Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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

The imposition of an RMF on a solidifying metal column causes problems like the occurrence of typical segregation pattern or a deflection of the upper free surface leading to surface defects or the entrainment of gas. The RMF application provides a permanent radial inward flow along the solidification front. Such flow is responsible for the transport of solute to the axis of the ingot resulting in typical freckle segregation pattern in form of vertical channels filled with alloy of eutectic composition. In this paper we present a new innovative method of electromagnetic stirring using a modulated RMF which offers a considerable potential for a well-aimed modification of casting properties Solidification experiments as well as numerical simulations were carried out considering the directional solidification of Pb Sn alloys from a water cooled copper chill. A modulated rotating magnetic field (RMF) was applied for melt agitation. Thermocouples were used to measure the temperature field during solidification. The velocity field in the liquid phase was determined by means of Ultrasound Doppler velocimetry (UDV). Our numerical model is based on the classical mixture formulation. The comparison between numerical simulations and solidification experiments delivered a good agreement. Our results demonstrate the modulation magnetic field enables an effective control of the flow field and the structure of the solidified samples. Modifications of the grain structure and macrosegregation effects are discussed with respect to the details of the flow field.

High-spin states in neutron-rich Mo-106 were investigated by detecting the prompt gamma-rays in the spontaneous fission of Cf-252 with Gammasphere. Several new bands are observed. Two sets of Delta I = 1 bands in Mo-106 are found to have all the characteristics of a new class of chiral vibrational doublets. Tilted axis cranking calculations support the chiral assignment and indicate that the chirality is generated by neutron h(11/2) particle and mixed d(5/2), g(7/2) hole coupled to the short and long axis, repectively.

High-spin states in the neutron-rich nuclei Yb-172,Yb-173 have been populated in a Er-170(Li-7,(p,d,t)chi n) incomplete-fusion reaction and the emitted gamma-radiation was detected with the GASP array. The signature partners of the 7/2(+)[633] rotational band of the odd-N Yb-173 isotope have been newly established and were observed up to spin values of (45/2(+)) and (43/2(+)), respectively. The ground-state band of the even-even nucleus Yb-172 has been observed up to a spin value of (22(+)). No band crossings were found in these bands. To explain this observation; it is proposed that the static pair field is absent; considering that the neutron odd-even mass differences reach for these nuclei very small values and that the band crossing is absent in cranked shell modell calculations without pairing. The results indicate, however, that strong dynamic correlations are still present.

During Loss-of-Coolant-Accidents (LOCA) in nuclear reactors insulation materials of pipes and pressure vessels can be released inside of drywells and containments under the impingment forces of steam and water jets. A portion of dislodged fragments of thermal insulation materials would transport to the screens and strainers arranged forwards of Emergency-Core-Cooling-System (ECCS) pumps. Within the „ German competence network East for nuclear engineering“ at the University of Applied Sciences Zittau/Görlitz (FH) and the Research Centre Rossendorf (FZR) generic investigations has been carried out for the development and improvement of CFD-models for the analytic simulation of insulation-water-two phase flow based on an experimental generated data basis. This paper presents the description of the test facility „Ring line-II“ and results of separate effect experiments regarding the behaviour of water-insulation fragments flow at a horizontal perforated plate used as strainer in BWR plants with the insulation material MD2-1999.

The evolution of the nanostructure of magnetron sputtered Au films has been experimentally studied. At a synchrotron-radiation beam line, during growth and subsequent annealing, in-situ X-ray diffraction has been carried out to follow the texture, the grain size, the microstrain and lattice-plane distances. With Bragg–Brentano geometry, only (111) grains, having a (111) plane parallel to the film surface, have been observed, while, with glancing incidence and exit X-ray diffraction, (111)* grains, having one of their (111) planes perpendicular to the film surface, have also been observed. Both during growth and subsequent annealing, the (111) texture changed, and some (111)* grains recrystallized and/or the orientation of the grains changed. The microstrain decreased drastically during the first few minutes of growth (300 A) while, simultaneously, the size of the coherently diffracting domains increased. Subsequently, the microstrain became constant, and the rate of increase of the size of coherently diffracting domains leveled off. Initially, during the first few minutes of annealing, a large decrease in the microstrain was observed simultaneously with a dramatic rise of the size of the coherently diffracting domains. After this initial annealing period, as during film growth, the microstrain became constant, and the rate of increase of the size of coherently diffracting domains leveled off.
The activation energy for the initial growth of the coherent diffracting domains was found to be Q=(0.25 +/- 0.03) eV, and the activation energy for normal grain growth was found to be Q=(0.99 +/- 0.04) eV.
Finally, the thin-film stress was followed during growth and subsequent annealing. A tensile contribution to the stress was observed during island coalescence.

