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41420 Publications

Origin of the ferromagnetism in defective TiO2 single crystals

Zhou, S.; Cizmar, E.; Potzger, K.; Krause, M.; Talut, G.; Helm, M.; Fassbender, J.; Zvyagin, S. A.; Wosnitza, J.; Schmidt, H.

In this paper we show that ferromagnetism can be induced in pure TiO2 single crystals by oxygen ion irradiation. By combining x-ray diffraction, Raman-scattering, and electron spin resonance spectroscopy, a defect complex, Ti^{3+} ions on the substitutional sites accompanied by oxygen vacancies, has been identified in irradiated TiO2. This kind of defect complex results in a lattice strain and a local (TiO_{6-x}) stretching Raman mode. We elucidate that Ti^{3+} ions with one unpaired 3d electron provide the local magnetic moments.

Keywords: TiO2; Induced ferromagnetism; Defects; ESR

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Permalink: https://www.hzdr.de/publications/Publ-11876
Publ.-Id: 11876


Room temperature ferromagnetism in carbon-implanted ZnO

Zhou, S.; Xu, Q.; Potzger, K.; Talut, G.; Fassbender, J.; Vinnichenko, M.; Grenzer, J.; Helm, M.; Hochmuth, H.; Lorenz, M.; Grundmann, M.; Schmidt, H.

Unexpected ferromagnetism has been observed in carbon doped ZnO films grown by pulsed laser deposition [Phys. Rev. Lett. 99, 127201 (2007)]. In this letter, we introduce carbon into ZnO films by ion implantation. Room temperature ferromagnetism has been observed. Our analysis demonstrates that (1) C-doped ferromagnetic ZnO can be achieved by an alternative method, i.e. ion implantation, and (2) the chemical involvement of carbon in the ferromagnetism is indirectly proven.

Keywords: ZnO; Diluted magnetic semiconductor; Carbon; ion implantation

  • Applied Physics Letters 93(2008), 232507
    DOI: 10.1063/1.3048076
    Cited 211 times in Scopus
  • Lecture (Conference)
    DPG Frühjahrstagung der Sektion Kondensierte Materie (SKM) 2009, 22.-27.03.2009, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-11875
Publ.-Id: 11875


Inverse spinel ZnFe2O4 nanoparticles synthesized by ion implantation and post-annealing: an investigation using X-ray spectroscopy and magneto-transport

Zhou, S.; Potzger, K.; Buerger, D.; Kuepper, K.; Helm, M.; Fassbender, J.; Schmidt, H.

Noncrystalline ZnFe2O4 has been investigated intensively due to the drastic difference in cation distribution compared with bulk materials. We previously synthesized ZnFe2O4 nanoparticles by ion implantation and post-annealing [J. Phys. D-Appl. Phys. 40, (2007) 964]. These ZnFe2O4 nanocrystals are crystallographically oriented inside the ZnO matrix and show a hysteretic behavior upon magnetization reversal at 5 K. Their magnetic properties are explained by assuming that Fe^{3+} ions partially occupy tetrahedral sites. In this paper an X-ray spectroscopic and magneto-transport investigation on ZnFe2O4 nanocrystals in a ZnO matrix will be presented. The occupation of Fe^{3+} at tetrahedral sites has been directly proved. A positive magnetoresistance (MR) effect is observed and is attributed to ordinary MR.

Keywords: ZnFe2O4; X-ray absorption; Magnetoresistance

Permalink: https://www.hzdr.de/publications/Publ-11874
Publ.-Id: 11874


Sorption of uranium(VI) onto opalinus clay in absence and presence of humic acid

Joseph, C.

An anaerobic opalinus clay sample was characterized (BET, TC, TOC, CEC, XRD, IR). No significant differences between the aerobic and the anaerobic clay could be determined.
For the uranium(VI) sorption onto kaolinite the effect of the background electrolyte was investigated. An explanation for the different results is given by EQ3/6-speciation diagrams. The uranium(VI) sorption onto aerobic opalinus clay (S/L = 60 g/l) in opalinus clay pore water in absence and presence of humic acid was investigated and compared with the according uranium(VI)-humic acid-kaolinite sorption results.

Keywords: opalinus clay; characterization; anaerobic; sorption; uranium(VI); speciation; humic acid; kaolinite

  • Lecture (others)
    Meeting FZD - PSI, 03.-04.11.2008, Rossendorf, Germany

Permalink: https://www.hzdr.de/publications/Publ-11873
Publ.-Id: 11873


Spectroscopic investigations of U(VI) speciation In cementitious materials

Macé, N.; Wieland, E.; Tits, J.; Dähn, R.; Kunz, D.; Geipel, G.; Scheinost, A. C.

In the Swiss radioactive waste management program, cement is used as a matrix for long-lived intermediate-level waste (ILW), in which Uranium is an important radionuclide. Calcium Silicate Hydrates (C-S-H) are one of the major components of Hardened Cement Paste (HCP). A molecular-level understanding of Uranium uptake processes occurring in cementitious materials is essential to improve long-term predictions in safety analysis. U(VI) uptake by C-S-H (CaO/SiO2 = 1.07) in Artificial Cement pore-Water (ACW) and HCP has been investigated using Time Resolved Laser Fluorescence Spectroscopy (TRLFS) and X-Ray Absorption Spectroscopy (XAS) in order to determine the chemical environment of retained and precipitated U(VI) species in cementitious matrices. Phase X (CaUO4(H2O)x) soddyite and a uranophane (Ca(H3O)2 have been chosen as relevant reference compounds.
The main results are:
1) Preliminary TRLFS and XAS results are in a good agreement concerning U(VI) speciation in cementitious systems
2) TRLFS spectra of U(VI) in supernatant ≠ TRLFS spectra of U(VI) in cementitious pastes, i.e. free U(VI) species in ACW ≠ sorbed U(VI) species in cementitious pastes
3) TRLFS and XAS spectra of U(VI) sorbed species in HCP and C-S-H pastes are similar, i.e. C-S-H phases are responsible of U(VI) immobilization in HCP
4) For U(VI) high loading in HCP and U(VI) precipitated in ACW, i.e. U(VI) environment closed to a Ca-uranate phase with long U-Oaxial distances (1.86 ± 0.02) Ǻ
5) For U(VI) low loadings in HCP and C-S-H in ACW, i.e. uranophane-like structure with short UOaxial distances (1.83 ± 0.02) Ǻ

Keywords: cement; nuclear waste; uranium; TRLFS; EXAFS

  • Poster
    Cement08 - 2nd International workshop on Mechanism and Modelling of waste/cement interaction, 12.-16.10.2008, Le Croisic, France

Permalink: https://www.hzdr.de/publications/Publ-11872
Publ.-Id: 11872


eta and eta-prime production in nucleon-nucleon collisions near thresholds

Kaptari, L. P.; Kämpfer, B.

The production of eta and eta-prime mesons in nucleon-nucleon collisions near thresholds is considered within a one-boson exchange model. We show the feasibility of an experimental access to transition formfactors.

Permalink: https://www.hzdr.de/publications/Publ-11871
Publ.-Id: 11871


Fracture mechanics characterization of Russian WWER type reactor pressure vessel welding seams

Viehrig, H.-W.; Schuhknecht, J.

The paper is focussed on Master Curve testing according to ASTM E1921-05 [5] of the Russian WWER-440 type reactor pressure vessel steel. Charpy size SE(B) specimens from the beltline welding seam SN0.1.4 of the Greifswald NPP Unit 1 (1st generation WWER-440/V-230) and Unit 2 (2nd generation WWER-440/V213) were investigated in this study. The specimens are TL and TS oriented in the RPV welding seam, this means specimen axis axial to the RPV wall and crack propagation circumferential and through the thickness, respectively. The WWER-440 welding seam consists of a welding root welded with an unalloyed wire Sv-08A and the filling material welded with the alloyed wire Sv-10KhMFT. Fracture toughness values at brittle failure, KJc, measured on Charpy size SE(B) specimens were evaluated following Master Curve analyses as specified in ASTM E1921-05. The results show a wavelike course of the evaluated reference temperature, T0, through the thickness of the welding seams of Unit 1 and Unit 8. The scatter is more pronounced for the irradiated annealed and reirradiated 1st generation RPV of Unit 1.
Another issue was the influence of the specimen orientation and mainly the crack extension direction. While the crack front of a TS specimen is located in a more or less uniform structure, the structure along the crack front of a TL specimen varies, because it usually spans several welding beads. Roughly speaking, TS and TL specimens have a differentiating and integrating behaviour, respectively. A difference in T0 was found also for TS and TL oriented specimens of Unit 8. The lowest T0 was measured on TS specimens from the welding root with 114°C, whereas TL specimens of the same thickness locations gave 62°C.
For the 2nd generation RPV of Unit 8, the KJc values measured on specimens of both orientations generally follow the course of the Master Curve and are enveloped by the fracture toughness curves for 2% and 98% fracture probability. This statement can generally be made also for the first generation RPV of Unit 1, but the scatter of the KJc values is larger compared to the Unit 8 RPV. More values than expected lie below the 2% fractile.
The reason for the scatter in the KJc values and T0 is found in the structure at and along the crack tip, which depends on the welding technology and the specimen orientation. The welding technology applied on the beltline welding seams of the 1st and 2nd WWER-440 RPV generation is different, which is clearly visible in macroscopic section in Figs. 3 and 4. KJc values measured on SE(B) specimens from the thickness locations beyond the welding root of Unit 8 RPV result in a valid T0. KJc values from specimens of the same thickness within the welding seam of Unit 1 show a larger scatter. The majority of KJc values from one thickness location falls below the fracture toughness curve for 2% fracture probability. The reason is seen in the brittle zone in the fusion region between two welding beads. The application of the SINTAP MC extension procedure leads to a conservative T0.
In comparison to the correlative and indirect approach of the fracture toughness estimation in the present codes, the results presented here show that the orientation of the surveillance specimens is crucial for the direct measurement of the fracture toughness. For fracture toughness determinations the specimen orientation should be chosen which either yields the most conservative fracture toughness values or which agrees with the loading and crack extension direction considered in the integrity assessment.

Keywords: reactor pressure vessel; multilayer welding seam; SE(B) specimen; specimen orientation; fracture toughness; Master Curve approach

  • Contribution to proceedings
    12th International Conference on Fracture, 12.-17.07.2009, Ottawa, Kanada
    Proceedings of the 12th International Conference on Fracture
  • Lecture (Conference)
    12th International Conference on Fracture, 12.-17.07.2009, Ottawa, Kanada

Permalink: https://www.hzdr.de/publications/Publ-11870
Publ.-Id: 11870


Photon data shed new light upon the GDR spreading width in heavy nuclei

Junghans, A. R.; Rusev, G.; Schwengner, R.; Wagner, A.; Grosse, E.

A global study of the electric dipole strength in and below the isovector giant dipole resonance (GDR) is presented for mass numbers A>80. It relies on the recently established remarkably good match between data for the nuclear photo effect to novel photon scattering data covering the region below the neutron emission threshold as well as by average resonance neutron capture (ARC). From the wide energy coverage of these data the correlation of the GDR spreading width with energy can be studied with remarkable accuracy. A clear sensitivity to details of the nuclear shape, i.e. the beta- and gamma-deformations, is demonstrated. Based hereon a new parameterization of the energy dependence of the nuclear electric-dipole strength is proposed which - with only two new parameters - allows to describe the dipole strength in all heavy nuclei with A>80. Although it differs significantly from previous parameterizations it holds for spherical, transitional, triaxial and well deformed nuclei. The GDR spreading width depends in a regular way on the respective resonance energy, but it is independent of the photon energy.

Keywords: Isovector giant dipole resonance; E1 strength function; Lorentzian; Spreading width

Permalink: https://www.hzdr.de/publications/Publ-11869
Publ.-Id: 11869


The properties of the nanometer thick Si/Ge films-on-insulator produced by Ge+ ion implantation and subsequent hydrogen transfer

Tyschenko, I. E.; Voelskow, M.; Cherkov, A. G.; Popov, V. P.

The behaviour of germanium implanted into the SiO2 layers in the vicinity of the bonding interface of silicon-on-insulator (SOI) structures has been studied. The enhanced segregation of the implanted Ge atoms at the Si/SiO2 bonding interface has been observed. Segregated Ge atoms form the layer, which is coherent with the silicon lattice. It is suggested that the formation of intermediate Ge layer is mediated by the occurrence of liquid Ge phase. The effect of Ge on the Hall mobility of holes in the 25 nm thick SOI layer was studied. An increase in the hole mobility by a factor of three was obtained in the SiGe-on insulator structures in comparison with that measured in the respective Ge-free SOI films.

Keywords: SiGe on insulators

  • Physica Status Solidi (C) 5(2008)12, 3724-3727

Permalink: https://www.hzdr.de/publications/Publ-11868
Publ.-Id: 11868


Influence of the transition metal affinity on the encapsulating carbon medium during the growth of carbon:transition metal nanocomposite films

Berndt, M.; Krause, M.; Abrasonis, G.; Mücklich, A.; Munnik, F.; Kolitsch, A.; Möller, W.

The understanding of the interactions of carbon (C) atoms with transition metals (TM) is of particular importance as these interactions are involved in many processes in nanoscience. However, the underlying fundamental mechanisms are still not well understood. In this work, the influence of the TM chemical affinity to C on the encapsulating carbon nanostructuring is studied during the growth of C:TM nanocomposite films. C:Co and C:V nanocomposites with metal content of ~ 15 and ~ 30 at.% have been grown by ion beam co-sputtering in the temperature range of RT-500°C. The so-grown films have been investigated by the means of elastic recoil detection analysis, X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman spectroscopy at two excitation wavelengths (532 nm and 785 nm). In order to highlight the influence of the transition metal on the encapsulating matrix, the results are compared with the pure carbon films deposited at the same temperatures.

Nanocomposite structure is observed for all the C:TM films which consists of metal (or metal carbide) nanograins embedded in carbon medium. The C:V films consist of spherical grains of the diameter of ~2 nm whose size or shape is independent of the growth temperature. Vanadium is in the carbidic state over the whole temperature range of this study. The Co nanoparticles in C:Co films grown at RT also exhibit a spherical shape with a diameter of ~ 2 nm. However, with increasing deposition temperature the Co nanoparticles become elongated the long axis coinciding with the direction of the film growth. A carbide phase is identified for growth temperatures of RT-300°C, while a metallic phase is formed above 300°C.

The embedding carbon phase resembles that of the amorphous carbon at lower growth temperatures, while at elevated growth temperatures (>= 300°C) curved graphenic sheets encapsulating the metal nanoparticles can be identified. Raman spectroscopy shows that both metals enhance 6-fold ring clustering of the carbon phase since the D peak intensity related to the 6-fold ring breathing vibrations is increased in comparison to the pure carbon films. This enhancement occurs independently on the nanoparticle type, size, shape and phase. Besides the D and G peak, a third peak at ~ 1100 cm-1 is identified, which shows a resonance enhancement for visible laser excitation. This peak is absent in pure carbon films. Its intensity in relation to D-G band decreases when the growth temperature increases, while it increases concomitantly with the metal content. Moreover, the position of this peak is independent on the metal type indicating that it is an inherent feature of carbon.

Keywords: composites; ion beam sputtering; metallic and carbon nanostructures

  • Poster
    XXIInd International Winterschool on Electronic Properties of Novel Materials, 01.-08.03.2008, Kirchberg, Austria

Permalink: https://www.hzdr.de/publications/Publ-11867
Publ.-Id: 11867


Morphology, structure and growth pathways of carbon:transition metal nanocomposite thin films prepared by Ion beam co-sputtering

Krause, M.; Abrasonis, G.; Berndt, M.; Mücklich, A.; Munnik, F.; Kolitsch, A.; Möller, W.

Nanocomposites (NC) represent a new class of composite materials, wherein at least one component has a size of =< 100 nm in one dimension. [1] They are expected to show improved properties compared to classical materials and conventional composites due to their higher number of interfaces and their smaller particle size. In this work ion beam co-sputtering (IBS) of carbon and the 3d metals V, Co, Ni, and Cu was used to prepare NC thin films. Stable and homogenous NC with good adhesion on silicon were obtained for all the metals in a composition range of 15 at.% to 40 at.% metal, although the stability of the corresponding metal carbides gets smaller from vanadium to copper.
The NC morphology and structure was investigated by transmission electron microscopy, x-ray diffraction, x-ray absorption and Raman spectroscopy. In general, the NC consisted of nanoparticles embedded in a carbon matrix. Depending on the growth parameters, i.e. the chemical nature of the metal and the deposition temperature, the NC morphology could be varied from spherical grains via ellipsoidal nanocrystals to vertical standing columns extending over the whole thickness of the thin films. The phase properties of the nanoparticles resembled those of the bulk phases. While VC was formed in the temperature range of RT-500°C and no carbide phase at all was obtained for copper, cobalt and nickel exhibited either carbidic or metallic nanoparticles. Independently of the metal type the surrounding carbon phase exhibits an enhanced 6-fold aromatic ring formation compared to pure carbon reference films grown at identical conditions. The enhancement is particularly strong for low growth temperatures. While the carbon phase in general consists of a superposition of nanocrystalline graphite and amorphous carbon, the degree of graphitization could be controlled by the incorporated metal and the growth temperature. The results indicate that phase stability, nucleation rate and surface diffusivity determine the growth pathway of carbon:transition metal NC thin films grown by IBS. [2]-[5]

[1] P. M. Ajayan, L.S. Schadler, P.V. Braun, Nanocomposite Science and Technology, Wiley-VCH, 2003
[2] G. Abrasonis, M. Krause, A. Mücklich, K. Sedlackova, G. Radnoczi, U. Kreissig, A. Kolitsch, W. Möller, Carbon, 45, 2995-3006 (2007)
[3] M. Krause, G. Abrasonis, A. Kolitsch, A. Mücklich, U. Kreissig, W. Möller, Phys. Stat. Sol. (B), 244, 4236-4239 (2007)
[4] G. Abrasonis, A. Scheinost, S. Zhou, R. Torres, R. Gago, I. Jimenez, K. Kuepper, K. Potzger, M. Krause, A. Kolitsch, W. Möller, S. Bartkowski, M. Neumann, R. Gareev, J. Phys. Chem. C, 112, 12628-12637 (2008)
[5] G. Abrasonis, M. Berndt, M. Krause, K. Kuepper, F. Munnik, A. Kolitsch, W. Möller, J. Phys. Chem. C, in press, 2008

Keywords: Composites; Ion beam sputtering; growth; structure

  • Invited lecture (Conferences)
    SIWAN 2008 - 4th Szeged International Workshop on Advances in Nanoscience, 09.-10.10.2008, Szeged, Hungary

Permalink: https://www.hzdr.de/publications/Publ-11866
Publ.-Id: 11866


Advanced measuring techniques for multiphase flow at Research Center Dresden-Rossendorf

Da Silva, M. J.

