Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Transition metal chalcohalides MX2 can form a wealth of diverse nanostructures, largely as a function of the synthesis conditions. The obtained structures range from large octahedral and fullerene-like hollow clusters and cylindrical nanotubes close to the nominal composition M:X = 1:2 to smaller, two-dimensional platelet-shaped clusters under sulfur excess and to one-dimensionally elongated nanowires under sulfur-deficient conditions. All of those structures exhibit specific electronic properties that differ from the ones of the pure bulk and open up a large spectrum of nanostructure applications, that still includes the lubricant aspect, but reaches further to catalysis and electronic transport. One-dimensionally delocalized electronic states provide the basis for the higher activity, reactivity and conductivity in nanostructured MX2. Larger triangular and hexagonal platelets exhibit a so-called 'brim'-state along the circumference of the cluster, which assists the activation of sulfur atoms contained in raw oil; hence platelet-based catalysts are employed for desulfurization. One-dimensional wires with compositions MX an M2X3 are composed of a central metallic wire coated by an insulating sulfur and/or halide shell. They exhibit a very high structural regularity, hence, ballistic conductivity may be obtained in such structures. The stability, structure and metallicity of such wires have been calculated in excellent accordance with recent scanning-probe experiments. In addition, the calculations showed, that wires can act as electromechanical switches, because they undergo a symmetry-dependent metal-insulator transition upon twisting. Thus, metal chalcohalide nanostructures are versatile building blocks for nanoscale catalytic and electronic devices.

Small-angle neutron scattering was applied to investigate the size distribution of irradiation-induced defect-solute clusters in a reactor pressure vessel weld material containing 0.22 wt% copper. In order to identify flux effects the material was exposed to neutron irradiations at two different levels of neutron flux in such a manner that the same value of neutron fluence was accumulated. We observed a pronounced effect of neutron flux on the cluster size, whereas the total volume fraction of the irradiation-induced clusters was found to be insensitive to the level of flux. The result is compatible with a rate theory model according to which the range of applied fluxes covers the transition from a flux-independent regime at lower fluxes to a regime of decelerating cluster growth. The issue of the effect of flux on the mechanical properties is also addressed.

Ion beam analysis @ FZD
Since more than 30 years ion beam analysis is performed at the Forschungszentrum Dresden-Rossendorf (FZD) for the determination of element distributions. Due to continuous upgrades of the different experimental set-ups, we are able to routinely perform:
• Rutherford Backscattering Spectrometry (RBS) & Channeling (C-RBS)
• Nuclear Reaction Analysis (NRA)
• Elastic Recoil Detection Analysis (ERDA)
• Particle-Induced X-Ray Emission (PIXE)
• Particle-Induced Gamma-Ray Emission (PIGE)

State-of–the art with “old” 5 MV accelerator
Most of our applications lie within material sciences. We are able to measure non-destructively “all natural” elements, i.e. hydrogen to uranium, most elements with lateral, some even in 3-D resolution with the following typical parameters (highly depending on matrix and elements):
• depth resolution: 1-30 nm
• depth range: nm-µm
• lateral resolution: few µm
• usual mapping area: 2x2 mm²
• maximum sample size: 3x10 cm² (vacuum) & “unlimited” (external beam)
• detection limits: ~10 µg/g (H); 500 µg/g – 1% (He-F); 10-100 µg/g (Na-U)
For some elements, e.g. H/D, isotope analysis is possible.

Outlook for “new“ 6 MV accelerator
In summer 2009, the 30-year-old Russian-made van-de-Graaff 5 MV accelerator will be replaced by the latest 6 MV Tandetron model from HVE, which is even more sophisticated than the lately installed 5 MV version from Southern France. Our new accelerator will need of course less maintenance allowing more beam time for real measurements with respect to our old one. It might be also possible to expand from two to three 8-hour-shifts a day with the new fully automatic system.
Scientifically, the main advantages for ion beam analysis are an increased depth range by a factor of 2 for ERDA and improved detection limits for NRA. In addition, the machine will be installed with special equipment for accelerator mass spectrometry (AMS).

AMS
There is a main advantage of using a high-energy accelerator for mass spectrometry: The background and interfering signals, resulting from molecular ions and ions with similar masses (e.g. isobars) are nearly completely eliminated. Thus, AMS generally provides much lower detection limits in comparison to conventional mass spectrometry (typical isotope ratios 10^-10-10^-15). Our AMS system will offer excellent measurement capabilities also for external users.
In contrast to common low-energy AMS facilities in Europe, which have mainly specialized in radiocarbon analyses (¹⁴C), the FZD-AMS is the first modern-type facility in the EU that will run at a terminal voltage of 6 MV.
Especially in environmental and geosciences, the determination of long-lived (t_1/2 > 0.3 Ma) cosmogenic radionuclides like ¹⁰Be, ²⁶Al, and ³⁶Cl became more and more important within the last decades. Using these nuclides dating of mass movements, e.g. volcanic eruptions, rock avalanches, earth quakes, and glacier movements is possible.

Radioactive or stable cosmogenic nuclides are products of nuclear reactions induced by cosmic rays. The development of the interdisciplinary field of the quantification of cosmogenic nuclides has been increased dramatically in the last decades. Especially, the progress in the field of accelerator mass spectrometry (AMS) improved detection limits and accuracy and allows nowadays the determination of radionuclide concentrations as low as of 10⁴-10⁵ atoms/(g rock).
In particular, in-situ produced cosmogenic nuclides – so-called terrestrial cosmogenic nuclides (TCN) - have proved to be valuable tools for quantifying Earth's surface processes. Here, the work-horses are ¹⁰Be and ²⁶Al in quartz, and ³⁶Cl in Ca- or K-rich minerals.
In siliceous environments both radionuclides, ¹⁰Be and ²⁶Al, are pure high-energy spallation products, thus, the influence on the secondary neutron field by changing trace element concentrations in the original bulk matrix is negligible. Another advantage: Usually, quartz can be easily cleaned from other mineral phases making the normalization to (g SiO₂)^-1, i.e. only two target elements, very straightforward. There is usually no need for a full chemical analysis.

In contrast, ³⁶Cl can be produced by several different nuclear reactions: Spallation on different target elements, mainly Ca and K (to a lesser extent Ti and Fe), induced by high-energy neutrons and muons. Thus, every sample that will be analysed for TCNs has to be chemically analyzed for the main target elements, too. Additionally, as ³⁶Cl can be produced by thermal neutron-capture on ³⁵Cl, trace elements influencing the thermal neutron field have to be unavoidably also measured. This includes U and Th as “background”-neutron emitter, all elements with high neutron absorption cross sections like B, Gd, and Sm, and all light elements, which take part in (gamma,n)-reactions. Thus, a complete bulk rock analysis (for the neutron field) and measurements of the main target elements in the dissolved fraction are absolutely necessary. As ³⁶Cl concentrations will be normalized to (g Ca)^-1, (g K)^-1 etc., the overall result cannot be more precise then the corresponding target element data.

We have selected typical samples with different fractions of silicate- and calcite-rich phases to have them analyzed by the method of choice of most TCN-user: inductively coupled plasma optical emission spectrometry (ICP-OES). Unfortunately, the two French CNRS laboratories involved, CEREGE and CRPG-SARM, did not produce concordant results for all elements of interest. Thus, we have tested the capability of two non-destructive activation analysis methods: We performed Instrumental Neutron Activation Analysis (INAA) ourselves at Vienna and we sent aliquots for Prompt Gamma Activation Analysis (PGAA) to Budapest.

The four laboratories performed differently depending on the analyte. For example, all methods produce CaO-data with unacceptable high uncertainties. PGAA seems to underestimate the true CaO-value of some samples. K₂O-data (@ 0.1-0.7%) by ICP-OES has exceptional high uncertainties and is constantly lower as corresponding INAA- and PGAA-data. As a conclusion, it seems advisable to use more than a single analytical method, if precise TCN applications are intended.

