Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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35836 Publications

Feasibility study for MeV electron beam tomography

Hampel, U.; Bärtling, Y.; Hoppe, D.; Kuksanov, N.; Fadeev, S.; Salimov, R.

Electron beam tomography is a promising imaging modality for the study of fast technical processes. But for many technical objects of interest X-rays of several hundreds of keV energy are required to achieve sufficient material penetration. In this article we report on a feasibility study for fast electron beam computed tomography with a 1 MeV electron beam. The experimental setup comprises an electrostatic accelerator with beam optics, transmission target, and a single X-ray detector. We employed an inverse fan-beam tomography approach with radiographic projections being generated from the linearly moving X-ray source. Angular projections were obtained by rotating the object.

Keywords: electron beam tomography; ultrafast tomography

Publ.-Id: 17544

Capacitance wire-mesh sensor applied for the visualization of three-phase gas-liquid-liquid flows

Da Silva, M. J.; Hampel, U.

This short communication describes the application of a capacitance wire-mesh sensor for the investigation of a simulated gas-liquid-liquid three-phase flow in a laboratory setup. Experiments with air, silicone oil and water are performed first in static and second in dynamic conditions. The capacitance mesh sensor is capable of generatinge images of the cross-sectional distribution of relative permittivity values, which in turn is an indication to the phases present in the multiphase mixture. Initial tests show that the sensor is a valuable tool to investigate such three-phase flows, which are very common in the oil industry.

Keywords: wire mesh sensor; three phase flow; multiphase flow; flow measurement

Publ.-Id: 17543

Development of high-rate MRPCs for high resolution time-of-flight systems

Wang, J.; Wang, Y.; Gonzalez-Diaz, D.; Chen, H.; Fan, X.; Li, Y.; Cheng, J.; Kaspar, M.; Kotte, R.; Laso Garcia, A.; Naumann, L.; Stach, D.; Wendisch, C.; Wüstenfeld, J.

We show how the high charged-particle fluxes (1-20 kHz/cm²) expected over the 150 m² large time-of-flight wall of the future Compressed Baryonic Matter experiment (CBM) at FAIR can be realistically handled with Multi-gap Resistive Plate Chambers (MRPCs). This crucial 100-fold increase of the chamber rate capability, as compared to that of standard MRPCs presently employed in experiments resorting to sub-100 ps timing, has been achieved thanks to the development of a new type of low-resistive doped glass. Following the encouraging results previously obtained with small counters, two types of modules (active area: ~150 cm²) have been built at Tsinghua University with the new material. The measurements conveyed in this work, obtained with a quasi-minimum ionizing electron beam, prove their suitability as the building blocks of the present hadron-identification concept of the CBM experiment. Namely, they provide a time resolution better than 80 ps and an efficiency above 90% at particle fluxes of 50 kHz/cm², being at the core of a modular concept that is easily scalable. Recent measurements of the electrical and mechanical properties of this new material, together with its long-term behavior, are shortly summarized.

Publ.-Id: 17542

Production and purification of 56Co at the Leipzig cyclotron

Mansel, A.; Franke, K.

60Co (T1/2 = 5.27 a) is one of the most used radionuclide for sterilization of medical equipment, as a radiation source for medical radiotherapy, industrial radiography and food irradiation due to the high gamma-energy of 1.33 MeV. In case of release in the geosphere, e.g. soil and aquatic systems, the migration behaviour of cobalt is not well understood. For geochemical investigations, e.g. migration and adsorption studies in soil and rock formations, the short-lived isotope 56Co (T1/2 = 77 d) can be used.
We produced 56Co at a recently installed 18 MeV-cyclotron by using the nuclear reaction 56Fe(p,n)56Co.[1] The target was prepared by pressing metallic iron powder into an aluminium plate and cover it with an aluminium foil. After the irradiation with 11 MeV protons for 1 h at a current of 25 µA, the iron was dissolved with a mixture of concentrated HCl and concentrated H2O2.[2] The separation of 56Co from the target material was done by liquid-liquid extraction with methyl-tert-butylether (MTBE) from 5.2 M HCl.[3] Alternatively, an anionic exchange with DOWEX 1x8 as a column material can be used.[4] Due to the shorter separation time the liquid-liquid extraction is preferred. The radiochemical yield was 82% ± 6%. The activity concentration in the 56Co stock solution was ~4.5 MBq / ml.

[1] Jenkins, I. L., Wain, A. G., (1970) J. Inorg. Nucl. Chem. 32(5) 1419-1425.
[2] Lagunas-Solar, M. C., Jungerman, J. A., (1979) Int. J. Appl. Radiat. Isot. 30(1) 25-32.
[3] V. Wiskamp, S. Zenker, (1997), Eisenextraktion mit tertiärem Butylmethylether. CLB 48 (Beilage Memory) 22.
[4] Kraus, K. A., Moore, G. E., (1953) J. Am. Chem. Soc. 75(6) 1460-1462.

  • Lecture (Conference)
    NRC 8 - International Conference on Nuclear and Radiochemistry, 16.-21.09.2012, Como, Italy

Publ.-Id: 17541

Dose-Controlled Radiobiological Experiments with Laser Accelerated Proton Pulses as a Prerequisite for Radiation Therapy

Schramm, U.

  • Invited lecture (Conferences)
    EPS / ICPP - 39th European Physical Society Conference on Plasma Physics / 16th International Congress on Plasma Physics, 02.-06.07.2012, Stockholm, Sweden

Publ.-Id: 17540

Synthesis, Characterization and Evaluation of Radiometal-Containing Peptide Nucleic Acids

Stephan, H.; Förster, C.; Gasser, G.

As described in Chapter, peptide nucleic acids (PNAs) have very attractive properties, which include, among them, high selectivity towards DNA/RNA recognition. It is therefore not surprising that their potential in nuclear medicine and biology to explore in vitro and in vivo processes has also been investigated. The high thermal and radiolytic stability as well as resistance toward nuclease/protease degradation of these bioconjugates offers new opportunities in this field of research, which could, potentially, lead to a transformation of the whole scope of diagnostically and therapeutically relevant radionuclides. Importantly, as demonstrated in Chapter with metal complexes, PNAs can be synthetically modified allowing their intrinsic physico-chemical properties to be significantly modulated. For example, the attachment of appropriate spacer elements and specific building blocks, such as targeting units, to both the C- and N-terminus of PNAs allows a broad variation of the pharmacologic properties of PNA bioconjugates, hence enabling the development of application-orientated probes for imaging of gene expression. Furthermore, the high metabolic resistance of these non-natural oligonucleotides makes them interesting for therapeutic applications. In this book chapter, we report on the current developments towards the preparation of radiometal-containing PNA constructs and summarize the protocols for labeling these oligonucleotides with 99mTc, 111In, 64Cu, 90Y and 177Lu.

Keywords: Peptide Nucleic Acid (PNA); Radiometal Complexes; Bifunctional Chelating Agents; Molecular Imaging; Endoradionuclide Therapy

  • Book chapter
    P. E. Nielsen, D. H. Appella: Peptide Nucleic Acids: Methods and Protocols, 2nd ed., Series: Methods in Molecular Biology, Vol. 1050, New York: Springer, Humana Press, 2014, 978-1627035521, 37-54

Publ.-Id: 17539

Polyoxometalates as versatile enzyme inhibitors

Stephan, H.; Müller, C. E.

Polynuclear metal compounds may have considerable potential as metallic drugs. The most prominent representatives are polyoxometalates (POMs) 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.
Polyoxometalates 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 polyoxometalates are able to be transported into cells, particularly into mitochondria. However, many of such polyanions are only slightly taken up by cells, obviously caused by negatively charged membranes.
On the way to explore the biological activity of polynuclear cluster compounds, we recently recognised POMs as a new class of potent enzyme inhibitors. Certain polyanionic complexes are able to inhibit extracellular 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.
We want to present a brief overview about the potential of POMs as E-NTPDase inhibitors and P2 receptor antagonists.

  • Lecture (Conference)
    4th EuCheMS Chemistry Congress, 26.-30.08.2012, Prague, Czech Republic

Publ.-Id: 17538

Look-Locker Acquisition for Estimation of partial volume fractions in ASL Data

Petr, J.; Schramm, G.; Hofheinz, F.; Langner, J.; Steinbach, J.; van den Hoff, J.

Due to the relatively low spatial resolution, arterial spin labeling (ASL) images are strongly affected by partial volume effects (PVE). This can make the qualitative analysis of ASL images difficult and it also significantly decreases the accuracy of cerebral blood flow (CBF) quantification. The PVE can be corrected for by using gray matter (GM) and white matter (WM) tissue segmentation of high-resolution T1-weighted images as proposed by Asllani et al1. The main drawback of this method is the need for precise knowledge of the partial volume ratios. However, the segmentation of T1-weighted images is very difficult at the border of GM and WM. Moreover, ASL images contain susceptibility induced deformations typical for EPI images and thus a correct registration with T1-weighted images is not always possible. Hence, the PVE correction using segmented T1-weighted images can introduce artifacts. In this study, we analyze an alternative method to obtain the partial volume ratios through the longitudinal magnetization relaxation times obtained from a Look-Locker sampling acquired in a multiple inversion time (TI) ASL sequence.

  • Contribution to proceedings
    ISMRM 20th Annual Meeting, 05.-11.05.2012, Melbourne, Australia
    2012 Annual Meeting Proceedings, 2001
  • Poster
    ISMRM 20th Annual Meeting, 05.-11.05.2012, Melbourne, Australia

Publ.-Id: 17537

Validierung eines Gammatomographen zur Bestimmung der Phasenanteilsverteilung in einem geneigt rotierenden Festbettreaktor

Arlit, M.

Das Institut für Fluiddynamik im Helmholtz-Zentrum Dresden-Rossendorf (HZDR) beschäftigt sich unter anderem mit der Untersuchung mehrphasiger verfahrenstechnischer Prozesse sowie der Entwicklung und Charakterisierung neuer effizienter Mehrphasenkontaktapparate und -reaktoren.
Ein solches neuartiges Konzept stellt der geneigt rotierende Festbettreaktor dar. Im Gegensatz zum zeitlich-periodischen Reaktorbetrieb erfolgt die Prozessintensivierung hier durch Aufprägung einer örtlichen Periodizität unter ansonsten stationären Betriebsbedingungen. Aus dieser veränderten Betriebsweise ergeben sich durch die Wahl von Reaktorneigung und Reaktordrehzahl zusätzliche Freiheitsgrade bei der Strömungsführung und damit zur Beeinflussung der Reaktorleistung.
Im Rahmen der Diplomarbeit ist ein tomographisches Messsystem für die Ermittlung von Phasenanteilen zu validieren. Weiterhin ist der Einfluss von Reaktorneigung und –drehzahl auf die Verteilung der Phasenanteile und den Druckverlust bei ausgewählten Gas- und Flüssigkeitsdurchsätzen zu untersuchen und mit dem etablierten Rieselbettreaktor zu vergleichen.

Keywords: Fixed bed reactor; Liquid Holdup; Phase Distribution; Inclination; Rotation; Gamma-ray Tomography

  • Diploma thesis
    TU Dresden, 2012
    130 Seiten

Publ.-Id: 17536

High specific activity 61Cu via 64Zn(p,α)61Cu reaction at low proton energies

Thieme, S.; Walther, M.; Preusche, S.; Rajander, J.; Pietzsch, H.-J.; Solin, O.; Steinbach, J.

The PET radionuclide 61Cu is accessible through several nuclear reactions. Besides the common production route via 61Ni(p,n)61Cu the 64Zn(p,α)61Cu reaction offers some advantages. Especially the comparatively cheap enriched 64Zn makes this process economical. For fast product purification and recycling of target material an ion exchanger cascade was developed. In addition a separation technique with a copper selective resin was tested. 61Cu with specific activities up to 1000 GBq/µmol was produced with these methods.

Publ.-Id: 17535

Absorption saturation in optically pumped graphene

Winzer, T.; Knorr, A.; Mittendorff, M.; Winnerl, S.; Sun, D.; Norris, T. B.; Helm, M.; Malic, E.

We investigate the saturation of the optical absorption in graphene induced by ultrafast optical pulses. Within a microscopic theory, we study the momentum-, angle-, and time-resolved interplay of anisotropic excitation, carrier-carrier and carrier-phonon scattering and its influence on the saturation of absorption and transmission as a function of the input intensity. In agreement with recent experiments, we observe a linear regime for the intensity-dependence of the transmission at low pump fluences and a nonlinear saturation in the high excitation regime. Applying 10 fs-pulses we obtain a saturation fluence of approximately 6.5mJ/cm2. We demonstrate how the interplay of Pauli-blocking and intensity-dependent relaxation determines the saturation behavior.

Publ.-Id: 17534

1550 nm ErAs:In(Al)GaAs Large Area Photoconductive Emitters

Preu, S.; Mittendorff, M.; Lu, H.; Weber, H. B.; Winnerl, S.; Gossard, A. C.

We report on high power Terahertz emission from ErAs-enhanced InAlAs-InGaAs superlattices for operation at 1550 nm. ErAs clusters act as ecient recombination centers. The optical power is distributed among a large, microstructured area in order to reduce the local optical intensity. A THz field strength of 0.7 V/cm (1 V/cm peak-to-peak) at 100 mW average optical power has been obtained, with emission up to about 4 THz in air, limited by the detection crystal used in the system.

Publ.-Id: 17533

Relaxation dynamics in epitaxial graphene investigated in the whole infrared spectral range

Winnerl, S.; Göttfert, F.; Mittendorff, M.; Schneider, H.; Helm, M.; Orlita, M.; Potemski, M.; Winzer, T.; Knorr, A.; Malic, E.; Sprinkle, M.; Berger, C.; de Heer, W. A.

As a gapless material with linear dispersion graphene is of great interest for the infrared spectral range. In this study we investigate the carrier relaxation dynamics of graphene in a wide spectral range from the near to the far-infrared, covering more than two orders of magnitude in photon energy.
The samples for this study are epitaxially grown graphene layers on the carbon-terminated face of SiC, which behave essentially like a stack of electronically uncoupled layers. In the near infrared (NIR) spectral range (photon energy 0.41 eV – 1.5 eV) degenerate and two-color experiments were performed. In the mid (MIR) and far infrared (FIR) range (photon energy 10 meV – 250 meV) degenerate pump-experiments were carried out employing the free-electron laser FELBE as a source.
In the NIR range pump-induced transmission was observed in two-color experiments with both red and blue shifted probe radiation. The signals in case of the blue shifted probe are evidence for a hot carrier distribution. The thermalization process is beyond the temporal resolution of our experiment (~ 100 fs in the near infrared). The observed decay times are in the range of 2 – 4 ps. In the MIR range we observe a significant increase of the relaxation time as the photon energy is decreased to values below the optical phonon energy (~200 meV). These experiments are complemented by microscopic theory based on the density matrix formalism [1]. The theory reflects the trends seen in the experiment well. It reveals the contribution of Coulomb scattering as well as the role of both optical and acoustic phonons in the observed dynamics.
In the FIR range an unexpected change from enhanced transmission to enhanced absorption is found (cf. Fig. 1). It is caused by an interplay of interband and intraband processes. For photon energies above twice the value of the Fermi energy, bleaching of interband transitions results in pump-induced transmission. For smaller photon energies, however, interband transitions are not possible. Here intraband transitions cause a heating of the carrier distribution, which is responsible for the intraband absorption.

  • Poster
    International Conference on Superlattices, Nanostructures and Nanodevices, 22.-27.07.2012, Dresden, Deutschland

Publ.-Id: 17532

Graphene excited with short infrared pulses: fundamental aspects and application perspectives

Winnerl, S.