Multiphase flow, the simultaneous stream in a pipe or vessel of two or more physically distinct and immiscible substances, is present in many industry branches. The correct understanding and modeling of such flows is a key issue for safety and efficiency aspects of processes and plants where they occur. In this presentation, state-of-the-art measuring techniques for investigation of multiphase flows are presented which have been developed or are under investigation at Research Center Dresden-Rossendorf. Special focus has been given to imaging techniques which are able to resolve phase distributions at high temporal and spatial resolution, including different types of wire-mesh sensors, gamma ray tomography and ultra fast electron beam tomography. Furthermore, the application of such techniques in basic research as well as industrial applications is presented and discussed.

Keywords: Multiphase flow; imaging techniques; wire-mesh sensor; tomography

  • Invited lecture (Conferences)
    Research Seminar, Engineering School of Sao Carlos, Department of Mechanical Engineering, Universidade de Sao Paulo, 08.10.2008, Sao Carlos, Brazil

Permalink: https://www.hzdr.de/publications/Publ-11865
Publ.-Id: 11865


Rare-Earth Implanted MOS Devices for Silicon Photonics

Rebohle, L.; Skorupa, W.

The book concentrates on the microstructural, electric and optoelectronic properties of rare earth implanted MOS structures and their use as light emitters in potential applications. It describes the structural formation processes in the gate oxide during fabrication and under operation, how this microstructure development will affect the electrical device performance and how both microstructure and electrical characteristics determine the optoelectronic features of the light emitters. However, most of the discussed physical processes as well as the described fabrication methods and device characterization techniques are of general interest and are beyond the scope of this type of light emitter. The book will be of value to engineers, physicists, and scientists dealing either with Si based photonics in particular or optoelectronic device fabrication and characterization in general.

Keywords: Si-based light emission; Electroluminescence; Rare earth implantation; MOS technology; Nanocluster formation

Related publications

  • Book (Authorship)
    Heidelberg: Springer, 2010
    173 Seiten

Permalink: https://www.hzdr.de/publications/Publ-11864
Publ.-Id: 11864


Coexisting stochastic and coherence resonance in a mean-field dynamo model for Earth's magnetic field reversals

Fischer, M.; Stefani, F.; Gerbeth, G.

Using a spherical symmetric mean-field alpha^2-dynamo model for Earth's magnetic field reversals, we show the coexistence of the noise-induced phenomena coherence resonance and stochastic resonance. Stochastic resonance was recently invoked to explain the 100 kyr periodicity in the distribution of residence times between reversals. The comparison of the resulting residence time distribution with the paleomagnetic one allows for some estimate of the effective diffusion time of the Earth's core which may be 100 kyr or slightly below rather than 200 kyr as it would result from the molecular resistivity.

Permalink: https://www.hzdr.de/publications/Publ-11863
Publ.-Id: 11863


Excitation hierarchy in the BEC candidate DTN

Zvyagin, S. A.; Wosnitza, J.; Kolezhuk, A. K.; Batista, C. D.; Kawashima, N.; Tsukamoto, M.; Zapf, V. S.; Jaime, M.; Paduan-Filho, A.; Krzystek, J.; Glazkov, V. N.; Sosin, S. S.; Smirnov, A. I.

NiCl2-4SC(NH2)2 (known as DTN) is a quantum S = 1 chain system with strong easyplane anisotropy that is regarded as a new candidate for the Bose-Einstein condensation (BEC) of spin degrees of freedom, with critical fields Bc1 = 2.1 T and Bc2 = 12.6 T. Tuneable-frequency Electron Spin Resonance (ESR) studies of magnetic excitations in DTN in fields up to 25 T are presented. Based on analysis of the single-magnon excitation mode observed in the high-field spin-polarized phase1 and previous experimental results2, a revised set of spin-Hamiltonian parameters is obtained. Our results yield D = 8.9 K, Jc = 2.2 K, and Ja,b = 0.18 K for the anisotropy, intrachain, and interchain exchange interactions, respectively. These values are used to calculate the antiferromagnetic phase boundary, magnetization and the frequency-field dependence of two-magnon bound-state excitations predicted by theory3 and observed in DTN for the first time. Furthermore, we present a systematic study of the low-energy excitation spectrum of DTN in the fieldinduced magnetically ordered phase (which is regarded as the magnon BEC phase) at temperatures down to 0.45 K. We argue that two gapped modes observed in the experiment4 can be consistently interpreted within a four-sublattice antiferromagnet model with a weak isotropic corner-center interaction of magnetic ions in the body-centered tetragonal lattice with unbroken axial symmetry. The latter is of particular importance, being a necessary prerequisite for the interpreting of the antiferromagnetic ordering in DTN in terms of the BEC scenario. The physically simplest scenario would correspond to the isotropic "corner-center" exchange. Since the exchange interaction within each sublattice is antiferromagnetic, the ground state in DTN in the ordered state (Bc1 < B < Bc2) is predicted to be frustrated and thus infinitely degenerated.

  • Invited lecture (Conferences)
    Highly Frustrated Magnetism (HFM) 2008, 07.-12.09.2008, Braunschweig, Germany

Permalink: https://www.hzdr.de/publications/Publ-11862
Publ.-Id: 11862


Kleintier Positronen-Emissions-Tomographie zur in vivo Charakterisierung von Tumoren

Bergmann, R.

kein Abstract verfügbar

  • Invited lecture (Conferences)
    Wissenschaftliches Kolloquium Leibniz-Institut für Naturstoff-Forschung und Infektionsbiologie e.V. (HKI), 02.12.2008, Jena, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-11861
Publ.-Id: 11861


Photoactivation experiment on 197Au and its implications on the dipole strength in heavy nuclei

Nair, C.; Junghans, A. R.; Erhard, M.; Bemmerer, D.; Beyer, R.; Grosse, E.; Klug, J.; Kosev, K.; Rusev, G.; Schilling, K. D.; Schwengner, R.; Wagner, A.

The 197Au(gamma, n) reaction is used as an activation standard for the photodisintegration studies on astrophysically relevant nuclei. At the bremsstrahlung facility of the superconducting electron accelerator ELBE of FZ Dresden-Rossendorf, photoactivation measurements on 197Au have been performed with bremsstrahlung endpoint energies from 8.0 to 15.5 MeV. The measured activation yield is compared with previous experiments as well as calculations using Hauser-Feshbach statistical models. It is shown that the experimental data are best described by a two-lorentzian parametrization with taking the axial deformation of 197Au into account. The experimental 197Au(gamma, n) reaction yield measured at ELBE via the photoactivation method is found to be consistent with previous experimental data using photon scattering or neutron detection methods.

Keywords: bremsstrahlung; photoactivation

  • Physical Review C 78(2008)5, 055802

Permalink: https://www.hzdr.de/publications/Publ-11860
Publ.-Id: 11860


Influence of irradiation on the metabolism of melanoma cells and development of corresponding in vitro and in vivo models for the characterization of radiopharmaceuticals

Mosch, B.; Müller, K.; Pietzsch, J.

Aim:

Irradiation is an effective implement for the therapy of solid tumors. But often single cells elude this treatment and constitute a basis for recurrence of the primary tumor and formation of metastases. One possible explanation for this observation could be predicted on irradiationdependent metabolic changes which lead to a predisposition of certain cells to show enhanced survival and migratory activity. The aim of our study was to investigate metabolic properties of irradiated melanoma cells which should further enable us to develop and validate appropriate in vitro and in vivo models for the characterization of new radiopharmaceuticals for diagnosis and therapy of metastases and solid tumors.

Materials and methods:

We applied different singledose X‐ray irradiation (1, 2, 5, 7, 10, and 20 Gy) to murine B16‐F10 melanoma cells. At several timepoints we analyzed cell viability, growth properties, clonogenic regrowth capability, cellular proliferation, and expression of cell cycle markers. Furthermore, we analyzed the cellular uptake of the radiotracers 2‐[18F]Fluor‐2‐desoxy‐D‐glucose and 3‐O‐Methyl‐[18F]fluor‐L‐DOPA, providing information about the glucose and amino acid metabolism before and after irradiation. Additionally, we performed in vivo studies in a syngeneic mouse model to analyze the capability of untreated and irradiated melanoma cells to form lung metastases. Results: In a dosedependent manner we detected a decrease in the growth properties, viability and tracer uptake of the melanoma cells, particularly, in the period 3 to 6 days after irradiation. In contrast, already one day after irradiation cell cycle analyses showed an increase in the number of G2/M phase cells and the expression of G2‐phase markers in irradiated compared to untreated cells. Additionally, in vitro analyses showed an influence of irradiation concerning the extent to form lung metastases in the mouse.

Conclusion:

Our results indicate that metabolic changes in melanoma cells after irradiation can be analyzed by a set of different in vitro and in vivo approaches, even in a dose‐dependent manner. Using this experimental approach, we are able to characterize new radiotracers and, furthermore, to investigate metabolic effects of applied radiopharmaceuticals in combination with experimental radiation therapy.

  • Poster
    Annual Congress of the European Association of Nuclear Medicine (EANM), 11.-15.10.2008, München, Deutschland
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 35(2008), S316
    DOI: 10.1007/s00259-008-0896-9

Permalink: https://www.hzdr.de/publications/Publ-11859
Publ.-Id: 11859


Irradiation of melanoma cells induced changes in the S100A4-RAGE interaction toward a promigratory phenotype

Haase, C.; Wolf, S.; Pietzsch, J.

Aim:

Tumor metastasis is responsible for most cancer deaths, and can occur after long periods of tumor dormancy. The treatment of metastases would be either radiation only or surgery combined with adjunctive postoperative radiation therapy. Multiple reports have focused on the role of S100A4 in cancer progression, specifically its ability to enhance metastasis. We suggest that RAGE (receptor for advanced glycation endproducts) is a putative receptor for S100A4.
However, the role of S100A4‐RAGE interaction in melanoma metastasis is still unclear. The aim of this study was to characterize molecular and cellular mechanism of irradiated B16‐F10 melanoma cells, thereby, examining changes in the S100A4‐RAGE interaction and the ability for migration of irradiated melanoma cells in the presence of tumor associated macrophages.

Material and Methods:

B16‐F10 cells were exposed to single dose irradiation (5 Gy, 20 Gy) and mouse RAW 264.7 cells were used as a model for tumor‐associated macrophages. The expression of S100A4 and RAGE was quantified via real‐time RT‐PCR and Western‐blot analysis. Furthermore, cell migration was investigated with irradiated B16‐F10 cells in a 24‐transwell chamber for 16 h and 24 h. Migration was influenced by seeding RAW cells as a chemoattractant into the lower
compartments and recombinant S100A4 as a stimulus to the upper compartments. Migratory cells were labeled with Calcein‐AM and quantified in a standard fluorescence microplate reader.

Results:

The total number of vital irradiated B16‐F10 cells is significantly decreased with increasing dose up to 20 Gy and up to six days, thereby altering their morphological appearance. Expression of S100A4 and RAGE is significantly increased in surviving B16‐F10 cells three and six days after 20 Gy (p[[Unsupported Character ‐ ]]0.05). Furthermore, irradiated B16‐F10 cells have a higher migratory activity supposed due to an enhanced expression of S100A4 and RAGE. RAW cells and/or recombinant S100A4 caused a further increasing migration activity of irradiated cells (20 Gy).

Conclusions:

There is a close association of melanoma cells and macrophages with alterations of their migratory and invasive activity after irradiation. We suppose a perpetual para‐/autocrine expression mechanism of extracellular S100A4 and RAGE,
and thereby changing functional properties of melanoma cells towards a promigratory phenotype. This study was supported in part by the Deutsche Forschungsgemeinschaft (grant Pi 304/1‐1).

  • Poster
    Annual Congress of the European Association of Nuclear Medicine (EANM, 11.-15.10.2008, München, Deutschland
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 35(2008), S316
    DOI: 10.1007/s00259-008-0896-9

Permalink: https://www.hzdr.de/publications/Publ-11858
Publ.-Id: 11858


In vitro investigation of Yttrium-90-citrate-, Erbium-169-citrateand Rhenium-186-sulfur-colloid stability

Bergmann, R.; Pinckert, J.

Aim:

Yttrium‐90‐citrate‐ (YMM‐1), Erbium‐169‐citrate‐ (ERMM‐1), and Rhenium‐186‐sulfurcolloid (Re‐186‐MM1) were applied in radiosynovectomy (RSO), a local intraarticular injection of radionuclides in colloidal form for radiotherapy. The local metabolism of the colloidal particles is not fully understood; however, knowledge about the leakage is important for risk assessment. Therefore we investigated diffusion of the radionuclides by equilibrium dialysis, which provided
information about interaction of the colloids with synovia, stability and size in controlled equilibrium conditions.

Materials & Methods:

Carrier added YMM‐1, ERMM‐1, Re‐186‐MM1 colloids were dispersed and dialyzed against synovia, different electrolytes and buffers separated by dialysis membranes with a molecular weight cut off (MWCO) of 10,000 Dalton. The activity
concentration in the dialysis compartment was studied up to 24 hours. Tl‐201‐chloride, F‐18‐FDG, and Er‐169‐chloride were used as reference tracers.

Results:

The equilibria were reached at the latest 10 hours after start of dialysis. The ionic Er‐169‐chloride (as negative control) and Re‐186‐perrhenate showed very similar diffusion kinetics compared with reference radiotracers. The colloidal radionuclides, incubated and dialyzed against electrolytes comparable with plasma (MEM Dulbeco medium), human synovia, or phosphate containing buffers were not detected in the dialysis solution (lower 0.5% of applied dose(%ID)), except Re‐186‐MM1. Significant amounts of this compound were found in the dialysis compartment. Incubation of the colloids with isotonic sodium chloride or 0.1 M hydrochloric acid was followed by an activity release into the dialysis solution YMM‐1 (67%ID) and ERMM‐1 (62%ID). Conclusion: The different stabilities of the carrier added radiocolloids studied in different electrolyte solutions was mainly a result of the presence of phosphate ions. The low solubility of the phosphates of rare earth elements, the binding to synovia proteins, and hydroxylation were the main mechanisms of colloidal particle stabilization or reformation of free or secondary formed Erbium or Yttrium ions. This generally results in formation of particles of low diffusibility, increasing the retention of the radiocolloids inside the joint before the radionuclide‐loaded colloidal particles are phagocytozed by macrophages in the inflamed synovial membrane.

  • Lecture (Conference)
    Annual Congress of the European Association of Nuclear Medicine (EANM), 11.-15.10.2008, München, Deutschland
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 35(2008), S204
    DOI: 10.1007/s00259-008-0896-9

Permalink: https://www.hzdr.de/publications/Publ-11857
Publ.-Id: 11857


Biodistribution and metabolism of stabilized bombesin labeled with new Cu-64-chelating ligands

Bergmann, R.; Walther, M.; Juran, S.; Gasser, G.; Pietzsch, J.; Stephan, H.

Aim:

Gastrin releasing peptide receptors (GRPR) are overexpressed in different human tumors like prostate, breast and squamous cell carcinomas. The goal of this study was to compare the biodistribution and metabolism of a stabilized bombesin analogue radiolabeled with two new Cu‐64‐complexes for PET imaging of GRPR expression in xenografted mice.

Method:

Cu‐64 was complexed with a bis(2‐pyridylmethyl) derivative of 1,4,7‐triazacyclononane (TAC) and a bispidine 1,5‐dicarboxylic acid derivative (Cu‐64‐N2Py4‐OH(COOH)2) conjugated to a stabilized bombesin (BBN) derivative βhomoGlu‐βAla‐βAla‐[Cha13, Nle14]BN(7‐14) (Garcia Garoya et al. 2007). Biodistribution, elimination, and metabolism were studied in rats. Tumor accumulation was exemplarily evaluated with small animal PET in xenografted mice bearing prostate (PC3), squamous cell carcinoma (FaDu), and colorectal (HT‐29) human tumors. Cu‐64 chloride was studied for comparison. Results: PET imaging of Cu‐64‐N2Py4‐OH(COOH)2‐BBN in mice 1 h after injection revealed tumor‐to‐background ratios of 2.1 (PC3), 2.4 (FaDu control), 1.0 (FaDu blocked), and 1.5 (HT‐29). The uptake found in PC3 tumors with tissue sampling was significantly higher (5.3 control; 2.6 blocked). In comparison to the Cu‐64‐TAC‐BBN, the uptake of Cu‐64‐N2Py4‐OH(COOH)2‐BBN in rat pancreas and intestine was lower but the accumulation in kidney, liver, and stomach was higher. The metabolic stabilities of the Cu‐64‐labeled BBN‘s studied were comparable. More than 85% of the original substances were remained after 1 hour in vitro incubation with rat blood or blood plasma. In vivo all compounds were fast metabolized in rats, and lower than 5% of the original compounds were recovered in arterial blood plasma 1 hour after injection. However, the metabolism in xenografted nude mice was slower, after 1 hour 12% of blood plasma activity correspond to the original compound.

Conclusion:

Both investigated new Cu‐64 chelating agents conjugated to a stabilized BBN analogue showed typical BBN biodistribution and GRPR specific accumulation in vivo. The differences in biodistribution and metabolism between Cu‐64‐TAC‐ and Cu‐64‐N2Py4‐OH(COOH)2) labeled BBN demonstrate the influence of the Cu‐64 chelating units on these processes, especially on the nonspecific activity biodistribution. Comparison of biodistribution data of the BBN analogues and Cu‐64 chloride indicate only marginal, if any, in vivo copper demetalation, revealing high in vivo stability of the copper complex units. With further optimization of the radiolabeling in particular of specific activity the low specific uptake should increase. The studied chelating agents appear to be promising candidates for copper labeling of peptides under mild conditions. Partly supported by the 6th framework EU‐project “BioCare”, proposal # 505785.

  • Lecture (Conference)
    Annual Congress of the European Association of Nuclear Medicine (EANM), 11.-15.10.2008, München, Deutschland
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 35(2008), S153
    DOI: 10.1007/s00259-008-0896-9

Permalink: https://www.hzdr.de/publications/Publ-11856
Publ.-Id: 11856


The use of nanocavities for the fabrication of ultrathin buried oxide layers

Ou, X.; Kögler, R.; Skorupa, W.; Möller, W.; Wang, X.; Vines, L.

A continuous buried oxide (BOX) layer with a thickness of only 58 nm is formed in silicon by oxygen implantation at 185 keV with a very low ion dose of 1×1017 cm-2 and subsequent He implantation. Due to the implanted He efficient oxygen gettering occurs at the implantation induced damage and results in the accumulation of the implanted oxygen as well as of oxygen in-diffused from the annealing atmosphere. The morphology and the resistivity of the resulting silicon-on-insulator (SOI) structure are analyzed by cross section transmission electron microscopy and by cross section scanning spreading resistance microscopy, which is demonstrated to be a promising tool for the characterisation of a thin BOX layer.

Keywords: Ion Implantation; Silicon; Oxygen; SIMOX; BOX

Permalink: https://www.hzdr.de/publications/Publ-11855
Publ.-Id: 11855


Grafting of Poly(3-hexylthiophene) from Poly(4-bromostyrene) Films by Kumada Catalyst-Transfer Polycondensation: Revealing of the Composite Films Structure

Khanduyeva, N.; Senkovskyy, V.; Beryozkina, T.; Bocharova, V.; Simon, F.; Nitschke, M.; Stamm, M.; Grötzschel, R.; Kiriy, A.

