Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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31738 Publications
Östrogennachweis in wässrigen Lösungen mit Hilfe Silzium-basierter Lichtemitter
Cherkouk, C.;
In dieser Arbeit wurde ein Sensorkonzept mit Hilfe der Si-basierten Lichtemitter (MOSLED) zum Östrogennachweis in wässrigen Lösungen entwickelt. Das Sensorkonzept basiert auf einer direkten Fluoreszenzanalyse und besteht aus der Anordnung der Bio-Komponenten und dem Verfahren zu ihrer Herstellung sowie dem eigentlichen Meßverfahren. Die Anordnung besteht aus drei Teilen: die Funktionalisierung der MOSLED-Oberfläche, die Immobilisierung des hER-Rezeptors und die Herstellung der Referenzlösung. Den Schwerpunkt dieser Arbeit bildet die Ausführung dieser drei Teile.
Die Funktionalisierung der SiO2-Oberfläche der MOSLED wurde mit Hilfe eines im Rahmen dieser Arbeit entwickelten SSC (Spraying Spin Coating)- Verfahrens realisiert. Die Ausgangsmaterialien dieses Verfahrens sind organofunktionelle Silangruppen mit drei unterschiedlichen funktionellen Gruppen, nämlich die Amino-, Carboxyl- und die Thiolgruppen. Die Optimierung dieser Methode erfolgte mittels der zwei Silangruppen APMS ((3- Aminopropyl)trimethoxysilane und Triamino-APMS (N-[3-(Trimethoxysilyl)propyl]ethylenediamine mit der gleichen Molekülstruktur, aber mit einer unterschiedlichen Anzahl an funktionellen Gruppen. Diese Resultate wurden mit in der Literatur beschriebenen Verfahren verglichen. Die Optimierung der SSC-Methode wurde zuerst auf einfache SiO2-Oberflächen und dann auf der Oberfläche der MOSLED angewendet. Die Proben wurden mit Hilfe üblicher Methoden der Oberflächenphysik- wie FTIR-, Raman- und XPS-Spektroskopie untersucht.Die Oberflächenrauhigkeit wurde mittels AFM-Spektroskopie ermittelt, deren Aufnahmen eine glatte Oberfläche bei den mit der SSC-Methode silanisierten Proben zeigen. Während die Hydrophobizität der funktionalisierten SiO2-Oberflächen zunimmt, sinkt dabei die Oberflächenenergie, welche die Anbindung eines hER-Rezeptors mit großer Bindungsenergie begünstigt. Zur Immobilisierung des hER-Rezeptors wurde dieser erst an das Hüllenmolekül des QDots R-655-Farbstoffs gebunden und anschließend an der SSC-silanisierten SiO2-Oberflächen adsorbiert. Der Anteil der immobilisierten Rezeptoren wurde mittels PL-Messung kontrolliert.
Eine andere Immobilisierungstrategie des hER-Rezeptors an die SiO2-Oberfläche kann mit Hilfe eines Aminosäure-Derivates um den Rezeptor realisiert werden. Eine Adsorption der Lysinaminosäure an die SSC-APMS silanisierten SiO2- Oberflächen als Funktion des pH-Wertes wurde durchgeführt, und der Adsorbatsanteil des Lysins mittels XPS-Messung durch die Bindungsenergien der Energieniveaus C1s und N1s berechnet. Eine Referenzlösung mit QDots R 800-Farbstoff markierten Östrogenmolekülen kommt zum Einsatz. Dabei wird die Position 17 des β-Estradiolmoleküls, welches mit einem N-Hydroxysuccinimide Derivat versehen ist, an das Hüllenmolekül des QDots R 800-Farbstoff gebunden,sodass der Phenolring des β-Estradiols frei bleibt. Insbesondere ist bei den FTIR-Spektren
eine nichtgebunden OH-Gruppe des β-Estradiolmoleküls gut erkennbar. Das gesamte Sensorkonzept wurde an zwei mit Östrogen mit einer Konzentration von 1mM und 1μM versetzten Wasserproben getestet. Die Anordnung der Bio-Komponenten wurde mittels PL nachgewiesen. Der Östrogennachweis wurde mit Hilfe des Ge- und Tb-basierten Lichtemitters demonstriert.
  • Open Access LogoWissenschaftlich-Technische Berichte / Forschungszentrum Dresden-Rossendorf; FZD-542 2010

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Publ.-Id: 14778 - Permalink


Ultrafast and nonlinear terahertz spectroscopy of semiconductor quantum structures
Schneider, H.;
This seminar gives an overview on our recent experimental studies involving terahertz (THz) radiation from photoconducting antennae and from the free-electron laser in Dresden, Germany. In particular, microstructured scalable antennae for photoconductive THz emitters and semiconductor quantum well detectors for quadratic autocorrelation of pulsed THz radiation will be discussed. The final part of my talk will concentrate on nonlinear THz spectroscopy, in particular THz sideband generation and coherent dynamics of excitons dressed by strong THz beams.
Keywords: two-photon absorption, quadratic autocorrelation, terahertz spectroscopy
  • Lecture (others)
    Condensed Matter Physics Colloquium, 21.09.2010, Hefei, China

Publ.-Id: 14777 - Permalink


Two-photon quantum well infrared photodetectors for terahertz autocorrelation
Schneider, H.; Winnerl, S.; Drachenko, O.; Helm, M.; Liu, H. C.; Walther, M.; Faist, J.;
Two-photon quantum well infrared photodetectors (QWIPs) are based on quantum wells comprising three energetically equidistant states, namely two bound subbands and one resonant state in the continuum. This configuration is extremely efficient for two-photon transitions, giving rise to strong resonant enhancement and to optical nonlinearities which are six orders of magnitude stronger than in bulk crystals. Using this approach, extremely sensitive quadratic detectors for mid-infrared and THz radiation can thus be realized. These devices are very useful for quadratic autocorrelation measurements of THz radiation from free-electron lasers, nonlinear optical converters, and modelocked quantum cascade lasers.
Exploiting the two-photon QWIP approach, we have investigated various detectors based on different epitaxial structures, covering operation wavelengths from the mid-wavelength infrared to the THz regime. In particular, we have demonstrated a two-photon QWIP which operates below the Reststrahlen band at 42 μm (7.1 THz) [1]. At shorter wavelengths, quadratic detection also works at higher temperatures, which is crucial for applications in practical systems. In particular, room temperature operation has been achieved at 5.5 μm (54.5 THz) [2].
In this talk, we will concentrate on the detection properties of two-photon QWIPs. We confirm their quadratic intensity dependence and demonstrate autocorrelation measurements and pulse monitoring of far-infrared picosecond pulses from the free-electron laser at the Forschungszentrum Dresden Rossendorf. Huge optical nonlinearities allow for quadratic detection at THz pulse energies as low as a few pJ. The time resolution of this detector is limited by the intersubband dynamics associated with the intermediate state. Besides applications in THz pulse diagnostics, the two-photon QWIP thus also provides interesting opportunities for studies of the associated intersubband population and polarization lifetimes.
[1] H. Schneider, H. C. Liu, S. Winnerl, C. Y. Song, M. Walther, M. Helm, Opt. Express 17, 12279 (2009)
[2] H. Schneider, H. C. Liu, S. Winnerl, O. Drachenko, M. Helm, J. Faist, Appl. Phys. Lett. 93, 101114 (2008)
Keywords: Quantum well infrared photodetector, QWIP, terahertz, autocorrelation
  • Invited lecture (Conferences)
    5th International Symposium on Ultrafast Phenomena & Terahertz Waves (ISUPTW'2010), 12.-16.09.2010, Xi'an, China

Publ.-Id: 14776 - Permalink


Hydrogen desorption kinetics of melt-spun and hydrogenated Mg90Ni10 and Mg80Ni10Y10 using in-situ synchrotron X-ray diffraction and thermogravimetry
Kalinichenka, S.; Roentzsch, L.; Baehtz, C.; Kieback, B.;
Two nanocrystalline magnesium-rich alloys, Mg90Ni10 and Mg80Ni10Y10, were produced by meltspinning. After hydrogenation they consist of a MgH2 matrix with finely dispersed Mg2NiH4 grains of about 2m in size. In the case of Mg80Ni10Y10, nanocrystalline YH3 grains are found, additionally. The desorption kinetics of hydrogenated Mg90Ni10 and Mg80Ni10Y10 was investigated by thermogravimetry at different temperatures in the range from 150°C to 250°C. It was observed that Mg80Ni10Y10 exhibits a much faster desorption kinetics in comparison toMg90Ni10 of up to 1.3 wt.%H2/min. Differential scanning calorimetry indicates that these alloys undergo a two-step desorption process. The corresponding phase transformations were investigated in detail by in situ synchrotron X-ray diffraction, thus, the different hydrogen desorption kinetics can be explained.
Keywords: Hydrogen storage Lightweight metal hydrides Mg-rich alloys Melt-spinning X-ray diffraction Synchrotron radiation

Publ.-Id: 14775 - Permalink


Longitudinal THz electric fields in the focus of radially polarized beams
Winnerl, S.; Hubrich, R.; Peter, F.; Helm, M.; Schneider, H.;
While typical pulsed terahertz (THz) systems operate with freely propagating THz waves of linear polarization and Gaussian beam profile, modes of different polarization can also be attractive. In particular, radially polarized beams exhibit longitudinal fields at the focus and smaller spot sizes as compared to linearly polarized beams. These key properties of radially polarized beams have been demonstrated indirectly for visible light [1]. Recently radially polarized single cycle THz beams have been generated by velocity-mismatched optical rectification [2] and photoconductive antennas [3,4]. However, longitudinal THz fields have been observed so far only in the near field of plasmon-polariton excitations in a metal tip [5].

We report on longitudinal THz fields in the focus of freely propagating waves. Single cycle THz pulses with radial polarization are generated by photoexcitation of emitters with an electrode structure consisting of concentric rings [4]. By means of electro-optic detection we determine the phase relation between transverse and longitudinal field components. The radiation is focused onto ZnTe sensing crystals oriented along the (110) and (100) axis, respectively, in order to detect transverse and longitudinal THz fields. While the THz beam is kept fixed, the electro-optic detection system is scanned along the x-axis, which denotes the horizontal direction perpendicular to the axis of propagation. For comparison, emitters for linearly polarized beams are operated under the same conditions.

The transverse field changes sign, as the detector is moved across the propagation axis located at x = 0, as expected for a radially polarized wave. The longitudinal field, however, is located around the propagation axis and does not change sign as x changes from negative to positive. At t = 0 where the transverse fields exhibits extrema (dashed line), the longitudinal field is zero. This phase difference of pi/2 has been predicted theoretically as a consequence of Maxwell’s equation div E = 0. To our knowledge, this phase relation has not been measured previously in the entire range of the electromagnetic spectrum. Furthermore we show that the spot size of the longitudinal component is smaller than the diffraction limited spot of a linearly polarized THz beam. The results are analyzed by calculations based on the vector Helmholtz equation beyond the paraxial approximation.

[1] R. Dorn, S. Quabis, G. Leuchs, Sharper focus for a radially polarized light beam, Phys. Rev. Lett. 91, 233901 (2003).
[2] G. Chang, Ch.J. Divin, C.-H. Liu, S.L. Williamson, A. Galvanauskas, T.B. Norris, Generation of radially polarized terahertz pulses via velocity-mismatched optical rectification, Opt. Lett. 32, 433 (2006).
[3] J.A. Deibel, K. Wang, M.D. Escarra, D. Mittleman, Enhanced coupling of terahertz radiation to cylindrical wire waveguides, Opt. Express. 14, 279 (2006).
[4] S. Winnerl, B. Zimmermann, F. Peter, H. Schneider, M. Helm, Thz Bessel-Gauss beams of radial and azimuthal polarization from microstructured photoconductive antennas, Opt. Express 17, 1571 (2009).
[5] N.C.J. van der Valk and P.C.M. Planken, Electro-optic detection of subwavelength terahertz spot sizes in the near field of a metal tip, Appl. Phys. Lett. 81, 1558 (2002).
Keywords: terahertz waves, longitudinal and azimuthal fields, radial polarization
  • Lecture (Conference)
    5th International Symposium on Ultrafast Phenomena & Terahertz Waves (ISUPTW'2010), 12.-16.09.2010, Xi'an, China

Publ.-Id: 14774 - Permalink


Aqueous uranyl benzoate species characterized by different spectroscopic techniques
Frost, L.; Moll, H.; Bernhard, G.;
In this study UV-vis spectroscopy as well as RT and cryo time-resolved laser-induced fluorescence spectroscopy (TRLFS) were applied to reinvestigate the complexation of uranium(VI) by benzoic acid (BA). For the first time in the liquid phase the existence of a U(VI)-BA complex with a 1:2 stoichiometry could be proven.
RT TRLFS measurements revealed a static as well as a dynamic ligand-initiated quench process in the U(VI)-BA system. At these conditions no luminescence emission resulting from complex formation was found. Consequently cryo TRLFS was applied to increase the maximum detect-able BA:U(VI) ratio. By this for the first time a lumines-cence spectrum of the 1:2 U(VI)-BA complex could be determined. This species is characterized by emission bands at 467, 485, 505, 526, and 550 nm which are blue-shifted compared to the ones of the uranyl ion. The luminescence lifetime of the 1:2 complex amounts to 9.21 ± 0.01 µs at -18°C compared to 150.4 ± 0.5 µs for uranyl.
Stability constants of both, the 1:1 and the 1:2 species, have been calculated to be log β110 = 2.66 ± 0.18 and log β120 = 4.48 ± 0.24, respectively. UV-vis spectroscopy combined with factor analysis yielded the molar absorption spectrum of the 1:2 U(VI)-BA species which is characterized by absorption bands at 406, 418, 432.5, 447, and 461 nm and a molar absorption coefficient of 22 L•mol-1•cm-1.
Keywords: Uranium, Benzoic Acid, Complexation, UV-vis spectroscopy, Cryo TRLFS

Publ.-Id: 14773 - Permalink


Electromagnetic inspection of a two-phase flow of GaInSn and Argon
Terzija, N.; Yin, W.; Gerbeth, G.; Stefani, F.; Timmel, K.; Wondrak, T.; Peyton, A.;
In the continuous casting process, an adequate control of liquid steel flow through the submerged entry nozzle is essential for maintaining steel cleanliness and ensuring good surface quality in downstream processing. Monitoring the flow in the nozzle presents a challenge for the instrumentation system because of the high temperature environment and the limited access to the nozzle in between the tundish and the mould.
In this paper, the distribution of a two-phase liquid metal/gas flow is studied by using a liquid metal laboratory model of an industrial steel caster and an inductive sensor array. The experiments were performed with the liquid eutectic alloy GaInSn as an analogue for liquid steel, which has similar conductive properties as molten steel and allows the measurements at room temperature. A scaled (approx. 1:10) experimental rig consisting of a tundish, a stopper rod, a nozzle and a mould was used. Argon gas was injected through the centre of the stopper rod and the behavior of two phase GaInSn/Argon flows was studied.
The electromagnetic system used in the experiments to monitor the behavior of two phase GaInSn/Argon flows consists of an array of 8 equally spaced inductive coils arranged around the object, a data acquisition system and a host computer. The present system operates at 10 kHz and has a capture rate of 10 frames per second.
The results show clearly that the injection of the Argon gas is distinguishable from the single phase flow by observing the appearance of oscillation patterns. These oscillations become more dominant with the increase of the Argon flow. In some cases two main oscillation patterns were present in the raw signals. In general, the signals and the reconstructed void fractions in the nozzles are highly correlated with the observed oscillations of the level height in the mould and the pressure in the nozzle.

Publ.-Id: 14772 - Permalink


Ternary uranium(VI) carbonato humate complex studied by cryo-TRLFS
Steudtner, R.; Sachs, S.; Schmeide, K.; Brendler, V.; Bernhard, G.;
The complex formation of U(VI) with humic acid (HA) in the presence of carbonate was studied by time-resolved laser-induced fluorescence spectroscopy at low temperature (cryo-TRLFS) at pH 8.5. In the prescence of HA, a decrease of the luminescence intensity of U(VI) and no shift of the emission band maxima in compari-son to the luminescence spectrum of the UO2(CO3)34- complex, the dominating U(VI) species under the applied experimental conditions in the absence of HA, was observed. The formation of a ternary U(VI) carbonato hu-mate complex of the type UO2(CO3)2HA(II)4− starting from UO2(CO3)34- was calculated from the luminescence data. A complex stability constant of log K = 2.83 ± 0.17 was determined and the result of the slope analysis with a slope of 1.12 ± 0.11 verifies the postulated complex reaction. These results agrees very well with literature data. Speciation calculations show, that the formation of the ternary U(VI) carbonato humate complex can significantly influence the U(VI) speciation under environmental conditions.
Keywords: Uranium(VI), Humic acid, Carbonate, Complexation, Ternary complex, cryo-TRLFS

Publ.-Id: 14771 - Permalink


P0902 - Anordnung zur Elektronenstrahltomographie
Hampel, U.;
Aufgabe der vorliegenden Erfindung ist es, eine Anordnung zur Elektronenstrahltomographie anzugeben, die eine kontinuierliche und gleichzeitige Aufnahme zweidimensionaler Schnittbilder eines Objektes in verschiedenen Durchstrahlungsebenen mit hoher zeitlicher und räumlicher Auflösung gestattet.
Die Erfindung beinhaltet, dass die Targets (5) von Öffnungen (14) gegebener Breite und regelmäßiger Anordnung in Umfangsrichtung durchbrochen sind, wobei die Öffnungen (14) in den Targets (5) jeweils auf einer Bahnkurve liegen, die den Schnitt der Mantelfläche des Elektronenstrahlkegels (11) mit dem jeweiligen Target (5) bilden; die in Strahlrichtung aufeinanderfolgenden Targets (5) mit jeweils einem kleinen Winkelversatz zum davorliegenden Target (5) bezüglich der optischen Achse (10) angeordnet sind, so dass ein entlang der Mantelfläche des Elektronenstrahlkegels (11) zirkulierender Elektronenstrahl (4) mit mindestens einem Teil seines Querschnitts nacheinander die Materialstege (15) zwischen den Öffnungen (14) aller Targets (5) bestrahlt und zu jedem Target (5) ein Röntgendetektorbogen (6) koplanar radial vor oder hinter dem jeweiligen Target (5) angeordnet ist.
  • Patent
    Anmeldung: DE 10 2009 002 114 A1 14.10.2010
  • Patent
    EP 2238908 B1 - 24.08.2011
  • Patent
    DE 102009002114B4 - 15.03.2012
  • Patent
    US 8130899B2 - 06.03.2012

Publ.-Id: 14770 - Permalink


Große Laufwasserkraftwerke im Einzugsgebiet der Elbe
Rindelhardt, U.;
In Deutschland ist die Grenze zwischen großen und kleinen Wasserkraftanlagen (WKA) bei einer Generator-Leistung von 1 MW festgelegt. Die vorliegende Untersuchung stellt den aktuellen Stand der großen WKA im deutschen Elbe-Einzugsgebiet dar. An der Elbe selbst bestehen heute keine Voraussetzungen (Staustufen) für die Nutzung der erheblichen Wasserkräfte (etwa 1 TWh/a). Die 31 an den Nebenflüssen der Elbe bestehenden WKA haben eine Leistung von insgesamt etwa 59 MW, wovon 50 MW etwa zu gleichen Teilen auf die Flussgebiete der Saale und der Mulde entfallen. Neubaumöglichkeiten für weitere WKA an bestehenden Stauanlagen mit einer Leistung von 6 bis 8 MW werden derzeit untersucht.
Keywords: hydropower, Elbe river
  • Wasserwirtschaft 101(2011)3, 31-36

Publ.-Id: 14769 - Permalink


Activation study of the 40Ca(alpha,gamma)44Ti reaction at the Dresden Felsenkeller
Bemmerer, D.;
The strength of selected resonances in the 40Ca(alpha,gamma)44Ti reaction is studied by activation, using the Felsenkeller low-level gamma-counting facility. In addition, the background conditions for possible accelerator experiments inside Felsenkeller are reviewed.
  • Lecture (Conference)
    10th Meeting Collaboration of European Low-level Underground Laboratories (CELLAR), 14.-15.10.2010, Dresden, Deutschland

Publ.-Id: 14768 - Permalink


Anisotropic magneto-optical response of metallic thin films probed by Vector-Magneto-Optical Generalized Ellipsometry
Mok, K. M.; Du, N.; Schmidt, H.;
Magneto-optical generalized ellipsometry is the most general approach to characterize the magneto-optical response of materials. We extended this experimental approach to Vector-Magneto-Optical Generalized Ellipsometry (VMOGE) in the IR-UV spectral range, by constructing a generalized spectroscopic ellipsometer combined with a 3D vector magnet. VMOGE measures the upper 3 x 4 submatrix of the 4 x 4 Mueller matrix in a magnetic field of arbitrary orientation and magnitude up to 0.4 T at room temperature. Searching the best match model between experimental and calculated VMOGE data, the complex-valued magneto-optical dielectric tensor ε MO is determined. Comparison with vector magnetometry measurements can provide the complex and anisotropic magneto-optical coupling constant Qx, Qy, Qz. We have determined the wavelength dependence of the isotropic Qx and Qy of ferromagnetic Co, Fe, and Ni films. Besides, VMOGE is also employed to study Co nanowires with very strong anisotropic optical response. Having knowledge of the magneto-optical coupling constant Q(λ), one can design magneto-optical devices, e.g., ferromagnetic thin film and nanowire structures, with a strong magneto-optical response for a selected wavelength.
Keywords: Magneto optics, Mueller matrix, generalized ellipsometry, dielectric tensor, ferromagnetism, magnetic anisotropy, nanowires
  • Lecture (Conference)
    3rd NanoCharm Workshop on Non-Destructive Real Time Process Control, 13.-15.10.2010, Berlin, Germany
  • Lecture (Conference)
    Trends in Spintronics and Nanomagnetism (TSN-2010), 24.-28.05.2010, Lecce, Italy