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Tetravalent uranium is the typical form of uranium in reducing natural waters such as deep groundwaters or waters of the deeper zones of abandoned uranium mines. The colloidal behaviour of uranium(IV) was investigated. Coulometric titrations of strongly acidic U(IV) solutions in HClO4/NaClO4 medium (I = 0.2 M) were carried out in order to find the pH of first colloid formation. Laser-induced breakdown detection (LIBD) was applied for the detection of traces of uranium colloids as the pH was increased. The pH values at the onset of colloid formation were used for thermodynamic calculations aimed at determining the solubility products of crystalline and amorphous uranium dioxide (cf. [1]). Furthermore, the UO2·xH2O(am) colloids were investigated for their colloidal stability. Zeta potentials of ≥ 30 mV were found for pH values of less than 4. The point of zero charge was at pH ~ 6.9. Colloidal suspensions of 10-3 M UO2·xH2O(am) at a pH value of 2.5 proved to be stable over > 1.5 years. The interaction of the forming UO2·xH2O(am) colloids with other colloid-forming species was tested. Therefore, coulometric titrations of U(IV) solutions in the presence of (a) dissolved Al(III) and (b) dissolved silicate were carried out. The presence of Al(III) does not significantly influence the formation of the UO2·xH2O(am) colloids, and the presence of U(IV) does not significantly influence the behaviour of Al(III). There is more interaction of the U(IV) with silicate. Silicate, on the one hand, does not significantly influence the pH value of first UO2·xH2O(am) colloid formation, i.e. it does not significantly influence UO2·xH2O(am) solubility. However, the presence of U(IV) significantly influences the precipitation behaviour of the silicate (formation of U(IV)-Si “pseudocolloids” due to co-precipitation). The nature of the interaction between the silicate and the U(IV) is not yet known. Adsorption of the silicate onto the UO2·xH2O(am) colloids and/or formation of a coffinite (USiO4) precursor come into question. Measurements by extended X-ray absorption fine structure (EXAFS) spectroscopy with synchrotron radiation to elucidate the local structure around the U(IV) atoms in the pseudocolloids are underway. Reference: [1] Opel K., Weiß S., Hübener S., Zänker H., Bernhard G. Radiochim. Acta, 95 (2007) 143-149.

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Software zum Datenaustausch zwischen dem Steuerungssystem der Strahlenquelle ELBE und den Datenaufnahmesystemen der Experimentatoren

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The symmetries of the rotating mean field and their consequences for rotational bands are discussed. Chirality of rotating triaxial nuclei differs from the chirality of molecules and mass-less particles, because the roles of space inversion and time reversal are exchanged. The experimental consequences of chirality and mass regions where it is expected are discussed. Rotational bands of the predicted shapes with tetrahedral symmetry are ΔI=2 sequences with alternating parity. Breaking of the isospin rotational symmetry by the isovector pair field leads to isorotational bands. The low spin spectra of N=Z nuclei can be explained combining mean-field calculations that take only isovector pairing into account with the concept of isorotational bands. The possible appearance of an isoscalar pair field at high spin would manifest as a pair-rotational band consisting of even-spin states in the even-even and odd-spin states in odd-odd N=Z nuclei.

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Introduction:

The coupling of phosphonic acid esters with carbonyl compounds, also referred to as the Horner-Wadsworth-Emmons reaction, represents a powerful carbonyl olefination reaction to form C-C double bonds, exhibiting E-configuration exclusively.
This work describes the application of the Horner-Wadsworth-Emmons reaction as novel labeling technique in 18F-chemistry. Various 18F-labeled E-configured stilbenes could be synthesized through the coupling of benzylic phosphonic acid esters with readily available 4-[18F]fluorobenzaldehyde 1 as labeling precursor (Fig. 1).

