Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Due to the high uniaxial anisotropy L10-ordered FePt is currently the most favored candidate for future high density storage applications. With respect to a feasible fabrication technology, it is necessary (i) to produce such films on amorphous substrates, and (ii) to enable a low processing temperature (T<400°C). FePt films deposited at RT only exhibit the face-centered cubic A1-phase. Thus, either deposition or a post-deposition heat treatment at temperatures above typically 500°C is required, in order to achieve the L10-phase. We report on the L10 ordering of stoichiometric FePt thin films fabricated on SiO2/Si substrates by magnetron sputtering at various temperatures (RT - 400°C). Using a low deposition rate of about 0.6 Å/s and an Ar pressure of 0.3 Pa the ion/atom-ratio during deposition is » 1 where the ions exhibit energies of about 20 eV. In addition, FePt films have been irradiated subsequently with He ions of 50 keV and fluencies between 1x1015 and 3x1016 cm−2 for comparison. The kinetics of A1-L10 transition and ordering have been investigated with in-situ X-ray diffraction at the Synchrotron-beamline ROBL at ESRF. L10 ordered FePt films with an ordering parameter S=0.8 have been achieved already for an overall process temperature below 350°C. The results are discussed in terms of ion-assisted activation and segregation which supports the atomic relocation during L10 ordering.

Bakterien waren die ersten Lebewesen auf unserem Planeten. Über die Jahrmilliarden haben sie gelernt, sich an jeden noch so unwirtlichen Lebensraum anzupassen und nahezu jede noch so komplexe chemische Verbindung abzubauen. Fälschlicherweise haben sie sich insbesondere als Krankheitserreger einen „Namen“ gemacht. Bei genauerer Beschäftigung mit diesen kleinsten Lebewesen wird nämlich schnell klar, dass es sich dabei nur um Ausnahmeerscheinungen handelt. Nach vorsichtigen Schätzungen kennt man zwar nur etwa 1 % aller Bakterien, aber es ist unumstritten, dass nur durch ihre Aktivität das Leben in seiner heutigen Form möglich geworden ist. Neben ihrem fundamentalen Beitrag zur Entstehung der heutigen Atmosphäre und damit der Grundlage unseren Lebens, sorgen sie außerdem dafür, dass die Kreisläufe der Natur nicht zum Erliegen kommen.
Der Vortrag soll dazu einen Überblick geben und am Beispiel ungewöhnlicher Leistungen sowie besonderer Eigenschaften der Bakterien deren Anwendungspotential vor dem Hintergrund der Arbeiten am Forschungszentrum Rossendorf aufzeigen.

The substrate/interface morphology and roughness plays a crucial role for the determination of the magnetic properties of ultrathin films. An anisotropic roughness can easily create magnetic anisotropy contributions of the same symmetry. It will be demonstrated that ion erosion fabricated ripples can be used to tailor the magnetic anisotropy and lead to a dramatic enhancement of the uniaxial magnetic anisotropy of Permalloy by a factor of up to 20.
By means of 500 eV Ar+ ion erosion a rippled Si surface with a well defined periodicity (20 – 60 nm) and peak to valley height (2 – 5 nm) is created. The surface topography is investigated by means of atomic force microscopy. On top of this naturally oxidized surface, first a metallic buffer layer and then a 9 nm thin Permalloy layer is deposited by means of thermal evaporation. Depending on the buffer layer material (Cr, Mn, Pt, Cu) and thickness (0 – 20 nm) the ripple morphology is reproduced to a variable extent by the Permalloy film. The magnetization reversal behavior and the ripple-induced magnetic anisotropies are investigated by means of magneto-optic Kerr effect measurements and correlated to the interface morphology. An easy route for the tailoring of magnetic anisotropies is shown.

The layer magnetization, the saturation magnetization as well as the magnetic anisotropy and damping behavior of 20 nm thick Ni81Fe19 films have been modified by 30 keV Cr, Ni and Co ion implantation with fluences up to 11016 ions/cm2 ( 5 atom-%). As a function of fluence first an improvement of the (111) fiber texture, then a lattice expansion and finally a partial amorphization of the interface near region of the Ni81Fe19 layer is found. The region of amorphization can be understood quantitatively by the concentration profiles as a function of depth in combination with irradiation induced damage formation. The magnetic properties change correspondingly. Magneto-optic Kerr effect magnetometry and inductive techniques have been used to determine the layer magnetization and the static magnetic anisotropy. A strong reduction of the magnetization with increasing implantation fluence is found. This reduction can be decomposed in a reduction of the active magnetic layer thickness and a reduction of the saturation magnetization. The latter one has been determined by means of pulsed inductive microwave magnetometry. This technique allows in addition the determination of the dynamic anisotropy, the relaxation rate and the magnetic damping constant. A reduction in magnetic anisotropy and a strong increase of the magnetic damping behavior is observed as a function of implantation fluence which is mainly attributed to doping effects. However, also radiation induced damage effects have to be considered in order to fully understand the change in magnetic properties.

The magnetic properties of both interacting and non-interacting iron nanoparticle systems were investigated by means of SQUID magnetometry. Both nanoparticle systems were produced by ion beam synthesis. For this purpose Fe+ was implanted into diamagnetic LaAlO3 substrates with a fluence of 6×1016 cm-2 at an energy of 120 keV at either 400°C or 800°C. It is observed that for the lower (higher) temperature a non-interacting (interacting) nanoparticle ensemble is created. The size distribution of the nanoparticles is studied by transmission electron microscopy. The memory effects in these systems were investigated by field-cooling and zero field-cooling magnetization measurements. Both analysis methods should help to settle the controversy whether the interaction between superparamagnetic particles or their size distribution is responsible for the memory effect [1, 2].

[1] Y. Sun et al., Phys. Rev. Lett. 91, 167206 (2003).
[2] R. K. Zheng et al., Phys. Rev. Lett. 93, 139702 (2004).

Laser pulse induced field assisted precessional switching in exchange coupled mesoscopic NiFe/FeMn striplines has all-optically been triggered and magneto-optically observed in real time with switching times down to 500 ps. A fast decoupling of the exchange bias bilayer launches coherent precession of the magnetization of the ferromagnetic layer of the exchange bias system. By properly choosing the initial equilibrium orientation the optical unpinning of the bilayer can induce complete magnetization switching. Stroboscopic time domain imaging of the switching event has been realized by a sophisticated synchronization scheme of a magnetic preset pulse and both the optical pump and probe pulses, respectively. The observed laser assisted switching can be well described by the Landau-Lifshitz-Klaasen-van Peppen equation combining precessional and thermally activated spin dynamics.

Recently ion irradiation has been proposed as a patterning tool for different magnetic systems. The increasing interest for this technique is due to the capability of tailoring the magnetic properties without affecting the sample topography. We present a study of the magnetic properties of patterns with different geometries produced by ion irradiatio on a Ni81Fe19/Fe50Mn50 exchange bias bilayer by magneto-optic Kerr effect (MOKE) magnetometry and magnetic force microscopy (MFM). The hysteresis loops measured by MOKE present features evidently related to the irradiated geometries. Moreover they also reveal that the magnetization reversal is not proceeding independently in irradiated and non-irradiated areas. This magnetic coupling is confirmed by MFM images, which clearly show that magnetic domains in irradiated and non-irradiated elements are mutually influencing each other during the reversal process. Comparison with previous studies indicates that the above mentioned coupling dramatically affects the reversal process only when the lateral size of irradiated elements approaches a characteristic coupling length.

Diluted magnetic semiconductors (DMS) are based on common semiconducting material like GaAs, Si, Ge, InP, GaN or ZnO doped with a few percent of a transition or rare earth metal. While early work has been performed mainly by polish groups in the 1970ies and 80ies, DMS have attracted worldwide scientific attention during the last 5 years due to their application potential in spintronics. This was triggered by the discovery of ferromagnetic GaMnAs and the theoretical prediction of room temperature ferromagnetism for ZnO:Mn and GaN:Mn by T. Dietl and H. Ohno [1]. One of the main obstacles while creating a DMS is secondary phase formation. Since solubility limits are rather low, non-equilibrium doping techniques like low temperature film growth are commonly used. On the other hand, ion implantation offers superb possibilities for low temperature doping but is always connected with lattice damage of the target material. Combining ion implantation with another non-equilibrium technique, i.e. rapid thermal annealing, leads to a diluted state while the crystallinity of the target material is restored. This has been shown for Si:Mn [2].
Recently, we investigated the secondary phase formation for Fe,Co and Ni as well as Gd, Tb implanted in ZnO single crystals. We found, that at an implantation temperature of 623 K tiny superparamagnetic nanoparticles are formed in all transition metal (TM) doped samples. These phases can hardly be identified using lab X-ray diffraction (XRD), e.g. in the case of Fe. Only application of high resolution methods like synchrotron XRD, susceptometry, Mössbauer spectroscopy and transmission electron microscopy allows their identification [3]. On the other hand, rare earth implanted samples show a diluted state up to annealing temperatures of 823 K. For both ZnO:Tb and ZnO:Gd a ferromagnetic order was found. Low temperature TM implantation (253 K) leads to a 100% diluted state. The TM-ions however do not couple magnetically that can be caused by the lattice damage introduced due to the implantation. Very rapid thermal processing using flash lamps with 20 ms pulse width leads to a significant recovery of the lattice order, while only a small amount of nanoparticles is created.

Reference
[1] T. Dietl, et al., Science 287, 1019 (2000).
[2] M. Bolduc, et al., Phys. Rev. B 71, 033302 (2005).
[3] K. Potzger, et al., Appl. Phys. Lett. 88, 052508 (2006).

Ziel/Aim:

In klinischen PET Scannern ist das räumliche Auflösungsvermögen durch physikalische Größen wie der Gantry und der Kristallgröße (zur Zeit 4 x 4 mm) limitiert. Dagegen ist im Tier-PET das räumliche Auflösungsvermögen durch eine kleine Gantry und eine geringere Kristallgröße (2 x 2 mm) erhöht, sodaß dem Einfluß der mittleren freien Weglänge der Positronen bei Verwendung unterschiedlicher Nuklide für die Entwicklung neuer PET Radiopharmaka eine erhebliche Bedeutung zukommen könnte.

Methodik/Methods:

Es wurden bei 3 Radionukliden (F-18, O-15, Ga-68) je 2 Phantommessungen durchgeführt. Die Messungen erfolgten mit einem MOSAIC PET Scanner der Firma Philips an dem Tier-PET Phantom 50/106 der Firma BS Industrieelektronik & Medizintechnik. Das Phantom hat insgesamt 298 Kanäle mit Durchmessern in Stufen von 1,0 mm, 1,5 mm, 2,0 mm, 2,5 mm und 3,0 mm. Die Phantommessungen wurden ohne Schwächungskorrektur mit 0,5 mm Auflösung und unterschiedlichen Methoden (3D Ramla, Ramla, Iterativ, Butterworth-FTB, Gaussian-FTB, Hanning-FTB) rekonstruiert. Zuerst wurde das Auflösungsvermögen bei F-18, O-15 und Ga-68 visuell verglichen. Es wurde dann beim kleinsten gemeinsamen Auflösungsniveau jeweils der mittlere Kontrast (Differenzsignal/Hintergrundsignal) für die obengenannten Rekonstruktionen ermittelt.

Ergebnisse/Results:

Visuell konnten mit F-18 noch 1,5 mm Kanäle, mit O-15 und Ga-68 2,0 mm Kanäle aufgelöst werden, es ergab sich kein nennenswerter Unterschied bezüglich der jeweiligen Rekonstruktionsmethode. Die Kontrastermittlung erfolgte daher bei 2,0 mm Kanaldurchmesser. Hingegen wurde beim semiquantitativen Vergleich der verschiedenen Rekonstruktionsverfahren der höchste Kontrast für jedes Nuklid mit 3D Ramla erzielt. Die mittleren Kontraste für die Rekonstruktion mit 3D Ramla lag bei 1,36 für F-18, bei 1,23 für O15 und bei 0,78 für Ga-68.

Schlussfolgerungen/Conclusions:

Die Phantommessungen im Tier-PET zeigen zum einen eine deutliche Abhängigkeit von Auflösung und Kontrast vom jeweiligen Rekonstruktionsverfahren, wobei der Rekonstruktionsparameter 3D Ramla die besten Ergebnisse erzielte. Zum anderen wurde der Einfluss der mittleren freien Weglänge des jeweiligen Isotops auf die Auflösung demonstriert. Beide Einflussgrößen müssen bei der Anwendung eines Tier-PETs für die zu erreichende Auflösung berücksichtigt werden.

Ziel/Aim:

Die MIRDDOSE Annahme einer 50% zu 50% Verteilung knochenaffiner Radiopharmaka im kortikalen und der trabekulären Knochen sowie einer homogene Anreicherung in den Knochenmetastasen dürfte nicht den reellen Verhältnissen entsprechen.

Methodik/Methods:

Ein Modell zur Induktion von osteoblastischen Knochenmetastasen wurde durch intra-ossäre Injektion von Prostata-Karzinomzellen bei Kopenhagenratten in einer Vorversuchsserie entwickelt. In histologischen Untersuchungen konnte das Vorliegen von osteoblastischen Knochenmetastasen bewiesen und diese szintigraphisch dargestellt werden.

Bei 45 Kopenhagenratten (Alter: 9 ± 2 Monate, Gewicht: 318 ± 22g) wurden jeweils 100.000 R3327 Mat-Ly-Tu Zellen in beide Femura injiziert. Ab dem 12. Tag nach Zellapplikation war makroskopisch ein Tumor gut sichtbar. 17 ± 1 Tage nach Tumorzellapplikation erfolgte die Applikation von 134 ± 53 MBq Re-188-HEDP sowie nachfolgend die Tötung von jeweils 15 Tiere 4, 24 und 48 Stunden. Coronare Gefrierschnitte (Cryopolycut, Leica, 40 #mikro#m dick) wurden autoradiographisch mit einer Auflösung von 0,5 #mikro#m (BAS 500, Fuji) untersucht. Mittels ROI-Technik erfolgte die Bestimmung der Anreicherung des Re-188-HEDP pro mm3. Nachfolgend wurden die Verhältnisse zwischen Tumor und normaler Knochen (T/NT) berechnet, sowie die Verteilung im kortikalen und der trabekulären Knochen quantifiziert.

Ergebnisse/Results:

Es zeigte sich eine Verteilung im kortikalen und der trabekulären Knochen von 33,5% zu 66,5% nach 4h, von 34,6% zu 65,4% nach 24h und von 35,9% zu 64,1% nach 48h (p = 0,788 bis 0,871). In den Knochenmetastasen zeigte sich eine stark inhomogene Anreicherung mit einer minimalen und maximalen T/NT von 3:1 und 14:1 nach 4h, von 5:1 und 14:1 nach 24h sowie von 5:1 und 16:1 nach 48h, der Anstieg über die Zeit ist nicht signifikant. Die maximale Anreicherung in einer Metastase betrug 22:1. Bei erneuter Berechnung der Knochenmarkdosis aus vorliegender Daten einer Rhenium-188-HEDP Therapie beim Menschen, ergab sich bei einer Zugrundelegung einer Verteilung von 35% zu 65% (kortikal zu trabekulär) eine um 135% höhere Dosis als bei einer Verteilung von 50% zu 50%.