³⁶Cl AMS measurements at natural isotopic concentrations have yet been performed only at tandem accelerators with 5 MV terminal voltage or beyond. We have developed a method to detect ³⁶Cl at natural terrestrial isotopic concentrations with a 3-MV system, operated above specifications at 3.5 MV.
An effective separation was obtained with an optimized split-anode ionization chamber design (adopted from the ETH/PSI Zurich AMS group), providing a suppression factor of up to 30.000 for the interfering isobar ³⁶S. Despite the good separation, a relatively high sulfur output from the ion source (³⁶S^-/³⁵Cl^- = 5×10^-11) resulted in a background corresponding to ³⁶Cl/Cl = 3×10^-14. The method was applied to samples containing between 10⁵ and 10⁶ atoms ³⁶Cl/g rock from sites in Italy and Iran, which were already investigated by other laboratories for surface exposure dating. The ³⁶Cl/Cl ratios in the range from 2×10^-13 to 5×10^-12 show a generally good agreement with the previous results.
These first measurements demonstrate that also 3-MV tandems, constituting the majority of dedicated AMS facilities, are capable of ³⁶Cl exposure dating, which is presently the domain of larger facilities.

In contrast to siliceous environments, there is a severe lack of cosmogenic nuclides, which can be used for in-situ dating of calcareous environments. Thus, we have investigated other nuclides than ³⁶Cl as possible dating tools by cross-calibration. Cosmogenic ¹⁰Be is highly contaminated with atmospheric ¹⁰Be and cannot be removed quantitatively, even by a very sophisticated chemical cleaning procedure. Only working on clay-free calcite provides correct ¹⁰Be data, giving a 2.7 times higher production rate of ¹⁰Be from CaCO₃ than from SiO₂. Though, the production rate of ²⁶Al is only ~4.6% (CaCO₃ relative to SiO₂), ²⁶Al can be easily determined in calcite, as the low intrinsic ²⁷Al concentration yields to nearly as high ²⁶Al/²⁷Al as within corresponding quartz. The measurement of ⁴¹Ca, mainly produced via thermal-neutron-capture, is hindered by very low ⁴¹Ca/Ca: < 2.5x10^-15.

Ceramics intended for use as nuclear fuels, transmutation targets or actinide immobilization matrices have to endure severe conditions including internal radiation. While zirconia-based materials with defect-fluorite structure have shown high tolerance against external ion-beam irradiation, few experimental studies have demonstrated that these structures also resist under more realistic conditions, i.e. with homogeneous internal radiation from α-emitting actinides within the structure. Here, we provide for the first time experimental insight into the radiation-resistance mechanisms of americium pyrochlore ²⁴¹Am₂Zr₂O₇. We combined X-ray diffraction and X-ray absorption spectroscopy to probe changes of both the long-range and the short-range structure. The phase transition from the pyrochlore to the defect-fluorite structure was accompanied with an unusual negative lattice expansion. Once the fluorite structure was reached, neither volume changes nor amorphization were observed over a time course of 4 years corresponding to 0.8 dpa. The disorder relaxation proceeds through the simultaneous formation of cation antisites and oxygen Frenkel pairs, in line with former molecular dynamics studies. Moreover, EXAFS analysis revealed a disruption in the long-range order and a markedly different development in the local environments of zirconium and americium: while Am-O polyhedra show an increasing disorder, the Zr-O polyhedral units remain unchanged. However, they rotate along edges and corners, thereby reducing the structural strain imposed by the growing disorder around americium. We believe it is this particular property of the compound that provides the remarkable resistance to radiation, making it attractive for a wide range of nuclear applications.

The generation of high magnetic fields for scientific and industrial applications, in particular those techniques which meet critical limits of field strength, coil heating, and mechanical stress as well, require a careful design and modelling based on finite-element simulation. In order to describe the mutual dependences of the electrical, thermodynamical, and mechanical processes in such systems in a reasonable way, the use of multi-physics modules of the finite-element software packages becomes more and more relevant. Here, the designs based on finite- element simulations of pulsed magnetic field coils for extreme magnetic flux densities up to 100 Tesla as well as pulsed power supplies for the generation of electrical current pulses up to the Mega-Ampere range are presented. A survey on recent technical progresses in science and industry is given.

The beamline BM20 operated by the Forschungszentrum Dresden-Rossendorf is located at ESRF storage ring and divided into two experimental stations for spectroscopy and diffraction. A double crystal monochromator provides an energy range from 6 to 30 keV. A six-circle goniometer allows different scattering and diffraction methods like XRR, XRD, GID and GISAXS, additionally even in combination with X-ray spectroscopy. Different detector systems (point, one, two dimensional or energy dispersive) as well as an additional detector bank for large area detectors are available. A major part of ROBL-MRH experiments are performed as in-situ X-ray studies using a dual magnetron sputtering deposition chamber equipped optionally with an ion gun for ion beam bombardment and erosion. Using a hemispherical Beryllium dome scattering experiments can be carried out up to 1200°C under vacuum conditions.
The focus of the beamline research is on thin film investigations and on new nanostructured materials. X-ray investigations are a very important tool to find the correlation between the functional and the corresponding structural properties that are generating this function and to explain the influence of different deposition conditions, substrate parameters etc. by the underlying physical processes making it possible to design thin films with specific properties.
By the use of the deposition chamber for reactive magnetron sputtering thin films of Ti2AlN were for the first time synthesized. Different ways of synthesis, the thermal and phase behavior were investigated [1, 2].
A key element for the development of a new generation of solar cells are nanocrystalline materials. In-situ studies of the growth of SiO2/GeOx multilayers were carried out to create Ge nanocrystalls by subsequent thermal decomposition or directly by sputtering at elevated temperatures.

[1] C. Höglund et al.; Appl. Phys. Lett., 90, 174106, (2007).
[2] M. Beckers et al.; Appl. Phys. Lett., 89, 074101, (2006).

We report on periodic ripple formation on Si(001) surfaces after bombardment with Xe+ ions with energies between 5 and 35 keV under incidence angles of 65 degrees and 70 degrees. The sputter process leads to the formation of a rippled amorphous surface layer, followed by a rippled interface toward crystalline material. Using grazing-incidence small-angle scattering and diffraction, we show that the surface morphology is exactly reproduced at the interface. In addition, we observe that the crystal lattice close to the interface is anisotropically expanded. The lattice expansion parallel to the ripples is larger than those perpendicular to them.

Ziel/Aim: Ziel der Arbeit ist die Entwicklung von bifunktionellen Markierungsbausteinen für eine milde und selektive Radiomarkierung von biologisch aktiven Molekülen mit dem Positronenstrahler Kupfer-64. In diesem Zusammenhang sind Pyridin-haltige Derivate des 1,4,7-Triazacyclononans (TACN) besonders geeignet, weil sie sehr stabile Kupfer(II)-Komplexe bilden sowie eine schnelle Komplexbildungskinetik aufweisen. Weiterhin ist es leicht möglich, diese Verbindungen mit Maleinimid- und Isothiocyanat-Derivaten oder Aktivestern zu modifizieren und damit an Biomoleküle zu kuppeln. Erste Untersuchungen zeigen, dass Komplexe von Kupfer-64 mit einem TACN-Carbonsäurederivat sowie ein entsprechendes Peptidkonjugat auf der Basis eines stabilisierten Bombesinfragments BBN(7-14) eine hohe in vitro- und in vivo-Stabilität besitzen.^[1] Bombesin und dessen Derivate weisen eine hohe Affinität zum Gastrin Releasing Peptide Rezeptor (GRPR) - der auf einer Vielzahl von Tumoren, wie Brust-, Prostata- und Pankreaskarzinomen, überexprimiert ist - auf. Aus diesem Grund sind radioaktiv markierte BBN-Derivate für die Diagnostik und Therapie von Tumoren sehr interessant.

Methodik/Methods: Die Umsetzung von Aminoethylmaleinimid mit einem TACN-Carbonsäurederivat durch Peptidkupplung mittels HBTU in Anwesenheit der Hünigbase DIPEA führt zu einer Maleinimid-haltigen TACN-Verbindung. In analoger Weise wurden über eine Peptidkupplung, stabilisierte BBN(7-14)-Derivate an TACN-Liganden gebunden. Ein weiterer vielseitig einsetzbarer Synthesebaustein wurde durch Umsetzung von zweifach pyridylmethylsubstituiertem TACN mit einem Boc-geschützten Phenylendiamin-Derivat erhalten. Durch Abspaltung der Schutzgruppe erhält man das freie Amin, das durch Behandlung mit Thiophosgen in das Isothiocyanat überführt wird.