Detailed knowledge of the ultrafast carrier dynamics is of crucial importance for the development of novel electronic and optoelectronic devices. Graphene, a gapless semiconductor, is very attractive for broadband photonic and optoelectronic applications. We performed pump-probe experiments on graphene samples in a wide spectral range from the near-infrared to the terahertz region (wavelength 0.8 µm – 120 µm). We show results on the relaxation dynamics and identify the main relaxation channels, namely optical phonons, intraband carrier-carrier scattering, and Auger-type processes [1]. Furthermore the saturation behaviour of the signals is investigated. This is important with respect to graphene-based saturable absorbers. Here we find that the intensity required for full beaching of graphene decreases by three orders of magnitude, when the pump wavelength is increased from 5 µm to 40 µm. Finally we present a fast graphene-based terahertz detector, which can be operated at room temperature.
This work was carried out in collaboration with M. Mittendorff, F. Göttfert, H. Schneider, and M. Helm from the Helmholtz-Zentrum Dresden Rossendorf, M. Orlita and M. Potemski from LNCMI-CNRS Grenoble. Modelling based on microscopic theory was performed by T. Winzer, E. Malic, and A. Knorr at the TU Berlin, sample growth by M. Sprinkle, C. Berger, and W.A. de Heer from the Georgia Institute of Technology, Atlanta. We acknowledge support by the German Science Foundation (DFG) in the framework of the priority program “Graphene”.
[1] S. Winnerl, M. Orlita, P. Plochocka, P. Kossacki, M. Potemski, T. Winzer, E. Malic, A. Knorr, M. Sprinkle, C. Berger, W. A. de Heer, H. Schneider, and M. Helm, Phys. Rev. Lett. 107, 237401 (2011).

  • Invited lecture (Conferences)
    7th International Conference on Surfaces, Coatings and Nanostructured Materials, 18.-21.09.2012, Prague, Czech Republic

Publ.-Id: 17531

Intersublevel spectroscopy on single InAs-quantum dots by terahertz near-field microscopy

Jacob, R.; Winnerl, S.; Fehrenbacher, M.; Bhattacharyya, J.; Schneider, H.; Wenzel, M. T.; von Ribbeck, H.-G.; Eng, L. M.; Atkinson, P.; Schmidt, O. G.; Helm, M.

Using scattering-type near-field infrared microscopy in combination with a free-electron laser, intersublevel transitions in buried single InAs quantum dots are investigated. The experiments are performed at room temperature on doped self-assembled quantum dots capped with a 70 nm GaAs layer. Clear near-field contrast of single dots is observed when the photon energy of the incident beam matches intersublevel transition energies, namely the p-d and s-d transition of conduction band electrons confined in the dots. The observed room-temperature linewidth of 5 – 8 meV of these resonances in the mid-infrared range is significantly below the inhomogeneously broadened spectral lines of quantum dot ensembles. The experiment highlights the strength of near-field micro-spectroscopy by demonstrating signals from bound-to-bound transitions of single electrons in a probe volume of the order of (100 nm)^3.

Publ.-Id: 17530

Cyclammonopropionic acid- a promising chelating system for radiocopper isotopes

Kubeil, M.; Peschel, L.; Stephan, H.; Steinbach, J.

A wide variety of radiometal-chelating bioconjugates have been studied intensively to design effective radiopharmaceuticals for diagnostic and therapeutic purposes. Azamacrocycles offer an enormous potential to achieve highly stable radiometal complexes and allow the covalent attachment of targeting and/or fluorescence units at the ligand skeleton. In this context, 1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetraacetic acid (TETA) is quite often used for the development of copper-based target-specific radiopharmaceuticals, although demetallation and transchelation occur in biological systems. In contrast, radiolabeling of propionic acid analogues has not been reported so far.
An appropriate building block to form very stable complexes with copper(II) is N-mono-(2-(carboxy)ethyl)-1,4,8,11-tetraazacyclotetradecane (Cyclammonopropionic acid, CMPA) which permits the formation of stable radiocopper complexes as well as a facile approach to obtain peptide multimers. An improved pharmaceutical targeting might be utilized due to the multimeric peptide functionalization of the chelating agent. The Epidermal-Growth-Factor-Receptor (EGFR), which is overexpressed on a multitude of tumors, has been chosen as target system to be studied.
Herein, we want to report about coupling reactions of the model dipeptide H-(L)-Leu-(L)-Ala-OH, which is a part of an EGFR-specific peptide, with the cyclammonopropionic acid skeleton. Radiolabeling of CMPA-peptide conjugates with copper-64 indicate high in vitro stability of the complexes formed. So far, this promising behavior may pave the way to develop attractive candidates for radiopharmaceutical applications.

  • Lecture (Conference)
    4th EuCheMS Chemistry Congress, 26.-30.08.2012, Prague, Czech Republic

Publ.-Id: 17529

Relaxation dynamics in graphene

Winnerl, S.

The peculiar properties of graphene, most importantly its gapless, linear band structure, give rise to exciting phenomena such as constant optical absorption over a wide range of photon energies and an unusual quantum Hall effect. Furthermore graphene is considered as an interesting material for electronic and optoelectronic applications. A good understanding of the relaxation dynamics is essential both for fundamental research and applications.
After an introduction into graphene research, I will present our results of pump-probe experiments in the mid- and far-infrared spectral range (photon energy 245 meV – 10 meV). We identify the role of optical phonons in the relaxation dynamics and discuss contributions from Auger-type processes and acoustic phonons. Furthermore an interesting change in sign of the pump-probe signal is observed at low photon energies (20 – 30 meV), which can be explained by an interplay of intraband and interband absorption processes [1]. In the second part of the talk I will focus on the relaxation dynamics in Landau-quantized graphene. Since the Landau levels (LLs) in graphene are not equidistant but scale with both the square root of the LL index and the square root of the magnetic field, optical pumping of individual LL-transitions is possible. Here we focus on the LL-1 → LL0 and LL0 → LL1 transitions, which exhibit equal transition energies but can be distinguished by applying either right-handed or left-handed circularly polarized light. Employing all four combinations of pumping and probing with right-handed and left-handed circularly polarized light, respectively, results in complex pump-probe signals: They involve fast and slow components, which exhibit either positive or negative signs. The relaxation dynamics in this regime can be understood by attributing the fast components to Auger-type processes and the slower components to phonon-mediated energy relaxation.
[1] S. Winnerl, M. Orlita, P. Plochocka, P. Kossacki, M. Potemski, T. Winzer, E. Malic, A. Knorr, M. Sprinkle, C. Berger, W. A. de Heer, H. Schneider, and M. Helm, Phys. Rev. Lett. 107, 237401 (2011).

  • Lecture (others)
    Seminar der Arbeitsgruppe Prof. Wiek, 06.07.2012, Bochum, Deutschland

Publ.-Id: 17528

Charakterisierung der Bindungseigenschaften rheniumhaltiger Clusterverbindungen gegenüber Dendrimeren

Kuhlmann, M.

kein Abstract verfügbar

  • Diploma thesis
    TU Dresden, Fakultät Mathematik und Naturwissenschaften, Fachrichtung Chemie und Lebensmittelchemie, 2009
    74 Seiten

Publ.-Id: 17527

The FELBE user facility

Seidel, W.; Winnerl, S.; Bhattacharyya, J.; Teich, M.; Fehrenbacher, M.; Drachenko, O.; Schneider, H.; Helm, M.; Bauer, C.; Gensch, M.; Schurig, R.; Lehnert, U.; Michel, P.

The FELBE user facility located at the Helmholtz-Zentrum Dresden-Rossendorf operates two free-electron lasers (FELs). Here we discuss the basic parameters of the FELs and the experimental opportunities at the facility. The FELs are based on the superconducting electron linear accelerator ELBE, which provides short (picosecond) electron bunches with energies up to 35 MeV at a 13 MHz repetition rate. The two FELs of FELBE (FELBE stands for FEL@ELBE) are equipped with two undulators, one for the mid-infrared spectral range (wavelengths 4 – 22 μm) and one for the far-infrared or THz range (wavelengths 20 – 250 μm). The key feature which distinguishes FELBE from other FEL user facilities is the possibility of “quasi cw” operation (meaning a continuous train of pulses, also called micropulses), made possible by the superconducting accelerator cavities. The FEL thus provides picosecond optical pulses at a repetition rate of 13 MHz. In this mode, the average power can reach up to 30 W (depending on the wavelength) corresponding to more than 1 μJ pulse energy. Additionally FELBE can be operated in a macrobunch mode and, via pulse-picking, a 1 kHz mode. The two FELs can be synchronized to a number of tabletop femtosecond and picosecond lasers, enabling two-color experiments from the near-infrared to the THz frequency range. The main techniques at FELBE are pump-probe spectroscopy [1-3] and time-resolved photoluminescence [4]. Furthermore there is a lab devoted to near-field microscopy [5,6]. Spectroscopy with FELBE radiation is also possible in pulsed high magnetic fields up to 70 T (150 ms magnetic pulse duration) [7,8]. FELBE is operated as a user facility, i.e., scientists from other institutions are invited to submit short research proposals and apply for beamtime.
[1] D. Stehr et al., Appl. Phys. Lett. 92, 051104 (2008).
[2] E.A. Zibik, et al., Nature Mat. 8, 803 (2009).
[3] S. Winnerl et al., Phys. Rev. Lett. 107, 237401 (2011).
[4] J. Bhattacharyya et al., Rev. Sci. Instr. 82, 103107 (2011).
[5] S.C. Kehr et al., Phys. Rev. Lett. 100, 256403 (2008).
[6] S.C. Kehr et al., Nature Comm. 2, 249 (2011).
[7] S. A. Zvyagin, et al, Rev. Sci. Instr. 80, 073102 (2009).
[8] O. Drachenko et al., Phys. Rev. B 79, 245207 (2011).

  • Poster
    503th Wilhelm and Else Heraeus Seminar Free-Electron Lasers: from Fundamentals to Applications, 10.-13.04.2012, Bad Honnef, Deutschland

Publ.-Id: 17526

Biofunctionalisation and 64Cu-labeling of pyridine-containing TACN ligands for specific targeting of EGF-receptor

Hesse, J.; Viehweger, K.; Stephan, H.; Steinbach, J.

The application of radiolabeled peptides in biomedicine is increasing rapidly and offers excellent prospects for the development of target-specific tumor imaging agents. In this perspective, the incorporation of the positron-emitting radionuclide 64CuII into ligand-peptide conjugates would permit the use of positron emitting tomography (PET) for tumor identification. An important requirement is that the resulting radiocopper-ligand complex is both kinetically and thermodynamically stable in vivo. We have developed a ligand scaffold based on bis(2-pyridylmethyl)triazacyclononane (DMPTACN) that forms very stable CuII complexes [1]. This structure allows for the introduction of linker groups, such as carboxylic acids, maleimide or isothiocyanate, thereby facilitating coupling of targeting molecules.
Among many characteristic targets of cancer tissue, the epidermal growth factor receptor (EGFR) is one of the most important mediators involved in the development of highly malignant tumors. This surface receptor is overexpressed in several tumor entities. The altered expression of EGFR during tumor growth, invasion, and metastasis present an interesting molecular target for tumor diagnosis and therapy.
Meanwhile, some specific peptides are identified capable of recognition EGFR-rich cancer tissue. Among these, the hexapeptide D4 (Leu-Ala-Arg-Leu-Leu-Thr) has been described [2]. We want to present the synthesis of a DMPTACN-peptide conjugate, applying thiourea coupling of the hexapeptide D4 by a DMPTACN isothiocyanate derivative. Radiochemical and radiopharmacological properties will be reported. In vitro binding characteristics of the [64Cu]CuII-labeled DMPTACN-peptide conjugate in EGFR overexpressing cancer cells ( FaDu, A431) using an immunoprecipitation protocol point to specific interactions.

[1] G. Gasser, L. Tjioe, B. Graham, M. J. Belousoff, S. Juran, M. Walther, J.-U. Künstler, R. Bergmann, H. Stephan, L. Spiccia, Bioconjugate Chem. 2008, 9, 719-730.
[2] S. Song, D. Liu, J. Peng, H. Deng, Y. Guo, L. X. Xu, A. D. Miller, Y. Xu, FASEB J. 2009, 23, 1396–1404.

  • Lecture (Conference)
    4th EuCheMS Chemistry Congress, 26.-30.08.2012, Prague, Czech Republic

Publ.-Id: 17525

Semiconductor quantum structures in high THz fields

Winnerl, S.

Electronic resonances in semiconductor quantum structures such as quantum wells and quantum dots are often accompanied by nonlinear phenomena. The intense, spectrally narrow radiation of a free-electron laser (FEL) is ideally suited for studying these nonlinear effects. We briefly discuss effects that can be treated in a perturbative way, such as the appearance of THz-sidebands around near-infrared absorption lines of quantum wells and quantum dots. Mainly we focus on an effect, which is beyond the perturbative description, namely the Autler-Townes splitting of excitonic absorption lines. Photogenerated electrons and holes in semiconductors form excitons, which exhibit a hydrogen-like energy spectrum. Due to the presence of the crystal lattice, however, the energy is scaled to the meV range. Excitation with intense THz pulses from an FEL "dresses" the excitonic states and leads to a splitting of energy levels. This splitting can be observed by probing the samples's transmission with broadband near-infrared radiation. While the main features, such as the dependence of the peak position on the THZ intensity, can be explained by a simple two-level model, other observations such as the relative strength of the peaks require more complex modelling. The mauin results presented here were obtained by M. Wagner, D. Stehr, H. Schneider and M. Helm on a sample grown by A. M. Andrews, S. Schartner, and G. Strasser.

  • Invited lecture (Conferences)
    503th Wilhelm and Else Heraeus Seminar Free-Electron Lasers: from Fundamentals to Applications, 10.-13.04.2012, Bad Honnef, Deutschland

Publ.-Id: 17524

Dose controlled irradiation of cancer cells with laser accelerated proton pulses

Zeil, K.; Baumann, M.; Beyreuther, E.; Burris-Mog, T.; Cowan, T. E.; Enghardt, W.; Karsch, L.; Kraft, S. D.; Laschinsky, L.; Metzkes, J.; Naumburger, D.; Oppelt, M.; Richter, C.; Sauerbrey, R.; Schürer, M.; Schramm, U.; Pawelke, J.

Proton beams are a promising tool for the improvement of radiotherapy of cancer, and compact laserdriven proton radiation (LDPR) is discussed as an alternative to established large-scale technology acilitating wider clinical use. Yet, clinical use of LDPR requires substantial development in reliable beam generation and transport, but also in dosimetric protocols as well as validation in radiobiological studies. Here, we present the first dose-controlled direct comparison of the radiobiological effectiveness of intense proton pulses from a laser-driven accelerator with conventionally generated continuous proton beams, demonstrating a first milestone in translational research. Controlled dose delivery, precisely online and offline monitored for each out of *4,000 pulses, resulted in an unprecedented relative dose uncertainty of below 10 %, using approaches scalable to the next translational step toward radiotherapy application.

Publ.-Id: 17523

Synthesis and cytotoxicity of pyridine and quinoline oxorhenium(V) complexes with tridentate (NS2, S-3)/monodentate (s) coordination

Segal, I.; Zablotskaya, A.; Kniess, T.; Shestakova, I.

New oxorhenium complexes with tridentate 3-thia- and 3-methylazapentane-1,5-dithiolate and monodentate pyridine and quinoline derivatives have been synthesized. As a result of investigation of biological activity a high cytotoxicity was found for the synthesized complexes in relation to tumor cells. The specificity of the 2-pyridylthiolato[3-(N-methyl)azapentane-1,5-dithiolato]oxorhenium(V) cytotoxic action towards cells of mouse hepatoma MG-22A on a background of low acute toxicity was established.

Keywords: oxorhenium(V) complexes; pyridine; quinoline; rhenium; cytotoxicity

Publ.-Id: 17522

Ultrafast relaxation dynamics close to the Dirac point in graphene

Winnerl, S.; Malic, E.

The relaxation dynmics in graphene is studied in the mid- and far-infrared spectral range.

  • Poster
    International Workshop on THz dynamics in carbon based nanostructures, 05.-07.03.2012, Dresden, Deutschland

Publ.-Id: 17521

Modularisierung der Geometrieinformation einer C++/Qt-basierten iterativen Bildrekonstruktion in der Positronen-Emissions-Tomographie

Domula, S.

kein Abstract verfügbar

  • Diploma thesis
    Hochschule für Technik und Wirtschaft Dresden, 2012
    78 Seiten

Publ.-Id: 17520

Improved composit targets for small scale Cu-64 production comparing Au- and Pt-foils as Ni-64 backing

Walther, M.; Preusche, S.; Füchtner, F.; Pietzsch, H.-J.; Steinbach, J.