Publ.-Id: 14767 - Permalink


Optimization of the pulp process regarding energy efficiency and fibre pulp quality
Mäbert, M.; Bieberle, A.; Krug, D.; Hampel, U.;
Zur Herstellung von Mitteldichten Faserplatten (MDF) werden Holzfasern definierter Qualität benötigt. Für die Prozess- und Energieoptimierung soll die Holzfaserverteilung im Laborrefiner des Institut für Holztechnologie Dresden gGmbH (IHD) erfasst werden.
Keywords: Refiner, MDF-Plattenherstellung, Faserstoffproduktion
  • Lecture (Conference)
    7th European Wood-based Panel Symposium, 13.-15.10.10, Hannover, Deutschland

Publ.-Id: 14766 - Permalink


Spatial Resolution of Thin-Walled High-Pressure Drift Tubes
Davkov, V. I.; Gregor, I.; Haas, D.; Mouraviev, S. V.; Myalkovskiy, V. V.; Naumann, L.; Peshekhonov, V. D.; Rembser, C.; Rufanov, I. А.; Russakovich, N. А.; Senger, P.; Smirnov, S. Y.; Tikhomirov, V. O.;
A small prototype detector based on high pressure thin-walled tubes (straws) has been developed and its parameters have been studied on a bench at JINR, Dubna, and SPS at CERN. The inner diameter of the straws is 9.53 mm. The pressure of the active gas mixture Ar/CO2 (80/20) has been varied from 1 to 5 bar. The best spatial resolution achieved in this pressure range is ~40 μm. Both the high efficiency and high rate capability are retained.
Keywords: Coordinate Detector; High Pressure; Thin-Walled Drift Tube; Straw; Spatial Resolution

Publ.-Id: 14765 - Permalink


Influence of humic acid on the Am(III) sorption onto kaolinite
Krepelova, A.; Sachs, S.; Bernhard, G.;
The sorption of americium(III), (Am(III)), onto kaolinite was studied in batch experiments in the absence and presence of humic acid (HA) ([Am(III)]0 = 1x10-6 M, [HA]0 = 0 or 10 mg/L, I = 0.01 M NaClO4, pH = 3–10, pCO2 = 10-3.5 atm, solid-to-liquid ratio (S/L) = 1 or 4 g/L). The results show that the Am(III) sorption onto kaolinite is influenced by S/L, the presence of HA and the pH value. In the absence of HA, Am(III) exhibits a very strong and almost pH independent sorption onto kaolinite at the S/L ratio of 4 g/L. In the presence of HA, there are small differences in the Am(III) sorption compared to the HA free system. At pH values < 5, HA very slightly enhances the sorption of Am(III). Conversely, at pH values ≥ 5.5, the presence of HA decreases the sorption of Am(III) due to the formation of dissolved Am(III) humate complexes. The decrease of S/L from 4 to 1 g/L has a significant effect on the Am(III) sorption onto kaolinite. A sorption edge occurs at pH 6 and the influence of carbonate on the Am(III) sorption at higher pH values becomes evident. Furthermore, the influence of HA on the Am(III) sorption onto kaolinite is more pronounced. The Am(III) sorption results are compared to literature and to those of U(VI) sorption onto kaolinite obtained under the same experimental conditions.
Keywords: Americium, Kaolinite, Humic Acid, Sorption, Clay

Publ.-Id: 14764 - Permalink


Alteration of magnetic anisotropy of Pt/Co/Pt trilayers by FIB irradiation
Mazalski, P.; Dobrogowski, W.; Maziewski, A.; Sveklo, I.; Fritzsche, M.; Liedke, M. O.; Fassbender, J.ORC; Wawro, A.; Baczewski, L. T.
Ion beam irradiation enables to modify magnetic properties of magnetic ultrathin films and multilayers [1, 2]. Such a method is a very promising technique for magnetic patterning [3]. In films with initial perpendicular magnetization the decrease of perpendicular magnetic anisotropy, followed by the magnetization rotation to the in-plane orientation and finally a transition to superparamagnetic state has been observed with increasing irradiation dose D [1-3]. Recently a double magnetisation reorientation from in-plane to out-of-plane direction and back to in-plane alignment, driven by Ga+ ion 30 keV irradiation, has been observed in sputtered Pt/(Co 2.6 nm)/Pt films [4].
In this work we report the influence of focused ion beam (FIB) irradiation on magnetic properties of MBE grown Mo/Pt/(Co 3.3nm)/Pt sandwiches. In the as deposited sample magnetization was aligned in the film plane. The numerous areas of the sample (squares 100x100μm² or 50x50μm²) have been irradiated by Ga+ ions with doses D ranging between 2x1012 and 1x1016 ions/cm². A development of perpendicular magnetic anisotropy in irradiated regions has been correlated with modifications of a surface morphology using polar Kerr effect magnetometry (sensitive to perpendicular magnetization component), as well as atomic/magnetic force microscopy techniques.

[1] C. Chappert, H. Bernas, et al., Science 280, 1919 (1998).
[2] J. Fassbender, J. McCord, J. Magn. Magn. Mat. 320, 579 (2008).
[3] J. Ferré, J.-P. Jamet, in Handbook of Magnetism and Advanced Magnetic Materials, Vol. 3, p.1710 H. Kronmüller, S. Parkin Ed. (John Wiley & Sons, Ltd, 2007).
[4] J.Jaworowicz et al., APL 95, 022502 (2009).
  • Poster
    NANOSMAT 2010, 19.-21.10.2010, Reims, France

Publ.-Id: 14763 - Permalink


Preparation and characterization of 90Y- and 177Lu-labeled cetuximab for therapeutic applications in vitro and in vivo
Zenker, M.; Bergmann, R.; Walther, M.; Heldt, J.-M.; Pietzsch, J.; Pietzsch, H.-J.; Steinbach, J.;
Cetuximab (C225) as a chimeric monoclonal antibody specifically targets the epidermal growth factor receptor (EGFR) that is often overexpressed in human malignancies. This phenotype is associated with tumor aggressiveness, treatment
resistance and biological heterogeneity with potential to bypass the blockade of the EGFR signaling pathways.
The aim of this work was to modify the C225 for radiolabeling with therapeutic radionuclides like 90Y and 177Lu as a prerequisite for combination of endoradionuclide therapy with antibody-, chemo- or external radiation therapy for routine application.
C225 was conjugated with the bifunctional chelator CHX-A″-DTPA up to a molar DTPA to C225 ratio of 5. The EGFR-affinity of the immunoconjugate resulted in 94% versus 100% of the unmodified C225 measured with enzyme-linked immunosorbent assay on EGFR-positive tumor cell line A431. DTPA-C225 was labeled with 90YCl3 or 177LuCl3 within 30 min with a radiolabeling yield of N95%. The radio-immunoconjugates exhibited high accumulation in squamous cell carcinoma xenotransplanted tumors shown by single photon emission computed tomography and autoradiography. The radiolabeled C225 can be produced in routine with high avidity and specific activity as prerequisite for long term preclinical therapeutic studies.
  • Poster
    International Symposium on Technetium and other Radiometals in Chemistry and Medicine, 08.-11.09.2010, Bressanone, Italy
  • Abstract in refereed journal
    Nuclear Medicine and Biology 37(2010)6, 723
    DOI: 10.1016/j.nulmedbio.2010.04.053
  • Contribution to external collection
    Ulderico Mazzi, William V. Eckelman, Wynn A. Volkert: Technetium and Other Radiometals in Chemistry and Medicine, Padova: SGEditoriali, 2010, 553-554

Publ.-Id: 14762 - Permalink


Cu-61 production and purification
Thieme, S.; Walther, M.; Pietzsch, H.-J.; Steinbach, J.;
Cu-61 (T1/2=3.32 h, Eβ+=1.22 MeV 60%) is a positron emitter from the set of medically useful copper radioisotopes. Its nuclear properties and ease of production make it suitable for positron emission tomography imaging. The 64Zn (p,α)61Cu reaction with enriched Zn-64 as target material seems to be more convenient for the routine production of Cu-61 than the 61Ni(p,n)61Cu route, due to the higher costs of enriched Ni-61. As reported, the 64Zn(p,α)61Cu reaction delivers adequate yields of Cu-61 in an energy window of 19à10MeV with low contaminants like Cu-60/62 which occur at higher proton energies.
Cu-61 was generated using the 64Zn(p,α)61Cu reaction utilizing 16 MeV. For the purification of Cu-61, a system of cation- and anion-exchange columns was applied which allows recycling of the target material for uncomplicated electro deposition for the next irradiation cycle. The abandonment of heating and drying steps, applying pumps or any pressure to the columns makes this process suitable for remote handling in hot cells and causing fewer sources of contaminants and enables good/reasonable yields. An overview of the key data (yield at EOB and after processing, specific activity and radiochemical purity) will be presented.
  • Abstract in refereed journal
    Nuclear Medicine and Biology 37(2010)6, 719
    DOI: 10.1016/j.nulmedbio.2010.04.049
  • Contribution to external collection
    Ulderico Mazzi, William V. Eckelman, Wynn A. Volkert: Technetium and Other Radiometals in Chemistry and Medicine, Padova: SGEditoriali, 2010, 475-478
  • Lecture (Conference)
    International Symposium on Technetium and other Radiometals in Chemistry and Medicine, 08.-11.09.2010, Bressanone, Italy

Publ.-Id: 14761 - Permalink


[188Re(N)(cys∼)(PNP)]+/0 mixed ligand compounds as models for target specific agents
Bolzati, C.; Thieme, S.; Agostini, S.; Carta, D.; Salvarese, N.; Refosco, F.; Bergmann, R.; Pietzsch, J.; Pietzsch, H.-J.;
An efficient procedure for the preparation of [188Re(N)(PNP)]-based complexes is reported. The radiochemical yield (RCY) of the compounds was optimized considering reaction parameters such as: nature of nitrido nitrogen donors, reaction times and pH.
The chemical identity of 188Re-agents was determined by high-performance liquid chromatography comparison with the corresponding well characterized cold Re-compounds. The stability of the [188Re(N)(PNP)] complexes toward transchelation with glutathione and degradation by serum enzymes was assessed. The clearance of selected radiolabeled agents from normal tissues was evaluated in rats.
[188Re(N)(cys∼)(PNP)]+/0 asymmetrical compounds were prepared in aqueous solution from perrhenate using a multistep procedure based on the preliminary formation of the labile 188ReIIIEDTA species which easily undergo to oxidation/ligand exchange reaction to afford in presence of DTCZ the [188ReV≡N]2+core. The final compounds were obtained by adding to the [188ReV≡N]int 2+ the two bidentate ligands. However, a relative high amount of cys∼ ligand was required to obtain a quantitative RCY. The complexes were stable toward reoxidation to perrhenate and ligand exchange reactions. In vivo studies showed a rapid distribution and elimination of the complexes from the body. No specific uptakes in radiation sensitive tissues/organs were detected.
A positive correlation of the distribution of the complexes estimated with biodistribution studies (% injected dose) andwithmicro-single photon emission computed tomography semiquantification imaging analysis was observed. The low labeling efficiency limits but not excludes the possibility to apply [188Re(N)(PNP)]-technology to the preparation of target specific radiotherapeutical agents.
  • Poster
    International Symposium on Technetium and other Radiometals in Chemistry and Medicine, 08.-11.09.2010, Bressanone, Italy
  • Abstract in refereed journal
    Nuclear Medicine and Biology 37(2010)6, 711-712
    DOI: 10.1016/j.nulmedbio.2010.04.001
  • Contribution to external collection
    Ulderico Mazzi, William V. Eckelman, Wynn A. Volkert: Technetium and Other Radiometals in Chemistry and Medicine, Padova: SGEditoriali, 2010, 407-408

Publ.-Id: 14760 - Permalink


Radiolabeled L-oligonucleotides with tunable pharmacokinetics — a suitable complementary system for pretargeting technologies
Förster, C.; Bergmann, R.; Schubert, M.; Walther, M.; Pietzsch, J.; Vonhoff, S.; Klussmann, S.; Pietzsch, H.-J.; Steinbach, J.;
Complementary mirror-image L-oligonucleotides (L-ON) and tumorspecific antibodies appear as a suitable system for pretargeting technologies. However, optimization of the radiopharmacological characteristics of the LON is a prerequisite for high accumulation in the target. The objective was to decrease the kidney uptake, to increase the area under the blood curve (AUC), and to minimize the nonspecific accumulation in the body. Therefore the L-ON were conjugated with PEG units of increasing size (2, 5, 10, 20 kDa) and subsequently derivatized with NOTA and DOTA for radiolabeling with Ga-68, Cu-64, Y-86, Y-90, Lu-177.
We investigated the impact of size and structure of the radiolabeled (Ga-68, Cu-64) L-ON on biodistribution and positron emission tomography kinetics. The increasing PEG units, up to 20 kDa PEG, decreased the kidney uptake, increased the activity concentration in the blood, e.g., the AUC, but also increased the liver uptake. We can decisively influence the pharmacokinetics resulting in optimal L-ON kinetics and distribution. These results, combined with the option of different radionuclides and high specific activities of the radiolabeled L-ON, emphasizes the attractiveness of this complementary system for pretargeting approaches.
  • Lecture (Conference)
    International Symposium on Technetium and other Radiometals in Chemistry and Medicine, 08.-11.09.2010, Bressanone, Italy
  • Abstract in refereed journal
    Nuclear Medicine and Biology 37(2010)6, 706
    DOI: 10.1016/j.nulmedbio.2010.04.100
  • Contribution to external collection
    Ulderico Mazzi, William V. Eckelman, Wynn A. Volkert: Technetium and Other Radiometals in Chemistry and Medicine, Padova: SGEditoriali, 2010, 357-362

Publ.-Id: 14759 - Permalink


99mTc-labelled vasopressin peptide as a potential radiopharmaceutical for small-cell lung cancer imaging
Koźmiński, P.; Gniazdowska, E.; Bańkowski, K.; Pietzsch, H.-J.;
The aim of the paper was to synthesize and investigate the conjugate of the “4+1” mixed-ligand technetium(III) complex with the vasopressin peptide-99mTc(NS3)(CN-AVP). The overexpression of vasopressin receptor V2 has been found in the case of small-cell lung cancer.
The “4+1” mixed-ligand technetium complex consists of central metal ion Tc(III) coordinated simultaneously by a tetradentate NS3 tripodal chelator tris(2-mercaptoethyl)-amine and a monodentate isocyanide ligand, previously coupled with the selected biomolecule. The identity of the 99mTclabelled vasopressin peptide was corroborated by investigation of the analogous rhenium compound. The 99mTc-labelling vasopressin conjugate was formed in two-step synthesis, via the 99mTc-EDTA intermediate complex, with the final yield of 95%. After 24 h of incubation of the conjugate in the 10 mM solution of histidine or cysteine, the obtained highperformance liquid chromatography chromatograms have shown the existence of one radioactive species, with the retention time characteristic for the complex studied. The log D value of −0.48±0.02 for the 99mTclabelled vasopressin peptide was found. This value (higher than the lipophilicity of the free vasopressin peptide equal to −2.15) can be corrected by introducing a hydrophilic group, R, at the periphery of the NS3 ligand.
  • Poster
    International Symposium on Technetium and other Radiometals in Chemistry and Medicine, 08.-11.09.2010, Bressanone, I
  • Abstract in refereed journal
    Nuclear Medicine and Biology 37(2010)6, 704
    DOI: 10.1016/j.nulmedbio.2010.04.128
  • Contribution to external collection
    Ulderico Mazzi, William V. Eckelman, Wynn A. Volkert: Technetium and Other Radiometals in Chemistry and Medicine, Padova: SGEditoriali, 2010, 337-338

Publ.-Id: 14758 - Permalink


Studies of new [Tc(N)(PS)]-based mixed compounds as analogues of WAY 100635
Bolzati, C.; Salvarese, N.; Carta, D.; Pietzsch, H.-J.; Bergmann, R.; Dolmella, A.; Bandolini, G.;
This study was focused on evaluating the applicability of a new labelling procedure to the preparation of 99mTc(N)-based target specific compounds. The chemistry is based on the use of the [Tc(N)Cl(PS)(PPh3)] species (PS=alkyl-phosphino-thiolate ligand), which selectively reacts with an appropriate mono-negative chelate, such as a dithiocarbamate (DTC), to give neutral [Tc(N)(PS)(DTC)] compounds. The 2-methoxyphenylpiperazine (L) pharmacophore, which displays a potent and specific affinity for 5HT1A receptors, was selected as functional group and conjugated to the dithiocarbamate unit through different spacers.
The synthesis of [99m/99gTc(N)(PS)(Ln)] complexes, and their stability as well as their biological in vitro and in vivo assays were investigated. [99mTc(N)(PS)(Ln)] compounds were prepared in high yield (N90%) using a multi-step procedure and their chemical identity was determined by highperformance liquid chromatrography comparison with the 99gTc-analogues. All complexes were found to be inert toward transchelation with glutathione and sufficiently stable to the in-vitro action of serum and liver enzymes. Nanomolar affinities for the 5-HT1A receptor were obtained for [99mTc(N) (PSiso)L3] (IC50=1.5 nM). However, a negligible brain uptake was observed after in-vivo administration of the complex.
This work describes the application of a new labelling procedure for incorporating a bioactive molecule into a stable dissymmetric 99mTc(N)-complex. Despite the lack of BBB penetration of [99mTc(N)(PSiso)L3] the favourable binding properties of this compound strongly support the possibility to apply [Tc(N)(PS)]-technology to the preparation of target specific agents useful in peripheral applications.
  • Poster
    International Symposium on Technetium and other Radiometals in Chemistry and Medicine, 08.-11.09.2010, Bressanone, Italy
  • Abstract in refereed journal
    Nuclear Medicine and Biology 37(2010)6, 700
    DOI: 10.1016/j.nulmedbio.2010.04.026
  • Contribution to external collection
    Ulderico Mazzi, William V. Eckelman, Wynn A. Volkert: Technetium and Other Radiometals in Chemistry and Medicine, Padova: SGEditoriali, 2010, 313-314

Publ.-Id: 14757 - Permalink


Induction heating for pendent-drop melt extraction from a metallic sheet
Park, J.-S.; Pal, J.; Cramer, A.; Gerbeth, G.; Taniguchi, S.;
Induction heating for pendent-drop melt extraction (PDME) from a metallic sheet is simulated and optimized. This numerical study aims at concentrating dissipated powers on the lower edge of the metallic sheet so that multi-extraction of fine fibers from the wide metallic drop is realized. The solutions on the electromagnetic field are obtained numerically by three-dimensional (3D) modeling based on Finite Element Method (FEM) using ANSOFT Maxwell software, then verified experimentally by lab-scale tests. Subjects to variation are (1) the extension of the substrate (extraction wheel) in both directions parallel and perpendicular to the inductor, (2) the protrusion depth of the edge below the lower face of the inductor and (3) the shape of the inductor. The numerical simulations suggest that the vertical position of the inductor has to be significantly higher than that in Reference 1 in order to increase the efficiency of the process.
  • Lecture (Conference)
    The 4th Asian Workshop on EPM, 03.-06.10.2010, Jeju, Korea
  • Contribution to proceedings
    The 4th Asian Workshop on EPM, 03.-06.10.2010, Jeju, Korea
    Induction heating for pendent-drop melt extraction from a metallic sheet, pp. 252-256

Publ.-Id: 14756 - Permalink


Direct evidence of long lived trapped carriers in InGaAs/GaAs quantum dots studied using terahertz-activated luminescence measurements
Bhattacharyya, J.; Wagner, M.; Helm, M.; Hopkinson, M.; Wilson, L. R.; Schneider, H.;
Trapped carrier dynamics in semiconductor quantum dots (QDs) have been studied using terahertz activated luminescence. This technique enabled us to isolate the luminescence emitted by the trapped carriers from the photoluminescence due to interband excitation. Trapped carriers having long lifetimes ~ 250 ns at 8 K were observed. Temperature dependence of the trapped carrier lifetime was measured. Activation energy for the trapped carrier decay rate was found to be close to the intersublevel transition energy of the QDs.
Keywords: trapped carriers, quantum dots, terahertz activated luminescence
  • Lecture (Conference)
    ICPS-30, 25.07.2010, Seoul, South Korea
  • Contribution to proceedings
    ICPS 2010, 30th International Conference on the Physics of Semiconductors, 25.-30.07.2010, Seoul, South Korea
    AIP Conference Proceedings 1399(2011)593