Ergebnisse/Results: Markierungsstudien des Maleinimid-funktionalisierten TACN-Derivates mit Kupfer-64 weisen auf eine sehr schnelle Komplexbildungskinetik unter physiologischen Bedingungen hin. Untersuchungen mit dem Modellpeptid Glutathion zeigen, dass dieser Markierungsbaustein sehr effektiv an Thiolgruppen bindet. Bioverteilungsstudien mit Cu-64-Komplexen von TACN-Bombesin-Konjugaten in Wistar Ratten ergaben eine Anreicherung des Radiotracers im Pankreas. Untersuchungen mittels Kleintier-PET an PC-3 Tumor-Mäusen zeigten eine Akkumulation dieser Tracer im Tumorgewebe, so dass eine klare Visualisierung der Tumore möglich ist.

Schlussfolgerungen/Conclusions: Bifunktionelle Liganden auf der Basis von pyridinhaltigen TACN-Derivaten können unter physiologischen Bedingungen effektiv mit Kupfer-64 markiert werden. Die mit Maleinimid-, Isothiocyanat-Gruppen und Aktivester funktionalisierten TACN-Derivate können effizient an Biomoleküle gekuppelt werden. TACN-Bombesin-Konjugate besitzen ein hohes Anwendungspotential zur Darstellung von GRPR-reichem Gewebe.

Referenzen/Refrences:

[1] G. Gasser et al., Bioconjugate Chem. 2008, 19, 719-730.

there is no abstract available

Vanadium and silicon form several binary compounds; the most well characterized structures have
the compositions V:Si= 3:1, 5:3, 6:5, 1:2. Spin-Density-functional band-structure calculations with the
Projector Augmented Wave-method have been carried out to investigate the structural properties and the
phase stability for the experimentally known binary crystals.

Since approximately 20 years we have controversial discussions about the possibility of ion beam generated diluted magnetic semiconductors (DMS) primarily transition metals in silicon. Now a detailed study has been done for the system Vanadium:Silicon. Vanadium and silicon form several binary compounds; the most well characterized structures have the compositions V:Si= 3:1, 5:3, 6:5, 1:2; as well as different constellations of substitutional and interstitial vanadium atoms in a silicon crystal matrix. Suitable magnetic properties of a semiconductor are important for DMS.

While the Master Curve (MC) method is gradually entering brittle fracture safety assessment procedures world-wide, knowledge is still lacking about its limits of applicability to highly neutron irradiated material. In this paper two reactor pressure vessel (RPV) steels A533B Cl. 1 (IAEA reference material code JRQ) and A508 Cl.3 (code JFL) were scrutinized for possible deviations of the postulated invariant MC shape and the MC validity for macroscopically inhomogeneous microstructure. Besides tensile and Charpy-V tests, MC tests were performed on Charpy size three-point bend specimens in the unirradiated, neutron irradiated with fluences up to nearly 1020 n/cm² (E>1MeV) and recovery heat treated condition. Evaluation procedures include Master Curve reference temperature T0 determination according to ASTM E1921-05 as well as additional analysis methods such as SINTAP, multimodal MC method (MML) and the Unified Curve (UC). Integrity assessment according to ASME Code Cases N-629 and N-631has been applied. It is shown that the standard MC concept provides a precise description of the fracture toughness for all conditions, even exceptionally well for the highly irradiated state. No MC shape change could be observed, whereas the UC concept indicates a significant influence of irradiation on the fracture toughness curves for the highly irradiated JRQ.

Der Zugang zur THEREDA-Datenbank erfolgt über die URL http://www.thereda.de. Der Internetzugang vereint dabei die Schnittstelle für externe Nutzer zum Abfragen von Datensätzen sowie eine Schnittstelle zur Administration des gesamten Internetauftritts im Rahmen des Content Management Systems (CMS) Joomla! Joomla! ist Open Source Software, durch die große Community, die das Projekt ständig weiterentwickelt, ist gewährleistet, dass ein problemloser Zugriff auf den Inhalt und die Datenbank über einen sehr langen Zeitraum erfolgen kann. Mit Joomla! verfügt THEREDA über ein sehr gutes Tool, die Datenbank mit geringem Pflegeaufwand und über einen langen Zeitraum zur Verfügung zu stellen. Über www.thereda.de erhalten Besucher der Webseite Informationen zum Projekt und den THEREDA-Partnern, können Dokumente downloaden sowie Links zu anderen relevanten Projekten finden. Zusätzlich nutzen die Mitglieder des Verbundprojektes die Internetseite als Intranet (nach Anmeldung). Im Vortrag werden der gegenwärtige Stand des THEREDA-Online-Auftrittes und die interaktiven Möglichkeiten für die Nutzer vorgestellt.

PURPOSE
Respiratory motion blurs PET-images and may cause localization errors in studies acquired using breath holding such as CT and MRI. To reduce motion related influences on radiation therapy planning of lung cancer, image acquisition may be gated. The aim of our study was to compare motion of primary lung tumors as detected by respiration gated data acquired with PET, CT, MRI.

METHOD AND MATERIALS
So far, this ongoing study included four patients (median age 72.5 years) with NSCLC scheduled for radiation therapy. All patients were investigated under free breathing conditions and respiratory gated FDG-PET, CT and MRI. Image data was separated into eight comparable gates uniformly distributed over the breathing cycle. After blinded GTV-definition, volumes and centers of volumes (COV) were generated from all gates and all modalities. Comparative statistics were done using t-tests, confidence intervals and Lin's concordance analysis.

RESULTS
Median tumor volumes in PET, CT and MRI were 28 ml, 69 ml, and 46 ml, respectively. t-tests revealed significant differences for the comparison CT/MRI (p=0.04) and PET/CT (p=0.05), but not for MRI/PET (p=0.09). The medians of the maximum distances the COV traveled during the entire breathing cycle in PET, CT and MRI were 0.42 cm, 0.95 cm, 0.93 cm, respectively. t-tests revealed nearly significant differences between PET and CT (p=0.06) and MRI and PET (p=0.06), while the result for CT and MRI was in good agreement (p=0.74). Lin’s concordance analysis (OCCC=0.172) revealed best congruency between CT and MRI (rho=0.55), only fair congruency between MRI and PET (rho=0.2) and poor congruency between PET and CT (rho=0.02).

CONCLUSION
In our early experience, the differences in GTV-definition of NSCLC in 4D imaging by PET, CT and MRI are mainly related to the observer’s experience. As shown in other tumors before, PET revealed the smallest tumor volume. Due to the low movement of the tumors evaluated in the patients included so far, results are preliminary. Nevertheless, results suggest that MRI may be applicable in radiation therapy planning for GTV-definition. The inclusion of a higher number of patients with pronounced tumor movement during breathing is required.

CLINICAL RELEVANCE/APPLICATION
Gated 4D imaging in NSCLC may increase planning accuracy in radiation oncology. In selected patients, gated radiation therapy might be advantageous and may reduce toxicity in normal tissues.

Aim:

Cell-penetrating peptides (CPP) derived from the native peptide hormone human calcitonin (hCT) represent a high potential drug delivery system for in vivo intracellular targeting of diagnostic and therapeutic compounds. Cell penetration of hCT-derived substances was verified in vitro, however, the knowledge about CPP in vivo distribution and metabolism is very limited. Therefore we studied the in vivo radiopharmacology of Ga-68 radiolabeled DOTA modified, hCT-derived CPP in rats using small animal PET (1).

Methods:

Three hCT-derived peptides (hCT(9-32), LGTYTQDFNKFHTFPQTAIGVGAPNH2; [f_12,16]-hCT(9-32), LGTfTQDfNKFHTFPQTAIGVGAP-NH2; random (rd)-hCT(9-32), FLTAGQNTIQTPVKTGGHFPFADY-NH2) were at the N-terminus modified with DOTA. The internalization of the stabilized peptide, biodistribution and kinetics of the radiolabeled Ga-68-DOTA-hCT(9-32) or Ga-68-DOTA-[f_12,16]-hCT(9-32) or Ga-68-DOTA-rd-hCT(9-32) were studied with small animal PET. The arterial blood at different time points, and urine were analyzed for radio-metabolites.

