Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Numerical simulations of kinematic dynamo action have been carried out in a setup that resembles the configuration of the Von-Karman-Sodium (VKS) dynamo experiment. The results show that the high permeability domains introduced by soft iron impellers essentially determine the field generation process and are also responsible for the selection of the dominating azimuthal dynamo mode.

The material heterogeneity within the fluid give rise to three distinct effects that may influence the dynamo process. In addition to the local decrease of the magnetic diffusivity eta=(mu_0\mu_r\sigma)^(-1) so called paramagnetic pumping occurs which is proportional to the gradient of the permeability and describes the suction of magnetic field into domains with high permeability. Beside the modifications of the induction equation itself, jump conditions of the magnetic field (respectively the electric field) are enforced on the material interfaces between fluid and impellers. These jump conditions and the pumping term are responsible for the distinct behavior of high conducting(i.g. copper) and soft iron impellers.

At reasonable values for the magnetic Reynolds number (i.e around Rm=30) and rather moderate permeability (around values of 60 as suggested from recent measurements) the simulated magnetic field is dominated by an axisymmetric component. However, to obtain a growing axisymmetric eigenmode still an alpha-effect is necessary that parametrizes the induction effects of helical small scale motions. In contrast to preliminary mean field models for the VKS dynamo that have been based solely on an alpha-omega mechanism, the necessary magnitude for the alpha effect remains reasonable small if soft iron impellers are utilized.

The LUNA experiment is dedicated to measure low energy cross sections of reactions of astrophysical interest. Motivating these measurements with the question about the origin and the different abundances of isotopes in our universe, the reason to perform them in a deep underground laboratory is also mentioned. Using the example of the ²H(alpha, gamma)⁶Li reaction, the measurement approach and the apparatus are introduced.

Das Nuklid 44Ti (Halbwertszeit 59 Jahre) wird in Supernovae erzeugt. Die Gamma-Strahlung aus seinem Zerfall lässt sich in weltraumgestützten Gamma-Teleskopen nachweisen und kann als Werkzeug zum Test von Supernova-Modellen genutzt werden. Hierfür ist eine genaue Kenntnis der Kernreaktionsraten für die Erzeugung und Zerstörung von 44Ti erforderlich. Die 40Ca(alpha,gamma)44Ti-Reaktion dominiert die Erzeugung von 44Ti. Ihre Rate wird von einer Vielzahl von Resonanzen bestimmt. Um präzise Daten zu gewinnen, wurde die Stärke des Resonanztripletts bei 4.5MeV Gamma-Energie am Dresdner 3MV Tandetron sowohl mittels in-beam Gamma-Spektrometrie als auch durch eine Aktivierungsmessung im Felsenkeller-Niederniveaumesslabor gemessen. Eine Untersuchung der bestrahlten Proben mittels Beschleunigermassenspektrometrie ist geplant. – Gefördert von der EU (FP7-SPIRIT 227012) und der DFG (BE 4100/2-1).

Eine der größten Herausforderungen der Gegenwart ist der verantwortungsvolle Umgang mit den Ressourcen unseres Planeten. In diesem Zusammenhang ist die Entwicklung neuartiger Verfahren zur Gewinnung und vor allem Rückgewinnung von seltenen Metallen aus Industrieprodukten als wichtige Rohstoffe zahlreicher Zukunftstechnologien von besonderer Relevanz.

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In this study, extracellular concentrations of adenosine and ATP from the rat striatum were estimated by the microdialysis technique under physiological conditions and during focal cerebral ischemia induced by middle cerebral artery occlusion (MCAo). Under these conditions, adenosine and ATP concentrations were in the range of 130 nM and 30 nM, respectively. Blocking the ecto-ATPases with the novel inhibitor polyanion [TiW₁₁CoO₄₀]^8- (PV4: 100 μM), recently synthesized and characterized by Stephan and Müller, we could demonstrate that the extracellular concentration of ATP increased 12-fold and that adenosine concentration was not modified. This result indicates that, under physiological conditions, adenosine is released per se from cells. In the presence of PV4 and of the adenosine equilibrative transporter inhibitor dipyridamole (100 μM), adenosine extracellular concentration was increased 3-fold. This result excludes the possibility that adenosine is carried out of cells by a carrier mediated efflux. By using immunolabeling and electron microscopy, we showed the presence of the CNT2 on plasma membrane of synaptic terminals and on vesicle membranes. Results suggest that under in vivo physiological conditions adenosine is transported in vesicles and is released in an excitation-secretion manner.
In the first 4 hours after in vivo ischemia induced by MCAo, adenosine increased to ~690 nM and ATP to ~50 nM. In the presence of PV4 the extracellular concentration of ATP increased to ~440 nM and extracellular adenosine decreased to ~270 nM. An upregualtion of ecto-nucleotidases after ischemia might represent an important mechanism in hydrolysis of ATP and formation of extracellular adenosine in the first hours after ischemia.

Wetting properties of ceramic materials may be enhanced by treating them with high-intensity plasma pulses carrying a substantial fraction of metallic ions. Rod Plasma Injectors (RPI), developed originally for fusion studies, may generate such plasma pulses containing the working gas used for discharge initiation and the metal ions eroded from the discharge electrodes. We examined the plasma pulse technology and concluded that it is possible to extend the range of system parameters appropriate for wetting enhancement. We also studied the physical properties of plasma treated carbon and silicon carbide samples in an attempt to disclose the origin of wettability differences between them. We finally conclude that these differences are due to the morphology of the treated surfaces.

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The most stable atomic configuration of coherent nanoclusters in bcc-Fe formed by vacancies, Cu and Ni as well as the corresponding energetics are determined by on-lattice simulated annealing and subsequent off-lattice relaxation. Ternary v_l Cu_m Ni_n clusters show a core-shell structure with vacancies in the core coated by a shell of Cu atoms, followed by a shell of Ni atoms. In binary Cu_m Ni_n clusters the Cu core is covered by a shell of Ni atoms. On the contrary, binary v_l Ni_n clusters consist of a pure vacancy cluster surrounded by an agglomeration of Ni atoms. The latter is similar to a pure Ni cluster (Ni_n) and consists of Ni atoms at the second nearest neighbor distance. In all clusters investigated Ni atoms may be nearest neighbors of Cu atoms but never nearest neighbors of vacancies or other Ni atoms. The structure obtained for Cu_m Ni_n clusters is in agreement with previous theoretical results and with indications from measurements while for the other clusters reference data are not available. It is shown that the presence of Ni atoms promotes the nucleation of clusters containing vacancies and Cu. This is in agreement with experimental observations and recent theoretical results Compact and rather accurate analytical formulae for the total binding energy have been derived from the results of the atomistic simulations. These relations can be used in rate theory or object kinetic Monte Carlo simulations of nanocluster evolution.

A series of high quality Zn_1-xCo_xO films prepared by reactive magnetron sputtering displays altered magnetic properties ranging from paramagnetic (PM) to ferromagnetic (FM)- like at room temperature. With tuning the properties of the Zn_1-xCo_xO films from PM- to FMlike, the temperature dependent resistivity of the films changes from a Mott variable-range hopping to an Efros variable-range hopping process. This indicates the emergence of a Coulomb gap, which can be explained by the presence of nanoclusters. Moreover, the anhysteretic M (H)-curves above the blocking temperature for superparamagnetic (SPM) films can be described by a Langevin function, which confirms the existence of FM nanoclusters. The investigation on the magneto-transport of these films shows no spin-dependent transport behaviour associated with the observed FM-like/SPM properties.

The rate of the carbon-nitrogen-oxygen (CNO) cycle of hydrogen burning is controlled by the 14N(p,gamma)15O reaction. The reaction proceeds by capture to the ground states and several excited states in O-15. In order to obtain a reliable extrapolation of the excitation curve to astrophysical energy, fits in the R-matrix framework are needed. In an energy range that sensitively tests such fits, new cross section data are reported here for the four major transitions in the 14N(p,gamma)15O reaction. The experiment has been performed at the Laboratory for Underground Nuclear Astrophysics (LUNA) 400 kV accelerator placed deep underground in the Gran Sasso facility in Italy. Using a composite germanium detector, summing corrections have been considerably reduced with respect to previous studies. The cross sections for capture to the ground state and to the 5181, 6172, and 6792 keV excited states in O-15 have been determined at 359, 380, and 399 keV beam energy. In addition, the branching ratios for the decay of the 278 keV resonance have been remeasured.

The CFD code ANSYS CFX has been coupled with the neutron-kinetic core model DYN3D. ANSYS CFX calculates the fluid dynamics and related transport phenomena in the reactor’s coolant and provides the corresponding data to DYN3D. In the fluid flow simulation of the coolant, the core itself is modeled within the porous body approach. DYN3D calculates the neutron kinetics and the fuel behavior including the heat transfer to the coolant. The physical data interface between the codes is the volumetric heat release rate into the coolant. In the prototype that is currently available, the coupling is restricted to single-phase flow problems. In the time domain an explicit coupling of the codes has been implemented so far.
Steady-state and transient verification calculations for a small-size test problem confirm the correctness of the implementation of the prototype coupling. The test problem was a mini-core consisting of seven real-size VVER-1000 fuel assemblies. Comparison was performed with the DYN3D stand-alone code. In the steady state, the effective multiplication factor obtained by the DYN3D/ANSYS CFX codes shows a deviation of 0.2 pcm from the DYN3D stand-alone solution. The transient test case simulated the withdrawal of the control rod from the central fuel assembly at hot zero power in the same mini-core. Power increase during the introduction of positive reactivity and power reduction due to fuel temperature increase are calculated in the same manner by the coupled and the stand-alone codes. The maximum values reached during the power rise differ by about 3 MW at a power level of 240 MW. These differences are caused by the use of different flow solvers.
After this verification a steady-state full power calculation for a full VVER-1000 reactor was carried out in order to show the applicability of the new code system to real problems. A CFX grid consisting of about 1.3 106 nodes was created. The main difference to a pure DYN3D calculation with its 1D thermal hydraulic model is the presence of a lateral coolant flow at a velocity in the order of 1 cm/s from the circumference of the core centre. It is driven by the acceleration of the liquid in the centre due to the stronger heating. This flow increases the exchange of heat in the lateral direction by advection and leads to a ‘smearing’ of the step-like temperature profile that has been found in a pure DYN3D calculation.

The control of morphology and surface composition of nanoalloys is the key factor in order to tune or to extend the range of their optical, magnetic and chemical properties. Therefore it is one of the major tasks in nanoalloy materials science. The de-wetting dynamics and kinetics dependence of a Rh-Pd bilayer/alloy thin film model system on chemical environment (CO and NO) is investigated in-situ by means of high pressure x-ray photoelectron spectroscopy. Independently of the initial state, the film surface shows an enrichment of Pd upon heating in vacuum. De-wetting caused by heating in NO or CO shows significant differences in the surface chemical composition evolution and, consequently, in the de-wetting onset temperature. Alternating exposure to NO or CO results in the surface enrichment with either Rh or Pd, respectively, and subsequent film rupture. The results are discussed on the basis of the interplay between thermodynamic and kinetic factors. The study demonstrates the effect of the chemical environment on the morphology as well as on the composition of supported nanostructures.

Die Erfindung betrifft ein Verfahren und eine Anordnung zur kontaktlosen Messung des Durchflusses elektrisch leitfähiger Medien durch Strömungskanäle. Durch die Erfindung soll eine Durchflussmessung ohne mechanischen oder elektrischen Kontakt zum fließenden Medium zu ermöglicht werden, ohne die zu messende Strömung zu beeinflussen und die unabhängig von möglichen Temperaturänderungen des fließenden Mediums eine direkte Durchflussmessung erlaubt. Erreicht wird das durch Ausbilden eines am Strömungskanal drehbaren einfach polarisierten Magnetfeldes eines Magneten (4), derart, dass die Strömung im Strömungskanal (1) ein Drehmoment auf das Magnetfeld der Magneten (4) ausübt, das proportional zum Produkt aus der elektrischen Leitfähigkeit des strömenden Mediums und dessen mittleren Geschwindigkeit ist und das den Magneten (4) in Drehung versetzt, derart, dass ein Drehmoment auf das strömende Medium im Strömungskanal (1) ausgeübt wird, welches proportional zur elektrischen Leitfähigkeit des strömenden Mediums und zur Drehzahl des sich drehenden Magneten (4) ist und nachfolgende Messung der Drehzahl des einfach polarisierten Magnetfeldes im weitgehend drehmomentlosen Zustand.

We demonstrate the coexistence of superconductivity and ferromagnetism in Bi₃Ni nanostructures that have been prepared by making use of novel chemical-reaction paths. We have characterized their magnetic and superconducting properties by means of magnetometry and electrical-transport measurements. Other than in bulk geometry, submicrometer-sized particles and quasi-one-dimensional nanoscaled strains of single-phase Bi₃Ni undergo ferromagnetic order. Superconductivity in confined Bi₃Ni emerges in the ferromagnetically ordered phase and is stable up to remarkably high magnetic fields. Uniquely, ferromagnetic hysteresis at zero resistance is observed in nanostructured Bi₃Ni.

Metal-organic materials constitute a new field in which to search for ferroelectricity and coupling between electricity and magnetism. We observe a magnetic field-induced change in the electric polarization, ΔP(H), that reaches 50 μC/m² in single crystals of NiCl₂–4SC(NH₂)₂ (DTN). DTN forms a tetragonal structure that breaks inversion symmetry with the electrically polar thiourea molecules [SC(NH₂)] all tilted in the same direction along the c axis. The field H induces canted antiferromagnetism of the Ni S = 1 spins between 2 and 12 T and our measurements show that the electric polarization increases monotonically in this range, saturating above 12 T. By modeling the microscopic origin of this magnetoelectric effect, we find that the leading contribution to ΔP comes from the change in the crystal electric field, with a smaller contribution from magnetic exchange striction. The finite value of ΔP induced by magnetostriction results from the polar nature of the thiourea molecules bonded to the Ni atoms, and it is amplified by the softness of these organic molecules.