Publ.-Id: 14755 - Permalink


Results from the LIMMCAST programme: Modelling the steel flow in the mould with cold liquid metals
Gerbeth, G.; Eckert, S.; Timmel, K.; Miao, X.;
Model experiments with low melting point liquid metals are an important tool to investigate the flow structure and related transport processes in melt flows relevant for metallurgical applications. We present the new experimental facility LIMMCAST for modelling the continuous casting process of steel using the alloy SnBi at temperatures of 200-400°C. The possibilities for flow investigations in tundish, submerged entry nozzle and mould will be discussed. In addition, experimental results will be presented on the impact of a steady magnetic field on the outlet flow from the nozzle, obtained at a smaller-scale set-up working with the room-temperature alloy GaInSn. Local velocities are measured by Ultrasound Doppler Velocimetry and contactless inductive flow tomography. The magnetic field significantly changes the jet-type flow in the mould. Surprisingly, in some parameter ranges the DC field creates low-frequency oscillations of the flow structure which resulted in increased velocity fluctuations. Numerical simulations using the CFX code confirm this magnetic field action.
  • Lecture (Conference)
    The 4th Asian Workshop on EPM, 03.-06.10.2010, Jeju, Korea
  • Contribution to proceedings
    The 4th Asian Workshop on EPM, 03.-06.10.2010, Jeju, Korea
    Results from the LIMMCAST programme: modelling the steel flow in the mould with cold liquid metals, 9-12

Publ.-Id: 14754 - Permalink


Preparation of DOTA-dendron Cetuximab bioconjugates for radioimmunotherapy using 90Y, 177Lu and 67Cu
Heldt, J.-M.; Zenker, M.; Pietzsch, H.-J.; Bergmann, R.; Steinbach, J.;
In order to improve the efficiency of radioimmunotherapy by augmenting the specific activity of the radiolabeled bioconjugates while preserving their immunoreactivity, we prepared a water-soluble dendron bearing four 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid moieties by solidphase peptide synthesis. An N-hydoxysuccinimide ester of the dendron was synthesized and the dendron conjugated to lysine amino groups of the therapeutic monoclonal antibody Cetuximab which is specific for the epidermal growth factor receptor and overexpressed by various tumours. Dendron-bearing Cetuximab is thus used for treatment of colon, head, and neck cancer, so as to combine high specific activities brought by multilabeling to achieve a more effective targeted radionuclide therapy as it has been shown for Zevalin and Rituximab. The dendron to antibody ratio was determined by MALDI-TOF MS. These new conjugates have been radiolabeled by 64Cu and 90Y and higher specific activities have been obtained compared to monochelator- labeled antibody. positron emission tomography imaging in mice showed a significant tumour accumulation. Here we discuss the relationships between dendron to antibody ratio, antigen affinity and specific activity of monochelator and dendron-labeled Cetuximab conjugates.
  • Poster
    International Symposium on Technetium and other Radiometals in Chemistry and Medicine, 08.-11.09.2010, Bressanone, Italy
  • Abstract in refereed journal
    Nuclear Medicine and Biology 37(2010)6, 696-697
    DOI: 10.1016/j.nucmedbio.2010.04.005
  • Contribution to external collection
    Ulderico Mazzi, William V. Eckelman, Wynn A. Volkert: Technetium and Other Radiometals in Chemistry and Medicine, Padova: SGEditoriali, 2010, 255-256

Publ.-Id: 14753 - Permalink


Ga-68 Microspheres and Galligas for lung scintigraphy with PET
Wunderlich, G.; Schiller, E.; Pietzsch, H.-J.; Bergmann, R.;
To handle the present shortage of Mo-99 in the nuclear medicine community, we offer alternative preparations for lung scintigraphy, Ga-68-labelled DOTA microspheres (DOTA MS) and labelled aerosol, analogously to well-known Technegas.
Over the last three decades, several trials have been made to label HSA microspheres with Ga-68 in an efficient manner and with stability. Biodegradable albumin microspheres (HSAM) have been widely applied for lung perfusion scintigraphy (Tc-99m HSAM) or labelled with Re-188 for internal radiation therapy. We present in vitro and in vivo stability data of Ga-68 DOTA HSAM in Wistar rats.
DOTA-Bz-NCS was reacted with HSAM and labelled with Ga-68 from a Ge-68/Ga-68 generator by a simple and reproducible method in high yields. The in vitro stability of Ga-68-labelled DOTA-HSAM was checked by incubation in human plasma and by challenging with DTPA.
After intravenous injection into a tail vain, the Ga-68 DOTA MS was rapidly filtered from venous blood and accumulated almost quantitatively in the lungs. Radioactivity level then remains constant for at least 30 min (PET studies with microPET P4). Ga-68-labelled particles showed high in vitro stability and almost quantitative accumulation in the lungs after intravenous application. We consider that Ga-68 DOTA HSAM is a potential radiotracer for lung and other organ perfusion studies.
On the other hand, for ventilation, Ga-68 Galligas aerosol for PET imaging is simple to produce in a Technegas apparatus which can produce Ga-68 eluate concentrated in acetone/HCl. It was stable in vivo (tested over 3.5 h) and allows PET imaging in man with 5–10 MBq Ga-68 only.
  • Poster
    International Symposium on Technetium and other Radiometals in Chemistry and Medicine, 08.-11.09.2010, Bressanone, Italy
  • Abstract in refereed journal
    Nuclear Medicine and Biology 37(2010)6, 694
    DOI: 10.1016/j.nucmedbio.2010.04.016
  • Contribution to external collection
    U. Mazzi, W. C. Eckelman, W. A. Volkert: Technetium and Other Radiometals in Chemistry and Medicine, Padova: SGEditoriali Padova, 2010, 235-236

Publ.-Id: 14752 - Permalink


Effect of carrier redistribution on spin polarization in n-doped InGaAs quantum dot ensemble
Bhattacharyya, J.; Wagner, M.; Helm, M.; Hopkinson, M.; Wilson, L. R.; Schneider, H.;
Semiconductor quantum dots (QDs) are found to have relatively long spin depolarization times, which makes them promising candidates for practical realization of qubits for spintronics based computation. For doped QDs the presence of the excess carriers in the dots modifies the electron-hole interaction leading to unusual spin polarization properties like negative spin polarization. From our experiments we found that the sign and magnitude of the spin polarization depended on the excitation energy and the QD transition involved. Therefore, to understand the spin dynamics in doped QDs and the role of excited states, we performed photoluminescence quenching measurements using circularly polarized interband excitation and temporally synchronized terahertz pulses to induce intersublevel transitions.

The sample studied was an ensemble of n-doped InGaAs/GaAs QDs with an average doping of one electron per dot. The s-p intersublevel energy was tuned to about 20 meV (5 THz) by thermal annealing. A circularly polarized Ti:sapphire laser was used for interband excitation, where the wavelength was adjusted to enable excitation in the barrier, the wetting layer (WL) or the QDs. Terahertz pulses from a free-electron laser (FEL), synchronized to the Ti:sapphire laser, were used to excite intersublevel transitions (~ 20 meV, i.e. 5 THz) in the QDs. A streak-camera coupled to a CCD enabled time and wavelength resolved PL detection.

Time-resolved photoluminescence measurements at ~10 K, for cross-circular (s+s+), i.e. excitation s+ and detection s+, and cross-circular (s+s-) polarizations showed weak negative spin polarization for the QD ground state transition (Figure 1(a)). When excited by long wavelengths, the PL spectrum showed multiple peaks due to selective excitation of the QD ensemble. Some of these features were associated with phonon mediated transitions and exhibited strong positive circular polarization anisotropy (Figure 1(b)). The effect of the FEL pulses on the spin polarization was found to depend on the excitation wavelength. While the strong positive spin polarization for excitation below the wetting layer was drastically reduced by the FEL pulse (as shown by the solid lines in Figure 1 (b)), the weak negative polarization was found to persist. This suggests different mechanisms involved in the generation of spin polarization for different excitation energies. We will discuss the origins of these spin polarizations associated with different transitions in the QD ensemble and their dynamical behaviour. By varying the time-delay of the FEL pulses with respect to the Ti:sapphire laser pulses for interband excitation in the barrier or the WL, we confirmed the existence of trapped carriers. Trapped carriers have been reported to have considerable effect on the PL response of QDs. The FEL pulses induced two competitive phenomena that affect the spin polarization, i.e. (i) diffusion of trapped carriers resulting in increased PL and (ii) intersublevel transitions resulting in a quenching of the PL signal. To summarize, this work investigates the influence of the intradot transitions and interdot diffusion of the trapped carriers on the spin polarization of the QD ensemble.
Keywords: Time-resolved Photoluminescence, Spin polarization, PL quenching
  • Poster
    The 6th International Conference on the Physics and Applications of Spin Related Phenomena in Semiconductors (PASPS-VI), 01.10.2010, Tokyo, Japan

Publ.-Id: 14751 - Permalink


Accessible silanol sites - beneficial for the RP-HPLC separation of constitutional and diastereomeric azaspirovesamicol isomers
Wenzel, B.; Fischer, S.; Brust, P.; Steinbach, J.;
Different RP-HPLC columns (phenyl, conventional ODS, cross-linked C18 and special end-capped C8 and C18 phases) were used to investigate the separation of four basic ionizable isomers. Using ACN/20 mM NH4OAc aq., a separation was observed exclusively on RP columns with higher silanol activity at unusual high ACN concentration, indicating cation-exchange as main retention mechanism. Using MeOH/20 mM NH4OAc aq., another separation at low MeOH concentrations was observed on both, RP columns with higher as well as RP columns with lower silanol activity, which is mainly based on hydrophobic interactions. The isomers were also separated on a bare silica column at higher MeOH content using NH4OAc as buffer. Since cation-exchange governs this retention, the elution order was different compared to the RP phases. A strong retention on the silica column was observed in ACN, which could be attributed to partition processes as additional retention mechanism.
Keywords: azaspirovesamicol isomers, silanol sites, cation-exchange, silica column, retention mechanism, basic analytes, VAChT

Publ.-Id: 14750 - Permalink


Molecular imaging of σ receptors: synthesis and evaluation of the potent σ1 selective radioligand [18F]fluspidine
Fischer, S.; Wiese, C.; Grosse Maestrup, E.; Hiller, A.; Deuther-Conrad, W.; Scheunemann, M.; Schepmann, D.; Steinbach, J.; Wünsch, B.; Brust, P.;
Purpose Neuroimaging of σ1 receptors in the human brain has been proposed for the investigation of the pathophysiology of neurodegenerative and psychiatric diseases. However, there is a lack of suitable 18F-labelled PET radioligands for that purpose.

Methods The selective σ1 receptor ligand [18F]fluspidine (1'-Benzyl-3-(2-[18F]fluoroethyl)-3Hspiro[[2]benzofuran-1,4'-piperidine]) was synthesised by nucleophilic 18F- substitution of the tosyl precursor. In vitro receptor binding affinity and selectivity were assessed by radioligand competition in tissue homogenate and autoradiographic approaches. In female CD-1 mice, in vivo properties of [18F]fluspidine were evaluated by ex vivo brain section imaging and organ distribution of intravenously administered radiotracer. Target specificity was validated by organ distribution of [18F]fluspidine after treatment with 1 mg/kg, i.p. of the σ receptor antagonist haloperidol or the emopamil binding protein (EBP) inhibitor tamoxifen. In vitro metabolic stability and in vivo
metabolism were investigated by LC-MSn and radio-HPLC analysis.

Results [18F]Fluspidine was obtained with a radiochemical yield of 35-45%, a radiochemical purity of ≥99.6%, and a specific activity of 150-350 GBq/μmol (n=6) within a total synthesis time of 90-120 min. In vitro, fluspidine bound specifically and with high affinity to σ1 receptors (Ki = 0.59 nM). In mice, [18F]fluspidine rapidly accumulated in brain with uptake values of 3.9 and 4.7 %ID/g and brain to blood ratios of 7 and 13 at 5 and 30 min after intravenous application of the radiotracer, respectively. By ex vivo autoradiography of brain slices, resemblance between binding site occupancy of [18F]fluspidine and the expression of σ1 receptors was shown. The radiotracer uptake in the brain as well as in peripheral σ1 receptor expressing organs was significantly inhibited by haloperidol but not by tamoxifen. Incubation with rat liver microsomes led to a fast biotransformation of fluspidine. After an incubation period of 30 min only 13 % of the parent compound was left. Seven metabolites were identified by HPLC-UV and LC-MSn techniques. However, [18F]fluspidine showed a higher metabolic stability in vivo. In plasma samples ~94% of parent compound remained at 30 min and ~ 67% at 60min p.i. Only one major radiometabolite was detected. None of the radiometabolites did cross the blood-brain-barrier.
Conclusion [18F]Fluspidine demonstrated favourable target affinity and specificity as well as metabolic stability both in vitro and in animal experiments. The in vivo properties of [18F]fluspidine offer a high potential of this radiotracer for neuroimaging and quantitation of σ1 receptors in vivo.
  • European Journal of Nuclear Medicine and Molecular Imaging 38(2011)3, 540-551

Publ.-Id: 14749 - Permalink


X-Ray Diffraction from Periodically Patterned GaAs Nanorods Grown onto GaAs[111]B
Davydok, A.; Biermanns, A.; Pietsch, U.; Grenzer, J.; Paetzelt, H.; Gottschalch, V.;
We present a high-resolution X-ray diffraction pattern of periodic GaAs nanorod (NR) ensembles and individual GaAs NRs grown catalyst-free throughout a prepatterned amorphous SiN x mask onto GaAs[111]B surfaces. The experiments were performed at a home laboratory using synchrotron radiation in combination with a micron-sized beam prepared by compound refractive lenses. The structural properties were probed by measuring RSMs (q x , q z ) in the vicinity of GaAs(111) and (222) reflections. Besides the GaAs substrate peak, we found a second peak referring to NRs with lattice mismatch of 0.23 pct with respect to the substrate, probably caused by structural defects. The lateral periodicity of NRs was probed by q x scans, and the NR height obtained from the width of the diffraction curve along q z . Grazing-incidence in-plane diffraction revealed the appearance of small crystallites of cubic γ-Si3N4 caused by recrystallization of SiN x during NR growth. Whereas measurements at the home diffractometer provided average structure parameters, the micron-sized X-ray beam experiment was used to probe the parameters at individual NRs.

Publ.-Id: 14748 - Permalink


First In-Human Data of Fluorine-18 Labelled Fluoromethyl-McN5652 for In-Vivo imaging of Brain Serotonin Transporters (SERT) with PET
Hesse, S.; Brust, P.; Mäding, P.; Zessin, J.; Becker, G.; Patt, M.; Seese, A.; Sorger, D.; Habermann, B.; Meyer, P.; Luthardt, J.; Bresch, A.; Steinbach, J.; Sabri, O.;
Aim: DASB is currently the most frequently applied highly selective radiotracer for visualisation and quantification of central SERT. Its use, however, is hampered by the short half‐life of carbon‐11, the moderate cortical test retest reliability, and the lack for quantifying endogenous serotonin. The aim of our study was to first apply in human the new highly SERT‐selective fluorine‐18 labelled fluoromethyl analogue of (+)‐McN5652 ([18F]FMe‐McN).
Methods: The synthesis of [18F]FMe‐McN was performed according to Zessin et al. with some modifications. Briefly, the demethylated (+)‐McN5652 was reacted with bromo‐[18F]fluoromethane to yield [18F]FMe‐McN, which was purified by reversed‐phase HPLC. For in vivo human studies, five healthy volunteers (2 female, age 39±10 years) underwent dynamic PET over 120 minutes after intravenuous injection of a 90 s bolus of 298±57 MBq [18F]FMe‐McN and a static acquisition over 30 minutes 3 h p.i.. PET data were coregistered with individual MRI data set using PMOD and VOI analysis was performed. Target‐to‐background‐ratios (TB‐R, cerebellum as background structure) were compared with those of a reference data set assessed by [11C]DASB‐PET in 21 healthy subjects (11 female, 38±8 years).
Results: TB‐R ([18F]FMe‐McN) displays no hemispheric differences. The values are for the frontal cortex (FC) 1.02±0.04 (right‐hand side) and 1.01±0.03 (left), for the head of caudate region (caud) 1.46±0.16 (right) and 1.50±0.15 (left) and for the raphé region 2.04±0.11. Corresponding TB‐R ([11C]DASB) are 1.10±0.07 (FC right, ANOVA p=0.05), 1.08±0.78 (FC left, 0.06), 2.14±0.21 (caud right, 0.02), 2.06±0.19 (caud left, 0.04) und 2.23±0.39 (raphé, 0.04). Visually, image quality of [11C]DASB‐PET is superior to [18F]FMe‐McN .
Conclusion: Cerebral radiotracer uptake fits well with the known SERT distribution also in humans. Hence, [18F]FMe‐McN might be suitable for in vivo quantification of SERT. Despite a tendency to lower TB‐R compared to [11C]DASB, the lower standard deviation of [18F]FMe‐McN TB‐R can be advantageous with regard to test‐retest estimations in larger study cohorts. Also, labelling with fluorine‐18 allows (1) later data acquisition times, which is useful for the investigation of the
tracer kinetics in brain tissue (modelling), and (2) a widespread application within a satellite concept e.g. in multicenter trials.
References Zessin J, Eskola O, Brust P et al. Nucl Med Biol 2001; 28: 857‐863.
  • Poster
    23rd Annual Congress of the European Association of Nuclear Medicine (EANM), 09.-13.10.2010, Wien, Österreich
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 37(2010)2, S387

Publ.-Id: 14747 - Permalink


Growth of spatially ordered Ge nanoclusters in an amorphous matrix on rippled substrates
Buljan, M.; Grenzer, J.; Keller, A.; Radic, N.; Vales, V.; Bernstorff, S.; Cornelius, T.; Metzger, H.; Holy, V.;
So far, the growth of spatially ordered nanoclusters by multilayer deposition has been reported and explained satisfactorily only in crystalline materials. Here we demonstrate a method for the growth of spatially ordered nanoclusters in amorphous matrices, where the ordering is achieved in the single large domain. The regular ordering is induced by the deposition of a multilayer on a periodically rippled substrate at an elevated substrate temperature. During the deposition, the nanoclusters self-arrange, following the morphology of the substrate.

Publ.-Id: 14746 - Permalink


Synthesis and first radiopharmaceutical investigation of 5-[125I]Iodo-SU11248, a potential radiotracer for imaging VEGFR
Kniess, T.; Oliveira, C.; Kuchar, M.; Gano, L.; Santos, I.; Steinbach, J.;
Aim: Due to the fact that receptor tyrosine kinases (RTKs) are overexpressed in some tumour entities, they might be a suitable target for PET or SPECT imaging. Then, tyrosine kinase inhibitors labeled with a radioisotope could represent a useful tool for monitoring levels of RTKs in tumour tissue giving valuable information for anti‐angiogenic therapy. SU11248 (Sunitinib®) is a novel highly potent RTK inhibitor targeting vascular endothelial growth factor receptor (VEGFR)
(IC50=0.08μM) [1]. We report here the synthesis of a 125I‐labeled derivative of SU11248 and its first radiopharmaceutical characterization.
Materials and methods: 5‐[125I]lodo‐SU11248 was obtained via destannylation of the corresponding tributylstannyl precursor with [125I]NaI in the presence of H2O2. The radioiodinated compound has been purified by RP‐HPLC with UV and radioactivity detection using methanol/0.1% TFA (85:15) as eluent. Determination of human plasma protein binding at time intervals of 0; 1; 2; 4 and 24h was accomplished by incubation of the radiotracer in fresh human serum at 37°C. Preliminary biodistribution studies were carried out in healthy CD‐1 mice and in vivo stability was assessed by HPLC analysis of urine samples collected at sacrifice time.
Results: 5‐[125I]Iodo‐SU11248 could be obtained in high radiochemical yield (>95%). After HPLC purification the radiochemical purity exceeded 98%. The identity of the radiotracer was confirmed by co‐elution with 5‐Iodo‐SU11248 as reference compound [2]. Lipophilicity of 5‐[125I]Iodo‐SU11248 has been assessed using the octanol/PBS partition coefficients (logPo/w) and was found to be 2.25. Determination of human plasma protein binding suggested a low non‐specific binding of 5‐10%. Biodistribution studies showed a relatively high uptake in VEGFR‐2 rich tissues like kidney and lung, followed by rapid washout (9.6 and 9.7; 4.5 and 3.8% ID/g kidney and lung at 1 and 4 h, respectively).
Conclusion: The new 5‐[125I]Iodo‐SU11248 was synthesized in high radiochemical yield and purity. The high stability in human serum and urine samples, suggests that the tracer is not significantly metabolized. The ability of 5‐Iodo‐SU11248 to inhibit tyrosine kinase activity, a mandatory prerequisite for further studies on RTK expressing cells, is underway, to disclose whether this radiotracer would be a useful tool for monitoring VEGFR expression. Ultimately, the radiochemical profile of 5‐[125I]Iodo‐SU11248 associated to a low non‐specific binding and rapid clearance from most tissues encourages further radiolabeling with other radioisotopes, such as 123I for SPECT or 124I for PET.
[1] Sun L., Liang C. et al., J. Med. Chem., 46, (2003), 1116 [2] Kniess T., Oliveira C. et al., unpublished results
  • Poster
    23rd Annual Congress of the European Association of Nuclear Medicine (EANM), 09.-13.10.2010, Wien, Österreich
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 37(2010)2, S364

Publ.-Id: 14745 - Permalink


Generation of an ordered Ge quantum dot array in an amorphous silica matrix by ion beam irradiation: Modeling and structural characterization
Buljan, M.; Bogdanovic-Radovic, I.; Karlusic, M.; Desnica, U.; Radic, N.; Skukan, N.; Drazic, G.; Ivanda, M.; Gamulin, O.; Matej, Z.; Vales, V.; Grenzer, J.; Cornelius, T.; Metzger, H.; Holy, V.;
We studied the generation of an ordered Ge quantum dot array in an amorphous silica matrix by ion beam irradiation. In particular we investigated the influence of the irradiation process on the nucleation of Ge clusters, on the correlations in their positions and on the crystalline quality of Ge quantum dots formed after subsequent annealing. We have developed a method for the description of the intensity of grazing-incidence x-ray small-angle scattering from irradiated multilayers, which enables a precise determination of the arrangement of quantum dots as well as their position correlation and size distribution. The analysis shows that the irradiation causes an ordering of Ge clusters along the irradiation direction, which substantially improves the correlations of the Ge dot locations in their three-dimensional array. The observed phenomena are explained and simulated by a Monte Carlo model based on the modification of local Ge density induced by ion tracks in the irradia!
ted multilayers.