Results:

Ga-68-DOTA-[f_12,16]-hCT(9-32) was in vitro internalized. In vivo the radio-peptides were eliminated mainly by the renal system, more than 50% of the injected dose was found at 60 min after injection in the urine, only small amounts of the activity were detected in the intestine. The general activity retention in the body was low, except the kidneys. The blood clearance of the original peptides reached terminal half-lifes of Ga-68-DOTA-hCT(9-32) 15.9 min, Ga-68-DOTA-[f_12,16]-hCT(9-32) 20.9 min, Ga-68-DOTA-rd-hCT(9-32) 15.8 min; the relative AUC in comparison to Ga-68-DOTA-hCT(9-32) were 100%, 170%, and 51%, respectively. The patterns of metabolic cleavage in the arterial blood were different. The Ga-68-DOTA-[f_12,16]-hCT(9-32) was metabolized to three radio-metabolites after 30 min, the other radiopeptides were degraded to more than five radioactive metabolites.

Conclusion:

It was shown that D-amino acid modifications of the sequence hCT(9-32) resulted in an increased in vivo stability and lower retention in the kidney cortex. The blood clearance and the elimination of the Ga-68-DOTA-peptides were relatively high and should be decreased by structural changes to enhance the tissue uptake of this drug carrier system.

References:

(1) Neundorf I, Rennert R, et Bergmann R, Bioconjug Chem. 2008 Aug;19(8):1596-603.

wird nachgereicht

Purpose: Planning target volume definition is one of the crucial points for gated radiotherapy. To gain reliable information on variability of tumour position and tumour motion during the course of fractionated radiotherapy a longitudinal study was implemented.

Patients and Methods: Patients with locally advanced, inoperable non small cell lung cancer are enrolled in a clinical protocol for curative treatment with 66 Gy @ 2 Gy. For treatment planning a 4D-FDG-PET/4D-CT with phase correlated attenuation correction of the PET in treatment position was performed (Biograph 16, Siemens). Target volumes are derived from the Internal Target Volume (ITV) + 7 mm (Clinical Target Volume) + 8 mm (Planning Target Volume) for the first week. The latter margin is reduced to 5 mm after 6 fractions if deviations in tumour location are small. For treatments patients are positioned by X-ray verification (ExacTrac-Xray, BrainLab). Repeat 4D-CT scans are acquired with an in-room CT (Primatom, Siemens) directly before treatment for the first 5 fractions and subsequently twice per week (i.e. 16 4D-CTs per patient). Immediate evaluation of the 4D-CTs includes verification of patient positioning and adequateness of treatment fields (Pinnacle, Philips). Further evaluation of data includes intra- and interfractional variability of tumour volume and centre of gravity. Margins will be evaluated simulating gated radiotherapy.

Results: The protocol started in January 2008. Up to now 5 patients are enrolled, 2 of them have completed their treatment. For the first 5 patients a PTV reduction to 79,5 % (SD 2,1 %) after the first treatment week could be reached, which led to a decrease of Mean Lung Dose of 0.7 Gy (SD 0.3 Gy). Preliminary evaluation of the 4D data shows minor intrafractional variability of the tumour volume compared to greater interfractional variations. The preliminary data rather suggest variability in contouring than true variability in tumour volume. The trajectory of centre of gravity associates with the tumour motion.

Conclusion: The preliminary data suggest only small setup variability during treatment. Extension of the data base and further analysis will address if dose escalation by introducing gated radiotherapy is possible.

Supported by BMBF (03ZIK/OncoRay) and Siemens Medical Solutions.

Aim: Ga-68 radiolabeled human albumin microspheres (Ga-68-DOTA-HSAM) with a diameter of 20 µm are expected to lodge in the pulmonary capillaries. The purpose of the study was to quantify the pulmonary perfusion (Q_r) in prone and supine position in terms of their imaging manifestations in healthy rats.

Methods: The animal research committee of the Landesdirektion Dresden approved the animal facilities and the experiments according to institutional guidelines and the German animal welfare regulations. Seven anesthetized, spontaneous breathing Wistar rats (297 +/- 53 g), were positioned either in prone (n=3) or supine (n=4) position and Ga-68-DOTA-HSAM were infused. Q_r was achieved by imaging the radioactivity distribution in the lungs. The animal PET 3D volume data were reconstructed with 3D OSEM MAP algorithm. After first measurement animals were arranged in opposite position and the PET measurement was repeated. The 3D data were at first manually coregistered and residual differences in the relative positioning of the lungs were corrected user independent (Rover, ABX GmbH, Germany). Masks for defining regions of interest (ROI) were set in the coregistered volume data for all animals. Mean normalized Q_r values (Q_mean) of the dorsal and ventral parts of the lungs were calculated of the basis of an automatic ROI-setting including threshold analysis.

Results: Vertical gradient of regional perfusion was significantly steeper in the supine, -0.131 ± 0.01 %/cm, than in the prone animals -0.055 ± 0.01 %/cm (P = 0,002), indicating that the vertical distribution of regional perfusion was in dependent regions more accentuated in the supine than in the prone infused animals. Changes in the vertical gradient after rotation in the opposite position resulted in a vertical gradient of -0.093 ± 0.031 %/cm in prone position. Vertical gradient in the supine position of prone infused animals was -0.093 ± 0.015 %/cm. Position changes did not produce significant changes in vertical gradient in supine (P = 0.125) and in prone infused animals (P = 0.25).
Conclusions: Ga-68-DOTA-HSAM (20µm) can be used for pulmonary perfusion studies in rats with small-animal PET. Q_mean was not affected by posture, whereas vertical gradient indicating significant decrease from dependent to the nondependent regions of Q_r in supine infused animals in supine position. Lung structure distribution changes are less pronounced than perfusion distribution changes in prone and supine position.
Distribution pattern of regional perfusion in prone and supine position in normal rat lungs will be used as reference data set for studies on injured rat lungs.

Ziel/Aim:

Eine event-basierte Bewegungskorrektur verbunden mit einer räumlichen Transformation jeder Line-of-Response (LOR) erlaubt eine exakte Korrektur von Patientenbewegungen in der PET. In den letzten Jahren haben wir bereits verschiedene Verbesserungen dieses Verfahrens vorgestellt. Neben Optimierungen zur klinischen Akquisition von List-Mode Daten, sowie der Entwicklung von Methoden zur Analyse der Patientenbewegungen wurde gezeigt, dass mit der Reduzierung der durch das limitierte Gesichtfeld begründeten Artefakte (Out-of-FOV) ein letztes wichtiges Hindernis für die klinische Nutzung bei Hirnmessungen beseitigt werden konnte. Ziel der nunmehr vorliegenden Arbeit war es, nach der klinischen Integration den Einfluss dieser Bewegungskorrektur innerhalb eines Patientenkollektivs mit starken Patientenbewegungen genauer zu quantifizieren.

Methodik/Methods:

Für die klinische Nutzung wurden zwei graphische Nutzeroberflächen entwickelt, die eine einfache Aufnahme von Bewegungs- und List-Mode Daten ermöglichen. Nach erfolgter Akquisition werden die Daten vollautomatisch verarbeitet und bewegungskorrigiert. Für die Evaluation des Einflusses der Bewegungskorrektur auf die Bildqualität bzw. Quantifizierung dynamischer PET Aufnahmen wurden aus einem Patientenkollektiv von [¹⁸F]DOPA Hirnstudien N=15 Patientendaten anhand der Größe der Bewegung ausgewählt. Für den jeweils unkorrigierten und korrigierten Datensatz wurden 8 ROIs innerhalb des Striatum sowie eine Referenz-ROI positioniert. Neben dem Vergleich der Zeit-Aktivitäts-Kurven (TAC) wurde mittels eines irreversiblen Zweikompartment-Modells mit Referenzgewebe die jeweiligen Einstromraten (R₀k₃) durch eine Patlak Auswertung berechnet und durch Kalkulation parametrischer Bilder entsprechend mit den Werten der unkorrigierten Daten verglichen.