Schlussfolgerungen/Conclusions:

Das MIRDOSE Schema unterschätzt die reelle Dosis im Knochenmark. Die stark inhomogene Anreicherung in den Knochenmetastasen führt zu einer inhomogenen Dosisverteilung in den Metastasen, bei Anwendung von Betastrahlern mit einer höheren Beta-Energie lässt sich eine homogenere Dosisverteilung erreichen.

Ziel/Aim:

Dynamische PET-Studien mit FDOPA erlauben die Beurteilung des striatalen Dopamin-Uptakes und sind damit ein wichtiges Werkzeug in der Diagnose des Morbus Parkinson. Diese Aufnahmen erfordern typischerweise Akquisitionszeiten von ein bis zwei Stunden während deren die Patientenbewegung nicht vollständig vermieden werden kann. Diese Bewegung kann die Analyse der Tracerkinetik stark beeinträchtigen oder gar unmöglich machen. Ziel dieser Arbeit ist eine routinetaugliche Methode um die Patientenbewegung in den PET-Volumina zu korrigieren. Dazu stellen wir eine Methode zur Bewegungskorrektur vor, die auf der vollautomatischen Koregistrierung der dynamischen Studien beruht.

Methodik/Methods:

Es wurden 33 dynamische FDOPA Studien koregistriert und bezüglich der Effekte der Patientenbewegung untersucht. Die Koregistrierung basiert auf starren Transformationen, wobei die besten Transformationsparameter durch Maximieren der Mutual Information (MI) erhalten werden. Die Maximierung der MI erfolgt mittels der Methode der konjugierten Gradienten. Alle Frames der dynamischen Studien wurden gegen das letzte Frame der jeweiligen Studie vollautomatisch koregistriert. Der FDOPA-Uptake im Striatum wurde in den unkorrigierten und in den korrigierten Daten mit einem Referenz-Tissue Zwei-Kompartment Modell bestimmt. Zum einen wurden aus den dynamischen Studien parametrische Bilder erstellt, aus denen sich der FDOPA-Uptake ermittelt lässt. Zum anderen ergab sich der Uptake aus den Zeitaktivitätskurven der in den parametrischen Bildern festgelegten ROIs. Die Ergebnisse für unkorrigierte und bewegungskorrigierte Bilddaten wurden verglichen.

Ergebnisse/Results:

In 16 der 33 Studien führte die Patientenbewegung zu Artefakten in den parametrischen Bildern und zu einem bis zu 70 % über- bzw. unterbewerteten FDOPA-Uptake im Striatum. Dieser Effekt war auch in den Zeitaktivitätskurven deutlich sichtbar. Die angewandte Koregistrierung vermochte in allen untersuchten Studien die Patientenbewegung zu korrigieren. Das verwendete Programm benötigte ca. 10 min. Rechenzeit je Studie (21 Frames) auf einem durchschnittlichen Computersystem. Studienabhängige Einstellungen von Registrierungsparametern waren hierbei nicht notwendig, was eine zuverlässige Stapelverarbeitung von Serien von Studien erlaubt.

Schlussfolgerungen/Conclusions:

Die robusten Ergebnisse und die einfache Handhabung erlauben einen routinemäßigen Einsatz dieser Bewegungskorrekturmethode.

Ziel/Aim:

Die Bestrahlungsplanung beruht auf einem komplexen Zielvolumenkonzept, dass die Tumorregion erfassen (gross tumor volumen,GTV), subklinische Tumorausdehnung beinhalten und Lagerungsinkonsistenzen zwischen den einzelnen Bestrahlungsfraktionen ausgleichen soll (planning target volumen, PTV). Der Einfluss der OMFD-PET auf die Bestrahlungsplanung von Hirntumoren wurde anhand folgender Fragen untersucht: Wurden mit OMFD-PET Tumorareale angezeigt, die nicht vom konventionell erstellten PTV erfasst wurden? Könnte das Einbeziehen von OMFD-PET in die Bestrahlungsplanung das PTV im Vergleich zur konventionellen Planung potenziell verkleinern?

Methodik/Methods:

Bei 30 Patienten mit malignen Hirntumoren wurde OMFD-PET nach subtotaler Resektion und vor Strahlentherapie durchgeführt. Die PET-Daten und soweit vorhanden prä- und postoperative T1-gewichtete MRT-Studien wurden retrospektiv mit dem Planungs-CT am Bestrahlungsplanungssystem Pinnacle 3 überlagert. Die Tumorareale im PET und Kontrastmittelanreicherung im MRT wurden als einzelne GTV markiert und in das Planungs-CT integriert. Es erfolgte der Vergleich der GTV-OMFD und GTV-MRTprä/post mit dem GTV-konv, das allein auf dem Planungs-CT und der visuellen Bildbeurteilung des MRT beruht.

Ergebnisse/Results:

Bei 28 von 30 Patienten war Tumorgewebe mittels OMFD-PET abgrenzbar. Ein Patient zeigte einen multifokalen Befall, so dass die primär kurative Therapieintention in ein palliatives Konzept geändert wurde. Alle im OMFD-PET abgrenzbaren Tumorregionen waren im konventionell erstellten PTV enthalten. Die mittleren Volumina betrugen 69,2 #±# 42,2ccm für das GTV-konv, 48,0 #±# 43,8ccm für das GTV-MRTprä, 16,8 #±# 15,5ccm für das GTV-MRTpost und 14,8 #±# 12,3ccm für GTV-OMFD. Der differentielle Vergleich der Volumina ergab, dass bei 5 von 29 Patienten mehr als 10 ccm der GTV-OMFD außerhalb des GTV-konv und bei 8 von 26 Patienten außerhalb des GTV-MRTpost lokalisiert waren. Bei 6 von 26 Patienten lagen mehr als 10ccm des GTV-MRTpost außerhalb des GTV-OMFD.

Schlussfolgerungen/Conclusions:

Die funktionelle Bildgebung von Hirntumoren mittels OMFD-PET detektiert relevantes Tumorgewebe außerhalb der im MRT detektierten Tumorregion und erbringt somit wichtige Informationen für die Abgrenzung des GTV für die Bestrahlungsplanung. Multimodale Strahlentherapieplanung beinhaltet das Potential die Hochdosisregion genauer abgrenzen und so möglicherweise die Ausdehnung des PTV begrenzen zu können.

Ziel/Aim:

This study investigates the effect of oligosaccharide derivatives on proliferation, metabolic activity and apoptosis of cultivated tumor cells. The effect of a complex oligosaccharide derivative of marine origin with anti-tumor activity has been compared with a defined trimeric oligosaccharide based on chitosan.

Methodik/Methods:

The human bladder carcinoma cell line EJ-28 was used as tumor model and compared to the human fibroblast cell line NHDF 6369. For quantification of the glucose metabolism [F-18]FDG-uptake was measured. The starting activity was 60 MBq in 10 ml culture medium. The cells were incubated for one hour. The incorporated activity was measured with a gamma counter. Further we studied the programmed cell death with flow cytometry. Early phase of apoptosis was detected by annexin staining and late phase by propidium iodide staining. The protein kinase inhibitor staurosporine was used as control substance in all experiments.

Ergebnisse/Results:

EJ-28 cells treated for 24 hours with oligosaccharide derivatives and chitosan trimers showed a decreased [F-18]FDG-uptake of about 50% in comparison to the untreated reference. On the other hand NHDF 6369 incubated by these agents showed an increased [F-18]FDG-uptake up to 150%. The protein kinase inhibitor staurosporine decreased the [F-18]FDG-uptake to 10% in both cell lines. Furthermore incubation for 24 hours increased the rate of apoptosis. Oligosaccharide derivatives and chitosan trimer were able to raise the rate of apoptosis in EJ-28 from 7% (6 h incubation) to 60% (24 h incubation). In NHDF 6369 cells the substances induced an increase of apoptosis rates from 15% (6 h) to 40% (24 h). Staurosporine increased the apoptosis rates from 20% (6h) to 65% in EJ-28 and 35% in NHDF 6369 (24h) in both cell lines, respectively.

Schlussfolgerungen/Conclusions:

Our data showed a reduced metabolic activity and increased apoptosis rates of cultivated tumor cells treated with oligosaccharide derivatives and chitosan derived trimers. The effects of chitosan trimers were comparable to the effects of the oligosaccharide derivatives of the marine nature material.

Ziel/Aim:

Er-169-Citrat-Kolloid (ERMM-1) wird in der Radiosynoviorthese eingesetzt. Die Mechanismen der Retention, des Abstroms und besonders die des lokalen Metabolismus der Kolloide in vivo sind noch nicht komplett verstanden. Deshalb sollte in vitro, unter definierten Bedingungen, ihr Diffusionsverhalten in der Gleichgewichtsdialyse, das Rückschlüsse auf die Größenverteilung der Kolloide und ihre Stabilität zulässt, untersucht werden.

Methodik/Methods:

Geträgertes Er-169-Citrat-Kolloid (fertiges Arzneimittel) und Filtrat des Er-169-Citrat-Kolloid (0,22 µm-Filter), welches die nanokolloidale Fraktion (Durchmesser kleiner 100 nm) enthält, wurden in einem Gleichgewichtsdialysesystem mit Synovia, verschiedenen Elektrolyt- und Pufferlösungen dialysiert (cut off der Membran 10000 Dalton). Die Zeit/Aktivitätsverteilung in den Dialysekompartimenten wurde für die einzelnen Präparationen bis zum Erreichen des Gleichgewichts untersucht. Als Referenzpräparate wurden Tl-201-Chlorid, F-18-FDG und Er-169-Chlorid verwendet.

Ergebnisse/Results:

Das ionische Erbium-169-Chlorid (Negativkontrolle) diffundiert praktisch mit der gleichen Kinetik wie die niedermolekularen Referenztracer. Die kolloidalen Er-169-Citrat Fraktionen zeigen bei Inkubation mit einer dem Plasma vergleichbaren Elektrolytlösung (MEM-Medium nach Dulbecco), humaner Synovia oder phosphathaltigen Puffern eine weitgehend fehlende Dialysierbarkeit, weniger als 0,5% der eingesetzten Aktivität werden dabei im Dialysemedium gefunden. Im Gegensatz dazu kommt es bei Inkubation mit physiologischer Natriumchloridlösung zu einer deutlichen Freisetzung von dialysierbaren Erbium (ca. 62%).

Schlussfolgerungen/Conclusions:

Das Verhalten der Kolloidpräparationen wird in erster Linie durch die Anwesenheit von Phosphationen erklärbar. Auf Grund sehr geringer Löslichkeit von Erbiumphosphat wird bei Inkubation der nanokolloidalen Fraktion mit Synovia und phosphathaltigen Puffern eventuell vorhandenes bzw. sekundär gebildetes ionisches Erbium ausgefällt. Dies führt zur Bildung neuer, sekundärer Erbium-Phosphat-Kolloide bzw. zur Stabilisierung und Wachstum bereits vorhandener Erbium-Citrat-Kolloide. Dieser Mechanismus der Stabilisierung der Kolloide durch Phosphationen scheint hauptsächlich für die Fixierung der Er-169-Aktivität in den Gelenken verantwortlich sein bevor die Kolloide durch die Deckzellen der Synovialis phagozitiert werden.

Ziel/Aim:

Die Radiotracer-Aufnahme von hypoxischen Arealen in solidem Tumorgewebe ist ein wichtiger Parameter für die Visualisierung von Tumoren mit PET. Das Ziel des vorgestellten Projekts ist die Bewertung von Endothelzellen hinsichtlich ihrer Radiotraceraufnahme unter hypoxischen Bedingungen.

Methodik/Methods:

Verschiedene humane primäre Endothelzellen aus der Nabelschnurvene (HUVEC), der Aorta (HAEC) und der Haut (HDMEC) wurden neben etablierten Tumorzelllinien FaDu und HT-29 verwendet. Experimentelle Hypoxie wurde mit einem speziellen Inkubator (Gasboy, Labotect, Göttingen) erzeugt. Nach 24h Kultivierung unter hypoxischen Bedingungen wurde die Expression der Gene HIF-1#alpha# und VEGF mit PCR analysiert sowie die Aufnahme der Radiotracer [Tc-99m]Sestamibi und [F-18]FDG gemessen.

Ergebnisse/Results:

Unter experimenteller Hypoxie wurde eine verstärkte Expression von HIF-1#alpha# sowie VEGF gemessen. Die Aufnahme von [Tc-99m]Sestamibi, einem Marker für die Intaktheit der Atmungskette, war in allen Zelltypen unter hypoxischen Bedingungen verringert. Die [F-18]FDG Aufnahme unter hypoxischen Bedingungen war sowohl von den verwendeten primären Endothelzellen als auch von Tumorzellen deutlich erhöht.

Schlussfolgerungen/Conclusions:

Primäre Endothelzellen nehmen wie Tumorzellen in Gegenwart von experimentell erzeugter Hypoxie vermehrt den Radiotracer [F-18]FDG auf. In vaskularisierten soliden Tumoren tragen Endothelzellen somit zur Anreicherung von Radiotracern bei und haben einen Einfluss auf die nachfolgende Bildgebung mit PET.

Ziel/Aim:

Peptidrezeptoren sind auf Grund ihrer gesteigerten Expression im Tumorgewebe für das molekulare Imaging von großem Interesse. Das molekulare und biochemische Verständnis dieser Rezeptoren wird für die Entwicklung repräsentativer Liganden via Radiomarkierung für die Tumordiagnose und Therapie genutzt. Die Charakterisierung der Neurotensin- Rezeptor (NTR) Familie als wichtiges Target für die Tumordiagnose und Therapie ist Gegenstand dieser Arbeit.

Methodik/Methods:

In der vorliegenden Arbeit wurde die Expression der NTR in kultivierten HT-29 (humanes Adenokarzinom) und FaDu ( humanes Plattenepithelkarzinom) Zellen sowie in den entsprechenden xenogenen Tumortransplantaten untersucht. Die mRNA Genexpression wurde mittels real-time PCR mit spezifischen Primern für die drei Rezeptorsubtypen quantifiziert. Die Analyse der Rezeptor-Proteinexpression erfolgte mittels Autoradiographie mit Tritium markierten Neurotensin und immunhistochemisch mit spezifischen Antikörpern gegen NTR1, 2 und 3.