In order to achieve a stable, long-term operation of flexible electronic devices, it is necessary to firmly fix semiconductive conjugated polymers to plastic substrates, thus preventing their damage against delamination or chemical treatments. Surface-initiated Kumada catalyst-transfer polycondensation of 2-bromo-5-chloromagnesio-3-alkylthiophene from photo-cross-linked poly(4-bromostyrene), PS(Br), films leads to covalent grafting of regioregular head-to-tail poly(3-hexylthiophenes), P3HT. Herein, we investigate the grafting process in detail and elucidate the structure of the resulting composite films using ellipsometry, X-ray photoelectron spectroscopy, Rutherford backscattering spectroscopy, and conductive mode atomic force microscopy techniques. In particular, we found that the grafting process is much more efficient if thick PS(Br) supporting layers are used. The maximal reachable thickness of the P3HT deposits is directly proportional to the thickness of the supporting PS(Br) layers. The obtained data suggest that the grafting process occurs not only at the PS(Br)/polymerization solution interface but also deeply inside the swollen PS(Br) films, penetrable for the catalyst and for the monomer. The process results into a kind of interpenetrated PS(Br)/P3HT network in which relatively short (∼10 nm) P3HT grafts emanate from long cross-linked PS(Br) chains. The films show good stability against delamination, high electrical conductivity in the doped state, and high swellability that might be exploited for construction of fully “plastic” electronic devices and sensors.

  • Macromolecules 41(2008)20, 7383-7389

Permalink: https://www.hzdr.de/publications/Publ-11854
Publ.-Id: 11854


Quark mass dependence of thermal excitations in QCD in one-loop approximation

Seipt, D.; Bluhm, M.; Kämpfer, B.

A comprehensive determination of the quark mass dependence in the dispersion relations of thermal excitations of gluons and quarks in non-Abelian gauge theory (QCD) is presented for the one-loop approximation in Feynman gauge. Larger values of the coupling are admitted, and the gauge dependence is discussed. In a Dyson-Schwinger type approach, the effect of higher orders is estimated for asymptotic thermal masses.

Permalink: https://www.hzdr.de/publications/Publ-11853
Publ.-Id: 11853


Reactive magnetron sputtering of CuInS2 adsorbers for thin film photovoltaic: relation between deposition parameters and film morphoöogy

Seeger, S.; Grötzschel, R.; Ellmer, K.

For the preparation of high-quality CuInS2 absorber films, two film properties are decisive: large crystallites and compact film morphologies. In this work we investigate the influence of the deposition parameters discharge power and substrate bias, on the morphology and chemical composition of CuInS2 films, which were prepared by reactive magnetron sputtering (radio frequency) in H2S/Ar atmosphere. A lateral concentration distribution along the substrate axis, which is caused by the arrangement the copper and indium cathodes in our sputtering equipment, was used to study the influence of the Cu-to-In ratio on the film growth. At a Cu-to-In ratio of one, which can be adjusted by the discharge powers at the copper and indium target to be positioned at the middle of the substrate, the crystallites in the film are small in size and separated by crevices from each other. In order to achieve compact CuInS2 films, the negative substrate bias was varied systematically (-15V to -150 V). The influence of the ion assistance, i.e. the impact of positive argon ions onto the growing film, was investigated with respect to the chemical composition and the morphology of the films.

Keywords: magnetron sputtering; CuInS2

  • Lecture (Conference)
    23rd European Photovoltaic Solar Energy Conference, 01.-4.9.2008, Feria Valencia, Spain

Permalink: https://www.hzdr.de/publications/Publ-11852
Publ.-Id: 11852


Dynamical scaling at the metal-insulator transition in YHx

Pronin, A. V.; Romijn, I. G.; Brom, H. B.; Hoekstra, A. F. T.; Gorshunov, B. P.; Wosnitza, J.

There are strong indications that the light-induced metal-insulator transition in YHx is a quantum phase transition. If true, the conductivity should develop not only a characteristic scaling behavior with regard to doping and temperature, but also to frequency. Here we present our results on the frequency-temperature scaling of the conductivity in YHx at sub-terahertz frequencies on the insulating and metallic sides of the metal-insulator transition. In the insulating state, the data suggest the expected ω/T-scaling to hold. In the metallic phase, however, this scaling breaks down, and the sub-terahertz conductivity demonstrates frequencyindependent behavior. These results do not agree with the simplest picture of a quantum phase transition.

  • Invited lecture (Conferences)
    3rd International Conference "Fundamental Problems of High Temperature Superconductivity" (FPS'08), 13.-17.10.2008, Moscow-Zvenigorod, Russia

Permalink: https://www.hzdr.de/publications/Publ-11851
Publ.-Id: 11851


Bacterial Uranium Binding - Basis for the Development of Innovative Materials

Raff, J.

Within the radio-ecological research on bacteria, living in uranium mining waste piles, it was demonstrated that the microorganisms developed an intelligent detoxification strategy to survive in such an extreme habitat. They possess a special kind of surface layer (S-layer) to protect themselves from uranium. Beside fundamental research on the protein-radionuclide interaction, the S-layers were used for the development of new and innovativ materials. Immobilized on carrier materials, these proteins keep their high and selective metal binding properties and can thusly be used for (multi)functional coatings. For example, the basic technology allows the production of metal selective filter materials for the removal and recovery of metals and the production of photocatalytical active nanoclusters immobilized on different carriers or surfaces. The latter can be used for new and innovative water treatment, whereby pharmaceutical remnants and hormones will be eliminated.

  • Lecture (others)
    INE-FZD Workshop, 22.-23.10.2008, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-11849
Publ.-Id: 11849


Fe nanoparticles embedded in MgO crystals

Shalimov, A.; Potzger, K.; Geiger, D.; Lichte, H.; Talut, G.; Misiuk, A.; Reuther, H.; Stromberg, F.; Zhou, S.; Baehtz, C.; Fassbender, J.

Iron nanoparticles embedded in MgO crystals were synthesized by Fe+ ion implantation at an energy of 100 keV and varying fluences from 3×10e16 to 3×10e17 cm-2. Investigations of structural and magnetic properties of Fe nanoparticles have been performed using magnetometry, x-ray diffraction, transmission electron microscopy and Mössbauer spectroscopy, as well as by theoretical Preisach modeling of bistable magnetic systems. It has been found that alpha- and gamma-Fe nanoparticles are formed for all fluences. The content of the alpha- Fe phase increases at higher fluences and after annealing. The influence of post implantation annealing at 800 ºC in vacuum and under enhanced up to 10 kbar hydrostatic pressure in argon atmosphere on the formation of nanoparticles has been analyzed.

Keywords: iron; ferromagnetic materials; nanoparticles; ion implantation

  • Journal of Applied Physics 105(2009), 064906
  • Virtual Journal of Nanoscale Science & Technology 19(2009)13

Permalink: https://www.hzdr.de/publications/Publ-11848
Publ.-Id: 11848


Visualizing different uranium oxidation states during the surface alteration of uraninite and uranium tetrachloride

Grossmann, K.; Arnold, T.; Steudtner, R.; Weiss, S.; Bernhard, G.

The surface alteration of uraninite (U(IV)O2) and uranium tetrachloride UCl4 in air atmosphere was studied by confocal laser scanning microscopy (CLSM) and laser-induced fluorescence spectroscopy (LIFS) using an excitation wavelength of 408 nm. It was found that within minutes the oxidations state on the surface of the uraninite and the uranium tetrachloride changed. During the surface alteration process U(IV) atoms on the uraninite and uranium tetrachloride surface became stepwise oxidized by a one-electron step at first to U(V) and than further to U(VI). These observed changes in the oxidation states of the uraninite surface were microscopically visualized and spectroscopically identified on basis of their fluorescence emission signal. A fluorescence signal in the wavelength range of 415-475 nm was indicative for metastable uranium(V) and a fluorescence signal in the range of 480-560 nm was identified as uranium(VI). In addition, the oxidation process of tetravalent uranium in aqueous solution at pH 0.3 was visualized by CLSM and U(V) was fluorescence spectroscopically identified.

Keywords: uraninite UO2; uranium; uranium tetrachloride UCl4; CLSM; oxidation states; fluorescence spectroscopy

  • Naturwissenschaften 96(2009)8, 963-974

Permalink: https://www.hzdr.de/publications/Publ-11847
Publ.-Id: 11847


Exceptionally Long Exciton Photoluminescence Lifetime in ZnO Tetrapods

Zhong, Y.; DjurišIc´, A. B.; Hsu, Y. F.; Wong, K. S.; Brauer, G.; Ling, C. C.; Chan, W. K.

The fabrication of ZnO tetrapods of an exceptional optical quality, based on a photoluminescence (PL) lifetime in the range of tens of nanoseconds and the absence of defect emission, is found to be possible in a very narrow temperature range only. A reduction in the PL lifetime and an increase in the defect emission are observed for both higher and lower growth temperatures. The obtained PL lifetime for the optimal growth temperature is an order of magnitude higher than the best results achieved in epilayers and single crystals. Temperature dependence of the PL lifetime of high-quality tetrapod samples indicates that the dominant recombination processes are radiative.

  • Journal of Physical Chemistry C 112(2008)42, 16286-16295

Permalink: https://www.hzdr.de/publications/Publ-11846
Publ.-Id: 11846


Magnetic excitations in the BEC candidate DTN: high-field ESR studies

Zvyagin, S.

NiCl2-4SC(NH2)2 (known as DTN) is a quantum S = 1 chain system with strong easy-plane anisotropy that is regarded as a new candidate for the Bose-Einstein condensation (BEC) of magnons, with critical fields Bc1 = 2.1 T, Bc2 = 12.6 T (defined at T = 0). Electron Spin Resonance (ESR) studies of magnetic excitations in DTN in fields up to 25 T are presented. Based on analysis of the single-magnon excitation mode observed in the high-field spin-polarized phase at temperatures above Tc (Tc ≤ 1.2 K), a revised set of spin-Hamiltonian parameters is obtained. Our results yield D = 8.9 K, Jc = 2.2 K, and Ja,b = 0.18 K for the anisotropy, intrachain, and interchain exchange interactions, respectively. These values are used to calculate the antiferromagnetic phase boundary, magnetization and the frequency-field dependence of two-magnon bound-state excitations predicted by theory and observed in DTN for the first time. Furthermore, we present a systematic study of the low-energy excitation spectrum of DTN in the field-induced magnetically ordered phase at temperatures down to 0.45 K. We argue that two gapped modes observed in the experiment can be consistently interpreted within a four-sublattice antiferromagnet model with a finite interaction between two tetragonal subsystems and unbroken axial symmetry. The latter is of crucial importance for the interpretation of the field-induced ordering in DTN in terms of the BEC of magnons.

  • Invited lecture (Conferences)
    Correlated Electron Systems in High Magnetic Fields, 13.-17.10.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-11845
Publ.-Id: 11845


Spectroscopic studies of the uranium(VI) interaction with nitrogen and sulfur containing model ligands

Raditzky, B.; Joseph, C.

The migration and interaction behavior of actinides can be effectively influenced by humic substances, biopolymers ubiquitous in natural environments, due to their ability for complex and colloid formation and their redox properties. In addition to oxygen containing functional groups, humic substances also offer sulfur and nitrogen containing functionalities.
The aim of this work is to determine the influence of various nitrogen and sulfur containing functional groups on the uranium(VI) complexation and to evaluate their contribution in comparison to oxygen containing functional groups. For this, simple organic model ligands that can occur as building blocks for humic substances are used. In this study, results are presented for the uranium(VI) complexation by the organic ligands benzenesulfonic acid and 4-hydroxybenzenesulfonic acid as well as anthranilic and nicotinic acid. The complex formation constants for the uranium(VI) complexation were determined applying time-resolved laser-induced fluorescence spectroscopy (TRLFS).

Keywords: uranium(VI); fs-TRLFS; TRLFS; benzenesulfonic acid; 4-hydroxybenzenesulfonic acid; anthranilic acid; nicotinic acid; complexation

  • Lecture (others)
    ACTINET 05-08 Project Meeting, 27.-31.10.2008, Larnaca, Cyprus

Permalink: https://www.hzdr.de/publications/Publ-11844
Publ.-Id: 11844


Synthetic Humic Acids for Basic Studies of Humic Acid Complexation Properties and Migration Processes

Sachs, S.

In order to improve the knowledge about the interaction processes between humic acids and metal ions, e.g., actinide ions, various humic acid model substances with different functional properties were developed at the Institute of Radiochemistry. These includes synthetic humic acids with different functional group contents and various structural elements, chemically modified humic acids, humic acids with pronounced redox functionalities, and isotopically labeled humic acids. The presentation gives an overview about the synthesis, characterization and application of the different types of designed humic acid model substances.

Keywords: Humic acid; humic acid model substances; synthesis; characterization; modification; labeling; application

  • Lecture (others)
    ACTINET 05-08 Project Meeting, 27.-31.10.2008, Larnaca, Cyprus

Permalink: https://www.hzdr.de/publications/Publ-11842
Publ.-Id: 11842


Redox Properties of Humic Substances in the Systems Np(V)/(IV) and U(VI)/(IV)

Schmeide, K.

The Np(V) and U(VI) reducing capacities of humic substances of varying functionality are discussed.

Keywords: Neptunium; Uranium; Reduction; Tetravalent; Humic acid; Redox processes

  • Lecture (others)
    ACTINET 05-08 Project Meeting, 27.-31.10.2008, Larnaca, Cyprus

Permalink: https://www.hzdr.de/publications/Publ-11841
Publ.-Id: 11841


Formation of UO2(OH)HA(I) Studied by TRLFS

Sachs, S.

The complexation of U(VI) with purified Aldrich humic acid was studied at pH 7 under nitrogen atmosphere. Using two independent laser-induced spectroscopic methods, the formation of the ternary uranium(VI) mono hydroxo humate complex (UO2(OH)HA(I)) was studied and complexation data were derived. The results of this study are discussed in comparison to literature data.

Keywords: Humic acid; complexation; uranium; U(VI); ternary complexes; TRLFS

  • Lecture (others)
    ACTINET 05-08 Project Meeting, 27.-31.10.2008, Larnaca, Cyprus

Permalink: https://www.hzdr.de/publications/Publ-11840
Publ.-Id: 11840


A critical review on atomistic simulations of solid-phase epitaxial regrowth of amorphous Si and Ge layers

Posselt, M.; Gabriel, A.-A.

In semiconductor technology ultra-shallow junctions are produced by ion implantation and subsequent annealing. The relatively high fluence applied in dopant implantation and the use of pre-amorphization implantation may lead to the formation of an amorphous (a-)layer. In the first stage of annealing the solid phase epitaxial regrowth (SPER) of the a-layer takes place. SPER leads to redistribution of dopants, and they are incorporated into the crystal either substitutionally or within clusters containing self-interstitials (Is) or vacancies. In Si the SPER process leaves beyond the original a/c interface the end-of-range (EOR) damage which contains an excess of Is. During further annealing, free Is are emitted from the EOR damage and may cause an enhanced diffusion of the dopants. It is highly desirable to understand the processes occurring during SPER on the atomic level. This work presents results of classical molecular dynamics simulations of SPER in pure Si and Ge. While in the last decade several authors investigated SPER in Si, the regrowth of a-Ge layers has not been considered yet. The critical review of SPER simulations using different interatomic potentials shows that the experimental regrowth rates cannot be reproduced reasonably well. Moreover, it is found that the results obtained by different groups under virtually equal conditions do not agree. Possible reasons for these differences are outlined. The main cause for the disagreement with experimental data is the inaccuracy of the interatomic potentials used. Proposals for physically-based improvements are discussed. They are based on a better description of the amorphous phase using a modified potential, without changing the established potential for the single-crystalline material. It is shown that a-Si and a-Ge with realistic structural and thermodynamic propertied can be obtained by various modifications of known interatomic potentials, whereas it is very difficult to find a modification which also yields the correct SPER rate.

Keywords: computer simulation; Si; Ge; solid-phase epitaxial regrowth

  • Lecture (Conference)
    The 9th International Conference on Computer Simulation of Radiation Effects in Solids (COSIRES2008), 12.-17.10.2008, Beijing, China

Permalink: https://www.hzdr.de/publications/Publ-11839
Publ.-Id: 11839


Terahertz wave emission from an InGaAsN large area emitter

Peter, F.; Winnerl, S.; Schneider, H.; Helm, M.; Köhler, K.

We present large-area emitters based on InGaAsN which show efficient THz emission for excitation wavelengths up to 1.35 μm.
The substrate material consists of a 1000 nm GayIn1-yAs1-xNx (y=0.11 and x=0.04) layer grown by molecular-beam epitaxy on semi-insulating GaAs. On top there is an additional GaAs/Al0.3Ga0.7As heterostructure with thicknesses of 5 nm for the GaAs and 60 nm for the AlGaAs layer, respectively. Transmission measurements with a Fourier spectrometer reveal a bandgap corresponding to a wavelength of 1.5 μm. The resistance of a complete device with an active area of 1 mm2 is 0.3 MΩ. This allows operation with high bias fields (30 kV/cm) without being limited by heating. For excitation an optical parametric oscillator (OPO), tunable between 1.1 μm and 1.5 μm, is used. The pulse duration is 280 fs (FWHM). The THz signal is detected using electro-optical sampling with a 1 mm thick ZnTe crystal. The gating beam (λ = 820 nm) for detection is split off from a Ti:sapphire oscillator which drives the OPO.

  • Poster
    GDR-E-2008 THz Workshop, 25.-26.09.2008, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-11838
Publ.-Id: 11838


Influence of the neutron-kinetic feedback parameter variation on an anticipated transient without SCRAM in a PWR

Kliem, S.; Mittag, S.; Rohde, U.; Weiß, F.-P.

The complete failure of the reactor scram system upon request during an operational transient is called anticipated transient without scram (ATWS). According to the German regulatory guidelines, postulated ATWS events have to be analyzed with regard to their consequences on the safety of nuclear power plants.

Since the course of ATWS transients is determined by a strong interaction of the neutron kinetics with the thermal hydraulics of the system, coupled 3D neutron kinetic/thermal hydraulic code systems are adequate tools for the analysis of such transients. In the following, the coupled code system DYN3D/ATHLET is applied to the analysis of an ATWS transient. The objective of the present work is to perform a best-estimate analysis with consequent use of a 3D neutron kinetic code (DYN3D) in combination with an advanced thermal hydraulic system code (ATHLET) together with a quantification of differences in the course and the results of transients, which arise from the uncertainties of neutron-physical conditions.

Typically, the complete failure of the main feed water supply is assumed to be the bounding ATWS event with regard to the maximum primary coolant pressure, which can be reached during the transient. The situation is aggravated if the main coolant pumps remain in operation.