Ergebnisse/Results:

Die entwickelten Benutzeroberflächen erlauben eine einfache Nutzung der List-Mode- sowie Bewegungsaufnahme in der klinischen Routine. Beim Vergleich der Datensätze konnten qualitative Verbesserungen sowie ein besseres Signal-to-Noise-Ratio (SNR) durch die Korrektur festgestellt werden. Des Weiteren zeigt die quantitative Auswertung der dynamischen Aufnahmen Unterschiede von bis zu 30% im Verlauf der TACs. Auch die Auswertung der ₀k₃ Parameter zeigt eine relevante Änderung und der Vergleich der parametrischen Bilder eine Reduzierung von Artefakten.

Schlussfolgerungen/Conclusions:

Durch die einfache Bedienung der Benutzeroberflächen konnten diese nunmehr für die generelle Aufnahme von Hirnaufnahmen an unserer Einrichtung etabliert werden. Bei der Auswertung der Patientendaten zeigte sich, dass die event-basierte Bewegungskorrektur nicht nur die Bildqualität sondern auch die Quantifizierung der Tracerkonzentrationen bei PET-Hirnstudien positiv beeinflusst. In Folge dessen werden nun alle Hirnaufnahmen mit deutlicher Patientenbewegung in unserer Einrichtung standardmäßig mit der event-basierten Bewegungskorrektur durchgeführt.

Respiratory motion introduces image artefacts not only in standard 3D-CT but also in 3D-PET images due to two reasons: (a) Smearing of the activity concentration and (b) an incorrect attenuation correction. In 4D-PET the effect of smearing becomes negligible but the influence of incorrect attenuation correction remains important.
To investigate the quantitative influence of attenuation correction on both PET acquisition methods (3D- and 4D-PET), a comprehensive phantom study was performed using a respiratory motion mimicking phantom on a dedicated Siemens Biograph 16 PET/CT, which had the extended capability of acquiring 4D-PET and 4D-CT data. The used respiratory motion phantom is able to simulate typical lung tumor motion in two dimensions with two possible patterns of respiration. The 3D- and 4D PET data sets were corrected with different CT attenuation data, namely a standard 3D-CT (pitch 1.5), a slow 3D-CT (pitch 0.5), an ultraslow 3D-CT (pitch 0.15), and also an average CT and a maximum intensity projection, both calculated from a 4D-CT (pitch 0.1). Additionally, the 4D-PET was corrected phase-wise with the 4D-CT (phase-correlated attenuation correction). For that purpose the synchronization between 4D-PET and 4D-CT has been verified. The reconstructed PET images were analyzed concerning the reconstructed volume, the activity concentration and the full width half maximum (FWHM) of the activity distribution in the direction of the highest phantom movement. Additionally, the motion amplitude of the phantom was obtained from the 4D-PET data sets.
Our results suggest that attenuation correction of 3D-PET data should be performed with a slow CT. However, the 4D PET data should be reconstructed using phase-correlated attenuation correction with a 4D-CT.

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

Methods: Cu-64 was complexed with a bis(2-pyridylmethyl) derivative of 1,4,7-triazacyclononane (TAC) and a bispidine 1,5-dicarboxylic acid derivative (Cu-64-N₂Py₄-OH(COOH)₂) conjugated to a stabilized bombesin (BBN) derivative βhomoGlu-βAla-βAla-[Cha13, Nle14]BN(7-14) (Garcia Garoya et al. 2007). Biodistribution, elimination, and metabolism were studied in rats. Tumor accumulation was exemplarily evaluated with small animal PET in xenografted mice bearing prostate (PC3), squamous cell carcinoma (FaDu), and colorectal (HT-29) human tumors. Cu-64 chloride was studied for comparison.

Results: PET imaging of Cu-64-N₂Py₄-OH(COOH)₂-BBN in mice 1 h after injection revealed tumor-to-background ratios of 2.1 (PC3), 2.4 (FaDu control), 1.0 (FaDu blocked), and 1.5 (HT-29). The uptake found in PC3 tumors with tissue sampling was significantly higher (5.3 control; 2.6 blocked). In comparison to the Cu-64-TAC-BBN, the uptake of Cu-64-N₂Py₄-OH(COOH)₂-BBN in rat pancreas and intestine was lower but the accumulation in kidney, liver, and stomach was higher. The metabolic stabilities of the Cu-64-labeled BBN‘s studied were comparable. More than 85% of the original substances were remained after 1 hour in vitro incubation with rat blood or blood plasma. In vivo all compounds were fast metabolized in rats, and lower than 5% of the original compounds were recovered in arterial blood plasma 1 hour after injection. However, the metabolism in xenografted nude mice was slower, after 1 hour 12% of blood plasma activity correspond to the original compound.

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

Ziel/Aim:

Für eine genaue Volumenabgrenzung von Zielstrukturen in PET-Aufnahmen mittels schwellwert-basierten Algorithmen wird der Einfluss verschiedener Faktoren (Objektgröße, Bildkontrast, etc.) auf den volumenreproduzierenden Schwellwert üblicherweise durch Kalibrierungsmessungen unter Nutzung von Zylinderphantomen mit eingesetzten Glashohkugeln bestimmt. In einer quantitativen Bewertung einer derartigen Phantommessung wurde auch nach Untergrundsubtraktion eine Abhängigkeit des relativen Schwellwertes vom Bildkontrast nachgewiesen. In der vorliegenden Arbeit soll nun systematisch der Einfluss der inaktiven Glaswand in den Kugelphantomen auf die beobachtete Kontrastabhängigkeit des untergrundbereinigten Schwellwertes untersucht werden.

Methodik/Methods:

Es wurden Kalibrierungsmessungen unter Verwendung eines Zylinderphantoms (Durchmesser: 20 cm, Höhe: 18 cm) durchgeführt. Die im Zylinder befindlichen 6 Kugeleinsätze besitzen Volumina von 2,5 ml bis 27 ml und eine Glaswanddicke von 1,2 mm. In 9 Phantommessungen mit einem ECAT EXACT HR+ (Siemens/CTI, Knoxville, Tennessee) wurden der Zylinder und die Kugeln mit unterschiedlichen Aktivitätsmengen (Fluor-18) befüllt um das Signal-Untergrund-Verhältnis und damit den Bildkontrast zu variieren. Der analytische Ausdruck für die Faltung der Objektfunktion (Aktivitätsverteilung) mit der Point Spread Function (PSF) wurde an die aus den experimentellen Bilddaten gewonnenen radialen Aktivitätsprofile angefittet.

Ergebnisse/Results:

Die aus den Least Squares Fits ermittelten Radien sind stets kleiner als die wahren Kugelradien, wenn die inaktive Glaswand in der Objektfunktion vernachlässigt wird. Erst unter expliziter Berücksichtigung der Wanddicke von 1,2 mm der Hohlkugeln in der Objektfunktion verschwindet diese scheinbare Radiusreduktion. Mit den berechneten theoretischen Aktivitätsprofilen der Phantomkugeln konnte zudem eine Absenkung des untergrundbereinigten Schwellwertes bei steigendem Untergrundanteil in den Bilddaten verifiziert werden. Die gemessene Kontrastabhängigkeit des relativen Schwellwertes nach Untergrundsubtraktion konnte daher vollständig mit dem Vorhandensein der inaktiven Glaswände in den Phantomstudien erklärt werden.

Schlussfolgerungen/Conclusions:

Inaktive Wände zur Separation verschiedener Aktivitätsbereiche in PET Phantommessungen verursachen auch nach erfolgter Untergrundsubtraktion eine Kontrastabhängigkeit des volumen-reproduzierenden Schwellwertes. In realen Patientendaten kann daher aufgrund der Abwesenheit inaktiver Wände der untergrundbereinigte optimale Schwellwert als unabhängig vom Bildkontrast angenommen werden. Kalibrierungsmessungen zur Bestimmung des korrekten Wertes für den volumenreproduzierenden Schwellwert können daher auf eine einfache Phantommessung ohne Untergrundaktivität reduziert werden.