Ergebnisse/Results:

Die Quantifizierung auf mRNA Ebene ergab in den HT-29 und FaDu Zellen eine 3,5fach höhere Expression von NTR3 im Vergleich zu NTR1. Die Expression von NTR3 im Vergleich zu NTR2 war um den Faktor 2,5 erhöht. Die mRNA Rezeptorverteilung in den entsprechenden Tumortransplantaten verhielt sich für NTR3 ähnlich stark wie in den Zellen. Ebenfalls konnte in den Transplantaten eine gesteigerte Expression von NTR1 um das 2fache für die HT-29 Transplantate und das 1,4fache für die FaDu Transplantate beobachtet werden. Auf Proteinebene wurde ein starkes immunpositives Signal für NTR1 in den Zellen und Geweben detektiert. Rezeptorprotein für NTR3 konnte in unseren Untersuchungen nicht nachgewiesen werden.

Schlussfolgerungen/Conclusions:

Aufgrund der hohen Proteinexpression, scheint NTR1 für die Tumordiagnose ein geeignetes Target via Radiomarkierung zu sein. Überdies stellt NTR 1 als G-Protein gekoppelter Rezeptor eine wichtige Funktion bei der intrazellularen Signalübertragung dar und ist zudem ein interessantes Target für die Entwicklung therapeutisch wirksamer Medikamente.

Ziel/Aim:

Oxidative modification of LDL apolipoprotein (apo) B-100 by myeloperoxidase-generated hypochlorite (HOCL) is regarded as a crucial event in atherogenesis. Recently, HOCl-modified LDL (OCl-LDL) have been shown to be present in human atherosclerotic lesions. On the other hand, data concerning the role of circulating OCl-LDL in the development of atherosclerosis are scarce. One reason for this is the shortage of methods for direct assessment of metabolism of oxidized LDL in vivo. We report an improved methodology for radiolabeling of both native LDL (nLDL) and OCl-LDL with the positron-emitter fluorine-18 (F-18) by N-succinimidyl-4-(F-18)fluorobenzoate (F-18-SFB) and the use of F-18-fluorobenzoylated LDL particles in dynamic PET studies in rats.

Methodik/Methods:

As a model, nLDL were modified in vitro by 3 mM NaOCl. For radiolabeling, pools of chemically and biochemically well characterized human nLDL and OCl-LDL were used. Module-assisted synthesis of F-18-SFB resulted in radiochemical yields of 36±2% (corrected for decay) and purites of >95%.

Ergebnisse/Results:

LDL labeling with F-18-SFB resulted in radiochemical yield of 30±10% (nLDL; corrected for decay) and 10±5% (OCl-LDL), respectively, with specific radioactivity of 50-400 GBq/µmol. Radiolabeling of native and modified LDL using F-18-SFB caused neither additional oxidative structural modifications of LDL lipids and proteins nor alteration of their biological activity and functionality in vitro, respectively. The method was further evaluated with respect to the uptake of F-18-fluorobenzoylated native and modified LDL, respectively, in various human cells. Biodistribution studies in rats revealed high in vivo stability for the fluorine-18-fluorobenzoylated LDL. The metabolic fate of F-18-fluorobenzoylated nLDL and OCl-LDL particles in vivo was delineated by dynamic PET studies using a dedicated small animal positron emission tomograph. Dynamic PET data demonstrated a significantly enhanced catabolism of OCl-LDL when compared with nLDL. The in vivo distribution and kinetics of both native and modified LDL correlated well with the anatomical localization of LDL receptors and scavenger receptors.

Schlussfolgerungen/Conclusions:

F-18-SFB-labeling of LDL and the use of small animal PET provide a valuable tool to discriminate the kinetics and the metabolic fate of both native and oxidized LDL in animal models in vivo.

Ziel/Aim:

In (1) und (2) wurden bereits Verfahren vorgestellt, welche halbautomatisch zur Eingrenzung, Analyse und quantitativen Auswertung dreidimensionaler Strukturen innerhalb von PET-Bildvolumen dienen. Die dort beschriebene Schwellwertanalyse mittels Schwellwert über Untergrund und der damit verbundenen Untergrundsubtraktion, führen bei Phantommessungen zu einer Unsicherheit der Volumenbestimmung von unter 20%.

Das Ziel dieser Arbeit war es, die Inter-Observer-Variabilität(IOV) des Verfahrens anhand klinischer Datensätze zu überprüfen und mit der manuellen Schwellwertanalyse, also der interaktiven Festlegung eines von Benutzern als optimal bewerteten Schwellwertes, zu vergleichen.

Methodik/Methods:

Es wurden PET-Volumendatensätze aus dem Bereich der onkologischen Leberdiagnostik und Phantommessungen ausgewertet. Die Studien enthielten eine verschiedene Anzahl von interessierenden Strukturen (VOIs), die dreimal auf unterschiedliche Weise abgegrenzt werden mussten. Im ersten Schritt sollte der Observer die VOIs mittels der manuellen Methodik abgrenzen, im zweiten Schritt sollte er jede VOI einzeln mittels der automatischen Methode aus (2) abgrenzen und im dritten Schritt sollte er alle gesuchten VOIs gleichzeitig mittels der Methode aus (2) bestimmen. Die Zahl der vorläufig untersuchten VOIs ist n=24 und damit die der Abgrenzungen n=168.

Ergebnisse/Results:

Bei den betrachteten Datensätzen lieferten die in (2) vorgestellten Methoden sehr stabile Ergebnisse. Im Gegensatz dazu schwankten die ermittelten Volumen bei der manuellen Schwellwertanalyse zwischen den einzelnen Observern sehr stark.

Die IOV bei manueller respektiv automatischer Volumenbestimmung konnte im Mittel von ca. 30% auf ca. 10% reduziert werden, wobei das mittlere Volumen vergleichbar mit den Werten der manuellen Bestimmung ist.

Schlussfolgerungen/Conclusions:

Der Vergleich zeigt, dass der Einsatz automatischer Verfahren die IOV im Vergleich zu manuellen Verfahren deutlich reduziert. Prospektiv erscheint die implizierte Möglichkeit zur Standardisierung der PET-unterstützten Zielvolumendefinition von potentieller Bedeutung für die Strahlentherapieplanung.

Literatur/References:

(1) C.Pötzsch; B. Beuthien; J. van den Hoff; Teilautomatisierte Segmentierung zur Quantifizierung von Metastasen bei der FDG-PET; Nuklearmedizin (2003) 42 p. A26

(2) C.Pötzsch; F. Hofheinz; J. van den Hoff; Minimierung der Inter-Observer-Variabilität bei volumetrischen Auswertungen von onkologischen Ganzkörperstudien in der PET; Nuklearmedizin (2005) 44 p. A16

Ziel/Aim:

PET-Systeme, die wie der weit verbreitete ECAT Exact HR+ das ACS2 Kontrollsystem nutzen, erlauben es auf Grund von Limitationen der ACS2 Hardware mit nur sehr geringen Raten auf die akquirierten Daten zuzugreifen. Bei den üblicherweise mehreren Gigabyte großen Listmodedaten behindert dies die routinemäßige Auswertung dieser Daten erheblich. In (1) wurden bereits Methoden vorgestellt, die dem entgegenwirken. Um jedoch Korrekturmethoden, wie z. B. eine listmode-basierte Bewegungskorrektur effektiv in die Routine zu überführen, bedarf es weiterer Entwicklungen. Unsere Studie soll daher überprüfen, inwieweit ein echtzeitnaher Zugriff auf Listmodedaten durch Analysen und Hardwareentwicklungen am ACS2 System erreicht werden kann.

Methodik/Methods:

Die Koinzidenzdaten einer PET-Akquisition werden innerhalb des ACS2 Systems über einen extern zugänglichen Datenbus geführt. Dieser aus 32 Datenleitungen bestehende Bus verbindet die verschiedenen Hauptkomponenten des ACS2 und überträgt den Listmodedatenstrom während einer Akquisition. Um einen externen Abgriff dieser Daten zu ermöglichen, ohne jedoch die Standardkomponenten des PET Scanners zu beeinflussen, wurde ein optoelektronisch getrennter Adapter entwickelt. Dieser wurde zusammen mit einem durch digitale Datenakquisitionskarten erweiterten Linux Rechner am ACS2 angeschlossen. Ferner wurde eine Software entwickelt, die die abgegriffenen Daten über eine Netzwerkverbindung für andere Rechner zur Verfügung stellt, aber auch eine unmittelbare Verarbeitung bzw. Sortierung der Listmodedaten in Sinogramme zulässt.

Ergebnisse/Results:

Die entwickelten Methoden erlauben es, auf die Rohdaten eines ACS2 basierten PET-Scanners in Echtzeit zuzugreifen. Zur Verifikation wurden verschiedene Testmessungen bis zur Zählratengrenze des PET-Scanners durchgeführt. Hierbei lag die Drop-out Rate von nicht registrierten Ereignissen unterhalb 0,1%.

Schlussfolgerungen/Conclusions:

Die vorgestellten Methoden erlauben es, mit relativ kostengünstigen Mitteln ACS2-basierte PET-Scanner für einen Echtzeitzugriff auf Listmodedaten umzurüsten. Mit der entwickelten Software ist es möglich, die akquirierten Listmodedaten zeitnah zu bearbeiten und unmittelbar nach der Akquisition für eine Auswertung vorzuhalten. Dies stellt einen wichtigen Fortschritt bei der konsequenten Anwendung von Listmode in der PET dar.

Literatur/References:

(1) Langner J. et al., Entwicklung von Methoden zum beschleunigten Zugriff auf Akquisitionsdaten ACS2-basierter PET-Scanner; Nuklearmedizin 2005; 44; p. A161

kein Abstract verfügbar

Ionenstrahlen erlauben bei der Radiotherapie von Tumoren auf Grund ihrer physikalischen und biologischen Eigenschaften ein höheres Maß an Präzision und Wirksamkeit als konventionell zur Bestrahlung eingesetzte Elektronen- oder Photonenstrahlen. Daher ist ein in-situ Monitoring der Dosisapplikation bei Ionenstrahlen wünschenswert. Gegenwärtig ist dafür nur die in-beam
Positronen-Emissionstomographie (PET) bekannt. Dabei werden zwischen Projektil und Gewebe stattfindende Kernreaktionen, die zur Erzeugung von Positronenemittern führen, genutzt um durch den Nachweis der emittierten g-Strahlung Aussagen zur Reichweite der Teilchen, zur Lage des bestrahlten Feldes und zu anatomischen Veränderungen gegenüber dem Zustand des Patienten zur Zeit der Planung der Bestrahlung zu treffen. In die experimentelle 12C Ionentherapieanlage an der Gesellschaft für Schwerionenforschung (GSI) Darmstadt wurde ein in-beam PET-Scanner integriert und diese Methode erstmals klinisch angewendet. An dieser Anlage wurden seit 1997 über 300 Patienten, vornehmlich mit strahlenresistenten Tumoren im Kopf-Hals Bereich behandelt. Diese Bestrahlungen wurden mit Hilfe von in-beam PET kontrolliert. Gegenwärtig gibt es Bemühungen, in-beam PET auch für andere Ionensorten als 12C nutzbar zu machen.

Bispidines (bispidine = 3,7-diazabicyclo[3.3.1]-nonane) show interesting complexation behaviour towards transition metal ions. [1] The stabilities achieved for copper complexes with bispidines – lying in the same range as found for copper complexes of aza macrocycles – offer the possibility to apply such complexes for diagnostic and therapeutic purposes (^64/67Cu).
We want to present the synthesis of novel hexadentate bispidine derivatives having pyridine and/or imidazole units as donor groups. Cu(II) complexes of some bispidines have been isolated and the structures were characterised by single-crystal X-ray diffraction analysis. Studies which have been performed to label selected bispidines with ^64/67Cu indicate a rapid formation of stable complexes under mild conditions. Chemical approaches to introduce bio-molecules into the bispidine skeleton are discussed.

kein Abstract verfügbar

Low energy ion erosion of surfaces can lead to the formation of self-organized structures in the range from 10 to 100 nm [1]. Periodic ripple patterns and hexagonally ordered dot arrays can be achieved for oblique and normal incidence, respectively. The evolution of ripple structures on different materials has been studied extensively during the last decades whereas the formation of dots has been discovered only recently [2] and is not fully understood yet.
In the presented work, the evolution of GaSb(001) surface morphology under normal incidence sputtering has been studied in-situ by surface sensitive X-ray techniques. The Grazing Incidence Small Angle X-ray Scattering (GISAXS) and Grazing Incidence Diffraction (GID) measurements have been performed at the beam line ID01 at the ESRF. These techniques were used to study the evolution of the dots for ion energies from 100 to 1000 eV. With GISAXS the morphology and the correlation of the dots is analysed, while in GID information about the crystalline structure (i.e. strain) is added. This way, three regimes are observed and identified as smoothing, pattern formation and increase of lateral order.

[1] M. Navez, D. Chaperot and C. Sella, C. R. Acad. Sci. 254 (1962), 240
[2] S. Facsko et al., Science 285 (1999), 1551

The structural integrity of the reactor pressure vessel (RPV) has to be maintained throughout the operation time of a nuclear power plant (NPP). The fracture toughness of the RPV steel has to be higher than the stress intensity at the crack tip. The present regulatory-based correlative approaches for the determination of fracture toughness of RPV steels are not consistent because they link technological parameters (RTNDT, Charpy-V) and universal fracture toughness lower bound curves. Safety margins as well as probability estimations cannot be quantified. In contrast, a new “Master Curve” (MC) method enables the direct measurement of the fracture toughness with less uncertainty. The MC approach is based on Weibull statistics and models the cleavage failure of a specimen in the lower ductile-to-brittle transition region.
To maximize the Master Curve’s benefits, it should be incorporated in regulatory evaluation or integrity assessment as a long term objective. Before the Master Curve approach can be implemented in codes and regulations, open issues such as influence of irradiation, loading rate effects, loss of constraint, as well as the effects of inhomogeneous material need resolving.
The Research Centre Rossendorf is currently investigating the invariability of the MC shape for “extreme” irradiation, the applicability in case of partial intergranular fracture, annealing effects, and the correlation of MC and Charpy results. Latest results will be presented.

Low temperature doping with transition metals is currently accepted as the “silver bullet” for the creation of diluted magnetic semiconductors (DMS). Among them, ion implantation offers the possibility for doping at almost any temperature. However, tiny, hardly detectable ferromagnetic nanoparticles created due to phase separation already during implantation can wrongly give the impression of a DMS by means of a pronounced integral magnetization. In this work we would like to present systematic investigations on the formation of ferromagnetic nanoparticles due to 57Fe implantation into ZnO single crystals applying several sensitive analysis techniques. At an implantation temperature of 623 K and implantation energy of 180 keV, a distinct dependence of the nanoparticle formation on the Fe ion fluence was observed. Below a fluence of 2x1016 cm-2, all Fe is found in nonmagnetic charged states indicating no -Fe-nanoparticle formation as was confirmed using X-ray diffraction. From a fluence of 2x1016 cm-2, superparamagnetic -Fe-nanoparticles are present. They were evidenced by zero-field cooled (ZFC) and field cooled (FC) magnetization curves, x-ray diffraction and transmission electron microscopy. The superparamagnetic blocking temperatures increase with the implanted fluence. An annealing at 823 K for 15 min enhanced the Fe particle formation, but Fe nanoparticles were oxidized after an annealing at 1073 K for 15 min. A further annealing at 1073 K for 3.5 h induced the formed of ZnFe2O4. In a conclusion, we definitely rule out the formation of a diluted magnetic semiconductor in Fe-implanted ZnO at process temperature above 623 K.