Experimental:

The carbonyl-olefination reaction was performed via a “multi-step/one-pot” reaction by the coupling of benzylic phosphonic acid esters (3,5-bis-methoxymethoxybenzyl)-phosphonic acid diethyl ester 2a, (4-methoxymethoxybenzyl)-phosphonic acid diethyl ester 3a and (4-dimethyl-aminobenzyl)phosphonic acid diethyl ester 4a) with 4-[18F]fluorobenzaldehyde to give the corresponding 18F-labeled stilbenes [18F]2b, [18F]3b and [18F]4b exclusively as the expected E-isomers after deprotection. The radiochemical yields ranged from 9 to 22% (based upon [18F]fluoride, including HPLC purification). The specific activity reached up to 90 GBq/μmol.

Results and Discussion:

The reaction can be applied for the synthesis of polyphenolic compounds and aromatic amines bearing an E-configured stilbene backbone as pharmaceutically interesting compounds. Several E-configured stilbene-based polyphenols are known to be potential anticancer compounds. In the case of amine group-containing stilbene compound [18F]4b, structural comparable stilbenes have been reported as potential ligands to bind to Aβ-plaques found in the brain of patients with the neurodegenerative Alzheimer's disease. Preliminary radiopharmacological studies including small animal PET of compound [18F]4b in normal rats showed promising brain uptake. Results on the radiopharmacological characterization of compound [18F]4b will be presented.

Conclusion:

The described method opens a convenient access to a large number of 18F-labeled compounds bearing an E-configured stilbene backbone.

Acknowledgement: The authors wish to thank S. Preusche for radioisotope production and T. Krauss for technical assistance.

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Introduction:

Radiolabeled RGD-peptides have been studied for in vivo targeting of integrin receptors which are over-expressed in carcinomas [1]. The high pharmacological influence of the radiometal complex and limitations of various labelling concepts are reasons for exploring new approaches. The so-called “4+1” mixed-ligand chelate system, [Tc(NS₃)(CN-R)], is an interesting alternative due to high labelling efficiency and in vivo stability [2]. Here we present the application of this concept to the labelling of the peptide c(RGDyK).

Experimental:

The figure shows the labelled peptides, corroborated upon coinjection with the corresponding rhenium compounds. The RGD-peptide, serving as monodentate ligand, was functionalized with 4-(isocyanomethyl)benzoic acid (L1) and 4-isocyanobutanoic acid (L2). ^99mTc labelling was performed starting from ^99mTc-EDTA followed by ligand exchange reaction with a mixture of the appropriate isocyanide-modified peptide and a tetradentate ligand (NS₃R). The resulting series of ^99mTc peptide conjugates [^99mTc(NS₃R)(L-c(RGDyK))] with R = R1, R2, R3 and L = L1, L2 was evaluated in biodistribution studies using tumour-bearing mice.

Results and Discussion:

The radiochemical yield was about 60 % after labelling 0.05-0.1 mg of isocyanide-modified peptide. Purification by HPLC resulted in radiochemical purity > 95 %. The stability of the 99mTc conjugates in PBS was higher than 90 % after 24 h. Distribution ratios (logD, octanol/PBS, pH 7.4) covered the range from -0.59 ± 0.14 for [⁹⁹mTc(NS₃R1)(L1-c(RGDyK))] to -3.3 ± 0.2 for [^99mTc(NS₃R3)(L2-c(RGDyK))]. The compounds exhibited only low tumour uptake and a fast hepatobiliary elimination. Substitution of the tripodal chelator bearing R1 or R2 by the carboxyl group-bearing ligand NS₃R3 resulted in a predominant urinary excretion.

Conclusion:

The "4+1" mixed-ligand approach enables the ^99mTc-labelling of c(RGDyK). The chelate unit dominates the biodistribution profile which could be influenced by varying the tripodal chelator.

[1] Haubner, R., Wester, H.-J. Curr. Pharm. Design 10 (2004) 1439-1455.
[2] Seifert, S. et al., Bioconjugate Chem. 15 (2004) 856-863.