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

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

Results: The equilibria were reached at the latest 10 hours after start of dialysis. The ionic Er-169-chloride (as negative control) and Re-186-perrhenate showed very similar diffusion kinetics compared with reference radiotracers. The colloidal radionuclides, incubated and dialyzed against electrolytes comparable with plasma (MEM Dulbeco medium), human synovia, or phosphate containing buffers were not detected in the dialysis solution (lower 0.5% of applied dose (%ID)), except Re-186-MM1. Significant amounts of compounds were found in the dialysis compartment. Incubation of the colloids with isotonic sodium chloride or 0.1 M hydrochloric acid was followed by an activity release into the dialysis solution YMM-1 (67%ID) and ERMM-1 (62%ID).

Conclusion: The increased stabilities of the carrier added radiocolloids studied in different electrolyte solutions was mainly a result of the presence of phosphate ions. The low solubility of the phosphates of rare earth elements, the binding to synovia proteins, and hydroxylation were the main mechanisms of colloidal particle stabilization or reformation of free or secondary formed Erbium or Yttrium ions. This generally results in formation of particles of low diffusibility, increasing the retention of the radiocolloids inside the joint before the radionuclide-loaded colloidal particles are phagocytozed by macrophages in the inflamed synovial membrane.

At the heavy ion therapy facility at the Gesellschaft für Schwerionenforschung Darmstadt, Germany, an in-beam PET scanner is operated for quality assurance monitoring simultaneously to the therapeutic irradiation. The PET scanner, which is completely integrated into the treatment facility, registers the annihilation γ - rays following the decay of minor amounts of β+ radioactive nuclei produced via nuclear reactions between the ions of the therapeutic beam and the atomic nuclei of the irradiated tissue. From a comparison of the reconstructed activity distributions with those predicted from the treatment plan, deviations between the prescribed and the applied dose distributions can be detected. The solution currently implemented for the reconstruction of in-beam PET data is the ML-EM algorithm adapted to the low statistics case and to the dual head geometry. The size of image elements (voxels) influences significantly the quality of the image. A small voxel size increases the resolution but produces high oscillations of a signal. Large voxels produce homogeneous images, however, with low spatial resolution. The size of the voxel is always a compromise between suppressing signal oscillations which requires larger voxel size, and covering small imaging details which requires smaller voxel size. The standard voxel side-length used for the BASTEI scanner, 1.6875 mm, is exactly 1/4 of the crystal width. For in-beam PET the size of the voxel can be enlarged for typical irradiation fields from the standard (1.6875 mm)3 to 2 × 2 × 3 mm3 without loss of quality. The images reconstructed with bigger voxel are less noisy and still contain enough information about activity in small cavities and deviations of the range. Reconstruction performs almost two times faster for the 2 × 2 × 3 mm3 voxel.

At the heavy ion therapy facility at the Gesellschaft für Schwerionenforschung Darmstadt, Germany, an in-beam PET scanner is operated for quality assurance monitoring simultaneously to the therapeutic irradiation. The PET scanner, which is completely integrated into the treatment facility, registers the annihilation γ - rays following the decay of minor amounts of β+ radioactive nuclei produced via nuclear reactions between the ions of the therapeutic beam and the atomic nuclei of the irradiated tissue. From a comparison of the reconstructed activity distributions with those predicted from the treatment plan, deviations between the prescribed and the applied dose distributions can be detected. The solution currently implemented for the reconstruction of in-beam PET data consists of ML-EM and recently developed randomly filled subsets expectation maximization (RFS-EM) algorithms adapted to the low statistics case and to the dual head geometry. We proposed the reconstruction scheme for the subsets based RFS-EM algorithm. The scheme includes 4 iterations only, the number of subsets decreases from iteration to iteration and equals to 8, 6, 4, and 2 subsets, respectively. The scheme has been tested for two typical irradiation cases: head and neck (image space dimensions: 190 × 122 × 122 mm3) and pelvic (398 × 152 × 136 mm3) fields. The image quality was evaluated by means of visual inspection, root mean square error, and sensitivity of the method to the range deviations. The images reconstructed with the proposed RFS-EM scheme are of similar quality as those reconstructed with the reference 50 iterations of ML-EM. High quality of the system matrix is required for RFS-EM reconstructions of large fields.

Dental enamel has been widely studied by particle-induced x-ray emission (PIXE), but less attention was paid to its demineralization, which leads to caries formation. Using broad-beam PIXE and mu-PIXE, we investigated normal enamel and the in vitro formation of pre-carious lesion in lactic acid solution, aiming also to evaluate intercusp differences within the same tooth. Broad-beam PIXE was performed using 3.0 MeV protons, and µm-PIXE maps of Ca, Fe and Zn were collected with 3.1 MeV protons at similar to 4 mu m resolution. In normal enamel a differentiated Ca-rich surface layer was observed, where Fe and Zn reached their highest levels. In deeper layers, Fe and Zn evidenced quasiperiodic patterns of maxima, possibly due to coupled diffusion-reaction catalytic processes involved in the enamel growth. Both Fe and Zn appeared to be located in a few distinct types of pools. Near the surface, demineralization induced an increase of Fe, Cu, Zn, Sr and Pb with respect to Ca, attr!
ibuted to partial hydroxyapatite dissolution and/or to chelate extraction and concentration of trace metals. Ca maps revealed limited changes in the surface layer and a massive loss in the inner enamel; here, Fe was almost depleted and Zn partially removed. The maps of Ca, Fe and Zn demonstrated major intercusp variations in both normal and altered enamel. Thus, broad-beam PIXE and mu-PIXE, which do not require (semi)thin sectioning of the tooth as the conventional methods, provide compositional and structural insight of normal dental enamel, of its intercusp variability and of the alterations produced by ill vitro demineralization, largely not accessible to the current techniques, and highly relevant for understanding the incipient caries formation.

Dipole transitions from J = 1+ and 1- states in 26Mg were studied by means of photon scattering. The 1+ and 1- states were excited with bremsstrahlung produced by an electron beam of 13.0 MeV kinetic energy provided by the superconducting electron linear accelerator ELBE. We determined the transition strengths from 1+ and 1- states to the ground state as well as to low-lying states. In addition, we observed a J = 1 state at 11.154 MeV, above the neutron-separation energy of 11.093 MeV, and determined its partial gamma decay width for the first time.

Our group has synthesized technetium labeled fatty acids which are extracted into the myocardium and sequestered due to H-FABP binding. In this paper we further address the detailed subcellular distribution and potential myocardial metabolism of "4+1" ^99mTc-fatty acids (FA).

Experiments were conducted using isolated hearts of wistar rats as well as wildtype and H-FABP^-/--mice. Myocardium samples underwent subcellular fractionation (subsarcolemmal and intermyofibrillar mitochondria, cytosol with microsomes as well as nuclei and crude membranes) and analysis by TLC and HPLC.

The largest fraction of tissue radioactivity was associated with the cytosol (79.69 ± 8.88% of the infused dose =ID). 9.07 ± 0.95% and 3.43 ± 1.38% of the ID were associated with the subsarcolemmal and the intermyofibrillar mitochondrial fractions, respectively. In the rat heart, etomoxir, an inhibitor of the carnitin-palmitoyl transferase I, did not significantly decrease radioactivity associated with the mitochondrial fractions, whereas the myocardial extraction of ¹²³I-IPPA (13.26% vs. 49.49% in control) and the radioactivity associated with the subsarcolemmal and the intermyofibrillar mitochondrial fractions was blunted. The percentage of the ID in the mitochondrial and crude fractions increased with the number of NH-amide groups of the FA derivative. Absence of H-FABP significantly decreased the radioactivity count in the cytosolic fraction (P < 0.001). No metabolic products of a ^99mTc "4+1" FA could be detected in any isolated hearts. Myocardial ^99mTc "4+1" FA extraction reflects binding to H-FABP and membrane structures (including the mitochondrial membrane). However, the compounds do not undergo mitochondrial metabolism, because they do not reach the mitochondrial matrix.