We report the structural and magnetic properties of ZnO single crystals implanted at 623 K with up to 10 at. % of Ni. As revealed by X-ray diffraction, crystalline fcc-Ni nanoparticles were formed inside ZnO. The magnetic behavior (magnetization with field reversal and with different temperature protocol) of all samples is well explained by a magnetic Ni-nanoparticle system. Although the formation of Ni:ZnO based diluted magnetic semiconductor cannot be ruled out, the major contribution to the magnetic properties stems from crystalline nanoparticles synthesized under these implantation conditions.

The paper presents results of a study on the motion of bubbles rising in upward shear liquid flow in the vicinity of a vertical wall. Bubbles were found to slide along the wall, when their diameter is small. Bubbles could also experience multiple collisions with the wall at certain experimental parameters (geometry of a channel, range of superficial liquid velocity, bubble size, etc). The latter was theoretically predicted by solving the equation of the bubble motion for the lateral direction in the boundary layer of the channel. For this, the available in the literature constitutive models for the interfacial forces acting on a bubble in the vicinity of the wall were used. A simplified 1D model predicting bubble lateral displacement near the wall and taking into account the balance of drag and non-drag forces acting on a bubble was proposed. The numerical results were verified against the experimental ones obtained by non-intrusive high-speed video observations and subsequent image processing.
The experiments on the bubble motion were conducted in a vertical acrylic duct having a square cross-section of 25 cm2 and a height of approximately 1.3 m. Desalinated water and air both taken at the room temperature were used in the experiments. All measurements on the bubble motion were performed at channel heights between 0.8 and 1 m above the gas injection point.

Highly charged ions carry a large amount of potential energy, which is defined as the sum of the binding energies of all removed electrons. In the case of low velocities of the ions this energy can exceed their kinetic energy.
Approaching the solid surface the ions are neutralized, relaxe to the ground state, and their potential energy is released. Thereby different mechanisms, such as surface sputtering, secondary ion emission, secondary electron emisson and X-ray emission take place [1]. The secondary particles leaving the surface carry only up to 10% of the potential energy.
Using a calorimetric setup [2] we measured the amount of the potential energy which remains in the solid to 85% +/- 10%.
To study the detailed mechanism of the energy retention materials with different electronic structures were investigated: Cu, n-Si, p-Si, SiO2.
We can conclude, that the difference in energy depositon between these materials is below 10%.
The calorimetric results are rounded off with results from energy reemission measurements using electron spectroscopy.
The value of the reemitted energy increases with increasing charge state up to 10%.
[1] A. Arnau et.al.: Surf. Sci. Rep.27, 113 (1997).
[2] U. Kentsch et.al.: Phys. Rev. Lett.87, 10 (2001).

Die Rossendorfer Zweiquellenionenstrahlanlage stellt eine weltweit einmalige Kombination aus einer Elektron-Zyklotron-Resonanz-Ionenquelle mit einer bei Raumtemperatur arbeitenden Elektronenstrahl-Ionenquelle, der Dresden EBIT, dar. Die Ionenstrahlen beider Quellen münden in eine gemeinsame Targetkammer und stehen dort für Experimente zur Verfügung. Die erreichbaren Ladungszustände, die Ionenströme sowie die Energien der Ionen aus beiden Quellen unterscheiden sich aufgrund der verschiedenen Wirkungsprinzipien und gewährleisten so ein breites Spektrum an Experimenten. Die Gesamtanlage kann gegenüber der Targetkammer auf ein negatives Potential gebracht werden, wodurch sich die Ionen beider Quellen bis auf Energien unter q*100V abbremsen lassen. Die Untersuchung der Wechselwirkung langsamer hochgeladener Ionen mit Festkörperoberflächen, insbesondere der Einfluss der Potentialenergie der Ionen, ist neben der Ionenquellendiagnostik Gegenstand aktueller Forschungen an der Rossendorfer Zweiquellenanlage.

Highly charged ions (HCI) carry a large amount of potential energy, which is defined as the sum of the binding energies of all electrons that are removed from the atom. In the case of low velocities of the ions this energy is equal or can exceed the kinetic energy of the ions. Retaining such a large energy in a very small surface area of typically about 1-10nm^2 and in a very short interaction time of typically 5-10fs an enormous power flux of 10^13 W/cm^2 is given. In respect of this, high yields of photons and electrons have been observed, which carry away a fraction of the potential energy. Some experiments give a quantitative estimation of an energy reemission coefficent in the order of only 10%. In our experiment we determine the fraction of the retained potential energy of the ions by a calorimetric measurement.

For improved calorimetric measurements of the retention of the potential energy of highly charged ions a UHV device with a base pressure of p<10^-9mbar was constructed and connected to the 7.5 GHz ECR ion source at the Forschungszentrum Rossendorf. The ECR ion source is equipped with a sector field magnetic separation and a beam deceleration system. The ions are accelerated with a voltage of 5 kV and after beam transport decelerated to final kinetic energies down to 60eVxq.

By using a calorimetric setup the increase of the target temperature is measured during the irradiation with argon ions.
The retained energy of Ar q+ (q= 1 up to 9) ions into the Si(100) surface is determined at kinetic energies between 60 eVxq and 200 eVxq. By extrapolation to zero kinetic energy the retained fraction of the potential energy is obtained.

For absolute calorimetric measurements a small resistive heater is used for the calibration of the calorimetric setup. Using the resistive heater a function between the temperature increase and the deposited electrical power of the heater is obtained. Assuming that the electrical power is equivalent to the retained power of the incident ions the retained power of the ions can obtained from the temperature increase.

By sputtering with Ar+ the silicon surface is cleaned before the measurement. The chemical state of the target surface is controlled by AES using LEED
optics. Once being clean there are no other Auger electron signals in spite of silicon signals detectable over a time of 7 hours.

The obtained retained potential energy of the different charge states of the argon ions is related to the total potential energy. The potential energy retention coefficient results as 0.7 +/- 0.2 and decreases weakly with increasing charge state. This values are compared with earlier measurements [1] on a copper surface. The potential energy retention coefficient for silicon is about three times larger than the results with the copper surface.

[1] U. Kentsch, H. Tyrroff, G. Zschornack, and W. Möller, Retention of the potential energy of multiply charged argon ions incident on copper, Phys. Rev. Lett. 87(10), 4273 (2001).

Despite the recent success of fully coupled three-dimensional numerical models of the geodynamo, the very nature of field reversals is still a matter of controversy. A mean-field dynamo model with a spherically symmetric helical turbulence parameter alpha serves us as a sort of minimum dynamo model that exhibits a number of typical reversal features. These include the asymmetry of reversals, the correlation between field strength and interval length, the existence of an inhibition time, and the bimodal field distribution. We identify the existence of a branch point of the spectrum of the non-selfadjoint dynamo operator as the essential ingredient for reversals to happen (Phys. Rev. Lett. 94 (2005), 184506). We present some evidences for a self-tuning mechanism of highly supercritical dynamos that tend to saturate into a reversal-prone state by driving the branch point and its nearby local maximum of the growth rate towards the zero line (Earth Planet. Sci. Lett. 143 (2006), 828-840). The high supercriticality can also explain the typical time-scales of asymmetric reversals (arxiv.org/physics/0601011), without taking resort to a turbulent resistivity. The role of the inner core to increase the ratio of excursions to reversals is discussed in the framework of resonant appearance of branch points in dependence on the wavelength of the dynamo source (arxiv.org/math-ph/0602013).

It is widely recognized that colloids can influence the migration of toxic and radiotoxic elements such as uranium. There are transport-facilitating and transport-impeding effects caused by colloids.
The most common scenario assumed in performance assessment for nuclear waste repositories is contaminant transport through anoxic aquifers. Only transport-facilitating effects of colloids are usually taken into consideration for this case. For abandoned uranium mines, retarding influences of colloids, apart from mobilizing ones, are also of high interest since they have the potential of causing “natural attenuation” of the environmental hazard.
The formation of colloids containing U(IV) and U(VI) was studied by laboratory experiments and by comparing the results with field experience. It is shown that there may be transport-stimulating effects of colloids on the “immobile” contaminant U(IV) and transport-impeding effects on the “mobile” contaminant U(VI).
A key factor in assessing the impact of colloids in a geochemical setting is the timescale that needs to be taken into account. Very long periods of time must be considered for nuclear waste repositories. Here, the point in time at which a certain colloid-borne contaminant such as uranium reaches the biosphere depends on the moment at which spent fuel container leakage begins, the water flow velocity, the concentration and mobility of potential carrier colloids, the hindrance of colloidal transport by barrier materials, and the persistence (reversibility vs. irreversibility) of the binding of the contaminant onto the colloids. In the case of mines, the phase critical for the environment occurs when the flood water reaches the level where first connections to unprotected surface waters or underground drinking water resources occur. This phase is characterized by the „first flush“ of the mine; the maximum release rate of contaminants such as U from the mine to the environment can be reduced by colloids via the flattening of the release rate profile. Whereas the timescale of critical contaminant release is in the range of centuries for the nuclear waste repositories, it lies in the range of only few years for abandoned uranium mines.
It is primarily the different dynamics of the processes behind these two different timescales that causes the different role of colloids for uranium migration in nuclear waste repositories and in abandoned uranium mines.

Plant-measured data provided by the OECD/NEA VVER-1000 coolant transient benchmark programme were used to validate the DYN3D/RELAP5 and DYN3D/ATHLET coupled code systems. Phase 1 of the benchmark (V1000CT-1) refers to an experiment that was conducted during the commissioning of the Kozloduy NPP Unit 6 in Bulgaria. In this experiment, the fourth main coolant pump was switched on whilst the remaining three were running normal operating conditions. The experiment was conducted at 27.5 % of the nominal level of the reactor power. The transient is characterized by a rapid increase in the primary coolant flow through the core, and as a consequence, a decrease of the space-dependent core inlet temperature. The control rods were kept in their original positions during the entire transient. The coupled simulations performed on both DYN3D/RELAP5 and DYN3D/ATHLET were based on the same reactor model, including identical main coolant pump characteristics, boundary conditions, benchmark-specified nuclear data library and nearly identical nodalization schemes. In addition to validation of the coupled code systems against measured data, a code-to-code comparison between simulation results has also been performed to evaluate the respective thermal hydraulic models of the system codes RELAP5 and ATHLET.

for further information, please contact the author

1. Introduction
Integrins are cell surface transmembrane glycoproteins that are found as αβ heterodimers. The αvβ3 integrin is known to be over-expressed in many tumour types and sprouting blood vessels in the tumour, but expressed at lower levels in normal tissues. Peptides containing the Arg-Gly-Asp (RGD) sequence, bind with high affinity to αvβ3 and have found increasing interest for radiolabelling to target v3 receptors and for imaging angiogenesis. Recently, it was demonstrated using [18F]Galacto-RGD and PET that monitoring of αvβ3 is possible in animal models as well as in humans (1). Recent advances in organometallic chemistry enable 99mTc-labelling of biomolecules with high specific activity and high stability. The aim of this study was to use a cyclic RGD derivative, c(RGDyK), containing a Lys residue for derivatisation with different moieties for labelling with 99mTc using novel technetium-cores, such as HYNIC, Tc(CO)3, and Tc(4+1) approaches and to compare chemical and biological properties in vitro and in vivo.

2. Materials & Methods:
c(RGDyK) (RGD) was derivatised with HYNIC (1), Cys (2), 3, 5–Me2 –pyrazol-1-yl-ethyldiamine –RGD (PZ1, 3) and an isonitrile moiety (L3, 4) at the terminal lysine group of c(RGDyK) using standard fmoc chemistry (examples see Fig1). 99mTc-labelling was performed using both Tricine as well as EDDA as coligands for HYNIC-RGD, [99mTc(CO)3(H2O)3]+ was used for labelling Cys-, PZ1 and HYNIC-RGD and Aminotrithiols as coligangds for L3-RGD at high specific activities. Radiolabelled peptides were characterised concerning lipophilicity (octanol/PBS coefficient, RP-HPLC), protein binding using SEC, stability in buffer, serum and tissue homogenates and tested for stability in PBS, Cystein and Histidine solutions, tissue homogenates and serum up to 6 h. Integrin receptor activity was determined in internalisation assays using v3 receptor positive M21 and negative M21-L melanoma cells. Biodistribution and in vivo tumour uptake was evaluated in nude mice carrying M21 and M21-L tumours for selected compounds.

3. Results
All peptides could be labelled at high specific activities and revealed high stability in various solvents. Both lipophilicity as determined by HPLC retention times and log P values (-0.92 to -3.57) and binding to serum proteins (2-32%) varied considerably All 99mTc-labelled peptides showed specific uptake in αvβ3 positive cells with comparable values for all compounds around 1% of total/mg protein except for 99mTc-L1 and L3-RGD with lower values of less than 0.5%. In a mouse tumour model great variations in pharmacokinetic behaviour was found ranging from predominant renal excretion up to predominant hepatobiliar eliminiation. Highest specific values of tumour uptake were found for 99mTc-EDDA/HYNIC-RGD and 99mTc(CO)3-PZ1-RGD (see Fig. 2) with about 2.5% uptake in M21 receptor positive tumours and <1% in receptor negative M21-L tumours with lower intestinal uptake of 99mTc-EDDA/HYNIC-RGD.

4. Discussion/Conclusion
Our study provides for the first time data on chemical and biological characterisation of the same peptide labelled with 99mTc using different technetium-cores. It shows the decisive influence of labelling approaches on imaging properties of 99mTc-labelled peptides and the necessity to use different in vitro assays to predict targeting properties in vivo.

5. References:

(1) Haubner R, Weber WA, Beer AJ, Vabuliene E, Reim D, Sarbia M, Becker KF, Goebel M, Hein R, Wester HJ, Kessler H, Schwaiger M. [2005] PLoS Medicine. 2(3):e70.

6. Acknowledgements:

This work is part of the CRP “Development of Tc-99m based small bio-molecules using novel 99mTc cores” of the IAEA

1 Introduction
Organometallic Tc and Re (III) compounds in terms of so called “4+1” complexes enable high specific labelling of biomolecules, e.g., peptides under mild conditions and exhibit high complex stability [1, 2]. However, ^99mTc-labelled peptides containing a “4+1” complex as in ^99mTc(NS₃)(CN-GGY) (Fig. 1) showed a high liver uptake [1]. To improve the biobehavior of such compounds a new hydrophilic “4+1” complex bearing three carboxyl groups was introduced and evaluated coupled to a model peptide.