Advantages of a stacked assembly of target support components for 64Cu production via 64Ni(p,n)64Cu reaction were reported recently.1 The present work shows the applicability of these composit targets for beam currents up to 22 µA. Gold and platinum foils were evaluated as 64Ni backing. The effective specific activity (ESA) and specific activity (SA) were determined by TETA titration at room temperature and at 80 °C and compared with additional copper quantification results via stripping voltammetric trace analysis (VA).

  • Lecture (Conference)
    14th International Workshop on Targetry and Target Chemistry (WTTC14), 26.-29.08.2012, Playa del Carmen, Mexico
  • Contribution to proceedings
    14th International Workshop on Targetry and Target Chemistry, 26.-29.08.2012, Playa del Carmen, Mexico
    AIP Conference Proceedings Vol. 1509: American Institute of Physics, 978-0-7354-1127-2, 81-83
    DOI: 10.1063/1.4773945

Publ.-Id: 17519

Ultrafast relaxation dynamics close to the Dirac point in graphene

Winnerl, S.; Malic, E.

The relaxation dynamics at low photon energies (10 meV - 300 meV) is studied experimentally. Comparison with mcroscopic theory allows us to identify teh role of carrier-carrier scattering and scattering by optical and acoustic phonons.

  • Poster
    1st Workshop of the Priority Programme Graphene, 04.-08.12.2011, Rothenfels, Deutschland

Publ.-Id: 17518

Four years experience in operation and maintenance of the [18F]F2 proton target at the Rossendorf Cyclone® 18/9 cyclotron

Preusche, S.; Füchtner, F.; Steinbach, J.

Experience in operation of the [18F]F2-p target to achieve stable and sufficient activity yields and reaction yields for [18F]FDOPA preparations are summarized. Hints for maintenance are given.

  • Lecture (Conference)
    The eigth workshop of the "CYCLONE 18/9 + 10/5 USER COMMUNITY", 09.-13.10.2010, Coimbra, Portugal

Publ.-Id: 17517

Strahlenschutz im PET-Zentrum Dresden-Rossendorf - Überblick -

Preusche, S.; Füchtner, F.; Zessin, J.; Beuthien-Baumann, B.; Bergmann, R.; Walther, M.

kein Abstract verfügbar

  • Lecture (others)
    Strahlenschutz-Kolloqium, VKTA, 02.09.2010, Rossendorf, Deutschland

Publ.-Id: 17516

Transport von Kohlenstoffnanoröhrchen in Umweltsystemen

Schymura, S.

Einführung in den Transport von Kohlenstoffnanoröhrchen in Umweltsystemen

Keywords: carbon nanotubes; transport

  • Communication & Media Relations
    Poster & Handout (Lange Nacht der Wissenschaft) 29.06.2012
    1 Seiten

Publ.-Id: 17515

Three years experience in operation and maintenance of the [18F]F2 proton target at the Rossendorf Cyclone® 18/9 cyclotron

Preusche, S.; Füchtner, F.; Steinbach, J.

An increasing demand of radiopharmaceuticals based on electrophilic reaction with [18F]F2 gas (for instance [18F]FDOPA) led to an upgrade of the IBA [18F]F2 gas target system in summer 2007. The more than 10 years operated [18F]F2 deuteron target [20Ne(p,α)18F] was not able to meet the increasing requirements in terms of activity anymore and was thus replaced by an IBA [18F]F2 proton gas target [18O(p,n)18F] based on the so-called “double-shot” ‘irradiation method by R.J. Nickles [1]. The upgrade itself was done by IBA.
We run the Cyclone® 18/9 cyclotron in routine operation for more than 14 years. One of the specific features of the Rossendorf PET Center is the Radionuclide transport system (RATS) [2], 500 m in length that bridges the distance from the cyclotron to the radiopharmaceutical laboratories. The activity at the end of bombardment (EOB) is calculated taking in account the transfer time and experimental data of activity losses (about 30%) in the transfer tube [2].

  • Lecture (Conference)
    WTTC13 - 13th International Workshop on Targetry and Target Chemistry, 25.-28.06.2010, Risoe, Denmark
  • Poster
    WTTC13 - 13th International Workshop on Targetry and Target Chemistry, 25.-28.06.2010, Risoe, Denmark

Publ.-Id: 17514

Entwicklung maleinimidhaltiger, bifunktioneller Markierungsbausteine auf der Basis von 1,4,7-Triazacyclononanliganden

Fähnemann, S.

kein Abstract verfügbar

  • Master thesis
    Hochschule für Technik und Wirtschaft Fachbereich Maschinenbau/Verfahrenstechnik Studiengang Chemie, 2008
    75 Seiten

Publ.-Id: 17513

Radiometallmarkierung und kolloid-chemische Charakterisierung von magnetischen Nanopartikeln

Fähnemann, S.

kein Abstract verfügbar

  • Diploma thesis
    Hochschule für Technik und Wirtschaft Fachbereich Maschinenbau/Verfahrenstechnik Studiengang Chemie, 2007
    70 Seiten

Publ.-Id: 17512

Enhanced ion heating induced by collisional shocks generated by an ultra-short intense laser pulse interacting on a heterogeneous solid target

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

To achieve above keV ion temperatures, we propose a method to deposit enough energy of an ultra-short intense laser pulse into a multilayer solid target by creating an ion shock wave. In the scenario studied the bulk ions are heated efficiently when the shock wave is created inside the target and propagates through the target. To study the feasibility of this scheme a heterogeneous solid target with of CD-Al-CD multi-layer structure is studied using Particle-in-Cell (PIC) simulations. These simulations give insight into the dynamics of the shock generation by an ultra-short intense laser pulse (~100fs, 10^20W/cm2). The simulations show that shock waves are created in the interfaces of the CD-Al layer. Deuteron temperatures in the keV range are observed after the shock. Such high ion temperatures may be benefitial for neutron production via D-D fusion reactions.

Keywords: Laser plasma physics; ion heating; kev temperature

  • Poster
    International Workshop on Laser-Plasma Interaction at Ultra-High Intensity, 16.-20.04.2012, Dresden, Germany

Publ.-Id: 17511

A Critical Review on Multiscale Material Database Requirement for Accurate Three-Dimensional IC Simulation Input

Yeap, K.-B.; Röllig, M.; Hübner, R.; Gall, M.; Sukharev, V.; Zschech, E.

Material behavior and properties at different scales, from nanometers to millimeters, are the input data needed for a model-based design-for-manufacturing approach of 3-D through-silicon-via (TSV) stacked ICs. In particular, mechanical and thermomechanical material data have to be used as input for physics-based modeling and simulation of stress-induced phenomena in 3-D stacks. Both package-and wafer-level properties, including their interaction, have to be considered. This paper reviews the thermomechanical and mechanical properties of several structures: time-dependent properties of solder materials (millimeter and micrometer scales), microstructure-dependent properties of Cu TSVs (micrometer scale), and process-dependent properties of ultralow-k materials in on-chip interconnect stacks (10-nm scale). To minimize the keep-out zone for active devices in the stress-affected surrounding of TSVs, while maintaining the device performance during 3-D TSV stacking of ICs, highly accurate material data are needed as input for the thermomechanical stress simulation. A similar strategy is supposed to be developed for a model-based design-for-reliability approach of 3-D TSV stacked ICs.

Keywords: Device performance; material database; multiscale simulation; through-silicon via (TSV); 3-D integration

Publ.-Id: 17510

Radiolabelling of engineered nanoparticles for environmental particle tracing - HZDR – Cyclotron facility – Radionuclide production

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

Radiolabelling of engineered nanoparticles for environmental particle tracing --> Presentation of the radionuclide production at the HZDR - cyclotron facility in Leipzig together with yields and stability of different radiolabelling strategies for nanoparticles

  • Lecture (Conference)
    JRC-QNano-seminar, 15.06.2012, Ispra, Italia

Publ.-Id: 17509

Untersuchung des Lebenszyklus von TiO2- und Ag0-Nanopartikeln - NanoTRACK

Franke, K.

Untersuchung des Lebenszyklus von TiO2 - und Ag0 - Nanopartikeln mithilfe Radiotracern. Radionuklidherstellung, Markierungsausbeuten, Markierungsstabilität und erste Ergebnisse zur Partikelfreisetzung aus Lacksystemen werden vorgestellt.

  • Lecture (Conference)
    2. Clustertreffen der Fördermaßnahmen NanoCare und NanoNature, 13.-14.03.2012, Frankfurt /Main, Deutschland

Publ.-Id: 17508

CNT-Modification and radiolabelling at the HZDR

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

Presentation of results on microwave-assisted carbon nanotube modification and iodine radiolabelling

Keywords: carbon nanotubes; modification; radiolabelling

  • Lecture (others)
    Seminar at the JRC-cyclotron facility within the Qnano project: "Be-7 Recoil labelling of multi-wall carbon nanotubes", 04.-15.06.2012, Ispra, Italien

Publ.-Id: 17507

Rapid carbon nanotube modification and radiolabelling for particle tracing applications

Schymura, S.; Franke, K.; Lippmann-Pipke, J.

Presentation of results on carbon nanotube modification via microwave-assisted oxidation and iodine radiolabelling of carbon nanotubes for particle tracing applications

Keywords: carbon nanotubes; radiolabelling; modification

  • Poster
    2. NanoNature Clustertreffen, 12.-14.03.2012, Frankfurt, Deutschland

Publ.-Id: 17506

Eu3+ in NMR spectroscopy – a helpful tool in tracking binding sites

Kretzschmar, J.; Barkleit, A.; Brendler, V.

Lanthanides have become a useful tool in NMR spectroscopy within the last 40 years. Due to their paramagnetic properties they can be utilized as probes to determine the binding sites of biologically or environmentally relevant organic molecules as they cause significant line broadenings and / or paramagnetic induced shifts [1-3].
Actual research deals with the interactions, thermodynamic and kinetic behaviour of actinides and biomolecules. Lanthanides can easily be used as inactive analogues for trivalent actinides in consequence of their similar chemistry.
Glutathione is a high concentrated intracellular reducing agent, playing a major role in detoxification processes. Important targets are electrophiles such as heavy metal ions. With its high natural abundance, different functional groups and reducing ability, this tripeptide provides outstanding characteristics for actinide complexation research and, furthermore by its small size it is well suited as a model molecule in NMR spectroscopy.
1H-NMR signals are shifted and broadened by the paramagnetic induced shift of the Eu3+ with their 4f6 electron configuration. These interactions between nuclear spins and electron unpaired spins exhibit a strong distance dependency. The closer the binding site, the bigger the shift of the signals.
From these findings, it can be derived that the carboxylate group of the glutamate residue is the most potential binding site at pH 2.9. According to the aqueous speciation, the glycine carboxylic acid group is only partially deprotonated and therefore less involved in complexation. The thiol group does not interact with the metal ion.

Acknowledgement: We thank Dr. Erica Brendler, Technische Universität Bergakademie Freiberg, for providing the possibility to acquire 2D-NMR spectra.

[1] C. C. Hinckley, J. Am. Chem. Soc. 1969, 91, 5160-5162.
[2] O. A. Gansow, M. R. Willcott, R. E. Lenkinski, J. Am. Chem. Soc. 1971, 93, 4295-4297.
[3] I. Bertini, C. Luchinat, G. Parigi, Solution NMR of paramagnetic molecules, Vol. 2, in: Current methods in inorganic chemistry, Elsevier, Amsterdam, 2001.

Keywords: Advanced Techniques in Actinide Spectroscopy (ATAS); Eu3+; glutathione; NMR spectroscopy

  • Lecture (Conference)
    International Workshop on Advanced Techniques in Actinide Spectroscopy (ATAS), 05.-07.11.2012, Dresden, Deutschland

Publ.-Id: 17505

Electromagnetic fields and electron dynamics in Traveling-wave Thomson scattering

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

The Traveling-wave Thomson scattering (TWTS) scheme is a novel high-yield Thomson scattering geometry using ultrashort laser pulses with tilted pulse fronts. Combined with relativistic electron bunches this can be utilized as an optical undulator or as an optically driven free electron laser for generation of high-brightness, narrow bandwidth X-Ray pulses. In order to examine the wave-optical propagation of these TWTS pulses we developed an analytical formalism to calculate the electrical field of a spatio-temporal distorted laser pulse which has been diffracted at a grating of arbitrary periodicity function. This allows for numerical analysis of a TWTS laser pulse in terms of its envelope and dispersion properties. We use this to investigate the applicability of the scheme as an optical undulator and free electron laser.

Keywords: travelling wave; thomson scattering; x-ray; laser pulse; vls grating

  • Poster
    International Workshop on Laser-Plasma Interaction at Ultra-High Intensity - ENLITE 12, 16.04.-20.07.2012, Dresden, Deutschland

Publ.-Id: 17504

Quantitative accuracy of attenuation correction in the Philips Ingenuity TF whole-body PET/MR system A direct comparison with transmission-based attenuation correction

Schramm, G.; Langner, J.; Hofheinz, F.; Petr, J.; Beuthien-Baumann, B.; Platzek, I.; Steinbach, J.; Kotzerke, J.; van den Hoff, J.

Objective: Evaluation of the quantitative accuracy of MR-based atten- uation correction (MRAC) in the Philips Ingenuity TF whole-body PET/MR.

Materials and methods: In 13 patients, PET emission data from the PET/MR were reconstructed using two different methods for attenuation correction. In the first reconstruction the vendor-provided standard MRAC was used. In the second reconstruction, a coregistered transmission-based attenuation map from a second immediately preceding investigation with a stand-alone Siemens ECAT EXACT HR+ PET scanner was used (TRAC). The two attenuation maps were compared regarding occurrence of segmentation artifacts in the MRAC procedure.
Standard uptake values (SUVs) of multiple VOIs (liver, cerebellum, hot focal structures at various locations in the trunk) were compared between both reconstructed data sets. Furthermore, a voxel-wise intensity correlation analysis of both data sets in the lung and trunk was performed.

Results: VOI averaged SUV differences between MRAC and TRAC were as follows (relative differences, mean ± standard deviation): (+12 ± 6)% cerebellum, (−4 ± 9% liver, (−2 ± 11)% hot focal structures. The fitted slopes of the voxel-wise correlations in the lung and trunk were 0.87 ± 0.17 and 0.95 ± 0.10 with averaged adjusted R2 -values of 0.96 and 0.98, respectively. These figures include two instances with partially erroneous lung segmentation due to artifacts in the underlying MR images.

Conclusion: The MR-based attenuation correction implemented on the Philips Ingenuity PET/MR provides reasonable quantitative accuracy. On average, deviations from TRAC-based results are small (on the order of 10% or below) across the trunk, but due to interindividual variability of the segmentation quality, deviations of more than 20% can occur.
Future improvement of the segmentation quality would help to increase the quantitation accuracy further and to reduce the inter-subject variability.

  • Open Access Logo Magnetic Resonance Materials in Physics, Biology and Medicine 25(2013)1, 115-126
    Online First (2012) DOI: 10.1007/s10334-012-0328-5

Publ.-Id: 17503

Simulation of electro-magnetic emissions in laser-particle interactions

Pausch, R.; Debus, A.; Widera, R.; Bussmann, M.; Schramm, U.

Modern laser-plasma simulations are able to model complex plasma processes. However, since particle dynamics within a plasma are usually not directly accessible to experiments, there is interest to compare experimental results with Particle-In-Cell (PIC) simulations.
One way to accomplish this task is to simulate the electro-magnetic emissions from both relativistic and sub-relativistic plasma electrons.
Here we present a newly developed software for spectral analysis of laser-plasma phenomena and for simulating novel light sources. Moreover, a GPU based code was developed to work directly within PIConGPU.

Keywords: laser-plasma simulations; electro-magnetic emission; spectral analysis; laser-plasma phenomena; novel light sources; PIConGPU

  • Poster
    International Workshop on Laser-Plasma Interaction at Ultra-High Intensity 2nd Dresden Exchange on Laser-Plasma Interaction Theory ENLITE, 16.-20.04.2012, Dresden, Germany

Publ.-Id: 17502

18F-labelled CCR1-receptor antagonist is not suitable for imaging of Alzheimer's disease

Beuthien-Baumann, B.; Holthoff, V.; Mäding, P.; Bergmann, R.; Pawelke, B.; Holl, G.; von Kummer, R.; Kotzerke, J.; van den Hoff, J.