Publ.-Id: 14744 - Permalink


Comparison of Ga-68 labelled RGD-peptides for imaging integrin alpha(v)beta3 expression
Knetsch, P.; Seidel, G.; Petrik, M.; Rangger, C.; Helbok, A.; Griessinger, C.; Fani, M.; von Guggenberg, E.; Wester, H.; Pichler, B.; Pietzsch, H.-J.; Decristoforo, C.; Haubner, R.;
Aim: An promising therapeutic approach to treat cancer focus on the inhibition of tumourinduced angiogenesis. One target structure involved is integrin alpha(v)beta3. Imaging modalities allowing monitoring of alpha(v)beta3 may provide insights into corresponding molecular process. Labelling techniques becoming more and more interesting for molecular imaging with PET are based on Ga‐68. Especially, due to the straightforward labelling protocols this is an interesting alternative to F‐18 labelling of peptides. Here the imaging properties of c(RGDfK) conjugated to different chelating systems are compared.
Methods: Peptide synthesis follows standard SPPS protocols. The cyclised and selectively deprotected peptides were conjugated with the chelating moieties via the side chain amino function of the lysine. The chelating systems include 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐acetic acid (DOTA), 1,4,7‐triaazacyclononane‐4,7‐acetic acid‐1‐2‐glutaric acid (NODAGA), and a tris(2‐mercaptoethyl)amine derivative (NS3). Labelling was carried out using the fractionated elution method in sodium acetate (DOTA; NODAGA) or phosphate buffer (NS3). In vitro evaluation included log D determination, protein binding assays, plasma stability studies, isolated receptor binding assays, and cell uptake studies. In vivo evaluation was carried out using M21 (alpha(v)beta3 positive) and M21L (alpha(v)beta3 negative) bearing nude mice. For all tracer biodistribution data were collected. For DOTA‐RGD and NODAGA‐RGD also small animal PET imaging was carried out. Results: NODAGA‐RGD and NS3‐RGD could be labelled at room temperature, whereas labelling of DOTA‐RGD has to be carried out at elevated temperature. NODAGA‐RGD and DOTA‐RGD could be labelled in high radiochemical purity without further purification. For NS3‐RGD a subsequent Seppak separation was necessary to obtain the product in high radiochemical purity. The compounds showed comparable log D (‐2.9 ‐ ‐3.9) and IC(50) values (~5 nM) as well as receptor specific uptake. In contrast, great differences were found in the protein binding properties. The found protein bound activity after 1 h incubation was 18.6% (DOTA‐RGD), 42,4% (NS3‐RGD), and 1.4% (NODAGA‐RGD). This performance is reflected in the biodistribution data. Lowest activity concentration in blood (%ID/g 1h p.i.: NODAGA‐RGD=0.12±0.06 ; DOTA‐RGD=0.72±0.07; NS3‐RGD=3.33±1.9) and best tumour/background ratios were found for NODAGA‐RGD. Small animal imaging confirmed these findings and indicated that NODAGA‐RGD might have similar imaging properties as found for F‐18‐Galacto‐RGD. Conclusions: In this series NODAGA‐RGD revealed most promising properties for imaging alpha(v)beta3 expression. Easy radiolabelling at room temperature, low amount of protein bound activity and the resulting lower activity concentration found in blood compared to the other compounds makes it to an attractive alternative to F‐18‐Galacto‐RGD, worth to be tested in clinical studies.
  • Lecture (Conference)
    23rd Annual Congress of the European Association of Nuclear Medicine (EANM), 09.-13.10.2010, Wien, Österreich
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 37(2010)2, S252

Publ.-Id: 14742 - Permalink


Biodistribution and metabolism of a Ga-68 labeled tris(salicylaldimine) derivative - a myocard perfusion tracer
Bergmann, R.; Jeong, J. M.; Pietzsch, J.; Steinbach, J.; Baum, R. P.;
Aim: The lipophilic cationic Ga‐68‐complex (Tsang B.W. et al. J Nucl Med 1993; 34; 1127) of Tris(4,6‐dimethoxysalicylaldimine)‐N,N′‐bis(3‐aminopropyl)‐N,N′‐ethylenediamine (BAPEN), showed high accumulation in mice hearts (Nucl Med Biol 2010; 37; 149). To reevaluate the radiopharmacological profile in rats the Ga‐68‐BAPEN was produced by a kit formulation and the biodistribution, kinetics and metabolism were studied with small animal PET.
Materials & methods: The BAPEN was labeled with 0.1 M HCl Ga‐68‐Cl3 (generator eluate 1 M HCl) in a one step procedure. Before application human serum albumin was added to a final concentration of 1%, and the solution filtrated (22 μm pore size). The biodistribution at 5 and 60 min p.i. (each time point 8 rats) after single intravenous injection, arterial blood clearance over 1 h (n=2), and the in vivo metabolism in Wistar rats were investigated in combination with small animal PET, and the main biokinetic parameters of Ga‐68‐BAPEN were estimated.
Results: Ga‐68‐BAPEN was prepared with purity >91% within 20 min. The activity was fast accumulated in the rat heart (values in SUV; 5 min p.i., 1.56 ± 0.19; 60 min, 1.42 ± 0.35) with the following heart‐to‐tissue ratios at 5 min p.i.: blood 4.2, lung 2.2, liver 0.4, kidneys 0.3, and brain 109.6. No clearance of Ga‐68‐activity from the heart was observed over 1 hour. The arterial blood clearance of the original compound was biphasic with half lifes of 2 min and 23 min respectively; it was metabolized with a half‐life of 1.6 min. The Ga‐68‐activity was rapidly excreted into the intestine (5 min p.i. 34.9 ± 4.0%ID; 60 min p.i. 56.7 ± 7.0%ID).
Conclusion: Ga‐68‐BAPEN showed a typical perfusion dependent biodistribution pattern in rats, with high accumulation in heart, kidneys, liver, adrenals, and pancreas. The heart was clearly delineated with low background. The increasing liver uptake could complicate the quantitative imaging of the heart apex at late time points. Ga‐68‐BAPEN was fast distributed followed by a slow blood clearance on a low activity level. The fast in vivo metabolism of the Ga‐68‐BAPEN in rats prevented a more distinct perfusion dependent biodistribution pattern. No transport through the blood‐brain‐barrier into the brain was observed. The Ga‐68‐BAPEN may be useful as radiopharmaceutical for perfusion imaging, particularly, for the heart.
  • Lecture (Conference)
    23rd Annual Congress of the European Association of Nuclear Medicine (EANM), 09.-13.10.2010, Wien, Österreich
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 37(2010)2, S251
  • Poster
    2010 World Molecular Imaging Congress, 08.-11.09.2010, Kyoto, Japan

Publ.-Id: 14741 - Permalink


Preclinical radiation dose assessment of (-)-[F18]NCFHEB, a new PET tracer for imaging of cerebral alpha4beta2 nicotinic acetylcholine receptors
Sattler, B.; Deuther-Conrad, W.; Fischer, S.; Hiller, A.; Patt, M.; Kendziorra, K.; Hesse, S.; Smits, R.; Hoepping, A.; Steinbach, J.; Sabri, O.;
Aim: (‐)‐[F‐18] Norchloro‐fluoro‐homoepibatidine ((‐)‐NCFHEB) is a new and promising tracer for neuroimaging of alpha4beta2 nicotinic acetylcholine receptors with PET. To assess the radiation risk to humans caused by systemic application of the tracer, CD1 mice were injected with (‐)‐NCFHEB. The biodistribution of the tracer and, thereby, resulting organ doses (OD) and the effective dose (ED) were calculated.
Methods: 27 female CD1 mice (weight: 28.2 ± 2.1g) were injected i.v. with 0.75± 0.334MBq of (‐)‐[F18]NCFHEB (specific activity >100GBq/μmol) through the V. caudata lateralis. At 5, 15, 30, 45, 60, 90, 120, 180 and 240 min. p.i. the animals were sacrificed (n=3 per time). The organs (brain, heart, lung, stomach, small intestine, large intestine, liver, kidneys, urinary bladder, spleen, thymus, pancreas, adrenals, ovaries, blood, skin, muscle, skeleton) were isolated, weighed and counted in a γ‐counter to determine mass and radioactivity. The masses of the skeleton and the muscle were extrapolated from tissue samples [1]. Time and mass scales were adapted to the respective human scales [2]. The fractions of activity in source organs were displayed as %ID/g, and %ID/organ for both scales. Time‐activity curves were derived by trapezoidal and exponential fits. The numbers of disintegrations in the source organs were calculated and ODs and the ED was calculatedusing OLINDA.
Results: The urinary bladder receives the highest OD of 104.0 μSv/MBq, followed by the kidneys (24.2 μSv/MBq), uterus (14.1 μSv/MBq), liver (14.0 μSv/MBq), pancreas (14.0 μSv/MBq) and small intestine (14.0 μSv/MBq) The highest contribution to the ED was by urinary bladder (5.2μSv/MBq) followed by the ovaries (2.1μSv/MBq), lower large intestine (1.5μSv/MBq) and red marrow (1.3 μSv/MBq). According to these data, the ED by i.v. application of (‐)‐[F18]NCFHEB
results in an ED of 14.2 μSv/MBq.
Conclusion: The ED as a measure of the overall radiation risk upon i.v. application of about 370 MBq (‐)‐[F‐18] NCFHEB to humans would be 5.3 mSv. This is well within the range of the application of other [F18]‐labeled compounds to humans. This risk assessment encourages to transfer (‐)‐[F‐18]NCFHEB from preclinical to clinical study phases and to further develop as a clinical tool for PET brain imaging.
References: [1] Lindstedt SL, Schaeffer PJ.: Use of allometry in predicting anatomical and physiological parameters of mammals Laboratory Animals (2002) 36, 1‐19 [2] Stabin MJ: Fundamentals of Nuclear Medicine Dosimetry, Springer 2008, ISBN 978‐0‐387‐74578‐7, 237P The trial is granted by the German Federal Ministry of Education and Research (Nr. 01EZ0820)
  • Lecture (Conference)
    23rd Annual Congress of the European Association of Nuclear Medicine (EANM), 09.-13.10.2010, Wien, Österreich
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 37(2010)2, S205

Publ.-Id: 14740 - Permalink


Reduced myocardial glucose utilization after fasting and heparin injection in rats
Bergmann, R.; Pietzsch, J.;
kein Abstract verfügbar
  • Poster
    78th European Atherosclerosis Society Congress (EAS), 20.-23.06.2010, Hamburg, D
  • Abstract in refereed journal
    Atherosclerosis 11(2010)2, 192

Publ.-Id: 14739 - Permalink


Observation of the intraexciton Autler-Townes effect in GaAs/AlGaAs semiconductor quantum wells
Wagner, M.; Schneider, H.; Stehr, D.; Winnerl, S.; Andrews, A. M.; Schartner, S.; Strasser, G.; Helm, M.;
The near-infrared transmission of a semiconductor multiple quantum well is probed under intense terahertz illumination. We observe clear evidence of the intraexcitonic Autler-Townes effect when the terahertz beam is tuned near the 1s-2p transition of the heavy-hole exciton. The strongly coupled effective two-level system has been driven with terahertz field strengths of up to 10  kV/cm resulting in a Rabi energy of ≈0.6 times the transition energy. The induced near-infrared spectral changes at low intensities are qualitatively explained using a basic two-level model.
Keywords: Autler-Townes effect, AC Stark, intraexciton, free-electron laser

Publ.-Id: 14738 - Permalink


Terawatt Yb:CaF2 laser
Siebold, M.; Uecker, R.; Hornung, M.; Hein, J.; Sauerbrey, R.;
We present a terawatt diode-pumped laser employing single-crystalline Yb:CaF2 as the amplifying medium. A pulse energy of 197 mJ and a duration of 192 fs were obtained, corresponding to a peak power of 1 TW.
  • Invited lecture (Conferences)
    6th International Conference on Crystal Growth ICCG-16, 08.-13.08.2010, Beijing, China

Publ.-Id: 14737 - Permalink


Copper binding to S100A12: Suggested role in oxidative modification of human LDL
Pietzsch, J.; Walther, M.; Bergmann, R.; Hoppmann, S.;
kein Abstract verfügbar
  • Poster
    78th European Atherosclerosis Society Congress (EAS), 20.-23.06.2010, Hamburg, D
  • Abstract in refereed journal
    Atherosclerosis 11(2010)2, 118

Publ.-Id: 14736 - Permalink


Native and glycooxidized high density lipoprotein (HDL) modulate adrenal steroidogenesis via scavenger receptor class B, type I (SR-Bi)
Kopprasch, S.; Saha, S.; Graessler, J.; Pietzsch, J.; Bornstein, S. R.;
kein Abstract verfügbar
  • Poster
    78th European Atherosclerosis Society Congress (EAS), 20.-23.06.2010, Hamburg, D
  • Abstract in refereed journal
    Atherosclerosis 11(2010)2, 113

Publ.-Id: 14735 - Permalink


Influence of novel selective cyclooxygenase-2 (COX-2) inhibitors on copper-mediated oxidation of human LDL
Pietzsch, J.; Pietzsch, F.-J.; Laube, M.; Wuest, F.; Steinbach, J.; Kniess, T.;
kein Abstract verfügbar
  • Poster
    78th European Atherosclerosis Society Congress (EAS), 20.-23.06.2010, Hamburg, D
  • Abstract in refereed journal
    Atherosclerosis 11(2010)2, 76

Publ.-Id: 14734 - Permalink


Multiple bandgap solar cells based on confined Ge nanocrystals in an oxide matrix
Zschintzsch, M.; Jeutter, N.; von Borany, J.; Mücklich, A.; Sahle, C.;
Si and Ge nanocrystals are supposed to be a promising material for high efficient 3rd generation multiple bandgap thin film solar cells. Photoluminescence studies of the quantum confinement effect in Si and Ge nanocrystals showed the feasibility of this approach [1, 2]. We propose the design sketched in Fig. 1 using a stack of well separated, mono-dispersed Ge nanoclusters of different size which allows bandgap tuning for light absorption from the blue to the infrared region.
In this contribution investigations on Ge nanocrystals formation in GeOx-SiO2 multilayer structures will be presented. The nanocrystals growth during annealing is vertically limited by the SiO2 separation layer while the phase separation of the GeOx layer during annealing leads to laterally GeO2 separated Ge nanocrystals. The goal is to achieve well confined, graded, equally sized and dense nano¬crystal superlattices only by the variation of the layer thicknesses and the GeOx composition. The GeOx-SiO2 stacks were deposited via reactive DC magnetron sputtering. A process window for the oxygen partial pressure in the O2/Ar sputtering gas mixture allows both, SiO2 formation for the separation layers as well as GeOx films with tuneable stoichiometry in the range of x = 0.2 - 2 [4].
Very smooth interfaces of the multilayers with roughness’s below 1 nm and a SiO2 separation layer thickness < 2 nm could be revealed with XRR and TEM – fig. 2 shows an annealed sample with Ge nanocrystals with a size of 2 nm. XANES synchrotron measurements (fig. 3) show that the phase separation of GeOx~1 is already finished at 400°C. The crystallisation occurs at 550°C which was monitored by GIXRD and Raman scattering. The Ge nanocrystal size was determined to be 2, 3 or 6 nm for different samples by GIXRD, TEM and Raman. Ellipsometry and absorbance measurements showed additional information’s about the structural and optical parameters of the multilayers. The stochiometry of the stack was always controlled with RBS.
Ge nanoclusters of 2 … 6 nm in size could be formed by phase separation at a temperature of about 400°C and crystallised at 550°C into nanocrystals which allows a broad variety of substrate materials. The very thin and smooth SiO2 separation layer enable interesting possibilities for charge transport via tunnelling.
[1] G. Conibeer et al. TSF 511-512, 654 (2006)
[2] Y. M. Niquet et al. APL 77, 1182 (2000)
[3] F. Dimroth et al. MRS Bulletin 32,230 (2007)
[4] M. Zschintzsch et al. JAP, in print (2010)
  • Poster
    25th European Phtotvoltaic Solar Energy conference, 5th World Conference on Photovoltaic Energy Conversion, Symposium: Advanced Photovoltaics: New Concepts and Ultra-High Efficiency, 06.-10.09.2010, Valencia, Spain

Publ.-Id: 14733 - Permalink


Confined Ge nanocrystals in an oxide matrix for multiple bandgap solar cells
Zschintzsch, M.; Jeutter, N.; von Borany, J.; Mücklich, A.; Sahle, C.;
Si and Ge nanocrystals are believed to be a promising material for high efficient 3rd generation multiple bandgap thin film solar cells. Photoluminescence studies of the quantum confinement effect in Si and Ge nanocrystals showed the feasibility of this approach [1, 2].
Our design is sketched in Fig. 1 which uses a stack of well separated, mono-dispersed Ge nanoclusters of different size on an absorbing Ge layer which allows bandgap tuning for light absorption from the blue to the infrared region. In this conference contribution investigations on Ge nanocrystals formation in GeOx-SiO2 multilayer structures will be reported. The goal is to achieve well separated, equally sized and dense nanocrystal superlattices only by the variation of the layer thicknesses and the GeOx composition. The GeOx-SiO2 multilayers were deposited via reactive DC magnetron sputtering. A process window for the oxygen partial pressure in the O2/Ar sputtering gas mixture allows both, SiO2 formation for the separation layers as well as GeOx films with tuneable stoichiometry in the range of x = 0.2 - 2 [4]. The films stoichiometry were always controlled with RBS. The nanocrystals growth during annealing is vertically limited by the SiO2 separation layer while the phase separation of the GeOx layer during annealing leads to laterally GeO2 separated Ge nanocrystals.
Very smooth interfaces of the multilayers with roughness’s below 1 nm and a SiO2 separation layer thickness < 2 nm could be revealed with XRR and TEM – fig. 2 shows an annealed sample with Ge nanocrystals of 3 nm size. XANES synchrotron measurements (fig. 3) show that the phase separation of GeOx~1 -> Ge + GeO2 is already completed at 400°C. GIXRD and Raman scattering confirme a crystallisation temperature of about 550°C. Ge nanocrystals with well defined sizes between 2 and 10 nm have be fabricated by the variation of the GeOx sublayer thickness. As derived from RAMAN measure¬ments, the degree of crystallinity decreases with reduced layer thickness. The energy dependent optical parameters were determined by means of photoluminescence, ellipsometry and absorbance mea¬surements. The very thin and smooth SiO2 separation layer enables interesting possibilities for charge transport via direct tunnelling.
References:
[1] G. Conibeer et al. Thin Solid Films 511-512, 654 (2006)
[2] Y. M. Niquet et al. Applied Physics Letters 77, 1182 (2000)
[3] F. Dimroth et al. Materials Research Society Bulletin 32, 230 (2007)
[4] M. Zschintzsch et al. Journal Applied Physics 107, 0343061-8 (2010
  • Poster
    Nanofair conference, Symposium: Energy, 06.-07.07.2010, Dresden, Deutschland

Publ.-Id: 14732 - Permalink


Self-Organized Formation of Ge nanocrystals out of (GeOx-SiO2) superlattice structures
Zschintzsch, M.; Jeutter, N.; Mücklich, A.; von Borany, J.; Sahle, C.;
Bandgap engineered Si and Ge nanocrystal solar cells are supposed to be a candidate for high effective 3rd generation thin film solar cells. Photoluminescence studies of the quantum confinement effect in Si and Ge nanocrystals showed the feasibility of this approach [1,2]. However the design and the fabrication of a high density of well separated, monodispersed nanoclusters remains a great challenge.
We want to present our investigations [3] on Ge nanocrystals formation in GeOx-SiO2 multilayer structures based on the phase separation of GeOx during annealing. The size of the laterally self-ordered Ge nanocrystals is vertically limited by the SiO2 separation layer. The final goal is to achieve well confined, graded, equally sized and dense nanocrystal superlattices only by the variation of the layer thicknesses and the oxygen content in the GeOx layer.
The GeOx-SiO2 stacks were deposited via reactive DC magnetron sputtering. A process window for the oxygen partial pressure in the O2/Ar sputtering gas mixture can be defined which allows both, SiO2 formation for the separation layers as well as GeOx films with tunable stoichiometry in the range of x = 0.2 … 2.
In-situ X-ray studies at synchrotron beamlines were performed to monitor the phase separation (XANES) of GeOx and the Ge nanocrystal formation (GIXRD, XRR, GISAXS) which was proofed in addition via TEM, Raman scattering and Absorbance.
Separated Ge nanocrystals of 2 … 6 nm in size can be formed at temperatures < 600°C. Very smooth interfaces with roughnesses below 1 nm allowed the separation of the Ge nanocrystal layers by SiO2 films < 2 nm which enables interesting possibilities for charge transport via tunnelling.
[1] G. Conibeer et al. TSF 511-512, 654 (2006)
[2] Y. M. Niquet et al. APL 77, 1182 (2000)
[3] M. Zschintzsch et al. JAP, 107, 0343061 - 8 (2010)
  • Poster
    MRS Spring Meeting, Symposium: Photovoltaics and Optoelectronics from Nanoparticles, 05.-09.04.2010, San Francisco, California, USA

Publ.-Id: 14731 - Permalink


Quantitative determination of the charge carrier concentration of sub-surface implanted silicon by IR-near-field spectroscopy
Jacob, R.; Winnerl, S.; Schneider, H.; Helm, M.; Wenzel, M. T.; von Ribbeck, H.-G.; Eng, L. M.; Kehr, S. C.;
We use a combination of a scattering-type near-field infrared microscope with a free-electron laser as an intense, tunable radiation source to spatially and spectrally resolve buried doped layers in silicon. To this end, boron implanted stripes in silicon are raster scanned at different wavelengths in the range from 10 to 14 μm. An analysis based on a simple Drude model for the dielectric function of the sample yields quantitatively correct values for the concentration of the activated carriers. In a control experiment at the fixed wavelength of 10.6 μm, interferometric near-field signals are recorded. The phase information gained in this experiment is fully consistent with the carrier concentration obtained in the spectrally resolved experiments.
Keywords: Spectroscopy, Near-field microscopy, Infrared, Semiconductor materials

Publ.-Id: 14730 - Permalink


The CBM time-of-fligth wall
Deppner, I.; Herrmann, N.; Gonzalez-Diaz, D.; Ammosov, V.; Cheng, J.; Ciobanu, M.; Gapienko, V.; Hildenbrand, K. D.; Kiselieva, A.; Kis, M.; Kresan, D.; Kotte, R.; Huangshan, C.; Leifels, Y.; Li, C.; Li, Y.; Loizeau, P. A.; Naumann, L.; Petrovici, M.; Petris, M.; Semak, A.; Simion, V.; Stach, D.; Sun, Y.; Sviridov, Y.; Tang, Z.; Usenko, E.; Wang, J.; Wang, Y.; Wisnieswki, K.; Wüstenfeld, J.; Xu, L.; Zaets, V.; Zhang, Y.; Zhu, X.;
The key element providing hadron identification in the future Compressed Baryonic Matter spectrometer at FAIR is a time-of-flight wall placed at 10 m distance from the target. The most promising technological option for such a task consists on a 150 m² carpet based on Resistive Plate Chambers. Due to the fixed-target geometry, the conceptual design foresees two extreme regions: an outermost region (low rate/low multiplicity) covered by float glass RPCs in multi-strip fashion, and a central region (high rate/high multiplicity) consisting of densely packed read-out cells made with low resistive electrodes. The status of the ongoing R&D efforts in both regions is presented.