2 Results
The carboxyl-groups bearing ligand NS₃(COOH)₃ was synthesized by conjugation (DCC) of the dendritically functionalized amine H₂N-C(-CH₂-O-CH₂-CH₂-COO-Me)₃ [3] to the S-benzyl protected NS₃COOH [1] followed by deprotection.
The isocyanide group was coupled to the model peptide Gly-Gly-Tyr via an aliphatic linker (CN-BFCA). For ^99mTc-labelling a two-step procedure [1] was applied using ^99mTc-EDTA/mannitol (400 MBq) which was reacted with 20 µg isocyanide-modified peptide and 300 µg NS₃(COOH)₃. ^99mTc-labelling resulted in a radiochemical yield of app. 25 % (HPLC), Fig. 2. The yield can be increased by using a higher peptide amount. ^99mTc(NS₃(COOH)₃)(CN-GGY) showed a high in vitro stability (> 90 % in PBS after 24 h).
To verify the identity of the ^99mTc-labelled peptide, the analogous "4+1" Re compound Re(NS₃(COOH)₃)(CN-GGY) was synthesized (Fig. 1).

For a convenient synthesis of peptides containing the new hydrophilic Re “4+1” complex, the active ester Re(NS₃(COOMe)₃)(CN-BFCA) as shown in Fig. 1 was prepared starting from NS₃(COOH)₃, [Re(tu-S)₆]Cl₃ and PMe₂Ph followed by ligand exchange with CN-BFCA. Reaction of Re(NS₃(COOMe)₃)(CN-BFCA) with the peptide and hydrolysis of the methyl ester gave the desired peptide derivative.
The increased hydrophilicity of the new “4+1” complex was shown by HPLC investigations (Fig. 2) and determination of the partition coefficient (logD, octanol/PBS, pH 7.4).
^99mTc(NS₃(COOH)₃)(CN-GGY) showed a logD value of -2.6 ± 0.3 (n = 3) compared with the logD value of -1.5 ± 0.2, ^99mTc(NS₃)(CN-GGY).

3 Conclusion
A new hydrophilic “4+1” complex characterized by a dendritically modified tetradentate ligand was synthesized and has been introduced for peptide labelling. Increasing generation of dendritic branches will be grafted on the chelating unit in order to tune the lipophilicity. As a next step peptides bearing the new modified “4+1” compound have to be evaluated in animal experiments.

4 References
[1] Seifert S., Künstler J.-U., Schiller E., Pietzsch H.-J., Pawelke B., Bergmann R. and Spies H. [2004] Bioconjugate Chem. 15: 856-863.
[2] Schiller E., Seifert S., Tisato F., Refosco F., Kraus W., Spies H. and Pietzsch H.-J. [2005] Bioconjugate Chem. 16: 634-643.
[3] Newkome G. R., Lin X. and Young J. K. [1992] Synlett 1: 53-54.

5 Acknowledgements
The work was performed in the framework of the project “Chemical Studies for Design and Production of New Radiopharmaceuticals” (No MTKD-CT-2004-509224 (POL-RAD-PHARM)) supported by the European Community within the 6th Framework Programme Marie Curie: Host Fellowships for Transfer of Knowledge.

In der Einleitung wird das Rossendorfer Ionenstrahllabor mit allen zur Verfügung stehenden ionenstrahl-analytischen Methoden zur Elementanalyse im oberflächennahen Bereich von Festkörpern kurz vorgestellt.
Die physikalischen Grundlagen zur Wasserstoffanalytik mittels resonanter Kernreaktion (RNRA) und elastischer Rückstoßstreuung (ERDA) werden erläutert. Es werden die notwendigen Voraussetzungen zur Berechnung der H-Konzentration und – tiefenprofile diskutiert. Die folgenden Anwendungsbeispiele sollen die Leistungsfähigkeit und Grenzen beider Methoden verdeutlichen. So wird die H-Konzentration in SiO2 – Schichten untersucht, die durch nasschemische Oxidation von Si erzeugt wurden. Hierbei wird darauf hingewiesen, wie wichtig die Kontrolle eines eventuellen H-Verlustes während der Analyse ist, um Fehlmessungen auszuschließen. Die mit RNRA erreichte Tiefenauflösung von 1 nm macht die Untersuchung der H-Verteilung in ca. 10 nm dünnen ZrO2– und Al2O3-Schichten möglich. Es wird über den Versuch berichtet, H-Monolagen zu untersuchen.
ERDA am Mikrostrahl (micro ERDA) machte erstmalig die Messung von dreidimensionalen H-Verteilungen möglich, die in H-implantierten Ti-Blechen mit und ohne Biegespannung untersucht wurde.

Molecular recognition, binding and transport of different chemical species represents an aspect of supramolecular chemistry that has relevance to a number of areas that include biochemical processes, analytical techniques, recycling and environmental processes as well as aspects of catalysis and medicine. Over the years a large number of both efficient and selective receptors for cations, anions, salts and zwitterions based on different architectures and binding modes have been developed and studied. Among the manifold experimental techniques employed for the application of such receptors has been the investigation of the distribution of species between two immiscible solutions, normally an aqueous and an organic phase, under the influence of the receptor in the organic phase. Such a procedure has often allowed characterization of the receptor’s complexation behaviour towards individual species as well as enabling an evaluation of its suitability for species monitoring, separation and/or concentration; especially with respect to possible analytical applications as well as for use in extraction and membrane transport processes.

Radioaktive Kupfer(II)-Komplexe weisen ein hohes inhärentes Anwendungspotential für radiopharmazeutische Anwendungen in Diagnostik und Therapie auf. In diesem Zusammenhang zeigen sechszähnige Derivate des Bispidins (3,7-Diazabicyclo[3.3.1]nonan) aussichtsreiche Eigenschaften. Sie bilden insbesondere mit Kupfer(II) Komplexe hoher Stabilität. Um eine selektive Anreicherung der radioaktiven Kupferkomplexe im Zielgewebe zu erzielen, ist es notwendig, Biomoleküle an das Ligandgrundgerüst anzukoppeln.

Radiochemistry with the short-lived positron emitter carbon-11 (t_1/2 = 20.38 min) represents special challenges in terms of synthesis time and the labelling techniques. The recent developments in carbon-11 radiochemistry have steadily expanded the number of carbon-11 labelled compounds. The review wants to address selected chemical and technical aspects of carbon-11 chemistry based on the readily available labelling precursors [¹¹C]methyl iodide and, to some lower extent, [¹¹C]methyl triflate. Special emphasis is attributed to heteroatom methylation reactions and ¹¹C-C bond formations.

The spectrum of the spherically symmetric α²-dynamo is studied in the case of idealized boundary conditions. Starting from the exact analytical solutions of models with constant α-profiles a perturbation theory and a Galerkin technique are developed in a Krein-space approach. With the help of these tools a very pronounced α-resonance pattern is found in the deformations of the spectral mesh as well as in the unfolding of the diabolical points located at the nodes of this mesh. Non-oscillatory as well as oscillatory dynamo regimes are obtained. An estimation technique is developed for obtaining the critical α-profiles at which the eigenvalues enter the right spectral half-plane with non-vanishing imaginary components (at which overcritical oscillatory dynamo regimes form).

Understanding of the growth process of undoped ZnO thin films is important for optoelectronic applications of the material. In this study, ZnO layers were deposited at single crystalline Al2O3 (0001) substrates by pulsed reactive magnetron sputtering. Oxygen partial pressure, base pressure and the substrate temperature (Ts) were varied systematically. The films were characterized by spectroscopic ellipsometry (SE), Seebeck effect measurements and X-ray diffraction (XRD). SE data were analyzed by using graded layer model for the film with Lorentz oscillator parameterization of the ZnO optical constants. The films produced at low temperatures always have negative Seebeck voltage, while at Ts>540 °C it changes to low positive values, which, however, degrade to negative values within several hours. The Lorentz oscillator broadening for the films grown at these temperatures increases with oxygen flow which points to a formation of more disordered structure inside ZnO grains in this case. XRD analysis yields decreasing grain size and increasing rocking curve full width on a half maximum with oxygen flow enhancement at the same Ts.

In dieser Arbeit wurde die durch Bestrahlung mit schnellen Neutronen bedingte Materialalterung von Reaktordruckbehälterstählen untersucht. Das Probenmaterial umfasste unbestrahlte, bestrahlte und ausgeheilte RDB-Stähle russischer und westlicher Reaktoren sowie Eisenbasis-Modelllegierungen. Mittels Neutronen-Kleinwinkelstreuung ließen sich bestrahlungsinduzierte Leerstellen/Fremdatom-Cluster unterschiedlicher Zusammensetzung mit mittlerem Radius um 1.0 nm nachweisen. Ihr Volumenanteil steigt mit der Strahlenbelastung monoton, aber im allgemeinen nicht linear an. Der Einfluss der Elemente Cu, Ni und P auf den Prozess der Clusterbildung konnte herausgearbeitet werden. Eine Wärmebehandlung oberhalb der Bestrahlungstemperatur reduziert den Anteil der Strahlendefekte bis hin zu deren vollständiger Auflösung. Die Änderungen der mechanischen Eigenschaften der Werkstoffe lassen sich eindeutig auf die beobachteten Gefügemodifikationen zurückführen. Die abgeleiteten Korrelationen können als Hilfsmittel zur Vorhersage des Materialverhaltens bei fortgeschrittener Betriebsdauer von Leistungsreaktoren mit herangezogen werden.

The luminescence spectrum of uranyl U(V) in aqueous perchlorate solution was detected for the first time at room temperature in the UV-Vis region with a peak maxima at 440 nm and a fluorescence lifetime of 1.1 +/- 0.021 mu s using an excitation wavelength of 255 nm.

The complexation of U(VI) with Aldrich humic acid (HA) was studied at pH 7 under exclusion of CO2. Using two independent laser-induced spectroscopic methods, time-resolved laser-induced fluorescence spectroscopy (TRLFS) and TRLFS with ultrafast pulses (fs-TRLFS), the formation of the ternary U(VI) mono hydroxo humate complex UO2(OH)HA(I) by reaction of UO2OH+ with HA was studied. Assuming that all proton exchanging functional groups of the HA are able to contribute to the complex formation, a mean stability constant of 6.58 ± 0.24 was derived for UO2(OH)HA(I). Alternatively, the analytical data were evaluated based on the metal ion charge neutralization model resulting in a complexation constant of 6.95 ± 0.10 and a loading capacity of 0.76 ± 0.28. An overall complexation constant of log b0.1M = 14.89 ± 0.54 was calculated for the total reaction of U(VI) with HA starting from the non-hydrolyzed UO22+ ion. This value agrees very well with literature data. Taking into account the UO2(OH)HA(I) complex, the speciation of U(VI) in presence of HA was recalculated. It was found, that the formation of UO2(OH)HA(I) can significantly influence the U(VI) distribution in the environmentally relevant pH region. As a consequence, the mobility of U(VI) in natural aquifer systems could be enhanced.

The decays of 102 Sn and 104 Sn were studied by using high-resolution germanium detectors as well as a Total Absorption Spectrometer (TAS). For 104 Sn, with three new beta-delayed gamma rays identified, the total Gamow-Teller strength (BGT) value of 2.7(3) was obtained. For 102Sn, the gamma-gamma coincidence data were collected for the first time, allowing us to considerably extend the decay scheme. This scheme was
used to unfold the TAS data and to deduce a BGT value of 4.2(8) for this decay. This result is compared to
shell model predictions, yielding a hindrance factor of 3.6(7) in agreement with those obtained previously for 98Cd and 100In. Together with the latter two, 102 Sn completes the triplet of Z < 50, N > 50 nuclei
with two proton holes, one proton hole and one neutron particle, and two neutron particles with respect to the doubly magic 100Sn core.

We have investigated the electronic structure of Sr2FeMoO6. In order to probe the partial densities of states we applied soft x-ray emission spectroscopy (XES) to the Fe L, the Mo M and the O K edges. We discuss the results in the light of complementary measurements of the valence band by means of x-ray photoelectron spectroscopy (XPS) and first-principles generalized gradient approximation (GGA) and LDA + U band structure calculations [1].
[1] K. Kuepper et al., J. Phys.: Condens. Matter 17, 4309 (2005).

We have investigated for the first time the orbital ordering in a three dimensional colossal magneto resistance manganite, namely
La7/8Sr1/8MnO3, by applying soft x-ray linear dichroism (XLD) to the Mn L edge [1]. We found that the cooperative Jahn Teller distorted orthorhombic phase, which is present at a temperature of 240 K, is probably accompanied by a predominantly cross type (x2−z2)/(y2−z2) orbital ordering. This result is discussed in the light of previous results obtained by means of resonant x-ray scattering at the Mn K edge and different exchange interaction models.
[1] K. Kuepper et al., J. Phys. Chem. B 109, 15667 (2005)

The mechanism of ion-induced ripple-like structure formation at top-surface
and at buried crystalline surface is being studied extensively by several techniques. Using the technique of grazing incidence x-ray scattering, we have measured the degree of amorphization in the region between buried-crystalline and top-surface ripples in silicon as a function of argon-ion dose. Two broad peaks of the amorphous scattering profiles were probed by varying the penetration depth of x-ray and revealed short-range ordering. Our results show that the strong damage of crystalline structure caused by ion bombardment takes place along particular crystallographic directions and displays ion dose dependent behavior.

Two types of highly soluble oligothiophene based swivel cruciform are presented as semiconducting materials in OFETs. Transistor made from one of these oligomers exhibited mobilities of more than 0.01 cm^2/Vs and current on/off ratio of >105. This is among the highest values reported to date for wet processed OFETs utilizing oligothiophenes. In fact, the OFET-mobilities are comparable to values extracted from pulse-radiolysis time resolved microwave conductivity (PR-TRMC) experiment, indicating that carrier trapping is insignificant. In depth examination of the morphological, optical characteristics and thermal stability of the materials were carried to obtain information on the packing of the oligomers in the layer. Finally, the correlation between the transistor performance and the crystallinity of the layers is addressed.

Investigations of ripples morphology of Ar+ implanted silicon are presented. Particularly we have measured the degree of amorphization as a function of implantation dose by means of x-ray grazing amorphous scattering (GIAS). For perfect silicon crystals GIAS shows monotone decreasing background intensity versus the 2theta scattering angle. For implanted samples we find two broad peaks indicating short-range ordering of amorphous material changing with the penetration depth of probing x-ray. The appearance of embedded crystalline domains is indicated by additional sharp peaks on top of the amorphous scattering. 2theta- scans taken at different azimuthal angles of sample display strong anisotropy of amorphous scattering which only slightly changes with dose. Based on these results we suggest a model of dose-dependent amorphization. The strong damage of crystalline structure takes place along particular crystallographic directions and strongly reveal for low doses, before it becomes complete amorphous and mostly uniform at high doses of implantation. This mechanism can be used as a hint for the appearance of a ripples amorphous-crystalline interface found at these structures.