Um die hohen Bindungskapazitäten und schnelle Mutationsrate von Bakterien, aber auch die bekanntermaßen hohen Aufnahmekapazitäten von Pilzen als Modell zu nutzen, werden die generellen, molekularen Aufnahmesysteme für Uran und die Bindungsformen in der Zelle beispielhaft für Bakterien und Pilze mit ihrer guten Bearbeitbarkeit untersucht. Dazu werden Mikroorganismen verwendet, für die molekulare Werkzeuge und Genomsequenzen vorliegen. Stämme mit Schwermetallresistenz werden genutzt, um die hier besonders stark ausgeprägten Systeme zur Entgiftung von Schwermetallen und damit auch der schweren Radioisotope zu nutzen. Der Nachweis der Aufnahme in die Zelle erfolgt durch Analyse der einzelnen zellulären Fraktionen, die mit spektroskopischen und mikroskopischen Methoden auf die vorherrschenden, molekularen Bindungsformen hin untersucht werden. Dabei werden die Modellorganismen Arthrobacter sp. JG37-Iso2 und Streptomyces acidiscabies E13 als Bakterien sowie der Weißfäulepilz Schizophyllum commune genutzt. Die Genomsequenz von Schizophyllum konnte genutzt werden, um Gene zu annotieren, die mit der Uranaufnahme zusammenhängen könnten. Dies ist nur durch Experimente wirklich möglich, da bisher keine Urantransporter in Eukarya gefunden wurden. Wir haben daher Proteomanalysen und Transkriptomanalysen durchgeführt, um die Expression unter verschiedenen Bedingungen zu testen, in denen der Pilz auf uranhaltigen Medien wächst. In Mikroarrays zeigen sich eine hohe Anzahl unterschiedlich regulierter Gene, deren Funktion experimentell überprüft wird. Ergänzend dazu wurde die Wechselwirkung von Schizophyllum mit Uran auf molekularer und zellulärer Ebene untersucht. Dabei konnte eine dominierende Wechselwirkung von Uran mit organischen Phosphatverbindungen auf und in der Zelle nachgewiesen werden. Bei der Untersuchung der Arthrobacter-Referenzstämme stellte sich heraus, dass eine Zellsorption der angebotenen U(VI) Spezies der dominante Prozess ist. Fluoreszenzspektroskopische Untersuchungen ergaben deutliche Unterschiede zwischen den U(VI) Spezies in den mineralischen Ausgangsmedien (freies U(VI), Uranylhydroxide bzw.Uranylhydroxocarbonat) und der sich über Carboxyl- und organischen Phosphatgruppen bildenden U(VI)- Spezies an der Bakterienzelle. Es konnten von schwermetallhaltigen Arealen der ehemaligen Wismut Region Pilzfruchtkörper gewonnen werden, die extrem hohe Anreicherungsfaktoren für Uran und Cäsium zeigen. Weiterhin konnte gezeigt werden, dass aus Pilzen sowie Gram-positiven und Gram-negativen Bakterien vom Standort lediglich 2 Isolate auf 50 μM Uranylacetat wachsen konnten. Diese beiden Stämme zeigten in der Laserablations-ICP-MS eine deutlich signifikante Urananreicherung im Bereich des Wachstums. Daneben wurden Streptomyces-Stämme auf ihre Resistenz gegenüber Uran getestet. Hier scheint sich ein anderer Mechanismus als bei Arthrobacter herauszustellen.

Die vorliegende Erfindung beschreibt eine Anordnung zur optischen Tomographie mit mindestens einem optischen Aufnehmer 5 und einem Untersuchungsobjekt 2 unter Verwendung von Spiegeln 1. Damit können sich schnell zeitlich verändernde oder bewegende Untersuchungsobjekte untersucht werden, ohne dass örtliche Veränderungen der optischen Aufnehmer (Kamera) oder der Spiegel notwendig sind.

Die Erfindung betrifft eine Anordnung zur optischen Visualisierung und Vermessung von mikroskopischen Vorgängen in Prozessen bei hoher Temperatur und/oder hohem Druck. Die Kamera- und die Beleuchtungseinheit sind in einem oder in getrennten Wärmeleitzylindern untergebracht um diese Einheiten vor unzulässig hohen Temperaturen, die am Prozessort auftreten, zu schützen ohne gleichzeitig einen starken Wärmeentzug aus dem Prozessmedium zu verursachen.

Ligand der Formel F1 worin (CH-R1) und (CH-R1') substituierte oder unsubstituierte Methylenbrücken darstellen, die einzelnen R1 und R1', sowie R3 und R3' jeweils unabhängig voneinander ausgewählt sind aus Wasserstoff, substituierten oder unsubstituierten Alkylgruppen, substituierten oder unsubstituierten Arylgruppen, m und n positive ganze Zahlen sind, wobei m die Anzahl der Gruppen (CH-R1') und n die Anzahl der Gruppen (CH-R1) repräsentiert, wobei die Summe aus m und n im Bereich von 4 bis 10 liegt, R2 und R2' unabhängig voneinander ausgewählt sind aus Wasserstoff, substituierten oder unsubstituierten Alkylgruppen, substituierten oder unsubstituierten Carboxylgruppen, substituierten oder unsubstituierten Arylgruppen oder Z, X eine substituierte oder unsubstituierte Methylenbrücke mit der Formel CHR4 oder eine unsubstituierte Aminogruppe (N-H) oder substituierte Aminogruppe (N-Z) ist, wobei Z für -(CH-R5)p-A steht, worin (CH-R5) eine substituierte oder unsubstituierte Methylenbrücke darstellt und p eine ganze Zahl ist, die für die Anzahl der Gruppen (CH-R5) steht, wobei p im Bereich von 2 bis 8 liegt, A eine kopplungsfähige Einheit darstellt, wobei R4 und die einzelnen R5 jeweils unabhängig voneinander ausgewählt sind aus Wasserstoff, substituierten oder unsubstituierten Alkylgruppen, substituierten oder unsubstituierten Arylgruppen.

The arrangement has an electron accelerator with accelerator cavities, and strewing targets (3) positioned between the accelerator cavities. The strewing targets are electron-optically thin. Multiple strewing targets are used between the cavities. An independent claim is also included for a method for producing individual relativistic electrons.

Die vorliegende Erfindung dient der kontaktlosen Bestimmung von Geschwindigkeitsverteilungen eines flüssigen Metalls in einer Stranggießkokille. Ein bevorzugtes Einsatzgebiet der Einrichtung ist die Geschwindigkeitsbestimmung im Strangguss von Stahl und Aluminium, insbesondere beim Brammengießen. Die Bestimmung erfolgt dadurch, dass ein primäres Magnetfeld das Flüssigmetallvolumen in der Kokille durchdringt, dass die durch die Flüssigkeitsbewegung induzierten Magnetfelder gemessen und aus diesen die Geschwindigkeit durch Lösung eines inversen Problems berechnet wird. Die Berechnung benutzt das Prinzip der kleinsten Quadrate, wobei als zu minimierendes Funktional die mittlere quadratischen Abweichungen der durch die angenommene Geschwindigkeit induzierten Magnetfelder von den gemessenen Werten benutzt wird. Dabei wird die Tichonov-Regularisierung eingesetzt, wobei als Regularisierungsfunktional die mittlere quadratische Krümmung des Geschwindigkeitsfeldes oder die mittlere quadratische Geschwindigkeit verwendet wird. Des Weiteren wird die Divergenzfreiheit des Geschwindigkeitsfeldes durch Verwendung eines zusätzlichen Funktionals gewährleistet. Die Anordnung besteht aus einem ein Magnetfeld erzeugenden Spulensystem, einer Mess- und Steuereinheit für die Ströme in diesem Spulensystem, mit welcher die Richtung des Magnetfeldes in der Flüssigkeit geändert werden kann, einer Mehrzahl von Magnetfeldsensoren im Außengebiet der Flüssigkeit zur Bestimmung der durch die Flüssigkeitsbewegung induzierten Magnetfelder sowie aus Mitteln zur Signalweiterleitung, -verarbeitung und -darstellung.

Gegenstand der Anmeldung ist eine Anordnung und ein Verfahren zur Messung der Partikelvolumenströme von Mehrphasengemischen in einem Strömungskanal, die aus einem innerhalb eines Strömungskanals eingebrachten Kanalkörper besteht, wobei über dem Kanalkörper ein Differenzdrucksensor oder vor und hinter dem Kanalkörper jeweils ein Drucksensor angeordnet ist, aus dem der Differenzdruck der beiden Drucksensoren ermittelt wird; der Kanalkörper aus einer Vielzahl von in Strömungsrichtung verlaufenden durchgängigen Kanälen mit geringem hydraulischem Durchmesser besteht; an jedem der Kanäle mindestens zwei Phasensensoren zur Identifikation der stofflichen Phase in Strömungsrichtung hintereinander angeordnet sind; alle Phasensensoren signaltechnisch mit einer zugeordneten Messelektronik verbunden sind, die gleichzeitig die Phasenindikatorsignale der Phasensensoren sowie den Messwert des Differenzdrucksensors mit hoher Abtastrate erfasst; ein in der Messelektronik integrierter oder dieser nachgeschalteter Mikrocontroller oder Rechner die Partialvolumenströme in den Kanälen sowie die mittleren Partialvolumenströme des gesamten Querschnitts des Strömungskanals aus den erfassten Messwerten berechnet.

"Collision Dynamics" is part of the CBM Physics Book.

"In-Medium Excitations" is part of the CBM Physics Book.

"Bulk Properties of Strongly Interacting Matter" is part of the CBM Physics Book.

Die vorliegende Erfindung betrifft ein E. coli-Sekretionssystem auf Basis einer S-Layer-Gensequenz, deren Expressionsprodukt die Sekretion von rekombinanten Proteinen aus E. coli-Zellen vermittelt. Das Sekretionssystem eignet sich für die Anwendung in der Molekularbiologie und in der Biotechnologie. Das erfindungsgemäße Sekretionssystem basiert auf der Verwendung eines S-Layer-Proteins, einer Teilsequenz davon oder einer dazu homologen Sequenz als Sekretionssignal. Die Erfindung umfasst weiter ein Fusionsprotein, welches ein zu exprimierendes Zielprotein und das erfinungsgemäße Sekretionssignal enthält, eine Nukleinsäuresequenz, welche für ein erfindungsgemäßes Fusionsprotein kodiert, einen Expressionsvektor oder einen Klonierungsvektor für die Herstellung eines erfindungsgemäßen Fusionsproteins, eine Wirtszelle für die Expression eines erfindungsgemäßen Fusionsproteins und einen Kit sows erfindungsgemäßen Fusionsproteins aus einer Wirtszelle.

Die Erfindung betrifft das Hohlraumresonatorsystem (HRS) supraleitender Hochfrequenz-Fotoelektronenquellen (SHFE), die in Elektronenbeschleunigern eingesetzt werden können. Die beschleunigten Elektronen können direkt genutzt oder mittels nachgelagerter Anordnungen zur Erzeugung von Sekundärstrahlen, wie Gamma-, Röntgen- oder Laserstrahlung dienen. Der Erfindung liegt die Aufgabe zugrunde, die bei den bisherigen supraleitenden Hochfrequenz-Fotoelektronenquellen unbefriedigende Frequenzstabilität wesentlich zu erhöhen. Die Aufgabe wird durch eine spezielle Konstruktion zur mechanischen Stabilisierung des Hohlraumresonanzsystems gelöst, wobei die für das supraleitende System erforderliche hohe Effektivität für die Kühlung weiterhin gewährleistet wird und eine einfache Montage des Systems unterstützt wird.

Die vorliegende Erfindung betrifft röhrenartige biologische Strukturen, die sich aus der äußeren Membran von E. coli zusammensetzen und durch heterolog exprimierte rekombinante S-Layer-Proteine stabilisiert werden. Die neuartigen Mikroröhren eignen sich für die Anwendung in der Biotechnologie, Pharmazie, in der chemischen Katalyse und in der Nanotechnologie. Die erfindungsgemäßen Mikroröhren umfassen Bestandteile der äußeren Membran von E. coli Zellen und rekombinant exprimierte S-Layer-Proteine. Die Erfindung umfasst weiter ein Verfahren zur Herstellung der erfindungsgemäßen Mikroröhren, bei dem S-Layer-Proteine in E. coli-Zellen exprimiert werden und anschließend die E. coli-Zellen ggf. aus den gebildeten Mikroröhren entfernt werden, die E. coli-Zellen, welche die rekombinanten S-Layer-Proteine exprimieren, und die Verwendung der erfindungsgemäßen Mikroröhren zur Bindung von Metall aus einer wässrigen Lösung, zur Herstellung funktionalisierter Schichten, als Carrier für Enzyme oder für pharmazeutische Wirkstoffe oder als Katalysator.

Mineral wool insulation material applied to the primary cooling circuit of a nuclear reactor maybe damaged in the course of a loss of coolant accident (LOCA). The insulation material released by the leak may compromise the operation of the emergency core cooling system (ECCS), as it maybe transported together with the coolant in the form of mineral wool fiber agglomerates (MWFA) suspensions to the containment sump strainers, which are mounted at the inlet of the ECCS to keep any debris away from the emergency cooling pumps. In the further course of the LOCA, the MWFA may block or penetrate the strainers. In addition to the impact of MWFA on the pressure drop across the strainers, corrosion products formed over time may also accumulate in the fiber cakes on the strainers, which can lead to a significant increase in the strainer pressure drop and result in cavitation in the ECCS. Therefore, it is essential to understand the transport characteristics of the insulation materials in order to determine the long-term operability of nuclear reactors, which
undergo LOCA.
An experimental and theoretical study performed by the Helmholtz-Zentrum Dresden-Rossendorf and the Hochschule Zittau/Görlitz1 is investigating the phenomena that maybe observed in the containment vessel during a primary circuit coolant leak. The study entails the generation of fiber agglomerates, the determination of their transport properties in single and multi-effect experiments and the long-term effects that particles formed due to corrosion of metallic containment internals by the coolant medium have on the strainer pressure drop.
The focus of this presentation is on the numerical models that are used to predict the transport of MWFA by CFD simulations in the containment sump. Two dispersed phases were conditions to determine the influence of entrained air from a jet on the transport of fibre agglomerates through the sump. The strainer model of A. Grahn was implemented to observe the impact that the accumulation of the fibres have on the pressure drop across the strainers. The geometry considered is similar to the containment sump configurations found in Nuclear Power Plants.