For this particular transient, the influence of different neutron-physical conditions on the course of the transient was analyzed. Variations of the reactivity coefficients of the moderator density, the moderator temperature (spectral coefficient) and the fuel temperature were assumed.

One of the most relevant safety parameters in this ATWS event is the primary circuit pressure. It has been found that the spreading of the first pressure maximum is influenced only by the variation of the moderator density coefficient. A variation of the Doppler coefficient contributes only to the second pressure peak. For that reason the spreading of the tolerance limits during the second pressure peak is higher.

  • Contribution to proceedings
    2009 International Conference on Advances in Mathematics, Computational Methods, and Reactor Physics, 03.-07.05.2009, Saratoga Springs, USA
    Proceedings of the 2009 International Conference on Advances in Mathematics, Computational Methods, and Reactor Physics, CDROM paper 201661, La Grange Park: ANS, 9780894480690
  • Lecture (Conference)
    2009 International Conference on Advances in Mathematics, Computational Methods, and Reactor Physics, 03.-07.05.2009, Saratoga Springs, USA

Permalink: https://www.hzdr.de/publications/Publ-11837
Publ.-Id: 11837


Achieving high free electron mobility in ZnO:Al thin films grown by reactive pulsed magnetron sputtering

Cornelius, S.; Vinnichenko, M.; Shevchenko, N.; Rogozin, A.; Kolitsch, A.; Möller, W.

The study is focused on improvement of the free electron mobility in Al-doped ZnO films grown by cost-effective deposition method of reactive pulsed magnetron sputtering. At optimum growth conditions it yields low absorbing films with Hall effect mobility of 46 cm2V-1s-1, free electron density of 6x1020 cm-3 and electrical resistivity of 2.26x10-4 Ohm cm. The relation between the mobility and free electron density for the films grown at different conditions is discussed in terms of ionized impurity scattering and impurity clustering mechanism or grain boundary limited transport.

Keywords: transparent conductive oxides; ZnO:Al; reactive magnetron sputtering; electrical properties

Permalink: https://www.hzdr.de/publications/Publ-11836
Publ.-Id: 11836


Jahrestagung Kerntechnik 2008 - Sektionsbericht Sektion: Thermo- und Fluiddynamik

Schaffrath, A.; Kliem, S.

Der Beitrag gibt einen Überblick über die in den Sitzungen der Sektion Thermo- und Fluiddynamik gehaltenen Vorträge.

  • atw - International Journal for Nuclear Power 53(2008)8/9, 559-561

Permalink: https://www.hzdr.de/publications/Publ-11835
Publ.-Id: 11835


Radiation treatment planning in brain tumours Potential impact of 3-O-methyl-6-[18F]fluoro-L-DOPA and PET

Alheit, H.; Oehme, L.; Winkler, C.; Füchtner, F.; Hoepping, A.; Grabowski, J.; Kotzerke, J.; Beuthien-Baumann, B.

Aim:

Amino acid PET has become an important diagnostic tool for brain tumour imaging. In this data analysis, the potential impact of amino acid PET with 3-O-methyl-6-[18F]fluoro-L-DOPA ([18F]OMFD) on radiation treatment planning is addressed by the following questions: 1. Was tumour tissue identified with OMFD-PET which was not covered by the conventionally derived planning target volume (PTV)? 2. Would the PTV have been changed incorporating OMFD-PET?

Patients, methods:

OMFD-PET of 25 patients after subtotal resection of malignant glioma was evaluated. The region of elevated tracer uptake of PET and of contrast enhancing masses on MRI were outlined as separate gross tumour volumes (GTVMRI and GTVOMFD) and reconstructed in the planning CT for comparison with the conventionally drawn GTVconv. A PTVnew based on GTVconv+MRI was calculated. Pairwise differential volumes were calculated to estimate overlap and differential volumes delineation by each image modality and the PTVconv and PTVnew respectively.

Results:

Differential volume analysis showed > 10 cm3 of GTVOMFD outside GTVconv and GTVMRI in 5/25 patients respectively. From GTVMRI >10 cm3 were found outside GTVOMFD in 8/25 patients. Although all tumour areas indicated by
[18F]OMFD were covered by the conventionally derived PTV, based on a GTVOMFD+MRI, the PTVnew would have been enlarged >20% in seven patients. In seven patients the PTVnew would have been reduced.

Conclusion:

OMFD-PET indicated tumour tissue outside the tumour region identified with MRI, adding valuable information for the delineation of the GTV in radiation treatment planning. OMFD-PET contains the potential to tailor the high dose radiation to the appropriate tumour volume, especially if dose escalation is desired.

Keywords: Brain tumour; positron emission tomography; radiation treatment planning; multimodal imaging; 3-O-methyl-6-[18F]fluoro-L-DOPA

Permalink: https://www.hzdr.de/publications/Publ-11834
Publ.-Id: 11834


Ultrasound at high magnetic fields: first scientific results at the HLD

Zherlitsyn, S.

Ultrasound investigations are a powerful experimental tool to study various phase transitions and critical phenomena. This technique is now available at the Dresden High Magnetic Field Laboratory (HLD) as part of the pulsed field user program. The possible application of the infrared radiation produced by next-door free electron lasers for photoacoustic spectroscopy will be discussed. Here I will present two results recently obtained at the HLD by use of ultrasound technique. First, I report results of magnetoacoustic studies of the quantum spin-chain magnet NiCl2-4SC(NH2)2 (DTN) having a field-induced ordered antiferromagnetic (AF) phase. The longitudinal acoustic c33 mode, which propagates along the spin chains, modulates the in-chain exchange interaction and shows a softening, accompanied by energy dissipation in the acoustic wave in the vicinity of the quantum critical points. Another example is CdCr2O4, a geometrically frustrated magnet with a metamagnetic phase transition at 28 T followed by a very wide magnetization plateau with one half of the full moment of S = 3/2 Cr3+. We have performed an ultrasonic investigation of a high quality CdCr2O4 single crystal in pulsed magnetic fields up to 64 T. A minimum in the sound velocity and a peak in the attenuation have been observed at 28 T for temperatures below the temperature of the AF phase transition TN = 7.8 K. Another anomaly in the sound velocity has been observed at 60 T, where the magnetization plateau is terminated. The observed anomalies become smoother at higher temperatures. The experimental data are analyzed by use of a model where the main contribution to the spin-lattice interaction arises from the exchangestriction coupling.

  • Invited lecture (Conferences)
    Physical Phenomena at High Magnetic Fields (PPHMF), 01.-06.08.2008, Laulasmaa Resort, Estonia

Permalink: https://www.hzdr.de/publications/Publ-11833
Publ.-Id: 11833


Spin dynamics in the BEC candidate DTN studied by high-field ESR

Zvyagin, S. A.; Wosnitza, J.; Kolezhuk, A. K.; Batista, C. D.; Krzystek, J.; Zapf, V. S.; Jaime, M.; Paduan-Filho, A.; Glazkov, V. N.; Sosin, S. S.; Smirnov, A. I.

NiCl2-4SC(NH2)2 (DTN) is a quantum S=1 chain system with strong easy-pane anisotropy and a new candidate for the Bose-Einstein condensation of the spin degrees of freedom. Employing high-field electron spin resonance technique, we were able to study frequency-field dependence of magnetic excitations in DTN in fields up to 25 T [1] and at temperatures down to 0.45 K [2]. As a result of our studies, we were able to accurately estimate parameters of the spin-Hamiltonian for this compound. The values were used to calculate the antiferromagnetic phase boundary, magnetization and the frequency-field dependence of two-magnon bound-state excitations predicted by theory and observed in DTN for the first time. Excellent quantitative agreement with experimental data has been obtained. In addition, the excitation spectrum in DTN in the field-induced ordered phase has been studied. Two gapped modes have been observed and their frequency-field dependencies. We show that our observations can be consistently interpreted within the four-sublattice antiferromagnet model, involving a finite interaction between two tetragonal sublattices and leaving the axial symmetry intact, which is crucial for the interpretation of the field-induced ordering in DTN in terms of the BEC of magnons. Supported in part by NHMFL (through NSF and DOE) and DFG.

  • Invited lecture (Conferences)
    Physical Phenomena at High Magnetic Fields (PPHMF), 01.-06.08.2008, Laulasmaa Resort, Estonia

Permalink: https://www.hzdr.de/publications/Publ-11832
Publ.-Id: 11832


Force-induced structural transitions in cross-linked DNA films

André, A.; Fontaine-Vive, F.; Möller, H. M.; Fischer, T.; Maret, G.; Forsyth, V. T.; Gisler, T.

We report on the preparation and characterization of wet-spun films of sodium DNA in which intermolecular cross-links were introduced following formaldehyde treatment. Raman scattering shows that the DNA in moderately cross-linked films is mainly in th B conformation. Stretching experiments show a transition from plastic to elastomeric behavior with increasing exposure to the cross-linking agent. Elastomeric DNA films are strongly disordered.X-ray diffraction shows that stretching of moderately cross-linked film under controlled high humidity conditions results in increased molecular orientation as well as the appearance of meridional reflections at 7.4-7.8 and 8.2 A. These reflections are not observed for any of the calssical conformations associated with mixed sequence DNA, and may arise from extended base-pair stacking in a stretched DNA structure.

Permalink: https://www.hzdr.de/publications/Publ-11831
Publ.-Id: 11831


Ultrasonic Investigation of NiCl2-4SC(NH2)2 in the vicinity of the quantum critical points

Zherlitsyn, S.; Chiatti, O.; Sytcheva, A.; Wosnitza, J.; Zvyagin, A. A.; Zapf, V. S.; Jaime, M.; Paduan-Filho, A.

es hat kein Abstract vorgelegen!

  • Poster
    High Frustrated Magnetism (HFM) 2008, 07.-12.09.2008, Braunschweig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-11830
Publ.-Id: 11830


Evolution of ferromagnetic order in URhGe alloyed with Ru, Co and Si

Sakarya, S.; Huy, N. T.; van Dijk, N. H.; de Visser, A.; Wagemaker, M.; Moleman, A. C.; Gortenmulder, T. J.; Klaasse, J. C. P.; Uhlarz, M.; von Löhneysen, H.

We have investigated the evolution of ferromagnetic order in the correlated metal URhGe (Curie temperature TC = 9.5K) by chemical substitutionof Ru, Co and Si. Polycrystalline samples URh1−xRuxGe (x ≤ 0.6), URh1−xCoxGe (x ≤ 0.9) and URhGe1−xSix (x ≤ 0.2) have been prepared and the magnetic properties have been investigated by magnetization and transport experiments. In the case of Ru doping, TC initially increases, but then decreases linearly as a function of x and is completely suppressed for xcr ≈ 0.38. The Curie temperature in the URh1−xCoxGe series has a broad maximum TC = 20K near x = 0.6 and then drops to 8K for x = 0.9. In the case of Si doping TC stays roughly constant. We conclude that the alloy systems URh1−xRuxGe and URh1−xCoxGe are interesting candidates to study the ferromagnetic instability.

  • Journal of Alloys and Compounds 457(2008), 51-56

Permalink: https://www.hzdr.de/publications/Publ-11829
Publ.-Id: 11829


Flow imaging by high speed transmission tomography

Johansen, G. A.; Hampel, U.; Hjertaker, B. T.

Fourth generation medical x-ray scanners using a gantry with a rotating X-ray source and a fixed circular detector array as sensor head, are too slow for imaging of the process dynamics for instance in multiphase flows. To avoid inconsistent measurements and motion blurring, all measurements need to be carried out in a short time compared to the process time constants of the process dynamics. Two different high speed tomographic imaging systems are presented here demonstrating that image rates of several thousand images per second is possible.

Keywords: High speed tomographic imaging; Gamma-ray tomography; X-ray tomography; Electron beam scanning tomography; Flow imaging

  • Contribution to proceedings
    7th International Topical Meeting on Industrial Radiation and Radioisotope Measurement (IRRMA 7), 22.-27.06.2008, Prague, Czech Republic
    Proceedings
  • Applied Radiation and Isotopes 68(2010), 518-524
    DOI: 10.1016/j.apradiso.2009.09.004
    Cited 36 times in Scopus

Permalink: https://www.hzdr.de/publications/Publ-11828
Publ.-Id: 11828


Si-based light emitters as a key element for smart biosensors

Rebohle, L.; Cherkouk, C.; Skorupa, W.; Prucnal, S.; Helm, M.

In this work we will present our concept of direct fluorescence analysis using Ge- or rare earth-implanted Si based light emitters for the detection of estrogen in waterish solutions. We will discuss the performance of these light emitters in terms of efficiency, operation lifetime, stability, and operation voltage and show that they are generally suitable for lab-on-chip applications. In addition we report about the composition and fabrication of a bioactive layer on top of the light emitters which has the task to immobilize estrogen selectively from a waterish sample. Finally, the interaction of a Tb-implanted light emitter with a quantum dot dye is investigated.

Keywords: Smart biosensing; Estrogen detection; Si-based light emission; Electroluminescence; Rare earth ion implantation

  • Lecture (Conference)
    Eurosensors XXII, 07.-10.09.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-11827
Publ.-Id: 11827


The correlation between electroluminescence properties and the microstructure of Eu-implanted MOS light emitting devices

Rebohle, L.; Lehmann, J.; Kanjilal, A.; Prucnal, S.; Nazarov, A.; Tyagulskii, I.; Skorupa, W.; Helm, M.

In this work we investigated the correlation between the EL, the electrical properties and the microstructure of Eu-implanted MOS light emitting devices. The EL spectrum shows a red EL line centered at 618 nm which is usually assigned to Eu3+ and a broad blue-green EL band attributed to Eu2+. It was found that the red EL is favored by low injection currents, low Eu concentrations, lower anneal temperatures and shorter anneal times, especially for FLA. These properties are correlated with microstructural changes triggered by ion implantation and annealing, especially with the formation and ripening of Eu or Eu oxide clusters which strongly quench the red EL. Finally, the influence of Eu agglomerations at the injecting interface on the electrical properties of the light emitter is discussed.

Keywords: Europium; Electroluminescence; Si-based light emission; MOS

  • Poster
    IBMM 2008 - 16th International Conference on Ion Beam Modification of Materials, 31.08.-05.09.2008, Dresden, Deutschland
  • Nuclear Instruments and Methods in Physics Research B 267(2009)8-9, 1324-1327

Permalink: https://www.hzdr.de/publications/Publ-11826
Publ.-Id: 11826


Rare earth implanted Si-based light emitters and their use for smart biosensor applications

Rebohle, L.; Cherkouk, C.; Prucnal, S.; Helm, M.; Skorupa, W.

In this presentation we will review our recent progresses in the development of Si-based light emitters consisting of a MOS structure with a rare earth implanted SiO2 layer. Depending on the implanted element, namely Gd, Tb and Eu, the devices exhibit strong electroluminescence in the UV, the green and in the red spectral region. It will be shown that the implantation and annealing conditions during the fabrication strongly influence the microstructural, electrical and electro¬luminescence device properties and are of special importance for the efficiency and life time of future devices. In order to improve the stability of the devices, both LOCOS (local oxidation of Si) processing and additional protection layers made of SiON were applied to the devices. The advantages and the shortcomings of these light emitters regarding their efficiency, life time, electrical excitation conditions, cut-off frequencies and miniaturization potential are compared with the needs of smart photonic and biosensor applications. A special approach for utilizing the light emitters for the detection of organic pollutants in fluid media by fluorescence analysis is discussed in more detail. In this approach the light emitter is directly placed beneath the dye-labelled sample exciting the dye whose light emission can be recorded by a suitable external detector.

Keywords: Smart biosensing; Estrogen detection; Si-based light emission; Electroluminescence; Rare earth ion implantation

  • Invited lecture (Conferences)
    VII-th International Conference on Ion Implantation and other Applications of Ions and Electrons – ION 2008, 16.-19.06.2008, Kazimierz Dolny, Polen
  • Vacuum 83(2009)SI Suppl., S24-S28

Permalink: https://www.hzdr.de/publications/Publ-11825
Publ.-Id: 11825


Blue and red electroluminescence of Europium-implanted MOS structures as a probe for the dynamics of microstructure

Rebohle, L.; Lehmann, J.; Prucnal, S.; Kanjilal, A.; Nazarov, A.; Tyagulskii, I.; Skorupa, W.; Helm, M.

The strong blue and red electroluminescence from Eu-implanted SiO2 layers were investigated as a function of implantation and annealing conditions. It is shown that the red electroluminescence assigned to Eu3+ ions is favored by low Eu concentrations, low anneal temperatures and short anneal times. Based on a more quantitative analysis of the electroluminescence spectra this preference is explained by a shorter supply of oxygen for higher Eu concentrations and the growth of Europium oxide clusters with increasing anneal temperatures and anneal times. The correlation between electroluminescence and microstructure is supported by transmission electron microscopy investigations and demonstrates that the electroluminescence of Eu-implanted SiO2 layers can serve as a probe for the microstructural development in the active layer of the light emitter.

Keywords: Europium; Electroluminescence; Si-based light emission; MOS

  • Applied Physics Letters 93(2008), 071908

Permalink: https://www.hzdr.de/publications/Publ-11824
Publ.-Id: 11824


Si-based light emitters and their use for smart biosensor applications

Rebohle, L.; Cherkouk, C.; Prucnal, S.; Skorupa, W.; Helm, M.

In this presentation we will give a review about our recent progress in the development of rare earth-implanted Si-based light emitters. The devices consist of a MOS structure with a transparent front electrode made of indium tin oxide (ITO) and a SiON protection layer between the oxide and the ITO layer for a strong life time improvement. Gd, Tb and Eu are implanted in the middle of the oxide layer, and depending on the element the devices show strong electroluminescence in the UV, the green and in the red spectral region. The electrical and electroluminescence properties of these devices are discussed and evaluated in respect of possible applications on the field of biosensor technology. Based on the advantages and the shortcomings of these light emitters an approach for their use in biosensor applications is developed. In this approach the light emitters are utilized for the detection of biological substances by fluorescence analysis. There the emitter is directly placed beneath the dye-labelled sample exciting the dye whose light emission can be recorded by a suitable external detector. A very promising application is the detection of organic pollutants, e.g. estrogen, in drinking water.

Keywords: Smart biosensing; Estrogen detection; Si-based light emission; Electroluminescence; Rare earth ion implantation

  • Lecture (Conference)
    E-MRS 2008 Spring Meeting, 26.-30.05.2008, Strasbourg, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-11823
Publ.-Id: 11823


Multifunctional Cyclam Derivatives with Carbohydrates and Peptides

Röhrich, A.; Stephan, H.; Kretzschmann, A.; Noll, S.; Bergmann, R.; Steinbach, J.

Multifunctional chelating systems with linked biomolecules provide the possibility to develop novel diagnostic and therapeutic agents with enhanced stability and improved bio-availability. In this perspective, cyclam derivatives 1 are attractive candidates for developing new metalloradiopharmaceuticals. Biomolecules like sugars and peptides direct the solubility behavior and the targeting efficiency.

