Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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32227 Publications
Fano effect due to ponderomotive coupling in intersubband response of semiconductor quantum wells
Baudisch, M.; Wagner, M.; Schneider, H.; Stehr, D.; Helm, M.; Atkinson, P.; Huo, Y.; Schmidt, O. G.; Andrews, A. M.; Strasser, G.;
Using terahertz-time-domain spectroscopy, it has been demonstrated before that an intersubband transition in photoexcited undoped quantum wells reveals a Fano-like line shape in transmission spectra due to the phase-sensitive coupling of ponderomotive and intersubband currents [ D. Golde et al. Phys. Rev. Lett. 102 127403 (2009)]. In the present experimental study on GaAs/AlGaAs quantum wells we attempt to delineate the observability conditions of this phenomenon. We find that intensity-based Fourier-transform infrared (FTIR) spectroscopy cannot uncover these ponderomotive effects. However, for time-domain spectroscopy they are shown not to be limited to the case of optically excited electrons, but can be seen in doped samples as well.
Keywords: intersubband transition, terahertz, Fano, ponderomotive, quantum well, GaAs/AlGaAs

Publ.-Id: 17763 - Permalink


Terahertz nonlinear optics using intra-excitonic quantum well transitions: Sideband generation and AC Stark splitting
Wagner, M.; Schneider, H.; Stehr, D.; Winnerl, S.; Andrews, A. M.; Schartner, S.; Strasser, G.; Helm, M.;
We present experiments investigating nonlinear optics in the terahertz (THz) range related to the 1s–2p intra-excitonic heavy-hole transition in GaAs/AlGaAs multiquantum wells (MQWs). Driven by intense THz fields of the Dresden free-electron laser the system exhibits two different phenomena: (i) we observe efficient near-infrared (NIR) sideband generation as a perturbative effect in the transmission of a narrowband NIR laser, and (ii) we present unambiguous evidence for the intra-excitonic Autler–Townes splitting, a non-perturbative effect.
Keywords: AC Stark effect; Autler–Townes effect; excitons; sidebands; terahertz

Publ.-Id: 17762 - Permalink


Pt(II) and Pd(II) Pyrrolidine-Dithiocarbamates Investigated by XPS
Wenisch, R.; Montagner, D.; Helm, M.; Forrer, D.; Tondello, E.; Gross, S.;
In the present contribution, a series of four metal dithiocarbamates, namely 1-pyrrolidinecarbodithioate methyl ester (PyDTM) of Pd(II) and Pt(II), PtCl2(PyDTM), PtBr2(PyDTM), PdBr2(PyDTM), PdCl2(PyDTM), were analysed by x-ray Photoelectron Spectroscopy (XPS). Besides the wide scan spectra, detailed spectra for the C 1s, O 1s, N 1s, S 2s, S 2p, Pt 4f (for Pt-based compounds), Pd 3d (for Pd-based compounds), Cl 2p (for Cl containing compounds), Br 3p (for Br containing compounds) regions were acquired and the related data are presented and discussed.
Keywords: organic compounds, palladium compounds, X-ray photoelectron spectra, dithiocarbamates, coordination compounds, metal-sulphur bond, platinum, palladium, sulphur

Publ.-Id: 17761 - Permalink


Reconstruction of 4D in-beam PET data for quality control of moving target irradiation in ion beam therapy
Laube, K.; Fiedler, F.; Bert, C.; Saito, N.; Enghardt, W.;
no abstract available

Publ.-Id: 17760 - Permalink


GaAs photocathode status in Dresden-Rossendorf
Xiang, R.; Arnold, A.; Murcek, P.; Teichert, J.;
We introduce in this talk the developing status of GaAs photocathode for SRF gun. A new preparation chamber and transfer system has been designed. The test result of unactived bulk GaAs in SRF gun is reported here. Some experience for NEA-photocathode activation through GaN experiments is discussed.
Keywords: GaAs, photocathode, SRF gun
  • Invited lecture (Conferences)
    EuCARD SRF Annual Review, 29.-30.03.2012, Berlin, Germany

Publ.-Id: 17759 - Permalink


Curium(III) as intrinsic luminescence probe for direct speciation studies in biogeochemical systems
Moll, H.; Lütke, L.; Raff, J.; Brendler, V.; Bernhard, G.;
Knowledge concerning the speciation of actinides is essential to understand their fate and behavior in the environment. Moreover, the speciation of actinides influences their behavior in biological systems (e.g., microbes) in terms of chemical toxicity and radiotoxicity. Since many years we are successfully operating a unique pulsed flash lamp pumped Nd:YAG-­OPO laser system (Powerlite Precision II 9020 laser equipped with a Green PANTHER EX OPO from Continuum, Santa Clara, CA, USA) designed especially to detect the luminescence of trivalent actinides and lanthanides (e.g., Cm, Eu). The luminescence spectra were detected using an optical multi-channel analyzer-system, consisting of an Oriel MS 257 monochromator and spectrograph with a 300 or 1200 line mm-1 grating and an Andor iStar ICCD camera (Lot-Oriel Group, Darmstadt, Germany). The potential of this system for direct speciation studies of Curium(III) in biogeochemical systems will be presented on the basis of selected examples. These examples cover geochemical systems: the aqueous Cm(III) phosphate system [1] and biological systems: (a) Cm(III) speciation studies with cells of a groundwater strain of Pseudomonas fluorescens [2] and (b) Cm(III) complexation with bacterial surface-layer proteins [3].

Acknowledgement: This work was partly funded by BMWi under contract number 02E10618. The authors are indebted to the U.S. Department of Energy, Office of Basic Energy Sciences, for the use of 248Cm via the transplutonium element production facilities at Oak Ridge National Laboratory; 248Cm was made available as part of collaboration between HZDR and the Lawrence Berkeley National Laboratory (LBNL).


[1] Moll, H. et al. (2011) Radiochim. Acta 99, 775-782.
[2] Moll, H. et al. (2012) Geomicrobiol. J., in press.
[3] Moll, H. et al. (2011) Poster at the 13th International Conference on the Chemistry and Migration Behavior of Actinides and Fission Products (MIGRATION 2011), 18.-23.09.2011, Beijing, PR China.
Keywords: curium, TRLFS, speciation, biogeochemical systems
  • Contribution to proceedings
    International Workshop on Advanced Techniques in Actinide Spectroscopy (ATAS), 05.-07.11.2012, Dresden, Deutschland
  • Poster
    International Workshop on Advanced Techniques in Actinide Spectroscopy (ATAS), 05.-07.11.2012, Dresden, Deutschland

Publ.-Id: 17758 - Permalink


Cellular and molecular properties of 90Y-labeled cetuximab in combination with radiotherapy on human tumor cells in vitro
Saki, M.; Toulany, M.; Sihver, W.; Zenker, M.; Heldt, J.-M.; Mosch, B.; Pietzsch, H.-J.; Baumann, M.; Steinbach, J.; Rodemann, H. P.;
Purpose. Anti-EGFR antibody cetuximab (C225) is used in combination with radiotherapy of head and neck squamous cell carcinoma (HNSCC) patients. We investigated whether conjugation of cetuximab with trans-cyclohexyl-diethylene-triamine-pentaacetic acid (CHX-A″-DTPA) and radiolabeling with 90Yttrium affect the molecular and cellular function of cetuximab and improve its combined effect with external-beam irradiation (EBI).Methods. The following cell lines were used: HNSCC UT5, SAS, FaDu, as well as A43, Chinese hamster ovary cells (CHO), and human skin fibroblast HSF7. Binding affinity and kinetics, specificity, retention, and the combination of 90Y-cetuximab with EBI were evaluated.Results. Control cetuximab and CHX-A″-DTPA-cetuximab blocked the proliferation activity of UT5 cells. In combination with EBI, CHX-A″-DTPA-cetuximab increased the radiosensitivity of UT5 to a similar degree as control cetuximab did. In contrast, in SAS and HSF7 cells neither proliferation nor radiosensitivity was affected by either of the antibodies. Binding [90Y]Y-CHX-A″-DTPA-cetuximab (90Y-cetuximab) to EGFR in HNSCC cells occurred time dependently with a maximum binding at 24 h. Retention of 90Y-cetuximab was similar in both HNSCC cell lines; 24 h after treatment, approximately 90% of bound activity remained in the cell layer. Competition assays, using cell membranes in the absence of an internalized fraction of cetuximab, showed that the cetuximab affinity is not lost as a result of conjugation with CHX-A″-DTPA. Cetuximab and CHX-A″-DTPA-cetuximab blocked EGF-induced Y1068 phosphorylation of EGFR. The lack of an effect of cetuximab on EGF-induced Akt and ERK1/2 phosphorylation and the inhibition of irradiation (IR)-induced Akt and ERK1/2 phosphorylation by cetuximab were not affected by DTPA conjugation. 90Y-cetuximab in combination with EBI resulted in a pronounced inhibition of colony formation of HNSCC cells.Conclusions. Conjugation of CHX-A″-DTPA to cetuximab does not alter the cellular and biological function of cetuximab. 90Y-labeling of cetuximab in combination with EBI may improve radiotherapy outcome.
Keywords: Head and neck squamous cell carcinoma · EGFR · Cetuximab · 90Yittrium · 90Y-cetuximab

Publ.-Id: 17756 - Permalink


Prozess und Ergebnisse der Visions- und Zielbildung in einem komplexen Forschungsprojekt am Beispiel des ProSIN Projekts DER
Klossek, A.;
Die identifizierte Forschungslücke wird im vorliegenden Arbeitspapier aufgegriffen und konkret anhand des Fallbeispiels der Kooperationsplattform „Deutsches EnergieRohstoff-Zentrum Freiberg (DER)“ analysiert. Ziel des vorliegenden Arbeitspapieres ist es dementsprechend, den Entstehungs- und Gestaltungsprozess einer Vision, von Zielen und von Strategien in komplexen Forschungsprojekten strukturiert und fallstudienbasiert anhand des DER Projektes zu beschreiben. Aus der Fallstudienanalyse sollen ferner Gestaltungs- und Optimierungsansätze für zukünftige Kooperationsplattformen ähnlicher Art abgeleitet werden.
  • Open Access LogoContribution to external collection
    in: DER Working Papier Series Nr. 1/2012, Freiberg: Deutsches EnergieRohstoff-Zentrum, 2013

Publ.-Id: 17755 - Permalink


EtherCAT Feldbusknoten: Entwicklung, Systemunterstützung und -kompatibilität
Kaever, P.;
Die Verwendung selbst entwickelter Feldbusknoten und deren Einbindung in kommerzielle Automatisierungssysteme erfordert in der frühen Phase des Produktlebenszyklus einen erhöhten Entwicklungsaufwand. Nach erfolgreicher Integration bieten Hersteller von Automatisierungssystemen eine langfristig stabile und leistungsfähige Umgebung zur Projektierung und Programmierung von Anlagen, welche langfristig den Aufwand zur Pflege minimiert. Zur Überprüfung der Funktionsfähigkeit des Gesamtsystems ist die durch Testwerkzeuge unterstützte Systemkompatibilität eine entscheidende Voraussetzung. Die Vorgehensweise bei der Systemintegration eines Slave Device und der Prüfung der Systemkompatibilität wird im Folgenden vorgestellt.
Keywords: Fieldbus, slave devices, product life cycle, industrial Ethernet, EtherCAT, system integration, device test
  • Open Access LogoContribution to proceedings
    103. Tagung der Studiengruppe elektronische Instrumentierung im Frühjahr 2012, 12.-14.3.2012, Dresden, Deutschland
    103. Tagung der Studiengruppe elektronische Instrumentierung im Frühjahr 2012, ed.: Peter Göttlicher, 22607 Hamburg, Germany: Verlag Deutsches Elektronen-Synchrotron, 978-3-935702-65-2, 47-53
  • Lecture (Conference)
    103. Tagung der Studiengruppe elektronische Instrumentierung im Frühjahr 2012, 12.-14.3.2012, Dresden, Deutschland

Publ.-Id: 17754 - Permalink


Diffusive racetrack oxidation in a Ti sputter target by reactive high power impulse magnetron sputtering
Audronis, M.; Abrasonis, G.; Munnik, F.; Heller, R.; Chapon, P.; Bellido-Gonzalez, V.;
This paper reports experimental results for near-surface Ti sputter target oxidation in a magnetron racetrack during reactive high power impulse magnetron sputtering (HIPIMS) at various optical plasma monitoring set-points in the transition region between ‘metal’ and ‘poisoned’ target states. Oxygen depth profiles were obtained by nuclear reaction analysis and glow discharge optical emission spectroscopy. Ti target surface oxidation depth as induced by reactive HIPIMS was found to depend on the process set-point as well as discharge conditions. Deepest oxidation was observed when operating close to ‘fully poisoned (FP)’ or in ‘FP’ regime with oxygen profiles extending as deep as ∼0.5μm (oxygen concentration >=5 at%). Oxygen profiles obtained indicate the occurrence of oxygen bulk diffusion. Process induced elevated target surface temperature, magnetic field and plasma assistance are suggested to contribute substantially to these profiles. Based on these findings it is proposed that ion-bombardment-assisted thermal diffusion is a third target poisoning mechanism that can be taking place and is therefore important in reactive HIPIMS in addition to the two currently accepted mechanisms—ion implantation and chemisorption. Under the conditions investigated in this work, diffusive oxidation was most significant when operating in the lower part of the hysteresis loop. Reactive HIPIMS processes that will facilitate significant diffusive sputter target surface oxidation will also be expected to exhibit wider hysteresis and longer target cleaning times after substantial target poisoning.

Publ.-Id: 17753 - Permalink


Position-resolved Positron Annihilation Lifetime Spectroscopy
Wagner, A.; Butterling, M.; Fiedler, F.; Fritz, F.; Kempe, M.; Cowan, T. E.;
A new method which allows for position-resolved positron lifetime spectroscopy studies in extended volume samples is presented. In addition to the existing technique of in-situ production of positrons inside large (cm3) bulk samples using high-energy photons up to 16 MeV from bremsstrahlung production, granular position-sensitive photon detectors have been employed. A beam of intense bremsstrahlung is provided by the superconducting electron linear accelerator ELBE (Electron Linear Accelerator with high Brilliance and low Emittance) which delivers electron bunches of less than 10 ps temporal width and an adjustable bunch separation of multiples of 38 ns, average beam currents of 1 mA, and energies up to 40 MeV. Since the generation of bremsstrahlung and the transport to the sample preserves the sharp timing of the electron beam, positrons generated inside the entire sample volume by pair production feature a sharp start time stamp for positron annihilation lifetime studies with high timing resolutions and high signal to background ratios due to the coincident detection of two annihilation photons. Two commercially available detectors from a high-resolution medial positron-emission tomography system are being employed with 169 individual Lu2SiO5:Ce scintillation crystals, each. In first experiments, a positron-lifetime gated image of a planar Si/SiO2 (pieces of 1 cm × 2 cm size) sample and a 3-D structured metal in Teflon target could be obtained proving the feasibility of a three dimensional lifetime-gated tomographic system.
Keywords: position-resolved positron lifetime spectroscopy superconducting LINAC

Publ.-Id: 17752 - Permalink


Isospin observables from fragment energy spectra
Liu, T. X.; Lynch, W. G.; Tsang, M. B.; Hodges, R. K.; Liu, X. D.; Tan, W. P.; van Goethem, M. J.; Verde, G.; Wagner, A.; Xi, H. F.; Xu, H. S.; Famiano, M.; de Souza, R. T.; Charity, R. J.; Sobotka, L. G.; Showalter, R. H.;
The energy spectra of light charged particles and intermediate mass fragments from 112Sn+112Sn and 124Sn+124Sn collisions at an incident energy of E/A=50 MeV have been measured with a large array of Silicon strip detectors. We used charged particle multiplicities detected in a near-4 array to select data from the central collision events. We study isospin observables analogous to ratios of neutron and proton spectra, including double ratios and yield ratios of t/3He and of asymmetries constructed from fragments with Z=3-8. Using the energy spectra, we can construct these observables as functions of kinetic energy and observe a large difference in the fragment observables if fragments contributing to sequential decays are included.
Keywords: intermediate mass fragment nuclear multifragmentation silicon strip detector CsI detector light charged particle spectra

Publ.-Id: 17751 - Permalink


Visualisierung der Cyclooxygenase-2 mittels optischer Bildgebung in vitro und in vivo bei tumorassoziierten Prozessen
Tondera, C.;
kein Abstract verfügbar
  • Diploma thesis
    Friedrich-Schiller-Universität Jena, Biologisch-Pharmazeutische Fakultät, 2012
    100 Seiten

Publ.-Id: 17750 - Permalink


Photobiology: the biological impact of sunlight in carcinogenesis
Pietzsch, J.;
kein Abstract verfügbar
  • Invited lecture (Conferences)
    1st Klixx Solar Workshop on Photophysics, Photochemistry and Photobiology, 13.-14.07.2012, Madrid, Spain

Publ.-Id: 17749 - Permalink


Targeting cyclooxygenase-2 and oxidant stress pathways for attenuation of radiation-induced vascular dysfunction
Pietzsch, J.; Laube, M.; Ullm, S.; Sehn, F.; Pietzsch, F.-J.; Knieß, T.;
Radiotherapy of various cancers is closely associated with increased cardiovascular morbidity and mortality. Arachidonic acid metabolites are supposed to play a key role in radiation-induced vascular dysfunction.
This investigation was performed in order to evaluate the effects of novel selective cyclooxygenase-2 (Cox-2) inhibitors (coxibs) on radiation-induced formation of eicosanoids via Cox-2 and oxidant stress pathways in both human arterial endothelial cells (EC model) and rat aortic rings (AR model), respectively. In order to assess acute effects (24 h) of X-ray radiation at moderate doses (2, 4, and 10 Gy) without or with presence of coxibs (EC model: cyclopentene/indole/indomethacin derivatives; AR model: indole derivatives; celecoxib as reference) compared to sham-irradiated controls, the following parameters were measured: Cox-2 protein induction, release of prostaglandins, release of isoprostanes, and formation of lipid and protein oxidation products (LO/PO). Irradiation of EC and AR without presence of coxibs resulted in a dose-dependent augmentation of all parameters studied. When EC and AR were exposed to Cox-2 inhibitors (0.1, 1, and 10 µM), during and for 24 h post irradiation, indole derivatives showed highest potency to inhibit release of both prostaglandins and isoprostanes. Furthermore, indole derivatives significantly decreased LO/PO formation, indicating a direct interaction with oxidant stress-pathways. By contrast, both cyclopentene and indomethacin derivatives (and celecoxib) mainly inhibited prostaglandin release, but showed only slight effects on formation of isoprostanes and LO/PO. Model experiments using human low density lipoproteins showed that indole derivatives differently interact with oxidation of polyunsaturated fatty acids and protein amino acid side chains, than the cyclopentene/indomethacin derivatives, suggesting a physico-chemical rationale for observed antioxidative activity. The reduction of radiation-induced vascular dysfunction by antioxidative coxibs may widen the therapeutic window of Cox-2 targeted treatment.
  • Lecture (Conference)
    6th European Congress of Pharmacology (Ephar 2012), 17.-20.07.2012, Granada, Spain
  • Contribution to proceedings
    6th European Congress of Pharmacology (Ephar 2012), 17.-20.07.2012, Granada, Spain
    Proceedings of the 6th European Congress of Pharmacology, Bologna: Medimond, 978-88-7587-670-8, 87-90

Publ.-Id: 17748 - Permalink


18F-Labeled phosphopeptide-cell-penetrating peptide dimers with enhanced cell uptake properties in human cancer cells
Richter, S.; Bouvet, V.; Wuest, M.; Bergmann, R.; Steinbach, J.; Pietzsch, J.; Neundorf, I.; Wuest, F.;
Introduction
Phosphopeptides represent interesting compounds to study and elucidate cellular protein phosphorylation/dephosphorylation processes underlying various signal transduction pathways. However, studies of phosphopeptide action in cells are severely constrained by the negatively charged phosphate moiety of the phosphopeptide resulting in poor transport through the cell membrane. The following study describes the synthesis and radiopharmacological evaluation of two 18F-labeled phosphopeptide-cell-penetrating peptide dimers. The polo-like kinase-1-binding hexaphosphopeptide H-Met-Gln-Ser-pThr-Pro-Leu-OH was coupled to cell-penetrating peptides (CPPs), either sC18, a cathelicidin-derived peptide, or the human calcitonin derivative hCT(18-32)-k7.