Diagnosis of Alzheimer’s disease (AD) with positron emission tomography (PET) using 18F-fluorodeoxyglucose (FDG) relies on typical alterations of brain glucose metabolism which are, however, not disease specific. Amyloid-β imaging has not entered clinical routine yet. Post mortem histological specimen of brain tissue from AD patients revealed enhanced expression of the chemotactic cytocine receptor 1 (CCR1). Participants, methods: CCR1-antagonist ZK811460 was labeled with fluorine-18 to explore its possible use as specific diagnostic tool in AD. Tracer characterization comprising PET imaging of brain and metabolite analysis was performed in AD patients and controls.
Results: Neither qualitative evaluation nor quantitative compartment analysis of PET data did show any enhanced binding of the 18F-labeled CCR1-antagonist in the brain of AD patients or controls.
Conclusion: 18F-ZK811460 did not fulfill the expectation as diagnostic tracer in PET imaging of AD.

Keywords: Alzheimer’s disease; Positron emission tomography; CCR1 receptor antagonist

Publ.-Id: 17501

Assessment of low-dose radiotoxicity in microorganisms using calorimetric metabolic monitoring

Obeid, M.

At this project the effects of low doses of radionuclides and heavy metals on the metabolic activity of microorganisms was assessed, using the state of the art Thermal Activity monitor microcalorimeter, TAM(III), as a novel monitoring tool in this study. Therefore, the toxicity was measured as the metabolic response for these low doses reflected by bacterial growth thermograms. The bacterial strain used in this project, Paenibacillus sp. JG-TB8, was isolated from a soil sample of the uranium mining waste pile “Haberland” (Johanngeorgenstadt, Saxony, Germany) by Thomas Reitz [4]. This bacterial strain was exposed to different concentrations in the range of micromolar of Eu(III) and U(VI) salts. Thetoxicity of europium chloride (Eu(III)Cl3) as a heavy metal was reflected by the thermogram as a decrement of its maximal heat flow. In contrast, the effect of the uranium salts was more complicated. It showed a strong dependence on temperature and pH. Correlation of the degree of toxicity with concentration of the uranium salt was observed strongly at 30 °C in R2A medium, while it showed more constructive effect related to the usage of uranium as energetic source for the metabolic activity of the PB at 20°C. The mentioned thermograms showed that the general toxic effect of uranium is present but does not scale systematically with the applied concentrations. The data reveal that the thermal signature of a contaminant is unique for each concentration.

Keywords: calorimetry; radionuclide; europium; uranium

  • Master thesis
    Technische Universität Dresden, 2011
    100 Seiten

Publ.-Id: 17500

Use of targeted therapy for refractory ALK-positive anaplastic large cell lymphoma as a bridging strategy prior to allogeneic transplantation

Ordemann, R.; Stöhlmacher, J.; Beuthien-Baumann, B.; Platzek, I.; van den Hoff, J.; Kroschinsky, F.; Middeke, J. M.; Platzbecker, U.; Zietz, C.; Bornhäuser, M.; Ehninger, G.

Letter to the editor - kein Abstract verfügbar

Publ.-Id: 17499

Spektroskopische Untersuchungen zur Struktur und Funktion der Kupfer-ATPase CopB von E.Hirae

Groß, M.

The aim of this study is to investigate the structure and function of P-type-ATPases. Enterococcus hirae is a gram-positive lactic acid bacterium with two copper ATPases CopA and CopB. They show sequence similarity to known P-type-ATPases. The monovalent copper exporting ATPase CopB is a central regulator for copper homeostasis in E. hirae which shows 39 % sequence similarity to the sarcoplamic reticulum calcium ATPase SERCA1a of rabbit hind leg muscle (Oryctolagus cuniculus). SERCA1a undergoes large conformational changes of cytoplasmatic and transmembrane domains to translocate ions. Despite some former work, the transport of copper and the biochemical properties of the ATPase, however, has to be analyzed and the observation of hydrolytic activities has to be pursued. During thesis work the functional status of conformational states was studied by spectroscopy work on metal and nucleotide binding. The ability of nonionic detergents to stabilize the membrane-bound enzymes was used to work in lipid analogue environment, whereby the effect of light scattering of lipid systems is prevented. I have investigated the secondary structure of purified CopB in the absence and presence of the non-hydrolyzable ATP analogs ATPgS, mantATP and silver (a redox inert Cu+ analog) using circular dichroism spectroscopy. Binding of metals unfolds the protein, whereas ATP analogs partially elliminate this effect. ATPgS and silver form an optically active complex. Negative and positive CD peaks appear, at 257 nm and 277 nm, respectively, at a ratio of 1:3 of Ag:ATPgS corresponding to the predominant species ATPgS3Ag4. CopB competes with complex formation by binding both ATPgS and silver. To my knowledge this is the first description of such a complex. It is used in this work as a possible high sensitive realtime ATPase monitor. This assay could ultimately be exploited to determine binding affinities of nucleotide, silver and CopB in enzyme assays in real time. In the present work it is used to determine binding affinitiy of CopB to ATPgS. In addition to check the influence of the binding of ATP analogs and silver on stability of CopB, the protein was denaturated in the absence and presence of ATPgS, mantATP, ADP and silver. Whereas ATPgS and mantATP stabilize CopB, the same nucleotide-CopB complex is destabilized by silver. This evidences a strong negative coupling between the nucleotide and metal binding site as an important output of my work.

Keywords: copper; ATPase; CopA; CopB; circular dichroism; unfolding

  • Diploma thesis
    TU Dresden, 2011
    90 Seiten

Publ.-Id: 17498

New Bispidine-Derivatives for dual-modality imaging

Fähnemann, S.; Walther, M.; Stephan, H.; Kraus, W.; Emmerling, F.; Steinbach, J.

The diagnostic evaluation and treatment of complex diseases, like cancer, is very difficult using only standing alone methods with their individual limitations. To overcome these restrictions, a combination of different imaging modalities will be conceivable. The radionuclide based positron emission tomography (PET) and single photon emission computed tomography (SPECT) are useful for functional imaging. To obtain anatomical information, computer tomography (CT) and magnetic resonance imaging (MRI) can be used, whereas fluorescence-based optical imaging finds application in surgery guidance. [1]

Extensive research effort has shown, that 3,7-diazabicyclo[3.3.1]nonane-derivatives (bispidines) built up thermodynamic and kinetic very stable complexes with copper(II) ions (logK = 16.28) [2]. Different functional groups of the backbone (hydroxyl and carboxyl groups) provide the opportunity for simultaneous attachment of dyes and biomolecules (e. g. peptides, proteins, antibodies) as vector molecules. After that functionalization, the complexation of radioactive copper isotopes (61Cu, 64Cu, 67Cu) allows visualization of cancer tissue with PET and radiotherapy.

The hydroxyl group at C9 was functionalized using nitrophenyl chloroformate for active ester generation. Therefore, a fluorescence label could be coupled to the bispidine by urethane bond formation.

We will report about the versatility of bispidines as compounds to realize different functionalities in one molecule. The synthesis and characterization of such derivatives, and radiolabeling experiments with the PET-radionuclide 64Cu will be discussed.

[1] Kuil, J., Velders, A. H., van Leeuwen, F. W. B.; Bioconjugate Chem. 2010, 21, 1709-1719.
[2] Juran, S., Walther, M., Stephan, H., Bergmann, R., Steinbach, J., Kraus, W., Emmerling, F., Comba, P.; Bioconjugate Chem. 2009, 20, 347-359.

  • Lecture (Conference)
    4th EuCheMS Chemistry Congress, 26.-30.08.2012, Prague, Czech Republik

Publ.-Id: 17497

The impact of the bispidine structure on the stability of their Cu(II) complexes

Hunoldt, S.; Comba, P.; Morgen, M.; Steinbach, J.; Stephan, H.

Rigid bispidine (3,7-diazabicyclo[3.3.1]nonane) derivatives have been shown to form stable complexes, particularly with first row transition metal ions [1]. The variable number, type and position of donor groups provide a variety of tailor-made coordination sites for specific metal ions. Furthermore, the bispidine skeleton opens suitable pathways to introduce biomolecules, which are important in view of the pharmaceutical targeting of such complexes. Due to these interesting features, bispidines are predestined as attractive bifunctional chelating agents for the development of target-specific copper-based radiopharmaceuticals. In this perspective, a hexadentate bispidine ligand consisting of pyridine units in the positions C-2, C-4, N-3, and N-7 was conjugated to the tumour-seeking peptide bombesin. The 64Cu-labeled bioconjugate is accumulated in human prostate tumors to allow clear visualization of the tumor tissue [2].
In order to optimize the radiopharmaceutical behavior, further bispidine ligands have been developed with different denticity (tetra-, penta, hexadentate) with pyridine and/or methoxypyridine donor groups and with the possibility to introduce functionalities, such as targeting units and fluorescence labels in view of pharmaceutical targeting as well as dual labeling (PET and optical imaging).
These ligands and the important properties of their CuII complexes, e. g. stabilities, exchange kinetics and partition coefficients (64Cu: octanol/water) will be reported.

[1] P. Comba, M. Kerscher, W. Schiek, Progr. Inorg. Chem. 2008, 55, 613-704.
[2] S. Juran, M. Walther, H. Stephan, R. Bergmann, J. Steinbach, W. Kraus, F. Emmerling, P. Comba, Bioconjugate Chem. 2009, 20, 347-359.

Keywords: bispidine; copper(II); radiolabeling

  • Poster
    4th EuCheMS Chemistry Congress, 26.-30.08.2012, Prague, Czech Republic

Publ.-Id: 17496

Diffusion of U(VI) in Opalinus Clay: Influence of temperature and humic acid

Joseph, C.; van Loon, L. R.; Jakob, A.; Steudtner, R.; Schmeide, K.; Sachs, S.; Bernhard, G.

The diffusion of U(VI) (c0 = 1×10-6 M) in compacted Opalinus Clay from the Mont Terri underground laboratory, Switzerland, was studied in the absence and presence of humic acid (10 mg/L) at two different temperatures (25 °C, 60 °C) under anaerobic conditions. As background electrolyte a synthetic Opalinus Clay pore water (pH 7.6, I = 0.36 M) was used. The diffusion-accessible porosity, ε, was determined for each Opalinus Clay bore core sample by through-diffusion experiments with tritiated water (HTO) before the U(VI) diffusion experiments were carried out. The values for the effective diffusion and distribution coefficients De and Kd obtained for U(VI) and humic acid at 25 °C as well as at 60 °C showed that humic acid has no significant influence on the U(VI) diffusion. The diffusion profiles of humic acid in Opalinus Clay at 25 and 60 °C indicate the contributions of two different humic acid particle size fractions (< 1 kD and 10-100 kD). The small-sized humic acid fraction diffused through the whole Opalinus Clay samples at both temperatures within the three months duration of the U(VI) diffusion experiments. At 60 °C, diffusion profiles of two different U(VI) species were observed. In a separate experiment the U(VI) speciation in the source reservoir solution at 60 °C was analyzed by laser-induced fluorescence spectroscopy, photon correlation spectroscopy and scanning electron microscopy with an energy dispersive X-ray detector. The two diffusion profiles could be attributed to an unknown colloidal and a known aquatic U(VI) species (Ca2UO2(CO3)3(aq)). The diffusion results showed that the interaction of U(VI) and of the large-sized humic acid colloid fraction with the clay is stronger at 60 °C. An increase of Kd from 0.025 ± 0.003 m3/kg at 25 °C to 0.25 ± 0.05 m3/kg for U(VI)colloidal at 60 °C was determined. In addition, the value for De of U(VI) increased with increasing temperature. Using the De values at 25 and 60 °C, a preliminary activation energy for the diffusion of U(VI) through Opalinus Clay of 10 kJ/mol was calculated. The observed increased Kd and De values for U(VI)aqueous at 60 °C compensated each other to almost equal values of the apparent diffusion coefficient Da at 25 and 60 °C. Hence, the migration of U(VI) through OPA was not significantly influenced by the investigated higher temperature of 60 °C.

Keywords: uranium(VI); diffusion; Opalinus Clay; humic acid; temperature; LIFS; SEM-EDX; PCS

Publ.-Id: 17495

Investigation of the life cycle of nanoparticles by means of radiolabelling – NanoTRACK

Hildebrand, H.; Franke, K.

Presentation of current activities and results from the NanoTrack project, especially results from radiolabelling of Ag(0) and TiO2 nanoparticles

Keywords: radiolabelling Ag(0) TiO2 nanoparticles

  • Poster
    2. Clustertreffen NanoCare/NanoNature, 13.-14.03.2012, Frankfurt, Deutschland

Publ.-Id: 17494

Radiolabelling of commercial Ag0 and TiO2 nanoparticles with 110mAg and 44/45Ti for life-cycle studies and results from the QNANO research stay at JRC

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

Presentation of the current research activivities concerning the radiolabelling of Ag(0) and TiO2 nanoparticles within the NanoTrack project at HZDR and first results from the QNANO research stay at the Joint Research Center in Ispra, Italy

Keywords: radiolabelling of nanoparticles

  • Lecture (others)
    QNANO seminar within the QNANO research stay at JRC in Ispra, Italy, 15.06.2012, Ispra, Italia

Publ.-Id: 17493

Multi edge X-ray absorption spectroscopy of thorium, neptunium and plutonium hexacyanoferrate compounds

Dumas, T.; Charbonnel, M. C.; Charushnikova, I. A.; Conradson, S. D.; Fillaux, C.; Hennig, C.; Moisy, P.; Petit, S.; Scheinost, A. C.; Shuh, D. K.; Tyliszczak, T.; Den Auwer, C.

Although transition metal cyano bimetallic compounds have been well known for decades for their interesting optical and magnetic properties, reports on actinide hexacyanoferrate compounds are scarce. For instance, a thorough structural description is still lacking. Another question is the possible covalency or charge transfer effects in these materials that are known to foster electron delocalization with a large variety of transition metal cations. In this paper, new members of the actinide(IV) hexacyanoferrates have been synthesized with Th, Np and Pu. This is the first review of thorium to plutonium hexacyanoferrate compounds since the early investigations during the Manhattan Project some 70 years ago. We have carried out an extensive structural characterization using powder X-ray Diffraction (XRD), X-ray Absorption Spectroscopy (XAS) and X-ray microscopy for the plutonium adduct. The crystallographic space group of microcrystalline Th, Np and Pu hexacyanoferrate compounds appears to be very similar to that of the early lanthanide adducts, suggesting that the tetravalent actinides are arranged in a tricapped trigonal prismatic polyhedron of coordination number 9, in which the actinide atom is bonded to six nitrogen atoms and to three water molecules. Further combined analysis of the iron K-edge and actinide LIII-edge EXAFS data and XRD data provided the basis for a threedimensional molecular model. Structural data in terms of actinide–ligand bond lengths have been compared to those reported for the parent lanthanide(III) compounds, confirming the structural similarities. In addition, two new structures with the thorium cation have been obtained and described using single-crystal XRD: (H5O2)[Th(DMF)5(H2O)]2[Fe(CN)6]3 and [Th(DMF)4(H2O)3][Fe(CN)6](NO3)2H2O. This structural description of the Th, Np and Pu hexacyanoferrate system will be followed by a semi-quantitative electronic description of the actinide–cyano bond using NEXAFS data analysis in a coming paper.

Keywords: XAFS; Th; Np; Pu

  • New Journal of Chemistry 37(2013), 3003-3016
    Online First (2013) DOI: 10.1039/c3nj00318c

Publ.-Id: 17492

Time-resolved laser-induced fluorescence spectroscopy (TRLFS) of aqueous Am(III) complexes at ambient and elevated temperature

Barkleit, A.; Acker, M.; Geipel, G.; Bernhard, G.