Mineral wool insulation material applied to the primary cooling circuit of a nuclear reactor maybe damaged in the course of a loss of coolant accident (LOCA). The insulation material released by the leak may compromise the operation of the emergency core cooling system (ECCS), as it maybe transported together with the coolant in the form of mineral wool fiber agglomerates (MWFA) suspensions to the containment sump strainers, which are mounted at the inlet of the ECCS to keep any debris away from the emergency cooling pumps. In the further course of the LOCA, the MWFA may block or penetrate the strainers. In addition to the impact of MWFA on the pressure drop across the strainers, corrosion products formed over time may also accumulate in the fiber cakes on the strainers, which can lead to a significant increase in the strainer pressure drop and result in cavitation in the ECCS. Therefore, it is essential to understand the transport characteristics of the insulation materials in order to determine the long-term operability of nuclear reactors, which undergo LOCA.
An experimental and theoretical study performed by the Helmholtz-Zentrum Dresden-Rossendorf and the Hochschule Zittau/Görlitz is investigating the phenomena that maybe observed in the containment vessel during a primary circuit coolant leak. The study entails the generation of fiber agglomerates, the determination of their transport properties in single and multi-effect experiments and the long-term effects that particles formed due to corrosion of metallic containment internals by the coolant medium have on the strainer pressure drop.
The focus of this presentation is on the numerical models that are used to predict the transport of MWFA by CFD simulations. A number of pseudo-continuous dispersed phases of spherical wetted agglomerates can represent the MWFA. The size, density, the relative viscosity of the fluid-fiber agglomerate mixture and the turbulent dispersion all affect how the fiber agglomerates are transported. In the cases described here, the size is kept constant while the density is modified. This definition affects both the terminal velocity and volume fraction of the dispersed phases. Application of such a model to sedimentation in a quiescent column and a horizontal flow are examined. The scenario also presents the suspension and horizontal transport of a single fiber agglomerate phase in a racetrack type channel.

Mineral wool insulation material applied to the primary cooling circuit of a nuclear reactor maybe damaged in the course of a loss of coolant accident (LOCA). The insulation material released by the leak may compromise the operation of the emergency core cooling system (ECCS), as it maybe transported together with the coolant in the form of mineral wool fiber agglomerates (MWFA) suspensions to the containment sump strainers, which are mounted at the inlet of the ECCS to keep any debris away from the emergency cooling pumps. In the further course of the LOCA, the MWFA may block or penetrate the strainers. In addition to the impact of MWFA on the pressure drop across the strainers, corrosion products formed over time may also accumulate in the fiber cakes on the strainers, which can lead to a significant increase in the strainer pressure drop and result in cavitation in the ECCS. Therefore, it is essential to understand the transport characteristics of the insulation materials in order to determine the long-term operability of nuclear reactors, which undergo LOCA.
An experimental and theoretical study performed by the Helmholtz-Zentrum Dresden-Rossendorf and the Hochschule Zittau/Görlitz1 is investigating the phenomena that maybe observed in the containment vessel during a primary circuit coolant leak. The study entails the generation of fiber agglomerates, the determination of their transport properties in single and multi-effect experiments and the long-term effects that particles formed due to corrosion of metallic containment internals by the coolant medium have on the strainer pressure drop.
The focus of this presentation is on the numerical models that are used to predict the transport of MWFA by CFD simulations. A number of pseudo-continuous dispersed phases of spherical wetted agglomerates can represent the MWFA. The size, density, the relative viscosity of the fluid-fiber agglomerate mixture and the turbulent dispersion all affect how the fiber agglomerates are transported. In the cases described here, the size is kept constant while the density is modified. This definition affects both the terminal velocity and volume fraction of the dispersed phases. Only one of the single effect experimental scenarios is described here that are used in validation of the numerical models. The scenario examines the suspension and horizontal transport of the fiber agglomerates in a racetrack type channel. The corresponding experiments will be described in an accompanying presentation (see abstract of Seeliger et al.).

Loss of coolant accidents (LOCA) in the primary cooling circuit of a nuclear reactor may result in damage to insulation materials that are located near to the leak. The insulation materials released may compromise the operation of the emergency core cooling system (ECCS). Insulation material in the form of mineral wool fibre agglomerates (MWFA) maybe transported to the containment sump strainers mounted at the inlet of the emergency cooling pumps, where the insulation fibres may block or penetrate the strainers. In addition to the impact of MWFA on the pressure drop across the strainers, corrosion products formed over time may also accumulate in the fibre cakes on the strainers, which can lead to a significant increase in the strainer pressure drop and result in cavitation in the ECCS. Thus, knowledge of transport characteristics of the damaged insulation materials in various scenarios is required to help plan for the long-term operability of nuclear reactors, which undergo LOCA.
An experimental and theoretical study performed by the Helmholtz-Zentrum Dresden-Rossendorf and the Hochschule Zittau/Görlitz1 is investigating the phenomena that maybe observed in the containment vessel during a LOCA. The study entails the generation of fibre agglomerates, the determination of their transport properties in single and multi-effect experiments and the long-term effect that corrosion of the containment internals by the coolant has on the strainer pressure drop.
The focus of this presentation is on the experiments performed that characterize the horizontal transport of MWFA, whereas the corresponding CFD simulations are described in an accompanying contribution (see abstract of Cartland Glover et al.). The experiments were performed a racetrack type channel that provided a near uniform horizontal flow. The channel is 0.1 wide by 1.2 m high with a straight length of 5 m and two bends of 0.5 m. The measurement techniques include particle imaging (both wide-angle and macro lens), concurrent particle image velocimetry, ultravelocimetry, laser detection sensors to sense the presence of absence of MWFA and pertinent measurements of the MWFA concentration and quiescent settling characteristics. The transport of the MWFA was observed at velocities of 0.1 and 0.25 m s-1 to verify numerical model behaviour in and just beyond expected velocities in the containment sump of a nuclear reactor.

Ziel/Aim:

The enzyme class of thiol-dependent cathepsins has been shown to be linked to the progression of cancer in multiple ways. Particularly crucial is their involvement in proteolytic pathways that are related to tumour invasion and metastasis (1).
The aim was the design of a fluorine-containing inhibitor of the azadipeptide nitrile chemotype (2) and the labelling with the radionuclide F-18 to evaluate the potential of this inhibitor class for functional tumour imaging by PET and to gain insight into the pharmacokinetic behaviour of these inhibitors.

Methodik/Methods:

The fluorine atom was connected by an ethylene bridge to the inhibitor core structure and the affinities of the resulting compound to its targets were determined in kinetic enzyme assays. Labelling with F-18 was achieved by fluoroethylation with different substituted [¹⁸F]2-fluoroethyl benzenesulfonates (3). The stability of the tracer against chemical and enzymatic degradation as well as its metabolic fate in rat blood was investigated and its biodistribution was studied in vivo by small animal PET.

Ergebnisse/Results:

The fluorine containing azadipeptide nitrile Gue2011 exhibits inhibition constant in the single-digit to subnanomolar range against the oncologically relevant cathepsins L, S, and B. Among the various F-18 fluoroethylating agents tested, [¹⁸F]2-fluoroethyl nosylate revealed as the most efficient one. This enabled the two-step radiosynthesis of [¹⁸F]Gue2011 in an average RCY (dc) of 24 % (n = 6). Metabolite analysis in rat blood showed the rapid conversion of the tracer into its glutathione conjugate as indicated by HPLC. Studies towards the pharmacological prevention of this conjugate formation are under current investigation.

Schlussfolgerungen/Conclusions:

With Gue2011 a highly potent fluorine-containing cathepsin inhibitor was found and its labelling with fluorine-18 could be successfully established. The compounds suitability as PET tracer for functional tumour imaging seems to be limited due to its inherent thiol reactivity. The radiolabelling of other cathepsin inhibitors is underway.

Literatur/References:

(1) Mohamed, M. M.; Sloane B. F. Nat. Rev. Cancer 2006, 6, 764-775
(2) Löser, R. et al. Angew. Chem. Int. Ed. 2008, 47, 4331-4334
(3) Musachio, J. L.; Shah, J.; Pike V. W. J. Label. Compd. Radiopharm. 2005, 48, 735-747

Ziel/Aim:

Bei der FDG-PET kann die Bildqualität bzg. des Signal/Rausch-Verhältnisses (SN-ratio) deutlich eingeschränkt sein (z. B. Adipositas, Atemgating). Der Einsatz üblicher glättender Filter (MAF: „Moving Average Filter“) verbessert das SN-ratio, reduziert aber die räumliche Auflösung, woraus verminderte Detailerkennbarkeit und Kontrastverlust v.a. bei Strukturen nahe der Auflösungsgrenze resultieren. Eine Alternative zu MAF sind lokal adaptive Filter, welche eine Rauschunterdrückung kombiniert mit Kantenerhaltung in den Bildern bewirken, aber bisher wenig verbreitet sind. Ziel: Einfluß der Bildbearbeitung mittels MAF und einem lokalen adaptiven Filter (LAF ) auf das abgegrenzte Tumorvolumen und den maximalen Standard Uptake Value (SUVmax) zu ermitteln.

Methodik/Methods:

10 Patienten mit nicht-kleinzelligem Bronchial-Karzinom und mind. einer Metastase, BMI 29,5 (23,9 – 40,4), mittl. injizierte Aktivität 384 MBq F18-FDG. Akquisition ab 60 min p.i., PET-Scanner ECAT EXACT HR+ (Siemens/ CTI). Iterative Rekonstruktion OSEM 6/16, Gauss 6mm. Vergleich von 5 Datensätzen: Original-Daten, MAF (3x3x3 Gaussfilter, FWHM = 8 mm) sowie LAF optimiert für 3 Rauschamplituden (NR20, NR40, NR60). Ermittlung von Tumorvolumen und SUVmax über 3D Regions Of Interest mittels ROVER (ABX, Radeberg). Ausgewertet wurde die Änderung des Volumens und des SUVmax in Abhängigkeit von der Filterung.

Ergebnisse/Results:

Es wurden insgesamt 29 Läsionen ausgewertet. 9 Läsionen zeigten eine Volumen < 3 ccm, 12 Läsionen zwischen >3 ccm und < 10c cm, 5 Läsionen <10 und >20 ccm, und 5 Läsionen > 20 ccm. Der SUVmax lag im Mittel bei 6,5 für Läsionen < 3 ccm, SUVmax 8,3 bei Läsionen zwischen >3 und < 10 ccm, SUVmax 12,1 bei Läsionen <10 und >20 ccm und SUVmax 19,4 bei Läsionen > 20 ccm. MAF führte zu einer Zunahme des ermittelten Volumens zwischen 2 und 18%, wobei die kleinen Läsionen eine relativ größere Volumenzunahme aufwiesen. Der SUVmax sank auf 85% bis 95% des Ausgangswertes, wobei kleine Läsionen eine deutlichere Reduktion des SUVmax zeigten. LAF führte zu keiner wesentlichen Volumenänderung im Vergleich zum Originaldatensatz. Der SUVmax lag bei einer noise reduction von 60% zwischen 92% und 98% des Ausgangswertes, bei NR20 und NR40 waren die Abweichunegn noch geringer.

Schlussfolgerungen/Conclusions:

Der Einsatz glättender Filter reduziert die effektive räumliche Auflösung der Bilddaten und ist problematisch im Hinblick auf die visuelle und quantitative Bewertung von kleinen Läsionen nahe der Auflösungsgrenze, selbst bei nur geringfügiger Glättung. Kantenerhaltende lokal adaptive Filter bieten eine vielversprechende Alternative und führen visuell wie quantitativ zu überlegenen Ergebnissen. Dies erscheint insbesondere von Bedeutung für Verlaufsuntersuchungen, bei denen möglicherweise die prozentuale Änderung des SUVmax nach Chemotherapie für eine weitere Therapiestratifizierung genutzt wird.

Ziel/Aim:

Hypoxia imaging using F-18-fluoromisonidazole (FMISO) positron emission tomography (PET) is of increasing interest in the field of radiation oncology. But for analysis of FMISO PET data a reliable and accurate delineation technique of hypoxic subvolumes is still needed. Due to the inability of threshold based segmentation approaches to deliver reliable results when applied to data sets with small, inhomogeneous or non spherical target volumes, more complex algorithms may be preferred (1). We propose an Ant-Colony-Optimization (ACO) approach for segmentation of FMISO PET data sets. This investigation was performed to validate the reproducibility of the algorithm processing patient data sets.

Methodik/Methods:

Our analysis included 28 patients from an ongoing prospective study on head and neck cancers. FMISO PET images were acquired 4 hours p.i. of ~266 MBq. Patients were investigated by FMISO PET before radiochemotherapy (RCT) and the resulting data sets were further processed by the proposed ACO approach. Virtual ants were operating autonomously in the PET volume searching for regions with signal intensity above average. When an ant is located in such a region, it emits pheromone, attracting more ants to go to the marked region. More ants emit more pheromone and in that way the pheromone field shows the target objects with higher contrast than the original data set. Afterwards the pheromone fields were segmented into positive and negative regions using a histogram based threshold algorithm. Each data set was processed for 3 times and the resulting delineations were compared pair wise using the Jaccard-Index (JI). Mean JI and standard deviation were calculated from the resulting three JI values for each data set.

Ergebnisse/Results:

The JI over all data sets was 0.81 (+- 0.1) indicating highly reproducible volume delineations. The mean segmented volume was 182 ml with a mean deviation of 10 %. In 19 patient data sets volumes outside the presumptive tumour volume were segmented as positive, especially in the cerebellar region. This finding is well comparable to the clinical experience and these volumes were also segmented with high reproducibility.

Schlussfolgerungen/Conclusions:

The results show that the ACO approach delivers reproducible volume delineations when applied to FMISO PET patient data sets. Further development of the proposed algorithm will face excluding positive regions outside the presumptive tumour volume and comparison of automatically generated delineations with manual segmentations by experienced physicians.