Methods
Radiolabeling was accomplished with the prosthetic group N-succinimidyl 4-[18F]fluorobenzoate ([18F]SFB) using both, conventional and microfluidic-based bioconjugation of [18F]SFB to N-terminal end of phosphopeptide part of the peptide dimers. Cellular uptake studies in human cancer cell lines HT-29 and FaDu cells at 4 °C and 37 °C and small animal PET in BALB/c mice were utilized for radiopharmacological characterization.

Results
Isolated radiochemical yields ranged from 2% to 4% for conventional bioconjugation with [18F]SFB. Significantly improved isolated radiochemical yields of up to 26% were achieved using microfluidic technology. Cellular uptake studies of radiolabeled phosphopeptide and phosphopeptide-CPP dimers indicate enhanced internalization of 50% ID/mg protein after 2 h for both phosphopeptide dimers compared to the phosphopeptide alone (< 1% ID/mg protein). In vivo biodistribution of 18F-labeled peptide dimers was determined with small animal PET revealing a superior biodistribution pattern of sC18-containing peptide dimer MQSpTPL-sC18 [18F]4.

Conclusion
[18F]SFB labeling of the phosphopeptide-CPP dimers using a microfluidic system leads to an improved chemoselectivity towards the N-terminal NH2 group compared to the conventional labeling approach. Cell-penetrating peptide sC18 can be considered as an ideal molecular shuttle for intracellular delivery of the Plk1-PBD-binding hexaphosphopeptide as demonstrated by its favourable radiopharmacological profile.
Keywords: * 18F; * Phosphopeptides; * Cell-penetrating peptides (CPP); * Microfluidic; * Positron emission tomography (PET)

Publ.-Id: 17747 - Permalink


Experimente zur Entstehung von Titan-44 in Supernovae
Schmidt, K.;
In dieser Diplomarbeit wurde das astrophysikalisch interessante Resonanztriplett der Reaktion 40Ca(α,γ)44Ti bei 4,5MeV untersucht. Am 3-MV-Tandetron des Helmholtz-Zentrums Dresden-Rossendorf wurden dafür die Energien von Protonen- und -Strahlen kalibriert, Anregungsfunktionen im Energiebereich der drei Resonanzen aufgenommen, vier CaOTargets aktiviert und deren Struktur mittels der Reaktion 40Ca(p,γ)41Sc überprüft. Im Felsenkeller-Niederniveaumesslabor wurde anschließend die Aktivität der Proben gemessen. Schließlich konnte die Summe der Resonanzstärken bei 4497 und 4510 keV -Energie im Laborsystem zu (12;8 2;3) eV und die Summe der Resonanzstärken des gesamten Tripletts, d.h. zusätzlich bei 4523 keV, zu (12;0 2;0) eV bestimmt werden. Bei der ersten Resonanzstärke konnte die Unsicherheit im Vergleich zur Literatur von 19% auf 18% verbessert werden. Außerdem bieten die Daten der vorliegenden Arbeit die Grundlage, zukünftig die Unsicherheiten noch erheblich weiter zu reduzieren.


In this thesis the astrophysically interesting resonance triplet of the 40Ca(α,γ)44Ti reaction at 4.5MeV has been studied. For this purpose energies of proton and beams provided by 3MVTandetron at Helmholtz-Zentrum Dresden-Rossendorf have been calibrated. Excitation functions of energy regions near the resonances and in-beam spectra of four different targets have been measured. The 40Ca(p,γ)41Sc reaction has been used to scan the structure of the activated targets. Afterwards their activity has been measured in the underground laboratory Felsenkeller Dresden. Hence the sum of resonance strengths at laboratory energies of 4497 and 4510 keV of (12:8 2:3) eV has been determined as well as the sum of the total triplet strength, including 4523 keV, of (12:0 2:0) eV. In the case of the first resonance, the uncertainty was decreased from 19% to 18 %. Furthermore the results of this work establish a basis for reaching much lower uncertainties in the future.
Keywords: Ti-44, supernova, nuclear astrophysics, activation, 40Ca(alpha,gamma)44Ti, Tandetron, Felsenkeller
  • Open Access LogoWissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-020 2012

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Publ.-Id: 17746 - Permalink


The 14N(p,γ)O15 reaction studied at low and high beam energy
Marta, M.;
The Bethe-Weizsäcker cycle consists of a set of nuclear reactions that convert hydrogen into helium and release energy in the stars. It determines the luminosity of low-metal stars at their turn-off from the main-sequence in the Hertzsprung-Russel diagram, so its rate enters the calculation of the globular clusters’ age, an independent lower limit on the age of the universe. The cycle contributes less than 1% to our Sun’s luminosity, but it produces neutrinos that can in principle be measured on Earth in underground experiments and bring direct information of the physical conditions in the solar core, provided that the nuclear reaction rate is known with sufficient precision.
The 14N(p,γ)15O reaction is the slowest reaction of the Bethe-Weizs¨acker cycle and establishes its rate. Its cross section is the sum of the contributions by capture to different excited levels and to the ground state in 15O. Recent experiments studied the region of the resonance at Ep = 278 keV. Only one modern data set from an experiment performed in 1987 is available for the high-energy domain. Both energy ranges are needed to constrain the fit of the excitation function in the R-matrix framework and to obtain a reliable extrapolated S-factor at the very low astrophysical energies.
The present research work studied the 14N(p,γ)15O reaction in the LUNA (Laboratory for Underground Nuclear Astrophysics) underground facility at three proton energies 0.36, 0.38, 0.40MeV, and in Dresden in the energy range Ep = 0.6 - 2MeV. In both cases, an intense proton beam was sent on solid titanium nitride sputtered targets, and the prompt photons emitted from the reaction were detected with germanium detectors.
At LUNA, a composite germanium detector was used. This enabled a measurement with dramatically reduced summing corrections with respect to previous studies. The cross sections for capture to the ground state and to the excited states at 5181, 6172, and 6792 keV in 15O have been determined. An R-matrix fit was performed for capture to the ground state, that resolved the literature discrepancy of a factor two on the extrapolated S-factor. New precise branching ratios for the decay of the Ep = 278 keV resonance were measured.
In Dresden, the strength of the Ep = 1058 keV resonance was measured relative to the well-known resonance at Ep = 278 keV, after checking the angular distribution. Its uncertainty is now half of the error quoted in literature. The branching ratios were also measured, showing that their recommended values should be updated. Preliminary data for the two most intense transitions off resonance are provided.
The presence in the targets of the other stable nitrogen isotope 15N with its well- known isotopic abundance, allowed to measure the strength of two resonances at Ep = 430 and 897 keV of the 15N(p,αγ)12 C reaction, improving the precision for hydrogen depth profiling.
Keywords: Nuclear astrophysics; CNO cycle; TiN solid target; Tandetron; LUNA; Clover detector
  • Open Access LogoWissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-019 2012
    ISSN: 2191-8708

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Publ.-Id: 17745 - Permalink


Utilisation of a Hybrid Approach for Immersive Industrial Process Control Visualisation
Skripcak, T.; Tanuska, P.; Schmeißer, N.;
The objective of this paper is to present a proposal of hybrid system architecture for industrial process control visualisation. Leveraging of interoperability standard protocols for industrial automation, it is possible to create process agnostic visualisations. An application of this approach will lead to a hybrid system, which provides HMI (Human Machine Interface) layer for simulation, as well as real-world based industrial processes. An immersive 3-D visualisation is examined for the purpose of complex real-time process variables exploration. Reasonable 3-D visualisation types for industrial process HMI are identified. The idea is to create an immersive virtual environment for displaying industrial process related information, in order to help human operators to understand observed system behaviour and support them in the decision making process.
Keywords: SCADA/HMI, n-D visualisation, OPC, simulation.
  • Contribution to proceedings
    International Conference on Internet and Multimedia Technologies (ICIMT'12), 24.-26.10.2012, San Francisco, USA
    Proceedings of International Conference on Internet and Multimedia Technologies 2012., Hong Kong: International Association of Engineers, 978-988-19251-6-9, 415-420

Publ.-Id: 17743 - Permalink


Intra-excitonic coherent nonlinear optics in quantum wells: the Autler-Townes effect and beyond
Helm, M.;
Excitons in quantum wells represent a quasi-hydrogenic system, scaled down in energy to the meV (or THz) range due to the effective mass of the electrons and the dielectric constant. We take advantage of a free-electron laser as a narrow-band, intense THz source and drive the intra-excitonic heavy-hole 1s-2p transition in an undoped GaAs/AlGaAs multiquantum well (MQW). Probing the near-bandgap absorption with broad-band light from a 10 fs Ti: sapphire laser, we demonstrate the Autler-Townes splitting of the 1s exciton, giving evidence for dressed states. While the basic features at relatively low intensities follow the predictions of a simple two-level model, strong deviations are observed at higher THz fields in the 10 kV/cm range. At such field strengths, the rotating-wave approximation is not valid anymore, and also the two-level approximation breaks down, as higher excitonic bound states and the continuum cannot be neglected. Striking features are a peak reversal and overall blue shift of the Rabi sidebands with increasing field strength and a saturation of the splitting, going along with a line broadening that may indicate the onset of field ionization. Relevant for possible applications, signatures of this AC Stark effect are visible up to room temperature, with a THz induced threefold (at 200 K) near-infrared transmission modulation on a picosecond time scale. The above results are corroborated by recent measurements on an InGaAs/GaAs MQW with narrower exciton linewidth and corresponding calculations based on the semiconductor Bloch equations.
Keywords: terahertz, excitons, Autler-Townes, free-electron laser, semiconductor quantum well
  • Invited lecture (Conferences)
    31th International Conference on the Physics of Semiconductors (ICPS 2012), 29.07.-03.08.2012, Zürich, Schweiz

Publ.-Id: 17742 - Permalink


Perfect alloys for spin Hall current induced magnetization switching
Gradhand, M.; Fedorov, D. V.; Zahn, P.; Mertig, I.; Otani, Y.; Niimi, Y.; Vila, L.; Fert, A.;
We propose a device that allows for magnetization switching in nanomagnets by means of a pure spin current induced by the spin Hall effect. For this purpose we combine the ideas of magnetization switching of a ferromagnet by a spin current caused by the spin accumulation at a ferromagnet/nonmagnet interface with the electronic measurement of the direct spin Hall effect, and the theoretical material design to identify systems with a large spin Hall angle and an appropriate spin diffusion length. We will discuss the device design with respect to the size of the charge and spin currents. Based on ab initio calculations, we predict dilute alloys ideally suited for this application. Noble metals with single-sheeted Fermi surfaces doped with either heavy impurities like Bi and Pb in Cu or Bi in Ag and light impurities like C and N in Au seem to be the best candidates for a spin Hall angle larger than 5%.

Publ.-Id: 17741 - Permalink


Magnetoacoustic investigation of the Jahn-Teller effect in chromium doped ZnSe crystal
Gudkov, V. V.; Bersuker, I. B.; Yasin, S.; Zherlitsyn, S.; Zhevstovskikh, I. V.; Mayakin, V. Y.; Sarychev, M. N.; Suvoro, A. A.;
Ultrasonic investigation of ZnSe:Cr2+ crystal was carried out at low temperatures in magnetic field applied along the wave vector. The observed anomalies in magnetic field dependences of attenuation and wave number evidence for existence of resonant transitions between the energy levels of the Jahn-Teller tetrahedral complex CrSe4.

Publ.-Id: 17740 - Permalink


Direct imaging of spin wave emission from magnetic vortex cores
Wintz, S.; Weigand, M.; Stoll, H.; Schütz, G.; Raabe, J.; Quitmann, C.; Lindner, J.; Erbe, A.; Fassbender, J.ORC
Spin wave phenomena are an intensely studied field of magnetism, ranging from fundamental magnonics to the proposal of spin wave applications in logic or oscillator devices. In particular, the propagation of nanoscopic spin waves has come into the fore. Typically, micro-striplines or point- contacts are used to generate such spin waves in ferromagnetic media. However, a real-space observation of nanoscopic spin wave propagation has not been reported yet. Here we present the direct imaging of spin wave propagation as well as a novel concept for their generation based on the dynamics of interlayer coupled vortex pairs.
Keywords: magnetic vortex, spin wave emission, x-ray microscopy
  • Lecture (Conference)
    12th Joint MMM/Intermag Conference, 14.-18.01.2013, Chicago, USA

Publ.-Id: 17739 - Permalink


Transient Response of a Separated Flow over a Two-Dimensional Wing to a Short Duration Pulse
Williams, D.; Albrecht, T.; Weier, T.; Gerbeth, G.;
A Lorentz force actuator located at the leading edge of a two-dimensional wing at 16 degrees angle of attack was used to introduce short-duration disturbances into a separated flow. The transient response of the separated region at Re = 10,000 was documented using time-resolved PIV measurements. The direction of the Lorentz force was changed between downstream and upstream directed disturbances, and details of the resulting flow field structures and lift measurements were studied. Saturation of the peak lift amplitude occurs as the actuation amplitude is increased from 0.0054 < Cμ < 0.21 percent with the pulse duration fixed at 0.1 convective time. The effect of the pulse duration time on the lift response was examined using a fixed pulse amplitude, which showed that saturation occurred when pulse durations exceed 0.5 convective times. Differences in the coherent structures resulting from the upstream/downstream directed actuation were identified using the FTLE method. The initial development of the disturbed shear layer was strongly dependent on the direction of actuation, but the larger-scale separation did not show much difference. The relaxation of the separated region to the original flow state was essentially independent of the direction of actuation.
Keywords: flow control, Lorentz force, Finite-Time Lyapunov Exponent
  • Lecture (Conference)
    American Physical Society 65th Annual Fall Meeting, Division of Fluid Dynamics, 18.-20.11.2012, San Diego, USA

Publ.-Id: 17738 - Permalink


The Influence of Thermo-Solutal Convection on Freckle Formation and Dendritic Growth
Shevchenko, N.; Boden, S.; Gerbeth, G.; Eckert, S.;
In-situ observations of the solidification process under the influence of thermo-solutal convection were obtained by means of X-ray radioscopy within a Hele-Shaw cell filled with Ga-25wt%In alloy. The density-driven melt flow causes the formation of vertical freckles (“chimneys”) and changes the mushy zone characteristics. Experimental conditions have been identified which promote the formation of freckles in the Ga-In alloy. A strong coupling exists between the spatial and temporal properties of the flow field and the stability of segregation channels. Stable vortex flow provides a continuous upwards flow of solute-rich melt above the channel and an influx through the mushy zone towards the chimney. We also focused on the analysis of dendrite growth and microstructure features, for instance, dendrite orientation, primary and secondary arm spacing. The quantitative analysis of the flow field, temperature distribution and microstructure characteristic gives a better understanding of the complex interplay between melt flow and solidification process.
Keywords: X-ray radioscopy, thermo-solutal convection, chimneys, Ga - In alloy, mushy zone, melt flow, solidification, dendrite growth
  • Lecture (Conference)
    2013 TMS Annual Meeting & Exhibition / Frontiers in Solidification Science, 03.-07.03.2013, San Antonio, TX, USA

Publ.-Id: 17737 - Permalink


Microscopic Modelling of Freckle Formation during Directional Solidification and Its Verification via In situ X-ray Observation
Yuan, L.; Shevchenko, N.; Eckert, S.; Karagadde, S.; Lee, P. D.;
A 3D microscale solidification model, resolving complex interaction of solute partition and diffusion, interdendritic thermosolutal convection, dendrite formation and remelting, was used to study freckle formation for unidirectional solidified Ga-In alloys. The simulated results are validated against real time, in situ X-ray radiographic experiments, highlighting both similarities and differences between model and experiment. The redistribution of solute concentration and the formation of segregated solutal channels were both captured by the numerical model. Effects of thermo-solutal convection due to temperature and solute concentration variations were investigated and the formation of segregated solutal channels (freckles) was also examined in detail. With the assistance of the numerical solution, an improved understanding of the freckle channel formation at the microstructural level was provided.
Keywords: Freckle Formation , Directional Solidification, in situ X-ray radiographic experiments, 3D microscale solidification model, Thermosolutal convection, Computational model
  • Lecture (Conference)
    2013 TMS Annual Meeting & Exhibition/ Frontiers in Solidification Science, 03.-07.03.2013, San Antonio, TX, USA

Publ.-Id: 17736 - Permalink


Time dependent 2D flow structure measurements arising from melt stirring by means of various AC magnetic fields
Franke, S.; Räbiger, D.; Czarske, J.; Gerbeth, G.; Eckert, S.;
We present an experimental study concerning the flow inside an isothermal liquid metal column exposed to various magnetic field configurations. This paper is aimed at highly resolved, quantitative velocity measurements in the eutectic alloy GaInSn by means of the pulsed-wave ultrasound Doppler method. A novel ultrasound system was used to measure two-dimensional velocity fields of the secondary flow in the radial-meridional plane. The imaging system employs two arrays each of 25 transducer elements allowing for a fast electronic traversing with concurrently high spatial and temporal resolution. The study considers time-modulated fields or combinations of traveling magnetic fields (TMF) and rotating magnetic fields (RMF) revealing different flow structures and flow intensities. The results demonstrate different variants of electromagnetic melt stirring, some of them showing the potential to enhance the stirring efficiency and to optimize casting properties during solidification.
Keywords: Ultrasound Doppler method, flow field measurements, electromagnetic stirring, rotating magnetic field, magnetohydrodynamics, flow control
  • Lecture (Conference)
    8th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 19.-21.09.2012, Dresden, Deutschland
  • Open Access LogoContribution to proceedings
    8th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 19.-21.09.2012, Dresden, Deutschland
    Proceedings of the 8th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering

Publ.-Id: 17735 - Permalink


Tilting of carbon encapsulated metallic nanocolumns in carbon-nickel nanocomposite films by ion beam assisted deposition
Krause, M.; Mücklich, A.; Oates, T. W. H.; Zschornak, M.; Wintz, S.; Endrino, J. L.; Baehtz, C.; Shalimov, A.; Gemming, S.; Abrasonis, G.;
The influence of assisting low-energy (~50-100 eV) ion irradiation effects on the morphology of C:Ni (~15 at.%) nanocomposite films during ion beam assisted deposition (IBAD) is investigated. It is shown that IBAD promotes the columnar growth of carbon encapsulated metallic nanoparticles. The momentum transfer from assisting ions results in tilting of the columns in relation to the growing film surface. Complex secondary structures are obtained, in which a significant part of the columns grows under local epitaxy via the junction of sequentially deposited thin film fractions. The influence of such anisotropic film morphology on the optical properties is highlighted.
Keywords: Nanocomposites, Ion beam assisted deposition, TEM, GISAXS

Publ.-Id: 17734 - Permalink


Self-assembled isolated monodisperse NiO1+gamma nanoparticles as catalytic templates for nanomaterials synthesis
Houweling, Z.; Geus, J.; Harks, P.; Heller, R.; Schropp, R.;
We present the self-organization of isolated monodisperse nickel oxide (NiO1+gamma) nanoparticles on surfaces of arbitrary area sizes. Ni films deposited on titanium oxynitride support films are annealed in a nitrogen/air environment at atmospheric pressure for various annealing times. After the annealing treatments, randomly distributed spatially isolated NiO1+gamma, nanoparticles that are anchored to the support film are observed with a site-density of 11 +/- 1 mu m(-2) and with dimensions of 16 +/- 2 nm in height and 82 +/- 10 nm in diameter. The anchored nanoparticles, once formed, are immobile during further annealing, even for annealing times of 40 min or annealing temperatures of 800 degrees C, making the nanoparticle formation a well-controlled process that yields templates suitable for further processing at elevated temperatures. We demonstrate the utilization of these NiO1+gamma nanoparticle templates as nucleation sites for carbon nanotubes at temperatures of around 680 degrees C.