Time-resolved laser-induced fluorescence spectroscopy (TRLFS) has been extensively used as a sensi-tive and selective technique to analyze actinide complexation with inorganic and organic ligands in trace metal concentrations. However, the application of TRLFS onto Am(III) complexation systems was up to now limited because of the much lower luminescence intensity and much shorter lifetime of Am(III) in comparison to U(VI) or Cm(III).
We investigated the complexation behavior of Am(III) complexes with lactate (Lac) and substituted benzoic acids like pyromellitic acid (1,2,4,5-benzenetetracarboxylic acid, BTC) at ambient and ele-vated temperatures with TRLFS.
Using the emission of the 5D1-7F1 transition at around 691 nm, spectral data like luminescence life-times, luminescence maxima and complex stability constants were calculated. Temperature dependent stability constants were determined to estimate thermodynamic data (reaction enthalpy, reaction en-tropy).
The Am(III) aquo ion shows at pH 4-6 a luminescence lifetime of 23 ns, corresponding to approxi-mately 9 coordinating water molecules. Complexation with BTC shows no change of the excitation and emission maximum but an increase of the luminescence intensity and lifetime. The luminescence lifetime was prolonged to 27 ns, corresponding to 8 remaining water molecules in the first coordina-tion shell. This indicates an exchange of 1 water molecule with 1 coordination site of the ligand, re-sulting in an Am-BTC 1:1 complex [1]. In contrast, complexation with lactate causes a red shift of the excitation wavelength of Am(III) (Fig. 1), resulting in a red shift of the luminescence emission maxi-mum of about 5 nm. The luminescence lifetime is prolonged up to 37 ns which corresponds to 5-6 re-maining water molecules. This indicates an exchange of about 3-4 water molecules with coordination sites of ligand molecules which implies the formation of 1:1, 1:2 and 1:3 complexes. The stability con-stants increase slightly with rising temperature which is consistent with an endothermic complexation reaction.

  • Contribution to proceedings
    International Workshop on Advanced Techniques in Actinide Spectroscopy (ATAS), 05.-07.11.2012, Dresden, Deutschland
    Wissenschaftlich-Technische Berichte HZDR-027: Helmholtz-Zentrum Dresden-Rossendorf, ISSN 2191-8708, 41
  • Poster
    International Workshop on Advanced Techniques in Actinide Spectroscopy (ATAS), 05.-07.11.2012, Dresden, Deutschland

Publ.-Id: 17491

Interfacial heat and mass tansfer models

Krepper, E.; Scheuerer, G.

The lesson 4 of the "Short Course on Multiphase Flow Modelling" deals with the simulation of mass and energy exchange between the phases based on the two fluid model approach. After the basic principles the lesson describes the simulation of subcooled boiling and the simulation of cavitation processes.

Keywords: CFD; Two fluid model; heat transfer; mass transfer; boiling; cavitation

  • Lecture (Conference)
    10th HZDR & ANSYS Short Course and Workshop "Multiphase Flow - Simulation, Experiment and Applications", 12.-14.6.2012, Dresden, Deutschland

Publ.-Id: 17490

Annihilation Lifetime Spectroscopy using Positrons from Bremsstrahlung Production

Wagner, A.; Anwand, W.; Butterling, M.; Cowan, T. E.; Fiedler, F.; Kempe, M.; Krause-Rehberg, R.

A new type of a positron annihilation lifetime spectroscopy (PALS) system has been set up at the superconducting electron accelerator ELBE [1] at Helmholtz-Zentrum Dresden-Rossendorf. In contrast to existing source-based PALS systems, the approach described here makes use of an intense photon beam from electron bremsstrahlung which converts through pair production into positrons inside the sample under study. The article focusses on the production of intense bremsstrahlung using a superconducting electron linear accelerator, the production of positrons inside the sample under study, the efficient detector setup which allows for annihilation lifetime and Doppler-broadening spectroscopy simultaneously. Selected examples of positron annihilation spectroscopy are presented.

Keywords: pulsed positron source; positron annihilation lifetime spectroscopy; age-momentum correlation; bulk sample; fluids; gases; biological samples; bremsstrahlung; superconducting LINAC

  • Book chapter
    B.N. Ganguly, G. Brauer:: Near Surface Depth Profiling of Solids by Mono-energetic Positrons, Zurich, Switzerland: TransTech Publications Ltd, 2012, 978-3-03785-524-9, 41-52
    DOI: 10.4028/


Publ.-Id: 17489

Control of fluid flow using electromagnetic body forces

Albrecht, T.; Weier, T.; Gerbeth, G.

In many engineering applications, the way natural fluid flows behave leaves some room for improvement. While geometric optimizations, such as streamlined shapes, require no additional energy input, they might not always be possible, feasible, or sufficient.

Another option is active flow control, where a suitable actuator more or less directly alters flow structures. Of the variety of such devices proposed for flow control applications, we focus on Lorentz force actuators. They consist of (permanent) magnets and electrodes, generating a body force near the wall it is attached to. The momentum added to the flow is linearly driven by an electric current.

The actuator can be applied to prevent transition from laminar to turbulent flow, a process that would otherwise lead to a rapid increase in drag. Its linear response is also advantageous when suppressing flow separation at inclined airfoils to prevent the loss of lift. The talk will cover both applications, and include numerical as well as experimental results.

Keywords: Lorentz force actuator; flow control; DNS; PIV

  • Invited lecture (Conferences)
    CE Seminar, 03.05.2012, Darmstadt, Deutschland

Publ.-Id: 17488

Dose contributions due to radiation scattered by air (skyshine) in the case of x-ray machines

Sahre, P.; Kaden, M.; Schönmuth, T.; Pawelke, J.; Naumann, B.; Reichelt, U.

Radiation transport simulations had to be done in preparation of operation of the X-ray tube ISOVOLT 320 kV/13mA in a special laboratory. At first simulation was done without shielding the roof of the laboratory, showing a dose rate maximum of more than 100 mSv/h. This dose rate results in a skyshine dose rate of at most 2 lSv/h in the surrounding of the building without shielding the roof. For similar geometries the skyshine is negligible for dose rates at the unshielded roof of less than 3 mSv/h (exclusion area).

  • Kerntechnik 77(2012)3, 191

Publ.-Id: 17487

Ion Acceleration in Ultra-Intense Laser-Matter Interactions, and Applications in Radiation Oncology

Cowan, T.

  • Invited lecture (Conferences)
    Kolloquium, 09.05.2012, Chemnitz, Deutschland

Publ.-Id: 17486

Beschleunigung der Beschleunigung: Lasergetriebene Strahlungsquellen und ihre Anwendungen

Cowan, T.

  • Invited lecture (Conferences)
    ZIH Colloquium, 26.04.2012, Dresden, Deutschland

Publ.-Id: 17485

The Helmholtz Beamlines at the European XFEL and FAIR

Cowan, T.

  • Invited lecture (Conferences)
    Joint IZEST – Helmholtz Beamlines Workshop 2012, 23.-25.04.2012, Darmstadt, Deutschland

Publ.-Id: 17484

Applications of laser-matter interaction at ultra-high intensity

Cowan, T.

  • Invited lecture (Conferences)
    Workshop on Laser-Plasma Interaction at Ultra-High Intensity ENLITE – 2nd Dresden Exchange oN Laser-plasma Interaction ThEory, 16.-20.04.2012, Dresden, Deutschland

Publ.-Id: 17483

Comparison of PIV-based methods for airfoil loads evaluation

Albrecht, T.; Del Campo, V.; Weier, T.; Gerbeth, G.

We compare the accuracy achievable with different methods of calculating time-averaged airfoil loads if the surrounding velocity field is known, e.g., from Particle Image Velocimetry. These methods require integration over a control volume enclosing the body. For separated flow around an inclined flat plate at Re=10^4, we investigate the effect of varying the control volume. Some methods yield excellent results for both lift and drag.
Preliminary results for a corresponding experiment indicate that the calculated lift coincides well with direct force measurements, whereas agreement for the drag can be considered fair.
Implementation of the methods was validated using a circular cylinder flow at Re=200.

Keywords: PIV; DNS; airfoil loads; lift; drag

  • Contribution to proceedings
    16th International Symposium on Applications of Laser Techniques to Fluid Mechanics, 09.-12.07.2012, Lisboa, Portugal
    Proceedings of the 16th International Symposium on Applications of Laser Techniques to Fluid Mechanics

Publ.-Id: 17482

Science with high-power lasers at the European XFEL

Cowan, T.

  • Invited lecture (Conferences)
    503. WE-Heraeus-Seminar Free-Electron Lasers: from Fundamentals to Applications, 10.-13.04.2012, Bad Honnef, Deutschland

Publ.-Id: 17481

Einfluss von Mikroorganismen auf die Geochemie des Bergwerkes/Wassers - Königstein

Zirnstein, I.

Mikroorganismen in ehemaligen Uran Bergwerken leben meist unter extremen Bedingungen, wie auch in der ehemaligen Mine Königstein. Dort müssen die Mikroben einem saurem pH Wert (2,7), hohen Konzentrationen an Sulfationen, Eisenionen und Uran standhalten. Nachdem die Schächte unter tage weitestgehend geflutet wurden, sind die Bedingungen noch selektierender, da Sauerstoff im Wasser fehlt und keine organische Kohlenstoffquelle vorhanden ist. Der Vergleich der Mikroorganismen in der Grube vor der Flutung und nachher zeigt, dass sich die veränderten Bedingungen auf die Biodiversität auswirken. Vor der Flutung waren in den Schächten neben Bakterien auch zahlreiche Eukaryonten vorhanden. Diese konnten bisher im Flutungswasser nicht nachgewiesen werden.

Keywords: biofilms; uranium mine; biodiversity

  • Lecture (others)
    Fortschritt der Forschungsarbeiten, 23.03.2012, Chemnitz, Deutschland

Publ.-Id: 17480

Helmholtz Beamline at European XFEL Status & Next Steps

Cowan, T.

  • Lecture (Conference)
    Peak Brightness Collaboration @ XFEL Users Meeting, 26.01.2012, Hamburg, Deutschland

Publ.-Id: 17479

Dresden projects in Ultra-High- Intensity physics with PW lasers

Cowan, T.

  • Invited lecture (Conferences)
    Science with PW-class lasers, 23.-24.01.2012, Paris, Frankreich

Publ.-Id: 17478

High-energy, ceramic-disk Yb:LuAG laser amplifier

Siebold, M.; Loeser, M.; Roeser, F.; Seltmann, M.; Harzendorf, G.; Tsybin, I.; Linke, S.; Banerjee, S.; Mason, P.; Phillips, J.; Ertel, K.; Collier, J.; Schramm, U.

We report the first short-pulse amplification results to several hundred millijoule energies in ceramic Yb:LuAG. We have demonstrated ns-pulse output from a diode-pumped Yb:LuAG amplifier at an energy of 550 mJ and an optical-to-optical efficiency of 27%. In cavity dumped operation of a nanosecond oscillator we obtained 1mJ at up to 100 Hz repetition rate. A gain bandwidth of 5.4 nm was achieved at room temperature by measuring the small-signal single-pass gain. Furthermore, we compared our results with Yb:YAG within the same amplifier system.

Keywords: Laser amplifiers; Lasers, ytterbium; Lasers, diode-pumped

Publ.-Id: 17477

Phase transfer of agglomerated nanoparticles: deagglomeration by adsorbing grafted molecules and colloidal stability in polymer solutions

Rudolph, M.; Peuker, U. A.

A study is presented, where agglomerated magnetite nanoparticles with a crystallite size of 15 nm are transferred from water to an immiscible organicphase and tend to deagglomerate under certain conditions using different types of chemically adsorbing fatty acid. It is shown that the longer fatty acids lead to more stable dispersions and for the longest fatty acids, the functionality of the molecules defines stability with best results for ricinoleic acid. The disjoining force as a function of the brush layer thickness and adsorption density is calculated with a physical modelapplying the well-established Alexander de Gennes theory. We further investigate the colloidal stability of the transferred and stabilized magnetite nanocrystals in polymer solutions of destabilizing PMMA and stabilizing PVB. A DLVO-like theory presents the governing attractive and repulsive interactions for the case of destabilizing non-adsorbing polymers. The theory can be used to explain the influencing parameters in a mixture of sterically stabilized nanoparticles in an organic solvent based solutionofpolymercoils.Finally,by spray drying, we produce polymer–nanoparticle composite microparticles. Based on BET, laser diffraction and backscatter electron SEM measurements, we draw conclusions on the nanoparticle distribution within the composite in correlation with the stability investigations.

Keywords: Disjoining force; Peptization; Resuspension; Depletion; Fatty acids; Polymer; Solvents; Magnetite; Steric interactions; Solubility distance; DLVO; Non-DLVO; Nanocomposites

Publ.-Id: 17476

THz beamline at FLASH

Stojanovice, N.; Tavella, F.; Klopf, M.; Schade, U.; Seidel, W.; Yurkov, M. V.; Saldin, E.; Schneidmiller, E.; Geloni, G.; Gensch, M.

Transports THz pulses to XUV beamline for pump-probe experiments

  • Poster
    EuropeanXFEL user meeting, 27.-29.01.2010, DESY, Hamburg, Deutschland

Publ.-Id: 17475

The THz user facility FELBE at the radiation source ELBE of Helmholtz-Zentrum Dresden-Rossendorf

Seidel, W.; Helm, M.; Michel, P.; Schneider, C.; Schneider, H.; Schurig, R.; Stehr, D.; Wagner, M.; Winnerl, S.

The radiation source ELBE at the Helmholtz-Zentrum Dresden-Rossendorf (former Forschungszentrum Dresden-Rossendorf (FZD)) is built around a superconducting electron linear accelerator, constructed to produce quasi cw electron beams up to 1 mA beam current at 12 - 34 MeV. The electron beam is used to generate various kinds of secondary radiation, mainly to drive the two free-electron lasers U27 and U100 in the infrared region (4-250 μm). Starting in summer 2005 user beam time is offered to external users in the frame of the EC funded “Integrating Activity on Synchrotron and Free Electron Laser Science” (FELBE project). FELBE is an acronym for the free-electron laser (FEL) at the Electron Linear accelerator with high Brilliance and Low Emittance (ELBE). Twice a year users are invited to submit proposals for experiments at ELBE. For the period January - June 2012 the deadline will be November 14th, 2011. Access is free of charge for all non- proprietary research. Proposals are evaluated by the scientific advisory committee of ELBE. Based on their recommendations the final decision and allocation of beam time will be made by an local panel headed by the Scientific Director of the HZDR.
The IR light from the two FELs is transported to several laboratories in the same building and to the adjacent building (through a 27 m long tunnel) of the High Magnetic Field Laboratory (HLD) as well, where the experimental setups are up to 70 m away from the FELs. Here, self-designed magnets for fields up to 90 T have successfully been tested and first experiments with IR beams have been carried out.

  • Poster
    WIRMS 2011 - 6th International Workshop on Infrared Spectroscopy and Microscopy with Accelerator-Based Sources, 04.-08.09.2011, Trieste, Italy

Publ.-Id: 17474

PIDID Collaboration - a multi-institutional approach to improve infrastructure for time resolved experiments at THz and X-ray FEL facilities

Gensch, M.; Seidel, W.; Stojanovic, N.; Laarmann, T.; Eng, L. M.; Winnerl, S.; Schneider, H.; Helm, M.; Hübers, H. W.; Heberle, J.

The broad spectral range spanning from THz to X-rays combined with pulse durations from the femtosecond (fs) to nanosecond (ps) regime provided by THz and X-ray FELs are in principal optimally suited to investigate the rich and complex physics occurring in photoinitiated processes in materials. Unfortunately, these experiments require often specific conditions (e.g. high pressure, cryogenic temperatures, nanoscale resolution or ultra high vacuum) that complicate the alignment and the diagnostic of temporal and spatial overlap and lead to unacceptably long preparation times. In order to overcome this problematic, scientific groups working in the field teamed up with experts from different 4th generation photon facilities to develop more suitable instrumentation and infrastructure. Concepts and first developments will be presented.

  • Poster
    33rd International Free Electron Laser Conference 2011, 22.-26.08.2011, Shanghai, China

Publ.-Id: 17473

TELBE the coherent THz facility at ELBE: Enroute to naturally synchronized THz pump THz probe experiments beyond the 100 microjoule pulse energy limit

Gensch, M.; Seidel, W.; Stojanovic, N.; Hauser, J.; Lehnert, U.; Schneider, H.; Helm, M.; Michel, P.

At the ELBE accelerator at the HZDR a new electron beamline, providing for femtosecond electron bunches with nC bunch charges and repetition rates in the 1 – 200 kHz regime is currently constructed. The 40 MeV electrons will be used in photon-electron interaction experiments with TW and PW class laser and for the generation of broad band and narrow bandwidth coherent THz pulses in the frequency range between 0.1 THz – 3 THz. Similar to previous work at FLASH the natural synchronization between light pulses generated by the same electron bunch shall be employed for fully synchronized experiments between narrow and broad band THz pulses as well as for novel electron bunch diagnostic (see also poster WEAP13). Pulse energies are expected to exceed the 100 μJ limit at scalable repetition rates between 1 and 200 kHz. The current status of the project and planned experiments are presented.