¹³C, ¹⁸F and ¹²³I fatty acids (FA) are used for myocardial imaging. Recently, our group showed that ^99mTc-labeled "4+1" FA are extracted into the rat and guinea pig myocardium. The present study evaluates determinants of myocardial uptake and whole body biodistribution of these FA derivatives. Studies were performed with isolated perfused hearts of Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) with a FAT/CD36 deficiency, as well as with heart type FA binding protein knockout mice (H-FABP^-/-) and H-FABP^+/+. Eight "4+1"-^99mTc- FA were applied for 3 min followed by 1 min washout. A mathematical model was used to analyze FA dynamics and binding to proteins. Whole body distribution was studied in rats with and without Tween 80. In vitro fractionation studies with ^99mTc- FA assessed red blood cell uptake as well as association with plasma lipoproteins (VLDL, LDL and HDL). Myocardial extraction was 19.0-33.0 % of the infused dose in isolated WKY and 15.2-26.4 % in SHR hearts. However, H-FABP^-/- showed a marked reduction of tracer extraction (2.8 ± 0.6%ID vs. 17 ± 2%ID P < 0.001). Uptake in red blood cells (< 1.2%ID) and incorporation into lipoproteins were negligible. Incubation of ^99mTc-FA with albumin reduced ventricular extraction (P < 0.001) into the range of established iodinated FA tracers. Tween 80 improved the heart-to-liver ratio in the biodistribution studies. Myocardial uptake of "4+1"-^99mTc- FA derivatives is dependent on H-FABP. These substances may therefore provide a new tool to specifically assess regional myocardial changes of H-FABP.

Development and application of new expedient aluminium-based light alloys are a key issue in current materials science. In this study we present measurements of the thermophysical properties of liquid Al-7wt%Si, AlSi7Mg, and AlSi8Cu3 (wt.%) alloys, which are the most utilized casting alloys in the aluminium industry. Experimental data with respect to the density, viscosity, electrical and thermal conductivity have been determined in a wide temperature range and corresponding fit relations have been derived. A comparison with already published data and scaling relations available in the literature is given.

This paper describes laboratory experiments for investigations of flow structures and related transport processes in liquid metal bubbly flows under the influence of a travelling magnetic field (TMF). The melt flow is driven by central gas injection into a cylindrical container filled with the low melting point alloy GaInSn. Velocity fields of both the liquid and the gaseous phase were measured non-intrusively using the ultrasound Doppler method. Depending on the travelling direction of the magnetic field, the TMF mainly imposes either a co-current or counter flow with respect to the original bubble-driven circulation. In general, the application of a downward TMF significantly increases the liquid velocity all over the fluid volume. An upward TMF gives rise to more complex structures of the velocity field resulting in alternately arranged up- and downstream regions. Both the upward and downward TMF promote the occurrence of non-steady motions with distinct velocity fluctuations leading to an intensification of related transport processes in the melt and providing the perspective of enhanced mixing efficiencies.

In this presentation I will talk about recent development of the high-field Electron Spin Resonance program at the Dresden High Magnetic Field Laboratory (HLD) in Rossendorf. A unique feature of the facility is a combination of an extraordinary broad frequency range, 9 GHz - 100 THz (quasi-continuously covered by a number of tunable-frequency radiation sources, including THz-range free-electron laser FELBE) and high magnetic fields (up to 60 T). The talk will be illustrated by tunable-frequency ESR results obtained in sine-Gordon chain material Cu-PM and BEC candidate NiCl₂-4SC(NH₂₂ (known as DTN).

investigated by uranium LIII-edge EXAFS and HEXS measurements with the aim to distinguish monodentate and bidentate coordinated sulfate in aqueous solution. UV-vis absorption spectroscopy has been used to differentiate the species and to determine the species distribution as a function of the [SO42−]/[UO22+] ratio. A monodentate coordination prevails in solutions with [SO42−]/[UO22+] ratio of 1, where UO2SO4 is the dominant species. Besides the dominating monodentate sulfate a small amount of bidentate sulfate could be observed, indicating that two isomers may exist for UO2SO4. With increasing [SO42−]/[UO22+] ratio the UO2(SO4)2 2− species becomes the main species. The uranium atom of this species is coordinated by two bidentate sulfate groups.

Hydrogen is an important impurity in zinc oxide and can be incorporated into the lattice in several ways. Hydrogen can be also bound by vacancies that can be studied using positron annihilation techniques. Here we examine theoretically oxygen and zinc vacancies in ZnO, the latter also with hydrogen atoms inside. Several computational approaches are employed to determine the defect geometries and related positron characteristics. Positron-induced forces are also taken into account. Calculated positron lifetimes are compared with those observed in experiment, which gives an indication of the presence of zinc vacancy-hydrogen complexes in ZnO materials.

In this contribution we report on the theoretical study of basic vacancy-like defects in cubic zirconia and yttria stabilized zirconia. In particular, we concentrate on oxygen vacancy, zirconium vacancy and oxygen vacancy – yttrium complex. Relaxed atomic configurations of studied defects are obtained by means of an ab initio pseudopotential method within the supercell approach. Positron characteristics, like positron lifetime and binding energy to defects, are calculated using self-consistent electron densities and potentials taken from ab initio calculations.

Vertraulicher Abschlussbericht

Auftraggeber: LMBV mbH
Auftragnehmer: Verein für Kernverfahrenstechnik und Analytik Rossendorf e.V.

Leistungszeitraum: 01.04.2006 - 31.08.2008

Platinum oxide and platinum thin films have been grown by atomic layer deposition (ALD) using Pt(acac)₂ (acac ) acetylacetonato) and ozone as precursors. Amorphous platinum oxide thin films were deposited at 120 and 130 °C while metallic platinum films were obtained at 140 °C and above. The sublimation temperature of Pt(acac)₂ set the low temperature limit for oxide film deposition. The platinum oxide films were successfully deposited on Al₂O₃ and TiO₂ adhesion layers, soda lime glass, and silicon substrate with native oxide on top. Platinum films were grown on Al₂O₃ adhesion layer. The platinum oxide had good adhesion to all tested surfaces, whereas metallic platinum films did not pass the common tape test. Resistivities of 50-60 nm thick platinum oxide films were between 1.5 and 5 Ω cm at 130 °C and could be varied with both precursor pulse lengths. The resistivity of about 110 nm thick metallic film deposited at 140 °C was about 11 μΩ cm. The platinum films deposited at higher temperatures suffered from deterioration of thickness uniformity. The platinum oxide films can be reduced in 5% H₂ gas under reduced pressure at room temperature to porous platinum structures.

The Forschungszentrum Dresden-Rossendorf provides an intense pulsed 40 MeV electron beam with high brilliance and low emittance (ELBE). The pulse has a length of 1-10 ps and a repetition time of 77 ns, or in slow mode 616 ns. The EPOS system (ELBE Positron Source) generates by pair production on a tungsten converter and a tungsten moderator an intense pulsed beam of mono-energetic positrons. To transport the positrons to the laboratory (12 m) we constructed a magnetic beam guidance system with a longitudinal magnetic field of 75 G. In the laboratory outside the cave, the positron beam is chopped and bunched according to the time structure, because the very sharp bunch structure of the electron pulses is broadened for the positron beam due to transport and moderation.

Electrochemical and complexation properties of neptunium are investigated in aqueous perchlorate and nitrate solutions by means of cyclic voltammetry, bulk electrolysis, UV-visible absorption, and Np LIII-edge X-ray absorption spectroscopy. The redox reactions of Np(III)/Np(IV) and Np(V)/Np(VI) couples are reversible or quasi-reversible, while the electrochemical reaction between Np(III)/(IV) and Np(V)/(VI) is irreversible because they undergo structural rearrangement from spherical coordinating ions (Np3+ and Np4+) to trans-dioxoneptunyl ions (NpO2n+). The redox reaction of the Np(V)/Np(VI) couple involves no structural rearrangement on their equatorial planes in acidic perchlorate solutions. A detailed analysis of EXAFS spectra suggests that Np(IV) forms a decaaquo complex of [Np(H2O)10]4+ in 1.0 M HClO4, while NpV and NpVI exist dominantly as pentaaquoneptunyl complexes, [NpO2(H2O)5]n+ (n = 1 for Np(V) and 2 for NpVI) [1].
Structural information on the sulfate coordination of neptunium in aqueous solution is actually rather scarce. We investigated actinide complexes in aqueous sulfate solution by using samples of 10-50 mM of actinide and total sulfate concentrations, 0.05 ≤ [SO42-] ≤ 10 M. In contrast to the coordination of actinides with carbonate where bidentate coordination always prevails, the coordination with sulfate comprises monodentate and bidentate linkage with a wide variety of combinations. In general, with increasing [SO42-]/[Ann+] ratio the bidentate coordination becomes dominant in solution [2]. As example, at low [SO42-]/[UO22+] ratio, where the UO2SO4(aq) species prevails, the sulfate coordinates in a monodentate and only to a less extend in bidentate fashion. At high [SO42-]/[UO22+] ratio, where UO2(SO4)22- species prevails, bidentate sulfate coordination with the species [UO2(SO4)2bid]2- becomes dominant. In oxidation state IV, up to five coordinating sulfate groups have been observed, mostly with predominant bidentate coordination as for example in the high-charged complex [U(SO4bid)3(SO4mon)2]6- [3]. Np(IV) and Np(VI) follows the tendency of U(IV) and U(VI), whereas Np(V) is weakly coordinated by sulfate, in accordance with its low formation constant. The attempt to preserve solution species in crystal structures led in most of the cases to a rearrangement of bidentate sulfate groups in solution to monodentate–bridging coordination in solid state. The coordination of the solution complexes was optimized by DFT calculation and the results are compared with the experimental observations.