Publ.-Id: 14729 - Permalink


Electrical and Magnetic Properties of Polycrystalline Mn-Doped BaTiO3 Thin Films Grown on Pt/Sapphire Substrates by Pulsed Laser Deposition
Shuai, Y.; Zhou, S. Q.; Schmidt, H.;
5 at.% Mn-doped and undoped, 200 nm thick BaTiO3 thin films have been grown under different oxygen partial pressures by pulsed laser deposition on Pt/sapphire substrates. X-ray diffraction (XRD) measurements reveal the same polycrystalline single-phase perovskite structure for all the thin films despite the different oxygen partial pressure, while their preferred orientation strongly depends on the oxygen partial pressure. The 5 at. % Mn-doping decreases the dielectric loss of the Mn-doped BaTiO3 thin films, however, their relative permittivity is also decreased. Ferroelectricity has been probed on the Mn-doped and undoped BaTiO3 thin films grown under relatively high oxygen partial pressure. A ferromagnetic coupling of the Mn dopant ions has been probed at room tempetature on the Mn-doped BaTiO3 thin films prepared under low oxygen partial pressure and is understood in terms of the bound magnetic polaron model.
Keywords: multiferroics, ferroelectricity, magnetism, barium titanate, bound magnetic polarons
  • Contribution to proceedings
    12th INTERNATIONAL CERAMICS CONGRESS, 06.-11.06.2010, Montecatini Terme, Tuscany, Italy
    Electrical and Magnetic Properties of Polycrystalline Mn-Doped BaTiO3 Thin Films Grown on Pt/Sapphire Substrates by Pulsed Laser Deposition

Publ.-Id: 14728 - Permalink


CFD-Analyses on the behaviour of mineral wool in the reactor sump
Krepper, E.; Grahn, A.; Cartland-Glover, G.; Weiss, F.-P.; Alt, S.; Kratzsch, A.; Renger, S.; Kästner, W.;
The investigation of insulation debris generation, transport and sedimentation becomes important with regard to reactor safety research for PWR and BWR, when considering the long-term behaviour of emergency core cooling systems during all types of loss of coolant accidents. A joint research project on such questions is being performed in cooperation between the University of Applied Sciences Zittau/Görlitz and the Forschungszentrum Dresden-Rossendorf. The project deals with the experimental investigation of particle transport phenomena in coolant flow and the development of CFD models for its description. While the experiments are performed at the University at Zittau/Görlitz, the theoretical modelling efforts are concentrated at Forschungszentrum Dresden-Rossendorf. In the current presentation the basic concepts for CFD modelling are described and feasibility studies are presented. On the example of a complex flow situation at plunging jet conditions the model capabilities are demonstrated.
Keywords: Insulation material transport, CFD, plunging jet
  • Contribution to proceedings
    Fachtagung der KTG-Fachgruppen, 07.-08.10.2010, Rossendorf, Deutschland
    Aktuelle Themen der Reaktorsicherheitsforschung in Deutschland
  • Invited lecture (Conferences)
    Aktuelle Themen der Reaktorsicherheitsforschung in Deutschland Fachtagung der KTG-Fachgruppen, 07.-08.10.2010, Rossendorf, Deutschland

Publ.-Id: 14727 - Permalink


Development of Multi-Physics Code Systems based on the Reactor Dynamics Code DYN3D
Kliem, S.; Gommlich, A.; Grahn, A.; Rohde, U.; Schütze, J.; Frank, T.; Gomez, A.; Sanchez, V.;
In the presentation the recent developments of the coupling of the reactor dynamics code DYN3D with the coarse-mesh CFD code FLICA-4 and the CFD code ANSYS CFX are presented. First results of verification calculations for small-size test problems confirm the correctness of the implementation of the coupling.
  • Invited lecture (Conferences)
    Fachtag der KTG: "Aktuelle Themen der Reaktorsicherheitsforschung in Deutschland", 07.-08.10.2010, Dresden, Deutschland
  • Contribution to proceedings
    Fachtag der KTG: "Aktuelle Themen der Reaktorsicherheitsforschung in Deutschland", 07.-08.10.2010, Dresden, Deutschland
    Tagungsband des Fachtages der KTG: "Aktuelle Themen der Reaktorsicherheitsforschung in Deutschland", CDROM: FZ Dresden-Rossendorf
  • Kerntechnik 76(2011)3, KT100569

Publ.-Id: 14726 - Permalink


Medical Impact of Polynuclear Cluster Compounds
Stephan, H.; Müller, C. E.;
Polynuclear metal compounds may have considerable potential as metallic drugs. The most prominent representatives are polyoxometalates which have been investigated since the last third of the 19th century. In addition to applications in catalysis, separation, analysis, and as electron-dense imaging agents, some of these substances have been shown to exhibit biological activity in vitro as well as in vivo ranging from anti-cancer, antibiotic, and antiviral to anti-diabetic effects.1
Polymetalates represent a diverse ensemble of nanostructures with an almost infinite variability of chemical, physical and biological properties. The size of typical covalent bridged cluster compounds is in the range from 1 to 3 nm. The attachment of special surface groups on the periphery of cluster compounds may result in self-assembled non-covalent organized structures larger than 5 nm which are characteristic for bio-molecules, such as enzymes. Cells of mammalian organisms are typically 10 to 30 µm. However, sub-cellular organelle dimensions are smaller and range in sub-µm sizes. This comparison of size dimension illustrates that polymetalates are small enough to allow the cell membrane to be penetrated without too much interference. Evidently, some types of polymetalates are able to be transported into cells, particularly into mitochondria. Our aim is focused on the development of novel cluster compounds with improved chemical and metabolic stability. Furthermore, increased recognition of target biomolecules - such as enzymes - shall be achieved.
On the way to explore the biological activity of polynuclear cluster compounds, we recently recognised polyoxometalates as a new class of potent enzyme inhibitors.2 Certain polymetalates are able to inhibit E-NTPDases (ecto-nucleoside triphosphate diphosphohydrolases) that are surface-located nucleotide-hydrolyzing enzymes involved in the regulation of signaling cascades by activating P2 (nucleotide) receptors. The most potent compound - described to date – is K6H2[TiW11CoO40] I exhibiting IC50 values which are significantly lower than those of known standard inhibitors. Some compounds are also able to directly interact with P2 receptors. A further promising new class of cluster compounds to permit selective inhibition of E-NTPDases are hexanuclear rhenium complexes with bridging sulfur, selenium and/or tellurium atoms. In this perspective, a broad ensemble of water-soluble octahedral rhenium cluster compounds II becomes available by ligand exchange reactions.3
The paper will give a brief overview about the potential of inorganic cluster compounds in medicine as well as a survey of recent progress that was achieved on E-NTPDase inhibition and P2 receptor antagonism with polymetalates.

[1] J. T. Rhule, C. L. Hill, D. A. Judd, R. F. Schinazi, Chem. Rev.1998, 98, 327-357.
[2] C. E. Müller, J. Iqbal, Y. Baqi, H. Zimmermann, A. Röllich, H. Stephan, Bioorg. Med. Chem. Lett. 2006, 16, 5943-5947.
[3] K. A. Brylev, Y. V. Mironov, S. Kozlova, V. E. Fedorov, S.-J. Kim, H.-J. Pietzsch,
H. Stephan, A. Ito, S. Ishizaka, N. Kitamura, Inorg. Chem. 2009, 48, 2309-2315.
  • Lecture (Conference)
    IWTMC-II International Workshop on Transition Metal Clusters-II, 30.09.-02.10.2010, Rostock, D

Publ.-Id: 14725 - Permalink


A novel Dibenzoazacyclooctyne precursor in regioselective Copper-free click chemistry. An innovative 3-step synthesis.
Starke, F.; Walther, M.; Pietzsch, H.-J.;
A novel carboxylic acid substituted dibenzoazacyclooctyne precursor has been synthesized using a fast and innovative three-step synthesis. It can be easily converted into the corresponding alkyne through UV-irradiation. Due to its fast and regioselective reaction with azides, the alkyne is a promising agent for copper-free "click chemistry". The second order reaction rate constant was determined by 1H-NMR.
  • Open Access LogoARKIVOC (2010), 350-359

Publ.-Id: 14724 - Permalink


Nanotribology of lubricated carbon-based nanocoatings
Kunze, T.; Posselt, M.; Gemming, S.; Seifert, G.;
Nanocoatings have the potential to improve the surface properties of various materials. They are of extreme importance for surfaces in sliding lubricated contact such as highly stressed automotive engine parts. Here, nanocoatings have to be optimized with respect to low friction properties and a high wear resistance to enhance the energetic and environmental efficiency. An additional variation of the tribological characteristics arises due to the presence of the fuel as the lubricant.
The present study employs atomic-scale simulations in order to assist the manufacturing and optimization of functional nanocoatings. Our investigations focus on two basic functional film species - tetrahedral amorphous carbon (ta-C) and transition metal enriched carbon (TM:C) coatings. These films are modeled and studied with the help of bond-order potentials such as the reactive empirical bond-order (REBO) potential [1] for carbon-carbon interaction and the Shibuta potential [2] for TM-carbon interaction. Our simulations also incorporate an adaptive cutoff scheme, which is able to enhance the REBO potential characteristics [3]. Since the tribological properties of lubricated engine parts depend not only on the properties of the nanocoatings but also on the lubricant, the hydrocarbon dodecan is selected as a representative of the fuel in the automotive engines. Preliminary results on the ta-C film morphology and its tribological properties such as friction coefficients with and without lubrication are presented.

[1] D. W. Brenner et al., J. Phys.: Condens. Matter 14 (2002) 783
[2] Y. Shibuta et al., Chem. Phys. Lett. 472 (2009) 200
[3] L. Pastewka et al., Phys. Rev. B 78 (2008) 161402
Keywords: nanotribology, diamond-like carbon, atomistic simulations
  • Poster
    5th Int. Conf. Multiscale Materials Modeling (MMM2010), Symposium Tribology, 04.-08.10.2010, Freiburg, Deutschland
  • Contribution to proceedings
    5th Int. Conf. Multiscale Materials Modeling (MMM2010), 04.-08.10.2010, Freiburg, Deutschland
    Conference Proceedings MMM2010, Stuttgart: Fraunhofer Verlag, 978-3-8396-0166-2, 858

Publ.-Id: 14723 - Permalink


Status of atomic-level simulations of solid phase epitaxial recrystallization of amorphous Si
Posselt, M.;
In semiconductor technology amorphous Si layers are formed by ion implantation, and during subsequent annealing the solid phase epitaxial recrystallization (SPER) of the amorphous material takes place. In order to simulate the SPER process and to understand its atomic-level mechanisms, classical molecular dynamics calculations are employed since they allow the consideration of several thousand atoms and a time scale up to some hundreds of nanoseconds. In the last decade different authors investigated SPER in Si by this type of simulations, but the critical review shows that their results are not consistent with the experimental data. In most cases the SPER rate was strongly overestimated. Moreover, the results obtained by different groups under virtually equal conditions do not agree. This may be due to the different approaches used to prepare the initial state consisting of an atomic system with a nearly planar amorphous-crystalline interface. The main cause for the disagreement with experimental data is the inaccuracy of the interatomic potentials used in the different studies. The improvements considered in the present work 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 found that amorphous Si with realistic structural and thermodynamic properties can be obtained by certain modifications of known interatomic potentials, but these modifications do not yield the correct SPER rate. However, it is shown that the value of the SPER rate is strongly correlated with the melting temperature of amorphous silicon obtained by the corresponding modified potential. Obviously, this dependence can be explained by the fact that both melting and SPER are essentially determined by the flexibility of atomic bonds. The atomic mechanism of SPER consists in sequential local arrangements of atomic bonds and positions, preferentially along {111} facets or terraces.
Keywords: epitaxial recrystallization, Si, atomistic computer simulations
  • Lecture (Conference)
    5th Int. Conf. Multiscale Materials Modeling (MMM2010), Symposium Microstructure Modeling, 04.-08.10.2010, Freiburg, Deutschland
  • Contribution to proceedings
    5th Int. Conf. Multiscale Materials Modeling (MMM2010), 04.-08.10.2010, Freiburg, Deutschland
    Conference Proceedings MMM2010, Stuttgart: Fraunhofer Verlag, 978-3-8396-0166-2, 509

Publ.-Id: 14722 - Permalink


Applications of 100TW class ultrashort-pulse lasers
Schramm, U.;
first steps to laser driven radiation oncology
and the future of the Dresden laser lab
  • Lecture (Conference)
    Superstrong fields in plasmas, 03.-08.10.2010, Varenna, Italien

Publ.-Id: 14721 - Permalink


Nano-Biotechnologie für den Umweltschutz: Neue photokatalytisch aktive Verbundmaterialien zur Eliminierung von pharmazeutischen Reststoffen (NanoPharm)
Pollmann, K.; Raff, J.;
Vorstellung des BMBF-geförderten "NanoPharm"-Projekts
  • Lecture (others)
    4. MITTELDEUTSCHES NETZWERKTREFFEN, 30.11.2010, Magdeburg, Deutschland

Publ.-Id: 14720 - Permalink


Bioinspired nanomaterials
Raff, J.;
Protecting the environment and saving resources are two of the society’s challenges of the 21th century. Therefore interesting insights coming also from nature. As many bacteria and archaea live in extreme habitats, they developed early in evolution so called surface layers (S-layers), which function as intelligent interface between cells and their environment. One function of such S-layers is the binding of toxic metals and metalloids and thusly the protection of the cells from being damaged by these elements and their compounds. This makes, together with their self-assembling properties, S-layer very interesting building blocks for the construction of new bioinspired nanomaterials for different technical applications. Currently under development are materials for the selective metal-binding for the removal of toxic metals and metalloids or the recovery of precious metals, highly efficient (photo)catalysts for the elimination of organic pollutants or organic synthesis and new biosensors for chemicals or pharmaceuticals.
Keywords: S-layer, nanomaterials
  • Lecture (others)
    nanoSeminar des Instituts für Werkstoffwissenschaft, TU Dresden, 11.11.2010, Dresden, Deutschland

Publ.-Id: 14719 - Permalink


Domains and Dynamics in NiMnGa
Neudert, A.; Schäfer, R.; McCord, J.;
Magnetic domains in the shape memory alloy NiMnGa are investigated using magneto-optical indicator film technique. Depending on whether the twin boundary is moved by applying mechanical stress or magnetic fields a different domain state is found after twin boundary motion.
  • Lecture (Conference)
    SPP Convention Tutzing, 29.09.2010, Tutzing, Germany

Publ.-Id: 14718 - Permalink


Local patterning of damping by ion-irradiation In ferromagnetic-antiferromagnetic thin films
McCord, J.; Mönch, I.; Strache, T.; Fassbender, J.ORC; Mattheis, R.
The control of the effective magnetic anisotropy, saturation magnetization as well as the dynamic magnetic properties in ferromagnetic thin films is of significant importance for most applications in spin electronics. The two materials’ parameters which control the dynamic response of soft magnetic thin films are the precessional frequency f_res and the effective damping parameter alpha. Whereas anisotropy and saturation magnetization together determine the precessional frequency of the films, the magnetic damping parameter cannot be varied easily. However it was shown that exchange coupled ferromagnetic/antiferromagnetic (F/AF) systems exhibit strong changes in f_res and alpha independent of the occurrence of exchange bias [1, 2]. On the other hand, ion irradiation of magnetic thin films [3] has been shown to provide an alternative method to alter soft magnetic properties of magnetic multilayer films due to ion induced changes in the interfacial structure. Here we use Ni-ion irradiation to control the dynamic magnetic properties in Ni81Fe19/IrMn/Ni81Fe19 structures in a controlled way. We show that for very thin AF layers alpha can be increased significantly [4]. Selecting an IrMn thickness below the onset of exchange bias, it is possible to solely alter alpha. This effect is reversible by low fluence Ni ion irradiation without changing the composition of the ferromagnetic alloy and thus can be used to adjust alpha over a wide range. As a consequence, the method can be used to laterally pattern samples only by the damping parameter. As shown in Fig. 1 the overall integral damping parameter then is determined by the relative fraction of materials with high and low damping parameter. alpha is thereby varied linearly without any significant change in f_res. The demonstrated paths of film alteration by ion irradiation provide an additional degree of freedom for the tailoring of dynamic magnetic properties of softmagnetic thin films. The method not only allows for general adjustment of magnetic properties, but also for a local setting of dynamic magnetic properties.
This work was supported by the German Science Foundation DFG under grant no. MC9-8/2.