Michael addition on cyclam with methyl acrylate and subsequent aminolysis with ethylene diamine delivered the tetraamino product 2.1 Ligands with four sugar units 3 were obtained by thiourea-bridging of sugar isothiocyanates with 2.2 Peptide coupling led to conjugates 4 with the hexapeptide neurotensin(8-13) which is interesting for the targeting of ductal pancreatic carcinomas.

Isothermal titration calorimetry (ITC) was used in order to characterize the interaction between glycoclusters 3 and the lectin Concanavalin A. In vitro binding studies between ligand 4 and the neurotensin receptor 1 (NTR1) were performed using the human colon adenocarcinoma cell line HT-29.

The glycoclusters 3 showed a distinct glycoside clustering effect which can be explained by an entropy advantage for the tetramer compared to the sugar monomer. Thiourea-containing compounds 3 form very stable Cu(II) complexes with slow kinetics.3 On the other hand, a rapid attainment of Cu(II) complexation equilibria was observed in the case of the peptide conjugate 4.

Multifunctional sugar and peptide conjugates of branched cyclam derivatives possess interesting complexation and targeting properties. Peripheral modifications provide the opportunity of tailoring the bio-distribution.

1. Stephan, H.; Geipel, G.; Appelhans, D.; Bernhard, G.; Tabuani, D.; Komber, H.; Voit, B. Tetrahedron Lett. 2005, 46, 3209.
2. Stephan, H.; Röhrich, A.; Noll, S.; Steinbach, J.; Kirchner, R.; Seidel, J. Tetrahedron Lett. 2007, 48, 8834.
3. Röhrich, A.; Noll, S.; Stephan, H.; Steinbach, J.; Bergamini, G.; Balzani, V. in „Technetium, Rhenium and other Metals in Chemistry and Nuclear Medicine“ U. Mazzi (Ed.), SGE Editoriali, Padova, Italy, 2006, 7, 233.

  • Poster
    2nd EUCHEMS Chemistry Congress, Chemistry: The Global Science, 16.-20.09.2008, Torino, Italy

Permalink: https://www.hzdr.de/publications/Publ-11822
Publ.-Id: 11822


The complex dynamics between the Eu2+ and Eu3+ electroluminescence of Eu-implanted MOS light emitting devices

Rebohle, L.; Lehmann, J.; Prucnal, S.; Nazarov, A.; Tyagulskii, I.; Skorupa, W.; Helm, M.; Biskupek, J.; Kaiser, U.

Si-based light emitters were fabricated by ion implantation of Eu into a thermally grown oxide layer on Si followed by a thermal treatment and the deposition of a SiON and an indium tin oxide layer. The Eu ions were implanted in such a way that the maximum Eu concentration varies between 0.1 and 6 %. Flash lamp annealing, rapid thermal annealing and furnace annealing at temperatures between 900 and 1100°C were applied in order to activate the Eu-related luminescence centres. The electroluminescence (EL) spectrum of the Eu-implanted SiO2 layers shows a relatively sharp red EL line centered at 618 nm and a broad EL band in the blue-green spectral region which is usually assigned to the light emission of Eu3+ and Eu2+ ions, respectively. In this work we will show that the ratio between blue and red EL shows a complex dependence on the Eu concentration, the annealing time and the annealing temperature, but that some general tendencies can be identified, too. So the blue EL assigned to Eu2+ ions will dominate for high concentrations and high annealing temperatures. The dynamics of Eu2+ and Eu3+ is discussed in the framework of charge injection, charge transport and the EL mechanism which is based on the direct excitation of Eu ions by hot ballistic electrons.

Keywords: Europium; Electroluminescence; Si-based light emission; MOS

  • Lecture (Conference)
    E-MRS 2008 Spring Meeting, 26.-30.05.2008, Strasbourg, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-11821
Publ.-Id: 11821


Dendritic Ligands with Fluorescent Labels

Röhrich, A.

Overview on known fluorescent labeled dendrimers and their cellular uptake behavior. New synthetic route using MMTr and boc protecting groups. UV-vis and time-resolved laser fluorescence spectra.

  • Lecture (others)
    5th Supraphone Meeting, 29.-31.05.2008, Prague, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-11820
Publ.-Id: 11820


Complexation of uranium(VI) with peptidoglycan

Barkleit, A.; Moll, H.; Bernhard, G.

We investigated the interaction of UO22+ with peptidoglycan (PG), the main part of the outer membrane of gram-positive bacteria, by potentiometric titration and time-resolved laser-induced fluorescence spectroscopy (TRLFS) over a wide pH (2.0 to 9.0) and concentration range (10-5 to 10-4 M U(VI), 0.01 to 0.2 g/L PG). With potentiometry two different dissociation constants for the carboxyl sites of glutamic acid and diaminopimelic acid (pKa = 4.55 ± 0.02 and 6.31 ± 0.01), and one averaged pKa for hydroxyl and amino groups (which are not distinguishable) (9.56 ± 0.03) and the site densities could be identified. With potentiometry three different uranyl PG complexes were ascertained: two 1 : 1 uranyl carboxyl complexes R-COO-UO2+, one with the glutamic acid carboxyl group (log β110 = 4.02 ± 0.03), which has a very small formation ratio, and one with the diaminopimelic acid carboxyl group (log β110 = 7.28 ± 0.03), and a mixed 1 : 1 : 1 complex with additional hydroxyl or amino coordination, R-COO-UO2(+)-Ai-R (Ai = NH2 or O-) (log β1110 = 14.95 ± 0.02). With TRLFS, also three, but different species could be identified: a 1 : 1 uranyl carboxyl complex R-COO-UO2+ (log β110 = 6.9 ± 0.2), additionally a 1 : 2 uranyl carboxyl complex (R-COO)2-UO2 (log β120 = 12.1 ± 0.2), both with diaminopimelic acid carboxyl groups, and the mixed species R-COO-UO2(+)-Ai-R (Ai = NH2 or O-) (log β1110 = 14.5 ± 0.1). The results are in accordance within the errors of determination.

Permalink: https://www.hzdr.de/publications/Publ-11819
Publ.-Id: 11819


Cell cycle regulating kinase Cdk4 as a potential target for tumor cell treatment and tumor imaging

Graf, F.; Köhler, L.; Knieß, T.; Wüst, F.; Mosch, B.; Pietzsch, J.

The cyclin-dependent kinase (Cdk)-cyclin D/INK4/retinoblastoma (pRb)/E2F cascade, which controls the G1/S transition of the cell cycle, has found to be altered in many neoplasias. Inhibition of this pathway by using, e.g., selective Cdk4 inhibitors has been suggested to be a promising approach for cancer therapy. We hypothesized that appropriately radiolabeled Cdk4 inhibitors are suitable probes for tumor imaging and may be helpful studying cell proliferation processes in vivo by positron emission tomography. Herein, we report the synthesis and biological, biochemical, and radiopharmacological characterization of two 124I-labeled small molecule Cdk4 inhibitors (8-cyclopentyl-6-iodo-5-methyl-2-(4-piperazin-1-yl-phenylamino)-8H-pyrido[2,3-d]-pyrimidin-7-one (CKIA) and 8-cyclopentyl-6-iodo-5-methyl-2-(5-(piperazin-1-yl)-pyridin-2-yl-amino)-8H-pyrido[2,3-d]pyrimidin-7-one (CKIB)). Our data demonstrate a defined and specific inhibition of tumor cell proliferation through CKIA and CKIB by inhibition of the Cdk4/pRb/E2F pathway emphasizing potential therapeutic benefit of CKIA and CKIB. Furthermore, radiopharmacological properties of [124I]CKIA and [124I]CKIB observed in human tumor cells are promising prerequisites for in vivo biodistribution and imaging studies.

Permalink: https://www.hzdr.de/publications/Publ-11818
Publ.-Id: 11818


Microscopic and spectroscopic investigation of U(VI) interaction with the monocellular green alga Chlorella vulgaris

Vogel, M.; Günther, A.; Raff, J.; Bernhard, G.

The green alga Chlorella vulgaris has the ability to bind high amounts of uranium(VI) in the pH range from 3 to 6 and to a lesser extend at higher pH values. The uranium removal is almost complete at pH 4.4 and 6 by metabolic active and inactive cells under the given experimental conditions. Laser-induced fluorescence spectroscopy was used for the characterization of uranyl species formed in solutions and biomass. Fluorescence spectroscopic investigations indicate differences of the formed algal uranyl complexes in dependence of the metabolic activity of cells and the uranyl speciation. Scanning electron microscopy demonstrates that the algal cell wall is involved in the binding of U(VI).

Keywords: Chlorella vulgaris; algae; uranium(VI); biosorption; TRLFS; SEM

  • Lecture (others)
    Meeting INE-FWR, 22.-23.10.2008, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-11817
Publ.-Id: 11817


PET-CT Co-Registration for In-Beam PET

Fiedler, F.; Sobiella, M.; Enghardt, W.

In-beam PET is based on the β+-activation of the irradiated volume and of the beam itself by interactions between the incoming ions and the nuclei of the tissue. Due to the special situation of in-beam PET, i.e. space for the rotating patient table and for the beam delivery has to be provided, the unique in-beam PET scanner cannot be a full ring device as in conventional PET imaging. It is necessary for patient evaluation to establish a relationship between the β+-activity created during therapeutic treatment and the anatomy of the patient. Therefore, the PET images have to be superimposed onto the planning X-ray computed tomogram (CT) with sub-millimeter precision. Since in-beam PET images and planning CT are acquired at completely different devices, their coordinates are matched by means of stereotactic coordinates. To enable a high flexibility of the measurement the double head PET scanner is rotatable around the central beam. Due to the weight of the detectors, the PET gantry is deformed under rotation, resulting in a displacement of the crystal positions in comparison to those, which are expected when assuming a rigid body rotation. Therefore, a technical solution to define the exact detector positions at any rotation angles has been developed. An exemplary embodiment will be illustrated by means of the in-beam PET installation at GSI.

Keywords: in-beam PET; PET-CT Coregistration

  • Poster
    2008 Nuclear Science Symposium, Medical Imaging Conference and 16th Room Temperature Semiconductor Detector Workshop, 19.-25.10.2008, Dresden, Germany
  • Contribution to proceedings
    2008 Nuclear Science Symposium, Medical Imaging Conference and 16th Room Temperature Semiconductor Detector Workshop, 19.-25.10.2008, Dresden, Germany
    PET-CT Co-Registration for In-Beam PET

Permalink: https://www.hzdr.de/publications/Publ-11816
Publ.-Id: 11816


Ion Beam Therapy: Principles and Quality Assurance - Short Course

Kraft, G.; Fiedler, F.; Weyrather, K. W.; (Editors)

Gerhard Kraft studied Physics at Heidelberg and Cologne where he received his Ph.D. in nuclear physics. He founded the biophysics department at GSI where he developed the heavy ion tumor therapy together with Wilma K. Weyrather. She studied Physics at the University of Cologne and received her Ph.D. at the University of Giessen in Radiobiology in 1978. They both together initiated the Radiobiology program at GSI and later on the tumor therapy.

The novel features of the GSI tumor therapy are the extreme target conform beam delivery using an intensity modulated scanning method, the biology based treatment planning and the in vivo control of the patient using online-PET. In order to cover the target with a dose having a homogenous biological effect and a steep gradient at the borders the Target volume is dissected in slices of equal particle energy which are covered by a grid of 20,000 to 50,000 pixels of different beam positions. For all these pixels the individual covering of particles has to be calculated according to the wanted dose level and the actual value of the Relative Biological Effectiveness, RBE, at the specific pixel. These RBE values depend on the physical composition of the beam at each location and the biological properties of the affected tissue mainly on its repair capacity of complex DNA damage.

For the clinical success of the up to now more than 400 patients treated with this technique, the quality assurance of the technical equipment, the biological modelling for the treatment planning and the physical dose delivery are extremely important.

The biological corrections of the treatment planning are based on the Local Effect Model LEM verified in many experiments. It is also confirmed by the follow up of the treated patients that did not show large side and late effects. For the quality assurance of the beam delivery an online measurement of the emission of gamma quants have been developed and used during patient irradiation. When penetrating through the patient a significant fraction of the primary beam such as carbon or other ions under go nuclear reaction with the tissue resulting in radioactive positron emitting isotopes either from the beam such as 11C and 10C or from the target atoms such as 15O. Their positron decay can be monitored from outside and can be used to track the beam stopping inside the patient.

Fine Fiedler did her Ph.D. in 2008 at the Technical University of Dresden and studied the feasibility to monitor the stopping points of the beam inside the patients. She is working in the In-beam-PET group of the Oncoray Dresden. She will report that the PET techniques are capable assessing the relevant parameters for quality assurance in respect to anatomical landmarks. But it has been also shown that it is possible to extend this technique to other ion than carbon such as Protons, 3He, 7Li and 16O.

In general, the short course will introduce in the physical and biological rational of ion beam therapy. It will explain the critical feature in planning and beam delivery and will give the principles for quality assurance.

Keywords: ion therapy

  • Invited lecture (Conferences)
    2008 Nuclear Science Symposium, Medical Imaging Conference and 16th Room Temperature Semiconductor Detector Workshop, 19.-25.10.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-11815
Publ.-Id: 11815


Atomic-scale structure of Mo6S6 nanowires

Kibsgaard, J.; Tuxen, A.; Levisen, M.; Lægsgaard, E.; Gemming, S.; Seifert, G.; Lauritsen, J.; Besenbacher, F.

We have studied atomic-scale structure of the Mo6S6 nanowires using Scanning Tunneling Microscopy and Spectroscopy (STM and STS) and Density Functional Theory (DFT). A novel synthesis route based on metallic Mo precursors is presented for the selective formation of elementary pure Mo6S6 nanowires. The Mo6S6 nanowires selectively organize as trimer bundles, and each of the Mo6S6 nanowires consists of an electrically conducting Mo backbone dressed with a sulfur exterior cap. The Mo6S6 nanowires may thus be of interest as novel building blocks in nanoelectronics since the Mo6S6 nanowires exist in a robust, singular structural conformation with uniquely defined electrical (metallic) properties.

Keywords: nanowires; molybedenum sulfide; DFT; DF-TB; density-functional; STM; STS; scanning-tunneling microscopy; scanning tunneling spectroscopy

Permalink: https://www.hzdr.de/publications/Publ-11814
Publ.-Id: 11814


Electromechanical switch based on Mo6S6 nanowires

Popov, I.; Gemming, S.; Okano, S.; Ranjan, N.; Seifert, G.

We investigate the structural, electronic, and transport properties of mechanically deformed Mo6S6 nanowires using a density-functional based tight binding method extended with a Green's functions formalism. We present two interesting results: first, the properties of the wire are not affected by bending, and second, a metal-insulator transition occurs when the wire is twisted. This indicates that molybdenum sulfide nanowires can be used as a nanocable to flexibly transfer information between electromechanical switches, which can be also constructed from the same wires. Hence, our results suggest the Mo6S6 nanowires as unique building blocks for future nanodevices.

Keywords: nanowires; molybdenum sulfide; density-functional; DFT; DFTB; conductivity

Permalink: https://www.hzdr.de/publications/Publ-11813
Publ.-Id: 11813


Cell irradiation setup and dosimetry for radiobiological studies at ELBE

Zeil, K.; Beyreuther, E.; Lessmann, E.; Wagner, W.; Pawelke, J.

The radiation source ELBE delivers different types of secondary radiation, which is used for cell irradiation studies in radiobiological research. Thereby an important issue is the determination of the biological effectiveness of photon radiation as a function of photon energy by using low energetic, monochromatic channeling radiation (10-100 keV) and high energetic bremsstrahlung (up to 40 MV). Radiobiological studies at the research facility ELBE demand special technical and dosimetric prerequisites. Therefore, a cell irradiation system (CIS) has been designed, constructed and installed at the beam line. The CIS allows automatic irradiation of a larger cell sample number and the compensation of spatial inhomogeneity of the dose distribution within the beam spot. The recently introduced GafChromic EBT radiochromic film model has been used to verify the cell irradiation dose deposition achieving a dose uncertainty of <5 %. Both, the installed cell irradiation system and the developed dosimetric procedure based on the use of the EBT film have been experimentally tested at ELBE. The biological effectiveness of 34 MV bremsstrahlung with respect to 200 kV X-rays from a conventional X-ray tube has been determined. An RBE value of 0.75 has been measured in good agreement with literature.

  • Nuclear Instruments and Methods in Physics Research B 267(2008)14, 2403-2410

Permalink: https://www.hzdr.de/publications/Publ-11812
Publ.-Id: 11812


Elektromagnetisch getriebene Strömungen in elektrochemischen Systemen

Weier, T.; Cierpka, C.; Gerbeth, G.

Der in elektrochemischen Systemen in der Regel vorhandene Stromfluss führt zusammen mit einem magnetischen Feld zu Lorentzkraftverteilungen im Elektrolyten, die dessen Bewegungszustand modifizieren können. Dieser an sich einfache Effekt kann sich abhängig vom Aufbau der elektrochemischen Zellen in überraschend vielseitigen Strömungsformen äußern. Dies wird anhand von Beispielen demonstriert und im Hinblick auf aktuelle theoretische Vorstellungen diskutiert.

Keywords: Lorentz force; magneto-electrochemistry

  • Lecture (others)
    Lehrstuhlkolloquium Professur für Magnetofluiddynamik, 15.10.2008, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-11811
Publ.-Id: 11811


Magnetic quantum oscillations in strongly correlated metals – experimental data meets theoretical predictions

Wosnitza, J.

One of the most powerful methods to determine bulk band-structure parame-ters in metals is the measurement of magnetic quantum oscillations. This can be done e.g. by measuring the field-dependent magnetization, i.e., the de Haas-van Alphen (dHvA) effect, or by resolving Shubnikov-de Haas (SdH) oscillations in the field-dependent resistivity. It is, however, only the comparison with sophisticated band-structure calculation that a deeper understanding of the electronic properties of metals can be gained. Besides the user-lab activities a strong in-house research program is pursued at the HLD. Thereby, the focus is laid on the investigation of correlated electron systems at high magnetic fields. This covers e.g. the recently found clear thermodynamic evi-dence for the existence of the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state in a layered organic superconductor [1] and the determination of the band- and angle-resolved superconducting coupling strength in the borocarbide superconductor LuNi2B2C [2].

  • Invited lecture (Conferences)
    DFT Meets Experiment & 7th Tutorial Hands-on-FPLO, 25.-28.08.2008, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-11809
Publ.-Id: 11809


Science and Infrastructure at the New Dresden High Magnetic Field Laboratory

Wosnitza, J.