We would like to thank S. Hazra and T.K. Chini for research collaborations.
This work was supported by the DST-DAAD India-Germany

The uranyl tricarbonato complex is one of the most important uranyl species under environmental conditions. The tendency to form stable metal-uranyl tricarbonato complexes was found particularly for the interaction with alkaline earth elements. We studied chemical behavior of these compounds in aqueous solution by time-resolved laser-induced fluorescence spectroscopy (TRLFS). However, under comparable chemical conditions the formation of these complexes is very different. While magnesium tends mainly to the formation of a MgUO2(CO3)32+ - complex, in the case of calcium the Ca2UO2(CO3)3(aq.) complex is the most stable. The stability constant for the Ca2UO2(CO3)3 – complex is derived to be log β°213 = 30.90 ± 0.25 [1]. In the corresponding systems with strontium as well as for barium only the MeUO2(CO3)32+ - complex is formed. The stability constants of the MeUO2(CO3)32+ - complexes are determined to be log β°113 = 26.13 ± 0.27 and 26.24 ± 0.31 for the alkaline earth elements Sr and Ba, respectively. The Me2UO2(CO3)3 – complexes for Mg and Ca form stable minerals as bayleyite and liebigite. However several other mineral modifications as zellerite, fontanite, sharpite and rabbittite underline the geochemical importance of this class of compounds.
Analogous phenomena can be expected in the alkaline earth uranyl phosphate systems. Therefore we studied the interaction of alklaine earth metal ione with UO2(PO4)- at pH 7.0. From the fluorescence data the formation of MeUO2(PO4)+ complexes in solution can be concluded. The stability constants are derived to be β°111 = 16.85 ± 0.16, 16.62 ± 0.15, 17.4 ± 0.4 and 16.9 ± 0.4 for Mg, Ca, Sr and Ba, respectively. The formation of complexes with the common formula Me(UO2)2(PO4)2aq has not yet been obeserved due to the low solubility of these componds. In the case of Mg and Ca the fluorescence data will be compared to the correspondong minerals saleiite and autunite [2].

The complex formation of uranium(VI) with 4-hydroxy-3-methoxybenzoic acid as well as with benzoic acid and 3-hydroxybenzoic acid was studied. In aqueous solution weak carboxylic 1:1 complexes, in which the carboxyl group is bidentately coordinated to the metal atom, are formed. The logarithmic stability constants of these complexes regarding the reaction of the uranyl ion with the single charged anion of the respective ligands are 2.78 ± 0.04, and 2.71 ± 0.04 at an ionic strength of 0.1 mol/l (NaClO4) and at 25 °C.
Bis(4-hydroxa-3-methoxybenzoato)dioxouranium(VI) was obtained as a crystalline complex if the concentrations of the starting compounds for the synthesis are increased. The monoclinic compound has a reflections-rich X-ray powder diffraction pattern. The lattice constants are a = 13.662(9) Å, b = 21.293(7) Å, c = 11.213(3) Å, b = 107.49(4)°, and V = 3111(2) Å3.

Within the tumor treatment pilot project running at the Gesellschaft für Schwerionenforschung (GSI) in Darmstadt, in-beam positron emission tomography (in-beam PET) is used to clinically monitor every patient irradiation with carbon ion beams. The physical, technical and radiobiological rationale for heavy ion tumor therapy will be shortly outlined, together with a comparison of clinical results obtained with carbon therapy versus other forms of radiotherapy.
In-beam PET, installed at GSI by the team from the Forschungszentrum Rossendorf, will then be presented in this clinical context, followed by a description of the technological solutions already achieved, as well as by the challenges to take into consideration in order to extend the in-beam PET method onto future radiotherapy facilities delivering also other ion species.

State-of-the-art technology has outperformed the efficiency of the positron emission tomograph installed at the Gesellschaft für Schwerionenforschung for monitoring, in-beam, ion radiation therapy. In addition, the special requirements of in-beam PET have been better understood. We explain these special requisites and present dedicated in-beam PET readout solutions, either tested in-beam or under development. Experimental results obtained with two multi-pixel, gamma-ray detectors consisting of lutetium oxyorthosilicate (LSO) coupled to avalanche photodiode arrays (APDA) show that this detector provides a good solution for improved, next-generation in-beam PET scanners.
Nevertheless, we extrapolate recent detector and scintillator developments, enabling sub-nanosecond coincidence time resolution (T), onto a possile in-beam time-of-flight (TOF) PET scanner. We show that T < 200 ps full-width-at-half-maximum allows:
(1) images to be shown to the radiooncologist in real-time,
(2) artifact-free images to be obtained from dual-head tomographs,
(3) an absolute quantification of image intensity and
(4) to obtain optimum PET images corrected from biological washout mechanisms.

Surface free energy minimization driven by capillary forces leads to morphological changes of wires, e.g. disintegration into a droplet chain – known as Rayleigh instability. At the nano-scale, capillary effects are much more pronounced than in macroscopic systems due to the large surface-to-volume ratio. However, capillary-driven self-organization processes are subject to increasing fluctuations with decreasing dimensions, which mostly prevent the formation of regular structures with long-range order. In this contribution, we predict by means of kinetic Monte Carlo simulations a novel method to fabricate size-controlled chains of nanodroplets. Our prediction rests on the temperature dependence of surface tension – the origin of thermocapillarity. Uncompensated forces occur due to surface temperature gradients. These forces lead to material transport and structure formation on short time and length scales. A surface tension gradient triggers the biased migration of atoms from hot to cold regions by surface diffusion. A periodic temperature gradient along a nanowire might be achieved by a surface-plasmon-polariton (SPP) wave. For SPP excitations with long wavelengths (e.g. by a CO2 laser), sufficiently strong steady-state temperature gradients may be produced. However, pulsed operation might be necessary for shorter wavelengths. We predict that the regularity of nanodroplet chains, that form during a self-organized disintegration of nanowires, might be considerably improved by SPPs. If the SPP wavelength is commensurable with the inherent Rayleigh wavelength of the nanowire disintegration, the SPP-induced temperature undulations control the Rayleigh instability. Thus, a regular and long-range order in nanodroplet size and position may be achieved.

Partial depletion of the primary circuit of a pressurized water reactor during a postulated small break loss of coolant accident can lead to interruption of one-phase flow natural circulation. In this case, the decay heat is removed from the core in the reflux-condenser mode. In this operation mode, slugs of lower borated water can accumulate in the cold legs. After refilling of the primary circuit, the natural circulation in the two loops not receiving emergency core cooling injection (ECC) re-establishes and the lower borated slugs are shifted towards the reactor pressure vessel (RPV). Entering the core, the lower borated water causes a reactivity insertion. Mixing inside the RPV is an important phenomenon limiting the reactivity insertion and preventing a re-criticality.
The mixing of these lower borated slugs with the ambient coolant in the RPV was investigated at the 1:5 scaled coolant mixing test facility ROCOM. Wire mesh sensors based on electrical conductivity measurement are used in ROCOM to measure in detail the spreading of a tracer solution in the facility. The mixing in the downcomer was observed with a sensor which spans a measuring grid of 64 azimuthal and 32 positions over the height. The resulting distribution of the boron concentration at the core inlet was measured with a sensor integrated into the lower core support plate providing one measurement position at the entry into each fuel assembly.
The boundary conditions for the mixing experiment were taken from an experiment at the thermal-hydraulic test facility PKL operated by FANP Germany. The slugs, which have a lower density, accumulate in the upper part of the downcomer after shifting into the RPV. The ECC-water injected into the RPV falls almost straight down through the lower borated water and accelerates. On the outer sides of the ECC-streak, lower borated coolant admixes and flows together with the ECC-water downwards. This is the only mechanism of transporting the lower borated water into the lower plenum. All these effects could be visualized and quantified by the downcomer sensor. On the way to the core, the lower borated water is effectively mixing with the ambient, high borated water. Therefore, in the core inlet plane, lower borated water is detected only in the outer part. The minimum boron concentration, measured at one fuel element inlet position at one certain time point, was 71 % of the initial 2500 ppm. There is no change of the initial boron concentration in the inner part of the core inlet plane during the whole transient at all.

Different parametrizations for the Stillinger-Weber potential are used to determine the elastic properties and the melting point of Ge as well as the stability, the structure and the energetics of potential vacancy and self-interstitial configurations. The results are compared with literature data obtained from experiments and by tight-binding and density-functional theory calculations. Furthermore, the vacancy and self-interstitial migration is investigated for temperatures between 600 and 1200 K. The defect diffusivity, the self-diffusion coefficient per defect and the corresponding effective migration barriers are determined. These results are compared with experimental data on self-diffusion in Ge.

Sigma receptors are membrane-bound proteins having high affinities for a variety psychotropic
drugs with opiate-type structures. The sigma receptor subtypes, sigma-1 and sigma-2, have different molecular weights and pharmacological roles.1 Many cancer cell lines (breast, melanoma, prostate cancer) express high levels of sigma receptors,2,3 and proliferative tumor cells express much higher levels of sigma-2 receptors than quiescent cells.4,5 Thus, the sigma-2 receptor has been proposed as a suitable target for imaging proliferative tumor cells.

While many ligands are selective for the sigma-1 receptor or are nonselective, very few ligands
are selective for the sigma-2 receptor. A radiopharmaceutical based on an azabicyclo[3.3.1]nonane framework was developed by Mach,6 who demonstrated that the rhenium surrogate showed exceptional sigma-2 selectivity; later this agent was labeled with technetium-99m by Kung for tissue distribution studies.7 In considering potential fluorine-18
labeled sigma-2 receptor ligands, our attention focused on members of an indole piperidine series, especially 1 (LU 28-179), which is reported to have a remarkably high sigma-2 binding affinity and selectivity.8,9 Figure 1. The structure of indole piperidine ligands and their inhibition constants toward sigma receptors.

Target compounds 1 and 2 were prepared in several steps by a route based on a previously
described method,7 with modifications making it more efficient for the synthesis of the precursor molecule (3); compounds 1 and 2 showed high binding affinity and good selectivity (6 fold) for the sigma-2 receptor (Figure 1). The preparation of [¹⁸F]-labeled indole piperidine [¹⁸F]1 was achieved in two steps from a o-nitroaldehyde precursor (3). Aromatic [¹⁸F]fluorination was not reproducible when 3 was treated with F-18 fluoride in the presence of Bu4NOH under microwave heating conditions. However, by using F-18, K₂CO₃ and kryptofix[2.2.2] under microwave heating, we obtained radiochemical yields of 5-50%. The final decarbonylation step with Wilkinson’s catalyst was studied in various solvents. Decarbonylation using dioxane as solvent produced [¹⁸F]1, but with toluene, extensive decomposition resulted. Herein, we present the synthesis of precursor 3, optimization of [¹⁸F]fluorination, and decarbonylation to produce [¹⁸F]Lu 28-179 (Scheme 1). Future work to prepare [¹⁸F]1 will be done using an alternate synthetic route.10
Supported by DOE grants 86ER60401 (to JAK) and 84ER60218 (to MJW).
Ref)
1. Vilner, B. J. et al. Cancer Res. 55: 408-413 (1995)
2. John, C. S. et al. Cancer Res. 59: 4578-4583 (1999)
3. Quirion, R. et al. Trends Phrmacol. Sci. 13: 85-6 (1992)
4. Mach, R. H. et al. Cancer Res. 57: 156-161 (1997)
5. Wheeler, K. T. et al. Br. J. Cancer 82: 1223-1232 (2000)
6. Mach et al., J. Labelled Cmpds Radiopharm 2001; 44: 899-908
7. Choi, S.-R. Nucle. Med. Biol. 28: 657-666 (2001)
8. Perregaard, J. J. Med. Chem. 38: 1998-2008 (1995)
9. Moltzen, E. K. J. Med. Chem. 38: 2009-2017 (1995)
10. Wüst, F. et al. J. Label. Compd. Radiopharm. 48: 31-43 (2005)

Two bacterial strains, Iso2 and Iso3, were cultured from a uranium mining waste pile near the town of Johanngeorgenstadt, Germany. The 16S rRNA gene sequence analysis demonstrated that these strains belong to the genus Arthrobacter of Actinobacteria. In this work, a combination of wet chemistry, spectroscopic, microscopic and microbiological methods were used to assess the stress response of these strains to heavy metals. The studied strains, Arthrobacter sp. Iso2 and Iso3, tolerate -lead, -nickel, and -uranium in concentrations up to 0.5 mM, 18 mM, and 1 mM respectively. As was demonstrated by X-ray powder diffraction (XRD) analysis, the cells of these two strains precipitate lead as lead sulfide (galena). Transmission electron microscope (TEM) showed that these precipitates are localized mainly at the cell surface. Dead/live staining indicated that 60% of the lead-treated cells are viable. Polyacrylamide gel electrophoretic (PAGE) analysis of total bacterial proteins showed different profiles between the Pb-treated and the -untreated (control) cells. The amount of a 55 kDa protein was higher in lead-treated cultures than in the control cultures. The origin of sulfide involved in lead precipitation will be discussed in term of microbial activity .

In order to expand the photon version of the Monte Carlo transport program AMOS PE to an adjoint photon version the theory of adjoint radiation transport is resumed and evaluated in this regard. All relevant photon interactions, photoelectric effect, coherent scattering, incoherent scattering and pair production, are taken into account as proposed in the EPDL 97. In order to simulate pair production and to realise physical source terms with discrete energy levels, an energy point detector is used. To demonstrate the qualification of AMOS Pt a simple air-over ground problem is simulated by both the forward and the adjoint programs. The results are compared and total agreement is shown.

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Diamond-like carbon (DLC) films with addition of atmospheric air to benzene were prepared by DC discharge plasma enhanced chemical vapor deposition (PECVD). These films were compared with films made from benzene/argon mixture. Some properties of the films including their optical transmission, hydrogen content and Raman spectra were investigated. It was found that such films fabricated with air addition (even at low vacuum) exhibit properties suitable for optical applications.