[1] J. McCord et al., Phys. Rev. B 70, 094420 (2004)
[2] J. McCord et al., Phys. Rev. B 75, 134418 (2007).
[3] J. Fassbender and J. McCord, J. Magn. Magn. Mater. 320, 579 (2008).
[4] J. McCord, et al., Appl. Phys. Lett. 92 162506 (2008).
  • Lecture (Conference)
    IEEE 7th International Symposium on Metallic Multilayers (MML2010), 20.-24.09.2010, Berkeley, USA

Publ.-Id: 14717 - Permalink


Domain width effects on the magneto-dynamic response of CoFeB element arrays
Patschureck, C.; McCord, J.; Schäfer, R.; Mattheis, R.; Schultz, L.;
Understanding the role of the magnetic domain structure on the magneto-dynamic properties of patterned magnetic thin film structures is crucial for the optimization of devices, e.g. recording heads and integrated inductors. Arrays of rectangular amorphous Co40Fe40B20 elements of micron size, a separation to width ratio of 1.5 and a thickness of 60 nm have been fabricated. Magneto-optical Kerr microscopy was used to study the domain structure. At zero field closure domain patterns are present whereas the domain width was systematically altered by varying the magnetic field history. The magneto dynamic response of different domain patterns with adjusted domain width was measured using pulsed inductive microwave magnetometry. We show that the resonance frequency is the lowest for broad closure domain structures and increases when the domain width is decreased.
  • Lecture (Conference)
    Joint European Magnetic Symposia JEMS 2010, 25.08.2010, Krakow, Poland

Publ.-Id: 14716 - Permalink


Spatially controlled manipulation of damping in ferromagnetic thin films
McCord, J.; Strache, T.; Mönch, I.; Fassbender, J.ORC; Mattheis, R.
The control of dynamic magnetic properties in ferromagnetic thin films is of significant importance for applications in spin electronics. We demonstrate the use of low fluence Ni-ion irradiation to locally and solely tailor the magnetic damping parameter e in ferromagnetic-antiferromagnetic Ni81Fe19/IrMn/Ni81Fe19 sandwich structures. The overall relaxation time then depends on the relative fraction of the phases with different e , which thereby can be controlled without changing the precessional frequency. The superposition of alpha is confirmed by modeling of the dynamic response. The demonstrated path of film engineering by local ion irradiation [J. Fassbender, J. McCord, JMMM 320 (2008) 579] provides an additional degree of freedom for the local tailoring of dynamic magnetic properties of soft-magnetic thin films.
  • Lecture (Conference)
    Joint European Magnetic Symposia JEMS 2010, 27.08.2010, Krakow, Poland

Publ.-Id: 14715 - Permalink


P0806 Verfahren und Anordnung zum Nachweis von Östrogen in wässrigen Lösungen
Cherkouk, C.; Rebohle, L.; Skorupa, W.;
Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren zum schnellen Nachweis von Östrogen in wässrigen Lösungen vor Ort zu realisieren. Der Nachweis basiert auf einer Fluoreszenzanalyse, wobei eine integrierte Lichtquelle mit einer bioaktiven Schicht auf deren Oberfläche verwendet wird. Die bioaktive Schicht wird durch ein spezielles Hybridisierungs- und Silanisierungsverfahren erzeugt. Die Messung erfolgt durch die optische Detektion farbstoffmarkierter Hormonmoleküle, die nach einem bestimmten Messprotokoll die Rezeptoren belegen, die noch nicht durch Hormone aus der Messprobe gesättigt worden sind.
  • Patent
    Anmeldung: DE102008024526 A1 2009/12/03

Publ.-Id: 14714 - Permalink


Optical and microstructural properties of self-assembled InAs quantum structures in silicon
Prucnal, S.; Turek, M.; Drozdziel, A.; Pyszniak, K.; Wójtowicz, A.; Zhou, S. Q.; Kanjilal, A.; Shalimov, A.; Skorupa, W.; Zuk, J.;
The InAs quantum structures were formed in silicon by sequential ion implantation and subsequent thermal annealing. Samples were characterized by micro-Raman spectroscopy, Rutherford backscattering spectrometry (RBS), low temperature photoluminescence (PL), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). Two kinds of crystalline InAs nanostructures were successfully synthesized:quantum dots (QDs) and nanopyramides (NPs). The Raman spectrum shows two peaks at 215 and 235 cm-1 corresponding to the transverse optic (TO) and longitudinal optic (LO) InAs single-phonon modes, respectively. The narrow PL band at around 1.3 mm due to the excitation of InAs QDs with an average diameter 7.5 ± 0.5 nm was observed. The InAs NPs were found only in samples annealed for 20 ms at temperatures ranging from 1000 up to 1200 oC. The crystallinity and pyramidal shape of InAs quantum structures were confirmed by HRTEM and XRD techniques. The average size of the NPs is 50 nm base and 50 nm high and they are oriented parallel to the Si (001) planes. The lattice constant of the NPs increases from 6.051 to 6.055 Ǻ with the annealing temperature increasing from 1100 to 1200 oC due to network relaxation. Energy dispersive spectroscopy (EDS) shows almost stoichiometric composition of the InAs NPs.
Keywords: InAs, nanopyramid, quantum dots, flash lamp annealing, ion implantation
  • Poster
    E-MRS 2010 Spring Meeting, 07.-11.06.2010, Strasbourg, France

Publ.-Id: 14713 - Permalink


Electro-Optical Properties of Solar Cell Emitters Fabricated by Plasma Immersion Ion Implantation and Flash Lamp Millisecond Annealing
Prucnal, S.; Skorupa, W.; Abendroth, B.; Krockert, K.; Möller, H. J.;
Both mono- and multicrystalline p-type silicon wafers were used for the phosphorous ion implantation. After ion implantation the silicon is strongly disordered or amorphous within the ion range. Therefore subsequent annealing is required to remove the implantation damage and to activate the doping element. During FLA, only the wafer surface is heated homogeneously to very high temperatures at ms time scales, resulting in the annealing of the implantation damage and an electrical activation of the phosphorous. It is demonstrated that FLA at 800 oC for 20 ms even without preheating is sufficient to recrystallized implanted silicon. The highest recrystallization and the lowest resistivity were obtained after annealing at 1200 oC for 20 ms both for mono- and multicrystalline silicon wafers. Photoluminescence results point towards P - cluster formation at high annealing temperatures which effects on metal impurity gettering within the emitter.
Keywords: c-Si, mc-Si, ion implantation, FLA, solar cells
  • Poster
    26th European Photovoltaic Solar Energy Conference and Exhibition (26th EU PVSEC), 05.-09.09.2010, Valencia, Spain

Publ.-Id: 14712 - Permalink


P0801 Anordnung zur dreidimensionalen Elektronenstrahltomographie
Hampel, U.;
Aufgabe der vorliegenden Erfindung ist es, eine Anordnung zur Röntgen-Computertomographie anzugeben, die eine kontinuierliche dreidimensionale Abbildung des Untersuchungsobjektes bzw. eines Teilvolumens des Untersuchungsobjektes bei hoher zeitlicher und räumlicher Auflösung gestattet, wobei mit hoher räumlicher Auflösung sowohl eine hohe Auflösung innerhalb der Schnittebene als auch in axialer Richtung definiert ist.
  • Patent
    Anmeldung: DE 102008005718A1 2009/07/30
  • Patent
    Anmeldung: WO 2009092372A1: Offenlegung-30.07.2009; Nationaliserung in US, EP

Publ.-Id: 14711 - Permalink


Solar cell emitters fabricated by flash lamp millisecond annealing
Prucnal, S.; Shumann, T.; Skorupa, W.; Abendroth, B.; Krockert, K.; Möller, H. J.;
Phosphorous ion implantation was used for the emitter formation in mono- and multicrystalline silicon solar cells. After ion implantation the silicon is strongly disordered or amorphous within the ion range. Therefore subsequent annealing is required to remove the implantation damage and to activate the doping element. Flash-lamp-annealing (FLA) offers here an alternative route for the emitter formation at an overall low thermal budget. During FLA, only the wafer surface is heated homogeneously to very high temperatures at ms time scales, resulting in the annealing of the implantation damage and an electrical activation of the phosphorous. However, variation of the pulse time also allows to modify the degree of annealing of the bulk region to some extent as well, which can have an influence on the gettering behaviour of metallic bulk impurities.
The μ-Raman spectroscopy showed that the silicon surface is amorphous after ion implantation. It could be demonstrated that FLA at 800°C for 20 ms even without preheating is sufficient to recrystallize implanted silicon. The highest carrier concentration and efficiency and the lowest resistivity were obtained after annealing at 1200°C for 20 ms both for mono- and multicrystalline silicon wafers. Photoluminescence results point towards P-cluster formation at high annealing temperatures which effects on metal impurity gettering within the emitter.
Keywords: Solar cells, silicon, Flash Lamp Annealing
  • Open Access LogoActa Physica Polonica A 120(2011)1, 30-34

Publ.-Id: 14710 - Permalink


Optical and microstructural properties of In(As, N) quantum structure made by ion implantation and flash lamp processing
Prucnal, S.; Turek, M.; Drozdziel, A.; Pyszniak, K.; Wójtowicz, A.; Kanjilal, A.; Shalimov, A.; Skorupa, W.; Żuk, J.;
The In(As, N) quantum structures were formed in silicon, SiO2 and Si3N4 films by sequential ion implantation and subsequent thermal annealing. Samples were characterized by -Raman spectroscopy, Rutherford backscattering spectrometry (RBS), low temperature photoluminescence (PL), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). Two kinds of crystalline InAs nanostructures were successfully synthesized: quantum dots (QDs) and nanopyramides (NPs). The Raman spectrum shows two peaks at 215 and 235 cm-1 corresponding to the transverse optical (TO) and longitudinal optical (LO) InAs phonon modes, respectively. The narrow PL band at around 1.3 m from the InAs QDs with an average diameter 7.5 ± 0.5 nm was observed.
The InAs NPs were found only in samples annealed for 20 ms at temperature range from 1000 up to 1200 oC. The crystallinity and pyramidal shape of InAs quantum structures were confirmed by high resolution transmission electron microscopy (HRTEM) (see Fig. 1) and X-ray diffraction (XRD). The average size of the NPs is 50 nm base and 50 nm high and they are oriented parallel to the Si (001) planes. The InAs nanopyramids grow in silicon due to liquid phase epitaxy. The InN crystals are formed on the top of silicon nitride layer due to outdiffusion of indium and in Si3N4 film. The PL measurements shows narrow band at around 1.35 m originated from hexagonal InN nanocrystals due to quantum confinement size effect. -Raman scattering study shows two peaks at 495 and 588 cm-1, which correspond to (TO) of E2h and (LO) of A1 phonon modes, respectively.
Keywords: InAs, InN, Quantum dots, photoluminescence, FLA
  • Lecture (Conference)
    VIII-th International Conference Ion Implantation and Other Applications of Ions and Electrons, 14.-17.06.2010, Kazimierz Dolny, Poland

Publ.-Id: 14709 - Permalink


P0808 Verfahren und Anordnung zur Reinigung des Reaktionsgemisches bei der Herstellung von Radiopharmaka
Füchtner, F.; Mäding, P.; Preusche, S.; Zessin, J.;
Die Erfindung betrifft die Herstellung von Radiopharmaka, insbesondere in Verfahren, und eine Anordnung zur Reinigung des Reaktionsgemisches bei der Herstellung von Radiopharmaka, insbesondereF-markierte Radiopharmaka, wie z. B. [F]FDOPA und [F]OMFD sowie [F]FMeMcN. Erfindungsgemäß wird zur Reinigung des Raktionsgemisches eine Vorsäule als Vorreinigungssäule, gefüllt mit RP-Material (Reversed Phase Material), zur Abtrennung des bei der Reaktion verwendeten Lösungsmittels (Matrix) bzw. unerwünschter Nebenprodukte verwendet, während die eigentliche chromatographische Trennung des Reaktionsgemisches auf einer HPLC-Säule, bevorzugt einer RP-HPLC-Säule, durchgeführt wird.
  • Patent
    Anmeldung: DE 102009009344 A1 2010/09/02
  • Patent
    Anmeldung: WO201088901A1 2010/02/05

Publ.-Id: 14708 - Permalink


Magnetic Anisotropy of Thin Magnetic Films on Nanometer Scale Silicon Ripples
Ball, D.; Liedke, M. O.; Lenz, K.; Fritzsche, M.; Yilgin, R.; Keller, A.; Ranjan, M.; Facsko, S.; Fassbender, J.ORC
Ion beam erosion techniques allow for the creation of well-ordered substrate ripples with nanometer periodicity. Moreover, the periodicity can be tuned by changing the ion beam energy over a wide range [1]. The ripple pattern is directly transferred into films grown on these substrates. This offers the possibility of tailoring the magnetic properties by inducing additional magnetic anisotropy due to the structural modifications.
We study the influence of rippled vs. flat Si substrates for 10 nm thin Fe and Co films, as well as technologically relevant Heusler alloys (Fe3Si and Co2FexMn1-xSi). The magnetic anisotropy is measured by frequency and angle dependent vector network analyzer ferromagnetic resonance. The ripple morphology of the magnetic layers induces a strong uniaxial magnetic anisotropy.
Keywords: Vector network analyzer ferromagnetic resonance, Co2FexMn1-xSi, Fe3Si, rippled morphology
  • Poster
    Nanofair, 06.-07.07.2010, Dresden, Germany

Publ.-Id: 14707 - Permalink


P0802 Hochgeordnete Nanostrukturen und Sensor und deren Verwendung
Pollmann, K.; Raff, J.; Fahmy, K.;
Die vorliegende Erfindung betrifft eine hochgeordnete Nanostruktur und Sensor, in der bzw. dem organische Molekülgruppen, die spezifische Bindungseigenschaften für ein Zielmolekül haben, geordnet gebunden sind, und deren Verwendung. Anwendungsgebiet dafür finden sich in der Biotechnologie, Verfahrenstechnik, Umwelttechnik und Pharmazie, insbesondere bei der Herstellung von Biosensoren, in der biomedizinischen Analytik, bei der Beseitigung von Schadstoffen und Pathogenen, in der DNA-Analytik, für die Herstellung von Filtermaterialien, für Separationsverfahren, für Katalysatoren und in der medizinischen Therapie. Die Aufgabe der Erfindung ist es, eine Struktur zur Verfügung zu stellen, in der organische Molekülgruppen, insbesondere Molekülgruppen, die spezifische Bindungseigenschaften haben, geordnet gebunden sind, und dadurch die von den organischen Molekülgruppen gebundenen Substanzen in die Nähe funktioneller Bestandteile zu bringen. Dies wird gelöst durch eine Nanostruktur, die selbstorganisierende Proteine, an die Aptamere oder andere organische Molekülgruppen, die spezifische Bindungseigenschaften für ein Zielmolekül aufweisen, gebunden sind, und an die selbstorganisierenden Proteine gebundene anorganische Nanopartikel enthält.
  • Patent
    Anmeldung: DE 102008014298 A1 2009/09/24
  • Patent
    Anmeldung: EP 2101175 A1 2009/09/16

Publ.-Id: 14706 - Permalink


Solar cell emitters fabricated by plasma immersion ion implantation and flash lamp millisecond annealing
Prucnal, S.; Skorupa, W.; Abendroth, B.; Krockert, K.; Möller, H. J.;
Both mono- and multicrystalline p-type silicon wafers were used for the implantation of phosphorous. After ion implantation the silicon is strongly disordered or amorphous within the ion range. Therefore subsequent annealing is required to remove the implantation damage and to activate the doping element. Flash-lamp-annealing (FLA) offers here an alternative route for the emitter formation at an overall low thermal budget. During FLA, only the wafer surface is heated homogeneously to very high temperatures at ms time scales, resulting in the annealing of the implantation damage and an electrical activation of the phosphorous. However, variation of the pulse time also allows to modify the degree of annealing of the bulk region to some extent as well, which can have an influence on the gettering behaviour of metallic bulk impurities.
The μ-Raman spectroscopy showed that the silicon surface is amorphous after ion implantation. It could be demonstrated that FLA at 800oC for 20 ms even without preheating is sufficient to recrystallize implanted silicon. The highest carrier concentration and efficiency and the lowest resistivity were obtained after annealing at 1200oC for 20 ms both for mono- and multicrystalline silicon wafers. Photoluminescence results point towards P-cluster formation at high annealing temperatures which effects on metal impurity gettering within the emitter.
Keywords: solar cells, FLA,silicon
  • Poster
    VIII-th International Conference Ion Implantation and Other Applications of Ions and Electrons, 14.-17.06.2010, Kazimierz Dolny, Poland

Publ.-Id: 14705 - Permalink


Formation of InAs quantum dots in silicon by sequential ion implantation and flash lamp annealing
Prucnal, S.; Turek, M.; Drozdziel, A.; Pyszniak, K.; Zhou, S. Q.; Kanjilal, A.; Zuk, J.; Skorupa, W.;
InAs quantum dots (QDs) were successfully formed in single-crystalline Si by sequential ion implantation and subsequent milliseconds range flash lamp annealing (FLA). Samples were characterized by μ-Raman spectroscopy, Rutherford Backscattering Spectrometry (RBS) high-resolution transmission electronmicroscopy (HRTEM) and low temperature photoluminescence (PL). The Raman spectrum shows two peaks at 215 and 235 cm−1 corresponding to the transverse optical (TO) and longitudinal optical (LO) InAs phonon modes, respectively. The PL band at around 1.3 μm originates from the InAs QDs with an average diameter 7.5±0.5 nm and corresponds to the increased band gap energy due to the strong quantum confinement size effect. The FLA of 20 ms is sufficient for InAs QDs formation. It also prevents the out-diffusion of implanted elements.
Moreover, the silicon layer amorphized during ion implantation is recrystallized by solid-phase epitaxial regrowth during FLA.
Keywords: InAs, Quantum Dots, Si, photoluminescence, FLA

Publ.-Id: 14704 - Permalink


Comparison of the room temperature 1.53 μm Er photoluminescence from flash lamp and furnace annealed Er-doped Ge-rich SiO2 layers
Kanjilal, A.; Prucnal, S.; Rebohle, L.; Voelskow, M.; Helm, M.; Skorupa, W.;
The furnace and flash-lamp annealing (FLA) temperature dependent variation in the room temperature 1.53 μm Er photoluminescence (PL) from Er-doped Ge-rich SiO2 layers is investigated. The appearance of the 1.53 μm Er PL is discussed in the framework of the phonon-assisted fluorescent resonant energy transfer from Ge-related luminescence-centers (LCs) to the Er3+. Detailed analyses suggest that in case of FLA the decrease in the 1.53 μm Er PL intensity is governed by the temperature dependent recrystallization of Ge nanoclusters, while for furnace-annealing it is associated with the reduction in the LC-Er3+ coupling due to Ge out-diffusion and the formation of Er-rich clusters with increasing temperature.
Keywords: rare earth, electroluminescence, MOSLED, Flash Lamp Annealing

Publ.-Id: 14703 - Permalink


Infrared magneto-spectroscopy using quantum cascade lasers
Drachenko, O.; Winnerl, S.; Schneider, H.; Helm, M.; Leotin, J.;
We present a magneto-transmission experimental set up covering spectral region from 5 to 120 µm. Interchangable quintum cascade lasers are used as an excitation sources. Performance of the setup is illustrated via cyclotron resonance studies of InGaAs/GaAs QWs under magnetic fields up to 60T
Keywords: Cyclotron resonance, quantum cascade laser, high magnetic fields
  • Lecture (Conference)
    The 35th International Conference on Infrared, Millimeter and THz Waves (IRMMW-THz 2010), 05.-10.09.2010, Rome, Italy
  • Contribution to proceedings
    The 35th International Conference on Infrared, Millimeter and THz Waves (IRMMW-THz 2010), 05.-10.09.2010, Rome, Intaly: IEEE, 345 E 47TH ST, NEW YORK, NY 10017 USA, 978-1-4244-6657-3

Publ.-Id: 14702 - Permalink


Nucleation of copper-vacancy clusters in bcc-Fe: An atomistic study
Al-Motasem, A. T.; Posselt, M.; Bergner, F.;
Copper-rich precipitates are assumed to be the main cause of hardening and embrittlement of Cu-bearing reactor pressure vessel steels since they act as obstacles to dislocation motion within the grains of the polycrystalline bcc-Fe. Multiscale modeling contributes to a better understanding of point-defect-enhanced formation of these clusters during reactor operation. Rate theory is an efficient tool to simulate the cluster evolution on realistic time and length scales. However, many parameters used in rate theory, such as the diffusion coefficients of mobile species and the free binding energies of clusters, are not very well known from experimental investigations. Atomic-level computer simulations can provide these data. In the present work the nucleation free energy is determined for pure copper and pure vacancy clusters as well as for mixed clusters up to a maximum cluster size of 200. The energetics of the coherent CunVm clusters in bcc-Fe is obtained using a combination of on-lattice Monte Carlo simulations and off-lattice molecular dynamics. The most recent Fe-Cu interatomic potential by Pasianot and Malerba [1] is employed in the calculations.
[1] R. C. Pasianot and L. Malerba, J. Nucl. Mater. 360, 118 (2007).
Keywords: Lattice Monte Carlo, Nucleation of Cu-vacancy Cluster, free binding energy.
  • Poster
    Nuclear Materials 2010, An international conference in association with Journal of Nuclear Materials, 04.-07.10.2010, Karlsruhe, Germany

Publ.-Id: 14701 - Permalink


Traumatic Brain Injury Elicits Similar Alterations in α7 Nicotinic Receptor Density in Two Different Experimental Models
Hoffmeister, P.-G.; Donat, C. K.; Schuhmann, M. U.; Voigt, C.; Walter, B.; Nieber, K.; Meixensberger, J.; Bauer, R.; Brust, P.;
Traumatic brain injury (TBI) is a major cause of death and disability worldwide, especially in children and young adults. Previous studies have shown alterations in the central cholinergic neurotransmission after TBI. We therefore determined α7 nicotinic acetylcholine receptor (nAChR) densities in newborn piglets and adult rats after experimental TBI. Thirteen newborn piglets (post-TBI survival time: 6 h) underwent fluid percussion (FP) injury
(n = 7) or sham operation (n = 6). Furthermore, adult rats randomized into three groups of post-TBI survival times (2, 24, 72 h) received controlled cortical impact injury (CCI, n = 8) or sham operation (n = 8). Brains were frozen, sagittally cut and incubated with the α7-specific radioligand [125I]a-bungarotoxin for autoradiography. In injured newborn piglets, decreased α7 receptor densities were observed in the hippocampus (-38%), the hippocampus CA1 (-40%), thalamus (-30%) and colliculus superior (-30%). In adult rats, CCI decreased the receptor densities (between -16 and -47%) in almost any brain region within 2 and 24 h. In conclusion, widespread and significantly lowered α7 nAChR densities were demonstrated in
both TBI models. Our results suggest that a nearly similar TBI-induced decrease in the α7 density in the brain of immature and adult animals is found, even with the differences in species, age and experimental procedures. The alterations make the α7 nAChR a suitable target for drug development and neuroimaging after TBI.
Keywords: Traumatic brain injury; α7 nAChR; Autoradiography; Cholinergic system; α-Bungarotoxin

Publ.-Id: 14700 - Permalink


Texture development, microstructure and phase transformation characteristics of sputtered Ni-Ti Shape Memory Alloy films on TiN<111>
Martins, R. M. S.; Schell, N.; Reuther, H.; Pereira, L.; Mahesh, K. K.; Silva, R. J. C.; Fernandes, F. M. B.;
Near equiatomic Ni–Ti films have been deposited by magnetron co-sputtering on TiN films with a topmost layer formed by b111N oriented grains (TiN/SiO2/Si(100) substrate) in a chamber installed at a synchrotron radiation beamline. In-situ X-ray diffraction during Ni–Ti film growth and their complementary ex-situ characterization by Auger electron spectroscopy, scanning electron microscopy and electrical resistivity measurements during temperature cycling have allowed us to establish a relationship between the structure and processing parameters. A preferential development of b110N oriented grains of the B2 phase since the beginning of the deposition has been observed (without and with the application of a substrate bias voltage of −45 and −90 V). The biaxial stress state is considerably influenced by the energy of the bombarding ions, which is dependent on the substrate bias voltage value applied during the growth of the Ni–Ti film. Furthermore, the present work reveals that the control of the energy of the bombarding ions is a promising tool to vary the transformation characteristics of Ni–Ti films, as shown by electrical resistivity measurements during temperature cycling. The in-situ study of the structural evolution of the growing Ni–Ti film as a consequence of changing the Ti:Ni ratio during deposition (on a TiNb111N layer) has also been performed. The preferential growth of b110N oriented grains of the Ni–Ti B2 phase has been as well observed despite the precipitation of Ti2Ni during the deposition of a Ti-rich Ni–Ti film fraction. Functionally graded Ni–Ti films should lead to an intrinsic “twoway” shape memory effect which is a plus for the miniaturization of Ni–Ti films based devices in the field of micro-electro-mechanical systems.