At the Forschungszentrum Dresden-Rossendorf the Dresden High Magnetic Field Laboratory (Hochfeld-Magnetlabor Dresden), HLD, has opened his doors for users since the beginning of 2007. Pulsed magnetic fields up to 70 T (with 150 ms pulse length in a 24 mm bore) as well as smaller ones (60-65 T, with 25-50 ms pulse lengths) are available for users. Further pulsed magnets with ever increasing performances are being continuously developed, having set the ambitious goal of reaching 100 T on a 10 ms time scale. A 60 T magnet with a 1 second pulse length is ready to be tested allowing thermodynamic experiments to be performed. At the HLD a world-unique experimental infrastructure is at hand with next-door free electron lasers making possible unique high-field magneto-optical and ESR experiments in the range 4-230 µm. Besides the user-lab activities a strong in-house research program is persued at the HLD. Thereby, the focus is laid on the investigation of correlated electron systems at high magnetic fields. This covers e.g. the recently found clear thermodynamic evidence for the existence of the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state in a layered organic superconductor [1] and the determination of the band- and angle-resolved superconducting coupling strength in the borocarbide superconductor LuNi2B2C [2].

  • Invited lecture (Conferences)
    Physical Phenomena at High Magnetic Fields, 01.-06.08.2008, Laulasmaa Resort, Estonia

Permalink: https://www.hzdr.de/publications/Publ-11808
Publ.-Id: 11808


High magnetic field properties of quasi-two-dimensional organic superconductors

Wosnitza, J.

Investigations of quasi-two-dimensional (2D) organic charge-transfer salts in high magnetic fields have deepened our understanding of these materials. Comprehensive studies of e.g. magnetic quantum oscillations or angular-dependent transport properties allowed to unravel details of the electronic band-structure. In some cases, deviations from the usually adopted Fermi-liquid picture for metals were observed. For β´´-(BEDT-TTF)2SF5CH2CF2SO3 e.g., strong indications for an incoherent electronic transport across the layers and a field-induced insulating state were found. Strong magnetic fields as well influence the superconducting state, usually by driving the super¬conductor from the Shubnikov into the normal state and thereby suppressing the critical temperature in a well-known monotonous fashion. The 2D organic superconductors are, however, good candidates for exhibiting in addition to the Meissner and Shubnikov phase the so-called FFLO state, named after Fulde, Ferrell, Larkin, and Ovchinnikov, when applying the magnetic field exactly parallel to the conducting layers. In this case, the orbital critical field is much larger than the Pauli-limiting field for these singlet superconductors. In the FFLO state, superconductivity can survive even at magnetic fields above the Pauli limit by sacrificing parts of the superconducting volume with a spatially oscillating order parameter. Our recent high-resolution specific-heat experiments in parallel fields up to 28 T for κ-(BEDT-TTF)2Cu(NCS)2 gave strong evidence for the existence of the FFLO state. For fields above 21 T, the superconducting transition becomes first order signalling that the Pauli limit is reached. Below about 3 K, the upper critical field increases sharply and a second first-order transition appears within the superconducting phase. With additional magnetic-torque measurements up to 32 T we were able to follow the phase diagram down to 50 mK. The well-known electronic band-structure parameters allow a thorough theoretical estimate of the Pauli-limited superconducting phase diagram.

  • Invited lecture (Conferences)
    International Symposium on Molecular Conductors 2008, 22.-25.07.2008, Okazaki, Japan

Permalink: https://www.hzdr.de/publications/Publ-11807
Publ.-Id: 11807


Die Jagd nach dem Feldrekord - Forschung in hohen Magnetfeldern

Wosnitza, J.

Was sind Magnetfelder? Wo findet man sie? Wie erzeugt man sie und zu was sind sie nutze? Antworten auf diese Fragen sollen in dem Vortrag durch Vorstellung der weltweiten Bestrebungen, immer höhere Magnetfelder zu erreichen, gegeben werden. Ähnlich wie z. B. Druck und Temperatur haben magnetische Felder einen tief greifenden Einfluss auf den Zustand und Zustandsänderungen der Materie. Untersuchungen von Materialien in hohen Magnetfeldern sind daher mittlerweile Standard und eine Vielzahl von Anwendungen in unserem täglichen Leben sind ohne Magnetfeldeffekte undenkbar. In der Forschung wird der stetig wachsende Bedarf an möglichst großen Magnetfeldstärken durch Hochfeldlaboratorien abgedeckt. In dem neu aufgebauten Hochfeld-Magnetlabor Dresden sollen demnächst gepulste Magnetfelder bis zu 100 Tesla, dem 2,5-millionenfachen des Erdmagnetfelds, erzeugt werden. Erste Hochfeldmagnete sind in Betrieb und seit 2007 hat neben der Eigenforschung der Nutzerbetrieb begonnen. Der momentane Status des Labors, die Schwierigkeiten, die zur Erzeugung so hoher Magnetfelder überwunden werden müssen, und exemplarische wissenschaftliche Ergebnisse aus Hochfeldstudien sollen vorgestellt werden.

  • Invited lecture (Conferences)
    Festkolloquium zum Tag der Physik an der Universität Regensburg, 18.07.2008, Regensburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-11806
Publ.-Id: 11806


Science at the New Dresden High Magnetic Field Laboratory

Wosnitza, J.

Since the beginning of 2007, the new Dresden High Magnetic Field Laboratory (Hochfeld-Magnetlabor Dresden, HLD) at the Forschungszentrum Dresden-Rossendorf, is accepting proposals for magnet time and has hosted the first user groups. The available user coils at the HLD produce magnetic fields up to about 70 T, with 150 ms pulse length. Besides the ulti-mate goal of a pulsed magnet reaching 100 T for a timescale of 10 ms in a bore of 20 mm, further large-scale magnets (e.g. 60 T, 1 s, 40 mm) are planned. The necessary energy for the pulsed coils is provided by a world-unique 50 MJ capacitor bank. A free-electron-laser facil-ity next door allows high-brilliance radiation to be fed into the pulsed field cells of the HLD, thus making possible unique high-field magneto-optical experiments in the range 3-200 µm. Cryotechniques and different sample probes for a broad range of experimental techniques custom designed for the pulsed magnets are readily available for users. In-house research of the HLD focuses on electronic properties of strongly correlated materials at high magnetic fields. Some examples of the scientific work being carried out will be highlighted.

  • Lecture (others)
    Seminar am Max-Planck-Institut Physik komplexer Systeme, 22.05.2008, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-11805
Publ.-Id: 11805


On the influence of spatial discretization in LWR-burnup calculations with HELIOS 1.9

Merk, B.

Cell- and burnup calculations are the fundament for all deterministic static and transient 3D full core calculations for different operational states of the reactor. The spatial discretization used for the c burnup calculations influences the results for the used integral transport solutions significantly. The arising differences in the neutron flux distribution are demonstrated for different discretization strategies . These differences in the flux distribution cause significant changes in the infinite multiplication factor and in the localized burnup ditribution in the fuel rod for identical averaged burnup. The influence of different discretization strategies on the calculation of homogenized two group cross sections which are forwarded to the 3D full core calculations is investigated and the different calculation times are analyzed.

Keywords: Cell- and Lattice calculation; cross section preparation; HELIOS; Discretization; Burnup calculation

  • Contribution to proceedings
    2009 International Conference on Advances in Mathematics, Computational Methods, and Reactor Physics, 03.-07.05.2009, Saratoga Springs, United States
  • Lecture (Conference)
    2009 International Conference on Advances in Mathematics, Computational Methods, and Reactor Physics, 03.-07.05.2009, Saratoga Springs, United States

Permalink: https://www.hzdr.de/publications/Publ-11804
Publ.-Id: 11804


An analytical solution for an external source problem with delayed neutron using the Telegrapher's equation

Merk, B.

This work presents the development of an analytical solution for a space-time dependent neutron transport problem in a one dimensional system consisting of homogenized medium with a central, time dependent external source by Green's functions. The delayed neutron production is implemented with the multiple scale expansion method. Qualitative results are analyzed for a deeper understanding of the effects of space-time dependent neutron transport. An example for the use of the developed solution for the study of the effect of different levels of subcriticality in accelerator driven systems is given.

Keywords: Time Dependent Neutron Transport; Multiple Scale Expansion; Green's Functions; Accelerator Driven Systems

  • Contribution to proceedings
    2009 International Conference on Advances in Mathematics, Computational Methods, and Reactor Physics, 03.-07.05.2009, Saratoga Springs, United States
  • Lecture (Conference)
    2009 International Conference on Advances in Mathematics, Computational Methods, and Reactor Physics, 03.-07.05.2009, Saratoga Springs, United States

Permalink: https://www.hzdr.de/publications/Publ-11803
Publ.-Id: 11803


Magnetization of Polycrystalline BiFeO3 in High Magnetic Fields

Wardecki, D.; Przenioslo, R.; Sosnowska, I.; Skourski, Y.; Loewenhaupt, M.

The magnetization of polycrystalline ceramic BiFeO3 has been studied with pulsed magnetic fields up to 58 T. We observe a magnetic transition in both, increasing and decreasing magnetic fields. The critical field of the transition decreases with temperature. It is observed at 18.1 T at 80K and 16.1 T at 235K for increasing fields, whereas with decreasing fields the transition is observed at about 1.5 T below these values. The observed transition is the same as that reported in BiFeO3 single crystals at 10K [Kadomtseva et al.: JETP Lett. 79 (2004) 571]. It was attributed to the destruction of the modulated magnetic ordering in BiFeO3.

  • Journal of the Physical Society of Japan 77(2008)10, 103709

Permalink: https://www.hzdr.de/publications/Publ-11802
Publ.-Id: 11802


VGF-Kristallzüchtung mit kombinierten AC/DC-Magnetfeldern

Pätzold, O.; Lantzsch, R.; Grants, I.; Gerbeth, G.; Stelter, M.

s werden Ergebnisse von VGF-Kristallzüchtungen von GaAs und Ge-Si Kristallen unter dem Einfluss eines wandernden Magnetfeldes vorgestellt. Das Magnetfeld erzeugt eine Strömung in der Schmelze, die wiederum deutlichen Einfluss auf die Form der Phasengrenze und die Dotierstoffverteilung in der Nähe der Phasengrenze hat.

  • Lecture (Conference)
    DGKK-Workshop „Herstellung und Charakterisierung von massiven Verbindungshalbleitern“, 09.-10.10.2008, Erlangen, Germany

Permalink: https://www.hzdr.de/publications/Publ-11801
Publ.-Id: 11801


Sektionsberichte Jahrestagung Kerntechnik 2008 - Teil 1

Dagan, R.; Rohde, U.; Faber, W.

Von Berichterstattern werden die Präsentationen des fachlichen Teils der Jahrestagung Kerntechnik mit den Technischen Sitzungen und Fachsitzungen zusammengefasst. Der Beitrag beinhaltet Berichte über die Sektion "Reaktorphysik und Berechnungsmethoden".

Keywords: reactor physics; methods of calculations

  • atw - International Journal for Nuclear Power 53(2008)8/9, 556-567
    ISSN: 1431-5254

Permalink: https://www.hzdr.de/publications/Publ-11800
Publ.-Id: 11800


Absolute versus convective helical magnetorotational instability in a Taylor-Couette flow

Priede, J.; Gerbeth, G.

We analyze numerically the magnetorotational instability of a Taylor-Couette flow in a helical magnetic field (HMRI) using the inductionless approximation defined by a zero magnetic Prandtl number (Pm=0). The Chebyshev collocation method is used to calculate the eigenvalue spectrum for small amplitude perturbations. First, we carry out a detailed conventional linear stability analysis with respect to perturbations in the form of Fourier modes that corresponds to the convective instability which is not in general self-sustained. The helical magnetic field is found to extend the instability to a relatively narrow range beyond its purely hydrodynamic limit defined by the Rayleigh line. There is not only a lower critical threshold at which HMRI appears but also an upper one at which it disappears again. The latter distinguishes the HMRI from a magnetically-modified Taylor vortex flow. Second, we find an absolute instability threshold as well. In the hydrodynamically unstable regime before the Rayleigh line, the threshold of absolute instability is just slightly above the convective one although the critical wave length of the former is noticeably shorter than that of the latter. Beyond the Rayleigh line the lower threshold of absolute instability rises significantly above the corresponding convective one while the upper one descends significantly below its convective counterpart. As a result, the extension of the absolute HMRI beyond the Rayleigh line is considerably shorter than that of the convective instability. The absolute HMRI is supposed to be self-sustained and, thus, experimentally observable without any external excitation in a system of sufficiently large axial extension.

  • Physical Review E 79(2009), 046310

Permalink: https://www.hzdr.de/publications/Publ-11799
Publ.-Id: 11799


Analyzing of uranium species by fluorescence spectroscopy: A contribution for handling ecological problems caused by uranium mining activities in former Eastern Germany

Baumann, N.; Arnold, T.

As a consequence of extensive and reckless uranium mining in Eastern Germany by the Soviet mining company WISMUT between 1945 and 1990, numerous mining residues exist including important ecological problems in Saxony and Thuringia today. A main topic is washing out mobile uranium species from the rock piles and for-mer mines by surface water. It is necessary to control the pathway, the species, and the amount of migrating ura-nium compounds, and to investigate the interactions between solid mineral phases and mobile uranium species such as sorption, precipitation and forming secondary uranium minerals.
One tool for analyzing tiny amounts of U(VI) species (but also in a minor way U(IV) and U(V) species) is time-resolved laser-induced fluorescence spectroscopy (TRLFS). This method is well established in the Institute of Radiochemistry (IRC) from the Forschungszentrum Dresden-Rossendorf (FZD), especially in case of problems connected with uranium. TRLFS delivers a fluorescence signal with characteristic features in dependence of concentration and speciation of the fluorescent species in the sample. These features are the positions of the peak maxima, and, secondary, characteristic lifetimes of the signals. This technique is applicable in case of U(VI) spe-cies in water solutions, but also in case of thin U(VI) mineral coatings on solid phases.
In that lecture results of investigations of adsorbed uranium species onto mineral surfaces like from gibbsite and from muscovite are presented. Spectroscopic characterisation of several secondary uranium minerals (e.g. bolt-woodite and compreignacite) by determination of the positions of the peak maxima and the lifetimes from the TRLFS signals are presented. The spectroscopic signatures of these uranium (VI) minerals are useful for identi-fying U(VI) mineral species as colloids, as thin coatings on rocks, as minor components in soils, or as alteration products of nuclear waste. Additionally the interaction between an aqueous solution and metallic uranium was investigated by TRLFS: The identification of an ultra-thin secondary mineral film on a disk of metallic depleted uranium (DU) originated from a British tank shell, which was in contact with a phosphate containing solution, will be showed. This example demonstrates the high sensitivity of TRLFS regarding solid U(VI) phases.

Keywords: Uranium mining; U(VI); TRLFS

  • Lecture (others)
    Seminar, 03.11.2008, Bangkok, Thailand

Permalink: https://www.hzdr.de/publications/Publ-11797
Publ.-Id: 11797


Povedenie germanii, implantirovannovo v SiO2 vblisi granizui sraschivania kremnii na isolatore Behavior of Germanium Ion-implanted into SiO2 Near the Bonding Interface of a Silicon-on-Insulator Structure

Popov, V. P.; Tyschenko, E.; Voelskow, M.; Cherkov, A. G.

issledovanui svoistva germanii, implantirovannovo v sloi SiO2
The properties of germanium implanted into the SiO2 layers in the vicinity of the bonding interface of silicon-on-insulator structures are studied. It is shown that, under conditions of high-temperature (1100 °C) annealing, germanium nanocrystals are not formed, while the implanted Ge atoms segregate at the Si/SiO2 bonding interface. It is established that, in this case, Ge atoms are found at sites that are coherent with the lattice of the top silicon layer. In this situation, the main type of traps is the positive-charge traps; their effect is interpreted in the context of an increase in the surface-state density due to the formation of weaker Ge–O bonds. It is found that the slope of the drain–gate characteristics of the back MIS transistors increases; this increase is attributed to an increased mobility of holes due to the contribution of an intermediate germanium layer formed at the Si/SiO2 interface.

Keywords: ion implantation; germanium; SiO2

  • Fizika i Tekhnika Poluprovodnikov 41(2007)3, 301-303
  • Semiconductors 41(2007)3, 291-296

Permalink: https://www.hzdr.de/publications/Publ-11796
Publ.-Id: 11796


Transport and noise in organic field effect devices

Morawetz, K.; Gemming, S.; Luschtinetz, R.; Kunze, T.; Lipavský, P.; Eng, L. M.; Seifert, G.; Milde, P.; Pankoke, V.

The transport and fluctuation properties of organic molecules ordered parallel between two Au contact leads are investigated by the method of surface Green function. From first-principles simulation the relevant hopping parameters are extracted and used to calculate nonlinear transport coefficients with respect to an external bias voltage. A staggering of conductance is found in dependence on the number of molecules squeezed in-between the contacts. The thermal properties show an anomalous behavior whenever the voltage reaches the values of the molecular energy levels active for transport. The thermoelectric figure of merit shows a resonance allowing to reach values even larger than one.

  • Physical Review B 79(2009)085405, 1-12

Permalink: https://www.hzdr.de/publications/Publ-11795
Publ.-Id: 11795


Pattern competition in homogeneously heated fluid layers

Cartland Glover, G. M.; Generalis, S. C.

Simulations examining pattern competition have been performed on a horizontal homogeneously heated layer that is bounded by an isothermal plane above an adiabatic plane. Several different circulation patterns arose as the heating regime applied to the horizontal layer was modified. The sequence of the patterns formed as the Grashof number was increased had the following order: laminar, rolls, squares, hexagons and pentagons, pentagons and then two square modes of differing orientations. Fourier analysis was used to determine how the key modes interact with each pattern.

Keywords: Convection; Horizontal Layer; Heat Transfer; Stability

  • Open Access Logo Engineering Application of Computational Fluid Mechanics 3(2009)2, 164-174
    ISSN: 1994-2060

Permalink: https://www.hzdr.de/publications/Publ-11794
Publ.-Id: 11794


Ultra fast electron beam x-ray CT scanner for industrial process tomography

Fischer, F.; Hampel, U.; Mattausch, G.

In many industrial fields, there is a strong interest in the understanding of inner structure and transient behaviour of multi-phase flows. This is relevant for process control and optimisation in chemical industry or has influence on design of safety components in nuclear engineering, for example. The qualification of computational fluid dynamics codes dedicated to simulation of the stationary and transient flows in complex three dimensional geometries requires in-depth knowledge of the details of the real flow structure under various conditions. To extend our measurement capabilities beyond the wire mesh sensor and needle probes used so far [1], we have developed a high-speed x-ray tomography system recently [2]. This new technique offers the opportunity to perform non-intrusive flow measurements with a high frame rate and also at high temperatures and pressures. The basic principle of the system is similar to the EB CT being used in cardiac diagnostics [3]. The scanner consists of an electron beam gun with triode-type cathode system delivering up to 65 mA beam current at 150 kV acceleration voltage. Using fast electron-optical units, the electron beam is focussed onto a semicircular metal target and swept at a frequency of up to 10 kHz along the target thus producing a rapidly moving x-ray spot. A circular x-ray detector comprising 240 CZT pixels measures the x-ray power transmitted through the object which is placed in the center of the scanner head. The detector readings are recorded at a data acquisition rate of 1 MS/s and subsequently used for image reconstruction. Frame rates of up to 7.000 2D slices per second can be achieved in this way. Typical object diameters are up to 120 mm. Spatial resolution is currently in the range of 1 mm feature size but will be improved in the future.