Publ.-Id: 17733 - Permalink


Nanoparticles in Organic Solvents with Polymers – Stability and Consequences upon Material Synthesis through Spray Drying and Melt Moulding
Rudolph, M.; Turan, C.; Kirchberg, S.; Ziegmann, G.; Peuker, U. A.;
It is a well accepted fact that nanoparticles and their industrial and commercial use have the potential to improve properties of modern materials substantially. Especially polymeric materials are attractive for incorporating nanoparticles with special properties only apparent in the nanoscale. One main consideration in processing such composite materials is to prevent the nanoparticles from agglomerating or even worse aggregating. In this paper a modular process method is presented based on a mixture of sterically stabilized nanoparticles in an organic solvent with soluble polymers and subsequent spray drying to quickly yet thermally carefully remove the solvent. The method has the potential for large scale production of highly filled nanoparticle-polymer-composites. However the bottleneck of this method is the unknown interaction of polymers and stabilized nanoparticles. We present the impact of depletion flocculation and subsequent phase separation or stabilization by adsorbing polymers on the dispersion of the nanoparticles. It is shown that the processing method is more adequate when compared to traditional melt moulding. The best magnetite nanoparticle stability in dichloromethane is achieved using ricinoleic acid. Besides flocculates we can identify separate primary particles in the composite. The size of the floccules is in the lower micrometer range for nanoparticles 15 nm in size.
  • Book chapter
    Tiddy, Gordon; Tan, Reginald: NanoFormulation, Cambridge: RSC Publishing, 2012, 978-1-84973-524-7, 177-187

Publ.-Id: 17732 - Permalink


High-temperature stability of c-Si surface passivation by thick PECVD Al2O3 with and without hydrogenated capping layers
Saint-Cast, P.; Kania, D.; Heller, R.; Kuehnhold, S.; Hofmann, M.; Rentsch, J.; Preu, R.;
We are studying the thermal stability of thick hydrogenated amorphous aluminum oxide (Al2O3) layers (20-50 nm) prepared by a high-throughput plasma-enhanced chemical-vapor-deposition (PECVD) technique for the electrical passivation of crystalline silicon surfaces. These passivation layers can be applied alone or covered by a capping layer like amorphous hydrogenated silicon nitride (SiNx) or amorphous hydrogenated silicon oxide (SiOx), also prepared by PECVD. After firing at 870 degrees C for approximately 3 s, the layers show blistering for Al2O3 of 30 nm or higher, independently from the capping layer. For thinner Al2O3, no blistering can be observed even using scanning electron microscope (SEM).
Very long carrier lifetimes up to 900 mu s was obtained in passivated p-Si (1 Omega cm) wafer after annealing and firing, without observing a strong influence of the layer thickness and the capping layer. All the layer stacks, including the stacks with SiNx capping layer, show high negative charge densities in the layer (1-4 x 10(12) cm(-2)). Additionally, low interface defect densities (similar to 10(11) cm(-2) eV(-1)), which could be achieved with and without a hydrogenated capping layer, were measured even after firing. To explain these phenomena, hydrogen concentration depth profiles were measured by nuclear reaction analysis. These measurements have shown that, at the Al2O3-Si interface, hydrogen atomic concentration ranging 5-7% after annealing and 4% after firing are obtained independently from the capping hydrogen concentration. We conclude that PECVD Al2O3 layers of 20 nm or thicker can provide enough hydrogen to passivate the interface defects, even after a high te!
mperature step. However, the layer thickness should be limited to 30 nm in order to avoid the blistering.

Publ.-Id: 17731 - Permalink


Nanocomposites based on technical polymers and sterically functionalized soft magnetic magnetite nanoparticles: Synthesis, processing, and characterization
Kirchberg, S.; Rudolph, M.; Ziegmann, G.; Peuker, U. A.;
This experimental study deals with the synthesis, processing, and characterization of highly filled nanocomposites based on polyvinyl butyral/magnetite (PVB/Fe3O4) and polymethylmethacrylate/magnetite (PMMA/Fe3O4). The nanoparticles are synthesized in an aqueous coprecipitation reaction and show a single particle diameter of approximately 15nm. The particles are sterically functionalized and covered by PVB and PMMA in a spray drying process. The synthesized compound particles are further processed by injection molding to test specimens with filler contents up to 14.5vol.-%. PVB and PMMA specimen are processed as a reference as well. The distribution of the nanoparticles is characterized by microscopy. Besides a minor number of agglomerates and aggregates the nanoparticles are distributed homogeneously in the PVB composites. Furthermore, the injection molded specimens are characterized with regard to their thermal degradation, polymer structure, and their mechanical and magnetic properties. The presence of nanoparticles capped with ricinoleic acid shows significant decrease in degradation temperature and in glass transition temperature of PVB. The degradation temperature of PMMA is increased by adding nanoparticles capped with oleic acid. Dynamic-mechanical properties as well as the magnetic permeability of PVB and PMMA are improved significantly by adding nanoparticles.
Keywords: Aqueous coprecipitation; Degradation temperatures; Dynamic mechanical property; Experimental studies; Filler contents; Functionalized; Injection-molded specimens; Polymer structure; Polyvinyl butyral; Ricinoleic acid; Single particle; Soft magnetics; Spray drying process; Test specimens

Publ.-Id: 17730 - Permalink


A TGA-FTIR perspective of fatty acid adsorbed on magnetite nanoparticles-Decomposition steps and magnetite reduction
Rudolph, M.; Erler, J.; Peuker, U. A.;
The fatty acid stabilization of magnetite nanoparticles is important for a broad field of studies and applications. In numerous previous studies TGA analyses are applied to investigate these compounds and draw conclusions such as magnetite concentration and surface grafting densities of the chemisorbed molecules. There are however deviations in interpretation of the analysis results. In the presented work we contribute to the discussion on the inert gas decomposition of the fatty acid ricinoleic acid adsorbed on the surface of magnetite nanoparticles with a priori knowledge of magnetite concentration. We report on impacts of autoxidation of the fatty acid as well as significant reduction of magnetite from carbonaceous residues. The findings are based on subsequent gas analysis with FTIR coupled to the TG device. We show how stoichiometric calculations on the reduction in the temperature range of 600-900°C let conclude that the residues are most probably from the chemisorbed fatty acid molecules. Only the physically adsorbed fatty acid molecules have decomposed or detached before 600°C. In context to the investigations on chemically adsorbed fatty acid on magnetite we compare the decomposition of pristine fatty acid and fatty acid physically adsorbed on a high surface area SiO 2 nanopowder. Three distinct steps of decomposition which have often been reported before are found and accounted.
Keywords: Decomposition, FTIR, Magnetite, Nanoparticles, Reduction, Ricinoleic acid, TGA

Publ.-Id: 17729 - Permalink


Ultrasonic flow measurements and bubble detection in gas-stirred metallic melts
Vogt, T.; Andruszkiewicz, A.; Eckert, K.; Odenbach, S.; Eckert, S.; Gerbeth, G.;
In this study we investigate the flow structure in a liquid metal cylinder while a bubble driven recirculation flow is superposed with a rotating magnetic field (RMF). The flow structure and the bubble detection were measured by means of the ultrasound Doppler velocimetry (UDV) and ultrasound transit-time technique (UTTT). The measurements revealed the potential of the RMF to control both the amplitude of the meridional flow and the bubble distribution and to provide an effective mixing in the whole fluid volume. Various periodic flow patterns were observed in a certain parameter range with respect to variations of the magnetic field strength and the gas flow rate.
Keywords: bubble detection, bubble flow, rotating magnetic field, udv
  • Open Access LogoContribution to proceedings
    8th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 19.-21.09.2012, Dresden, Deutschland
    Proceedings of ISUD8
  • Lecture (Conference)
    8th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 19.-21.09.2012, Dresden, Deutschland

Publ.-Id: 17728 - Permalink


Magnetization dynamics of Co antidot lattices
Neudert, A.; Bali, R.; Kostylev, M.; Adeyeye, A.; Römer, F. M.; Wagner, K.; Farle, M.; Lenz, K.; Lindner, J.; Fassbender, J.ORC
We have systematically investigated the static and dynamic magnetic properties of Co(t nm)/CoO(5 nm)/Cu(2 nm) antidot square lattices as a function of Co thickness [1]. The Co film thicknesses in the different samples are 25, 50, 75, and 100 nm, respectively. The antidot pattern forms a square lattice with a wavelength of 415 nm (center to center) and the hole diameters were varied in the different samples (145, 185, 225, and 265 nm, respectively).
The static magnetic properties were measured using in-plane magneto-optical Kerr effect (MOKE) magnetometry. Measuring magnetization loops at different in-plane angles we could determine the orientation dependence of coercive (Hc) and saturation (Hs) fields. Both fields show angular dependencies that form a 4-fold anisotropy with hard axes along the [10] directions. Those anisotropies in Hc and Hs can be explained by the geometry of the lattice by taking into account the hole diameter.
Dynamic measurements were done using time-resolved MOKE experiments and different ferromagnetic resonance (FMR) setups (Vector Network Analyzer (VNA)-based and classical detection using a shortened microwave cable). For the 50 nm thick sample with holes of 145 nm diameter a transition of the main mode from a lower frequency branch to a higher one was observed at a field of around 900 Oe and a frequency of around 6 GHz along the [10] direction. A similar transition between main modes is also visible for larger hole diameters as well as for larger film thicknesses. Due to the coexistence of 2 modes at a fixed frequency it is not a real frequency gap but on the other hand the two branches are also not connected, rather the main precessional magnitude transitions from the lower branch to the higher branch.
Angular FMR scans show a strong signal for a 4-fold anisotropy with the hard axes along the [10] directions and a weak signal for additional hard axes along the [11] directions, confirming the findings of the static angular loop measurements done with MOKE magnetometry.
Keywords: magnetization dynamics, antidot lattice, FMR
  • Poster
    2012 IEEE International Conference on Microwave Magnetics (ICMM 2012), 26.-29.08.2012, Kaiserslautern, Deutschland

Publ.-Id: 17727 - Permalink


Imaging of the brain serotonin transporters (SERT) with a new fluorine-18 labelled fluoromethyl-analogue of McN5652 and PET in humans
Hesse, S.; Brust, P.; Mäding, P.; Becker, G.-A.; Patt, M.; Seese, A.; Sorger, D.; Luthardt, J.; Steinbach, J.; Sabri, O.;
Abstract wird nachgereicht.
  • Poster
    The 9th International Symposium on Functional Neuroreceptor Mapping of the Living Brain (NRM2012), 09.-11.08.2012, Baltimore, USA
  • Abstract in refereed journal
    Journal of Cerebral Blood Flow and Metabolism 32(2012), 100-127
    DOI: 10.1038/jcbfm.2012.79

Publ.-Id: 17726 - Permalink


Thermophysical properties of the liquid Pb84.1-Au15.9 eutectic alloy
Plevachuk, Y.; Sklyarchuk, V.; Yakymovych, A.; Eckert, S.; Gerbeth, G.;
Lead-gold eutectic alloy is under intense consideration as target material of spallation sources. The thermohydraulic design of such a target or related coolant systems requires a reliable data basis regarding the temperature dependent physical properties of such alloys. We present measurements of the electrical and thermal conductivity, thermoelectric power, viscosity and surface tension for liquid Pb-Au alloys of eutectic composition in a wide temperature range between the melting point and about 1000 K.
Keywords: thermophysical properties, lead-gold eutectics

Publ.-Id: 17725 - Permalink


PET Imaging of Cerebral Nicotinic Acetylcholine Receptors (nAChRs) in Early Alzheimer’s Disease (AD) Assessed with the New Radioligand (–)-[18F]Norchloro-Fluoro-Homoepibatidine ((–)-[18F]Flubatine)
Sabri, O.; Wilke, S.; Graef, S.; Becker, G.; Hesse, S.; Sattler, B.; Schönknecht, P.; Wagenknecht, G.; Smits, R.; Hoepping, A.; Steinbach, J.; Brust, P.;
Abstract wird nachgereicht.
  • Poster
    The 9th International Symposium on Functional Neuroreceptor Mapping of the Living Brain (NRM2012), 09.-11.08.2012, Baltimore, USA
  • Abstract in refereed journal
    Journal of Cerebral Blood Flow and Metabolism 32(2012), 55-55
    DOI: 10.1038/jcbfm.2012.78

Publ.-Id: 17724 - Permalink


In the search for a dream job - discovering your own potential.
Werniewicz, K.;
Getting a job in today’s extremely competitive world is not a trivial task. Getting a job which in parallel meets your interest, field of expertise and overall skills as well as satisfying your ambitions and financial expectations, is a real challenge.
Luckily most of us do enjoy the challenging tasks and if we are armed with an excellent education, curiosity for life, and desire for further self-development, the challenges tend to motivate rather than hinder us in advancing our goals. A final measure of your success will be your own satisfaction.
The following workshop attempts to demonstrate the opportunities and tools available to young academics for their career development. These include:
• Career path selection – making the most of your potential
• Mobility – building an international career
• Do I have the skill set and expertise people are looking for? – expanding your professional and interpersonal skills via diverse trainings
• Job adverts - getting lucky in your job search
• Shaping the future – preparing a career strategy, and finally
• How to turn an initial failure into an ultimate success
These aspects will all be discussed and illustrated by examining my own experiences.
The most important message to be delivered by this workshop is that in chasing your dreams for a perfect job you must not fear changes. Only through exploring new areas, listing to your own needs and constructively responding to them, will you be able to find a position that suits you.
Remember, you always have a choice!
  • Invited lecture (Conferences)
    The BioTiNet Summer School "Titanium in Medicine", 04.-08.06.2012, Caldes d’Estrac, Barcelona, Spain

Publ.-Id: 17723 - Permalink


Verification and validation of numerical models of the transport of insulation debris
Cartland Glover, G. M.; Kratzsch, A.; Krepper, E.; Renger, S.; Seeliger, A.; Zacharias, F.; Alt, S.; Kästner, W.; Kryk, H.; Weiss, F.-P.;
Damage to insulation materials located near to a primary circuit coolant leak may compromise the operation of the emergency core cooling system (ECCS). Insulation material in the form of mineral wool fiber agglomerates (MWFA) maybe transported to the containment sump strainers, where they may block or penetrate the strainers. Though the impact of MWFA on the pressure drop across the strainers is minimal, corrosion products formed over time may also accumulate in the fiber cakes on the strainers, which can lead to a significant increase in the strainer pressure drop and result in cavitation in the ECCS.
An experimental and theoretical study performed by the Helmholtz-Zentrum Dresden-Rossendorf and the Hochschule Zittau/Görlitz is investigating the phenomena that maybe observed in the containment vessel during a primary circuit coolant leak. The study entails the generation of fiber agglomerates, the determination of their transport properties in single and multi-effect experiments and the long-term effect that corrosion and erosion of the containment internals by the coolant has on the strainer pressure drop.
The focus of this paper is on the verification and validation of numerical models that can predict the transport of MWFA. A number of pseudo-continuous dispersed phases of spherical wetted agglomerates represent the MWFA. The size, density, the relative viscosity of the fluid-fiber agglomerate mixture and the turbulent dispersion all affect how the fiber agglomerates are transported. In the cases described here, the size is kept constant while the density is modified. This definition affects both the terminal velocity and volume fraction of the dispersed phases. Note that the relative viscosity is only significant at high concentrations.
Three single effect experiments were used to provide validation data on the transport of the fiber agglomerates under conditions of sedimentation in quiescent fluid, sedimentation in a horizontal flow and suspension in a horizontal flow. The experiments were performed in a rectangular column for the quiescent fluid and a racetrack type channel that provided a near uniform horizontal flow. The numerical models of sedimentation in the column and the racetrack channel found that the sedimentation characteristics are consistent with the experiments. For channel suspension, the heavier fibers tend to accumulate at the channel base even at high velocities, while lighter phases are more likely to be transported around the channel.
Keywords: Mineral Wool Fiber Agglomerates, Loss of Coolant Accidents, Containment Sump, Computational Fluid Dynamics, Multiphase Flow

Publ.-Id: 17722 - Permalink


Core-Core Interaction in Spin-Torque Double-Vortex Oscillators
Sluka, V.; Kákay, A.; Deac, A. M.; Bürgler, D. E.; Hertel, R.; Schneider, C. M.;
Magnetic vortex states are determined by two binary parameters: The vorticity refers to the sense of rotation of the curling in-plane magnetization; the polarity determines the up or down orientation of the out-of-plane magnetized vortex core [1]. Due to their unique nano-scale properties, magnetic vortices may be used in a wide range of applications. However, to exploit their full potential, ways must be sought to measure the core polarity. Due to the smallness of the vortex core, this has so far been a difficult task requiring elaborate imaging techniques [2-4].
Here we present a combined experimental and numerical study on double vortex oscillators. Our samples are all-metallic nanopillars 150 nm in diameter that contain a Fe(30)/Ag(6)/Fe(15) pseudo spin valve. The geometry of the Fe disks is chosen as to stabilize configurations with two stacked vortices. By applying d.c. cpp-currents, we excite magnetization dynamics corresponding to gyrotropic vortex motion. We show that the coupled dynamics of the two vortices split into a fine structure of modes. As confirmed by micromagnetic simulations, the different frequencies correspond to different vorticity-polarity combinations of the double vortex system. In particular, changes in relative core polarity between the two vortices lead to frequency differences of the order of 100 MHz. Our results therefore suggest a way to measure vortex core polarities by electrical means.
[1] E. Feldtkeller, and H. Thomas, Phys. kondens. Mat. 4 (1965) 8.
[2] T. Shinjo et al., Science 289 (2000) 930.
[3] A. Wachowiak et al., Science 298 (2002) 577.
[4] A. Vansteenkiste et al., Nature Phys. 5 (2009) 332.
  • Poster
    21th International Colloquium on Magnetic Films and Surfaces (ICMFS2012), 24.-28.09.2012, Shanghai, China

Publ.-Id: 17721 - Permalink


Spin-Transfer Torque-Induced Dynamics of CoFe/Pd Superlattice-Based Nano-Oscillators in Perpendicular Magnetic Field
Sluka, V.; Fowley, C.; Bernert, K.; Deac, A. M.; Rippard, W. H.; Pufall, M. R.; Russek, S. E.;
Spin-transfer torque provides a mechanism that can be employed to control magnetization on the nano-scale [1,2]. This scheme is used in spin-torque nano-oscillators (STNOs) where it is used to excite steady state precession of the magnetization, leading to microwave emission. Typical STNOs are nanopillars comprising two in-plane magnetized layers [3], one of which has a fixed magnetization while the other one is susceptible to spin-transfer torque. In such configurations, spin-torque generally leads to small angle or clam shell precession of the free layer around an in-plane easy axis of magnetization.
In this work, we investigate a different type of oscillator: The device consists of an in-plane magnetized CoFe layer and an out-of-plane magnetized [CoFe/Pd] superlattice. While the in-plane magnetized layer is confined to about 70 nm, the perpendicular layer is extended. In contrast to common STNOs, our structure is designed as to enable spin-torque-induced excitation in each of the layers. In the experiment, the spin-torque-excited magnetization dynamics is investigated with respect to the sample current and the applied out-of-plane magnetic field. For both current polarities, dynamic states are observed. Considering both layers separately, the in-plane magnetized layer contributes to the dynamics in either case of the current sign, however, the spin-torque asymmetry [4] allows excitation of the perpendicular layer only for one polarity. Since the observable signal is due to the relative motion of the layers’ magnetizations, the output frequency is significantly reduced compared to the frequency of each individually precessing layer. The concept of using the frequency difference between two dynamic layers coupled by spin-torque might be particularly useful for customizing STNOs for microwave generation.