IAEA, CSIC, FMP-CHLCC, Lab. de vacunas recombinantes, Fac. de Medicina, Uruguay for financial support.

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We construct a family of equations of state within a quasiparticle model by relating pressure, energy density, baryon density and susceptibilities adjusted to first-principles lattice QCD calculations. The relation between pressure and energy density from lattice QCD is surprisingly insensitive to details of the simulations. Effects from different lattice actions, quark masses and lattice spacings used in the simulations show up mostly in the quark-hadron phase transition region which we bridge over by a set of interpolations to a hadron resonance gas equation of state. Within our optimized quasiparticle model we then examine the equation of state along isentropic expansion trajectories at small net baryon densities, as relevant for experiments and hydrodynamic simulations at RHIC and LHC energies. We illustrate its impact on azimuthal flow anisotropies and transverse momentum spectra of various hadron species.

Introduction:

The interaction of S100/calgranulins, a multigenic family of Ca2+-modulated proteins, with receptors for advanced glycation endproducts, e.g., RAGE and AGERs, is hypothesized to be of high relevance in the pathogenesis of various diseases including cardiovascular diseases, inflammatory processes, and cancerogenesis. However, data concerning the role of circulating S100/calgranulins in these pathologies are scarce. Furthermore, it is currently not known whether RAGE or AGERs are universal S100/calgranulin receptors in vivo. One reason for this is the shortage of suitable radiolabeling methods for direct assessment of metabolic pathways of S100/calgranulins in vivo. We report a novel radiotracer approach using radiolabeling of recombinant human S100A1 with fluorine-18 (18F) and the application of 18F-labeled S100A1 (18F-S100A1) in dynamic small animal positron emission tomography (PET) studies in rats.

Experimental:

Human S100A1 was cloned in the bacterial expression vector pGEX-6P-1 and expressed in E. coli strain BL21. Radiolabeling of purified S100A1 was performed by conjugation with N-succinimidyl-4-(18F)fluorobenzoate ([18F]SFB). 18F-S100A1 was used for investigations of stability in vitro and in vivo. The metabolic fate of 18F-S100A1 in rats in vivo was delineated by dynamic PET studies using a dedicated small animal PET system.

Results and Discussion:

Radiolabeling of S100A1 with [18F]SFB at pH 7.4 resulted in 18F-S100A1 specifically labeled at the N-terminal glycine residue with radiochemical yields of 2-6% (decay-corrected) and effective specific activities of 0.5-1 GBq/µmol, respectively. In vitro experiments, and biodistribution and metabolite studies in rats in vivo revealed high stability for the 18F-S100A1. The organ-specific in vivo distribution and kinetics of 18F-S100A1 correlated well with the anatomical localization of receptors for advanced glycation endproducts, e.g., in blood vessels and lungs. In the presence of glycated human low density lipoprotein (glycLDL), a well characterized RAGE ligand, mean plasma residence time of 18F-S100A1 increased by 40% from 29.6±1.5 min to 41.3±2.1 min and lung associated retention of 18F-S100A1 decreased by 57% first indicating circulating S100A1 to be a specific ligand for receptors for advanced glycation endproducts in rats in vivo. Data were compared to former small animal PET studies using the 18F-labeled glycLDL.

Conclusion:

Radiolabeling of S100/calgranulins with 18F and the use of small animal PET provides novel probes to delineate functional expression of RAGE and AGERs under normal and pathophysiological conditions in rodent models of disease in vivo.

Acknowledgement: This study was supported in part by the DFG (grant no. Pi 304/1-1).

Introduction:

The incorporation of 18F into peptides and proteins usually takes advantage of prosthetic groups, also referred to as bifunctional labeling agents. This approach comprises 18F incorporation into a small organic molecule capable of being linked to peptides and proteins under mild conditions. This work deals with a comparative discussion on the synthesis and application of N-[6-(4-[18F]fluorobenzylidene)aminooxyhexyl]-maleimide ([18F]FBAM) and 4-[18F]fluorobenzaldehyde-O-(2-{2-[2-(pyrol-2,5-dion-1-yl)ethoxy]ethoxy}ethyl)oxim ([18F]FBOM) as novel prosthetic groups for the mild and selective conjugation to thiol group-containing biomacromolecules (Fig. 1).