  • Lecture (Conference)
    1st ITG International Vacuum Electronics Workshop, 10.-11.11.2008, Bad Honnef, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-11793
Publ.-Id: 11793


Air-water experiments in a vertical DN200-pipe

Beyer, M.; Lucas, D.; Kussin, J.; Schütz, P.

The extensive experimental results presented in this report provide a high-quality database for air-/water flows in a vertical pipe with a nominal diameter of 200 mm. This database can be used for the development and validation of CFD-like models for two-phase flows, e.g. for bubble coalescence and fragmentation. In particular, the investigations aim on the evolution of the two-phase flow along the pipe height. Therefore, up to 18 single measurements with varying distances between the gas injection and measurement plane were realised for each of the 92 combinations of gas and water flow rates. The pressure at the position of the activated gas injection was kept constant at 0.25 MPa(a). This boundary condition has the advantage that the measured data represent exactly the evolution of the flow along the pipe, i.e. they reflect a configuration at which the gas injection is at a fixed height position, while the measurement plane varies. Important results of this test series are time averaged radial profiles of the gas fraction, and the gas velocity, as well as the time and cross-section averaged bubble size distributions. Furthermore, gas fraction data resolved regarding the bubble size and spatial distribution are presented. As in previous test series, flow patterns were analysed, whereby the classification results from the bubble size. A substantial part of these new air/water experiments were quality and plausibility checks of the measured data. In the result, a clear and consistent trend regarding their evolution with increasing distance from the position of the gas injection was found. Comparisons of the trend of time and cross section averaged gas volume fraction along the pipe height with the theoretically expected values were carried out. The influence of the orifice diameter of the gas injection on flow patterns is also discussed in the report.
Freigabe ab 2011

Keywords: Two-phase flow; Gas bubbles; Gas volume fraction distribution; Gas velocity

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; FZD-505 2008
    ISSN: 1437-322X

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Permalink: https://www.hzdr.de/publications/Publ-11792
Publ.-Id: 11792


Luft-Wasser Experimente im vertikalen DN200-Rohr

Beyer, M.; Lucas, D.; Kussin, J.; Schütz, P.

Die im Rahmen dieser Versuchsserie erzielten umfangreichen experimentellen Ergebnisse bilden eine hochwertige Datenbasis für Luft-Wasser-Strömungen in einem vertikalen DN200-Rohr, die für die Entwicklung und Validierung von CFD-Modellen, beispielweise bzgl. Blasenkoaleszenz und -fragmentierung, genutzt werden können. Besonderes interessant ist die Untersuchung der Entwicklung der Zweiphasenströmung über der Rohrhöhe. Aus diesem Grund wurden für jede der 92 betrachteten Kombinationen aus Gas- und Wasser-Volumenstromdichten bis zu 18 Messungen mit variablen Abständen zwischen Gaseinspeisung und Messebene durchgeführt. Dabei wurde der Druck an der Gaseinspeisestelle konstant auf 0,25 MPa(a) gehalten. Diese Randbedingung bietet den Vorteil, dass die so gemessenen Daten die Entwicklung der Strömung über der Rohrhöhe widerspiegeln, d.h. eine Konfiguration beschreiben, bei der das Gas an einer festen Höhenposition eingespeist wird und die Messungen in verschiedenen darüberliegenden Ebenen erfolgen. Wesentliche Ergebnisse dieser Messserie sind radiale zeitgemittelte Profile für den Gasgehalt und die Gasgeschwindigkeit sowie zeit- und querschnittsgemittelte Blasengrößenverteilungen. Außerdem liegen blasengrößen- und ortsaufgelöste Gasgehaltsdaten vor. Wie bereits bei früheren Versuchsserien wurden auch in diesem Fall die Strömungsformen analysiert, wobei die Klassifizierung anhand der Blasengröße erfolgte. Ein wesentlicher Bestandteil dieser neuen Luft/Wasser-Versuche war die Qualitäts- und Plausibilitätsprüfung der Messdaten. Es konnte festgestellt werden, dass die Daten einen eindeutigen, widerspruchsfreien Trend bzgl. ihrer Entwicklung mit zunehmendem Abstand von der Gaseinspeisung aufweisen. Zur Plausibilitätsprüfung wurden Vergleiche des Gasgehaltsverlaufes über der Rohrhöhe mit theoretisch zu erwartenden Kurven durchgeführt. Zusätzlich zu diesen Ergebnissen enthält der Bericht eine Einschätzung des Einflusses des Bohrungsdurchmessers an der Gaseinspeisung auf die sich einstellende Strömung.
Freigabe ab 2011

Keywords: Two-phase flow; Gas bubbles; Gas volume fraction distribution; Gas velocity

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; FZD-504 2008
    ISSN: 1437-322X

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Permalink: https://www.hzdr.de/publications/Publ-11791
Publ.-Id: 11791


Miniature conductivity wire mesh sensor for gas-liquid two-phase flow measurement

Hampel, U.; Otahal, J.; Boden, S.; Beyer, M.; Schleicher, E.; Zimmermann, W.; Jícha, M.

A miniature conductivity wire mesh sensor for gas-liquid two-phase flow measurement in small channels is introduced. The sensor design is similar to the conventional wire mesh sensor for larger flow cross sections with wire electrodes stretched across the flow channel in two adjacent planes and with perpendicular wire orientation between planes. Conductivity measurement is performed by special electronics which consecutively applies bipolar voltage pulse excitation to the sender wires and measures electrical current flow in the wire crossings at the receiver wires. The new design is based on printed circuit board technology. A prototypical sensor made of 2 x 16 stainless steel wires each of 50 µm diameter was manufactured and applied to two-phase flow measurement inside the mixing chamber of an effervescent atomizer. Accuracy of the sensor was studied for static liquid distributions using microscope photography and for dynamic two-phase flow by comparison of wire mesh data with radial gas fraction profiles obtained from X-ray microtomography measurements.

Keywords: wire-mesh sensor; atomizer; two-phase flow; X-ray microtomography

Permalink: https://www.hzdr.de/publications/Publ-11790
Publ.-Id: 11790


Vacancy-type defects in 6H–silicon carbide induced by He-implantation: a positron annihilation spectroscopy approach

Zhu, C. Y.; Ling, C. C.; Brauer, G.; Anwand, W.; Skorupa, W.

Six-fold helium ion implantation was carried out on nitrogen doped n-type 6H–SiC epi samples. A box-shaped He-implantation profile and damage region was thus introduced. Vacancy-type defects in the implanted region were studied by positron annihilation spectroscopy using a monoenergetic positron beam. The average size of the vacancy-type defect detected in the as-He-implanted sample was the divacancy (V2). Thermal annealing had the effect of shrinking the defective region. Annealing at temperatures lower than 900 ◦C had the effect of removing vacancy-type defects in the defective region. While the annealing temperature is above 900 ◦C, the size of the vacancy-type defects in the defective region increased with annealing temperature. At the annealing temperature of 1600 ◦C, the defectiveregion reduced to ∼100 nm and the vacancy-type defects within the region agglomerated to clusters having an average size of 14 V2.

  • Journal of Physics D: Applied Physics 41(2008), 195304

Permalink: https://www.hzdr.de/publications/Publ-11789
Publ.-Id: 11789


Ionenstrahlen – ein Werkzeug zur Herstellung von Nanostrukturen

Schmidt, B.

Es wird ein Überblich über die Möglichkeiten des Einsatzes von Ionenstrahltechniken zur Erzeugung von Nanostrukturen sowohl auf Festkörperoberflächen als auch vergraben im Festkörper gegeben. Besonders wird dabei auf die Ionenstrahlsynthese von Nanoclustern in SiO2 und die Synthese von Nanodrähten mittels feinfokussierten Ionenstrahlen eingegangen. Zum Schluss wird die Herstellung von Si-Nanodrähten und Nano-Elektro-Mechanischen Systemen (NEMS) beschrieben, die auf der Kombination von lakaler Ga+ FIB-Implantation mit einer selektiven Ätztechnik beruht.

Keywords: ion implantation; ion beam synthesis; nanocluster; nanowire; NEMS

  • Invited lecture (Conferences)
    Internationale Fachmesse für Feinwerktechnik, Ultrapräzision, Micro- und Nanotechnologien -MiNat, MiNat Hot Spot WGL - Nanotechnologie in der Leibnizgesellschaft (WGL), 07.-08.10.2008, Stuttgart, Germany

Permalink: https://www.hzdr.de/publications/Publ-11788
Publ.-Id: 11788


Cluster growth and luminescence in ion-implanted silica

Fitting, H.-J.; Salh, R.; Kourkoutis, L.; Schmidt, B.

Scanning electron microscopy (SEM) and cathodoluminescence (CL) in
combination with scanning transmission electron microscopy (STEM) have been used
to investigate thermally grown amorphous silicon dioxide layers implanted
isoelectronically with group IV ions (C+, Si+, Ge+, Sn+, Pb+) as well as with group VI
ions (O+, S+, Se+).

Keywords: Cathodoluminescence; Silica layers; Ion implantation

  • Lecture (Conference)
    14th European Microscopy Congress, 01.-05.09.2008, Aachen, Germany
  • Contribution to proceedings
    14th European Microscopy Congress, 01.-05.09.2008, Aachen, Germany
    S. Richter, A. Schwedt (Eds.):EMC 2008, Vol. 2: Materials Science, Berlin Heidelberg: Springer-Verlag, 17-18

Permalink: https://www.hzdr.de/publications/Publ-11787
Publ.-Id: 11787


Ecological problems in Saxony related to the former uranium mining activities – fluorescence spectroscopy, a tool for analyzing the uranium binding form

Baumann, N.; Arnold, T.

As a consequence of extensive and reckless uranium mining in Eastern Germany by the Soviet mining company WISMUT between 1945 and 1990, numerous mining residues exist including important ecological problems in Saxony and Thuringia today. A main topic is washing out mobile uranium species from the rock piles and for-mer mines by surface water. It is necessary to control the pathway, the species, and the amount of migrating ura-nium compounds, and to investigate the interactions between solid mineral phases and mobile uranium species such as sorption, precipitation and forming secondary uranium minerals.
One tool for analyzing tiny amounts of U(VI) species (but also in a minor way U(IV) and U(V) species) is time-resolved laser-induced fluorescence spectroscopy (TRLFS). This method is well established in the Institute of Radiochemistry (IRC) from the Forschungszentrum Dresden-Rossendorf (FZD), especially in case of problems connected with uranium. TRLFS delivers a fluorescence signal with characteristic features in dependence of concentration and speciation of the fluorescent species in the sample. These features are the positions of the peak maxima, and, secondary, characteristic lifetimes of the signals. This technique is applicable in case of U(VI) spe-cies in water solutions, but also in case of thin U(VI) mineral coatings on solid phases.
In that lecture results of investigations of adsorbed uranium species onto mineral surfaces like from gibbsite and from muscovite are presented. Spectroscopic characterisation of several secondary uranium minerals (e.g. bolt-woodite and compreignacite) by determination of the positions of the peak maxima and the lifetimes from the TRLFS signals are presented. The spectroscopic signatures of these uranium (VI) minerals are useful for identi-fying U(VI) mineral species as colloids, as thin coatings on rocks, as minor components in soils, or as alteration products of nuclear waste. Additionally the interaction between an aqueous solution and metallic uranium was investigated by TRLFS: The identification of an ultra-thin secondary mineral film on a disk of metallic depleted uranium (DU) originated from a British tank shell, which was in contact with a phosphate containing solution, will be showed. This example demonstrates the high sensitivity of TRLFS regarding solid U(VI) phases.

Keywords: Uranium mining; U(VI); TRLFS

  • Lecture (others)
    Seminar, 27.10.2008, Hiroshima, Japan

Permalink: https://www.hzdr.de/publications/Publ-11786
Publ.-Id: 11786


Thermo-mechanische Finite-Elemente-Modellierung zur Schmelzerückhaltung im RDB nach Verlagerung von Corium in das untere Plenum Thermo-mechanical finite element modelling of in-vessel melt retention after corium relocation into the lower plenum

Altstadt, E.; Abendroth, M.; Willschütz, H.-G.

Bezüglich eines hypothetischen Kernschmelzeszenarios in einem Leichtwasserreaktor ist es notwendig, mögliche Versagensformen des Reaktordruckbehälters sowie Versagenszeiträume zu untersuchen, um die Belastung für das Containment bestimmen zu können.
Vom Institut für Sicherheitsforschung des FZD wurden Finite-Elemente-Modelle erstellt, die sowohl die Temperaturfeldberechnung für die Wand als auch die elastoplastische Mechanik der Behälterwand beschreibt. Die thermischen und mechanischen Berechnungen sind gekoppelt. Das Modell ist in der Lage, Versagenszeit und Versagensposition eines Behälters mit beheiztem Schmelzepool zu berechnen. Es existieren Modelle für die Druckwasserreaktortypen KONVOI und WWER-1000. Es wurden prototypische Szenarien mit und ohne externe Flutung des RDB untersucht, wobei die homogen und die segregierte Schmelzepoolkonfiguration betrachtet wurden. Zusätzlich wurde eine bruchmechanische Bewertung des Thermoschocks, der durch die externe Flutung entsteht, vorgenommen. Auf Grundlage der Experimente im Rahmen des ISTC-Projekts METCOR wurde außerdem die Auswirkung der thermochemischen Wechselwirkung zwischen Corium-Schmelze und RDB-Wand auf das Versagensverhalten des RDB untersucht. Das wichtigste Ergebnis ist, dass eine erfolgreiche Schmelzerückhaltung im RDB auch bei größeren Reaktoren möglich erscheint, wenn eine rechtzeitige Flutung der Reaktorgrube gelingt. Mittels einer statistischen Analyse wurden die Empfindlichkeiten von Ergebnissen gegenüber den Eingangsparametern
und die Unsicherheiten der Ergebnisse quantifiziert.

Considering the hypothetical core melt down scenario for a light water reactor (LWR) a possible failure mode of the reactor pressure vessel (RPV) and its failure time has to be investigated for a determination of the loadings on the containment. Several experiments have been performed accompanied with material properties evaluation, theoretical, and numerical work. At the Institute of Safety Research of the FZD finite element models have been developed simulating the thermal processes and the viscoplastic behaviour of the vessel wall. The thermal hydraulic and the mechanical calculations are coupled. The model is capable of evaluating fracture time and fracture position of a vessel with an internally heated melt pool. Models exist for the pressurised water reactor types KONVOI and VVER-1000. Prototypic scenarios with and without external flooding were investigated with consideration of homogeneous and segregated melt pool configurations. Additionally a fracture mechanic evaluation of the thermal shock, originating from the external flooding, was performed. Based on the experimental results of the ISTC project METCOR, the effects of the thermal chemical interaction between corium melt and vessel steel were investigated in the IVR scenarios. An important result of the project is that a successful in-vessel melt retention seems to be possible even for large reactors if the reactor pit can be filled with water before the corium melt is relocated to the lower plenum. By means of statistical analysis the sensitivity of results against input parameter variations was studied. The uncertainty of results was quantified.

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; FZD-503 2008
    ISSN: 1437-322X

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Permalink: https://www.hzdr.de/publications/Publ-11785
Publ.-Id: 11785


The immobilization of uranium in multispecies biofilms studied by microsensors and confocal microscopy

Krawczyk-Baersch, E.; Arnold, T.

Multispecies biofilms were cultured in standard culture media (Sifin; TN 1171) with a pH of approximately 7.2, and in air atmosphere condition at room temperature (20 °C). The culture media were pumped through three annular reactors for two months with a flow-rate of 15.2 ml/min, and an inner cylinder rotation speed of 14 rpm. Inside the reactors biofilms were grown on glass slides to a thickness of approximately 600 µm. Two reactors were fed with UO2(ClO4)2 to adjust the total uranium concentration in the culture medium in ecological relevant concentration (5×10-5 M and 5×10-6 M). After three weeks the cultured multispecies biofilms were used for microscopical and spectroscopical studies (CLSM) as well as for O2 microsensor studies.
Fluorescent uranium(V) and uranium(VI) particles were observed for the first time in vivo by a combined laser fluorescence spectroscopy and confocal laser scanning microscopy approach in a living multispecies biofilm grown on biotite plates. These particles ranged between 1 and 7 µm in width and up to 20 µm in length and were located at the bottom and at the edges of biofilms colonies. Anaysis of amplified 16S rRNA fragments and fluorescence in situ hybridization were used to characterize the biofilm communities. Laser fluorescence spectroscopy was used to identify these particles. The particles showed either a characteristic fluorescence spectrum in the wavelength range of 415-475 nm, indicative for uranium(V), or in the range of 480-560 nm, which is typical for uranium(VI). Particles of uranium(V) as well as uranium(VI) were simultaneously observed in the biofilms. These uranium particles were attributed for uranium(VI) to biologically mediated precipitation and for uranium(V) to redox processes taking place within the biofilms. The detection of uranium(V) in a multispecies biofilm was interpreted as a short-lived intermediate of the uranium(VI) to uranium(IV) redox reaction. Its presence clearly documents that the uranium(VI) reduction is not a two electron step but that only one electron is involved.
Concentration profiles of oxygen versus biofilm depths were measured in the biofilms by electrochemical microsensors with a tip diameter of 10µm. A motor-driven micromanipulator was used for moving downwards through the biofilm in 20 or 50µm steps. The microsensor results clearly showed that the vertical profiles of the O2 concentration within the biofilms are affected by the presence as well as by the concentration of U(VI) in the culture media. In the absence of uranium the O2 concentration in the well aerated biofilm decreased slightly. In contrast, O2 concentrations in the biofilms, which were exposed to different concentrations of uranium, decreased with increasing uranium concentration.

  • Lecture (Conference)
    4th Semi-Annual RTDC-2 Meeting of FUNMIG, 29.-30.04.2008, Larnaca, Cyprus

Permalink: https://www.hzdr.de/publications/Publ-11784
Publ.-Id: 11784


The influence of microbes on the mobility and immobilization of radionuclides e.g. U(VI) in surface and subsurface environments: A microscopical and geochemical study

Krawczyk-Baersch, E.

The effect of uranium added in ecologically relevant concentrations (1×10-5 M and 1×10-6 M) to stable multispecies biofilms was studied by electrochemical oxygen microsensors with tip diameters of 10 µm and by confocal laser scanning microscopy (CLSM). The results show the different influences of microorganisms on the migration of uranium due to redox processes taking place within biofilm. For the first time the reduction of the U(VI) to metastable U(V) by a one-electron transfer was proved by using a combination of confocal laser microscopy (CLSM) and fluorescence spectroscopy. The microsensor profile measurements in the stable multispecies biofilms exposed to uranium indicated that the bacteria in the top region of the biofilms, i.e. the metabolically most active biofilms zone, battle the toxic effects of aqueous uranium with an increased respiratory activity and high consumption rates. As analysis of the amplified 16S rRNA gene fragments showed, the addition of uranium in ecologically relevant concentrations did not change the bacterial diversity in the stable multispecies biofilms. Adaptation and detoxification mechanisms allow them to resist concentrations of toxic elements. The increased respiratory activity and high consumption rates of the microbes results in larger zones of O2 depletion in the biofilms. These zones may trigger redox processes leading to precipitation of U(IV) solids and consequently to an increased removal and immobilization of uranium from the surrounding bulk solution.