Literatur/References:

(1) Lee J.A. (2010) Segmentation of positron emission tomography images: Some recommendations for target delineation in radiation oncology.
Radiotherapy & Oncology, Vol. 96, Issue 3, pp 302-307

Ziel/Aim:

Aspiration of gastric contents is the second most common clinical event associated with the development of the adult respiratory distress syndrome (ARDS) and the mortality for ARDS resulting from acid aspiration ranges from 40-50%. Regions of aspiration induced injury matches regions of high pulmonary blood flow (PBF) in the early stage of acute lung injury, as recently shown by us. The aim of this project was to characterize the dynamics of regional PBF distribution in dependence on time after injury.

Methodik/Methods:

The protocol was approved by the Animal Study Committee of the Landesdirektion Dresden. In 11 desflurane anesthetized, spontaneously breathing male Wistar rats the lung injury was achieved by instillation of 0.1 HCl (0.4 ml/kg body weight) through a tracheostomy tube. The animals were scanned with a dedicated small animal CT scanner before and after injury. The pulmonary blood flow in the lungs was imaged by dedicated positron emission tomography (PET) using intravenously infused Ga-68-labeled DOTA-modified microspheres (diameter 20 µm) at 10 (6 animals) and 120 min (5 animals) after aspiration. CT- and PET-images were co-registered. Areas of injury, identified as new high density regions in lung CT-images after aspiration, were marked with a spherical mask and regions of interest (ROI) were derived using a threshold of 80% of maximum activity in the mask. Identical masks were used at the contralateral lung as reference. PBF in the injury ROI was calculated as activity fraction of the reference PBF region. The PBF in injury was compared with the reference side using the Wilcoxon matched-pairs signed rank test. The PBF-fraction at different time points was compared between the groups by unpaired t-test with Welch's correction.

Ergebnisse/Results:

CT images after aspiration showed areas of lung injury different in location and size within the two groups. Fraction of PBF in injured regions was higher at 10 min {1.34 (1.15-1.45) (median (interquartile range)} compared to 120 min (0.9 (0.85-1.06); P=0.0014) after aspiration. The intra-individual difference was determined by a high PBF in injured lung regions compared to the contralateral reference side at 10 min after injury (P = 0.03), whereas at 120 min after aspiration, injured regions have shown similar PBF compared to the contralateral reference side (P=0.81).

Schlussfolgerungen/Conclusions:

Regional PBF was increased 10 minutes after acid aspiration in regions of injury. This effect disappears within two hours after injury in anesthetized rats. This observed change in PBF after aspiration-induced acute lung injury seems to be important in early targeted treatment of acid aspiration.

Ziel/Aim:

Komplementäre L-Oligonukleotide (L-ON) stellen einen alternativen Ansatz zur Realisierung von Pretargeting-Technologien dar. Im Vergleich zu natürlichen D‑Oligonukleotiden besitzen L-Oligonukleotide eine sehr hohe metabolische Stabilität; allerdings werden sie sehr schnell aus der Blutbahn entfernt und in hohem Maße in den Nieren angereichert.Ziel des Forschungsvorhabens ist die gezielte Einflussnahme auf die Pharmakokinetik durch systematische PEGylierung einer L-ON-Leitstruktur. Schwerpunkte sind die Erhöhung der Bioverfügbarkeit durch Reduzierung der Blutclearance sowie die Verringerung der Nierenakkumulation.

Methodik/Methods:

Als Leitstruktur wurde das L-Oligonukleotid HO-C6H12-S-S-C6H12-5’GCG-GCT-GTG-CGG-TGC-GG3’ verwendet. Das 3’-Ende wurde mit PEG unterschiedlicher Größen (2, 5, 10, 20 kDa) derivatisiert. Nach Spaltung der Disulfidbindung und Funktionalisierung der PEG-L-ON-Konjugate mit maleinimidfunktionalisierten NOTA- bzw. DOTA-Chelatoren wurden die resultierenden Konstrukte mit Ga-68 bzw. Cu-64 markiert. Die Pharmakokinetik der Radiotracer wurde durch dynamische PET-Scans und simultane Organverteilungsstudien in Wistar-Ratten bestimmt.

Ergebnisse/Results:

Die Zunahme der PEG-Molmassen bewirkte eine stetige Reduzierung der Nierenaufnahme nach 60 min von 56,3 ± 4,1 %ID (Cu-64; 2 kDa PEG) und 52,4 ± 6,1 %ID (Ga-68; 2 kDa PEG) zu 6,5 ± 0,4 %ID (Cu-64; 20 kDa PEG) und 6,9 ± 0,6 % (Ga-68; 20 kDa PEG).Mit zunehmender PEG-Größe zeigte sich eine ansteigende Leberaufnahme nach 60 min p.i. von 4,8 ± 0,2 %ID (Cu-64; 2 kDa PEG) und 2,6 ± 0,4 %ID (Ga-68; 2 kDa PEG) zu 13,3 ± 2,1 %ID (Cu-64; 20 kDa PEG) und 10,7 ± 2,7 %ID (Ga-68; 20 kDa PEG). In den restlichen Organen, mit Ausnahme des Blutes, war die Radiotraceraufnahme nach 60 min p.i. sehr gering (<0,5 %ID/g bzw. <1 SUV). Aus den dynamischen PET-Untersuchungen wurden die Halbwertszeiten der einzelnen Radiotracer im Blutkreislauf bestimmt, diese betrugen 10,8 min (2 kDa PEG), 9,6 min (5 kDa PEG), 27,7 min (10 kDa PEG) und 39,4 min (20 kDa PEG).

Schlussfolgerungen/Conclusions:

Die Modifikation des pharmakokinetischen Profils der L-ON-Leitstruktur ist durch sukzessive PEGylierung möglich. Im optimalen Fall verringerte sich die Nierenanreicherung der PEG-L-ON nach 60 min auf ein Neuntel des Wertes der nicht-PEGylierten L-ON, bei gleichzeitiger Erhöhung der Verweilzeiten im Blut. Weiterhin bewirkte die PEGylierung eine Erhöhung der Leberaufnahme, während alle anderen Gewebe und Organe auf sehr niedrigem Radioaktivitätsniveau blieben. Durch PEGylierung von L-ON ist eine gezielte Beeinflussung der Pharmakokinetik möglich, jedoch ergeben sich entgegengesetzte Effekte bezüglich der Nieren- und Leberaufnahme. Die absoluten Anreicherungen in den genannten Organen müssen noch weiter reduziert werden, um die L-ON in Pretargeting-Technologien für Diagnostik und Therapie anwenden zu können.

Ziel/Aim:

The epidermal growth factor receptor (EGFR) is often overexpressed in human malignancies. This phenotype is associated with tumor aggressiveness, treatment resistance, and biological heterogeneity with potential to bypass the blockade of the EGFR signaling pathways. Cetuximab (C225) as a chimeric monoclonal antibody specifically targets the EGFR was modified for radio- and near infrared fluorescence (NIRF) imaging as well as for potential applications in radiotherapy using DTPA-, DOTA-, NOTA-modification, radio-labeling with Cu-64, Y-86, Y-90, Lu-177, and for modification with X-SIGHT Large Stokes Shift Dye (X-SIGHT 670 LSS Dye).

Methodik/Methods:

C225 was conjugated with bifunctional chelators based on SCN-Bz and -DTPA, -DOTA, -NOTA, and the C225-NOTA derivative was additionally modified with the X-SIGHT 670 Large Stokes Shift Dye, TFP Ester (XS670). The receptor binding and cell (A431 cells expressing high amounts of EGFR) uptake of Cu-64-NOTA-XS670-C225 was studied in vitro. The EGFR-affinity of the immune-conjugates was measured by a competitive radio-ligand binding assay. The conjugates were labeled with Cu-64, Y-86, Y-90, Lu-177 within 30 min with high radiolabeling yield and radiochemical purity. The biodistribution and –kinetics in vivo were studied by small animal PET or SPECT and ex vivo by autoradiography. Whole body cryo-sectioning of the animals into 40 micrometer sections permitted the direct comparison of the autoradiograms and NIRF images of the tissue sections.

Ergebnisse/Results:

C225 was conjugated with bifunctional chelators based on SCN-Bz and -DTPA, -DOTA, -NOTA, and the C225-NOTA derivative was additionally modified with the X-SIGHT 670 Large Stokes Shift Dye, TFP Ester (XS670). The receptor binding and cell (A431 cells expressing high amounts of EGFR) uptake of Cu-64-NOTA-XS670-C225 was studied in vitro. The EGFR-affinity of the immune-conjugates was measured by a competitive radio-ligand binding assay. The conjugates were labeled with Cu-64, Y-86, Y-90, Lu-177 within 30 min with high radiolabeling yield and radiochemical purity. The biodistribution and –kinetics in vivo were studied by small animal PET or SPECT and ex vivo by autoradiography. Whole body cryo-sectioning of the animals into 40 micrometer sections permitted the direct comparison of the autoradiograms and NIRF images of the tissue sections.

Schlussfolgerungen/Conclusions:

PET allows the quantitative kinetic characterization of biodistribution in small animals, which will be a prerequisite to estimate the dosimetry in animals. SPECT and autoradiography allowed the fine distribution imaging. The dual-labeling of antibodies is a promising tool for quantitative evaluation of the long time distribution in animals using NIRF of cryo-sections beyond the decay of the radionuclide used. Dual-labeled immune-conjugates represent a potential probe for translational application in tumor detection.

Ziel/Aim:

In einer Vielzahl menschlicher Tumore ist die Expression des Epidermal-Growth-Factor-Receptor (EGFR) nachweisbar und geht mit einer schlechteren Prognose onkologisch behandelter Patienten einher. Der EGFR wird durch seine natürlichen Liganden oder ligandenunabhängig durch Bestrahlung aktiviert. Zu den Substanzen, die den EGFR hemmen gehören monoklonale Antikörper (mAb) z. B. Cetuximab (C225). Die Markierung des C-225 mit dem Beta-Strahler Y-90 ermöglicht eine zielgerichtete Induktion von DNA-Schäden. Es sollte untersucht werden, welchen Einfluss der Zusatz von kaltem C225 auf den Uptake von Y-90-C225 in FaDu-Monolayer-Zellen hat.

Methodik/Methods:

FaDu-Zellen wurden in 6-Well-Mikrotiterplatten (MTP) ausgesät (1x105 und 3x105 Zellen pro well). Die Inkubation erfolgte mit Y-90-C225 über 24 h bei 37°C mit unterschiedlichen Dosen (0-6 Gy, Geant4 Monte Carlo Toolkits). Y-90-C225 wurde mit unmarkiertem C225 auf C225-Konzentrationen von 1 µg/ml und 5 µg/ml eingestellt und Proben ohne Zusatz von unmarkiertem C225 mitgeführt. Die Bestimmung des zellulär gebundenen Y-90-C225 (Uptake) erfolgte durch Messung der Radioaktivität des ungebunden Y-90-C225 sowie des gebundenen Y-90-C225 im Zelllysat an einem Gammacounter (CobraTM II).

Ergebnisse/Results:

Der Uptake von Y-90-C225 in FaDu-Zellen zeigte eine Abhängigkeit von der Zellzahl. Der absolute Uptake von Y-90-C225 ohne Zusatz von unmarkiertem C-225 stieg bei Dosissteigerung bzw. Konzentrationserhöhung des mAb nur marginal an, die relativen Werte (bezogen auf die eingesetzte Radioaktivität) zeigten bei 1 Gy den höchsten Uptake (1 Gy: 18,63%, 6 Gy: 3,6 %). Die Kompetition von Y-90-C225 und unmarkiertem C225 um die Bindungsstellen auf der Zellmembran konnte durch die Reduzierung des Y-90-C225-Uptakes mit zunehmendem Anteil von unmarkiertem C225 an der Gesamtantikörperkonzentration nachgewiesen werden.

Schlussfolgerungen/Conclusions:

Bei höheren Dosen bzw. Antikörperkonzentrationen wurde kein höherer Y-90-C225-Uptake erzielt, was auf eine Sättigung der Rezeptoren/Bindungsstellen hinweist. Die lineare Abnahme der zellulären Bindung des Y-90-C225 bei Erhöhung der Konzentration des unmarkierten C225 deutet auf die gleiche Affinität des markierten und unmarkierten Antikörpers an die EGFR-Bindungsstellen der FaDu-Zellen hin.Zur Verifizierung der Ergebnisse sind weitere Experimente geplant.

Ziel/Aim:

(-)-F18-Norchloro-fluoro-homoepibatidin ((-)-F18-NCFHEB) ist ein neuer und vielversprechender Radioligand für die Darstellung von alpha4beta2 nikotinischen Acetylcholinrezeptoren mit PET. Um das Strahlenrisikio durch diesen Tracer abzuschätzen, wurden die resultierenden Organdosen (OD) und die effektive Dosis (ED) im Rahmen einer Machbarkeitsstudie inkorporationsdosimetrisch ermittelt.

Methodik/Methods:

Die inkorporationsdosimetrische Untersuchung von (-)-F18-NCFHEB wurde an 3 Probanden (2 männlich, 1 weiblich; Alter: 59,6±3,9a; Gewicht: 74,3±3,1Kg) vorgenommen. Die Probanden unterzogen sich nach intravenöser Injektion von 353,7±10,2 MBq (-)-F18-NCFHEB einer sequentiellen PET-CT-Untersuchung bis zu 7h nach Injektion an einem SIEMENS Biograph16 PET-CT-System (9 Bettpositionen pro Frame, 1,5-6min/Bettposition, CT-Schwächungskorrektur, iterative Rekonstruktion). Bis zu 7h p.i. wurde sämtlicher Urin gesammelt und dessen Aktivitätskonzentration bestimmt. Alle den Tracer aufnehmenden Organe wurden CT-geführt mit dreidimensionalen Regionen (VOIs) markiert, und ihr Aktivitätsinhalt als Zeit-Aktivitäts-Verlauf dargestellt. Mit dem EXM-Modul von OLINDA [1] wurden Zeit-Aktivitäts-Kurven an diese Daten angepasst. Der Aktivitätsverlauf in der Blase wurde anhand der Urinabgaben bestimmt. ODs wurden unter Verwendung des 73,7kg-"adult male model" mit OLINDA bestimmt. Die ED wurde unter Verwendung der Gewebewichtungsfaktoren in der ICRP 103 von 2007 berechnet [2].