Experimental:

The aminooxy-functionalized labeling precursor for radiosynthesis of [18F]FBAM was prepared in a convenient three-step synthesis sequence in a total yield of 59%. The corresponding labeling precursor for the radiosynthesis of [18F]FBOM succeeded in a four-step reaction sequence in 14% total yield. Formation of the prosthetic groups [18F]FBAM and [18F]FBOM was achieved through condensation reaction with [18F]fluorobenzaldehyde to form the desired oximes in radiochemical yields of 20-30% ([18F]FBAM) and of 14-19% ([18F]FBOM), respectively.

Results and Discussion:

The syntheses were carried out in a remotely-controlled radiofluorination module allowing the convenient and reliable performance of the radiolabeling reactions. The radiochemical purity exceeded 95% and the specific activity ranged from 50 to 80 GBq/µmol. The total synthesis time was 70 to 80 min. The lipophilicity was determined to be logP=2.71 for [18F]FBAM and logP=0.84 for [18F]FBOM. The usefulness of [18F]FBAM and [18F]FBOM as thiol-reactive group prosthetic group was demonstrated by the reaction with glutathion, low density lipoproteins (LDL) and modified neurotensin derivatives. Reaction of [18F]FBAM and [18F]FBOM with glutathione showed that the use of as little as 1 µg/ml glutathione after 30 min provides excellent radiochemical yields of 95% of the desired coupled products. Labeling of LDL showed superior results with [18F]FBAM, whereas comparable results for both prosthetic groups were obtained for the labeling of modified neurotensin derivatives.

Conclusion:

The ease of production and the excellent performance in radiolabeling reactions make compounds [18F]FBAM and [18F]FBOM very promising prosthetic groups for the mild and selective conjugation to thiol group-containing biomacromolecules.

Introduction:

The matrix protein tenascin-c (TN-C) represents an interesting target for molecular imaging in oncology due to it´s high abundance in a variety of human tumors such as lung, breast and brain tumors [1]. First radiolabeled anti-TN-C antibodies could successfully proof the concept of tumor-TN-C targeting [2]. However, a persistently high blood level hampers their use for targeted imaging. Aptamers, a class of rapidly clearing high affinity oligonucleotides, have been introduced successfully to molecular imaging by the application of the Tc-99m labeled TN-C Targeting Aptamer-1 (TTA-1) [3]. Here we report on the radiolabeling, binding affinity and biodistribution of this novel targeting aptamer labeled with metal PET isotopes.

Experimental:

Labeling with Ga(III), Y(III), and In(III) was performed in a one pot reaction after conjugation of a DOTA-type chelating moiety to TTA-1-MAG2. In-111 was included in the study as a surrogate for Ga and Y in long term stability and affinity tests. The labeling was carried out in the presence of the aptamer-chelator conjugate and the respective radiometal in acetate buffer. Degradation was investigated in human plasma employing PAGE. Affinity for human TN-C was determined in a nitrous cellulose filter binding assay. Athymic mice, bearing the human U251 tumor cell line, were injected with the radiolabeled TTA-1 derivatives.

Results and Discussion:

Addition of the radiometal salts yielded the respective labeled aptamer conjugates in high yields (60 – 80 %). Ultrafiltration of the products led to > 95 % of pure material as determined by PAGE and HPLC methods. The biological stability in human plasma ranged from 68 % (In-111) to 95 % (Y-86) of intact material after 6 hr. Binding affinity for human TN-C revealed a KD of 1 nM (In-111). A maximum tumor uptake of 2.0 % ID/g (Ga-68), 1 hr p.i. and T/Non Tumor ratios of 5.1 (T/blood), 0.2 (T/kidney), 0.7 (T/liver) 1 hr p.i. proved to be adequate to image the U251 tumor xenograft in mice. Tumor visualization was possible for both Ga-68 and Y-86 labeled TTA-1.

Conclusion:

The introduction of a DOTA-type chelating moiety could be successfully used to radiolabel the aptamer probe with In, Ga and Y. The stability against nuclease degradation along with a significant tumor accumulation, high T/ blood levels and the imaging capabilities in PET-scans make these compounds promising candidates for further evaluation as multi-tumor imaging agents.