1) J. C. Slonczewski, J. Magn. Magn. Mater. 159, (1996) L1.
2) L. Berger, Phys. Rev. B 54, (1996) 9353.
3) S. I. Kiselev et al., Nature 425, (2003) 380.
4) J. C. Slonczewski, J. Magn. Magn. Mater. 247, (2002) 324.
  • Poster
    21th International Colloquium on Magnetic Films and Surfaces (ICMFS2012), 24.-28.09.2012, Shanghai, China

Publ.-Id: 17720 - Permalink


Switching voltages and back-hopping in magnetic tunnel junctions with different geometries
Bernert, K.; Sluka, V.; Fowley, C.; Gan, H.; Fassbender, J.ORC; Deac, A. M.
A spin-polarized current flowing through a ferromagnet can exert a torque on the local magnetization [1,2], which induce switching or steady state precession. Spin-transfer switching can be used as writing scheme in magnetic random access memory (MRAM), while spin-torque-driven precession can be exploited to design RF oscillators for telecommunication devices. Presently, the majority of spin-torque devices are based on a magnetic tunnel junction (MTJ) with an MgO barrier. A key step towards the practical implementation as MRAM elements is the reduction of the critical voltages [3].
Several groups have reported that MTJs exhibit the so-called ‘back-hopping’, whereby reliable switching is achieved with voltages of the order of the switching voltage, while a larger applied bias induces a telegraph-noise behaviour [4,5]. Back-hopping is characteristic for MTJs, since it has not been observed in metallic multilayers, and raises concerns for designing industrially-competitive MRAM devices. Here, we demonstrate that a potential cause for this phenomenon is the field-like (out-of-plane) spin-torque, which has been found to be much larger in MgO-MTJs than in metallic spin-valves, where it can be neglected [6]. In MgO-MTJs, however, the field-like torque can be of the order of 30% of the in-plane torque [7], and needs to be taken into account. We evaluate the switching phase diagram by analytically and numerically solving the modified Landau-Lifshitz-Gilbert equation which includes both (in-plane) (Slonczewski-like) and field-like torque terms for different geometries. The quadratic dependence of the field-like torque on the applied voltage [8] translates into a more complex correlation between the critical bias and the external field, altering the shape of the phase diagram as demonstrated experimentally [9]. It also explains back-hopping at a large bias for specific geometries, in agreement with experimental results.

[1] J. C. Slonczewski, J. Magn. Magn. Mater. 159 (1996) L1.
[2] L. Berger, Phys. Rev. B 54 (1996) 9353.
[3] Z. Diao et al., J. Phys.: Cond. Mat. 19 (2007) 165209.
[4] J. Z. Sun et al., J. Appl. Phys. 105 (2009) 07D109.
[5] T. Min et al., J. Appl. Phys. 105 (2009) 07D126.
[6] M. A. Zimmler et al., Phys. Rev. B 70, 184438 (2004).
[7] J. C. Sankey et al., Nat. Phys. 4, 67 (2008).
[8] C. Heiliger and M. Stiles, Phys. Rev. Lett. 100 (2008) 186805.
[9] S.-C. Oh et al., Nat. Phys. 5, 898 (2009).
Keywords: Spin-Torque Oscillators, Spin-Transfer Switching, Magnetic Random Access Memory
  • Lecture (Conference)
    2012 IEEE International Conference on Microwave Magnetics (ICMM 2012), 26.-29.08.2012, Kaiserslautern, Germany
  • Poster
    International Colloquium on Magnetic Films and Surfaces (ICMFS), 24.-28.09.2012, Shanghai, China

Publ.-Id: 17719 - Permalink


Microwave dynamics in point contact spin valve structures combining in-plane and out-of-plane magnetic layers with in-plane magnetic fields
Fowley, C.; Sluka, V.; Bernert, K.; Gan, H. D.; Deac, A. M.; Rippard, W. H.; Pufall, M. R.; Russek, S. E.;
Point contact spin transfer devices combining perpendicularly and in-plane magnetized layers are good candidates to fulfill the requirements of high power, low line-width and close to zero applied field operation [1][2]. We present experimental results on spin transfer torque oscillators combining an extended out-of-plane (CoFe/Pd) magnetized layer and a lithographically patterned in-plane (CoFe) magnetized layer.
High frequency magnetization dynamics as a function of current in such devices are explored for in-plane applied magnetic field. In general, the recorded oscillation frequency is lower than that which would be expected for dynamics associated with a single layer in the device (calculated for the given Ha and Ms of each layer). The individual dynamics of each layer are calculated, individually, from numerical integration of the LLG equation taking into account the Slonczewski spin transfer torque including the spin transfer asymmetry characterized by λ [3]. Microwave oscillations are observed at zero applied magnetic field. However, due to canting of the perpendicular layer in the in-plane applied magnetic field, the current dependent frequency of the system changes slope when the relative magnetization orientations are changed from perpendicular to parallel.
A.M.D. and C.F. acknowledge financial support from the Swiss National Foundation Ambizione grant (PZ00P2_131808).
[1] Houssameddine, D. et al., Nature Mat. 6, 447 (2007).
[2] Rippard, W.H., et al., Phys. Rev. B. 81, 014426 (2010).
[3] Slonczewski, J.C., J. Magn. Magn. Mater. 247, 324 (2002).
Keywords: Spin transfer torque, spin transfer oscillators, numerical integration
  • Poster
    21th International Colloquium on Magnetic Films and Surfaces (ICMFS), 24.-28.09.2012, Shanghai, China

Publ.-Id: 17718 - Permalink


Investigation of dipole strength in (gamma, gamma) and (n,gamma) experiments
Massarczyk, R.; Schwengner, R.; Junghans, A.; Schramm, G.; Grosse, E.;
The talk is an overview of our dipole strength experiments and analysis in Dresden and Budapest. It was presented to the IRMM nuclear physics group as foundation for our collaboration in the future 77Se (n,gamma) experiment.
Keywords: photon strength function, neutron capture, statistical analysis
  • Lecture (others)
    Seminar, 14.03.2012, Geel, Belgium

Publ.-Id: 17717 - Permalink


Quick-look report of the ROCOM Tests 1.3, 2.1 and 2.2 conducted within the OECD PKL2 Project
Kliem, S.; Franz, R.;
In the frame of the OECD PKL 2 Project the Test G3.1 was conducted at the PKL test facility. This test was dedicated to the investigation of a fast cool down transient. The transient was initiated by a main steam line break. One of the objectives of this test was to create experimental data for the the qualification of thermal hydraulic codes against Pressurized Thermal Shock (PTS) and re-criticality aspects. To investigate in more detail the thermal hydraulic behavior inside the reactor pressure vessel (RPV) complementary tests on the coolant mixing were conducted at the ROCOM (Rossendorf Coolant Mixing) test facility. Experimental results at the RPV inlet derived from the Test G3.1 were used as boundary conditions for the ROCOM tests. In the ROCOM Test 1.3 a specific aspect of the behavior of an ECC water stripe was investigated. The goal of the Tests 2.1 and 2.2 was the re-criticality issue, more specific, the investigation of the possibility of the formation of a sector with overcooled water at the core inlet.
  • Article, self-published (no contribution to HZDR-Annual report)
    Helmholtz-Zentrum Rossendorf 2012
    HZDR\FWO\2012\02
    0038 Seiten

Publ.-Id: 17716 - Permalink


Parametric resonance in a periodically perturbed von-Karman flow
Giesecke, A.; Stefani, F.;
We have performed numerical simulations of the kinematic induction equation in order to examine the dynamo efficiency of an axisymmetric von-Karman-like flow suct to time-dependent non-axisymmetric velocity perturbations. The numerical model is based on the setup of the French Von-Karman-Sodiuynamo and the flow measurements from a model water experiment conducted at the University of Navarra in Pamplona,ain. We find two distinct regimes of dynamo action that depend on the azimuthal drift of an (m=2) vortex like floerturbation. For comparatively slowly drifting vortices we observe a narrow window with enhanced growth-rates anddrift of the magnetic eigenmode that is synchronized with the flow perturbation drift. For larger vortex drift an abrupt transition to independently drifting magnetic eigenmode occurs and the field amplitude is modulated with twice the vortex driftequency. The sudden change between the resonant regime and the modulated regime is identified as an spectral exceonal point where eigenvalues and eigenfunctions of two previously independent modes collapse.
Keywords: Dynamo Simulation
  • Lecture (Conference)
    European GDR Dynamo & MHD Days, 01.-04.10.2012, Nice, France

Publ.-Id: 17715 - Permalink


Research on the reactor physics and reactor safety of VVER reactors – Selected contributions to the XXIst Symposium of the Atomic Energy Research organization
Aszodi, A.; Kliem, S.;
The Atomic Energy Research (AER) is an organization of 22 institutions (utilities, re-search institutes and universities) from nine countries. The common interest within this organ-ization is the research on topics related to all aspects of the operation of VVER reactors. AER provides the only regular scientific-technical co-operation for the VVER user countries. The organization is also open to institutions from countries not operating VVER reactors. . In 2011, the XXIst Symposium was organized in Dresden, Germany, from September 19 till 23. It was hosted by the Institute of Safety Research of the Helmholtz-Zentrum Dresden-Rossendorf. Altogether 61 papers were presented during this Symposium. The organizing committee selected 15 papers from the Symposium for this special issue of Kerntechnik, representing the whole spectrum of the activities of the AER.
  • Kerntechnik 77(2012)4, 212-212

Publ.-Id: 17714 - Permalink


Sound velocity measurements in fluids using echo signals from scattering particles
Lenz, M.; Bock, M.; Kühnicke, E.; Pal, J.; Cramer, A.;
A novel approach for measuring the speed of sound in fluids with scattering particles is presented. Potential fields of application for sound velocity measurements in fluids are process control, environmental measurement technology and medicine, where sound velocity can be used as an indicator of temperature, concentration or mass density. Similar to the pulsed Doppler application, the method also works non-invasively and uses the echo signals from scattering particles suspended in the fluid. The basic idea is that the ultrasonic time of flight to the focus position z depends on the speed of sound c in a well-defined way. The time of flight to the focus can be extracted from the echo signals, because the stray echo is strongest for the scattering particles being located in the sound focus and can thus be used to determine the speed of sound. Results are shown for different homogeneous fluids with sound velocities between 1116 m/s (ethanol, 50 °C) and 2740 m/s (eutectic GaInSn). Measurements have shown that a statistical measurement uncertainty of about 0,1 % was achieved with the underlying set-up. Further results of recent measurements in water having a temperature gradient show that the method is even capable of measuring the sound velocity with local resolution.
Keywords: speed of sound, material characterisation, scattering particles, annular array
  • Contribution to proceedings
    8th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering ISUD8, 19.-21.09.2012, Dresden, Deutschland
    Sound velocity measurements in fluids using echo signals from scattering particles
  • Lecture (Conference)
    8th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering ISUD8, 19.-21.09.2012, Dresden, Deutschland

Publ.-Id: 17713 - Permalink


Mikro- und (Ultra)spurenelementanalyse - ein wichtiges Werkzeug für die Suche und Erkundung von Erzlagerstätten
Renno, A. D.;
Auf den ersten Blick ein Widerspruch – ist die Analyse von Spurenelementen in sehr kleinen Dimensionen bei der Suche nach Erzlagerstätten von entscheidender Bedeutung. Ohne solchen Analysen können wir die Lagerstätten nicht ressourcenschonend und nachhaltig nutzen.
Keywords: Ressourcenanalytik, Ultraspurenelement, Mikroanalyse
  • Lecture (others)
    Dresdner Lange Nacht der Wissenschaften, 06.07.2012, Dresden, Deutschland

Publ.-Id: 17712 - Permalink


Flow measurements in a model of the Czochralski crystal growth process
Pal, J.; Cramer, A.; Gerberth, G.;
An experimental study of the buoyancy-induced flow in a model of a Czochralski crystal growth system was conducted. Ultrasonic velocimetry was used to measure fluid velocities. To have similar thermal boundary conditions as in an industrial growth facility, a double walled glass crucible flown through by a heating fluid was chosen to hold the fluid. Similarity of the heat transfer conditions was achieved by selecting a liquid metal as the fluid under investigation, which was the ternary alloy GaInSn having a Prandtl number of 0.021. Because of the double-walled crucible, measurements through the container wall are difficult if ever possible. Since the availability of relatively short ultrasonic transducers it is practicable to have the sensor immersed into the fluid. Measurements of the radial velocity component shortly below the melt surface across the entire diameter of the crucible at various azimuthal angles reveal the complex flow structure of natural convection in a Czochralski crucible. As it is not to be expected to grow high quality mono-crystalline crystals from such a non-axisymmetric flow, rotating magnetic fields (RMF) are often proposed to render the flow more axisymmetric. This paper also addresses the question what happens to the buoyancy-driven flow when such an RMF is applied.
Keywords: Czochralski crystal growth,Rayleight-Benard convection,ultrasonic flow measurement,magnetohydrodynamics, electromagnetic stirring
  • Contribution to proceedings
    8th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering ISUD8, 19.-21.09.2012, Dresden, Deutschland
    Flow measurements in a model of the Czochralski crystal growth process
  • Lecture (Conference)
    8th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering ISUD8, 19.-21.09.2012, Dresden, Deutschland

Publ.-Id: 17711 - Permalink


Investigation of dual-beam-implanted oxide-dispersed-strengthened FeCrAl alloy by positron annihilation spectroscopy
Kögler, R.; Anwand, W.; Richter, A.; Butterling, M.; Mücklich, A.; Ou, X.; Reuther, H.; Chen, C.-L.; Wagner, A.;
Oxide-dispersion-strengthened (ODS) FeCrAl steel is a class with promising materials to be applied for future nuclear applications. However, radiation damage, especially the formation of vacancy clusters or gas-filled bubbles, may result in hardness increase and the loss of ductility. Positron annihilation spectroscopy (PAS) is demonstrated to be a very useful and non-destructive analysis method to detect and to determine open volume defects of sub-nm size in ODS alloy. Synchronized dual beam implantation of Fe and He ions is performed to simulate the radiation damage caused by (n, α) reactions and to avoid induced activation. For room temperature implantation, i.e. without significant point defect recombination, the differences in the defect formation are shown by comparison between irradiation of ODS alloy and pure Fe bulk. The open volume defects created in ODS alloy are vacancy clusters closely connected with dispersed Y oxide nanoparticles. Their profiles are in reasonable qualitative agreement with the hardness profiles, indicating a relationship between sub-nm vacancy clusters or He bubbles and the hardness of the material. In heat-treated ODS alloy, containing larger vacancy clusters, the radiation induced hardness increase is more distinctive than for as-received ODS alloy.
For irradiation at a moderately enhanced temperature of 300°C open volume defects are drastically reduced. The few remaining defects are vacancy clusters of the same type as in as-received ODS alloy. Close to the surface the open volume defects completely disappear. These results are in agreement with the hardness measurements showing little hardness increase in this case.
The suitability of ODS-based materials for nuclear applications was verified.
Keywords: Radiation resistant materials, ODS steel, simultaneous dual beam ion implantation, vacancy clusters, He bubbles, hardness
  • Book chapter
    Ganguly B. N.; Gerhard Brauer, G.: Near-Surface Depth Profiling of Solids by Mono-energetic Positrons, Switzerland: Trans Tech Publishers, 2012, 978-3-03785-524-9, 149-163
    DOI: 10.4028/www.scientific.net/DDF.331.149

Downloads:

Publ.-Id: 17710 - Permalink


The synthesis of cutting-edge laboratory methodology and highly effective analytical service - Resource analytics at the newly founded Helmholtz-Institute Freiberg for Resource Technology (Germany)
Renno, A. D.; Gutzmer, J.; Merchel, S.; Möckel, R.; Krause, J.; Rugel, G.; Haser, S.; Ziegenrücker, R.; Michalak, P. P.;
Based on an initiative of the German Federal Government the Helmholtz Institute Freiberg for Resource Technology (HIF) is being established jointly by the Helmholtz-Zentrum Dresden-Rossendorf and the TU Bergakademie Freiberg. The new institute is to make a vital contribution towards implementing the national German strategy on raw materials. These visions and aims form the intellectual basis for the scientific work at the HIF:
• New technologies for utilization of mineral and metal containing resources from complex domestic and foreign deposits
• Contribution to global environmental protection by means of material and energy efficient extraction and use of raw materials
• Economic networks between Germany and resource countries based on sustainable technologies provided to German industry by the Helmholtz Institute (technology in exchange for access to raw materials)
• Training of new generation of highly qualified academic and technical staff for German industry and academia
The chemical and phase analysis of all natural and synthetic materials involved in the supply chain, named as resource analytics, is one of the backbones of the HIF. During implementation of the Department of analytics we embark on the following strategy:
• Concentration of all competences and capacities in one department available to all other departments
• Avoiding isolated applications
• Strict integration of the analysts during acquisition and design of projects
• Consistent integration of further development of laboratory methodology into scientific projects of the respective departments.
We describe the rationales and present first results of our landmark projects in resource analytics:
• High-speed PIXE of natural and synthetic materials
• Super-SIMS
• Automated mineralogy
• Reference materials for microanalytical methods
and demonstrate the interplay with the common projects of the HIF.
Keywords: Resource Analytics, Super-SIMS, High-speed PIXE, Automated Quantitative Mineralogy, Reference Materials
  • Lecture (Conference)
    GEOANALYSIS 2012 - The 8th International Conference on the Analysis of Geological and Environmental Materials, 16.-20.09.2012, Búzios, Rio de Janeiro, Brasilien

Publ.-Id: 17709 - Permalink


Universal Presence of Elements – still a valid concept?
Renno, A. D.;
In 1936 Ida Noddack published her landmark paper “Über die Allgegenwart der chemischen Elemente” – in English „About Universal presence of Elements“ (Noddack, 1936). In this article she states: “Alle chemischen Elemente kommen in allen Mineralien vor.“ – in English: „All chemical elements are present in all minerals.” This conclusion was based in the painstaking trace element analysis of bulk minerals. She was able to document the presence of such chemical elements as Re in sphalerite down to 10 ppb (Noddack, 1936).
It was, of course impossible for her to anticipate the development of modern microanalytical instrumentation, which is able to operate routinely at the picogram test portion range.
The Helmholtz- Institute Freiberg for Resource Technology is currently working to establish the Super-SIMS method (Döbeli et al, 1994) for analysis of minerals, ores and other materials related to resource technology. The extreme sensitivity of this technique raises the question of the validity of the concept of Universal Presence of Elements. It is expected that the Super-SIMS we will be able to quantify some elements down to the 1 ng/g level (10-12 atoms/atoms) in ideal matrices. Using a commercial available ion probe we will be able to focus the ion beam down to 2 µm in diameter, equivalent to a sampling mass at or below the sub-ng level.
Simulations of the probabilities of finding elements of interest at such low target concentrations show that the Super-SIMS will reach the point that the chance of measuring these elements in such small sampling volumes will be less than 10 %.This leads to a number of new questions which need to be addressed when addressing the topic of a given element yes-or-no. Is the amount of an ultratrace element in a mineral determined by the concentration in the bulk mineral or by the analytical capabilities?
Is it still possible to describe the geochemical behavior of ultratrace elements if the probability of detection of such elements in very tiny volumes approaches zero?
What are the driving forces behind the geochemical behavior of such ultratrace elements?
We hope that the new Super-SIMS facility will help to answer such question in the not too distant future.