Mining on uranium ores in Eastern Germany produced 220,000 metric tons of uranium (U) in addition to ~5•108 metric tons of radioactive waste on 3000 dumps and 20 tailings, and leaving a total subsurface void volume of >1•108 m3 to be flooded. For a reliable assessment of the U migration, knowledge on the molecular speciation and complex stability is crucial. Starting from field studies and mesocosm-scaled simulation of a mine flooding scenario, we performed coprecipitation batch experiments with U(VI) and newly formed, initially colloidal 2-line ferrihydrite at different pH and ion matrix conditions. The talk presents major results of the colloid characterization, and of spectroscopic investigations on the molecular bonding of the colloid-borne U using Extended X-ray Absorption Fine Structure (EXAFS) and Attenuated Total Reflectance Infrared (ATR IR) spectroscopy. The influence of carbonate on the U(VI)-ferrihydrite surface complex formation will be discussed.
In addition, some U-loaded precipitates and a sediment sample from a uranium mine were subjected to consecutive leaching experiments and thermally induced aging. These experimental approaches aimed at determining the kinetics of U desorption processes and obtaining preliminary information on the long-term stability of U-binding. According to our results, part of the adsorbed uranium seems to be bound irreversibly within the bulk precipitate, especially when the U-sorbing ferrihydrite phase altered to hematite.
In summary, the presented results show that the interaction of U(VI) and highly reactive functional groups of colloidal and aggregated ferrihydrite surfaces can play a major role in lowering or delaying the release of toxic U from flooded uranium mines into adjacent groundwater aquifers or surface waters.

CFD-Codes ist der Oberbegriff für Rechenprogramme zur mehrdimensionalen numerischen Strömungssimulation. Mit der heute verfügbaren Rechentechnik und fortgeschrittenen numerischen Methoden können bereits komplizierte Strömungsfelder, wie sie unter anderem in der Automobil- und Luftfahrtindustrie auftreten, berechnet werden. Von dem, was bei reinen Gas- oder Flüssigkeitsströmungen schon breite Anwendung findet, ist man im Fall zwei- oder mehrphasiger Strömungen jedoch noch weit entfernt. Wenn, wie beispielsweise in einem Kernreaktor, ein Zweiphasengemisch aus Dampf und Wasser die Brennelemente kühlt, dann müssen zusätzlich die Wechselwirkungen zwischen den beiden beteiligten Phasen beschrieben werden. Im Rahmen einer Initiative des BMWA zur "Entwicklung und Anwendung von CFDProgrammen für Phänomene im Kühlkreislauf von Leichtwasserreaktoren" werden Arbeiten zur Ertüchtigung des CFD-Codes CFX von ANSYS gemeinsam vom Institut für Sicherheitsforschung des Forschungszentrum Rossendorf (FZR) und dem Codeentwickler, der ANSYS Germany GmbH durchgeführt. Ausgehend von experimentellen Daten, die an der TOPFLOW-Versuchsanlage des FZR mit innovativer, hochauflösender Messtechnik gewonnen werden, erfolgt die Entwicklung neuer Modelle und Konzepte. Diese werden mit vereinfachten Methoden getestet und nach erfolgreichem Test vom Codeentwickler in CFX implementiert. Anschließend erfolgt die gemeinsame Validierung der Modelle an Hand experimenteller Daten. Dieses Vorgehen wird am Beispiel der der Modellentwicklungen für Blasenströmungen demonstriert.

This paper deals with the speciation of U(VI) associated with the cells of bacterial strains isolated from extreme habitats as function of pH. For this propose, a combination of synchrotron-based X-ray absorption spectroscopy (XAS), time-resolved laser-induced fluorescence spectroscopy (TRLFS), transmission electron microsocpe (TEM) coupled with energy dispersive-X ray (EDX) analysis and electron diffraction were used. XAS analysis indicated that the effect of pH on the local coordination of U in the U-complexes formed by the different bacterial strains is species specific. No structural differences were found between the U complexes formed by three different exo-types of Acidothiobacillus ferrooxidans at pH 2, 3 and 4.5. In contrast, the cells of Bacillus sphaericus JG-B7, Microbacterium oxydans M2, and Sphingomonas sp. S15-S1 precipitate U(VI) as a meta-autunite-like phase at pH 4.5, probably due to the release of the inorganic phosphate from the cells. At pH 2, the U is coordinated to the organic phosphate groups of the cells of the listed bacteria. Both organic and inorganic uranyl / bacterial complexes were formed at pH 3. TEM/EDX analysis confirm these results and showed strain-specific extracellular and/or intracellular uranium accumulation to varying degrees. We applied Iterative Target Test Factor Analysis to determine the uranium speciation at different pH values quantitatively from the EXAFS spectra. Different hypothesis explaining the different coordination chemistry of uranium to bacteria as a function of pH of uranium solution in terms of solubility of m-autunite and/or microbial activity will be discussed.

In-beam PET als eine Möglichkeit zur Qualitätssicherung für die Bestrahlung hat sich bereits in der Therapie mit Schwerionen bewährt. Für Protonen und Helium wurden erfolgreich Experimente durchgeführt. Da die Strahlentherapie mit Photonenstrahlung auch auf Photonen hoher Energien (größer 20 MeV) ausgeweitet wird, könnte in-beam PET dabei eingesetzt werden. Erste Experimente dazu wurden an ELBE (Elektronen Linearbeschleuniger für Strahlen hoher Brillianz und niedriger Emittanz) im Forschungszentrum Rossendorf durchgeführt. Durch Auftreffen der Elektronen (I = 80 µA) auf ein Aluminium-Target wurde Bremsstrahlung erzeugt und sowohl homogene PMMA-, als auch inhomogene gewebeäquivalente Phantome bestrahlt. Nach Ende der Bestrahlung wurde die Verteilung der im Phantom erzeugten Positronenemitter in einem PET-Scanner (Siemens ECAT EXACT HR+) ausgemessen. Die im Phantom applizierte Dosis wurde mittels optisch stimulierter Lumineszenzdosimeter (BeO) ermittelt. In insgesamt 16 Experimenten konnten die Abhängigkeiten der erzeugten Aktivität von der Elektronenenergie (E = 21 ... 34 MeV), der Dosis (D = 1 ... 10 Gy), der Kollimation des Photonenstrahls, sowie des Phantommaterials untersucht werden. Die Experimente und die Ergebnisse für Produktionsrate und dosisbezogene Aktivitätskonzentration werden vorgestellt.

We present a combined numerical and analytical approach to analyze the static and dynamic stability of an electromagnetically levitated spherical body depending on the ac frequency and the configuration of a three-dimensional (3-D) coil made of thin winding which is modelled by linear current filaments. First, we calculate numerically the magnetic vector potential in grid points on the surface of the sphere and then use Legendre and fast Fourier transforms to find the expansion of the magnetic field in terms of spherical harmonics. Second, we employ a previously developed gauge transformation to solve analytically the 3-D electromagnetic problem in terms of the numerically obtained expansion coefficients. Using this solution, we obtain the electromagnetic reaction force due to both a small displacement of the sphere from its equilibrium position and its velocity of motion which are defined by symmetric stiffness and damping matrices, respectively. Eigenvalues and eigenvectors of the stiffness matrix yield three principal stiffness coefficients, which all have to be positive for the equilibrium state to be statically stable, and three mutually orthogonal directions of principal oscillations. Dynamic instabilities are characterized by critical ac frequencies which, when exceeded, may result either in a spin-up or oscillations with increasing amplitude. The effective electromagnetic damping coefficients are found by using a classical eigenvalue perturbation theory. A new theoretical approach based on the vector field transformation by a small rotation in combination with a parametric frequency derivative is introduced to find the electromagnetic reaction torque due to a slow rotation of the sphere in a 3-D ac magnetic field.

We consider experimentally transitions in a liquid metal cylinder heated from below and subject to superimposed rotating and static magnetic fields. Being itself unstable, a strong enough rotating magnetic field driven flow suppresses considerably the temperature fluctuations due to the thermo-gravitational convection. The remaining fluctuations are caused by unsteady Taylor vortices generated near the side wall. Our experiment shows that the superimposed static `cusp' field further reduces the amplitude and characteristic period of these remaining temperature fluctuations while a superimposed uniform axial field has no such effect. The observed behavior agrees quantitatively with the differing effects of various static fields on the additional unstable Taylor vortex type solutions, which bifurcate sub-critically and actually govern the transition in the RMF driven flow. Thus, the observations are consistent with the description of a turbulent shear flow as a trajectory wound irregularly on the skeleton of the additional unstable flow states. If this `skeleton' is compressed by an external influence (the `cusp' static field in our case), then also the averaged amplitude of turbulent fluctuations decreases by the same factor.

The paper describes actual CFD approaches to subcooled boiling and investigates their capability to contribute to fuel assembly design. In a prototype version of the CFD code CFX a wall boiling model is implemented based on a wall heat flux partition algorithm. It can be shown, that the wall boiling model is able, to calculate the cross sectional averaged vapour volume fraction with good agreement to published measurements. The most sensitive parameters of the model are identified. Needs for more detailed experiments are established which are necessary to support further model development. Nevertheless in the paper the model is applied for the investigation of the phenomena inside a hot channel in a fuel assembly. Here the essential parameter is the critical heat flux. Although subcooled boiling represents only a preliminary state toward critical heat flux essential parameters like the swirl, the cross flow between adjacent channels and concentration regions of bubbles can be determined. By calculating the temperature at the rod surface the critical regions can be identified which might later on lead to departure from nucleate boiling and possible damage of the fuel pin. The application of up-to-date CFD with a subcooled boiling model for the simulation of a hot channel enables the comparison and the evaluation of different geometrical designs of the spacer grids of a fuel rod bundle.

In this paper a forced convective boiling of Refrigerant R-113 in a vertical annular channel has been simulated by a custom version of the CFX-5 code. The employed subcooled boiling model uses a special treatment of the wall boiling boundary, which assures the grid invariant solution. The simulation results have been validated against the published experimental data. In general a good agreement with the experimental data has been achieved, which shows that the current model may be applied for the Refrigerant R-113 without significantly changing the model parameters. The influence of non-drag forces, bubble diameter size and interfacial drag model on the numerical results has been investigated as well.

Die Untersuchung der Freisetzung, des Transports und der Sedimentation von Mineralwollpartikeln in der Sumpfströmung gewinnt wachsende Beachtung bezüglich des Langzeitverhaltens der Notkühlsysteme von Druck- und Siedewasserreaktoren. Das bei einem Leck freigesetzte Isolationsmaterial besteht bezüglich Größe, Form, Konsistenz und anderen Eigenschaften aus einem Gemisch von sehr unterschiedlichen Partikeln. Ein Teil dieser freigesetzten Fasern kann in den Sumpf gelangen und durch Anlagerung an den Sumpfsieben die Notkühlung beeinträchtigen. Offene Fragen von allgemeinem Interesse sind z. B. die Ablagerung von Isolationsmaterial, die mögliche Re-Suspension und der Transport in einer Wasserströmung, die Anlagerung des Isolationsmaterials an die Sumpfsiebe und der daraus resultierende Differenzdruck.
Ein gemeinsames durch das BMWA gefördertes Forschungsprojekt in Zusammenarbeit mit dem Institut für Prozesstechnologie, Automatisierung und Messtechnik (IPM) in Zittau befasst sich mit der experimentellen Untersuchung und der Entwicklung von CFD-Modellen zur Beschreibung von Partikeltransportphänomenen in der Kühlmittelströmung. Während die Experimente am IPM Zittau durchgeführt werden, ist die theoretische Arbeit am Forschungszentrum Rossendorf konzentriert.
In der vorliegenden Arbeit werden die grundlegenden Konzepte der CFD-Modellierung beschrieben und erste Ergebnisse einschließlich Machbarkeitsstudien beschrieben.

The processes in the synthesis of a thin layer of the semiconducting iron silicide (beta-FeSi2) on the surface of a single-crystal Si(111) substrate by implantation of 195 keV Fe ions with a dose of 8×1017 cm–2 are investigated. Using Rutherford backscattering spectrometry, x-ray diffraction and cross-sectional transmission electron microscopy, the structure and the phase composition of the synthesized layers are studied. The infrared transmittance spectra show the absorption at 310 cm–1 as an indication of the initial nucleation of beta-FeSi2 precipitates during the implantation of iron into silicon substrate.

Im Vortrag werden Ergebnisse der Arbeiten des Instituts für Radiochemie im Rahmen des vom BMWi-geförderten Huminstoff-Verbundprojekts "Migration von Actiniden im System Ton, Huminstoff, Aquifer" vorgestellt.

The spectrum of the spherically symmetric α²-dynamo is studied in the case of idealized boundary conditions. Starting from the exact analytical solutions of models with constant α²-profiles a perturbation theory and a Galerkin technique are developed in a Krein-space approach. With the help of these tools a very pronounced α²-resonance pattern is found in the deformations of the spectral mesh as well as in the unfolding of the diabolical points located at the nodes of this mesh. Non-oscillatory as well as oscillatory dynamo regimes are obtained. A Fourier component based estimation technique is developed for obtaining the critical α²-profiles at which the eigenvalues enter the right spectral half-plane with nonvanishing imaginary components (at which overcritical oscillatory dynamo regimes form). Finally, Fréchet derivative (gradient) based methods are developed, suitable for further numerical investigations of Krein-space related setups like MHD α²-dynamos or models of PT-symmetric quantum mechanics.

The mean field α²-dynamo of magnetohydrodynamics (MHD) plays a similarly paradigmatic role in MHD dynamo theory like the harmonic oscillator in quantum mechanics. In its kinematic regime this dynamo is described by a linear induction equation for the magnetic field. For spherically symmetric α²-profiles α(r) the vector of the magnetic field can be decomposed into poloidal and toroidal components and expanded in spherical harmonics. In the present contribution the spectrum of the spherically symmetric α²-dynamo is studied in the case of idealized boundary conditions. Starting from the exact analytical solutions of models with constant α²-profiles a perturbation theory and a Galerkin technique are developed in a Krein-space approach. With the help of these tools a very pronounced α²-resonance pattern is found in the deformations of the spectral mesh as well as in the unfolding of the diabolical points located at the nodes of this mesh. Non-oscillatory as well as oscillatory dynamo regimes are obtained. Finally, Fréchet derivative (gradient) based methods are developed, suitable for further numerical investigations of Krein-space related setups like MHD α²-dynamo or models of PT−symmetric quantum mechanics.

We propose a method for deterministic implantation of single atoms into solids which relies on a linear ion trap as an ion source. Our approach allows a deterministic control of the number of implanted atoms and a spatial resolution of less than 1 nm. Furthermore, the method is expected to work for almost all chemical elements. The deterministic implantation of single phosphor or nitrogen atoms is interesting for the fabrication of scalable solid state quantum computers, in particular for silicon and diamond based schemes. A wide range of further applications is expected for the fabrication of nano and sub-nano electronic devices.

kein Abstract vorhanden

The quadrupole moment of the 8+ yrast state in 84Kr was measured using the level-mixing spectroscopy technique to be Q = 36(4) efm2. The result is compared with predictions of the shell model using common sets of effective charges. The comparison of experimental quadrupole moments with calculated values for 8+ states in Kr, Sr and Zr isotopes with N = 48, 50 and for 9/2+ states in isotopes with N = 47, 49 suggests a modification of the effective charges used in this region.