Ergebnisse/Results:

Die Harnblaseblase erhält die höchste OD (80,2±37,8µSv/MBq), gefolgt von der Leber (44,7±5,4µSv/MBq), den Nieren (38,6±5,1µSv/MBq), der Milz (38,4±11,6µSv/MBq), der Schilddrüse (32,8±11,9µSv/MBq) und den Lungen (31,1±5,3µSv/MBq). Die höchsten Beiträge zur ED leisten die Lunge (3,7±0,6µSv/MBq), die Harnblase (3,2±1,5µSv/MBq), der Magen (2,9±0,7µSv/MBq), das rote KM (2,3±0,2µSv/MBq), der absteigende Dickdarm (1,9±0,2µSv/MBq) und die Leber (1,8±0,2µSv/MBq). Die ED durch i.v. Applikation von (-)-F18-NCFHEB ergibt sich zu 22,9±0,7µSv/MBq.

Schlussfolgerungen/Conclusions:

Die effektive Dosis als Maß für das summarische Risiko durch i.v. Applikation von 300 MBq (-)-F18-NCFHEB) ergibt sich zu 6,8±0,2mSv. Dies liegt im Bereich der Strahlenexposition durch andere F18-markierte Radioliganden. Diese günstigen dosimetrischen Ergebnisse unterstützen die weitere Entwicklung von (-)-F18-NCFHEB) als klinischen Hirn-PET-Tracer.

Literatur/References:

[1] Stabin et. al.: OLINDA/EXM: The Second-Generation Personal Computer Software for Internal Dose Assessment in Nuclear Medicine; JNM 46/6, 2005
[2] International Commission on Radiological Protection. Recommendations of the International Commission on Radiological Protection. ICRP Publication 103, Pergamon Press, New York, 2007
Die Studie wird vom Bundesministerium für Bildung und Forschung gefördert (Nr. 01EZ0820)

Ziel/Aim:

Der Partialvolumeneffekt beeinträchtigt die Bestimmung der wahren Aktivitätskonzentration einer Zielstruktur (sowie hiervon abgeleiteter Größen, wie z. B. SUV-Werte). Bereits bei Strukturabmessungen, die noch deutlich größer als die rekonstruierte räumliche Auflösung der Bilddaten sind, tritt eine gravierende Unterschätzung der wahren Werte auf, insbesondere, wenn ROI-Mittelwerte betrachtet werden (beschränkte Signal-Recovery). Werden quantitative Parameter wie SUV-Werte zur Beurteilung des Therapieansprechens herangezogen, muss daher eine Recovery-Korrektur durchgeführt werden Ziel dieser Arbeit war es, eine routinefähige modellfreie Methode zur Recovery-Korrektur zu entwickeln und diese anhand von Phantommessungen zu validieren.

Methodik/Methods:

Die entwickelte Methode arbeitet in 2 Schritten. Schritt 1: Bestimmung des wahren Objektvolumens V unter Benutzung eines automatischen thresholdbasierten Verfahrens inklusive einer Berücksichtigung des lokalen Untergrundes (ROVER, ABX) und der entsprechenden Gesamtaktivität A innerhalb von V. Schitt 2: Bestimmung des infolge des Partialvolumeneffektes ausserhalb der Objektgrenze abgebildeten untergrundbereinigten(!) Aktivtätsanteils B. Der Recoverykoeffizient
ergibt sich hiermit zu R = A/(A+B). Es wurden Messungen mit einem Zylinderphantom (Durchmesser: 20 cm, Höhe: 18 cm) durchgeführt. Die im Zylinder befindlichen 6 Kugeleinsätze besitzen Volumina von 2,5 ml bis 27 ml. In 3 Phantommessungen mit einem ECAT EXACT HR+ (Siemens/CTI, Knoxville, Tennessee) wurden der Zylinder und die Kugeln mit unterschiedlichen Aktivitätsmengen (Fluor-18) befüllt, um das Signal-Untergrund-Verhältnis und damit den Bildkontrast zu variieren. Zum Vergleich wurden die Recovery-Koeffizienten aus der Faltung der Objektfunktion (homogene Kugel) mit der bekannten/gemessenen Point Spread Function der Bilddaten berechnet. Die berechneten Recovery-Koeffizienten wurden mit den aus den Bilddaten gewonnenen Koeffizienten verglichen.

Ergebnisse/Results:

Die in den Bilddaten mit dem beschriebenen Verfahren bestimmten Recovery-Koeffizienten stimmmen bei praktisch relevanten Target/Background Kontrastverhältnissen sehr gut mit den berechneten Koeffizienten überein (Abweichungen im Mittel 5%).

Schlussfolgerungen/Conclusions:

Die vorgestellte Methode liefert bei praktisch relevanten Kontrastverhältnissen und homogenem Untergrund gute Ergebnisse. Die genauen Gültigkeitsgrenzen des Verfahren (inhomogener Untergrund, geringer Kontrast usw.) müssen noch genauer untersucht werden.

Ziel/Aim:

Regional tissue perfusion is a fundamental physiological parameter controlling delivery of oxygen and nutrients to tissue. Arterial Spin Labeling (ASL) is a Magnetic Resonance Imaging (MRI) technique used for perfusion quantification. ASL has been shown to work reasonably well in human brain investigations. In other organs and especially in small animal imaging, however, ASL is not yet well established and validation against other methods is missing. The purpose of this work was to evaluate ASL in the brain of the rat by comparison with microspheres-derived regional perfusion using dedicated small animal PET and Optical Imaging (OI) systems.

Methodik/Methods:

Catheters were implanted through the right carotid artery in the left ventricle of the heart for administration of labeled microspheres (20μm) and in the left femoral artery for blood sampling. Microspheres were double-labeled with Cu-64 (or Ga-68) for PET (microPET P4, Siemens) and and X-sight 670 LSS for OI (Kodak FX). ASL measurements were performed in a 7T small animal MRI system (BioSpec 70/30, BRUKER) using a FAIR (Flow-sensitive Alternating Inversion Recovery) sequence with an adiabatic hyperbolic secant inversion pulse (length-bandwidth product: 80) and EPI (Echo Planar Imaging) acquisition. Global and selective T1 images were used for calculation of the perfusion values.

Ergebnisse/Results:

Perfusion in two brain slices was determined in three different ways (PET, MRI, OI). For the catheterized rat under anesthesia the whole brain perfusion values range from 0.2 to 1.19 ml/min/g for PET measurements and from 0.3 to 1.15 ml/min/g for OI calculations. In the normal rat brain (no catheter) under anesthesia perfusion values from FAIR-ASL ranged from 0.8 to 1.4 ml/min/g in both hemispheres (caudate putamen region). Catheter implantation created left/right differences between hemispheres of 10-30 %. The Pearson correlation factor varies between 0.88 and 0.9 for ASL vs. PET.

Schlussfolgerungen/Conclusions:

Overall the regional perfusion contrast is concordant between ASL and microspheres measurements. However, substantial quantitative deviations exist and are currently investigated. In order to become a useful routine applications in small animal imaging, ASL data acquisition and data evaluation needs to be further optimized. A thorough calibration via a quantitative comparison with radio- and fluorescent-labeled microspheres is mandatory. Altogether, perfusion quantification in the rat brain with ASL seems possible.

A numerical study is presented to examine the effects on countercurrent flow limitation (CCFL) of shape and size of hot leg models with rectangular cross-section. Using the CFD software FLUENT 6.3.26, numerical simulations were conducted for CCFL experiments in a 1/3 scale rectangular channel (HxW = 0.25x0.05 m2), and results were compared with CCFL data and simulation results in a 1/5 scale rectangular channel (HxW = 0.15x0.01 m²). Comparing CCFL characteristics in rectangular channels with those in circular channels, the hydraulic diameter was turned out to be a major factor of cross-section geometry influencing the CCFL characteristics in hot legs.

Engineered nanoparticles (NPs) are present in a wide variety of consumer products, occasionally in significant quantities. During aging, abrasion or disposal of such products, NPs-release is likely - accompanied with effects for the environment that have to be investigated in more detail. The aim of this study is to quantify the amount of NPs (TiO2 and Ag0) released from composite coatings due to weathering, aging or mechanical stress and to follow the NPs along their further fate in the environment.
Generally, particle tracking may provide information on the transport behavoir of the particles in aqueous media or on their interactions with biota. Since NPs are possibly released in tiny amounts and into very complex natural systems, we suggest the radiolabelling of NPs as a tool for their very sensitive detection throughout their life cycle including complex media such as aquifer sands, soil or cells.
Within this study, a novel radiolabelling technique for TiO2 (P 25, Evonik Degussa) and Ag0 (Sigma-Aldrich) NPs is under development. During this labelling process, significant changes of the chemical composition and properties of the particles are avoided to the greatest possible extend.
Stability of the NPs in different media has been studied and results contribute to first estimates concerning their transport behaviour in the aquatic environment. Batch tests including sediment materials were conducted to describe interactions of Ag0 and TiO2 NPs with natural matrices.
Interactions of engineered NPs and natural colloids have been studied as well. Results show that natural colloids have a strong influence on stability and transport of engineered NPs under environmental conditions.
Based on these data, radiolabelling of engineered NPs may open up the chance for sensitive tracking of particles not only in environmental media but also in other complex systems.

Thermal annealing of Fe/Pt multilayers (ML) is reported to reduce significantly the formation temperature of FePt hard magnetic thin films. The transformation mechanisms of [Fe 1.38 nm/Pt 2.24 nm]50 ML, prepared by magnetron sputtering, is investigated in the present communication by high temperature X-ray reflectivity using synchrotron radiation. Complete degradation of the ML periodic structure is observed at about 610 K. The variation with annealing temperature of the intensity of the first Bragg peak, the correlated vertical roughness, and the lateral correlation length of the ML show that the ML transform in two stages with a cross-over temperature of about 515 ± 15 K. This behavior cannot be simply explained by the change in the measured interdiffusion coefficient below and above the cross-over temperature, suggesting the formation of FePt nanograins along the interfaces.

Im Vortrag werden die Möglichkeiten zur Verbesserung des Schaltverhaltens von Leistungshalbleiter-Bauelementen mittels einer Ionenbestrahlung vorgestellt. Die grundlegenden physikalischen Effekte und gerätetechnischen Voraussetzungen werden diskutiert und die anwendungsrelevanten Vorteile am Bespiel von schnellen Schaltdioden aufgezeigt.

Since the discovery of the first organic superconductor, more than 30 years ago, these materials revealed many fascinating properties and allowed to study fundamental low-dimensional physics. Besides superconductivity, the organic metals show a wealth of different ground states such as antiferromagnetic, spin-Peierls, spin-density-wave, and charge-density-wave phases. These ground states are accessible by tuning the structure, counter anion, magnetic field, temperature, and pressure. The study of these fertile phase diagrams has led to new theoretical concepts; however, a solid understanding of some of these states still remains a challenge and especially the nature of the superconducting state is a controversially discussed issue since many years. Even the normal metallic phase of these electronically low-dimensional metals reveals unusual properties sometimes not in line with conventional Fermi-liquid theory. Here, a review on selected normal-state and superconducting properties of the layered quasi-two-dimensional organic superconductors will be given. Thereby, the focus will be laid on the superconducting properties of the charge-transfer salts based on bisethylenedithio-tetrathiafulvalene, BEDT-TTF or ET for short, the building block of most of the to-date known organic superconductors. Some basic features of the crystallographic structure, the highly anisotropic electronic properties, and of the superconductivity in the organics will be highlighted. In more detail the recently reported evidence for the existence of a Fulde Ferrell Larkin Ovchinnikov state for exactly aligned in-plane magnetic fields will be presented

The migration of tetravalent actinides in natural waters occurs predominantly as sorption complexes at the surface of colloidal particles like clay, but also by the formation of actinide oxyhydroxide colloids (MOn(OH)4-2n•mH2O where M = Th or U [1]). Colloid-facilitated migration of plutonium has also been documented in subsurface groundwater conditions [2]. In a recent study it was observed that the stability of U(IV) and Th(IV) oxyhydroxide colloids is dramatically enhanced by the presence of silica [3]. In this study we investigate the influence of silica on the formation and stability of U and Th colloids at near-neutral pH conditions, which might have important environmental implications due to the uniquitous nature of silica in aquifers and surface waters.
U and Th colloids with varying U/Si and Th/Si ratios were synthesized and characterized using a range of spectroscopic and microscopic techniques. TEM and XRD measurements indicated that the structure of thorium/silica colloids is highly amorphous, which is clearly different from the ordered actinide(IV) oxyhydroxide colloids which are stable at pH < 3 but agglomerate and precipitate at near neutral pH within minutes. Comparison of O 1s X-ray photoelectron spectra (XPS) of actinide(IV)-silica and actinide(IV)-oxyhydroxide colloids revealed that two types of oxygen bonds (oxo and hydroxo) occur in presence of silica, which may explain the high degree of structural disorder. Moreover, the presence of O-Si bonds at near-neutral pH values suggest that silica is able to stabilize such colloids through modification of the structure by replacing the An-O(H)-An bonds of the oxyhydroxide structure with An-O(H)-Si bonds and consequently influencing the surface charge. These observations are consistent with X-ray absorption spectroscopy (XAS) data which demonstrate higher An-Si interaction and lower An-An interaction with increasing silica content in these colloids.

[1] Rothe et al. (2002) Inorg. Chem. 41, 249-258.
[2] Kersting et al. (1999) Nature 397, 56-59.
[3] Dreissig et al. (2011) GCA 75, 352-367.

Das vom BMBF (Bundesministerium für Bildung und Forschung) geförderte Forschungsprojekt „Multifunktionelle Komplexbildner mit N, O, S-Donorfunktionen für d- und f-Elemente: Synthese, Komplexbildung, Struktur und Transportverhalten“ beschäftigt sich im Teilprojekt II mit der „Steuerung des Migrationsverhaltens von Radionukliden mit Hilfe makrozyklischer, multifunktionaler Chelatliganden“. Die Arbeitspakete Radionukliderzeugung, Radiomarkierung, Komplexbildungs- und Transportstudien in Geosystemen des Teilprojekts II werden in der Abteilung Reaktiver Transport des Instituts für Radiochemie untersucht.