Publ.-Id: 14699 - Permalink


Enantioselective σ1 receptor binding and biotransformation of the spirocyclic PET tracer 1’-Benzyl-3-(3-fluoropropyl)-3H-spiro[[2]benzofuran-1,4’-piperidine]
Wiese, C.; Große Maestrup, E.; Schepmann, D.; Grimme, S.; Humpf, H.-U.; Brust, P.; Wünsch, B.;
It was shown that racemic (±)-2 [1’-benzyl-3-(3-fluoropropyl)-3H-spiro[[2]benzofuran-1,4’-piperidine], WMS-1813] represents a promising positron emission tomography (PET) tracer for the investigation of centrally located σ1 receptors. To study the pharmacological activity of the enantiomers of 2, a preparative HPLC separation of (R)-2 and (S)-2 was performed. The absolute configuration of the enantiomers was determined by CD-spectroscopy together with theoretical calculations of the CD-spectrum of a model compound. In receptor binding studies with the radioligand [3H]-(+)-pentazocine, (S)-2 was thrice more potent than its (R)-configured enantiomer (R)-2. The metabolic degradation of the more potent (S)-enantiomer was considerably slower than the metabolism of (R)-2. The structures of the main metabolites of both enantiomers were elucidated by determination of the exact mass using an Orbitrap-LC-MS system. These experiments showed a stereoselective biotransformation of the enantiomers of 2.
Keywords: σ1 receptor ligands; PET tracer; resolution; CD spectroscopy; enantioselective receptor binding; enantioselective metabolism

Publ.-Id: 14698 - Permalink


Hyperon production in Ar + KCl collisions at 1.76A GeV
Agakishiev, G.; Balanda, A.; Bannier, B.; Bassini, R.; Belver, D.; Belyaev, A.; Blanco, A.; Böhmer, M.; Boyard, J. L.; Cabanelas, P.; Castro, E.; Chernenko, S.; Christ, T.; Destefanis, M.; Diaz, J.; Dohrmann, F.; Dybczak, A.; Eberl, T.; Epple, E.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Fonte, P.; Friese, J.; Froehlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhaeuser, R.; Gil, A.; Gilardi, C.; Golubeva, M.; Gonzalez-Diaz, D.; Guber, F.; Gumberidze, M.; Heilmann, M.; Heinz, T.; Hennino, T.; Holzmann, R.; Huck, P.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kaempfer, B.; Kanaki, K.; Karavicheva, T.; Kirschner, D.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kotte, R.; Krizek, F.; Kruecken, R.; Kuehn, W.; Kugler, A.; Kurepin, A.; Lang, S.; Lange, J. S.; Lapidus, K.; Liu, T.; Lopes, L.; Lorenz, M.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michalska, B.; Michel, J.; Mishra, D.; Moriniere, E.; Mousa, J.; Muentz, C.; Naumann, L.; Otwinowski, J.; Pachmayer, Y. C.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Perez-Cavalcanti, T.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Roy-Stephan, M.; Rustamov, A.; Sadovsky, A.; Sailer, B.; Salabura, P.; Schmah, A.; Schwab, E.; Siebenson, J.; Sobolev, Y. G.; Spataro, S.; Spruck, B.; Stroebele, H.; Stroth, J.; Sturm, C.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Wagner, V.; Weber, M.; Wendisch, C.; Wisniowski, M.; Wojcik, T.; Wuestenfeld, J.; Yurevich, S.; Zanevsky, Y.; Zhou, P.; Zumbruch, P.;
We present transverse momentum spectra, rapidity distribution and multiplicity of Lambda-hyperons measured with the HADES spectrometer in the reaction Ar(1.76A GeV)+KCl. The yield of Xi- is calculated from our previously reported Xi-/(Lambda+Sigma0) ratio and compared to other strange particle multiplicities. Employing a strangeness balance equation the multiplicities of the yet unmeasured charged Sigma hyperons can be estimated. Finally a statistical hadronization model is used to fit the yields of pi-, K+, K0s, K-, phi, Lambda and Xi-. The resulting chemical freeze-out temperature of T=(76+-2) MeV is compared to the measured slope parameters obtained from fits to the transverse mass distributions of the particles.

Publ.-Id: 14696 - Permalink


Energetics and kinetics of defects, impurities, nanostructures and interfaces
Posselt, M.;
Computer simulations using classical interatomic potentials are an efficient and promising tool to investigate and understand atomic-level properties and processes in advanced materials. They allow the consideration of length and time scales which are often hardly accessible by experiments. However, the accuracy of the interatomic potentials employed in such type of simulations determines decisively the quality of the obtained results. Therefore, these potentials must be continuously improved and evaluated.
In the present contribution three applications of atomistic computer simulations are illustrated. The focus is on energetics and kinetics of defects, impurities, nanostructures and interfaces in materials for micro- and nanoelectronics and in structural materials for fission reactors. Implications of the simulation results for the explanation of experimental findings are discussed.

The first example deals with molecular dynamics simulations on basic migration mechanisms of mono- and di-(self-)interstitials in Si. Both the atomic mobility due to the presence of the defect and the defect mobility itself are determined. The mechanism of di-interstitial migration depends on temperature, in contrast to that of the mono-interstitial.

In the second example amorphous Si and Ge as well as their solid-phase epitaxial recrystallization (SPER) are considered. Results obtained by different interatomic potentials are compared. The molecular dynamics simulations yield amorphous material with realistic structural and thermodynamic properties, but the SPER rate is strongly overestimated. It is shown that a more realistic SPER rate can be obtained using a modified interatomic potential which yields a higher melting temperature of the amorphous phase. This is explained by the fact that both melting and SPER are essentially determined by the flexibility of atomic bonds.

The subject of the third example is the formation of coherent Cu-rich precipitates in bcc-Fe, i.e. nanostructures containing Cu and vacancies. For pure vacancy and pure Cu clusters as well as for mixed clusters up to a maximum size of 200 the free binding energy and nucleation free energy are determined, using a combination of on-lattice Metropolis Monte Carlo simulations and off-lattice molecular dynamics calculations. The data which are obtained for the binding energy of a single Cu atom and a single vacancy to a cluster are important input parameters of the rate theory. This type of simulation is an efficient multi-scale modeling tool to simulate the cluster evolution on realistic length and time scales.
Keywords: energetics and kinetics, defects, impurities, nanostructures, computer simulation, classical interatomic potential
  • Invited lecture (Conferences)
    11th IUMRS International Conference in Asia, Symposium T: Multi-scale Modeling and Simulation of Materials, 25.-28.09.2010, Qingdao, China

Publ.-Id: 14695 - Permalink


Nucleation of Cu-vacancy and Ni-vacancy clusters in bcc-Fe
Al-Motasem, A. T.; Posselt, M.; Bergner, F.;
Experimental investigations revealed that both the impurity Cu and the alloying element Ni may contribute to hardening and embrittlement of reactor pressure vessel (RPV) steels during the irradiation by fast neutrons. The irradiation-induced supersaturation of vacancies and self-interstitials amplifies the diffusion of the foreign atoms in bcc-Fe and causes the formation of nanosized Cu- or Ni-rich clusters which act as obstacles to dislocation motion within the grains of the polycrystalline matrix. The concentration of Cu in RPV steels is typically higher than its solid solubility and, therefore, irradiation-enhanced formation of Cu-rich precipitates is observed. Measurements showed that these clusters may not only consist of pure Cu but also include vacancies [1]. On the other hand, the Ni concentration is typically below its solubility limit. That means, any formation of Ni-rich clusters as found in [2] for neutron-irradiated binary Fe-Ni alloys is essentially irradiation-induced. Obviously, these clusters must contain additional species in order to be stable. Small-angle neutron scattering analysis [2] indicated that vacancies could be the other constituent.
In the present work atomistic computer simulations using the ternary Fe-Cu-Ni interatomic potential by Bonny et al. [3] are employed to investigate the thermodynamics of Cu-vacancy and Ni-vacancy precipitates in bcc-Fe. The nucleation free energy of the clusters is determined by the energy and the entropy change due to precipitation using isolated (diluted) Cu and Ni atoms as well as vacancies as the reference. In agreement with indications from measurements the nanoclusters are assumed to have the bcc structure of the iron matrix. The binding energy of the most stable cluster configurations is calculated by simulated annealing within the framework of on-lattice Metropolis Monte Carlo simulations and by subsequent relaxation using off-lattice molecular dynamics calculations.
[1] Q. Xu, T. Yoshiie, K. Sato, Phys. Rev, B 73 (2006) 134115.
[2] F. Bergner, A. Ulbricht, M. Hernandez-Mayoral, P. K. Pranzas, J. Nucl. Mater. 374 (2008) 334.
[3] G. Bonny, R. C. Pasianot, N. Castin, L. Malerba, Phil. Mag. 89 (2009) 3531.
Keywords: atomic simulation, cu-v clusters, formation energy, binding energy
  • Lecture (Conference)
    the 10th International Conference on Computer Simulation of Radiation Effects in Solids, 19.-23.07.2010, Krakow, Poland

Publ.-Id: 14694 - Permalink


Thermodynamics of nanoclusters in bcc-Fe containing copper, nickel and vacancies
Al-Motasem, A. T.; Posselt, M.; Talati, M.; Bergner, F.;
Reactor pressure vessel (RPV) steels consist of polycrystalline bcc-Fe with different alloying elements, e.g. Ni, and different impurities, e.g. Cu. The continuous irradiation by fast neutrons leads to a supersaturation of vacancies and self-interstitials which enhances the diffusion of the foreign atoms and causes the formation of nanosized clusters. The interaction of dislocations with these precipitates is considered to be the main cause of hardening and embrittlement of RPV steels. In order to model the evolution of the nanoclusters under irradiation at typical temperatures by rate theory the dependence of their nucleation free energy on cluster size and composition must be known. In the present work atomic-level computer simulations are employed to determine these data since they are hardly obtainable by experimental investigations. The ternary Fe-Cu-Ni interatomic potential by Bonny et al. [1] is used in order to consider the thermodynamics of nanoclusters which may consist of the two foreign species and vacancies. In particular the influence of Ni on the formation of clusters containing Cu and vacancies is investigated since previous theoretical [1] and experimental [2,3] studies indicated synergistic effects. The nucleation free energy of the clusters is determined by the energy and the entropy change due to precipitation using isolated (diluted) Cu and Ni atoms as well as vacancies as the reference. In agreement with experimental observations the nanoclusters are assumed to have the bcc structure of the iron matrix. The energy and entropy contributions are calculated using combinations of on-lattice Monte Carlo simulations and off-lattice molecular dynamics calculations.
[1] G. Bonny et al., Phil. Mag. 89 (2009) 3531.
[2] J. T. Buswell et al., Effects of Radiation on Materials: 14th Int. Symp. (Vol. II), ASTM STP 1046, Philadelphia, 1990, p.127.
[3] F. Bergner et al., J. Nucl. Mater. (2009) in press
Keywords: atomistic modeling, v-Cu-Ni cluster, thermodynamic stability, monomer binding energy.
  • Lecture (Conference)
    The fifth International Conference on Multiscale Materials Modeling (MMM-2010), 04.-08.10.2010, Frieburg, Germany, 04.-08.10.2010, Freiburg, Germany
  • Contribution to proceedings
    The fifth international conference on Multiscale Materials Modeling , Freiburg-Germany, 04.-08.10.2010, Freiburg, Germany
    MMM2010 Multiscale Materials Modeling, 978-3-8396-0166-2

Publ.-Id: 14693 - Permalink


3D-Visualisierung von Fluidströmungen in Salinargestein mittels Positronen-Emissions-Tomographie
Wolf, M.; Kulenkampff, J.; Enzmann, F.; Lippmann-Pipke, J.; Gründig, M.; Richter, M.;
Der ehemalige Kali- und Steinsalzbergbau im Raum Staßfurt (Sachsen-Anhalt) führt seit dem 19. Jahrhundert zu stellenweise erheblichen Bergschäden im Stadtgebiet, die auf Subrosion und Konvergenz untertägiger Hohlräume zurück gehen. Gebäude und Infrastruktur sind von großflächigen Absenkungen, Vernässungen und lokalen Tagesbrüchen in Mitleidenschaft gezogen worden.

Da man ähnliche Bergbaufolgeschäden in vielen Regionen des Salzbergbaus antrifft, hat sich das aus mehreren Forschungseinrichtungen, Universitäten und Unternehmen bestehende Forschungsverbundvorhaben Dynamik abgesoffener oder gefluteter Salzbergwerke und ihres Deckgebirgsstockwerks unter Federführung der Bundesanstalt für Geowissenschaften und Rohstoffe (BGR) zum Ziel gesetzt, Ursachen, Prozesse und Auswirkungen der Bergschäden exemplarisch und allumfassend zu untersuchen.

Um ein möglichst umfassendes Bild der im Untergrund ablaufenden Prozesse und deren Ursachen und Folgen zu erhalten, sind Untersuchung der kleinräumigen Strukturen und Prozesse im Labormaßstab erforderlich. Die großräumige Abschätzung der Grundwasserdynamik im Salinar und im Deckgebirge, also der Ursachen und Folgen der Subrosion, bedarf der Charakterisierung von Wegsamkeiten und der Fluiddynamik bis in den Milli- und Mikrometerbereich, da sich die grundlegenden Prozesse auf der molekularen Ebene in der Mikroskala abspielen und somit die Dynamik in der regionalen Größenordnung bestimmen.

Wie auf der Feldskala, so wird auch auf der Laborskala die Verteilung von hydrologischen Parametern, wie z.B. Permeabilitäten, Abstandsgeschwindigkeiten und Dispersionsraten von der heterogenen Struktur des Gesteins kontrolliert, weswegen diese Parameter nicht nur im regionalen sondern auch im Labormaßstab strukturbezogen, also räumlich differenziert, erhoben werden sollten.

Daher wurde in enger Zusammenarbeit mit dem Geologischen Institut der JGU Mainz eine Methode zur direkten räumlich aufgelösten und quantitativen Prozessbeobachtung entwickelt und angewendet. Hierfür wurde die Methode der Positronen-Emissions-Tomographie (PET) eingesetzt, ein ursprünglich medizinisches, bildgebendes Verfahren. Dieses Verfahren erlaubt es, zerstörungsfrei, mit höchstmöglicher Empfindlichkeit und geeignetem Auflösungsvermögen, die Bewegung einer mit einem radioaktiven Tracerisotop (hier F-18 und I-124) markierten Wassermenge in Raum und Zeit zu beobachten, wobei die Menge des eingesetzten Radiotracers im Bereich weniger Nanogramm gehalten werden kann. Das System wird somit durch den Tracer auf geringst mögliche Weise beeinflusst und es wird ein sehr realistisches Bild des Fließverhaltens mit einer räumlichen Auflösung von 1 mm und einer zeitlichen Auflösung von 60 s erzeugt.

Bislang wird in der Literatur nur von wenigen Ansätzen berichtet, die das Ziel verfolgen, die realistischen Verhältnisse strömender Fluide in heterogen strukturierten Gesteinen dreidimensional abzubilden. Solche Strömungsmuster werden in der Regel mittels stochastischer Modelle durch Computersimulationen erzeugt. Erst ein Abgleich mit gemessenen Strömungsmustern kann zur Validierung dieser Simulationen führen, was auch erst ein valides Upscaling in die Feldskala ermöglicht.

In Kooperation mit der Bundesanstalt für Materialforschung- und prüfung Berlin (BAM) und dem Geologischen Institut der Johannes-Gutenberg Universität Mainz (JGU) werden daher die PET-Messungen zur Fluiddynamik mit Lattice-Boltzmann-Simulationen der Fließprozesse verglichen, die auf hochauflösenden computertomographischen µXCT Messungen der internen Struktur der identischen Bohrkerne beruhen.

Der Vergleich von PET-Messdaten mit Lattice-Boltzmann - Simulationsdaten bedeutet eine Skalenübertragung um etwa drei Größenordnungen (µm - mm). Daher erfolgt der Abgleich zwischen gemessenen und simulierten Daten auf statistischem Wege. Gemessene und simulierte Strömungsmuster werden mittels Variographie mit einander abgeglichen, da diese Methode skalenübergreifend die Korrelationen zwischen den Fließmustern wider gibt. Ebenso werden räumlich differenzierte Durchbruchkurven und Histogramme für den Vergleich von Messung und Simulation heran gezogen.

Diesem Ansatz liegt das Bestreben zugrunde, zu einer Erweiterung des generellen Prozessverständnisses und der Vorhersagbarkeit über das Verhalten von Fluiden in porösen und klüftigen Gesteinen beizutragen und die beobachteten Phänomene und Prozesse von der Labor- auf die Feldskala zu übertragen.

Nicht in jedem Fall war dieser Abgleich zwischen Simulation und Experiment jedoch möglich: während in klüftig-porösen Materialien gewöhnlich mit beiden Methoden räumlich stark differenzierte präferentielle Fließwege im Kluftsystem gefunden wurden, konnte in eher mikrostrukturell ausgeprägten Materialien trotz messbarer Permeabilität gelegentlich kein verbundener Porenraum aus den CT-Bildern segmentiert und somit keine Lattice-Boltzmann-Simulation durchgeführt werden. In diesem Fall zeigte die PET-Untersuchung ein diffuses Ausbreitungsverhalten des Tracers.
  • Lecture (Conference)
    Staßfurt-Verbund Abschlusstagung 2010, 18.-20.11.2010, Staßfurt, Sachsen-Anhalt

Publ.-Id: 14692 - Permalink


Fluid flow in geological material: GeoPET observation in comparison with Lattice-Boltzmann simulation
Wolf, M.; Kulenkampff, J.; Lippmann-Pipke, J.; Gründig, M.; Richter, M.; Enzmann, F.;
This thesis is located at the Institute of Radiochemistry, FZD Research Site Leipzig for Interdisciplinary Isotope Research, Reactive Transport Division (FWRT). The main focus of this division is the investigation of transport processes in geosystems by means of radiotracer applications. The main topic of the thesis is the visualization of transport processes in geologic material by means of the in-house development of the GeoPET-method. This work is conducted as part of the scientific joint venture: „Dynamik abgesoffener oder gefluteter Salzbergwerke und ihres Deckgebirgsstockwerks“ („Dynamic of drowned or flooded salt mines and their overburden“), coordinated by the Bundesanstalt für Geowissenschaften und Rohstoffe (BGR).

Since the late 19. century drowned salt mines cause severe mining damages in the city of Stassfurt (Saxony-Anhalt). Sink hole depressions and subsidence of the surface below the groundwater table destroyed large parts of the down town. The general causation was lack of experience with salt mines and mining in gypsum karst in the 19. century. The causation in detail why and how exactly salt rock has washed out is more complicated to identify, as streaming mechanisms at the small scale level are partly still unclear; the general fluid dynamics at small scales is partly unknown.

To reveal these processes and mechanisms the behaviour of salt brines at the millimetre scale in drilling cores of the different geological units of the salt rock and its surrounding is examined by three-dimensional visualization of the distribution of radioactive labelled water measured with PET. Mechanisms at millimetre scale control mechanisms at the kilometre scale and are of utmost importance for the principal understanding of fluid dynamics. In the laboratory you can have „a look into the rock“. In the field this is not possible this way.

Combining PET data with high resolution CT-scans of the samples (conducted by the cooperation partners JGU Mainz and BAM Berlin) allows an alignment of processes of the fluid flow and its associated hydraulic pathway structures. This matching is important for understanding and for generalized conclusion about ongoing processes and is a necessary preparatory work for computer modelling.

Lattice-Boltzmann-simulations of velocity fields and streaming patterns based on CT-data are compared with PET-data derived from the same samples. This comparison of the flow patterns is done by means of geostatistic methods that allows scale independant spatial correlation of the patterns and therefore provide scale indpendant parameters like correlation lengths that are a necessity for upscaling.