  • Poster
    33rd International Free Electron Laser Conference 2011, 22.-26.08.2011, Shanghai, China

Publ.-Id: 17472

Entwicklung einer Synthesestrategie für die Radiofluorierung eines Eph-Rezeptor-Inhibitors für die Tumordiagnostik mittels PET

Kinski, E.

kein Abstract verfügbar

  • Diploma thesis
    Hochschule Zittau/Görlitz, 2012
    85 Seiten

Publ.-Id: 17471

Entwicklung von Radiotracern basierend auf EphB4-Inhibitoren und deren Vorstufen zur Radiomarkierung mit Kohlenstoff-11 und Fluor-18

Ebert, K.

kein Abstract verfügbar

  • Diploma thesis
    Hochschule Zittau/Görlitz, 2012
    83 Seiten

Publ.-Id: 17470

Status of the Fritz Haber Institute THz FEL

Schöllkopf, W.; Gewinner, S.; Erlebach, W.; Junkes, H.; Liedke, A.; von Helden, G.; Zhang, W.; Meijer, G.; Bluem, H.; Christina, V.; Cole, M.; Ditta, J.; Dowell, D.; Jordan, K.; Lange, R.; Park, J.; Rathke, J.; Schultheiss, T.; Todd, A.; Young, L.; Lehnert, U.; Michel, P.; Seidel, W.; Wünsch, R.; Gottschalk, S.

The IR and THz FEL at the Fritz Haber Institute (FHI) in Berlin is designed to deliver radiation from 4 to 500 microns. A single-plane-focusing undulator combined with a 5.4 m long cavity is used in the mid-IR (< 50 micron), while a two-plane-focusing undulator in combination with a 7.2 m long cavity with a 1-D waveguide for the optical mode, will be used for the far-IR. A key aspect of the accelerator performance is low longitudinal emittance, < 50 keV-psec, at 200 pC bunch charge and 50 MeV, from a gridded thermionic electron source. We utilize twin accelerating structures separated by a chicane to deliver the required performance over the 15 - 50 MeV energy range. "First Light" is targeted for the centennial of the FHI in October 2011. Installation and commissioning progress to date is described.

  • Poster
    33rd International Free Electron Laser Conference 2011, 22.-26.08.2011, Shanghai, China
  • Open Access Logo Contribution to proceedings
    33rd International Free Electron Laser Conference 2011, 22.-26.08.2011, Shanghai, China

Publ.-Id: 17469

First Lasing of the IR FEL at the Fritz-Haber-Institut Berlin

Schöllkopf, W.; Erlebach, W.; Gewinner, S.; Junkers, H.; Liedke, A.; Meijer, G.; von Helden, G.; Zhang, W.; Jordan, K.; Rathke, J.; Murray, A.; Todd, M.; Young, L. M.; Bluem, H.; Dowell, D.; Lange, R.; Park, J.; Davidsaver, M.; Lehnert, U.; Michel, P.; Seidel, W.; Wuensch, R.; Loos, H.; Gottschalk, S. C.

An IR and THz FEL with a design wavelength range from 4 to 500 µm has been commissioned at the Fritz-Haber-Institut (FHI) in Berlin, Germany, for applications in, i.a., molecular and cluster spectroscopy as well as surface science. The linac comprises two S-band standingwave copper structures. The first one operates at near fixed field to accelerate the electrons to 20 MeV, while the second one is designed to accelerate (or decelerate) to any final energy between 15 and 50 MeV. A key aspect of the system is low longitudinal emittance, < 50 keVpsec, at more than 200 pC bunch charge with a max. micro pulse rep. rate of 1 GHz. The up to 15 µs long macro pulses come at a rate of up to 20 Hz. The electrons are steered through either one of two FELs. A single-plane-focusing, 40 mm period hybrid magnet undulator combined with a 5.4 m long cavity has been commissioned for the mid-IR (< 50 µm). In addition, a two-plane- focusing undulator in combination with a 7.2 m long cavity with a 1-d waveguide for the optical mode is planned for the far-IR. In February 2012 we observed 'first lasing' at 28 MeV
and a wavelength of 18 µm. We will present first results characterizing the system.

  • Poster
    34th International Free Electron Laser Conference 2012, 26.-31.08.2012, Nara, Japan
  • Open Access Logo Contribution to proceedings
    34th International Free Electron Laser Conference 2012, 26.-31.08.2012, Nara, Japan

Publ.-Id: 17468

Characterization of H-plasma treated ZnO crystals by positron annihilation and atomic force microscopy

Cizek, J.; Prochazka, I.; Kuriplach, J.; Anwand, W.; Brauer, G.; Cowan, T. E.; Grambole, D.; Schmidt, H.; Skuropa, W.

Nominally undoped, hydrothermally grown ZnO single crystals have been investigated before and after exposure to remote H-plasma. Defect characterization has been made by two complementary techniques of positron annihilation: positron lifetime spectroscopy and coincidence Doppler broadening. The high-momentum parts of the of the annihilation photon momentum distribution have been calculated from first principles in order to assist in defect identification. The positron annihilation results are supplemented by Atomic Force Microscopy for characterization of the crystal surface. It was found that virgin ZnO crystal contains Zn-vacancies associated with hydrogen. H-plasma treatment causes a significant reduction in concentration of these complexes. Physical mechanism of this effect is discussed in the paper.

Keywords: Zinc oxide; hydrogen; positron annihilation; atomic force microscopy

  • Book chapter
    B.N. Ganguly, G. Brauer: Near Surface Depth Profiling by Mono-energetic Positrons, Switzerland: Trans Tech Publisher, 2012, 978-3-03785-524-9, 113-125
    DOI: 10.4028/


Publ.-Id: 17467

Structural studies of nanocrystalline thin Pd films electrochemically doped with hydrogen

Cizek, J.; Vlcek, M.; Lukac, F.; Vlach, M.; Prochazka, I.; Brauer, G.; Anwand, W.; Muecklich, A.; Wagner, S.; Uchida, H.; Pundt, A.

Hydrogen absorption in Pd causes a significant volume expansion. In free-standing bulk Pd, the hydrogen-induced volume expansion is isotropic. However, the situation becomes more complicated in thin Pd films. Contrary to bulk samples, thin films are clamped to an elastically stiff substrate, which prevents in-plane expansion. Hence, the volume expansion of a thin film is strongly anisotropic because it expands in the out-of-plane direction only. Internal stresses introduced by absorbed hydrogen may become so high that detachment of a film from the substrate is energetically favorable and buckles of various morphologies are formed. In the present work, we studied hydrogen-induced buckling in a nanocrystalline thin Pd film deposited on a sapphire substrate. Slow positron implantation spectroscopy (SPIS) was employed as a principal tool for the characterization of defects and investigation of defect interactions with hydrogen. SPIS studies were combined with X-ray diffraction and direct observations of buckling by light microscopy. It was found that buckling of thin Pd film occurs at hydrogen concentrations xH > 0.1 and is accompanied by a strong increase of dislocation density.

Keywords: palladium; hydrogen; thin films; positron annihilation

  • Book chapter
    B.N. Ganguly, G. Brauer: Near Surface Depth Profiling by Mono-energetic Positrons, Switzerland: Trans Tech Publisher, 2012, 978-3-03785-524-9, 137-147
    DOI: 10.4028/


Publ.-Id: 17466

Structural characterization of lead sheets for organ pipes by Positron Annihilation Spectroscopy

Butterling, M.; Anwand, W.; Cowan, T. E.; Skorupa, W.; Wagner, A.; Häberle, J.; Jungmann, M.; Krille, A.; Krause-Rehberg, R.; Eule, A. C.

An important issue when restaurating organ pipes made from lead alloys is the engineering of such material by mechanical hammering to increase the density. Microscopic effects of work-hardening on the surface near layers of lead sheets were investigated by depth resolving Doppler Broadening Spectroscopy measurements using the slow positron beam SPONSOR [1] of the Helmholtz-Zentrum Dresden-Rossendorf. The influence of small differences in the chemical composition of the samples is also discussed.

Keywords: Positron Annihilation Spectroscopy; Defect Characterization

  • Lecture (Conference)
    76. Jahrestagung der DPG und DPG-Frühjahrstagung, 25.-30.03.2012, Berlin, Deutschland

Publ.-Id: 17465

Defect Behaviour in Yttria-Stabilised Zirconia Nanomaterials Studied by Positron Annihilation Techniques

Prochazka, I.; Cizek, J.; Melikhova, O.; Kuriplach, J.; Anwand, W.; Brauer, G.; Konstantinova, T. E.; Danilenko, I. A.; Yashchishyn, I. A.

Recent experimental and theoretical investigations on a variety of yttria-stabilised zirconia (YSZ) nanomaterials are reviewed. The investigations were conducted within the frame of a collaboration of three institutions: (i) Charles University in Prague (CZ), (ii) Helmholtz Centre Dresden-Rossendorf (GER) and (iii) Nat. Academy of Science in Donetsk (UA), Materials studied involved pressure-compacted nanopowders of binary and ternary (with Cr2O3 additive) YSZ and YSZ ceramics obtained by sintering the nanopowders. The nanopowders were prepared by the co-precipitation technique. Positron annihilation spectroscopy including the conventional positron lifetime (LT) and coincidence Doppler broadening (CDB) techniques was employed as the main experimental tool. Slow positron implantation spectroscopy (SPIS) was used in investigation of commercial YSZ single crystals for reference purposes. Extended state-of-art theoretical ab-initio calculations of positron response in the ZrO2 lattice were carried out for various vacancy-like defect configurations. It was suggested by these calculations that none of the oxygen-vacancy related defects are capable to trap positrons. On the other hand, zirconium vacancy was demonstrated by the calculations to be a deep positron trap, even in case that a hydrogen atom is adjointed to the vacancy. The measured positron LT data clearly indicated that positrons annihilate in nanopowders predominantly from trapped states at defects of two kinds: (a) the vacancy-like misfit defects concentrated in layers along the grain boundaries and characterised with lifetimes of ≈ 0.180 ns, and (b) the larger defects of open volume comparable to a few vacancy cluster which are situated at intersections of three (or more) grain boundaries (characteristic lifetimes of ≈ 0.380 ns. Intensity ratio of LT components corresponding to these two kinds of defects was found to be correlated with the mean particle size. This correlation reconfirms the above interpretation of LT components and, moreover, the measured ratios could be used to estimate changes of the mean particle size with chromia content or sintering temperature. It was shown in this way that chromia addition to the YSZ nanopowder leads to a smaller particle size compared to the binary YSZ. Similarly, grain growth during sintering could be monitored via this intensity ratio. A portion of ≈ 10 % of positrons was found to form positronium (Ps) in binary YSZ compacted nanopowders. The observed ortho-Ps lifetimes correspond to Ps pick-off annihilation in cavities of ≈ 3 nm size which may be expected to occur between the primary nanoparticles. On the other hand, an addition of chromia at concentration as low as 0.3 mol.% appeared to be sufficient to suppress Ps formation below detection limit. Similarly, Ps formation could not be detected in binary YSZ sintered for 1 hour at a temperature of 1000 °C or higher. The former effect indicates an enhanced concentration of Cr cations at the particle surfaces, while the latter one appears due to a decrease of cavity concentration induced by sintering. The measured CDB data supported the idea that vacancy-like trapping centres are similar to zirconium vacancies and gave further evidence of a strong segregation of Cr segregation at particle interfaces.
SPIS was further involved in a trial experiment on binary YSZ nanopowders and sintered ceramics. This experiment clearly demonstrated that SPIS may reveal a valuable information about changes of depth profiles of microstructure during sintering,, e.g. a sintering induced diffusion of defects from sample interior to its surface.

Keywords: Yttria-stabilised zirconia; Chromia; Pressure-compacted nanopowders; Sintered ceramics; Positron lifetimes; Coincidence Doppler broadening; Slow positron implantation spectroscopy; Theoretical ab-initio calculations of positron parameters

  • Book chapter
    B.N. Ganguly, G. Brauer: Near Surface Depth Profiling by Mono-energetic Positrons, Switzerland: Trans Tech Publisher, 2012, 978-3-03785-524-9, 181-199
    DOI: 10.4028/


Publ.-Id: 17464

Investigations of HAVAR® Alloy using Positrons

May-Tal Beck, S.; Anwand, W.; Wagner, W.; Brauer, G.; Beck, A.; Ocherashvili, A.; Hen, O.; Haroush, S.; Eisen, Y.; Moreno, D.

A study of irradiation-induced damage in HAVAR® foils was initiated in order to extract the highest proton dose the foils can sustain. The lattice structure of HAVAR® foils in different metallurgic conditions is presented, as well as visible internal structure, measured by Transmission Electron Microscopy (TEM). Positron Annihilation Spectroscopy (PAS) techniques were used to investigate these foils, and another foil that had been irradiated to the maximal proton dose limit, set by the manufacturer, of 1 mAh. PAS techniques included Doppler Broadening (DB) measurement in the SPONSOR beam and Lifetime (LT) measurements, both carried at Helmholtz Zentrum Dresden-Rossendorf (HZDR). Both positron spectroscopy methods show clear differences between the investigated foils, with distinguished characteristics for annealed, cold-rolled and irradiated foils. The advantages of using a slow positron beam to study thin foils and defect profiles, over a table-top LT spectrometer, are discussed and demonstrated by the HAVAR® measurements.

Keywords: positron annihilation; lifetime spectroscopy; Doppler broadening; slow positron beam; HAVAR® alloy; irradiation damage

  • Book chapter
    B.N. Ganguly, G. Brauer: Near Surface Depth Profiling by Mono-energetic Positrons, Switzerland: Trans Tech Publisher, 2012, 978-3-03785-524-9, 95-112
    DOI: 10.4028/


Publ.-Id: 17463

Application of Positron Annihilation Spectroscopy to Irradiated Fe-Cr Alloys

Butterling, M.; Bergner, F.; Heintze, C.; Anwand, W.; Ulbricht, A.

The effect of Cr on the microstructure of neutron-irradiated Fe-Cr alloys is not yet known in detail. Available experimental results indicate that the addition of Cr to Fe or steels significantly influences the behavior of Fe-Cr alloys or ferritic/ martensitic high-Cr steels with regard to neutron irradiation. Neutron irradiation induced damage at its early stage was simulated by ion implantation. Positron Annihilation Spectroscopy, known as a very sensitive method for revealing smallest open-volume defects with lowest concentrations, was applied to identify irradiation-induced defects depending on the Cr-content in Fe-Cr alloys. Different irradiation scenarios were used to investigate the influences of irradiation step by step.

Keywords: Fe-Cr alloys; Positron Annihilation Spectroscopy; ion implantation induced damage

  • Book chapter
    B.N. Ganguly, G. Brauer: Near Surface Depth Profiling by Mono-energetic Positrons, Switzerland: TransTech Publishers, 2012, 978-3-03785-524-9, 165-179
    DOI: 10.4028/


Publ.-Id: 17462

Design and Construction of a Slow Positron Beam for Solid and Surface Investigations

Anwand, W.; Brauer, G.; Butterling, M.; Kissener, H.-R.; Wagner, A.

On the basis of the design and construction of the slow positron beam “SPONSOR” at the Helmholtz-Centre Dresden-Rossendorf an example is given how to build-up a simple slow positron beam for solid surface investigations within a short time and without high financial costs. The system uses a 22Na source and consists of three main parts: (1) the source chamber with a thin film tungsten moderator used in transmission, and a pre-accelerator stage, (2) the vacuum system with magnetic transport, a bent tube for energy selection and an accelerator, (3) the sample chamber with a sample holder, Ge detectors and (4) facilities for remote control and data acquisition. These parts are described in detail. The paper is preferentially addressed to beginners in the field of slow positron beam techniques and other readers being generally interested in positron annihilation spectroscopy.

Keywords: slow positron beam; design and construction

  • Book chapter
    B.N. Ganguly, G. Brauer: Near Surface Depth Profiling by Mono-energetic Positrons, Switzerland: Trans Tech Publisher, 2012, 978-3-03785-524-9, 25-40
    DOI: 10.4028/


Publ.-Id: 17461

Flash lamp annealing of W foils and meshes

Anwand, W.; Butterling, M.; Johnson, J.; Wagner, A.