References:
Döbeli M., Nebiker P.W., Suter M., Synal H.A., Vetterli D. (1994) „Accelerator SIMS for trace element detection. In: Nucl Instr Meth B85:770–774.
Noddack, I. (1936) “Über die Allgegenwart der chemischen Elemente” in: Angewandte Chemie, Vol. 49(47), pp. 835-854)
Keywords: Geochemistry, Super-SIMS, Universal Presence of Elements, Ultratrace Element, Analytical Geochemistry
  • Lecture (Conference)
    GEOANALYSIS 2012 - The 8th International Conference on the Analysis of Geological and Environmental Materials, 16.-20.09.2012, Búzios, Rio de Janeiro, Brasilien

Publ.-Id: 17708 - Permalink


Reference Materials in Automated Quantitative Mineralogy – experiences and approaches at the Freiberg Geometallurgy Laboratory
Haser, S.; Renno, A. D.; Bartzsch, A.; Weißflog, C.; Sandmann, D.; Schulz, B.; Gutzmer, J.;
Quantitative mineralogy done by automated image acquisition, signal processing and analysis became the principle driving force behind geometallurgical research projects and industrial applications. The same analytical methodology is used in forensic examinations, as well as for petrological, mineralogical and archaeometrical studies.
Recent developments in instrumental techniques, new algorithms for image and signal processing and growing computing power form the basis for this enormous development. The level of automation, the reproducibility and 'superhuman' never-tiring endurance have made this methodology virtually indispensable.
As a consequence of this development, due to the growing economic impact and foreseeable individual consequences as the result of forensic studies, laboratories using automated quantitative mineralogical methods have to face more and more question relating to:
• the accuracy and trueness of measurement,
• measurement precision and measurement reproducibility, and
• metrological traceability.
The routine usage of reference materials (RM) is one of the cornerstones to meet such requirements.
The principle of measurement is the combined detection of back-scattered electron intensities and X-ray spectra, both depending basically on chemical properties of the material studied. Automated quantitative mineralogy is consequently no true (primary) phase analytical method (PAM) and has to be traced back to primary PAMs.
To identify the RMs needed the quantitative mineralogical measurement needs to be separated into distinct steps and tangible variables that influence the success of these steps. The main steps, excluding sampling, are:
1. sample preparation,
2. image acquisition,
3. X-ray spectra acquisition,
4. X-ray spectra processing,
5. image processing including stereological reconstruction of 3-D features,
6. calculation of derived data like mineral mode, particle size distribution, particle shapes,
degree of liberation or the resolution of intergrowth relationships.
In general, quality management for steps 2 and 3 is well established and described in standardized procedures and well covered with RMs. However, the lack of suitable RMs affects all the other steps significantly.
The largest contribution to the uncertainty budget is sample preparation. The preparation of “in-house” standards will improve the situation, but will not reach the effects of future RMs. RMs to assess the correct and reproducible processing of X-ray spectra and the stereological reconstruction are easier to define and fabricable, but very scarce.
The experience of the Freiberg Geometallurgy Laboratory with missing suitable RMs is illustrated and missing inter-laboratory comparability of results is identified as the most serious challenge. First approaches to a solution, focusing on the creation of “in-house” standards as a first step towards a broader approach involving other laboratories worldwide, are presented and critically evaluated.
Keywords: Automated Quantitative Mineralogy, Reference Materials, Geometallurgy, Sample Preparation, Uncertainty Budget
  • Lecture (Conference)
    Microanalytical Reference Materials - An MAS Topical Conference, 15.-17.05.2012, Golden, USA

Publ.-Id: 17707 - Permalink


Element- and method-specific test for microhomogeneity of major and trace elements in reference materials
Renno, A.;
Homogeneity is a relative property of a sample in relation to the measurement (analytical method), the measurand (analyte), and the intended purpose, like the usage as a reference material (RM). The verification of homogeneity is essential to define a RM as fit for purpose. As a result of the lack of suitable RMs for microanalytical methods bulk RMs are used to calibrate the instruments, to validate methods, to estimate uncertainty, and for internal quality control.
To proof the superiority of synthetic mineral phases over natural ones as RMs for microanalytical methods we started to synthesize, different feldspars, pyrite and columbite/tantalite in the framework of a research project founded by the European Union (ESF) and the Free State of Saxony [1]. We hope that our attempt act as a trigger for forthcoming efforts in the production and certification of such RMs. The usage of these synthetic minerals will not restricted to a single analytical method, like electron probe microanalysis or LA-ICP-MS, non-destructive and destructive.
The assessment of homogeneity is an integral part of the synthesis tests and of the following certification. The test comprises several steps considering the relative character of microhomogeneity. This specific feature requires that all such tests have to be adapted to the specific analytical method, the specific element, and the type of microheterogeneity.
Five types of microheterogeneity were defined, based on the work of Malissa [2], Danzer [3], Kempenaers et al. [4], and Inczédy [5].
•random (stochastic) type
•systematic type
•nugget type
•island type
•periodic type.
A particular sampling strategy was defined for each type of microheterogeneity. The single calculations consider the different element- and method dependent 'information values', by using simulation software like CASINO, PENEPMA, SRIM or PyMCA.
The second step is the assessment of a critical mass in the sense of Danzer [6] and Kempenaers et al. [4] for every element.
The last measure requires the specification of the minimal volume of the whole synthesized mineral and the distance between sub-samples to be checked for microhomogeneity, following the procedures described by Chayes [7] for classical modal analysis of rocks [8].
[1]P.P. Michalak, A.D. Renno, S. Merchel, F. Munnik, M. Wiedenbeck, Microsc. Microanal. 17 (Suppl 2), 2011, 852-853.
[2]H. Malissa, K. Swoboda, Radex, 1963, 494.
[3]K. Danzer, Spectroch. Acta, 1984, 949-954.
[4]L. Kempenaers et al., Anal. Chem., 2002, 5017-5026.
[5]J. Inczédy, Talanta, 1982, 643-645.
[6]K. Danzer, Talanta, 1977, 561-565.
[7]F. Chayes, Petrographic Modal Analysis – An elementary statistical appraisal, John Wiley & Sons, New York, 1956.
[8]This project is supported by the European Union (ESF) and the Free State of Saxony. Many thanks to the custodians of the Geoscientific Collections in Freiberg for saving and providing an invaluable source of material. Motivating discussions on several facets of this study with Jens Gutzmer, Michael Wiedenbeck, Uwe Reinholz, and Slavo Michalak were very helpful.
Keywords: Reference Materials, Homogeneity, Heterogeneity, Homogeneity Test
  • Invited lecture (Conferences)
    Microanalytical Reference Materials - An MAS Topical Conference, 15.-17.05.2012, Golden, USA

Publ.-Id: 17706 - Permalink


Periodic pattern induced by low energy ion irradiation
Facsko, S.;
The morphology of surfaces after irradiation with low en- ergy ions (E < 50 keV) exhibits a variety of character- istics depending on the ion beam parameters and the ma- terial properties. Surfaces exposed to the ion beam can turn atomically smooth, stochastically or self-affine rough, or can evolve towards regular self-organised patterns. The structure size of these patterns is in the range of 10 to 100 nm and occasionally a high degree of ordering is achieved. Therefore, they have attracted interest recently as templates for nanostructured thin films or for structuring films by an erosive process [1].
Keywords: ion irradiation, nanostructures
  • Lecture (others)
    Spirit Workshop, 18.-20.07.2012, Lisboa, Portugal

Publ.-Id: 17705 - Permalink


Ion induced patterns on Ge surfaces
Facsko, S.; Fritzsche, M.; Ou, X.; Keller, A.; Mücklich, A.;
Low energy ion irradiations of surfaces can induce the formation of periodic patterns with periodici-ties in the range of a few tenths to a few hundreds of nanometers. These patterns have been used as templates for growing thin films with interesting anisotropic properties resulting from the modu-lation of their interface and surface.
At off-normal incidence ripple patterns oriented perpendicular to the ion beam direction are ob-served after prolonged ion irradiation. At normal incidence or for incidence angles smaller than 55° smoothing dominates on Si and Ge surfaces. However, if more than one atomic species is present on the irradiated surface, e.g. due the ion beam itself or co-deposited atoms on elemental materials or for compounds, additional instabilities may exist leading to periodic patterns also at normal ion incidence. These patterns are isotropic and can either appear as dot or hole patterns exhibiting short range hexagonal order.
We studied the formation of hexagonally arranged hole patterns on Ge(001) surfaces induced by irradiation with a scanned focused Ga+ ion beam (FIB). Hole patterns with characteristic length of 50 nm are observed in a narrow energy range of 5 - 7 keV (Fig. 1 a,b). These patterns are inde-pendent of ion flux in a range of several orders of magnitude. In addition, the patterns induced by FIB irradiations were compared to broad beam Ga+ irradiations at the same ion energies. No dif-ferences were found demonstrating that FIB irradiations with a large overlap of the scanned beam are identical to conventional broad beam irradiations.
We studied also ion induced pattern formation on Ge surfaces with 1 keV Ar+ at higher temperature. In contrast to irradiations at low temperature we found pattern formation even at normal ion incidence. Similar to the case of ion irradiated crystalline metal surfaces on the crystalline Ge sur-face a new instability appears at higher temperature due to the Ehrlich-Schwoebel barrier. Here, we observe regular checkerboard or hole patterns with the symmetry of the patterns reflecting the crystal structure of the irradiated surface (see Fig. 1c,d).
Keywords: nanostructures, ion irradiation
  • Lecture (Conference)
    Workshop Ionenstrahlphysik, 10.-11.07.2012, Augsburg, Deutschland

Publ.-Id: 17704 - Permalink


Morphology induced magnetic anisotropy and damping in thin films
Körner, M.;
Both, modification of magnetic anisotropy as well as damping, are of fundamental and technological importance. When miniaturizing the dimensions of a magnetic device roughness becomes more and more important, e.g. induced anisotropies have to be taken into account. Additionally new effects like direction dependent, defect induced two-magnon scattering are enabled. This opens the possibility for new types of devices where the damping can be set by an external magnetic field or by frequency.
Broad ion beam erosion is a well-established technique for structuring large scale surfaces. By varying the ion irradiation parameters, e.g. ion energy, fluence, incident angle, and sample temperature sinusoidally modulated surface corrugations (ripples) can be created with a periodicity tuneable over a wide range. Growing magnetic materials on these rippled substrates imprints the surface corrugation to the deposited material and induces a uniaxial magnetic anisotropy (UMA), caused by dipolar effects, where the strength of the UMA is wavelength dependent. On the other hand the imprinted surface corrugation can serve as spin wave scattering center in thin magnetic films, modifying the magnetic damping properties by introducing a two-magnon scattering contribution.
The in-plane anisotropy and damping properties of magnetic films grown on rippled substrates were investigated by means of angular as well as frequency dependent vector network analyzer ferromagnetic resonance. In case of tailoring magnetic anisotropy, the influence of single-crystalline thin iron films epitaxially grown on rippled MgO substrates will be presented. Here a superposition of magneto-crystalline and morphology induced UMA is observed, where the UMA can be set to an arbitrary direction with respect to the crystalline anisotropy. Furthermore the influence of rippled surfaces on thin polycrystalline Ni80Fe20 films will be discussed, where the surface corrugation acts as spin wave scattering center introducing a two-magnon scattering damping contribution. The latter leads to distinct peaks in the frequency dependent linewidth and a uniaxial in-plane damping behavior.
  • Lecture (others)
    Seminar at Lawrence Berkeley National Lab, 14.05.2012, Berkeley, CA, USA

Publ.-Id: 17702 - Permalink


Morphology induced magnetic anisotropy and damping in thin films
Körner, M.;
Both, modification of magnetic anisotropy as well as damping, are of fundamental and technological importance. When miniaturizing the dimensions of a magnetic device roughness becomes more and more important, e.g. induced anisotropies have to be taken into account. Additionally new effects like direction dependent, defect induced two-magnon scattering are enabled. This opens the possibility for new types of devices where the damping can be set by an external magnetic field or by frequency.
Broad ion beam erosion is a well-established technique for structuring large scale surfaces. By varying the ion irradiation parameters, e.g. ion energy, fluence, incident angle, and sample temperature sinusoidally modulated surface corrugations (ripples) can be created with a periodicity tuneable over a wide range. Growing magnetic materials on these rippled substrates imprints the surface corrugation to the deposited material and induces a uniaxial magnetic anisotropy (UMA), caused by dipolar effects, where the strength of the UMA is wavelength dependent. On the other hand the imprinted surface corrugation can serve as spin wave scattering center in thin magnetic films, modifying the magnetic damping properties by introducing a two-magnon scattering contribution.
The in-plane anisotropy and damping properties of magnetic films grown on rippled substrates were investigated by means of angular as well as frequency dependent vector network analyzer ferromagnetic resonance. In case of tailoring magnetic anisotropy, the influence of single-crystalline thin iron films epitaxially grown on rippled MgO substrates will be presented. Here a superposition of magneto-crystalline and morphology induced UMA is observed, where the UMA can be set to an arbitrary direction with respect to the crystalline anisotropy. Furthermore the influence of rippled surfaces on thin polycrystalline Ni80Fe20 films will be discussed, where the surface corrugation acts as spin wave scattering center introducing a two-magnon scattering damping contribution. The latter leads to distinct peaks in the frequency dependent linewidth and a uniaxial in-plane damping behavior.
  • Lecture (others)
    Seminar at HGST, a Western Digital company, 17.05.2012, San Jose, CA, USA

Publ.-Id: 17701 - Permalink


Morphology induced magnetic anisotropy and damping in thin films
Körner, M.;
Both, modification of magnetic anisotropy as well as damping, are of fundamental and technological importance. When miniaturizing the dimensions of a magnetic device roughness becomes more and more important, e.g. induced anisotropies have to be taken into account. Additionally new effects like direction dependent, defect induced two-magnon scattering are enabled. This opens the possibility for new types of devices where the damping can be set by an external magnetic field or by frequency.
Broad ion beam erosion is a well-established technique for structuring large scale surfaces. By varying the ion irradiation parameters, e.g. ion energy, fluence, incident angle, and sample temperature sinusoidally modulated surface corrugations (ripples) can be created with a periodicity tuneable over a wide range. Growing magnetic materials on these rippled substrates imprints the surface corrugation to the deposited material and induces a uniaxial magnetic anisotropy (UMA), caused by dipolar effects, where the strength of the UMA is wavelength dependent. On the other hand the imprinted surface corrugation can serve as spin wave scattering center in thin magnetic films, modifying the magnetic damping properties by introducing a two-magnon scattering contribution.
The in-plane anisotropy and damping properties of magnetic films grown on rippled substrates were investigated by means of angular as well as frequency dependent vector network analyzer ferromagnetic resonance. In case of tailoring magnetic anisotropy, the influence of single-crystalline thin iron films epitaxially grown on rippled MgO substrates will be presented. Here a superposition of magneto-crystalline and morphology induced UMA is observed, where the UMA can be set to an arbitrary direction with respect to the crystalline anisotropy. Furthermore the influence of rippled surfaces on thin polycrystalline Ni80Fe20 films will be discussed, where the surface corrugation acts as spin wave scattering center introducing a two-magnon scattering damping contribution. The latter leads to distinct peaks in the frequency dependent linewidth and a uniaxial in-plane damping behavior.
  • Lecture (others)
    Seminar at IBM Almaden Research Center, 15.05.2012, San Jose, CA, USA

Publ.-Id: 17700 - Permalink


Scientific publishing – writing successful papers
Werniewicz, K.;
Scientific publishing is an important part of every researcher’s life. Not only does it educate but it enhances awareness of and promotes your research achievements. It is one of the critical factors contributing to the establishment and subsequent strengthening of your position within the scientific community.
However, before spending long hours conducting laborious experiments culminating in a scientific document, you must ensure that your manuscript has ticked all of the boxes required for a successful publication. No matter how good your work itself is, how outstanding your research outcomes are, if their presentation is incorrect, you will be asked to either re-write your paper (optimistic outcome) or it will be desk-rejected. With so much effort involved in the experimental and writing process, the very last response you would like to receive is:
“Your manuscript has been reviewed and is being declined for publication in …”
Success is the driving force, whilst failure demotivates and weakens our self- confidence.
Trying to avoid the above-mentioned situation, the following lecture provides you with valuable hints on how to meet the expectations of the rigorous Editors and Reviewers and turn your paper into a success. Based on my own experience gained as a Managing Editor for the Journal of Alloys and Compounds (Elsevier), the step-by-step manuscript screening process (from submission to final decision) will be presented and discussed in detail.
  • Invited lecture (Conferences)
    BioTiNet Summer School: Titanium in Medicine, 04.-08.06.2012, Caldes d’Estrac, Barcelona., Spain
  • Lecture (others)
    FWI Seminar, 02.03.2012, HZDR, Germany
  • Invited lecture (Conferences)
    IX-th INTERNATIONAL CONFERENCE ION IMPLANTATION AND OTHER APPLICATIONS OF IONS AND ELECTRONS, 25.-28.06.2012, Kazimierz Dolny, Poland

Publ.-Id: 17699 - Permalink


Low-cost and large-area electronics, roll-to-roll processing and beyond.
Werniewicz, K.; Skorupa, W.;
A new emerging trend in the design of modern semiconductor devices dedicated to scaling-up, rather than reducing, their dimensions is presented. To realize volume manufacturing, alternative semiconductor materials with superior performance, fabricated by innovative processing methods, are essential. In our short presentation a general overview of the material and technology evolution in the area of macroelectronics, which grew in the shadow of the well-established chip technology, will be given. The major challenges of large-scale production will be discussed. Particular attention will be focused on describing advanced, short-term heat treatment approaches, which offer a range of advantages compared to conventional annealing methods. There is no doubt that large area and flexible electronic systems constitute an important research topic for the semiconductor industry. The ability to fabricate highly efficient macroelectronics by inexpensive processes will have a significant impact on a range of diverse technology sectors. A new era “towards semiconductor volume manufacturing…” has begun.
  • Lecture (Conference)
    IX-th INTERNATIONAL CONFERENCE ION IMPLANTATION AND OTHER APPLICATIONS OF IONS AND ELECTRONS, 25.-28.06.2012, Kazimierz Dolny, Poland

Publ.-Id: 17698 - Permalink


The new 6 MV tandem accelerator at HZDR
Akhmadaliev, S.; Rugel, G.; Kolitsch, A.; von Borany, J.;
Recently, a new 6 MV tandem accelerator was put into operation at Helmholtz-Zentrum Dresden-Rossendorf.
The accelerator is dedicated for non-destructive spatial- and depth-resolved analysis using ion beam techniques as well as for materials modification via high energy ion implantation. Additionally this opens a new field of research at HZDR - accelerator mass spectrometry (AMS).