Für die Sicherheitsbewertung von Schadstoffen in Untertagedeponien bestehen teilweise Defizite – insbesondere das Sorptions- und Komplexierungsverhalten von langlebigen radiotoxischen Schwermetallen unter naturnahen Bedingungen bedarf noch genauerer Aufklärung, was auch anhand fehlender Einträge in der RES3T-Datenbank zu sehen ist.[1] Das Sorptions- und Komplexierungsverhalten der Radionuklide wird sowohl durch das Milieu des Wirtsgesteins, als auch durch die Präsenz von anorganischen Komplexbildnern bestimmt.[2]

Für die Trennung von schwach-radioaktivem und hoch-radioaktivem Abfall werden hauptsächlich organische Komplexierungsverbindungen eingesetzt, die durch ihre teilweise hohe Elementselektivität mittels Extraktion oder Ionenaustausch diese Trennung ermöglichen. Für diese Trennung haben sich auch die Stoffgruppe der Calixarene als sehr nützlich erwiesen.[3] Die Calixarene werden nun so modifiziert, dass sie einerseits eine gute Wasserlöslichkeit und andererseits eine selektive Komplexierung von 85Sr bzw. 56Co aufweisen. Somit sollte eine gezielte Steuerung des Transports von Radionukliden mit Hilfe von Calixarenen ermöglicht werden.

Literatur:

[1] RES3T-Datenbank, URL: http://www.hzdr.de/db/res3t.login [13.04.2011] [2] M. Dozol, Pure & Appl. Chem. 1993, 65, 1081-1102. [3] J. F. Dozol, J. Incl. Phenom. Macrocycl. Chem. 2000, 38, 1-22.

We present results of a magneto-acoustic study of UCu_0.95Ge. This compound exhibits antiferromagnetic ordering at 48 K and shows a metamagnetic phase transition at 38 T for the magnetic field applied along the c direction, seen as a jump in themagnetization. The sound velocity and sound attenuation demonstrate pronounced anomalies in the vicinity of both magnetic phase transitions proving the important role of magnetoelastic interactions in the physics of this actinide compound.

We have performed magnetostriction and ultrasound measurements on the quasi-one-dimensional S ¼ 1=2 Ising-like antiferromagnet BaCo₂V₂O₈ in high magnetic fields of up to 51 T. The magnetostriction shows lattice shrinking along the c-axis, and we interpret it as the lattice distortion caused by exchange striction and Van-Vleck paramagnetism. It is clarified that the field dependence of sound velocity is correlated to the magnetostriction. We observed a pronounced softening in the sound velocity of the longitudinal-acoustic c₃₃ mode and found a novel phase transition.

The feasibility of embedding extrinsic superconducting nanolayers in commercial (100) silicon due to Ga precipitation is presented. To be far beyond the solid solubility limit of 0.1 at.% a high Ga fluence of 4x10¹⁶cm^-2 is introduced in silicon by the ion-implantation technique. This leads to 100 nm thick amorphous silicon layers with a Ga peak concentration of 16 at.%. Subsequent recrystallization and Ga precipitation is initiated via rapid thermal annealing (RTA) for 60 seconds at temperatures of 500 – 800°C. A 30 nm sputter deposited SiO₂ cover layer is used to protect the silicon surface during implantation and prevent Ga out-diffusion during annealing. It was shown that optimized annealing conditions (600 – 700°C) lead to superconducting layers with critical temperatures of 7 K and in plane critical fields up to 14 T [1]. Details of the layer microstructure investigations using of RBS/C and TEM as well as depth dependent XPS will be presented. The presented structural investigations reveal poly-crystalline silicon layers and show a strong Ga enrichment at the Si/SiO₂ interface. Even if no crystalline Ga clusters were detected it is shown that the superconductivity arises due to a high density of amorphous Ga-rich precipitates at the Si/SiO₂ interface. Since all involved processing steps are fully compatible with standard microelectronic technology and high criti-cal current densities of more than 2 kA/cm² are reached, the proposed material system may implicate a high potential for future microelectronic applications.
[1] Skrotzki R. et al., Appl. Phys. Lett. 97 (2010) 192505

After disposal in nuclear waste repositories the chemical and migration behavior of actinides depends on many factors. It is estimated that maximum temperatures in the near field of a repository could reach 300°C in dependence on the waste forms [1] and the host rock [2]. Thus, for the long-term safety assessment, knowledge of the interaction of actinides such as uranium with inorganic and organic ligands at elevated temperatures is required. The amount of organic matter in a repository can be separated in humic substances and in low molecular weight organic substances. A not negligible component of low molecular weight organic substances is the group of carboxylic acid. For example, citric acid is used in nuclear reprocessing [3] and acetic, lactic and formic acid were identified in rock extracts and pore water of Opalinus Clay [4]. Reliable experimental data on the complexation of U(VI) in solution at elevated temperatures are still needed.
Therefore, we studied the U(VI) complexation by lactic acid (pH 3) and citric acid (pH 0-10) in the temperature range from 7 to 65°C. Species distribution and complex formation constants were determined by means of UV-Vis and time-resolved laser-induced fluorescence spectroscopy. In the U(VI) lactate system, we identified the formation of 1:1- and 1:2-complexes. In the presence of citrate, we could characterize five U(VI) complexes in dependence on pH value. The complex formation between U(VI) and these both ligands was found to be endothermic and entropy-driven. The complex stability constants of the U(VI) complexes increase with increasing temperature. This could lead to an increased mobility of U(VI) at higher temperatures.

An output energy of 1.1 J of amplified nanosecond pulses was obtained by utilizing a diode-pumped Yb:YAG laser amplifier with the crystal cooled to 125 K. An all-mirror relay imaging was implemented to accomplish a low loss multi-pass scheme, where a three dimensional folding compensates the astigmatism of spherical mirrors at non-normal incidence. Without the need of diode-wavelength stabilization a for this type of amplifier record high total diode output to amplifier efficiency of 45 % was achieved.

We successfully demonstrated cw lasing of ytterbium-doped silica multicomponent glass bulk material. A slope efficiency of 43% and a tuning range from 1010-1080 nm have been achieved.

We present gain measurements and a time-resolved thermal lens analysis of a diode pumped, joule-class Yb:CaF2 disk laser. A thermal lens power of 0.05dpt at a single disk and small-signal gain of 5.2 in a two-disk amplifier were achieved at full pump power.

Thallium (Tl) is a typical toxic heavy metal, with higher toxicity than Hg, Cd, Pb. Anthropogenic sources such as coal combustion or mining/smelting activities generated high enrichments of Tl in some areas. For long-term risk assessments, the mobility in geochemical systems is a topic of major interest. Adsorption onto mineral surfaces can be considerably affected by dissolved humic acids (HAs), which are ubiquitous in natural waters. By using radioactive tracers, we were able to investigate co-adsorption of Tl and HAs at low concentration levels to be considered in real scenarios.
Two natural HAs were extracted from river sediments collected in a contaminated mining area in South China (regions of Guangzhou and Yunfu City). They were radiolabeled by an azo-coupling reaction with 14C-aniline. 204Tl(I) was employed as a radiotracer for Tl(I). The geological materials used in this study were goethite, pyrolusite and a natural sediment sample taken from Yunfu City.
For all these substrates, metal adsorption was found to be promoted with increasing pH since more binding sites are provided by deprotonation of surface hydroxyl groups. In contrast, adsorption of HAs was counteracted with increasing pH, which is explained by increasing electrostatic repulsion as a consequence of deprotonation. As expected, the extent of Tl(I)-HA complexation turned out to be very low, with a slight increase at higher pH.
Based on these data, a combined distribution model (Linear Additive Model) was tested for suitability in predicting the pH-dependent influence of HAs on Tl(I) adsorption. Our experimental results could not be reproduced in this way. In view of the fact that the approach worked well in other studies, criteria for its applicability need to be identified. Selectivities within the multicomponent system of humic material, regarding adsorption as well as complexation, are one possible reason for a failure of the model.

The methods of time of flight detection of fast neutrons are reviewed, with an emphasis on the planned NeuLAND detector at FAIR.

At the future Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany, uniquely intensive beams of radioactive ions will become available, enabling many experiments of astrophysical relevance. The Reactions with Relativistic Radioactive Beams (R3B) setup at FAIR will study reactions of such projectiles at energies up to 1 GeV/A. As part of R3B, the planned NeuLAND (New Large Area Neutron Detector) time-of-flight detector shall detect emitted neutrons with a time resolution of sigma < 100 ps and efficiency >90%. Two possible solutions are currently under study for NeuLAND: a pure scintillator concept and a design based on passive converters and multigap resistive plate chambers (MRPC's). The poster will outline the design work on the MRPC-based solution. The measured properties of a 200 cm * 50 cm large MRPC-based neutron detector prototype will be shown, the first device of such a size with thick passive converters inside the MRPC structure.

Due to the suppression by the Coulomb barrier, the cross sections of astrophysically relevant nuclear reactions are very low at the stellar energy. Therefore they can only be directly measured in a low-background environment. For more than a decade, the LUNA collaboration has pursued this approach with a 0.4\,MV accelerator in the Gran Sasso underground laboratory in Italy. It was highly successful in studying the nuclear physics of the Sun and of the Big Bang. However, the energy range of LUNA is not sufficient to address the nuclear reactions of stellar helium burning and the neutron source reactions for the astrophysical s-process. Therefore, in the NuPECC 2010 long range plan it is recommended to install one or more accelerators with higher energy underground. A comparison of the background at LUNA (1400\,m rock cover) and the Dresden Felsenkeller (45\,m) has shown that with an anti-muon veto the background counting rates in a $\gamma$-detector differ only by a factor of three. The feasibility of installing a 2-3\,MV accelerator for intense $\alpha$-beams in Felsenkeller will be discussed.

Five Ti-44 calibration sources supplied by Paul-Scherrer-Institute have been characterized concerning their activity distribution as well as the absolute activities. Now, calibration sources for nuclear astrophysics experiments with an uncertainty of +/-1.2% are available

Als Teil eines Langzeitsicherheitsnachweises für Endlager mit radioaktiven Abfällen sind auch Szenarien zu betrachten, bei denen es zu einer Mobilisierung von Radionukliden aus den Abfällen und damit zu deren Transport durch das Endlagersystem kommen kann. Eine wichtige Barriere im System eines Endlagers stellt neben dem Wirtsgestein auch das darüberliegende Deckgebirge dar. Der Transport durch die Geosphäre wird für viele Radionuklide durch Sorption an Oberflächen vorhandener Mineralphasen verlangsamt. In bisher verwendeten Transportprogrammen wird die Rückhaltung der Radionuklide über zeitlich und räumlich konstante Verteilungskoeffizienten (Kd Werte) beschrieben.
Im Rahmen des Vortrages wird das Verbundprojekt ESTRAL (Realitätsnahe Einbindung von Sorptionsprozessen in Transportprogramme für die Langzeitsicherheitsanalyse) (Kooperations-partner: HZDR Dresden-Rossendorf und GRS Braunschweig) vorgestellt. Ziel des Projektes ist es, eine neue Methodik zur Berücksichtigung der Sorption im bestehenden reaktiven Transportcode r³t (radionuclide, reaction, retardation, and transport, GRS) zu entwickeln und zu erproben. Dabei werden die bisher konditionellen Kd-Werte durch so genannte smart Kd-Werte ersetzt, welche auf Basis mechanistischer Modelle (Oberflächenkomplexierungsmodelle) als Funktion wichtiger Einflussgrößen Ei (z. B. pH, Ionenstärke, pCO2, Konzentration Ca2+ und Al3+) im geochemischen Speziationscode PHREEQC berechnet werden. Mit dieser Weiterentwicklung von r3t wird ein Instrumentarium zur Verfügung gestellt, mit dem der Radionuklidtransport unter sich verändernden geochemischen Bedingungen (z. B. infolge Klimaänderungen) realitätsnäher beschrieben werden kann. Eine solche Vorgehensweise wird exemplarisch für den Radionuklidtransport im Deckgebirge des möglichen Endlagers im Salzstock Gorleben entwickelt. Einzelne Einflussgrößen Ei sind bislang im Transportcode r³t nicht verfügbar. Hierzu werden geeignete Methoden zum Transport dieser Parameter sowie Gleichungen zur Beschreibung des pH-Wertes und der Ionenkonzentrationen als Funktion der verfügbaren Mineralphasen in r³t implementiert. Anschließend kann r³t für jeden Raum-Zeit-Punkt vorberechnete Verteilungs-koeffizienten aus einer mehrdimensionalen Matrix in Abhängigkeit von den jeweiligen geochemischen Bedingungen abrufen.
Anhand von Anwendungsrechnungen wird das weiterentwickelte Programm erprobt. Dafür werden zwei verschiedene Prozesse, die als Folge klimatischer Veränderungen auftreten können, untersucht: (1) Der Eintrag von Nordseewasser in das Deckgebirge für den Fall einer Meerestransgression während eines Klimaoptimums, und (2) Die Entwicklung des Deckgebirges in einer Warmzeit nach einer Kaltzeit mit lang andauerndem Permafrost. Bei beiden Prozessen werden sich die geochemischen Bedingungen erheblich verändern, was zu einer gravierenden Veränderung des Sorptionsverhaltens vieler Radionuklide führen wird.

Accidental release of radionuclides from mining activities, nuclear energy production, and radioactive waste storage sites requires research to predict the fate and mobility of these contaminants in the environment and more specific in organisms. To date, the interaction of actinides with biological systems is widely unkown, due to the lack of structural information on the molecular level. The aim of this presentation is to summarize recently explored coordination principles of tetravalent actinides with small carboxylic and aminocarboxylic ligands as well as the interaction with proteins.
Tetravalent actinides form with carboxylate ligands in aqueous solutions at low pH values usually monomeric complexes. They show at the other hand a strong tendency toward hydrolysis already at low pH. As the pH reaches the onset of An(IV) hydrolysis, olation and oxolation occur as competing reactions to the carboxylate complexation. We observed under these circumstances the formation of several well-defined polynuclear species. The carboxylic group acts in such systems as a terminating ligand and stabilizes nanosized polynuclear clusters in solution and in the solid state. It is important to note that this reaction prevents widely the formation of polynuclear hydrolysis species as well as the formation of An(IV) hydrous oxide colloids.