Tungsten is often used as a positron moderator in mono-energetic positron beams [1] with 22Na positron sources. Therefore, mono-crystalline W foils with a thickness of about 2 µm are commonly used. The efficiency of such tungsten moderators strongly depends on the heat treatment of the tungsten foils. Currently, the annealing of such thin foils is mostly done at temperatures of about 2000 oC under vacuum conditions with a considerable difficulty. For this reason, a new method was sought to quickly anneal W foils to produce manageable, low-cost moderators with a high efficiency suitable for mono-energetic positron beams.
Flash lamp annealing (FLA) offers a chance for the optimization of the moderator properties. With FLA, the surface of a W foil can be heated above the melting point (3422ºC) in 1 to 3 ms without melting the whole volume. The heat treatment was carried out in an Ar flow. In this way, a surface cleaning and a considerably longer positron diffusion length could be reached.
Conventional poly-crystalline W foils with a thickness of 9 µm + 25% and heat treated by FLA were characterized by Auger electron spectroscopy, scanning electron microscopy and slow positron implantation spectroscopy and then tested as positron moderators. First promising results obtained with these W foils will be presented and it will be shown that this technique is applicable to tungsten meshes too.

[1] P.G. Coleman, Positron Beams and their applications, World Scientific Publishing, Singapore, 2000

Keywords: mono-energetic positron beam; W moderator; flash lamp annealing

  • Lecture (Conference)
    Treffen deutscher Positronengruppen, 28.02.-01.03.2012, Dresden, Deutschland

Publ.-Id: 17460

ELI - Extreme Light Infrastructure Science and Technology with Ultra-Intense Lasers. Whitebook

Aleonard, M. M.; Altarelli, M.; Antici, P.; Apolonskiy, A.; Audebert, P.; Bartnik, A.; Barty, C. P. J.; Bernstein, A.; Biegert, J.; Böni, P.; Booth, N.; Borghesi, M.; Bote, D.; Bulanov, S. V.; Butkus, R.; Cardoso, L.; Chambaret, J. P.; Charambilidis, D.; Cheriaux, G.; Clarke, R.; Collier, J.; Cramer, L.; Czitrovsky, A.; D’Humières, E.; Di Piazza, A.; Dietz, B.; Ditmire, T.; Dombi, P.; Dorobantu, A.; Dyer, G.; Ernstorfer, R.; Ertel, K.; Esarey, E.; Esirkepov, T. Z.; Esposito, A.; Fajardo, M.; Fedotov, A.; Fenic, C.; Fernandez, F.; Ferrari, A.; Földes, I. D.; Frederickson, C.; Fuchs, J.; Fülöp, J. A.; Fülöp, Z.; Galimberti, M.; Gaul, E.; Gies, H.; Giulietti, A.; Giulietti, D.; Gizzi, L.; Gliksohn, F.; Goulielmakis, E.; Grigsby, W.; Gross, M.; Grüner, F.; Habs, D.; Hajdu, J.; Hajima, R.; Harman, Z.; Hatsagortsian, K. Z.; Hebling, J.; Kalashnikov, M. P.; Kalpouzos, C.; Karsch, S.; Keitel, C. H.; Kiefer, D.; Kienberger, R.; Kling, M.; Kneip, S.; Korn, G.; Köster, U.; Kovács, M.; Kozlova, M.; Kraft, G.; Kraft, S.; Krausz, F.; Lancaster, K. L.; Le Blanc, C.; Le Garrec, B.; Leemans, W.; Lenner, M.; Limpouch, J.; Lippenyi, T.; Lopes, N. C.; Lopez-Martens, R.; Ma, W.; Major, Z.; Margarone, D.; Markey, K.; Marklund, M.; Marti, M.; Martinez, M.; Mason, P.; Mathieu, F.; Metzger, T.; Mocek, T.; Molls, M.; Mourou, G.; Moustaizis, S. D.; Müller, C.; Murphy, C. D.; Musgrave, I.; Narozhny, N. B.; Naumova, N.; Neely, D.; Negoita, F.; Nickles, P. V.; Nisoli, M.; Oliva, E.; Osvay, K.; Paillard, J. L.; Pepler, D.; Pegoraro, F.; Pervak, V.; Petrillo, V.; Pfeiffer, F.; Pietralla, N.; Piskarksas, A.; Ploumistakis, I.; Poleto, L.; Priebe, G.; Rodriguez Tajes, C.; Rohlena, K.; Roth, M.; Ruhl, H.; Ruiz, C.; Rus, B.; Ruth, R.; Růžička, V.; Sandner, W.; Sansone, G.; Savran, D.; Schreiber, J.; Schützhold, R.; Serafini, L.; Silva, L.; de Silvestri, S.; Sonnabend, K.; Stehle, C.; Symes, D. R.; Szabo, G.; Tajima, T.; Tempea, G.; Thirolf, P. G.; Thomas, A. G. R.; Tikhonchuk, V.; Tsakiris, G. D.; Tsohantjis, I.; Tzallas, P.; Urruti, E.; Ursescu, D.; Varjú, K.; Veisz, L.; Vrakking, M.; Weidenmüller, H. A.; White, W.; Wilkens, J. J.; Will, I.; Winstone, T.; Wittman, T.; Woolsey, N.; Wormser, G.; Yan, X. Q.; Zamfir, N. V.; Zepf, M.

The ELI Whitebook contains the description of the science, the technology basis and the implementation of the new international scientific infrastructure Extreme Light Infrastructure (ELI)

Keywords: ultra-intense lasers; high-power lasers; ELI

  • Book (Authorship)
    Berlin: THOSS Media GmbH, Editors: G.A. Mourou, G. Korn, W. Sandner, 2011
    535 Seiten

Publ.-Id: 17459

A new experiment on the 2H(α,γ)6Li reaction

Anders, M.

The 2H(α,γ)6Li cross section has been measured by in-beam gamma-spectrometry at the deep underground 400 keV LUNA accelerator in Italy's Gran Sasso laboratory. An α-beam of 280-400 keV energy was incident on a windowless deuterium gas target, and the γ-rays from the reaction were detected in a large high-purity germanium detector. Due to elastically scattered deuterons, there is a low but not negligible parasitic neutron production of the order of 10 neutrons per second. These neutrons give rise to a significant background in the germanium detector. In addition to the underground in-beam experiment, also studies using americium-beryllium and deuterium-deuterium neutron sources and Monte Carlo simulations have been performed. The analysis of signal and background is described in detail.

Keywords: Gran Sasso; Nuclear Astrophysics; LUNA; Lithium; Big Bang; Nucleosynthesis

  • Poster
    XII International Symposium on Nuclei in the Cosmos, 07.08.2012, Cairns, Australia
  • Contribution to proceedings
    XII International Symposium on Nuclei in the Cosmos, 18.11.2012, Cairns, Australia
    PoS(NIC XII)137

Publ.-Id: 17458

Commissioning of the Fritz Haber Institute MID-IR FEL

Todd, A. M. M.; Bluem, H.; Ditta, J.; Dowell, D.; Jordan, K.; Lange, R.; Loos, H.; Park, J.; Rathke, J.; Young, L.; Gewinner, S.; Erlebach, W.; Junkes, H.; Liedke, A.; Meijer, G.; von Helden, G.; Schöllkopf, W.; Zhang, W.; Lehnert, U.; Michel, P.; Seidel, W.; Wuensch, R.

The free electron laser (FEL) at the Fritz Haber Institute (FHI) in Berlin is designed to deliver radiation from 4 to 400 microns. A single-plane-focusing undulator combined with a 5.4 m long optical cavity is used for the generation of mid-infrared (MIR) radiation up to 50 microns. A two-plane-focusing undulator, in combination with a 7.2 m long cavity with a 1-D waveguide for the optical mode, is planned for the far-infrared (FIR). Beam was delivered to the MIR beam dump in October 2011 and first light at 18 microns was achieved on Valentine’s Day, 2012. We describe progress to date and plans to complete the
commissioning of the MIR beamline and the installation of the FIR beamline.

  • Poster
    International Particle Accelarator Conference 2012 (IPAC2012), 20.-25.05.2012, New Orleans, USA
  • Open Access Logo Contribution to proceedings
    International Particle Accelarator Conference 2012 (IPAC2012), 20.-25.05.2012, New Orleans, USA

Publ.-Id: 17457

A comparative glance into the HAVAR alloy by PAS and TEM methods

May-Tal Beck, S.; Anwand, W.; Wagner, A.; Haroush, S.; Eisen, Y.; Beck, A.; Ocherashvili, A.; Hen, O.; Moreno, D.

HAVAR foils are used in the medical industry as a window material for the production of 18FDG for PET scans. First comparative measurements of HAVAR foils, 25 μm thick, are presented. Three samples were measured: cold rolled (CR), annealed (AN), and proton irradiated (IR). These HAVAR foils were studied by means of Slow Positron Implantation Spectroscopy (SPIS), Positron Annihilation Lifetime spectroscopy (PAL), Transmission Electron Microscopy (TEM) and X-Ray Diffraction (XRD). TEM and XRD results show that HAVAR has a fcc structure with a small amount of dislocations in the AN sample and a high density of dislocation nets in the CR sample. The positron diffusion lengths, extracted from the SPIS measurements, are ~8 nm and ~66 nm in the CR and AN samples, respectively, in agreement with TEM observations. The results of PAL measurements show significant differences between positron mean lifetimes in the three samples. Differences of ~50 ps and ~70 ps were measured between the mean lifetime in the AN sample and these in the CR and IR samples, respectively. GEANT4 simulations were used for the first time in PAL analysis. The simulation method and its benchmarking against previous measurements are described. Lifetime results obtained using conventional PAL analysis and GEANT4 based analysis are consistent within uncertainties for both the HAVAR and a Si reference sample.

Keywords: HAVAR foil; intrinsic and irradiation induced defects; positron annihilation spectroscopy; transmission electron microscopy

  • Contribution to proceedings
    Positron Studies of Defects 2011 (PSD-11), 28.08.-02.09.2011, Delft, Netherlands
    Physics Procedia 35: ELSEVIER, 63-68

Publ.-Id: 17456

Isolierung und Charakterisierung von Zellwandbestandteilen Gram-positiver Mikroorganismen

Drechsel, N.

Die Untersuchung von Metallen in Biosystemen stellt einen wichtigen Faktor im Verständnis von Mobilität und Stabilität, von z.B. Schwermetallen, in der Umwelt dar. Um diese Prozesse zu verstehen, bzw. um Aussagen zu verschiedenen Reaktionen treffen zu können, ist es notwendig die genauen Mechanismen zu bestimmen. Untersuchungen zeigten bei den hier verwendeten mikrobiellen Haldenisolaten sehr hohe Metallbindungskapazitäten. Da bisher größtenteils nur ganze Zellsysteme untersucht wurden, soll hier der Fokus auf die Einzelkomponenten von Gram-positiven Mikroorganismen gelegt werden. Dazu ist es notwendig diese zu isolieren und zu charakterisieren bevor Aussagen zu Bindungsereignissen und Wechselwirkungs-mechanismen getroffen werden können. In diesen Ausführungen sollen die gram-positiven Stämme JG-B53 und Lysinibacillus sphaericus JG-A12 in einem Batch-Verfahren kultiviert werden. Anschließend werden die Zellen geerntet und deren Zellwandbestandteile durch verschiedene Verfahren gewonnen. Zu den Extraktionsverfahren zählen die mechanisch-biochemische Gewinnung und die Lösungsmittelextraktion. Die zu isolierenden Komponenten sind vor allem Lipide und Hüllproteine, die auch als S-Layer bezeichnet werden. Die extrahierten Bestandteile werden mittels biochemischer, chemischer und strukturanalytischer Analysemethoden charakterisiert.

Keywords: S-Layer; Lipide; Biosorption; Bakterien; Biosysteme; Isolierung

  • Study thesis
    Hochschule Mittweida, 2012
    75 Seiten

Publ.-Id: 17455

Characterization of quenched-in vacancies in Fe–Al alloys

Cizek, J.; Lukac, F.; Prochazka, I.; Kuzel, R.; Jiraskova, Y.; Janickovic, D.; Anwand, W.; Brauer, G.

Physical and mechanical properties of Fe–Al alloys are strongly influenced by atomic ordering and point defects. In the present work positron lifetime (LT) measurements combined with slow positron implantation spectroscopy (SPIS) were employed for an investigation of quenched-in vacancies in Fe–Al alloys with the Al content ranging from 18 to 49 at.%. The interpretation of positron annihilation data was performed using ab-initio theoretical calculations of positron parameters. Quenched-in defects were identified as Fe-vacancies. It was found that the lifetime of positrons trapped at quenched-in defects increases with increasing Al content due to an increasing number of Al atoms surrounding the Fe vacancies. The concentration of quenched-in vacancies strongly increases with increasing Al content from 105 in Fe82Al18 (i.e. the alloy with the lowest Al content studied) up to 101 in Fe51Al49 (i.e. the alloy with the highest Al content studied in this work).

Keywords: Fe–Al alloys; vacancies; positron annihilation

Publ.-Id: 17454

Gestengesteuerte visuelle Datenanalyse einer Laser-Plasma-Simulation

Schneider, B.

Der ständige Zuwachs an Rechenleistung und die Entwicklung größerer Speichermedien fördert eine nie dagewesene Datenflut zu Tage. In Bereichen wie Astronomie, Biologie, Medizin, Physik und Wirtschaft werden Datenmengen im Petabyte-Bereich und darüber hinaus gemessen, beobachtet und berechnet.

Ein konkretes Beispiel liefert der am Institut für Strahlenphysik entwickelte PIConGPU-Code, welcher zur Simulation von Laser-Plasma-Kollisionen eingesetzt wird.

Zur effizienten Auswertung dieser Datenmengen bedarf es neuer Methoden und Werkzeuge, die eine intuitive und flexible Analyse ermöglichen. Ein natürliches Interface und eine immersive Darstellung der Visualisierung nutzt die kognitiven Fähigkeiten des Anwenders und erlaubt ihm sein Expertenwissen optimal einzusetzen.

Deshalb wurde in dieser Arbeit in Kooperation zwischen dem Helmholtz-Zentrum Dresden-Rossendorf und der TU Dresden ein Visualisierungssystem entwickelt, welches die Vorteile der visuellen Datenanalyse mit einem intuitiven Gesteninterface verbindet. Die Microsoft Kinect dient dabei als Trackinggerät für die Gestenerkennung. Einen wichtigen Beitrag zur Steigerung der Immersion leistet neben einer großen Displayfläche das implementierte Stereo-Rendering.

Keywords: Natürliche Interaktion; Wissenschaftliche Visualisierung; Gesten; Kinect; Powerwall; stereoskopisch; Datenanalyse

  • Study thesis
    TU Dresden, 2012
    70 Seiten

Publ.-Id: 17453

First lasing of the IR FEL at the Fritz-Haber-Institut

Schöllkopf, W.; Gewinner, S.; Zhang, W.; Junkes, H.; Erlebach, W.; Liedke, A.; von Helden, G.; Meijer, G.; Lehnert, U.; Seidel, W.; Wünsch, R.; Michel, P.; Bluem, H.; Todd, A.; Rathke, J.; Young, L.; Dowell, D.

An IR and THz free-electron laser for applications in, i.a., molecular and cluster spectroscopy as well as surface science has been installed at the Fritz-Haber-Institut in Berlin. Commissioning has started at the end of July 2011. On February 14th ‘first lasing’ was observed at a wavelength of about 18 µm.
The normal-conducting electron linac together with a gun-to-dump electron beam line has been designed, fabricated, and installed by Advanced Energy Systems, Inc. It comprises two S-band (2.99 GHz) standing-wave copper structures. The first one is designed to accelerate the electron bunches to a fixed energy of 20 MeV, while the second one shall accelerate or decelerate the electrons to any final energy between 15 and 50 MeV. Electron bunches of up to 300 pC charge are accelerated at a maximum rate of 1 GHz. A chicane between the two structures allows for variable bunch-compression down to 1 ps. Further, the design length of the electron macro-pulses is as long as 15 µs with a maximum repetition rate of 20 Hz.
The electrons will, eventually, be steered through either one of two oscillator FELs, So far, the first FEL has been installed. It includes a 2-m-long planar hybrid-magnet undulator made by STI Optronics, Inc. with a period of 40 mm, which is enclosed within a 5.4 m long IR cavity. At a minimum gap of 16.5 mm a maximum undulator parameter of more than 1.6 is reached. As a result, it is expected that MIR radiation in the range from 4 µm up to almost 50 µm can be produced with this system. Hole-outcoupling is used to extract a beam from the IR cavity. The cavity length will be stabilized using the feedback signal from a HeNe-laser interferometer.
The design of the FIR FEL, so far, has been outlined. It shall employ a 7.2 m long cavity containing a full-length 1-dimensional waveguide and a more than 4 m long undulator with a period of 11 cm. The design wavelength range covers the FIR from about 30 µm all the way to the THz regime up to about 500 µm. We will present the status of commissioning and design of the MIR and FIR FEL, respectively.