We investigated the local atomic and electronic structures of two related systematic sets of ternary uranium oxides, NaUO3 - KUO3 - RbUO3 and BaUO3 - Ba2U2O7 - BaUO4, by measuring the X-ray absorption near edge structure (XANES). The results are compared with calculations based on self-consistent real space full multiple scattering analysis. We found a very good agreement between measured and calculated spectra, which indicates that the uranium ions are in pure U5+ oxidation state in these compounds. The low energy shoulder observed in the U L3 edge XANES is an intrinsic feature of the uranium unoccupied 3d electronic state of the U5+ ions. Specific double shoulder features in the higher energy range of the U L3 edge XANES can be interpreted as indicative of the pure cubic perovskite structure.

The preferred orientation and thermal stability of MAX phase (M: early transition metal; A: A group element; X: C and/or N) Ti2AlN thin films sputtered onto MgO(111) and Al2O3(0001) substrates have been investigated by in situ x-ray diffraction and Rutherford backscattering (RBS). Low-temperature deposition results in epitaxial growth with inclined basal planes. An increased substrate temperature changes the preferred orientation to a parallel basal plane growth. In contrast to high bulk thermal stability, thin films decompose in vacuum already at 800°C by outward Al diffusion, followed by de-twinning of the remaining Ti2N slabs and concurrent TiN and Ti4AlN3 formation.

In the environment uranium is one of the ubiquitous elements. One million tons of uranium metal have been produced so far. Between 1945 and 1990 about one quarter of the total world production of uranium have been mined and milled in Eastern Germany. Especially these former intense uranium mining and milling activities have caused contaminations within urban areas.

In the hexavalent oxidation state uranium is soluble in aqueous media. The determination of different species with non-invasive methods can be performed by Time-Resolved Laser-Induced Fluorescence Spectroscopy (TRLIFS) under natural conditions. This is due to the different fluorescence emission and fluorescence lifetime of the varying uranium species.
The concentration of uranium ranges from the upper ng/L scale for table waters to the mg/L scale for mining related seepage and surface waters of the tailing ponds. From speciation calculations uranium in the most of these waters should be found as carbonate species. Unfortunately the carbonate species show poor fluorescence properties under ambient temperatures. By cooling of the samples to temperatures below 220 K an increase in the fluorescence intensity and lifetime can be observed. The dynamic quench effect of the carbonate ion decreases with decreasing temperature. Therefore the direct determination of the uranium speciation also in drinking waters can be performed. Examples of uranium carbonate speciation in a wide variety of natural waters will be given.

As an example, the dependence of the uranium speciation on pH of a tailing pond water was detected in detail by TRLIFS measurements. This water contains complexing anions like carbonate, phosphate, arsenate and sulphate. The uranium speciation in this surface water is strongly changed with pH. At pH 5 uranium arsenate species are dominating. The fluorescence emission of this species is in good agreement with data obtained from the uranium mineral troegerite.

Dynamics of the Molten Salt Reactor, one of the 'Generation IV International Forum' concepts, was studied in this paper. The graphite-moderated channel type MSR was selected for the numerical simulation. The MSR represents a liquid fueled reactor and its dynamics is very specific because of two physical peculiarities: the delayed neutrons precursors are drifted by the fuel flow and the fission energy is immediately released directly into the coolant. Presently, there are not many accessible numerical codes appropriate for the MSR simulation, therefore the DYN3D-MSR code was developed based on the Light Water Reactor dynamics code DYN3D. It allows calculating of full 3D transient neutronics in combination with parallel channel type thermal-hydraulics. The code was validated on experimental results of Molten Salt Reactor Experiment (from Oak Ridge National Laboratory) and applied to several transients typical for the liquid fuel system. Those transients were initiated by reactivity insertion, by overcooled or overfueled fuel slug, by the fuel pump start-up or coast-down, or by the blockage of single fuel channels. In these considered transients, the response of the MSR is characterized by the immediate change of the fuel temperature according to the power level. This causes fast feedback reactivity insertion, which is negative in the case of power increase. On the other hand, the graphite response is slower and its feedback coefficient is in some cases positive. The addition of erbium to the graphite can ensure the negative feedback and inherent safety features. The DYN3D-MSR code has been shown to be an effective tool for MSR dynamics studies.

The HADES (High Acceptance Di-Electron Spectrometer) is a tool designed for lepton pair (e+e-) spectroscopy in pion, proton and heavy ion induced reactions in the 1-2 A GeV energy range. One of the goals of the HADES experiment is to study in-medium modifications of hadron properties like effective masses, decay widths, electromagnetic form factors etc. Such effects can be probed with vector mesons (rho , omega , phi ) decaying into e+e- channel. The identification of vector mesons by means of a HADES spectrometer is based on invariant mass reconstruction of e+e- pairs. The combined information from all spectrometer sub-detectors is used to reconstruct the di-lepton signal. The recent results from 2.2 GeV p+p, 1 A GeV and 2 A GeV C+C experiments are presented.

The sorption characteristics of U and Cs on bentonite and montmorillonite were investigated in batch experiments to understand the near-field behaviour in geological nuclear repositories. The pH dependence and the retention of Cs are small and only caused by cation exchange. For the U sorption, maxima were found between pH 5.5 to 6.0 and at pH > 10.5. The linear sorption isotherm indicates only one binding type.
The retention of Cs in the concentration range between 3·E-9 and 1·E-4 mol/L on bentonite and montmorillonite (KD between 30 and 189 mL/g, retention from 7 to 31 %) is low compared to U (KD between 430 and 31500 mL/g, retention from 50 to 100 %)

This work is supported by the European Commission (NF-PRO C2-ST-C-01)

We studied the U(VI) sorption onto kaolinite in batch experiments in the absence and presence of humic acid (HA) under different experimental conditions: [U]0 = 1×10-6M or 1×10-5 M, [HA]0 = 10 or 50 mg/L, I = 0.1 M or 0.01 M NaClO4, pH = 3 – 10, CO2 or N2 atmosphere. The study showed that the U(VI) sorption onto kaolinite is influenced by pH, CO2 and HA presence. In the absence of CO2, the U(VI) uptake increases with increasing pH value up to pH 6. Above pH 6 it remains unchanged. Because of the formation of negatively charged uranyl carbonate complexes, the decrease in the U(VI) sorption onto the negative surface of kaolinite was observed above pH 8 in the presence of CO2. In presence of HA, the adsorption of U(VI) closely follows the adsorption of HA. In the acidic pH range the U(VI) uptake is enhanced compared to the system without HA due to the formation of additional binding sites for U(VI) coming from HA adsorbed onto kaolinite. The formation of aqueous uranyl humate complexes reduces the U(VI) sorption in the near neutral pH range. The enhancement of the U(VI) concentration from 1×10-6 M to 1×10-5 M results in the shift of the sorption pH edge by one pH unit to higher pH values. The ionic strength has only a slight influence on the U(VI) sorption onto kaolinite, whereas the HA sorption shows a dependence on the ionic strength.

Overview of electroproduction experiments on light nuclei

Report on RPC test at the FZ Rossendorf ELBE linac

The speciation of curium(III) with L-Threonine and O-Phospho-L-Threonine was determined by time-resolved laser-induced fluorescence spectroscopy (TRLFS) at trace Cm(III) concentrations (3x10-7 M).
Curium species of the type MpHqLr were identified in the L-Threonine- and O-Phospho-L-Threonine system. These complexes are characterized by their individual luminescence spectra and luminescence lifetimes. The following formation constants were determined a) for L-Threonine: log β101 = 6.72 ± 0.07, log β102 = 10.22 ± 0.09, and log β1-22 = -(7.22 ± 0.19) at ionic strength I = 0.5 M and b) for O-Phospho-L-Threonine: log β121 = 18.03 ± 0.13 and log β111 = 14.17 ± 0.09 at ionic strength I = 0.154 M. Possible structures of the identified curium species will be discussed on the basis of the luminescence lifetime measurements and the magnitude of the formation constants.

The ion implantation induced interfacial mixing and subsequent amorphization of ultrathin Ni81Fe19/Ta bilayers has been investigated by TRIDYN simulations and cross-sectional transmission electron microscopy. Due to the 30 keV Ni implantation the initially sharp interface between Ni81Fe19 and Ta broadens and an intermixing between both layers is observed. Consequently the Ni81Fe19 layer is increasingly doped with Ta in the interface near region. For the region exhibiting a Ta concentration above a threshold value of about 20 atom-% irradiation induced amorphization takes place. For an increasing Ni implantation fluence this region is succeedingly enlarged. A quantitative agreement between simulations and experimental data is found.

Der Washout der Positronenemitter bei in-beam PET

In-beam PET wird am experimentellen Schwerionentherapieplatz an der Gesellschaft für Schwerionenforschung (GSI) Darmstadt bereits erfolgreich eingesetzt. Durch Vergleich der simulierten Positronen-emitterverteilung mit der gemessenen sind Aussagen zur Reichweite des Kohlenstoffstrahls möglich, es können anatomische Veränderungen detektiert werden und die Feldlage kann beurteilt werden. In der Simulation werden alle Prozesse von der Erzeugung der Positronenemitter bis zum Nachweis der Photonen im Detektor behandelt. Im lebenden Gewebe jedoch nehmen die Positronenemitter an metabolischen Vorgängen teil. Es kommt zum Transport und der Annihilationsort kann vom Erzeugungsort verschieden sein.
Durch Auswertung von Messungen an Patienten kann eine effektive Halbwertszeit bestimmt werden, die sich aus der physikalischen und der biologischen Halbwertszeit zusammensetzt. Die physikalische Halbwertszeit wird nur durch die Stöchiometrie des Gewebes und die Bestrahlungsdauer determiniert. Die biologische Halbwertszeit unterliegt dagegen vielfältigen Einflüssen, die in der vorliegenden Arbeit untersucht wurden. Die Berücksichtigung der effektiven Halbwertszeiten verbessert die Simulation.

Bei der Radiotherapie von Tumoren erlauben Ionenstrahlen auf Grund ihrer physikalischen und biologischen Eigenschaften ein höheres Maß an Präzision und Wirksamkeit als die konventionellen Strahlenmodalitäten, Photonen und Elektronen. Ein in-situ Monitoring der Dosisapplikation ist deshalb für die Qualitätssicherung der Ionentherapie in hohem Maße wünschenswert. Das einzige gegenwärtig bekannte, dafür geeignete Verfahren ist die in-beam Positronen-Emissionstomographie (PET). Dabei werden während der Tumorbestrahlungen Annihilationsereignisse registriert, die in Folge des Zerfalls von Positronenemittern auftreten, welche durch nuklare Wechselwirkungen zwischen den Projektilen des Therapiestrahles und den Atomkernen des Gewebes erzeugt werden. In die experimentelle Ionentherapie-Anlage an der Gesellschaft für Schwerionenforschung Darmstadt wurde ein in-beam PET-Scanner integriert und die Methode erstmals klinisch angewendet. An dieser Anlage wurden seit 1997 etwa 300 Patienten, vornehmlich mit stahlenresistenten Tumoren in komplizierten anatomischen Positionen im Kopf-Hals-Bereich mit Kohlenstoff-Ionenstrahlen behandelt. Alle Bestrahlungen wurden mit PET kontrolliert.Die nunmehr vorliegenden Erfahrungen erlauben gesicherte Aussagen zum Potential der in-beam PET für die Qualitätssicherung der Ionentherapie.

Abstract not available

The paper presents the method of determination of mass transfer coefficient in electromagnetic stirred liquid phase based on Lamont, Scott and Kolmogorov turbulent models. For this purpose the numerical model allowing the determination of electromagnetic force and turbulent filed was utilized. As result the values of Lorentz forces and metal surface velocity have been determined. Calculations were made for IS5/III Leybold Heraeus induction furnace.

The Institute of Radiochemistry (IRC), one of the six institutes of the Forschungszentrum Rossendorf (FZR), performs application-oriented research in the fields of radiochemistry and radioecology. Motivation and background of our research are environmental processes relevant for the installation of nuclear waste repositories, for remediation of uranium mining and milling sites, and for radioactive contaminations caused by nuclear accidents and fallout. Due to their high radiotoxicity and long half-life the actinides are of special interest. Hence our research focuses on the chemical behavior of actinides at the molecular level in order to predict the relevant macroscopic processes in the environment.
Within this framework, special emphasis is on the interface between geological and biological systems.
In the last year our research topics were as follows:
– Aquatic chemistry of actinides
– Actinides in bio-systems
– Interaction of actinides with solid phases
– Reactive transport of actinides
About 60 scientists, technicians and PhD students are employed in the Institute of Radiochemistry.
We have achieved a wide range of new scientific results in the past year, which are presented in this Annual Report. Among them only a few can be highlighted here in this preface. For the first time it was possible to determine uranium speciation in situ in drinking and mineral waters e.g. by a dedicated fluorescence spectrometer at lowest μg/L concentrations. This methodical progress is an important prerequisite to study the uranium toxicity and its dependence on chemical speciation. We were very successful in the determination of formation pathways and structure of various actinide complexes, e.g., the surface complexes of uranium (VI) onto mica and iron hydroxides over a wide range of pH and carbonate concentration. These results contribute to a better understanding of actinide speciation in geo- and bio-systems, especially with respect to the chemical processes on the interfaces.
Studies to the interaction of uranium with biofilms, green algae and bacteria coming from extreme habitats extended our research on the field of bio-systems.
Major progress in the structural analysis of multiple uranium species has been achieved by applying Monte Carlo simulations and iterative transformation factor analysis to EXAFS spectroscopy.
Furthermore, our new radiochemical experimental station at the Free Electron Laser of the Rossendorf accelerator ELBE is now in full operation. We have started first experiments on the uranium and neptunium complexation on selected mineral surfaces.

A superconducting electron linear accelerator of high brilliance and low emittance (ELBE) is under operation at Forschungszentrum Rossendorf since January 2003. The first stage of ELBE is based on an electron energy of 20 MeV, whereas in the future a 40 MeV beam will be provided. The relativistic electron beam is used to drive various kinds of secondary radiation sources. Among all, X-rays in a wide energy range can be obtained. One method for production of intensive, quasi-monochromatic Xrays in the energy range 10 - 100 keV, tunable in photon energy, is by channeling of relativistic electrons in a perfect crystal. This unconventional photon source with variable time structure will be optimised and used for radiobiological studies. Its first test operation was in October 2003. This thesis is part of the first radiobiological project – the determination of relative biological effectiveness (RBE) of the X-rays in this energy range.
The most important aspects of medical application of low-energy X-rays are imaging and radiation therapy, but they can also be helpful in the study of radiation effects in living matter. However, the RBE depends on the photon energy, dose range, cell line and biological endpoint. Up to now no definitive conclusions can be made about their biological effectiveness due to the large spread of the published data. Therefore, in order to precisely determine the RBE, studies have to be performed at an intensive, tunable photon source, for several practically relevant cell lines and biological endpoints. The possibility of using channeling radiation (CR) for medical applications has been widely discussed in the literature, but building and optimisation of a dedicated source is for the first time performed at the ELBE accelerator.