Aluminates, representing an essential component of clay minerals, play a decisive role in regulating the mobility of contaminants in rock and soil formations, in particular due to their tendency to form coatings on mineral surfaces [1].
In this work, U(VI) sorption on γ-Al₂O₃ is comparatively investigated using in situ vibrational and X-ray absorption spectroscopy. The focus was set to micromolar U(VI) concentrations and a variety of environmentally relevant sorption parameters in order to resolve discrepancies reported earlier [2-4].
Time-resolved (TR) IR spectroscopic sorption experiments at the alumina-water interface evidence the formation of three different species as a function of surface loading (c.f. Fig.): a monomeric carbonate complex, an oligomeric surface complex and a surface precipitate. These results are confirmed by IR experiments performed at different flow rates, pH values, ionic strengths, U(VI) concentrations, and in inert gas atmosphere. Results of EXAFS experiments of batch samples are consistent to these findings.
[1] Guillaumont, R. (1994) Radiochimica Acta 66-7, 231-242. [2] Catalano, J. G. et al. (2005) Geochim. Cosmochim. Acta 69, 3555-3572. [3] Moskaleva, L.V. et al. (2006) Langmuir 22, 2141-2145. [4] Sylwester, E. R. et al. (2000) Geochim. Cosmochim. Acta 64, 2431-2438.

We derive a new scaling law for the photon spectral density in nonlinear Thomson/Compton scattering, extending the findings of Heinzl, Seipt, and Kämpfer [Phys. Rev. A 81, 022125 (2010)]. This allows one to easily include the effects of general scattering geometries, e.g., side injection, and of a finite-size detector on the photon spectrum. The scaling law is employed to study substructures emerging in the nonlinear Thomson/Compton spectra due to temporally shaped laser pulses scattering off relativistic electrons. We determine optimum scattering geometries for an experimental verification of these substructures.

The dosimetric characterization of laser-accelerated electrons applied for the worldwide first systematic radiobiological in vitro cell irradiations will be presented. The laser-accelerated electron beam at the JeTi laser system has been optimized, monitored and controlled in terms of dose homogeneity, stability and absolute dose delivery. A combination of different dosimetric components were used to provide both an online beam as well as dose monitoring and a precise absolute dosimetry. In detail, the electron beam was controlled and monitored by means of an ionization chamber and an in-house produced Faraday Cup for a defined delivery of the prescribed dose. Moreover, the precise absolute dose delivered to each cell sample was determined by an radiochromic EBT film positioned in front of the cell sample. Furthermore, the energy spectrum of the laser-accelerated electron beam was determined. As presented in a previous work of the authors, also for laser-accelerated protons a precise dosimetric characterization was performed that enabled initial radiobiological cell irradiation experiments with laser- accelerated protons. Therefore, a precise dosimetric characterization, optimization and control of laseraccelerated and therefore ultra-short pulsed, intense particle beams for both electrons and protons is possible, allowing radiobiological experiments and meeting all necessary requirements like homogeneity, stability and precise dose delivery. In order to fulfil the much higher dosimetric requirements for clinical application, several improvements concerning, i.e., particle energy and spectral shaping as well as patient safety are necessary.

Excitons in semiconductor exhibit a hydrogenic energy spectrum, scaled down into the THz range. By pumping the 1s-2p intra-excitonic transition in GaAs/AlGaAs quantum wells with the Dresden free-electron laser, we induce an AC Stark effect, namely the famous Autler-Townes splitting reflecting exciton states dressed by THz photons [1]. The spectrum is probed via band-gap absorption. Under similar conditions, we also observe resonantly enhanced THz sideband generation by mixing the THz and band gap radiation [2].
[1] M. Wagner et al., Phys. Rev. Lett. 105, 167401 (2010)
[2] M. Wagner et al., Appl. Phys. Lett. 94, 241105 (2009)

THz spectroscopy of semiconductors at high electric and magnetic fields

High Resolution Rutherford Backscattering Spectrometry (HR-RBS) with a depth resolution of about 0.3 nm near the surface was used to analyse the interface between ultrathin high-k ZrO₂-layers and the substrate. In order to improve the quality of the analysis, a method was developed that takes local thickness variations, obtained by atomic force microscopy (AFM), into account during simulation of the HR-RBS spectra. The aim was to study atomic layer deposition (ALD) growth processes on Si(100) covered with native silicon oxide (SiO₂) or with TiN. In the first case the interface is sharp, except for a small intermediate ZrSiO₄-layer, and no diffusion of Zr-atoms in SiO₂ could be detected. A quite different behaviour could be derived from high resolution spectra for the growth of ZrO₂ on TiN. In addition, measurements of the surface topography of the TiN-layer revealed non-negligible surface roughness. Diffusion of Zr into polycrystalline TiN was demonstrated for the first time after correction for surface roughness. This observation indicates that already during the first ALD reaction cycle a small proportion of the deposited Zr-atoms diffuses – probably along grain boundaries – into the TiN-layer up to a depth of 3 nm.

The paper describes the simulation of adiabatic gas-liquid flow based on the Euler/Eulerian approach. An adequate characterisation of the momentum exchange between the phases is necessary. The basic experiment investigating the momentum exchange is the vertical upward flow in a pipe. This report describes the main CFD approaches for momentum exchange and the comparison to experimental results for several test conditions. For large gas injection rates, a bubble size distribution including bubble coalescence and fragmentation has to be considered. The paper describes the concept of the inhomogeneous MUSIG model, developed by ANSYS/CFX and HZDR which is implemented in CFX and a comparable concept of a population balance model implemented in NEPTUNE_CFD (CEA, EDF, IRSN and AREVA). Measurements performed in HZDR are used for model validation. Crucial for the quality of the described models are the base approaches for bubble coalescence and fragmentation. Among other influences these phenomena depend on the liquid turbulence. Therefore special attention was devoted on CFD simulation of bubbly turbulent flow based on different model concepts. Concepts based on Reynolds averaged turbulence models are described. In PSI Large Eddy based studies were performed and compared to DEDALE experiments. The work was performed within the NURESIM and the NURISP projects in the frame of sixth and the seventh European Framework Program.

Im Vortrag wird der aktuelle Bearbeitungsstand zur Modellierung von Rückhaltevorrichtungen im Notkühlkreislauf von Kernreaktoren berichtet. Die Modellierung unterteilt sich in ein Basismodell zur Berechnung der im Verlauf des Prozesses akkumulierten Isoliermaterialmasse und des daraus resultierenden Druckverlusts über der kompressiblen Packung, sowie in ein erweitertes Modell, das den weiteren Anstieg des Druckverlusts durch Einlagerung von Korrosionspartikeln infolge der Tiefenfiltrationswirkung der Packung in der Spätphase des Kühlmittelverluststörfalls beschreibt. Im Vortrag werden experimentelle und theoretische Arbeiten zur Parametrierung der Modellgleichungen sowie Beispielrechnungen vorgestellt.

No abstract availabe

Early work on the iron-arsenide compounds supported the view, that a reduced dimensionality might be a necessary prerequisite for high–T_c superconductivity. Later, however, it was found that the zero-temperature upper critical magnetic field, H_c2(0), for the 122 iron pnictides is in fact rather isotropic. Here, we report measurements of the temperature dependence of the electrical resistivity, rho(T), in Ba_0.5K_0.32Fe₂As₂ and Ba_0.68K_0.32Fe₂As₂ single crystals in zero magnetic field and for Ba_0.68K_0.32Fe₂As₂ as well in static and pulsed magnetic fields up to 60 T. We find that the resistivity of both compounds in zero field is well described by an exponential term due to inter-sheet umklapp electron-phonon scattering between light electrons around the M point to heavy hole sheets at the Г point in reciprocal space. From our data, we construct an H–T phase diagram for the inter-plane (H || c) and in-plane (H || ab) directions for Ba_0.68K_0.32Fe₂As₂. Contrary to published data for underdoped 122 FeAs compounds, we find that H_c2(T) is in fact anisotropic in optimally doped samples down to low temperatures. The anisotropy parameter, γ = H^ab _c2/H^c _c2, is about 2.2 at T_c. For both field orientations we find a concave curvature of the H_c2 lines with decreasing anisotropy and saturation towards lower temperature. Taking into account Pauli spin paramagnetism we perfectly can describe H_c2(T) and its anisotropy.

We present results of a magneto-acoustic study on a UCu_0.95Ge single crystal. This compound exhibits antiferromagnetic ordering at 48 K and shows a first-order metamagnetic phase transition at 38 T to a spin-polarized state, i.e., when the magnetic field is applied along the c direction a sharp jump in the magnetization appears. The sound velocity and sound attenuation demonstrate pronounced anomalies in the vicinity of both magnetic phase transitions proving the important role of magneto-elastic interactions in the physics of this actinide compound. Above T_N, the acoustic characteristics show some unusual frequency-dependent features which presumably can be related to the dynamics of Cu vacancies in UCu_0.95Ge. Our results are discussed in frame of a phenomenological model, which describes qualitatively the main experimental observations.

The heavy-fermion (HF) metals are very susceptible to chemical substitution. In these compounds the Kondo coupling between a lattice of local moments and the conduction band creates quasiparticle excitations with large effective masses and the dopants disrupt the coherent Kondo coupling. We study the effect of Yb doping on the Pauli-limited, HF superconductor, CeCoIn₅ via de Haas-van Alphen (dHvA) measurements. Yb acts as a non-magnetic divalent substitution for Ce, equivalent to hole doping on the rare-earth site. Our main goal consists in the systematic investigation of the dHvA oscillations on Ce_1−xYb_xCoIn₅ in order to elucidate the evolution of the Fermi surface as a function of Yb. The dHvA data were obtained on high-quality single crystals with different concentrations of Yb atoms. The experiment was performed in a top-loading dilution refrigerator by use of a capacitive torque cantilever technique at temperatures down to 20 mK in magnetic fields up to 18 T.

We demonstrate the feasibility of embedding superconducting Ga nanolayers in commercial (100) oriented silicon wafers and discuss the possibility of potential device applications [1]. Ion implantation and rapid thermal annealing, known as versatile tools of microelectronic technology, have been used for inserting and distributing a gallium dose of up to 4 × 10¹⁶ cm². As proven by structural analysis, a 10 nm thin layer of amorphous Ga-rich precipitates forms during annealing at 600 - 700°C. These structures exhibit a superconducting transition at 7 K. Extended resistivity and magnetization measurements reveal in-plane critical fields around 14 T and critical current densities exceeding 2 kA/cm². In summary, we proceed with an optimistic outlook concerning the implementation of prospective microstructuring. After all, this would be the next step towards the development of novel semiconductor-based superconducting devices.

We determined thermodynamic (specific heat), magnetic (magnetization, magnetostriction and susceptibility) and transport (electrical resistivity) properties of the 4d-electron superconductor Rh₁₇S₁₅ (T_c = 5.3 K). The upper critical field is 19.2 T at T = 0.07 K. We investigated both a polycrystal and a single crystal. Specific heat gives (B = 0) = 107 mJ/molK², m_eff = 35 m₀, and a superconducting energy gap Δ₀ = 0.94 meV. The magnetic properties are dominated by flux-line pinning; resistivity likely reveals an amplification of electron-phonon coupling by weak disorder. Additionally, band-structure calculations are presented and interpreted in the context of our own experiments and other recently published results.We interpret our findings in order to find the origin of the strong electronic correlations in Rh₁₇S₁₅ both in the superconducting and in the normal-conducting state.

Magnetic excitations in copper pyrimidine dinitrate, a spin-1/2 antiferromagnetic chain with alternating g-tensor and Dzyaloshinskii-Moriya interaction, that exhibits a field-induced spin gap, are probed by means of pulsed-field electron spin resonance spectroscopy. In particular, we report on a minimum of the gap in the vicinity of the saturation field B_sat = 48.5 T associated with a transition from the sine-Gordon region (with soliton-breather elementary excitations) to a fully spin-polarized state (with magnon excitations). This interpretation is fully confirmed by quantitative the agreement with DMRG calculations for a spin-1/2 Heisenberg chain with staggered transverse field

Inhalt der Arbeiten des HZDR im Rahmen des BMWi-Forschungsvorhabens 150 1363 ist u. A. die Untersuchung des Einflusses von Korrosionsprodukten auf das Differenzdruckverhalten von Mineralwolleablagerungen an den Sumpfansaugsieben der Notkühlsysteme von Leichtwasserreaktoren bei Kühlmittelverluststörfällen.
Zur Aufklärung der Korrosionsprozesse und deren Auswirkungen auf die Verstopfung der Sumpfsiebe wurden zahlreiche Experimente in der Korrosionsversuchsanlage „KorrVA“ unter Nutzung von feuerverzinkten Stahlproben durchgeführt. Die Ergebnisse der Langzeit-Korrosionsexperimente lassen auf einen mehrstufigen Korrosionsmechanismus schließen. Zunächst erfolgt eine Auflösung der Zinkschicht in der Borsäure-Lösung. Die dabei entstehenden Zink-Ionen gehen in Lösung und tragen somit nicht signifikant zur Erhöhung des Druckverlustes an den Sumpfsieben bei. Während der zweiten Stufe erfolgt die Auflösung des Basismaterials, welches in weiterer Folge zu unlöslichen Korrosionspartikeln (Rost) reagiert. Diese lagern sich an den mit Isoliermaterial-Fasern belegten Sumpfsieben ab und führen so zu einem weiteren Differenzdruckaufbau. Als Haupteinflussfaktoren des Gesamtprozesses wurden die Aufprallkraft des Leckstrahls auf die Materialoberfläche, die Kühlwasserchemie sowie das Verhältnis der Korrosions-Oberfläche zum Kühlmittel-Volumen und das Verhältnis von Zink-Oberflächen im Leckstrahl zu unter dem Wasserspiegel liegenden verzinkten Oberflächen identifiziert.