The system is based on a medium current 6 MV-TandetronTM manufactured by High Voltage Engineering Europe (HVEE).
It operates via a Dynamitron type high voltage generator providing the terminal voltage 0.3 – 6.6 MV with high stability.
The accelerator has two separate ion injection systems. The multipurpose ion injector (MPI) with a Cs-sputter ion source and a He-duoplasmatron is dedicated to ion beam analysis and high energy ion implantation. A second injector used exclusively for AMS purposes consists of two Cs-sputter ion sources combined with a multi-cathode sample wheel.

The high energy mass spectrometer includes 90°-analysing magnet, electro¬static analyser, vertical 30° magnet and gas ionisation detector. The AMS facility is applied for precise measurements of radio-nuclides like 10Be, 26Al, 36Cl, 41Ca, and 129I with ultimative sensitivity.

The interconnecting beam-line con¬nects the new accelerator with the existing IBA equipment of the old 5 MV tandem accelerator taken out of operation in end of 2010. This equip¬ment is used for RBS, ERD (including high resolution ERD), PIXE/ PIGE, NRA and IBA with external protons beam.

High-energy ion implantation or irradiations can be performed at two different endstations. One of them is equipped with an automatic wafer-handling system allowing irradiation of samples with size up to 20 cm x 20 cm which is routinely applied for industrial services.
Keywords: Tandem accelerator, IBA, AMS
  • Lecture (Conference)
    Workshop Ionenstrahlphysik, 10.-11.07.2012, Augsburg, Deutschland

Publ.-Id: 17697 - Permalink


Generation and characterization of novel metastatic variants of the human melanoma cell line Mel-Juso
Mosch, B.; Pietzsch, J.;
Introduction: Melanoma is a highly metastatic tumor with early metastasis in distant organs like lymph nodes, lungs, liver and brain. In order to understand the complex process of metastasis and to identify molecules involved, suitable in vivo and in vitro models are essential. The aim of this study was to establish variants of the human melanoma cell line Mel-Juso with same genetic background but different metastatic potential.
Material and Methods: Mel-Juso cells were inoculated into the tail vein of athymic nude mice. Lung metastases were harvested, pooled, cultured in vitro and injected in another set of mice. Different melanoma variants were generated by repeated cycles of in vivo passage. The obtained metastatic variants (L3 and L5) were characterized genetically and concerning the expression of a melanoma marker, certain Eph receptor tyrosine kinases, growth properties, and in vivo metastasis.
Results and Discussion: STR DNA genotyping showed no differences between the parental cell line and two selected metastatic variants. Moreover, no differences in the expression of the melanoma-associated chondroitin sulfate proteoglycan and in Eph receptors could be detected. Interestingly, we detected a reduced proliferation in metastatic variants accompanied by reduced or even lost capability of colony formation, indicating some substantial changes in metastatic properties despite of genetic similarity. Nevertheless, these in vitro differences between Mel-Juso and the metastatic variants could not be confirmed in an in vivo metastasis assay. Therefore, we started an additional cycle of in vivo passage with preparation of metastatic variants (L6) from individual lung metastases. By now 15 individual cell clones could be established derived from lungs of 4 individual mice and are currently analyzed concerning their cellular properties.
Conclusion: The generation of melanoma cell line variants with same genetic background and different metastatic potential showed no success when using pooled lung metastases. Further steps will focus on the generation of variants from individual metastases to better reflect the varying tumorigenic potential of individual melanoma cells. Using such variants would facilitate the identification of molecules involved in metastasis, which show promise to be potential targets for the diagnosis and therapy of metastatic melanoma.
  • Poster
    EACR-22 - from Basic Research to Personalised Cancer Treatment, 07.-10.07.2012, Barcelona, Spain
  • Contribution to proceedings
    EACR-22 - from Basic Research to Personalised Cancer Treatment, 07.-10.07.2012, Barcelona, Spain
    European Journal of Cancer (EJC), Oxford: Elsevier, 0959-8049, S54

Publ.-Id: 17696 - Permalink


Response of human mesenchymal stem cells to ion-sputtered surfaces
Keller, A.; Andersen, O. Z.; Foss, M.; Facsko, S.; Kraft, D. C.; Besenbacher, F.;
Artificial biomaterials play an important role in bioengineering, e.g. in regenerative medicine, biosensing, and orthopedics. The success of orthopedic implants depends on early bone formation and strong binding between bone and implant. The ability of osteogenic cells to adhere, proliferate, and differentiate on the implant surface is thus crucial for the formation of new bone tissue and the subsequent osseointegration of the implant.
Bone is a hierarchically composed biomaterial exhibiting topographical features such as fiber networks, interconnecting pores, and mineral crystallites with dimensions ranging from the macro to the nanoscale [1]. Micro and nanoscale surface topography thus has a strong influence on the proliferation, morphology, and differentiation of various cell types [2]. Therefore, the topographical design of implant surfaces is a promising route toward novel and improved medical implants [1].
Recently, it was demonstrated that even topographical features with a height below 10 nm can affect the adhesion and proliferation of mesenchymal stem cells (MSCs) [3]. However, only few techniques provide reliable control of the nanoscale surface topography over macroscopic areas. Therefore, in this work, we investigate the response of MSCs to well-defined nanorippled surfaces fabricated by ion-beam sputtering which enables a precise tuning of the pattern dimensions by adjusting the ion energy [4]. The periodicity and height of the patterns range from ~50 to ~600 nm and from ~3 nm to ~60 nm, respectively. A strong influence of the ripple dimensions on MSC proliferation and morphology is observed.
[1] Stevens and George, Science, 310, 1135 (2005).
[2] Lord, Foss, and Besenbacher, Nano Today, 5, 66 (2010).
[3] Dolatshahi-Pirouz et al., ACS Nano, 4, 2874 (2010).
[4] Fassbender et al., New J. Phy., 11, 125002 (2009).
  • Lecture (Conference)
    Workshop Ionenstrahlphysik, 10.-11.07.2012, Augsburg, Deutschland

Publ.-Id: 17695 - Permalink


X-ray irradiation influences Eph receptors and cellular properties in human melanoma cells
Mosch, B.; Pietzsch, D.; Pietzsch, J.;
Introduction: There is experimental evidence that X-ray irradiation influences survival and metastatic properties of tumor cells. On the other hand, metastasis and cellular motility can be modified by EphA2 and EphA3, two members of the Eph receptor/ephrin family of receptor tyrosine kinases. The aim of this study was to analyze whether there is a molecular link between X-ray irradiation, Eph expression, and modification of metastasis-associated cell properties in human melanoma cells.
Material and Methods: We irradiated one pre-metastatic and three metastatic human melanoma cells lines, including one self-generated metastatic variant, with X-rays (5 and 10 Gy). At day 1 and day 7 post irradiation (p.i.) we analyzed cell proliferation, colony formation, adhesion, and migration. Additionally, selected Eph receptors and ephrin ligands were analyzed regarding irradiation-dependent changes in mRNA and protein content. For EphA2 and selected downstream signaling molecules we determined the phosphorylation status, representing protein activity.
Results and Discussion: Irradiation resulted in decreased proliferation and colony formation. Colony formation showed partial recovery at 7 days p.i. with 5 Gy. Regarding cell adhesion, we detected an irradiation-induced increment paralleled by a decrease in migration of Mel-Juso and Mel-Juso-L3 cells and, in part, A375 cells. Thus, we assume that X-rays merely act anti-metastatic on the investigated melanoma cells. Expression of the ephrins A1 and A5 generally was very low and after Xray showed a substantial decrement for ephrin A5 in all cells, but a heterogenous behaviour for ephrin A1. For EphA2 we detected a decrease after irradiation both in expression and activity at 7 days p.i. In contrast, EphA3 was found to be up-regulated in 3 of 4 analyzed cell lines, raising the question, if there is a counter-regulation between EphA2 and EphA3. Analyzing downstream signaling, we detected decreased Src kinase and focal adhesion kinase (FAK) phosphorylation in A375, A2058, and Mel-Juso cells at 10 Gy for Src and both 5 Gy and 10 Gy for FAK at 7 days p.i.
Conclusion: Our findings indicate that irradiation-induced downregulation of EphA2 and up-regulation of EphA3 in human melanoma cells is associated with anti-metastatic effects. The observed effects are assumed partly to be mediated by regulation of Src and FAK through EphA2.
  • Poster
    EACR-22 - from Basic Research to Personalised Cancer Treatment, 07.-10.07.2012, Barcelona, Spain
  • Contribution to proceedings
    EACR-22 - from Basic Research to Personalised Cancer Treatment, 07.-10.07.2012, Barcelona, Spain
    European Journal of Cancer (EJC), Oxford: Elsevier, 0959-8049, S269

Publ.-Id: 17694 - Permalink


Globale Rohstoffmärkte- seltene Erden und ihr Recycling
Fahimi, I.; Gutzmer, J.;
Die Situation der globalen Märkte für Seltene Erden macht das Recycling Seltener Erden zu einer wichtigen Strategie um an wirtschaftsstrategische Rohstoffe zu kommen.
  • Lecture (Conference)
    17. Tagung Siedlungsabfallwirtschaft Magdeburg Restabfall – Recycling – Ressource, 12.-13.09.2012, Magdeburg, Deutschland
  • Open Access LogoContribution to proceedings
    17. Tagung Siedlungsabfallwirtschaft Magdeburg: Restabfall – Recycling – Ressource, 12.-13.09.2012, Magdeburg, Deutschland
    Proceedings der 17. Tagung Siedlungsabfallwirtschaft Magdeburg: Restabfall – Recycling – Ressource

Publ.-Id: 17692 - Permalink


Defektuntersuchungen an HAVAR-Folien mittels Positronen-Lebensdauer- und –Doppler-Verbreiterungs-Messungen
Anwand, W.; May-Tal Beck, S.; Harush, M.; Eisen, A.; Ocherashvili, A.; Hen, O.; Butterling, M.; Wagner, A.;
HAVAR ist ein sehr festes, nicht magnetisches und korrosionsbeständiges Material. In der Medizintechnik wird es als Fenster für Targetkammern zur Produktion von Fluordesoxyglucose (FDG) benutzt. Das in der FDG enthaltene 18F findet Verwendung in der Positronen-Emissions-Tomographie als beta+-Strahler. Die Herstellung des 18F erfolgt dabei durch Protonenbestrahlung von 18O angereicherten Wassertargets entsprechend der Reaktion 18O(p,n)18F. Der wachsende Bedarf an 18FDG erfordert eine intensivere Protonenbestrahlung und damit eine höhere Beanspruchung der HAVAR-Folie als Targetfenster.
Für eine Prognose der Beständigkeit der HAVAR-Folien gegenüber Protonenbestrahlung sind Informationen über die Defektstruktur innerhalb der Folien und deren strahlungsinduzierte Veränderungen erforderlich. Deshalb wurden 25 µm dicke HAVAR-Folien sowohl im Ausgangszustand, nach Wärmebehandlung und nach Protonenbestrahlung hinsichtlich der Ausbildung von leerstellenartigen Defekten mittels konventioneller Positronen-Lebensdauermessungen untersucht. Oberflächennahe Untersuchungen bis in Tiefen von ca. 3 µm erfolgten mit einer mono-energetischen Positronenstrahlapparatur durch Messung der Doppler-Verbreiterung der Annihilationslinie.
Unterschiede in der Ausbildung der Defekte in Abhängigkeit von der Probenpräparation und –beanspruchung werden dargestellt und mit Ergebnissen, erhalten aus der Transmissions-Elektronenmikroskopie, verglichen.
Keywords: HAVAR; PET; strahlungsinduzierte Schädigung; PAS
  • Lecture (Conference)
    Workshop "Ionenstrahlphysik", 09.-11.07.2012, Augsburg, Deutschland

Publ.-Id: 17691 - Permalink


Characterization of the neutron beam at nELBE
Beyer, R.; Birgersson, E.; Elekes, Z.; Ferrari, A.; Grosse, E.; Hannaske, R.; Junghans, A. R.; Kögler, T.; Massarczyk, R.; Matic, A.; Nolte, R.; Schwengner, R.; Wagner, A.;
The neutron time-of-flight setup nELBE at the Helmholtz-Zentrum Dresden-Rossendorf got operational. Using an intense electron beam impinging on a liquid lead target neutrons are produced in the energy range from about 10 keV up to 10 MeV. This neutron source will be used to measure fast-neutron induced reactions with relevance for future nuclear transmutation facilities like Generation IV nuclear reactors or Accelerator Driven Systems (ADS). The profile, the intensity, the energy distribution, and the time structure of the nELBE neutron beam have been investigated and the techniques how they are measured will be explained in this work.
Keywords: nELBE, Neutron time-of-flight, Fast neutrons, Photoneutron production

Publ.-Id: 17690 - Permalink


Retrieval and Biodiversity of Biofilms of an Underground Uranium Mine
Zirnstein, I.; Arnold, T.; Krawczyk-Baersch, E.; Wobus, A.; Röske, I.;
Acid mine drainages (AMD) result from in-situ leaching with sulfuric acids. These acidic waters in the underground of the former uranium mine Königstein (Saxony, Germany) are characterized by high concentrations of metals (U, Fe) and sulfate (low pH) and flow through the sandstone. Biofilms grow in this unique subsurface habitat (250 meters below ground) either as stalactite-like slime communities (snotites) or as acid streamers in the drainage channels. Previously conducted studies on the bacterial diversity in both biofilm communities showed that beta-proteobacterium affiliated with Ferrovum myxofaciens, also designated “Ferribacter polymyxa” were identified as dominating bacterial species.
Biofilms are not only composed of bacteria, but may also include eukaryotic organisms. The eukaryotic diversity of the Königstein biofilms was analysed by molecular methods, i.e. 18S rDNA PCR, cloning and sequencing, which were used to determine the DNA-fragments of the microorganism, and by microscopic investigations. It was found that the eukaryotic biofilm communities of the Königstein environment showed a limited number of different heterotrophic species and consist of a variety of lineages belonging to nine major taxa: Ciliates, Flagellates, Amoebae, Heterolobosea, Fungi, Apicomplexa, Stramenopiles, Rotifers and Arthropoda and in addition a large number of uncultured eukaryotes, denoted as acidophilic eukaryotic cluster (AEC). Since 2010 the Königstein mine was flooded, and the galleries are no longer accessible for sampling. Biofilm analyses are now possible by pumping the flooding water from underground to the surface, through biofilm sampling devices, e.g. biofilm reactors. The In-situ Biofilm reactor (165 cm in length and 39 cm in diameter) included biofilm carriers where water microorganisms are attached to the carrier surface, indicated by the brown and slimy appearance. Biofilms on the carriers were used for different investigations e.g. CARD-FISH and pyrosequencing for determine the biodiversity after flooding.
Keywords: 16S rDNA PCR, 18S rDNA PCR, acid mine drainage, biofilm, environmental microbiology, microbial biodiversity, microbial ecology, uranium
  • Lecture (Conference)
    Biofilms 5 International Conference, 10.-12.12.2012, Paris, France
  • Poster
    Biofilms 5 International Conference, 10.-12.12.2012, Paris, France

Publ.-Id: 17689 - Permalink


Gesamte Wertschöpfungskette im Blick
Gutzmer, J.; Klossek, A.;
Das Helmholtz-Institut Freiberg für Ressourcentechnologie wurde am 29. August 2011 gegründet und wird gemeinsam durch das Helmholtz-Zentrum Dresden-Rossendorf und die TU Bergakademie Freiberg aufgebaut. Das Institut hat das Ziel, innovative Technologien für die Wirtschaft zu entwickeln, um mineralische und metallhaltige Rohstoffe effizienter bereitzustellen und zu nutzen sowie umweltverträglich zu recyceln.
Mit Grundlagen- und anwendungsorientierter interdisziplinärer Forschung, bei der alle Stufen der Rohstoff-Wertschöpfungskette vernetzt werden, wird eine strategische Lücke zwischen der bergbaulichen Kompetenz bei der Gewinnung und dem Knowhow von Rohstoffanwendungen in der deutschen aber auch in der europäischen Forschung geschlossen. Das Institut positioniert sich damit als nationales Kompetenzzentrum für die Erforschung, die Entwicklung und die Innovation von Technologien, die strategisch wichtige mineralische sowie insbesondere metallhaltige Rohstoffe bereitstellen.
Keywords: Helmholtz Institut Freiberg
  • Resource (2012)2, 25-28