  • Invited lecture (Conferences)
    Institute Seminar, Institute of Chemistry, Cyprus University, 02.05.2008, Nicosia, Cyprus

Permalink: https://www.hzdr.de/publications/Publ-11783
Publ.-Id: 11783


The response of biofilms to uranium impacts

Krawczyk-Baersch, E.; Brockmann, S.; Arnold, T.; Hofmann, S.; Wobus, A.

The effect of uranium added in ecologically relevant concentrations (1×10-5 M and 1×10-6 M) to stable multispecies biofilms was studied by electrochemical oxygen microsensors with tip diameters of 10 µm and by confocal laser fluorescence microscopy (CLSM). The microsensor profile measurements in the stable multispecies biofilms exposed to uranium showed that the oxygen concentration decreased faster with increasing biofilm depth compared to the uranium free biofilms. In the uranium containing biofilms, the oxygen consumption, calculated from the steady-state microprofiles, showed high consumption rates of up to 61,7 nmol cm-3s-1 in the top layer (0 - 70 µm) and much lower consumption rates in the lower zone of the biofilms. Staining experiments with 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) and 4,6-diamidino-2-phenylindole (DAPI) confirmed the high respiratory activities of the bacteria in the upper layer. Analysis of the amplified 16S rRNA gene fragments showed that the addition of uranium in ecologically relevant concentrations did not change the bacterial diversity in the stable multispecies biofilms and is therefore not responsible for the different oxygen profiles in the biofilms. The fast decrease in the oxygen concentrations in the biofilm profiles showed that the bacteria in the top region of the biofilms, i.e. the metabolically most active biofilm zone, battle the toxic effects of aqueous uranium with an increased respiratory activity. This increased respiratory activity results in O2 depleted zones closer to the biofilm/air interface which may trigger uranium redox processes, since suitable redox partners, e.g. extracellular polymeric substance (EPS) and other organics (e.g. metabolites), are sufficiently available in the biofilm porewaters. Such redox reactions may lead to precipitation of uranium(IV) solids and consequently to a removal of uranium from the aqueous phase.

  • Lecture (Conference)
    7. Jenaer Sanierungskolloquium, 22.-23.09.08, Jena, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-11782
Publ.-Id: 11782


The increase of metabolic activity in biofilms caused by uranium

Krawczyk-Baersch, E.; Brockmann, S.; Arnold, T.; Wobus, A.; Diessner, S.

Most surface and subsurface environments are inhabited by microorganisms, which do not usually occur as single individual cells in nature but rather in multicellular communities called biofilms. Such biofilms attached to mineral surfaces may considerably influence the migration of toxic and/or radioactive heavy metals in contaminated environments. In our studies multispecies biofilms, which were cultured in air atmosphere on glass slides in biofilm reactors were exposed to uranium in ecologically relevant concentrations, i.e. a total U concentration of 1×10-5 mol/l and 5×10-6 M, respectively. The resulting response of the microbial biofilm community to the added uranium was studied by oxygen microsensors in biofilms. In addition staining methods such as CTC and the DNA-binding DAPI were used in combination with confocal laser microscopy (CLSM). The results reveal that the addition of uranium in ecologically relevant concentrations to stable biofilms has a strong effect on the oxygen concentration and consumption rates in biofilms due to a stimulation of the metabolism of the microbes and, consequently, on their respiratory activity and oxygen consumption. The addition of uranium (VI) in ecologically relevant concentrations (1×10-5 M and 1×10-6 M) to stable multispecies biofilms induced a fast decrease of the oxygen concentration with increasing biofilm depth, which is dependent on the uranium concentration. The microbial response to the addition of uranium occurred within two to three hours and resulted in oxygen concentration profiles similar to the profiles measured three weeks after the uranium addition.

  • Lecture (Conference)
    Biofilms III, 3rd International Conference, 06.-08.10.2008, München, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-11781
Publ.-Id: 11781


In-situ Measurements on Suspended Nanoparticles with Visible Laser Light, Infrared Light and X-rays

Zänker, H.

The presence of engineered nanoparticles (ENPs) in the water cycle is a subject of discussion amongst scientists, producers of nanomaterials, environmentalists and politicians. At this stage the influence of ENPs on the environment is still minimum and there is also hardly any experience with measuring such artificial nanoparticles within the complex matrices of environmental samples. However, there is experience with measuring natural nanoparticles in environmental waters. An overview is given on measuring methods with the focus on in-situ methods. They are aimed at studying particle size, particle size distribution, electric charge or binding type of environmental contaminants on the nanoparticles. Examples of use are given for methods such as photon correlation spectroscopy, laser-induced breakdown detection, laser Doppler velocimetry, time-resolved laser fluorescence spectroscopy, Fourier transform infrared spectroscopy and X-rax absorption spectroscopy with synchrotron radiation. The examples show the general strategies of such measurements, indicate typical problems and difficulties and demonstrate how such difficulties can be overcome.

Keywords: Nanoparticles; environmental contaminants; photon correlation spectroscopy; laser-induced breakdown detection; laser Doppler velocimetry; time-resolved laser fluorescence spectroscopy; Fourier transform infrared spectroscopy; X-rax absorption spectroscopy

  • Contribution to external collection
    Nießner, R.; Frimmel, F.H.: Nanoparticles in the Water Cycle. Properties, Analysis and Environmental Relevance., Berlin, Heidleberg, New York: Springer, 2010, 3-642-10317-0, 117-138

Permalink: https://www.hzdr.de/publications/Publ-11780
Publ.-Id: 11780


The effect of spatial discretization in LWR cell calculations with HELIOS 1.9

Merk, B.; Koch, R.

Cell and lattice calculations are the basis for all deterministic static and transient 3D full core calculations. The spatial discretization used for the cell and lattice calculations influences the results for these transport solutions significantly. The arising differences in the neutron flux distribution due to different spatial discretization are demonstrated. These differences in the flux distribution cause significant changes in the kinf value. An evaluation of the kinf value for the case of infinitely fine discretization is made. The influence of the discretization on the calculation of homogenized few group cross sections which are forwarded to the 3D full core calculations is investigated. Strategies for improving the discretization are developed and their influence on the calculation time is evaluated.

Keywords: Spatial Discretization; Neutron Transport; HELIOS; Collision Probabilities; Flat-Flux-Approximation

  • Contribution to proceedings
    18th Symposium of AER on VVER Reactor Physics and Reactor Safety, 06.-10.10.2008, Eger, Hungary
    Proceedings of the 18th Symposium of AER, 9789633726389, 257-266
  • Lecture (Conference)
    18th Symposium of AER on VVER Reactor Physics and Reactor Safety, 06.-10.10.2008, Eger, Hungary

Permalink: https://www.hzdr.de/publications/Publ-11779
Publ.-Id: 11779


Character of magnetic excitations in a quasi-one-dimensional antiferromagnet near the quantum critical points: Impact on magnetoacoustic properties

Chiatti, O.; Sytcheva, A.; Wosnitza, J.; Zherlitsyn, S.; Zvyagin, A. A.; Zapf, V. S.; Jaime, M.; Paduan-Filho, A.

We report results of magnetoacoustic studies in the quantum spin-chain magnet NiCl2-4SC(NH2)2 (DTN) having a field-induced ordered antiferromagnetic (AF) phase. In the vicinity of the quantum critical points (QCPs) the acoustic c33 mode manifests a pronounced softening accompanied by energy dissipation of the sound wave. The acoustic anomalies are traced up to T>TN, where the thermodynamic properties are determined by fermionic magnetic excitations, the “hallmark” of one-dimensional (1D) spin chains. On the other hand, as established in earlier studies, the AF phase in DTN is governed by bosonic magnetic excitations. Our results suggest the presence of a crossover from a 1D fermionic to a three-dimensional bosonic character of the magnetic excitations in DTN in the vicinity of the QCPs

  • Physical Review B 78(2008), 094406

Permalink: https://www.hzdr.de/publications/Publ-11778
Publ.-Id: 11778


Spin-zero anomaly in the magnetic quantum oscillations of a two-dimensional metal

Wosnitza, J.; Gvozdikov, V. M.; Hagel, J.; Ignatchik, O.; Bergk, B.; Meeson, P. J.; Schlueter, J. A.; Davis, H.; Winter, R. W.; Gard, G. L.

We report on an anomalous behavior of the spin-splitting zeros in the de Haas–van Alphen (dHvA) signal of a quasi-two-dimensional organic superconductor. The zeros as well as the angular dependence of the amplitude of the second harmonic deviate remarkably from the standard Lifshitz–Kosevich (LK) prediction. In contrast, the angular dependence of the fundamental dHvA amplitude as well as the spin-splitting zeros of the Shubnikov–de Haas (SdH) signal follow the LK theory. We can explain this behavior of the dHvA signal by small chemical-potential (CP) oscillations and find a very good agreement between theory and experiment. A detailed wave-shape analysis of the dHvA oscillations corroborates the existence of an oscillating CP. We discuss the absence of the above spin-zero effect in the SdH signal and argue that in k-(BEDT-TTF)2SF5CH2CF2SO3 it can be explained by an incoherent variable range hopping interlayer transport which is insensitive to the small CP oscillations.

  • Open Access Logo New Journal of Physics 10(2008), 083032

Permalink: https://www.hzdr.de/publications/Publ-11777
Publ.-Id: 11777


Spectral-history modeling in DYN3D burnup calculations

Bilodid, Y.; Mittag, S.

Reactor dynamics codes such as DYN3D use two-group cross sections (XS) which depend on local burnup, given in terms of the energy produced per fuel mass (MWd/kgHM). However, a certain burnup value can be reached under different spectral conditions depending on moderator density and other local parameters. Neglecting these spectral effects, i.e. applying the summary-burnup value only, can cause considerable errors in the calculated power density. In some cases with a high burnup the inaccuracy can reach 20%.
This paper describes a way to take into account spectral-history effects. It is shown that the respective XS correction linearly depends on the actual Pu-239 concentration. The applicability of the method was proved not only for usual uranium oxide fuel, but also for mixed uranium/plutonium oxide (MOX) and fuel assemblies with burnable absorber. A test version of an extended data library containing history coefficients was created. The code DYN3D was extended by new subroutines that calculate the actual distribution of Pu-239 in the core and apply a spectral-history correction for the cross sections.

Keywords: DYN3D; spectral-history effects; burnup history effect; burnup; cross sections

  • Contribution to proceedings
    18th AER Symposium on VVER Reactor Physics and Reactor Safety, 06.-10.10.2008, Eger, Hungary
    Proceedings of 18th AER Symposium on VVER Reactor Physics and Reactor Safety, Budapest, 978-963-372-639-6, 467-481
  • Lecture (Conference)
    18th Symposium of AER on VVER Reactor Physics and Reactor Safety, 06.-10.10.2008, Eger, Hungary

Permalink: https://www.hzdr.de/publications/Publ-11776
Publ.-Id: 11776


The importance of the intracellular glutathione pool of rape cells exposed to heavy metal stress

Viehweger, K.; Geipel, G.

Uranium is a widespread radioactive toxic heavy metal, released into the biosphere mostly by military purposes and nuclear industry. It is taken up by plant root systems and its chemical toxicity is much more dangerous than the radiological. Thus cell suspensions of rape (Brassica napus) revealed similar intracellular defence reactions after uranium exposure like it is described for other heavy metals (1).
Glutathion is one of the key players in this network, because of its ability to complex xenobiotics via the action of glutathione-S-transferase, its redox-capacity, and/or as precursor in the biosynthesis of heavy metal-binding peptides, e.g. phytochelatines.
Rape cells react with a decrease of the cytoplasmic glutathione pool, revealed by HPLC and TLC, respectively. Time-resolved laser-induced fluorescence spectroscopy (TRLFS) measurements gave an insight in interactions between glutathione and uranium. The possible reduction of the soluble uranium(VI) to an insoluble oxidation state of (IV) by glutathione can be excluded, because of lacking uranium(IV) in the cytoplasm, detected by photoacustic measurements. These findings and the time course of dropping the glutathione pool suggest an involvement in the biosynthesis of pytochelatines, which is proven by HPLC. Experiments addressing the physiological relevance of these parts of cellular defence mechanisms are under way, especially to elucidate whose impact on intracellular heavy metal sequestration.

(1) Clemens, S. (2001). "Molecular mechanisms of plant metal tolerance and homeostasis." Planta V212 (4): 475-486.

Keywords: Glutathion; uranium

  • Contribution to proceedings
    The American Society for Cell Biology 48th Annual Meeting, 13.-17.12.2008, San Francisco, USA

Permalink: https://www.hzdr.de/publications/Publ-11775
Publ.-Id: 11775


Experimental two-phase flow measurement using ultra fast limited-angle-type electron beam X-ray computed tomography

Bieberle, M.; Fischer, F.; Schleicher, E.; Koch, D.; Menz, H.-J.; Mayer, H.-G.; Hampel, U.

We report on an experimental evaluation of a novel limited-angle-type ultra fast electron beam X-ray computed tomography approach for the visualization and measurement of a gas-liquid two-phase flow. With this method a simple linear electron beam scan is used to produce radiographic views of a live two-phase flow in a pipe segment of a flow loop. Electron beam scanning can be performed very rapidly, thus a frame rate of 5 kHz is achieved. Radiographic projections are recorded by a very fast detector arc made of CZT elements. This detector records the X-ray radiation passing through the object with a sampling rate of 1 MHz. The reconstruction of slice images from the recorded detector data is a limited angle problem since in our scanning geometry the object’s Radon space is only incompletely sampled. We investigated, whether this technology is able to produce accurate gas fraction data from bubbly two-phase flow. Experiments were performed both on a Perspex phantom with known geometry and an experimental flow loop operated under vacuum conditions in an electron beam processing box.

Keywords: flow measurement; two-phase flow; electron beam tomography; X-ray tomography

Permalink: https://www.hzdr.de/publications/Publ-11774
Publ.-Id: 11774


Uranium sorption onto opalinus clay and uranium complexation with model ligands - New results.

Joseph, C.; Schmeide, K.; Sachs, S.

An anaerobic opalinus clay sample was characterized (BET, TC, TOC, CEC, XRD, IR). No significant differences between the aerobic and the anaerobic clay could be determined.
The uranium(VI) sorption onto aerobic opalinus clay (S/L = 60 g/l) in opalinus clay pore water in absence and presence of humic acid was investigated and compared with the according uranium(VI)-kaolinite sorption results.
The model ligands mandelic acid and glycolic acid were chosen for the uranium(IV) complexation. The complex formation constants for the uranium(IV) complexation were determined applying UV-Vis absorption spectroscopy. Thereby, the hydrogen ion concentration was varied.
Sulfur-containing humic acid model substances were synthesized and characterized (S-content, PEC, FTIR, XPS). First investigations of the uranium(VI) complexation of humic acid type M1-S1 were performed.

Keywords: anaerobic opalinus clay; characterization; uranium(VI); sorption; humic acid; mandelic acid; glycolic acid; U(IV)-complexation; tetravalent; synthesis

  • Lecture (others)
    5th Workshop of the joint project "Interaction and transport of actinides in natural argillaceous rock considering humic substances and clay organics", 07.-08.10.2008, Speyer, Germany

Permalink: https://www.hzdr.de/publications/Publ-11773
Publ.-Id: 11773


Pages: [1.] [2.] [3.] [4.] [5.] [6.] [7.] [8.] [9.] [10.] [11.] [12.] [13.] [14.] [15.] [16.] [17.] [18.] [19.] [20.] [21.] [22.] [23.] [24.] [25.] [26.] [27.] [28.] [29.] [30.] [31.] [32.] [33.] [34.] [35.] [36.] [37.] [38.] [39.] [40.] [41.] [42.] [43.] [44.] [45.] [46.] [47.] [48.] [49.] [50.] [51.] [52.] [53.] [54.] [55.] [56.] [57.] [58.] [59.] [60.] [61.] [62.] [63.] [64.] [65.] [66.] [67.] [68.] [69.] [70.] [71.] [72.] [73.] [74.] [75.] [76.] [77.] [78.] [79.] [80.] [81.] [82.] [83.] [84.] [85.] [86.] [87.] [88.] [89.] [90.] [91.] [92.] [93.] [94.] [95.] [96.] [97.] [98.] [99.] [100.] [101.] [102.] [103.] [104.] [105.] [106.] [107.] [108.] [109.] [110.] [111.] [112.] [113.] [114.] [115.] [116.] [117.] [118.] [119.] [120.] [121.] [122.] [123.] [124.] [125.] [126.] [127.] [128.] [129.] [130.] [131.] [132.] [133.] [134.] [135.] [136.] [137.] [138.] [139.] [140.] [141.] [142.] [143.] [144.] [145.] [146.] [147.] [148.] [149.] [150.] [151.] [152.] [153.] [154.] [155.] [156.] [157.] [158.] [159.] [160.] [161.] [162.] [163.] [164.] [165.] [166.] [167.] [168.] [169.] [170.] [171.] [172.] [173.] [174.] [175.] [176.] [177.] [178.] [179.] [180.] [181.] [182.] [183.] [184.] [185.] [186.] [187.] [188.] [189.] [190.] [191.] [192.] [193.] [194.] [195.] [196.] [197.] [198.] [199.] [200.] [201.] [202.] [203.] [204.] [205.] [206.] [207.] [208.] [209.] [210.] [211.] [212.] [213.] [214.] [215.] [216.] [217.] [218.] [219.] [220.] [221.] [222.] [223.] [224.] [225.] [226.] [227.] [228.] [229.] [230.] [231.] [232.] [233.] [234.] [235.] [236.] [237.] [238.] [239.] [240.] [241.] [242.] [243.] [244.] [245.] [246.] [247.] [248.] [249.] [250.] [251.] [252.] [253.] [254.] [255.] [256.] [257.] [258.] [259.] [260.] [261.] [262.] [263.] [264.] [265.] [266.] [267.] [268.] [269.] [270.] [271.] [272.] [273.] [274.] [275.] [276.] [277.] [278.] [279.] [280.] [281.] [282.] [283.] [284.] [285.] [286.] [287.] [288.] [289.] [290.] [291.] [292.] [293.] [294.] [295.] [296.] [297.] [298.] [299.] [300.] [301.] [302.] [303.] [304.] [305.] [306.] [307.] [308.] [309.] [310.] [311.] [312.] [313.] [314.] [315.] [316.] [317.] [318.] [319.] [320.] [321.] [322.] [323.] [324.] [325.] [326.] [327.] [328.] [329.] [330.] [331.] [332.] [333.] [334.] [335.] [336.] [337.] [338.] [339.] [340.] [341.] [342.] [343.] [344.] [345.] [346.] [347.] [348.] [349.]