We present an experimental and theoretical study of the quasi-onedimensional S = 1/2 Heisenberg magnet linarite PbCuSO₄(OH)₂, with competing ferromagnetic nearest-neighbor and antiferromagnetic nextnearest- neighbor exchange interactions. It includes magnetization and NMR studies as well as theoretical simulations for the determination of the leading exchange couplings, which are about an order of magnitude higher as determined previously [1]. Furthermore, a manifold of field-induced phases are probed, from which we draw a preliminary phase diagram. Notably, spin-lattice relaxation investigations indicate that linarite might undergo a magnetic quadrupolar spin liquid phase transition as recently predicted for such materials.

Ho₂Ti₂O₇ and Dy₂Ti₂O₇ belong to the family of rare-earth titanates with pyrochlore structure which have attracted much interest in recent years because of their spin-ice ground state and unusual magnetic excitations. Ultrasound experiments have been carried out on Ho₂Ti₂O₇ and Dy₂Ti₂O₇ at low temperatures down to 0.3 K and applied magnetic fields of up to 17.5 T. The temperature as well as field dependences of the relative change of the sound velocity demonstrate some pronounced anomalies below 2 K for the acoustic modes c₁₁ and c_L. In addition we have performed magnetization measurements of these two compounds. The observed anomalies and features in the sound velocity and magnetization provide additional information about the spin-lattice interactions in these spin-ice compounds. The role of the lattice degrees of freedom in connection with the emergent quasiparticles (magnetic monopoles) is discussed.

In recent years, many synthetic strategies have emerged with regard to the crystal engineering of functional magnetic materials. The group of J.L. Manson et al. were able to grow single crystals of a quasi-2D antiferromagnet Cu(pyz)₂(HF₂)]SbF₆ and a defective polymorphic pendant [Cu₂(pyz)₄F(HF)(HF₂)₂ where 50% of the HF₂ ^- links are broken, leading to two crystallographically unique Cu²⁺ sites. The chemical composition remains unchanged, the structural configuration indicates a minor Jahn-Teller distortion. We studied the two branches of this compound by means of magnetization and specific heat measurements, in order to get a better understanding of the importance of H-F hydrogen bonds for establishing long-range magnetic ordering in polymeric quantum magnets.

Conceptual model of the new methodology
In previous safety assessments the Kd concept with temporally constant values was applied to describe the radionuclide retardation in the far field of a repository.
Here, the existing transport program r3t [1] used for large model areas and very long time scales has been improved by a new methodology. Implementing the smart Kd concept based on surface complexation allows to consider varying realistic geochemical conditions.
The methodology is based on a description of the sorption of radionuclides as a function of selected, important environmental parameters Ei such as pH, pCO2, ionic strength, concentration of the cations Ca2+ and Al3+ and presence of mineral phases. Exemplarily for a potential repository site in Germany, the Gorleben site has been selected as application case for a proof-of-concept.
Most of the individual parameters Ei are not available in r³t so far. Thus the transport of these influence factors as well as equations describing pH and concentrations of ions as a function of accessible mineral phases had to be implemented. Then the reactive transport model r³t can call for each time-space point pre-calculated Kd values for selected sediments. They are stored in a multidimensional matrix depending on the respective geochemical conditions. Figure 1 shows the frequency distribution of the pre-calculated Kd-values for Am3+ and U6+ and their classification.

Figure 1: Frequency distribution of the pre-calculated Kd values for Am3+ and U6+.

[1] Fein (2004) Report GRS-192.

We investigate nonlinear optics related to the intraexcitonic 1s-2p heavy-hole transition in GaAs/AlGaAs quantum wells. Tuning intense terahertz (THz) light around this resonance we report (i) efficient second order sideband generation and (ii) first clear evidence of the Autler-Townes effect.

Microstructural Evaluation of Ti-6Al-4V alloy after Plasma Immersion Ion Implantation (PIII)

Surface Modification of Ni-Ti SMA by Nitrogen Plasma Immersion Ion Implantation – Tribology Preliminary Results

Structure and Tribological Properties of the Aged Inconel 718 Superalloy by Plasma Immersion Ion Implantation

A series of 1,5-diaryl-substituted tetrazole derivatives was synthesized via conversion of readily available diaryl amides into corresponding imidoylchlorides followed by reaction with sodium azide. All compounds were evaluated by cyclooxygenase (COX) assays in vitro to determine COX-1 and COX-2 inhibitory potency and selectivity. Tetrazoles 3a–e showed IC₅₀ values ranging from 0.42 to 8.1 mM for COX-1 and 2.0 to 200 lM for COX-2. Most potent compound 3c (IC₅₀ (COX-2) = 2.0 lM) was further used in molecular modeling docking studies.

In order to get the correct feedback on the core reactivity, analyses of postulated reactivity initiated accidents in nuclear reactors require the coupled solution of the neutron transport equation, the equations of heat conduction in the fuel and the heat and momentum transport in the coolant. The paper gives an overview on the coupling of the neutron kinetics code DYN3D with the general purpose fluid dynamics code ANSYS CFX which was carried out to improve the thermal hydraulic part of reactor dynamics simulations. Two steady state simulations of Convoi and VVER type reactors demonstrate that the coupled code system allows for analyses with more plausible results of coupled thermal hydraulics - neutron kinetics problems because three-dimensional coolant flow and heat transport can now be simulated.

At the depth of 70 m (tunnel chainage 771) of the nuclear waste repository research tunnel ONKALO (Finland), which will be part of the nuclear waste repository in the future, massive biofilms are growing next to a fracture zone in a granitic rock environment. They were described as a pink and solid slime, consisting of Pseudomonas anguilliseptica, Arthrobacter bergeri, Hydrogenophaga sp., Methylobacter tundripaludum, Rhodoferrax ferrireducens, and Haliscomenobacter hydrossis. The samples were removed from the tunnel wall together with the fracture water for uranium sorption experiments in a flow cell. A uranium concentration of 4×10-5 M was adjusted in the fracture water by adding UO2(ClO4)2. The water was pumped through the flow cell in a closed circuit for 42 hours. Microsensor measurements of the redox potential, pH and oxygen were performed in the several millimeters thick biofilms before and after the addition of uranium in order to record the effect of uranium. The obtained data showed significant changes of redox potential, pH and oxygen. The redox potential decreased after the addition of uranium during the experiment from 70  2 mV to -164 mV  2 mV with an increase of the pH from 5.4  0.1 to 7.3  0.1 at the same time, indicating reducing conditions in the microenvironment of the biofilm. The decrease in the oxygen concentration showed that the bacteria in the top region of the biofilms, i.e. the metabolically most active biofilms zone, battled the toxic effects of aqueous uranium with an increased respiratory activity, which resulted in oxygen depleted zones. Redox processes may have been triggered, leading to a removal of uranium from the aqueous phase. Analysis, which were performed before and after the sorption experiment, clearly showed, that 63 % of the added uranium was immobilized.

The retardation of uranium in the biofilm was determined by Energy-filtered Transmission Electron Microscopy (EF-TEM) and Electron Energy Loss Spectroscopy (EELS). Elongated particles of high electron density were observed in the cytoplasm of some rod shaped gram negative bacteria, which were often found associated with large rod shaped bacteria. Analysis of the elongated particles by EELS provided spectroscopic evidence for the presence of uranium immobilization, showing unequivocally uranium ionization intensity peaks of O4,5- and N6,7-edges. Distribution analysis of uranium, phosphorus and calcium clearly showed, that a solid uranium mineral has formed intracellular, which indicates the presence of a solid U-phosphate mineral similar to Autunite (Ca[UO2]2[PO4]2•10-12H2O).

Acknowledgments:

The European Atomic Energy Community Seventh Framework Programme [FP7/2007-2013] under grant agreement n° 212287, Collaborative Project ReCosy is thanked for funding.

The code DYN3D, devoloped at the Helmholtzzentrum Dresden-Rossendorf, is extended for application of block-type High Temperature Reactors.
It involves a 3D heat conduction model to deal with higher-(than one)-dimensional effects of heat transfer and heat conduction in a block-type HTR. The heat conduction model is coupled with the existing thermal-hydraulic channel model of DYN3D. Fully-coupled (hexagonal) neutron kinetics and thermal hydraulics calculations are performed. It is shown that the model is appropriate to simulate both stationary states and short-time transients (sudden change of reactivity, sudden increase of the inlet coolant temperature) in a block-type HTR.

Excited states of ⁸⁰Br have been investigated via the ⁷⁶Ge(¹¹B, 3n) and ⁷⁶Ge(⁷Li, 3n) reactions and a new I = 1 band has been identified which resides 400 keV above the yrast band. Based on the comparison between the experimental results and the triaxial particle rotor model calculations, a chiral character of the two bands within the pi g9/2 X nu g9/2 configuration is proposed, which provides the first evidence for chirality in the A 80 region.

The g factors of the first excited 2+ states in the A=112,114,116,122,124 Sn isotopes have been measured with high accuracy using the transient field technique in combination with Coulomb excitation in inverse kinematics. The experimental results are discussed in a qualitative way on the basis of empirical single particle g factors of the relevant proton and neutron orbitals and compared to a number of different theoretical calculations. The results are found to be best described by shell-model calculations in an extended configuration space. Clear evidence for the contribution of neutron pair excitations from the 1d3/2 to the 0h11/2 orbital to the wave function of the 2+ state in 122,124Sn has been obtained.

We study field- and current-induced domain-wall motion in permalloy nanowires comprising a square-shaped magnetically softened region. Implantation of chromium ions is used to induce pinning sites via a local reduction of the saturation magnetization. Micromagnetic simulations, magnetic transmission soft X-ray microscopy, and electrical measurements are employed to char- acterize the pinning potential which significantly differs for transverse and vortex walls. Reliable domain-wall depinning from a so-called magnetic soft spot by single current pulses is observed. This demonstrates the suitability of these pinning sites for applications.

The environmental fate of plutonium, the major transuranium actinide in nuclear waste, is largely impacted by its sorption onto and redox reactions with iron oxide, carbonate or sulfide minerals that form as corrosion products of steel in the "near field" and occur widely in sediments. To obtain information on oxidation state and local structure of Pu in the presence of Fe(II) bearing minerals, electrolytically prepared Pu(V) or Pu(III) (242Pu, 1-3·10-5 M) were, under anoxic conditions, reacted with magnetite (FeIIFeIII2O4) (pH 6-8.5), chukanovite (Fe2(CO3)(OH)2) (pH 8.5) and mackinawite (FeS) (pH 6-8.5). Pu-LIII-edge X-ray absorption spectra (XAS) were collected after 40 d and 8 months of reaction.
In all 14 samples, more than 98 % of Pu was associated with the solid phase and its redox speciation thus accessible by XAS. With magnetite, only the sample prepared at the highest pH and highest Pu loading contained Pu(IV)O2 while in all others Pu was solely present as a tridentate Pu(III) surface complex [1]. The three chukanovite samples all contained both Pu(III) (15 to 40 %) and PuO2. With mackinawite at pH 6 only Pu(III) was present, while all samples prepared at pH7 and higher contained mostly PuO2 and up to approx. 10 % Pu(III).
Through comparison of the different types of minerals (oxide, carbonate, sulfide), reaction pH and Pu/mineral ratios, it becomes apparent that the type of surface complexation (e.g. inner-sphere on magnetite vs. outer-sphere on mackinawite) and total mineral surface area are key parameters in controlling concentrations of dissolved Pu and in determining whether a PuO2 solid phase precipitates. While PuO2 provides an upper limit for concentrations of dissolved Pu, the available mineral surface area and sorption complex stability control what percentage of Pu is present in surface complexes. Under reducing conditions as established through the Fe(II) bearing minerals used here, this mineral surface associated Pu was found to be trivalent. Surface complexed Pu(III) and PuO2 can be thought of being in equilibrium with each other via two processes: a sorption reaction between dissolved and surface complexed Pu(III) and a heterogeneous redox reaction between dissolved Pu(III) and solid phase Pu(IV)O2. It remains to be investigated if and through what mechanisms the Pu solid phase speciation (sorbed Pu(III) vs. solid phase PuO2) might impact the migration behavior of Pu and how, for risk assessment purposes, Pu(III) surface complexes with iron minerals can be implemented into geochemical models.

Es ist kein Abstract vorhanden.

As a common method to separate intrinsic and extrinsic spin relaxation processes in a ferromagnet, their frequency dependence is employed. We show, that this current approach may be insufficient for a large class of ferromagnetic systems, since the extrinsic spin relaxation can exhibit non-monotonous, periodic frequency dependence, as demonstrated by a good agreement of ferromagnetic resonance experiment and phenomenologic theory.

Quantum fluctuations in low-dimensional magnets give rise to a variety of exotic strongly correlated states, making those systems an extremely attractive ground for testing various theoretical concepts. In this presentation I will focus on high-frequency and high-field Electron Spin Resonance (ESR) studies of two low-dimensional quantum magnets: copper pyrimidine dinitrate (Cu-PM), a spin-1/2 antiferromagnetic chain system with alternating g-tensor and Dzyaloshinskii-Moriya interactions, and the spin-ladder system (C₅H₁₂N)₂CuBr₄ (known as BPCB). In Cu-PM, the observation of a minimum of the spin gap in the vicinity of the saturation field, H_sat = 48.5 T, is associated with a transition from the sine-Gordon region (with soliton-breather elementary excitations) to a spin-polarized magnon state. This interpretation is fully confirmed by the quantitative agreement over the entire field range of the experimental data with the DMRG calculations for spin-1/2 Heisenberg chain with a staggered transverse field. In BPCB, the zero-field gap in the excitation spectrum, Δ = 16.5 K, is observed directly. In addition, our studies provide straightforward evidence of a pronounced anisotropy in this compound (~ 5% of the rung interaction), which is in contrast to an isotropic spin-ladder model, employed for this system previously. It is argued that such an anisotropy in BPCB is determined by the substantial spin-orbit coupling, which appears to be very important for describing magnetic properties of BPCB. The talk will give also a brief introduction into the recent development of the high-field ESR program at the Dresden High Magnetic Field Laboratory.