Short term objective is the improvement and validation of parameters and fluid flow concepts derived from small scale simulations. Long term objective is the improvement of upscaling of parameters and concepts to the field scale and a better understanding and prediction of mining damages and groundwater behaviour.
  • Lecture (Conference)
    Bodenphysik-Seminar, 14.10.2010, Halle, Sachsen-Anhalt

Publ.-Id: 14691 - Permalink


Does the coordination geometry of CuII bispidine complexes influence the radiopharmacological properties?
Fähnemann, S.; Stephan, H.; Walther, M.; Steinbach, J.; Haaf, C.; Comba, P.;
3,7-Diazabicyclo[3.3.1]nonane derivatives (bispidines) represent a versatile platform for the development of new copper radiopharmaceuticals.[1] An extensive research effort has shown that bispidines with additional donor substituents form very stable complexes with copper(II) (L1, logK = 16.3). The CuII complexes of these so-called 1st generation hexadentate bispidine ligands (L1-Cu) enforce a distorted octahedral geometry which is well preorganized for CuII.

Recently, the 2nd generation of bispidine derivatives has been reported (L2 – L3).[2, 3] These ligands yield very high complex stabilities with CuII (logK from 19.5 to 26.4) similar to [CuII(cyclam)]2+ (logK = 27.2). In contrast to the 1st generation bispidines they provide exclusively aliphatic nitrogen atoms in the backbone, combined with one (L2) or two (L3) rigid diazacycloheptane rings for tetra- or hexadentate coordination, leading to distorted trigonal bipyramidal or distorted trigonal prismatic coordination geometries.

Ligands L1 – L3 have been labeled with 64Cu, and their radiopharmacological data, e.g. labeling efficiency and kinetics, lipophilicity and in vitro stability will be discussed.

Literature:
[1] S. Juran, M. Walther, H. Stephan, R. Bergmann, L. Steinbach, W. Kraus, F. Emmerling, P.Comba; Bioconjugate Chem. 2009, 20, 347-59.
[2] P. Comba, C. Haaf, H. Wadephol; Inorg. Chem. 2009, 48, 6604-6614.
[3] P. Comba, C. Haaf, A. Lienke, A. Muruganantham, H. Wadepohl: Chem.-Eur. J., 2009, 41, 10880-10887.
  • Poster
    3rd EuCheMS Chemistry Congress, 29.08.-02.09.2010, Nürnberg, D

Publ.-Id: 14690 - Permalink


Octahedral rhenium cluster/glycodendrimer associates: A new tailor-made drug delivery system?
Kubeil, M.;
In recent years polynuclear metal complexes have become increasingly important due to their antitumoral as well as antiviral properties. [1] Their wide variety of biochemical, chemical and physical properties gives the opportunity to create tailor-made drugs. In this perspective, the enhancement of the hydrolytic stability and in particular the improvement of the in vivo selectivity of inorganic cluster compounds represents the major burden to circumvent.

Appropriate nanocontainers may be utilized to enable the cluster compounds to be transported and released within target tissues. Of great interest is the encapsulation of potential drug molecules by non-covalent binding at the interior of dendritic structures which provide well-defined cavities. In this context, dendritic nanocontainer with maltose-modified shell [2] appears appealing to act as a host for nanometer sized anionic rhenium cluster compounds.

The inclusion and release phenomena of an octahedral rhenium cluster with six terminal hydroxo ligands [Re6S8(OH)6]4- [3] into poly(propylene amine) dendrimers (POPAM, generation 4 and 5) with dense maltose shell have been studied in detail applying different physico-chemical methods, e.g. UV/vis, time-resolved laser-induced fluorescence spectroscopy (TRLFS) and laser induced liquid bead ion desorption (LILBID) mass spectrometry.

On average, 4 – 5 cluster anions can be captured in the interior of the investigated sugar-coated dendrimers, and a slow release of cluster complexes was observed under physiological conditions.

Altogether, the studied system shows the possibility for the development of dendritic nanocarriers with specific targeting and paves the way for therapeutic applications.



[1] J. T. Rhule, C. L. Hill, D. A. Judd, R. F. Schinazi, Chem. Rev.1998, 98, 327-357.
[2] B. Klajnert, D. Appelhans, H. Komber, N. Morgner, S. Schwarz, S. Richter, B. Brutschy, M. Ionov, A. K. Tonkikh, M. Bryszewska, B. Voit, Chem. Eur. J. 2008, 14, 7030.
[3] K. A. Brylev, Y. V. Mironov, S. S. Yarovoi, N. G. Naumov, V. E. Fedorov, S.-J. Kim, N. Kitamura, Y. Kuwahara, K. Yamada, S. Ishizaka, Y. Sasaki, Inorg. Chem. 2007, 46, 7414-7422.
  • Lecture (Conference)
    IWTMC-II International Workshop on Transition Metal Clusters-II, 30.09.-02.10.2010, Rostock, D

Publ.-Id: 14689 - Permalink


Improved environmental resistance of Ti-alloys at elevated temperatures by a combined Al- and F-treatment
Donchev, A.; Schütze, M.; Kolitsch, A.; Yankov, R.;
Titanium is widely used as a structural material because of its low specific weight, good mechanical properties and excellent corrosion resistance at low temperatures due to the formation of a passive TiO2layer. The melting point (1677°C) is very high. Usually the maximum tolerable operating temperature is lower than 600°C. Because of increased oxidation and environmental embrittlement Ti-Alloys can not be used at higher temperatures in oxidizing environments. An enrichment of Al in the surface zone of Ti-alloys leads to an improvement of the oxidation resistance by the formation of intermetallic TixAly-phases but this is not sufficient. A fluorine treatment on TiAl-alloys results in the formation of a protective alumina scale by the so called fluorine effect. Therefore, the combination of Al-enrichment in the surface zone so that a TiAl-layer is formed and an additional F-treatment gives good results. The alumina scale is very protective against environmental attack and also prevents oxygen inward diffusion which causes embrittlement. In this paper the results of isothermal and thermocyclic oxidation tests at 600°C of several Ti-alloys (-Ti, Ti3Al, etc.) are presented without any treatment, with single Al-treatment, pure F-treatment and the combination of both. Aluminium was either enriched by a powder pack process or by magnetron sputtering. Fluorine was applied by several ways e.g. by a liquid phase process. Post experimental investigations like SEM revealed the formation of thin oxide layers on samples with the combined Al + F-treatment. Hardness measurements showed that no embrittlement was observed on the treated samples while untreated specimens showed increased hardness values in the oxygen enriched zone.
  • Lecture (Conference)
    Materials Science & Technology 2010 Conference and Exhibition - combined with the ACerS 112th Annual Meeting (MS&T 2010), 17.-21.10.2010, Houston, USA

Publ.-Id: 14688 - Permalink


Protection of TiAl-components against high temperature oxidation with fluorine
Donchev, A.; Schütze, M.; Kolitsch, A.; Yankov, R.;
Titanium aluminides are very promising light weight materials for several high temperature applications e.g. in aero or automotive engines but due to their insufficient oxidation resistance at temperatures above roughly 800°C they can not be used for longer times. The oxidation behaviour of TiAl-alloys can be improved significantly by microalloying of small amounts of fluorine into the subsurface zone. The use of TiAl-components after fluorine treatment is possible up to temperatures above 1000°C in oxidizing atmospheres due to the formation of a thin protective alumina layer. One possibility to apply fluorine to the surface of complex TiAl-components is the PI³-technique (plasma immersion ion implantation). The use of an Ar/CH2F2-plasma for the F-PI³ into small coupons leads to a positive effect which is as good as the beamline implantation of elemental fluorine gas into samples of the same size. Other treatments are using liquid or gaseous fluorine containing compounds which react with the surface of the specimens. The oxidation kinetics of F-treated TiAl-alloys will be discussed in the paper. Several more complex TiAl-samples and turbine blades as examples for real TiAl-components have been treated. Their oxidation behaviour will be shown. Post exposure investigations like SEM reveal a thin protective alumina scale on the surface of the implanted samples in contrast to a thick mixed scale (TiN/TiO2/Al2O3) growing on untreated samples during high temperature exposure in air.
  • Lecture (Conference)
    Materials Science & Technology 2010 Conference and Exhibition - combined with the ACerS 112th Annual Meeting (MS&T 2010), 17.-21.10.2010, Houston, USA

Publ.-Id: 14687 - Permalink


Suppression of oxygen-induced embrittlement in Ti by plasma immersion ion implantation (PIII)-based processing
Yankov, R. A.; Kolitsch, A.; Munnik, F.; von Borany, J.;
Titanium has a large strength-to-weight ratio and good corrosion resistance at moderate temperatures, which make it an important structural material in a number of advanced technical applications. A major problem with the use of Ti is its high affinity to oxygen giving rise to massive oxygen in-diffusion at temperatures of about 550° to 600°C. The presence of large amounts of oxygen renders the material brittle and deteriorates its mechanical properties. In this work, we describe an effective way of overcoming the oxygen-induced embrittlement problem by forming a surface barrier to the diffusion of oxygen. Surface processing has involved two steps, namely enrichment of the Ti near-surface region with Al, and introduction of fluorine. For the Al enrichment, a novel hybrid system has been developed to implant Al into Ti. The apparatus consists basically of a PIII chamber configured with two magnetrons having an Al target each, and facing the RF antenna. The magnetrons are synchronized with the bias applied to the sample holder in such a way that the accelerating high-voltage pulse is triggered with a certain delay, i.e. during the time when the Al plasma generated by the magnetrons is most dense, thereby minimizing deposition. Alternative aluminization techniques have involved either magnetron sputtering of Al onto Ti followed by a thermal drive-in step or pack processes. Fluorine has been subsequently introduced by PIII employing a mixture of CH2F2 and Ar as the precursor gas. A variety of analytical techniques such as elastic recoil detection analysis (ERDA), Rutherford backscattering spectrometry (RBS), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX) and x-ray diffraction (XRD) have been used for characterization. Optimized PIII-based processing has been found to produce a continuous, adherent alumina scale on the Ti surface. Thus, the resulting material is inherently resistant to oxygen absorption and is not embritteled upon extended exposure to oxygen-containing environments at elevated temperatures up to about 600° C.
  • Poster
    12th International Conference on Plasma Surface Engineering - PSE 2010, 13.-17.09.2010, Garmisch-Partenkirchen, Germany

Publ.-Id: 14686 - Permalink


Improvement of the oxidation behaviour of complex shaped TiAl-alloys by plasma immersion ion implantation with fluorine
Kolitsch, A.; Yankov, R.; Donchev, A.;
Titanium aluminides are of great interest for several structural high temperature applications because of their low specific weight (about 4 g/cm3) and their excellent high temperature strength. They could replace the much heavier high temperature steels or Ni-based superalloys (up to 9 g/cm3) which are usually in service. The implementation of this new group of intermetallic alloys in e.g. the aerospace or automotive industry is therefore due to economic and ecologic reasons. The use of TiAl-based alloys is still limited to a temperature of about 750 °C because of their poor oxidation resistance despite of their good mechanical properties which would allow the use at higher temperatures. The oxidation resistance can be improved significantly by small amounts of halogens such as fluorine, chlorine, bromine and iodine (so called halogen effect).
A defined dose of these halogens has to be provided at the metal/oxide interface of the component. The halogens promote the selective formation of gaseous Al-halides at temperatures above 700 °C which are oxidised to Al2O3 during their outward diffusion through the naturally grown oxide scale. So finally a protective alumina scale is formed which is stable for long times even under thermocyclic exposure and wet atmospheres. In this presentation the results of isothermal and thermocyclic high temperature oxidation tests of technical TiAl-alloys with and without fluorine ion implantation are shown.
  • Poster
    18th International Conference on Ion Implantation Technology, 06.-11.06.2010, Kyoto, Japan

Publ.-Id: 14685 - Permalink


Formation of an alumina-containing scale for the surface protection of TiAl alloys and Ti against environmental degradation at elevated temperatures
Yankov, R. A.; Kolitsch, A.; Munnik, F.; von Borany, J.;
Ti and TiAl alloys are lightweight materials that hold great promise for advanced aerospace, automotive and power generation applications. They are, however, limited in applicability by their poor oxidation resistance above 600°C. We have developed a process for enhancing the high-temperature oxidation resistance of these materials. For TiAl, the process involves a single step, i.e. plasma immersion implantation (PIII) of fluorine relying on the so-called "halogen effect". Optimum conditions have been established under which the alloys acquire a stable, adherent and highly protective alumina scale upon subsequent high-temperature oxidation in air. The extent of oxidation protection has been evaluated by testing F-implanted TiAl samples at temperatures up to 1050°C. Results from characterization by elastic recoil detection, X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray analysis have proven the possibility of forming a protective alumina scale on both laboratory coupons and components such as turbine blades and turbochargers. In the case of Ti, surface processing involves two steps, i.e. Al enrichment of the Ti near-surface, and introduction of F by PIII. The Ti samples so modified have shown marked environmental stability at temperatures up to 700°C.
  • Poster
    CIMTEC 2010 - 12th International Conference on Modern Materials and Technologies, 12th International Ceramic Congress, 06.-11.06.2010, Montecatini Terme, Italy

Publ.-Id: 14684 - Permalink


Enhanced resistance of Ti-alloys against environmental attack by a combined Al- and F-treatment
Donchev, A.; Schütze, M.; Kolitsch, A.; Yankov, R.;
Titanium alloys cannot be used at elevated temperatures above approximately 500°C because of their limited environmental stability. Several ways have been investigated so far to improve the environmental stability of Ti-alloys e.g. coatings but these attempts in a majority of cases have not been really successful. A new way to improve the performance of these alloys is the combination of Al-enrichment in the surface zone plus additional fluorine treatment. The Al-enrichment leads to the formation of intermetallic phases. These phases improve the oxidation resistance of Ti-alloys but not to a sufficient extent. An additional fluorine treatment on top of the Al-enriched surface leads to the formation of a stable alumina scale due to the fluorine effect. In this paper results from oxidation and other tests performed on Ti-samples without any treatment, with single Al- or F-treatment and with a combination of both are presented and the results are discussed.
  • Lecture (Conference)
    TMS 2010 (The Minerals, Metals and Materials Society), 139th Annual Meeting & Exhibition, 14.-18.02.2010, Seattle, USA

Publ.-Id: 14683 - Permalink


Comparison of fluorination treatments to improve the high temperature oxidation resistance of TiAl alloys in SO2 containing environments
Masset, P. J.; Yankov, R.; Kolitsch, A.; Schütze, M.;
Surfaces of titanium aluminides were treated with fluorine either physically by plasma immersion ion implantation (PIII) or chemically using a F-based polymer. Under optimum conditions of fluorination, both treatments were shown to improve the oxidation resistance of the alloys even in aggressive environments containing sulfur dioxide (0.1 vol. %). No sulfur was detected in the oxide scale although thermodynamic calculations predict the formation of sulfides. The inward diffusion of oxygen and nitrogen was found to be reduced in the presence of SiO2.

Publ.-Id: 14682 - Permalink


Surface Morphology of Heterogeneous Nanocrystalline Rutile/Amorphous Anatase TiO2 Films Grown by Reactive Pulsed Magnetron Sputtering
Gago, R.; Vinnichenko, M.; Redondo-Cubero, A.; Czigany, Z.; Vazquez, L.;
Titaniumdioxide filmswere grown on unheated substrates bymid-frequency (100 kHz) reactive pulsed magnetron sputtering at different O2 partial pressures in an Ar/O2 atmosphere. X-ray diffraction and absorption measurements reveal a transition from amorphous anatase to nanocrystalline rutile with [O2], with a mixture of both phases at intermediate values. Atomic forcemicroscopy shows that the promotion of rutile is accompanied by surface roughening due to the apparition of hollow structures (holes) on the surface, in contrast with the extremely smooth morphology of amorphous anatase films. The number and size of holes increase with [O2] and growth time in such a way that they eventually coalesce and percolate to lead to a rough surface for those growth conditions for which a rutile rich filmis obtained. Transmission electron microscopy analysis shows the growth evolution of a heterogeneous phase mixture and provides unambiguous correlation between the hole (smooth) morphology and the underlying rutile (anatase) phase. Therefore, the surface morphology results fromthe slower local growth rate of nanocrystalline rutile compared to that of the surrounding amorphous anatase flat regions as well as from the fast (slow) lateral (vertical) growth rate of the rutile domains.
Keywords: Amorphous oxides, TiO2, magnetron, pulsed discharges, thin films

Publ.-Id: 14681 - Permalink


Tumour bed irradiation of human tumour xenografts in a nude rat model using a common X-ray tube
Tokalov, S.; Enghardt, W.; Abolmaali, N.;
Studies that investigate the radiation of human tumour xenografts require an appropriate radiation source and highly standardized conditions during radiation. This work reports on the design of a standardized irradiation device using a commercially available X-ray tube with a custom constructed lead collimator with two circular apertures and an animal bed plate, permitting synchronous irradiation of two animals. Dosimetry and the corresponding methodology for radiotherapy of human non-small cell lung cancer xenograft tumours transplanted to and growing subcutaneously on the right lower limb in a nude rat model were investigated. Procedures and results described herein prove the feasibility of use of the device, which is applicable for any investigation involving irradiation of non-tumorous and tumorous lesions in small animals.

Publ.-Id: 14680 - Permalink


Improvement of radiation-mediated immunosuppression of human NSCLC tumour xenografts in a nude rat model
Tokalov, S.; Enghardt, W.; Abolmaali, N.;
Human tumour xenografts in a nude rat model have consistently been used as an essential part of preclinical studies for anticancer drugs activity in human. Commonly, these animals receive whole body irradiation to assure immunosuppression. But whole body dose delivery might be inhomogeneous and the resulting incomplete bone marrow depletion may modify tumour behaviour. To improve irradiation-mediated immunosuppression of human non-small cell lung cancer (NSCLC) xenografts in a nude rat model irradiation (2 + 2 Gy) from opposite sides of animals has been performed using a conventional X-ray tube. The described modification of whole body irradiation improves growth properties of human NSCLC xenografts in a nude rat model. The design of the whole body irradiation mediated immunosuppression described here for NSCLC xenografts may be useful for research applications involving other types of human tumours.

Publ.-Id: 14679 - Permalink


Advanced bio-composite materials for water treatment
Raff, J.; Pollmann, K.;
Bacteria developed during evolution highly effective mechanisms and structures to survive at the most forbidding, uninviting places on Earth. One example is the binding of metalloids, heavy metals and actinides by cell surface proteins of uranium mining waste pile isolates. The so called surface layer (S-layer) proteins avoid the uptake and any sustainable damage of the cell by toxic and/or radioactive elements. The proteins possess additionally self-assembling properties and form symmetric lattices. These properties altogether qualifies the protein for nano-technological purposes and allow the production of advanced bio-composite materials such as metal filters, (photo)catalysts, functionalized membranes or biosensors for the treatment of water.
Keywords: S-layer, photocatalysts, water treatment
  • Poster
    POLEKO 2010, Internationale Fachausstellung für Umwelt, Energie, Ökologie, 23.-26.11.2010, Posen, Polen

Publ.-Id: 14678 - Permalink


Untersuchungen zur U(VI)-Komplexierung durch Milchsäure sowie zur U(VI)-Sorption an Opalinuston in Abwesenheit und Gegenwart von organischen Modellliganden in Abhängigkeit von der Temperatur
Joseph, C.; Steudtner, R.; Schmeide, K.;
Die U(VI)-Komplexierung durch Milchsäure in Abhängigkeit von der Temperatur (7-65°C) wurde mittels UV/VIS-Spektroskopie und TRLFS untersucht. Dabei konnten zwei U(VI)-Lactat-Komplexe, UO2Lac+ und UO2Lac2, identifiziert werden. Die entsprechende Enthalpie und Entropie der U(VI)-Komplexierung wurde bestimmt.
Die U(VI)-Sorption an Opalinuston (OPA) in Abhängigkeit von Modellliganden und der Temperatur (25-60°C) wurde untersucht. Dabei beeinflussten die Modellliganden die U(VI)-Sorption an OPA in folgender Reihenfolge: Citronensäure > Weinsäure > Milchsäure ≈ Essigsäure > Ameisensäure. Die U(VI)-Sorption nahm mit steigender Ligandenkonzentration ab, nahm aber mit steigender Temperatur zu. Bei 60°C wurde ein Sprung im Kd-Wert des Urans verzeichnet. Milchsäure hatte dabei keinen signifikanten Einfluss auf die Enthalpie und Entropie der U(VI)-Sorption an OPA in Abhängigkeit von der Temperatur.
HTO-Diffusionsversuche mit OPA bei 25°C und 60°C wurden durchgeführt um die Diffusionsparameter (effektiver Diffusionskoeffizient, Porosität) der Tonproben zu bestimmen. Die experimentellen Werte bestätigten die Literaturdaten.
Keywords: uranium(VI), complexation, TRLFS, UV/VIS, lactate, citric acid, sorption, Opalinus Clay, temperature-dependent, diffusion, HTO
  • Lecture (others)
    9. Workshop des Verbundprojekts "Wechselwirkung und Transport von Actiniden im natürlichen Tongestein unter Berücksichtigung von Huminstoffen und Tonorganika", 05.-06.10.2010, Mainz, Deutschland

Publ.-Id: 14677 - Permalink


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