Publ.-Id: 17688 - Permalink


A multiple sulfur and organic carbon isotope record from non-conglomeratic sedimentary rocks of the Mesoarchean Witwatersrand Supergroup, South Africa
Guy, B. M.; Ono, S.; Gutzmer, J.; Kaufman, A. J.; Lin, Y.; Fogel, M. L.; Beukes, N. J.;
sulfur isotope ratios (36S/34S/33S/32S) and organic carbon isotope ratios (13C/12C) were measured from 198 non-conglomeratic sedimentary samples that were collected from five deep diamond drill-cores that cover the majority of the ca. 2.96–2.82 Ga Witwatersrand Supergroup. 13Corg, 34Spy and 33Spy values of the sample set range from
−44.3 to
−21.9‰,
−3.7 to +16.5‰ and
−4.0 to +1.9‰, respectively.
These geochemical data vary relative to depositional facies (proximal marine, distal marine and fluvialdominated) and tectonic setting (trailing margin and foreland basin).
In the trailing margin setting of the ∼2.96 Ga Hospital Hill Subgroup, the proximal marine depofacies is characterized by relatively high organic carbon contents (up to 0.9 wt.%) and 13Corg values around −28‰, in contrast to the distal marine depofacies that yields low organic carbon contents (0.01 wt.%) and high 13Corg values (up to −22‰). Both depofacies yield low sulfur contents (0.02 wt.‰), a narrow range of 34S values (∼+3 ±2‰) and positive 33S values (up to +1.9‰). This data is consistent with photoautotrophic carbon fixation in shallow marine environments and limited organic carbon production/preservation in deeper water settings due to longer transport distances and effective biological degradation (e.g., Fe-reducing microbes). Positive 33S values imply that sulfur was largely derived from a photochemical elemental sulfur reservoir. In the foreland basin tectonic setting of the ∼2.94 Ga Government and ∼2.92 Ga Jeppestown subgroups, shelf deposits associated with fluvial braidplain depofacies are characterized by 13C-depleted organic carbon (∼−44 to −38‰), relatively high sulfur contents (0.2–1.3 wt.%), variable 34S values (−3.7 to +16.5‰) and small negative 33S values (∼−0.4‰). These data suggest that the microbial community in the fluvial-dominated depofacies may have consisted of photoautotrophs, methanogens, anaerobic methanotrophs and sulfate reducers. Sulfate was derived from a variety of sources that include photochemical, crustal and marine sulfur reservoirs.
The occurrence of three regionally persistent diamictite deposits in the Government Subgroup coincides with the onset of compressional tectonics and development of pyritic shales with highly 13Cdepleted organic carbon, suggesting that an increase in continental sulfur flux and methane oxidation may have triggered the Mesoarchean glaciations (drawdown of H2 and CH4). However, the link between large 33S anomalies (−4.0 to +1.2‰) and diamictite suggests low levels of atmospheric oxygen and minimal dilution of photochemical signatures.
Keywords: Diagenetic pyrite, Mesoarchean, Sulfur mass-independent fractionation, Witwatersrand Supergroup, Anaerobic methanotrophy, Diamictite

Publ.-Id: 17687 - Permalink


The value of adaptive mineral processing based on spatially varying ore fabric parameters
van den Boogaart, K. G.; Weißflog, C.; Gutzmer, J.;
We show that adapting the mineral processing to the local ore fabric (mineralogy and microstructure) can substantially improve the profitability of the mine, however, only a proper geomathematical methodology using conditional expectations of profits rather than direct measurements can avoid losses. Based on geometallurgical exploration data and processing models potential gain and actual gain of this approach can be quantified before exploitation commences. Rules for optimal decisions, estimators for the gain of this approach from exploration data, and a method to compute the optimal geometallurgical sampling density are presented.
Keywords: Geometallurgy, adaptive mineral processing, geostatistics
  • Open Access LogoContribution to proceedings
    IAMG 2011 conference, 05.-09.09.2011, Salzburg, Österreich
    Mathematical Geosciences at the Crossroads of Theory and Practice - Proceedings IAMG 2011 conference, 978-3-200-02566-0, 609-621

Publ.-Id: 17686 - Permalink


The compositional meaning of the dection limit
van den Boogaart, K. G.; Tolosana-Delgado, R.; Bren, M.;
In compositional data analysis a value below detection limit (BDL) is typically modeled as the definitive information that the actual value is below some fixed value - the detection limit (see e.g. Palarea-Albaladejo et. al (2007, 2008)). Analytical chemistry (Heinrichs and Herrmann (1990); Fletcher (1981); Kellner et al. (2004)) however has a different view on measured concentrations. The measured concentration Cm is not the true concentration cm of the measurant but a quantity computed from an observable quantity Om through a calibration equation. This has serious consequences for the interpretation and statistical analysis of below detection limit observations in the context of compositional data analysis.
Keywords: BDL, detection limit, compositional data analysis
  • Open Access LogoContribution to proceedings
    4th International Workshop on Compositional Data Analysis (2011), 09.-13.05.2011, Sant Feliu de Guíxols, Espania
    Proceedings of the 4th International Workshop on Compositional Data Analysis (2011)

Publ.-Id: 17685 - Permalink


Kontaktlose Durchflussmessung in Metallschmelzen
Buchenau, D.; Gerbeth, G.; Priede, J.;
Control of the flow rate of liquid metals is required in a number of technological processes such as the cooling of nuclear reactors, transmutation systems and the dosing and casting of liquid metals. Electromagnetic flow meters play an important role in the diagnostics and automatic control of such processes. For example, the electromagnetic control of casting processes can be used to improve the quality of products by reducing their brittleness and increasing durability at high production efficiency, especially for complex shape components. A number of different electromagnetic flow meter designs have been developed starting from the end of the forties of the last century. One such flow meter - the magnetic flywheel, which is described in the textbook of Shercliff uses the electromagnetic force exerted by the flow on a close magnet. Commercial electromagnetic flow meters are typically based on the flow-induced electrical voltage measurements by electrodes in direct contact to the melt in a steady magnetic field. In view of the typical problems coming along with applications at liquid metal flows such as high temperatures, interfacial effects and corrosion, the main disadvantage of this type of flow meter is the electrical contact to the liquid metal, which is necessary to measure the electric potential difference. Therefore, contactless operating measurement techniques are very attractive for liquid metal applications.
Keywords: Contactless electromagnetic flow meter, liquid metal, phase shift, rotational frequency
  • Technisches Messen 79(2012)9, 389-393

Publ.-Id: 17684 - Permalink


Linear Models with Compositions in R
Tolosana-Delgado, R.; van den Boogaart, K. G.;
This chapter contains sections titled:

Introduction

The Illustration Data Set

Explanatory Binary Variable

Explanatory Categorical Variable

Explanatory Continuous Variable

Explanatory Composition

Conclusions

Acknowledgement

References
Keywords: linear models with compositions in R - checking intrinsic relations between (sets of) variables;explanatory variables, categorical variables - analysis of the variance (ANOVA), or analysis of the covariance (ANCOVA);classical concept of linear combination - meaningless on the simplex
  • Book chapter
    Vera Pawlowsky-Glahn, Antonella Buccianti: Compositional Data Analysis: Theory and Applications, Chichester, UK: John Wiley & Sons, Ltd, 2011, 9780470711354
  • Book chapter
    Vera Pawlowsky-Glahn, Antonella Buccianti: Compositional Data Analysis: Theory and Applications, Chichester, UK: John Wiley & Sons, Ltd, 2011, 9781119975462-1
    DOI: 10.1002/9781119976462

Publ.-Id: 17683 - Permalink


Geostatistics for Compositions
Tolosana-Delgado, R.; van den Boogaart, K. G.; Pawlowsky-Glahn, V.;
This chapter contains sections titled:

Introduction

A Brief Summary of Geostatistics

Cokriging of Regionalised Compositions

Structural Analysis of Regionalised Composition

Dealing with Zeros: Replacement Strategies and Simplicial Indicator Cokriging

Application

Conclusions

Acknowledgements

References
Keywords: geostatistics for compositions - any multivariate geostatistical data set, compositional in nature;geostatistics, collection of techniques - and tools, analysing regionalised data sets;problems of geostatistics
  • Book chapter
    Vera Pawlowsky-Glahn, Antonella Buccianti: Compositional Data Analysis: Theory and Applications, Chichester: John Wiley & Sons, Ltd, 2011, 9781119976462-1
    DOI: 10.1002/9781119976462
  • Book chapter
    Vera Pawlowsky-Glahn, Antonella Buchianti: Compositional Data Analysis: Theory and Applications, Chichester: John Wiley & Sons, Ltd, 2011, 9780470711354, 73-86

Publ.-Id: 17682 - Permalink


Influence of low (radio)metal concentrations on bacterial growth using calorimetric metabolic monitoring
Hassan Obeid, M.; Geissler, A.; Solioz, M.; Fahmy, K.; Oertel, J.;
Introduction: The transition of industrially caused metal contaminations into the food chain constitutes a serious risk for the environment and human health. It is particularly a major challenge to develop ecotoxicological biomonitors that provide a physical readout based on measurable metabolic effects rather than extrapolating risks from restricted physical and chemical environmental parameters that account for neither bioavailability nor metabolic responses to toxicity.

Objectives: We have studied bacterial growth by measuring metabolic heat using state ofthe art microcalorimetry to observe the effects of low doses of heavy (radio)metals on three different bacterial strains. Escherichia coli and Lactococcus lactis were used as genetically well defined test organisms and Peanibacillus sp. JG-TB8 as a natural isolate recovered from a soil sample of the uranium mining waste pile “Haberland” (Johanngeorgenstadt, Germany).

Material and Methods: Liquid cultures of Escherichia coli, Lactococcus lactis and Peanibacillus sp. JG-TB8 were exposed to micromolar concentrations of europium(III), copper(II) and uranium(VI) salts and the metabolic heat release was measured as a function of time and temperature using a thermal activity monitor (TAM-III, TA-instruments).

Results: Reproducible effects of europium and copper on the time dependent heat release are observed already at concentration of 10 µM. In contrast to europium and copper, for which the inhibitory action scales with concentration, uranium influences bacterial growth in a more complicated manner which strongly depends on temperature and pH, probably as a consequence of its different speciations. In contrast to conventional optical monitoring of cell growth, much more subtle effects, such as consecutive exponential growth phases can be distinguished.

Conclusions: The results demonstrate that microcalorimetric monitoring is an extremely sensitive tool to investigate the influence of low heavy metal and radionuclide concentrations on the metabolic activity of microorganisms. The bacterial growth rates were determined with high accuracy continuously in real time. The proven long-term stability will also allow the monitoring of higher living organisms (e.g. C. elegans).
Keywords: microcalorimetry metal stress
  • Contribution to proceedings
    Jahrestagungder Deutschen Gesellschaft für Biophysik, 23.-26.09.2012, Göttingen, Deutschland
  • Poster
    Jahrestagung der Deutschen Gesellschaft für Biophysik, 23.-26.09.2013, Göttingen, Germany

Publ.-Id: 17681 - Permalink


Comment on “A Conditional Dependence Adjusted Weights of Evidence Model” by Minfeng Deng in Natural Resources Research 18(2009), 249–258
Schaeben, H.; van den Boogaart, K. G.;
without abstract

Publ.-Id: 17680 - Permalink


Membrane nanodiscs: a platform for the structural and functional characterization of a bacterial PIB-type ATPase
Fischermeier, E.; Sayed, A.; Oertel, J.; Fahmy, K.;
Introduction:
Reconstitution of membrane proteins in a native-like lipidic environment is vital for the determination of their structural and functional properties. Nanodics (NDs) constitute such an environment by providing a planar nanoscale phospholipid bilayer bounded by a ring of two membrane scaffolding proteins (MSP). NDs are advantageous over liposomes and bicelles as they exhibit less scatter, are soluble and of defined size and can integrate membrane proteins as single molecules that are accessible from both sides. Here we show that NDs can be utilized to study the mechanism of PIB-type ATPases, a protein family pumping transition metals, e.g. copper, across biological membranes. Moreover, we explore the potential of ND for proposed single molecule structural studies using X-FEL radiation.

Objectives:
We want to explore the use of NDs as a biochemical platform for spectroscopic, biochemical and ultimately single molecule structural studies of membrane proteins, as for example the allosteric coupling between copper transport and ATP-hydrolysis in the PIB-type ATPase CopA from L. pneumophila.

Materials and Methods:
CopA and MSP1 were affinity-purified following recombinant expression in E. coli. Nanodiscs were reconstituted from a MSP : lipid : CopA (1:60:0.1) cholate-mixture after detergent removal and characterized by dynamic light scattering, AFM, CD spectroscopy and X-ray diffraction using X-FEL radiation.

Results:
MSP1 was purified and NDs were prepared with different lipid moieties. Thorough analyses by natural and magnetic CD as well as dynamic light scattering show a well defined and stable composition of NDs of an average diameter of 10nm. Preliminary x-ray diffraction data from NDs have been recorded using the X-FEL at SLAC, (USA).
After successfull purification of CopA from L. pneumophila, enzyme activity was tested by ATPase assays and spectroscopic techniques, followed by reconstitution into NDs for further biophysical investigation.

Conclusions: NDs provide a suitable platform for structural and functional studies of integral membrane proteins in a native-like lipidic environment. They offer the potential to apply functional assays under identical conditions as envisaged advanced x-ray diffraction experiments using pulsed r-ray sources. Here, we have established the functional reconstitution of the bacterial heavy-metal pump CopA into NDs to study structure–function relationships.
Keywords: membrane proteins copper transport X-FEL
  • Contribution to proceedings
    Jahrestagung der Deutschen Gesellschaft für Biophysik, 23.-26.09.2012, Göttingen, Deutschland
  • Poster
    Jahrestagung der Deutschen Gesellschaft für Biophysik, 23.-26.09.2013, Göttingen, Grmany

Publ.-Id: 17679 - Permalink


Spectroscopic characterization of transition metal complexes with quercetin in aqueous solutions
Attia, E.; Fahmy, K.;
Introduction: Flavonoids are ubiquitous polyphenolic compounds in fruits and vegetables, also referred as Vitamin P, which participate and redox reactions and influence the bioavailability of metals. Quercetin, one of the most abundant dietary flavonoids, has been shown to form a copper complex that binds to DNA and can cause strand cleavage.

Objectives: We want to determine the binding site of transition metals in flavonoids examplified for quercetin. The photreactivity of such complexes and their potential effect on DNA structure is investigated.

Material and methods: Quercetin (3,3’,4’,5,7pentahydroxylflavone) was purchased from SIGMA, salmon testes genomic DNA was from CALBIOCHEM. IR spectra of quercetin films were recorded by attenuated total reflectance (ATR) using a VECTOR 22 FTIR Spectrophotometer (BRUKER). CD spectra were measured with a JASCO 800 instrument.

Results:
The formation of copper–quercetin complexes was observed by the red shift of the quercetin absorption. Zn2+ showed low affinity in the mM range, whereas copper formed complexes already at nM concentratrions. In contrast to Zn, Cu2+ strongly quenches quercetin fluorescence, probably as a result of different ligand to metal charge transfer efficiencies. To address the complexation mode, IR-spectra were recorded from quercetin film is solution. The addition of transition metals affects a band at 1590 cm-1, typical of carbonyl stretching, suggesting that under our experimental conditions, coordination involves the C=O in position 4. Preliminary experiments show structural affects of the interaction of the complex with DNA.

Conclusions:
Copper-Quercetin complexes were synthesized in different solvents and the complex is stable under both aerobic and anaerobic conditions. The carbonyl at C4 of quercetin is the binding site for Cu2+ and affects photooxidative behaviour of the complex. Using ATR-technique highly hydrophbic flavonoids can be studied under fully hydrated conditions.
Keywords: infrared spectroscopy flavonoids
  • Poster
    Jahrestagung der Deutschen Gesellschaft für Biophysik, 23.-26.09.2013, Göttingen, Germany

Publ.-Id: 17678 - Permalink


Interpretation of a compositional time series
Tolosana-Delgado, R.; van den Boogaart, K. G.;
Common methods for multivariate time series analysis use linear operations, from the definition of a time-lagged covariance/correlation to the prediction of new outcomes. However, when the time series response is a composition (a vector of positive components showing the relative importance of a set of parts in a total, like percentages and proportions), then linear operations are afflicted of several problems. For instance, it has been long recognised that (auto/cross-)correlations between raw percentages are spurious, more dependent on which other components are being considered than on any natural link between the components of interest. Also, a long-term forecast of a composition in models with a linear trend will ultimately predict negative components.
In general terms, compositional data should not be treated in a raw scale, but after a log-ratio transformation (Aitchison, 1986: The statistical analysis of compositional data. Chapman and Hill). This is so because the information conveyed by a compositional data is relative, as stated in their definition. The principle of working in coordinates allows to apply any sort of multivariate analysis to a log-ratio transformed composition, as long as this transformation is invertible. This principle is of full application to time series analysis.
We will discuss how results (both auto/cross-correlation functions and predictions) can be back-transformed, viewed and interpreted in a meaningful way. One view is to use the exhaustive set of all possible pairwise log-ratios, which allows to express the results into D(D􀀀1)=2 separate, interpretable sets of one-dimensional models showing the behaviour of each possible pairwise log-ratios. Another view is the interpretation of estimated coefficients or correlations back-transformed in terms of compositions. These two views are compatible and complementary. These issues are illustrated with time series of seasonal precipitation patterns at different rain gauges of the USA. In this data set, the proportion of annual precipitation falling in winter, spring, summer and autumn is considered a 4-component time series. Three invertible log-ratios are defined for calculations, balancing rainfall in autumn vs. winter, in summer vs. spring, and in autumnwinter vs. springsummer. Results suggest a 2-year correlation range, and certain oscillatory behaviour in the last balance, which does not occur in the other two.
Keywords: Aitchison Simplex, compositional data analysis
  • Open Access LogoContribution to proceedings
    European Geosciences Union General Assembly 2012, 22.-27.04.2012, Wien, Österreich
    Geophysical Research Abstracts Vol. 14, EGU2012-8233: EGU General Assembly

Publ.-Id: 17676 - Permalink


Analyzing Compositional Data with R
van den Boogaart, K. G.; Tolosana-Delgado, R.;
Data describing amounts of components of specimens are compositional if the size of each specimen is constant, or irrelevant. Ideally compositional data is given by relative portions summing up to 1 or 100%. But more often compositional data appear disguised in several ways: different components might be reported in different physical units, different cases might sum up to different totals, and almost never all relevant components are reported. Nevertheless, the constraints of constant sum and relative meaning of the portions have important implications for their statistical analysis, contradicting the typical assumptions of usual uni- and multivariate statistical methods, and thus rendering their direct application spurious. A comprehensive statistical methodology, based on a vector space structure of the mathematical simplex, has only been developed very recently and several software packages are now available to treat compositional data within it. The book is at the same time a textbook on compositional data analysis from a modern perspective and a sort of manual on the R package “compositions”: both R and “compositions” are available for download as free software.
Keywords: Compositional Data Analysis, Aitchison Geometry
  • Book (Authorship)
    Heidelberg: Springer, 2013
    258 Seiten

Publ.-Id: 17675 - Permalink


The Research Group of Economic Geology at the TU Bergakademie Freiberg and the Helmholtz Institute Freiberg for Resource Technology (HIF)
Birtel, S.; Sandmann, D.; Seifert, T.; Gutzmer, J.;
Das Poster stellt die Themengebiete der Lagerstättenlehre der TUBAF und des HIF's und seine Rolle in der Forschungslandschaft dar
  • Poster
    EODI meeting, 30.-31.08.2012, Madrid, Spain

Publ.-Id: 17674 - Permalink


Flow measurements in a continuous casting model using a low temperature liquid metal
Timmel, K.; Röder, M.; Eckert, S.; Gerbeth, G.;
This paper describes experimental investigations of flow structures and related transport processes in the continuous casting mould under the influence of an external DC magnetic field at laboratory scale. Experimental results will be presented here which have been obtained using a physical model (mini-LIMMCAST) operating with the low melting point alloy GaInSn. The Ultrasound-Doppler-Velocimetry (UDV) was applied for measurements of the flow pattern in the mould. An array of ten transducers was attached to the narrow mould side, measuring the horizontal velocities in the the region around the liquid metal jet. Further, with two sensors on the mould top, vertical velocities were recorded successively in the whole mould width.
Keywords: continuous steel casting, liquid metal model, electromagnetic brake (EMBr)
  • Lecture (Conference)
    8th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 19.-21.09.2012, Dresden, Deutschland
  • Contribution to proceedings
    8th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 19.-21.09.2012, Dresden, Deutschland, 71-74

Publ.-Id: 17673 - Permalink


Bayes spaces: use of improper distributions and exponential families
Egozcue, J. J.; Pawlowsky-Glahn, V.; Tolosana-Delgado, R.; Ortego, M. I.; van den Boogaart, K. G.;
Bayes spaces are vector spaces of sigma-additive positive measures. Proportional measures are considered equivalent and can be represented by densities with respect to a fixed dominating measure. The addition in these spaces is perturbation. It corresponds to Bayes theorem, which appears as a linear operation. Bayes spaces, with continuous dominating measures, contain finite and infinite measures. Finite measures are equivalent to probability measures. Infinite measures include what in Bayesian statistics are called improper priors and non-integrable likelihood functions, justifying the use of such improper densities in Bayes theorem. Many concepts of probability theory can be handled in a natural way in the context of Bayes spaces. Particularly, an exponential family of probability densities appears as a cone contained in an affine subspace of the Bayes space. The framework of Bayes spaces allows an easy handling of exponential families and their extensions to improper distributions. Furthermore, the vector space structure of Bayes spaces allows the definition of derivatives of densities. In Bayesian statistics, these derivatives are a new tool to examine sensitivity of posterior distributions with respect to both observed data and prior changes.
Keywords: Simplex, Aitchison geometry, Derivative, Sensitivity
  • Revista de la Real Academia de Ciencias Exactas, Fisicas y Naturales. Serie A. Matematicas (2012)
    DOI: 10.1007/s13398-012-0082-6

Publ.-Id: 17672 - Permalink


Mineral potential mapping using Cox-type regression for marked point processes
van den Boogaart, K. G.; Schaeben, H.;
Mineral potential mapping infers the chance of finding a deposit at a location from geological covariables. Usual methods, like weights of evidence, fit a model for the occurrence probability of a deposit in a pixel to a dataset of pixels, where the all geological covariables and presence or absence of the deposit is known.