  • Poster
    503th Wilhelm and Else Heraeus Seminar Free-Electron Lasers: from Fundamentals to Applications, 10.-13.04.2012, 10.-13.04.2012, Bad Honneff, Deutschland

Publ.-Id: 17452

Actinides in Biological Systems

Geipel, G.; Viehweger, K.

Actinides are elements with atomic numbers between 89 and 103. All actinides are radioactive, heavy elements. Due to their occurrence the can be separated into two groups: Naturally occurring actinides and synthetic elements. However, the line between these two groups is not a sharp one. This is due human activities in use and testing nuclear power and nuclear weapons as well as in a very smaller amount due to natural nuclear reactors in the Proterozoic era. Thorium, protactinium, uranium and in much smaller amounts plutonium are the naturally occurring elements. Neptunium and all elements with atomic numbers (AN) larger than 94 are synthetic elements. The isotopes of elements beginning with einsteinium (AN=99) have relatively short lifetimes of the radioactive decay (< 472d Es-252) and there availability is very limited, therefore no information about their behaviour in biological systems have been published up to now.
Especially uranium, neptunium, plutonium and partly also americium can exist in different oxidation states. Therefore for these elements redox reactions in biological systems are of great significance.
Actinoides can be accumulated in the human body. However, the accumulating organs are different. While protactinium is mainly accumulated in kidneys and bones, plutonium is incorporated in lung, liver and bones. All actinoides show long residence times in the human body. Therefore it is sometimes not easy to distinguish between chemical toxicity and radiotoxicity.
Most of the literature deals with monitoring of radioactivity and calculation of doses in living systems, however, this will be not the focus of this contribution.
Thorium exits in the natural environment only in the oxidation state +4. Therefore it precipitates very easily. Due to this the transfer of thorium from soil to plants is much lower compared to uranium, for instance.
The only long living isotope of protactinium is Pa-231, a member of the U-235 decay chain. Up to now the biology of this element focuses only on the radiometric determination.
The use of depleted uranium in recent years increased the research in the behaviour of this element in biological environments latterly. New results show that due to the comprising coordination chemistry of uranium a change in the coordination of uranium occurs, when uranium is transported to different biological compartments. Additionally a lot of work to study the influence of uranium to microorganism and plants has been done in the past.
The next element in the actinoides series is neptunium. All members of this naturally occurring decay series have been decayed. Only studies with artificial neptunium isotopes have been done. It is known that microorganisms are able to reduce neptunium(V). Also neptunium is able to bond to transferrin and other proteins of the blood plasma.
Due to its high radio toxicity plutonium has been mainly studied with complexing agents as transferrin. Additionally several studies with microorganisms have been performed. Due to the five possible oxidation states the redox behaviour of plutonium in biological systems is of basic interest.
The next elements in the series of actinoides exits mainly in the oxidation state +3. Therefore it can be expected that their biological behaviour is similar. Nevertheless, several examples for americium, curium will be given. Some sorption behaviour of microorganisms towards americium has been published.
For curium the interaction with microorganism has been studied. It should be lined out here that curium shows an extraordinary high fluorescence emission yield, which enables studies at extremely low concentrations of this element down to 10-11 Mol/l. As an example the speciation of curium in human urine (Cm addition to urine) was determined.
No studies for berkelium in biological systems are reported.
Californium has been used as neutron source to irradiate blood lymphocytes.
Several data are available, dealing with questions of the decontamination of inhaled or ingested actinoides into human body.
Lanthanoides (elements of the 4f series) show similar chemical behaviour as actinoides in the same oxidation state.

Keywords: Actinoide; Lanthanoide; biological systems

  • Book chapter
    W. Maret: Binding, Transport and Storage of Metal Ions in Biological Systems, London: RSC, 2014, 978-1-78262-282-6, 800-832
    DOI: 10.1039/9781849739979-00800

Publ.-Id: 17451

Rétention de l’europium par la calcite : de l’adsorption à l’incorporation dans le matériau

Sabau, A.; Lomenech, C.; Marmier, N.; Jordan, N.; Barkleit, A.; Brendler, V.; Toulhoat, N.; Pipon, Y.; Moncoffre, N.; Giffaut, E.

Les mécanismes d’interaction entre cations et minéraux peuvent inclure des processus d’adsorption, de (co-)précipitation de surface, et aller jusqu’à l’incorporation au sein du matériau, ce qui peut entraîner l'irréversibilité de certaines réactions de sorption. Le minéral choisi pour cette étude est la calcite, présente dans les argilites du Callovo-Oxfordien et également produit d’altération des ciments sur des échelles géologiques, ce qui justifie son intérêt pour l’évaluation de la sûreté d’un site de stockage de déchets radioactifs en site géologique profond. Le cation étudié est l’europium, en tant qu’analogue de certains actinides. La démarche adoptée est la combinaison de données macroscopiques de rétention avec une étude spectroscopique : SLRT pour tenter d’élucider les mécanismes de sorption, et RBS pour confirmer la précipitation de surface ou l’incorporation au sein du matériau et obtenir les profils de diffusion.
Les expériences en réacteur fermé ont été menées sous conditions atmosphériques (pCO2 = 10-3.5 atm) en milieu NaCl 0,1 mol.L-1, pour des concentrations d’europium variant de 10-6 à 10-3 mol.L-1 et des temps de contact variant de quelques heures à 1 mois. Les analyses ICP-AES des surnageants montrent une rétention très forte par la calcite quelles que soient les conditions expérimentales.
Les résultats de SLRT montrent un comportement différent de l’europium en fonction de la concentration initiale et du temps de contact. Pour chacune des concentrations, deux espèces sont mises en évidence, leurs temps de vie augmentant lorsque la concentration initiale diminue, et lorsque le temps de contact augmente, ce qui correspond à une perte progressive des molécules d’eau entourant l’europium.
Pour les concentrations les plus fortes, les espèces identifiées semblent correspondre à un (co-)précipité de surface et un complexe de surface ayant conservé deux molécules d’eau en sphère interne. Les mesures RBS effectuées pour ces concentrations, montrent une accumulation de l’europium à la surface de l’échantillon, ce qui confirme l’hypothèse du précipité de surface. Pour les concentrations plus faibles, les temps de vie observés sur l’une des espèces, beaucoup plus longs, et proches de ceux obtenus par Fernandes et al. [1] qui ont effectué des synthèses directes par coprécipitation, semblent indiquer une incorporation de l´europium au sein du matériau.

Keywords: calcite; Eu; TRLFS; RBS

  • Lecture (Conference)
    XIIIe Journées Nationales de Radiochimie et Chimie Nucléaire, 04.-05.10.2012, Nantes, France

Publ.-Id: 17450

Emission bands of nitrogen-implantation induced luminescent centers in ZnO crystals: Experiment and theory

Dai, X. M.; Xu, S. J.; Gu, Q. L.; Ling, C. C.; Brauer, G.; Anwand, W.; Skorupa, W.

High quality ZnO crystal with the sharp band-edge excitonic emission and very weak green emission was implanted by nitrogen ions. An additional red emission band was observed in the as-implanted ZnO crystal and investigated as a function of temperature. By employing the underdamped multimode Brownian oscillator model for general electron-phonon coupling system, both the original green and nitrogen-implantation induced red emission bands were theoretically reproduced at different temperatures. Excellent agreement between theory and experiment enables us determine the energetic positions of the pure electronic levels associated with the green and red emission bands, respectively. The determined energy level of the red emission band is in good agreement with the data obtained from the deep-level transient spectroscopic measurements.

Publ.-Id: 17448

Cannabinoid Receptor Type 2 (CB2) Selective N-Aryl-oxadiazolyl-propionamides: Synthesis, Radiolabeling, Molekular Modelling and Biological Evaluation

Rühl, T.; Deuther-Conrad, W.; Fischer, S.; Günther, R.; Hennig, L.; Krautscheid, P.; Brust, P.

Background: The endocannabinoid system is involved in many physiological and pathological processes. Two receptors (cannabinoid receptor type 1, CB1, and type 2, CB2) are known so far. Many unwanted psychotic side effects of inhibitors of this system can be addressed to the interaction with CB1. While CB1 is one of the most abundant neuroreceptors, CB2 is expressed in the brain only at very low levels. Thus, high potent and selective compounds for CB2 are desired. N-Aryl-((hetero)aromatic)-oxadiazolyl-propionamides represent a promising class of such selective ligands for the human CB2. Here, a library of various derivatives is studied for suitable routes for labelling with [18F]. Such [18F]-labelled compounds can then be employed as CB2 selective radiotracers for molecular imaging studies employing positron emission tomography (PET).
Results: By varying the N-arylamide substructure we could explore the binding pocket of the human CB2 receptor and identified the 9-ethyl-9H-carbazole amide as the group with optimal size. Radioligand replacement experiments revealed that the modification of the (hetero)aromatic moiety in 3-position of the 1,2,4-oxadiazoles shows only moderate impact on affinity to CB2 but high impact on selectivity towards the CB2 with respect to CB1. Further, we could show by autoradiography studies, that the most promising compounds bind selectively on CB2 receptors in mouse spleen tissue. Molecular docking studies based in a novel 3D structural model of the human CB2 receptor in its activated form indicate that the compounds bind with the N-arylamide substructure in the binding pocket. [18F]-labelling at (hetero)aromatic moiety at the opposite site of the compounds via radiochemistry were carried out.
Conclusions: The synthesized selective CB2 compounds have high affinity towards CB2 and good selectivity against CB1 receptors. The introduction of labelling groups at the (hetero)aromatic moiety shows only moderate impact on CB2 affinity, indicating the introduction of potential labelling groups at this position as a promising approach to develop selective CB2 ligands suitable for molecular imaging with PET. The high affinity for human CB2 and selectivity against human CB1 of the herein presented compounds renders them as suitable candidates for molecular imaging studies.

Publ.-Id: 17447

The IR and THz user facility FELBE

Seidel, W.; Winnerl, S.; Bhattacharyya, J.; Teich, M.; Fehrenbacher, M.; Drachenko, O.; Schneider, H.; Helm, M.; Zvyagin, S.; Wosnitza, J.; Bauer, C.; Gensch, M.; Schurig, R.; Lehnert, U.; Michel, P.

The FELBE user facility located at the Helmhotz-Zentrum Dresden-Rossendorf operates two free-electron lasers (FELs). Here we discuss the basic parameters of the FELs and the experimental opportunities at the facility. The FELs are based on the superconducting electron linear accelerator ELBE, which provides short (picosecond) electron bunches with energies up to 35 MeV at a 13 MHz repetition rate. The two FELs of FELBE (FELBE stands for FEL@ELBE) are equipped with two undulators, one for the mid-infrared spectral range (wavelengths 4 – 22 µm) and one for the far-infrared or THz range (wavelengths 20 – 250 µm).
The key feature which distinguishes FELBE from other FEL user facilities is the possibility of “quasi cw” operation (meaning a continuous train of pulses, also called micropulses), made possible by the superconducting accelerator cavities. The FEL thus provides picosecond optical pulses at a repetition rate of 13 MHz. In this mode, the average power can reach up to 30 W (depending on the wavelength) corresponding to more than 1 µJ pulse energy. Additionally FELBE can be operated in a macrobunch mode and, via pulse-picking, a 1 kHz mode.
The two FELs can be synchronized to a number of tabletop femtosecond and picosecond lasers, enabling two-color experiments from the near-infrared to the THz frequency range. The main techniques at FELBE are pump-probe spectroscopy [1-3] and time-resolved photoluminescence [4]. Furthermore there is a lab devoted to near-field microscopy [5,6]. Spectroscopy with FELBE radiation is also possible in pulsed high magnetic fields up to 70 T (150 ms magnetic pulse duration) [7].
FELBE is operated as a user facility, i.e., scientists from other institutions are invited to submit short research proposals and apply for beamtime.

  • Poster
    503th Wilhelm and Else Heraeus Seminar Free-Electron Lasers: from Fundamentals to Applications, 10.-13.04.2012, Bad Honneff, Deutschland

Publ.-Id: 17446

Bestimmung der Neutronennachweiseffektivität von Plastik-Szintillationsdetektoren

Hannaske, R.; Beyer, R.; Birgersson, E.; Junghans, A. R.; Kögler, T.; Nolte, R.

Der Rossendorf Low-Amplitude-Neutron Detector (RoLAND) besteht aus 1000 × 42 × 11mm3 großen Streifen des Materials EJ-200, dessen Szintillationslicht mit hoch-verstärkenden Photomultipliern an zwei Seiten detektiert wird. Durch koinzidenten Nachweis von Signalen geringer Amplitude liegt die Nachweisschwelle für Neutronen bei weniger als 10 keV. Zur Bestimmung absoluter Wirkungsquerschnitte von (𝛾, n)- und (n, n’𝛾)-Reaktionen, wie sie in den Bereichen nukleare Astrophysik oder Transmutation benötigt werden, wurden am supraleitenden Elektronen-Linearbeschleuniger ELBE Experimente durchgeführt, bei denen sich die Detektoren im Gegensatz zu einer früheren Bestimmung der Effektivität in einem wesentlich kleineren Abstand und in einer Abschirmung aus Blei befanden. Ein Vergleich der Neutronennachweiseffektivität mit Simulationen und neueren Messungen relativ zu einer 235U-Spaltkammer zeigten deutliche Abweichungen insbesondere nahe der Schwelle. Daher wurde an der PTB Braunschweig eine weitere Kalibrierung im Energiebereich 20 − 5000 keV durchgeführt,
deren Ergebnisse vorgestellt werden.

Keywords: neutron detector; efficiency; neutron time-of-flight

  • Lecture (Conference)
    DPG Frühjahrstagung, 19.-23.03.2012, Mainz, Deutschland
  • Poster
    525. Wilhelm und Else Heraeus-Seminar "Nuclear Physics Data for the Transmutation of Nuclear Waste", 25.-27.02.2013, Bad Honnef, Deutschland

Publ.-Id: 17445

Präzisionsmessung der Photodissoziation des Deuterons bei Energien im Bereich der Big-Bang-Nukleosynthese

Hannaske, R.; Bemmerer, D.; Beyer, R.; Birgersson, E.; Ferrari, A.; Grosse, E.; Junghans, A. R.; Kempe, M.; Kögler, T.; Kosev, K.; Marta, M.; Massarczyk, R.; Matic, A.; Schilling, K.-D.; Schramm, G.; Schwengner, R.; Wagner, A.; Yakorev, D.

Die für die primordiale Nukleosynthese wichtige Reaktion 𝑑(𝛾, 𝑛)𝑝 wurde am supraleitenden Elektronen-Linearbeschleuniger ELBE mit Bremsstrahlung bei einer Endpunktenergie von 5,0 MeV untersucht. Neutronen mit einer kinetischen Energie von 20 − 1400 keV wurden mit Hilfe der Flugzeit-Detektoren RoLAND (Rossendorf Low-Amplitude-Neutron Detector) nachgewiesen, deren Effektivität 2011 an der PTB Braunschweig bestimmt wurde. Wechselwirkungen der emittierten Neutronen mit dem Targetmaterial (23 Schichten aus Aluminium und deuteriertem Polyethylen) wurden simuliert. Der Photonenfluss wurde mit Hilfe der resonanten Streuung an Aluminiumkernen bei Energien von 2,2 und 3,0 MeV bestimmt. Der experimentelle Aufbau, die Datenanalyse sowie vorläufige Ergebnisse werden präsentiert.

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

  • Poster
    DPG Frühjahrstagung, 19.-23.03.2012, Mainz, Deutschland

Publ.-Id: 17444

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