A well known tool in conventional (von Neumann) quantum mechanics is the selfadjoint extension technique for symmetric operators. It is used, e.g., for the construction of Dirac-Hermitian Hamiltonians with point-interaction potentials. Here we reshape this technique to allow for the construction of pseudo-Hermitian (J-selfadjoint) Hamiltonians with complex point-interactions. We demonstrate that the resulting Hamiltonians are bijectively related with so called hypermaximal neutral subspaces of the defect Krein space of the symmetric operator. This symmetric operator is allowed to have arbitrary but equal deficiency indices . General properties of the C-operators for these Hamiltonians are derived. A detailed study of C-operator parametrizations and Krein type resolvent formulas is provided for J-selfadjoint extensions of symmetric operators with deficiency indices <2,2>. The technique is exemplified on 1D pseudo-Hermitian Schrödinger and Dirac Hamiltonians with complex point-interaction potentials.

Besides low-temperature molecular beam epitaxy, ion implantation provides an alternative route to incorporate Mn into GaAs above the equilibrium solubility limit. However, post-implantation annealing can lead to the formation of secondary phases. In the published papers concerning Mn implanted GaAs, diluted magnetic GaAs is only obtained by pulsed laser annealing. In order to compare the post-annealing effect, we investigate GaMnAs by implanting up to 6 at% Mn followed by rapid thermal and flashlamp annealing. The structural properties were probed by high resolution X-ray diffraction. The magnetic properties were determined by SQUID measurements. Auger electron spectroscopy has been used to profile the depth distribution of Mn in GaAs after implantation and annealing. We elucidate after implantation a loss of As and that during rapid thermal annealing most of the Mn diffuses towards the surface. Flash lamp annealing prevents out-diffusion, but the recrystalisation effciency is low. Only the flash lamp annealed samples reveal weak ferromagnetism.

The presentation reported latest results about defect engineering of the SIMOX process

A cavity layer or nano-bubble layer introduced by He implantation before the oxygen implantation collects the implanted oxygen and increases the oxygen concentration. The average size and density of the oxygen precipitates formed in the initial stage of the Separation-by-implanted-oxygen (SIMOX) process is conform with the size and density of the cavities pre-formed by He implantation and annealing. The gettering ability of the cavity layer for oxygen is directly related to the area of the internal surface of the cavities. A nano-bubble layer accumulates oxygen in a very narrow range occurring between the damage maximum, DP, and the mean projected ion range, RP. Such a nano-bubble layer is most efficient in oxygen gettering due to their larger area of the internal surface and the small size of the oxide precipitates initially formed at the bubbles.

One-step device fabrication through the integration of nanowires (NWs) into silicon microchips is still under intensive scientific study as it has proved difficult to obtain a reliable and controllable fabrication technique.
So far, the techniques are either costly or suffer from small throughput. Recently, a cost-effective method based on thin-film fracture that can be used as a template for NW fabrication was suggested. Here, a way to integrate NWs between microcontacts is demonstrated. Different geometries of microstructured photoresist formed by using standard photolithography are analyzed. Surprisingly, a very simple ‘‘stripe’’ geometry is found to yield highly reproducible fracture patterns, which are convenient templates for fault-tolerantNWfabrication. Microchips containing integrated Au, Pd, Ni, and Ti NWs and their suitability for studies of conductivity and oxidation behavior are reported, and their suitability as a hydrogen sensor is investigated. Details of the fabrication process are also discussed.

In this paper we show that spinel ferrite nanocrystals (NiFe2O4, and CoFe2O4) can be texturally embedded inside a ZnO matrix by ion implantation and post-annealing. The ferrite nanocrystals show comparable magnetization with corresponding bulk ferrites. Anomalous Hall effect and positive magnetoresistance have been observed. Our study suggests a ferrimagnet/semiconductor hybrid system for potential applications in magneto-electronics. This hybrid system can be tuned by selecting different transition metal ions (from Mn to Zn) to obtain various magnetic and electronic properties.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

NiCl2-4SC(NH2)2 (known as DTN) is a quantum S = 1 chain system with strong easyplane anisotropy that is regarded as a new candidate for the Bose-Einstein condensation (BEC) of spin degrees of freedom, with critical fields B_c1 = 2.1 T and B_c2 = 12.6 T. Tuneable-frequency Electron Spin Resonance (ESR) studies of magnetic excitations in DTN in fields up to 25 T are presented. Based on analysis of the single-magnon excitation mode observed in the high-field spin-polarized phase1 and previous experimental results2, a revised set of spin-Hamiltonian parameters is obtained. Our results yield D = 8.9 K, J_c = 2.2 K, and J_a,b = 0.18 K for the anisotropy, intrachain, and interchain exchange interactions, respectively. These values are used to calculate the antiferromagnetic phase boundary, magnetization and the frequency-field dependence of two-magnon bound-state excitations predicted by theory3 and observed in DTN for the first time. Furthermore, we present a systematic study of the low-energy excitation spectrum of DTN in the fieldinduced magnetically ordered phase (which is regarded as the magnon BEC phase) at temperatures down to 0.45 K. We argue that two gapped modes observed in the experiment4 can be consistently interpreted within a four-sublattice antiferromagnet model with a weak isotropic corner-center interaction of magnetic ions in the body-centered tetragonal lattice with unbroken axial symmetry. The latter is of particular importance, being a necessary prerequisite for the interpreting of the antiferromagnetic ordering in DTN in terms of the BEC scenario. The physically simplest scenario would correspond to the isotropic "corner-center" exchange. Since the exchange interaction within each sublattice is antiferromagnetic, the ground state in DTN in the ordered state (B_c1 < B < B_c2) is predicted to be frustrated and thus infinitely degenerated.

kein Abstract verfügbar

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

Aim:

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

Materials and methods:

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

Conclusion:

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

Aim:

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

Material and Methods:

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

Results:

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

Conclusions:

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

Aim:

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

Materials & Methods:

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

Results:

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

Aim:

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

Method:

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

Conclusion:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Aim:

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

Patients, methods:

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

Results:

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

Conclusion:

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

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

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

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

es hat kein Abstract vorgelegen!

We have investigated the evolution of ferromagnetic order in the correlated metal URhGe (Curie temperature T_C = 9.5K) by chemical substitutionof Ru, Co and Si. Polycrystalline samples URh_1−xRu_xGe (x ≤ 0.6), URh_1−xCo_xGe (x ≤ 0.9) and URhGe_1−xSi_x (x ≤ 0.2) have been prepared and the magnetic properties have been investigated by magnetization and transport experiments. In the case of Ru doping, T_C initially increases, but then decreases linearly as a function of x and is completely suppressed for x_cr ≈ 0.38. The Curie temperature in the URh_1−xCo_xGe series has a broad maximum T_C = 20K near x = 0.6 and then drops to 8K for x = 0.9. In the case of Si doping T_C stays roughly constant. We conclude that the alloy systems URh_1−xRu_xGe and URh_1−xCo_xGe are interesting candidates to study the ferromagnetic instability.

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

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

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

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

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

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