We propose a new more flexible approach, viewing the locations of deposits as an inhomogeneous marked point process. This allows to model intensity rather than probability. The local occurrence probability is computed from the fitted model. The variation of log intensity is described by a linear model in the covariables like in a Cox-regression model for survival analysis. Applied to similar data the approach gives results similar to the classical approaches.

However it additionally allows for the inclusion of continues covariables, the use of information on smaller uneconomical mineralisation zones as additional information for the model fit by introducing mark distributions, inclusion of incompletely explored areas by reweighting with the probability of finding, and the use of samples rather than complete maps for the region without deposit
using the spatial character of point processes.
Keywords: Weights of Evidence, Mining Exploration, Instationary Point Processes
  • Contribution to proceedings
    34th International Geological Congress, 05.-10.08.2012, Brisbane, Australia
    Proceedings of the 34th International Geological Congress, Canberra: australian Geoscience Council

Publ.-Id: 17671 - Permalink


The Sensitivity to Axial Alignment of a Flow Driven by a Travelling Magnetic Field
Pal, J.; Cramer, A.; Gerbeth, G.; Koal, K.; Tschisgale, S.; Siller, J.;
The present study, both experimentally and by numerical simulation, concerns the sensitivity of a flow that is driven by a travelling magnetic field (TMF) with respect to a stepwise applied mismatch between the axes of the TMF and of the cylindrical liquid metal column. The TMF is generated by six equidistantly arranged cylindrical coils powered with an AC current having a phase shift of 60° between them. Because the flow induced by a TMF is basically of a torus type, vertical velocity components are representative for the motion in the meridional plane. Ultrasound Doppler Velocimetry (UDV) was applied to acquire the velocity component along the beam axis in the centre of the liquid metal column and at various azimuthal positions for a fixed radial coordinate. The measurements are compared to the flow data gained by large eddy simulations. Computations were based on the usual approximations to simplify the magnetohydrodynamic equations, which are low frequency and low induction, and on an analytical expression for the Lorentz force considering the shift between the fluid volume and the field. The results show that even a small shift between the axes may result in a distinct three-dimensional constituent of the flow structure which changes completely the usually assumed axisymmetric torus-type flow.
Keywords: fluid flows; magnetic fields; TMF; stirring; flow measurements
  • Journal of Iron and Steel Research International 19(2012)1-1, 557-560
  • Lecture (Conference)
    7th International Conference on Electromagnetic Processing of Materials (EPM2012), 22.-26.10.2012, Bejing, China

Publ.-Id: 17670 - Permalink


Cloud Computing and Big Data in German Research Institutes
Konrad, U.;
Supercomputing and Big Data expand the spectrum of scientific studies, since they provide access to the understanding of phenomena of highest complexity in the area of the theories and models as well as for the analysis of experimental data. Since 2008 Cloud Computing has become another buzzword after Web 2.0. In the commercial area Cloud Computing hast already achieved an enormous significance. This plenary speech describes the fundamentals and the actual status of Big Data and Cloud Computing in the area of research in Europe.
Keywords: Information Technology, Supercomputing, Cloud Computing, Big Data
  • Invited lecture (Conferences)
    The 1st International Workshop for Young Scientists “Intelligent Technologies for Information Processing and Management”, 17.-19.07.2012, Ufa, Russia

Publ.-Id: 17669 - Permalink


Spectroscopic and Quantum Chemical Study of the Curium(III) and Europium(III) Citrate Speciation in Biological Systems
Heller, A.; Barkleit, A.; Foerstendorf, H.; Tsushima, S.; Heim, K.; Bernhard, G.;
Heavy metals, particularly radionuclides, represent a serious health risk to humans in case of incorpo-ration. For the understanding of their (radio-) toxicity, distribution, deposition and elimination, it is crucial to investigate their aqueous speciation and molecular transport mechanisms in biosystems. Unfortunately, only little is known about the behavior of artificial, radioactive trivalent actinides (An(III)) and naturally occurring, nonradioactive lanthanides (Ln(III)) in the human organism. Nevertheless, quite recently, we showed that citrate complexes are the dominant binding form of An(III) and Ln(III) in human urine at pH < 6. Hence, an accurate prediction of the speciation of these elements in the presence of citrate is crucial for the understanding of the impact on the metabolism of the human or-ganism and the corresponding health risks.
Therefore, we studied the complexation of Cm(III) and Eu(III), as representatives of An(III) and Ln(III), respectively, in aqueous citrate solution over a wide pH range using a combined approach of Time-Resolved Laser-induced Fluorescence Spectroscopy (TRLFS), Fourier-Transform Infrared Spectroscopy with Attenuated Total Reflection (ATR FT IR) and density functional theory (DFT) calculations.
With TRLFS, four citrate complexes were identified for both Cm(III) and Eu(III), which are MHCit0, M(HCitH)HCit 2-, M(HCit)2 3-, and M(Cit)2 5-. Furthermore, the stability constants were determined. Additionally, there were also indications for the formation of MCit- complexes.
With ATR FT IR and DFT, structural details of the EuHCit and EuCit- complexes were obtained. The combination of both methods gave clear evidence for the deprotonation of the hydroxyl group of the citrate ion in the EuCit- complex, what also revealed that the complexation of the Eu 3+ ion takes place not only through the carboxylate groups, like in EuCit0, but additionally via the hydroxylate group. In both EuCit0 and EuCit- the carboxylate binding mode is predominantly mono-dentate.
Under very low metal to citrate ratio that is typical for human body fluids, the Cm(III) and Eu(III) speciation was found to be strongly pH-dependent. The Cm(III) and Eu(III) citrate complexes domi-nant in human urine at pH < 6 were identified to be Cm(HCitH)HCit2- and a mixture of Eu(HCitH)HCit 2- and EuHCit0. The results specify our previous in vitro study using natural human urine samples and point out the importance of low molecular weight ligands for An(III) and Ln(III) complexation in body fluids and other biological systems.
Keywords: actinides, lanthanides, speciation, spectroscopy, biofluids, citrate
  • Contribution to proceedings
    Advanced Techniques in Actinide Spectroscopy (ATAS), 05.-07.11.2012, Dresden, Deutschland
    Abstract book
  • Lecture (Conference)
    Advanced Techniques in Actinide Spectroscopy (ATAS), 05.-07.11.2012, Dresden, Deutschland

Publ.-Id: 17668 - Permalink


Reaktionsaufklärung und Einzelkanalstudien am Beispiel der Oxidation von Isobutan zu tert-Butyl-Hydroperoxid
Willms, T.; Kryk, H.; Hampel, U.;
Die Aufgaben des Arbeitspaketes 2.5 des Projektes „Energieeffiziente chemische Mehrphasenprozesse“ werden kurz vorgestellt. Nach der Vorstellung der am HZDR zur Reaktionsaufklärung verfügbaren apparativen Ausstattung wird das Potential der Energieeffizienzverbesserung der Oxidation von Isobutan mit Sauerstoff zu tert.-Butylhydroperoxid angesichts der Technologie mikrostrukturierter Reaktoren evaluiert. Ein vereinfachter Mechanismus der Reaktion wird angegeben. Darauf aufbauend wird das weitere Vorgehen zur Reaktionsaufklärung im Rahmen des Projekts skizziert, sowie die Verknüpfungen des Arbeitspaketes 2.5 mit anderen Arbeitspaketen aufgezeigt.
  • Lecture (others)
    Offizielles Kick-off-Meeting zur Helmholtz-Energie-Allianz "Energieeffiziente chemische Mehrphasenprozesse", 30.07.2012, Dresden, Deutschland

Publ.-Id: 17667 - Permalink


Extreme High-Rate Capable Timing Resistive Plate Chambers with Ceramic Electrodes
Garcia, L. A.; Kaspar, M.; Kämpfer, B.; Kotte, R.; Naumann, L.; Peschke, R.; Stach, D.; Wendisch, C.; Wüstenfeld, J.;
The future Compressed Baryonic Matter experiment to be built at the Facility for Antiproton and Ion Research in Darmstadt, Germany, will create the highest particle densities ever created in a laboratory. One of its components, the Time-of-Flight Wall, will be comprised of Resistive Plate Chambers. The high particle fluxes expected at the most inner region, close to the beam pipe, have led to the research of new low-resistive materials to be used as electrodes. Si3N4/SiC composites are a very good candidate for this function. Their bulk resistivity, in the order of 109–1010 Ω cm, allows for increased rate capabilities up to 106 s−1 cm−2. In this report, the properties of these new materials will be discussed. Also, the performance of resistive plate chambers with ceramic electrodes under irradiation in electron and proton beams will be presented.

Publ.-Id: 17665 - Permalink


Implementation of specific-heat and NMR experiments in the 1500 ms long-pulse magnet at the Hochfeld-Magnetlabor Dresden
Weickert, F.; Meier, B.; Zherlitsyn, S.; Herrmannsdörfer, T.; Daou, R.; Nicklas, M.; Haase, J.; Steglich, F.; Wosnitza, J.;
We report on the design and successful testing (up to 55 T) of a 60 T long-pulse (LP) magnet with a pulse duration of 1500 ms at the Hochfeld-Magnetlabor Dresden. This magnet has the capability of producing magnetic fields with time and homogeneity characteristics suitable to host specific-heat and nuclear magnetic resonance (NMR) experiments. We describe the development of a specific-heat probe for this magnet, which uses the quasi-adiabatic heat-pulse method and enables magnetocaloric-effect measurements. Furthermore, we report the implementation of a NMR setup, consisting of home-built probe and spectrometer. Both experimental devices were tested successfully in the LP magnet up to 31 and 44 T, respectively.

Publ.-Id: 17664 - Permalink


Ultrasonic flow measurements in a downscaled water mockup of a large scale precession driven dynamo experiment
Gundrum, T.; Stefani, F.; Ma, C.; Sun, Y.; Giesecke, A.; Albrecht, T.; Gerbeth, G.;
The DREsden Sodium facility for DYNamo and thermohydraulic studies (DRESDYN) is planned to become a platform both for large scale experiments related to geo- and astrophysics as well as for experiments on thermo-hydraulic and safety aspects of liquid metal applications in energy related technologies. The most ambitious project in the framework of DRESDYN is a homogeneous hydromagnetic dynamo driven solely by precession. The detailed knowledge of the flow structure in the precessing cylindrical vessel is of key importance for the prediction of the dynamo action. In this paper we present UDV measurements of the velocity field in a 1:6 downscaled water mock-up.
Keywords: Ultrasound Doppler Velocimetry, Precession, Dynamo
  • Open Access LogoContribution to proceedings
    8th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 19.-21.09.2012, Dresden, Germany
    Proceedings of the 8th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, Dresden: HZDR, 23-26

Publ.-Id: 17663 - Permalink


Fermi-surface evolution in Yb-substituted CeCoIn5
Polyakov, A.; Ignatchik, O.; Bergk, B.; Götze, K.; Bianchi, A. D.; Blackburn, S.; Prevost, B.; Seyfarth, G.; Coté, M.; Hurt, D.; Capan, C.; Fisk, Z.; Goodrich, R. G.; Sheikin, I.; Richter, M.; Wosnitza, J.;
We report results of systematic de Haas–van Alphen (dHvA) studies on Ce1−xYbxCoIn5 single crystals with varyingYb concentration. For x = 0.1, the well-known Fermi surfaces and the heavy effective masses of CeCoIn5 (x = 0) have changed only slightly.We start to observe changes of the Fermi-surface topology at x = 0.2 leading to a drastic reconstruction above x = 0.55. At these concentrations, the effective masses are reduced considerably to values between 0.7 and 2.6 free electron masses. For both YbCoIn5 and CeCoIn5, the angular-resolved dHvA frequencies can be very well described by conventional density-functional theory calculations. Projection of the Bloch states onto atomic Yb-4f orbitals yields a 4f occupation of 13.7 electrons, in agreement with previous experimental results indicating an intermediate Yb valence of +2.3.

Publ.-Id: 17662 - Permalink


Critical fields and growth rates of the Tayler instability as probed by a columnar gallium experiment
Rüdiger, G.; Gellert, M.; Schultz, M.; Strassmeier, K. G.; Stefani, F.; Gundrum, T.; Seilmayer, M.; Gerbeth, G.;
Many astrophysical phenomena (such as the slow rotation of neutron stars or the rigid rotation of the solar core) can be explained by the action of the Tayler instability of toroidal magnetic fields in the radiative zones of stars. In order to place the theory of this instability on a safe fundament, it has been realized in a laboratory experiment measuring the critical field strength, the growth rates, as well as the shape of the supercritical modes. A strong electrical current flows through a liquid metal confined in a resting columnar container with an insulating outer cylinder. As the very small magnetic Prandtl number of the gallium–indium–tin alloy does not influence the critical Hartmann number of the field amplitudes, the electric currents for marginal instability can also be computed with direct numerical simulations. The results of this theoretical concept are confirmed by the experiment. Also the predicted growth rates on the order of minutes for the nonaxisymmetric perturbations are certified by the measurements. That they do not directly depend on the size of the experiment is shown as a consequence of the weakness of the applied fields and the absence of rotation.
Keywords: magnetohydrodynamics (MHD) – stars: magnetic field – stars: rotation

Publ.-Id: 17661 - Permalink


Identification of hexanuclear Actinide(IV) carboxylates with Thorium, Uranium and Neptunium by EXAFS spectroscopy
Hennig, C.; Takao, S.; Takao, K.; Weiss, S.; Kraus, W.; Emmerling, F.; Meyer, M.; Scheinost, A. C.;
Hydrated actinide(IV) ions undergo hydrolysis and further polymerization and precipitation with increasing pH. The resulting amorphous and partly crystalline oxydydroxides AnOn(OH)4−2nxH2O can usually be observed as colloids above the An(IV) solubility limit. The aging process of such colloids results in crystalline AnO2. The presence of carboxylates in the solution prevents the occurrence of such colloids by formation of polynuclear complexes through a competing reaction between hydrolysis and ligation. The majority of recently described carboxylates reveals a hexanuclear core of [An6(μ3-O)4(μ3-OH)4]12+ terminated by 12 carboxylate ligands. We found that the An(IV) carboxylate solution species remain often preserved in crystalline state. The An(IV) carboxylates show An-An distances which are ~ 0.03 Å shorter than the An-An distances in AnO2 like colloids. The difference in the distances could be used to identify such species in solution.
Keywords: EXAFS, Actinides, Carboxylates

Publ.-Id: 17660 - Permalink


Experimental Investigations on Vertical Pipe Flow Using Ultrafast Electron-Beam X-Ray Tomography
Banowski, M.; Lucas, D.; Hoppe, D.; Barthel, F.; Szalinski, L.; Sprewitz, U.; Beyer, M.; Hampel, U.;
This presentation introduces into the tomography measurement system and the vertical pipe test facility for liquid-gas experiments at TOPFLOW. The reconstruction and data evaluation algorithms are discussed shortly. Some results of two-phase upward flow experimental series for air-water and steam-water flow regimes are showed with qualitative and quantitative data. Finally limits and errors of this measurement technique are presented.
Keywords: two-phase, measuring technique, X-ray, tomography, pipe flow, bubble
  • Lecture (Conference)
    10th Multiphase Flow Conference: Simulation, Experiment and Application, 13.-14.06.2012, Dresden, Deutschland
  • Contribution to proceedings
    10th Multiphase Flow Conference: Simulation, Experiment and Application, 13.-14.06.2012, Dresden, Deutschland
    CD-ROM

Publ.-Id: 17659 - Permalink


High temperature diffusion processes at the metal/slag interface
Bogusz, A.; Masset, P. J.;
The interface metal/molten oxide is of interest for several high temperature processes (metallurgy, gasification…). The exchange reactions occurring at the interface between the metal and the molten slag are complex and up to date not well understood. More generally, this is of importance for the understanding of the exchange reaction kinetics between one metallic compound (solid or liquid) and an ionic one (slag). This work proposes a theoretical approach which takes into account the effect of speciation in the slag on the diffusion process of the species in the two phases and the redox reaction occurring within the vicinity of the interface. The systems investigated consist of Fe and CaO-SiO2 without convection. The concentration profiles of silicon and iron oxide in both parts were calculated. The effect of impurities present in metal phase such as sulphur in the molten slag was investigated. This provides a basis of comprehensive approach for the purification of metal and a better understanding of processes at metal/oxide interface.
Keywords: Diffusion, Mass exchange, Electrochemical reactions, Metal/slag interface

Publ.-Id: 17658 - Permalink


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