Acknowledgement:

1. R. Chiquet-Ehrismann, Cell 47, 131 (1986)
2. P. Riva, Cancer 73, 1076 (1994)
3. B.J. Hicke, J. Nuc. Med. 47, 668-678 (2006).

Introduction:

Neurotensin receptors are expressed with high incidence in several human tumour entities. Thus, radiolabeled neurotensin derivatives might be used for tumour targeting. However, its application is limited by insufficient metabolic stability. Metabolic stability might be improved by the synthesis of multimeric peptides.

Experimental:

Three methods for 18F-labeling of dimeric and tetrameric neurotensin(8-13) derivatives were evaluated with respect to the labeling yield and the required peptide amounts.

Results and Discussion:

Labeling using N-succinimidyl-4-[18F]fluorobenzoate ([18F]SFB) gave low radiochemical yield for the dimeric peptides. Coupling of the tetramer with [18F]SFB was not successful. Furthermore, labeling of aminooxy-functionalized neurotensin(8-13) derivatives using 4-[18F]fluorobenzaldehyde ([18F]FBA) was investigated. High yields of up to 96% were obtained for the dimer whilst coupling of the tetramer only gave low yields of up to 10%.
In contrast to these findings, labelling of sulfhydryl-functionalized neurotensin(8-13) derivatives using the maleinimide 4-[18F]fluorobenzaldehyde O-[6-(2,5-dioxo-2,5-dihydro-pyrrol-1-yl)-hexyl]-oxime ([18F]FBAM) resulted in high radiochemical yields for both, the dimer and the tetramer, being 94% and 40%, respectively. Therefore, [18F]FBAM seems to be the most suitable 18F-labeling agent for multimeric neurotensin(8-13) derivatives. The synthesized 18F-labeled multimeric neurotensin derivatives are depicted in Fig. 1.

Conclusion:

In summary, 18F-radiolabeling of dimeric and tetrameric NT(8-13) derivates was investigated. Suitable results were obtained by labeling of the sulfhydryl-functionalized peptides using [18F]FBAM. Using [18F]SFB or [18F]FBA as the labeling agent gave only low radiochemical yields. Furthermore, labeling of the dimer gave better radiochemical yields than labeling of the tetramer – independent from the labeling method which was used. Therefore, the nature of the peptide exhibits a strong influence on the coupling reaction.

Introduction:

Click chemistry is a generic term for a set of reactions, which make use of several selective and modular building blocks to create heteroatom C-X-C links. The copper(I)-catalyzed 1,2,3-triazole formation from azides and terminal acetylenes according to a 1,3-dipolar [3+2]cycloaddition is a particularly powerful linking reaction due to its high degree of specificity and the biocompatibility of the reactants. Recently the first application of click chemistry in 18F chemistry has been reported [1]. Herein we report an alternative click chemistry strategy suitable for 18F labeling reactions.

Experimental:

The labeling strategy was exemplified by the synthesis of 18F-labeled neuropeptide neurotensin NT(8-13) [18F]3 (Fig. 1).
Results and Discussion: 4-[18F]Fluoro-N-(prop-2-ynyl)benzamide [18F]2 as novel terminal alkyne building block was prepared in 90% radiochemical yield by the reaction of readily available N-succinimidyl-4-[18F]fluorobenzoate [18F]SFB with propargyl amine. Purification of [18F]2 was performed by solid phase extraction. Coupling of 18F-labeled terminal alkyne with azide-functionalized NT(8-13) 1 gave the corresponding 18F-labeled NT(8-13) derivative [18F]3 in 66% yield as determined by radio-HPLC. Receptor binding of NT(8-13) derivative [19F]3 was investigated using the human colon adenocarcinoma cell line HT-29. The peptides inhibited the binding of [3H]-NT, showing a typical sigmoid curve. The in vitro binding affinity of NT(8-13) derivative [19F]3 was determined to be 66 nM.

Conclusion:

In summary, the use of [18F]fluoro-N-(prop-2-ynyl)benzamide [18F]2 as suitable click chemistry building block allows the convenient radiolabeling of 18F-labeled small molecular weight compounds as well as peptides as exemplified for the synthesis of 18F-labeled NT(8-13) [18F]3. This offers the application of click chemistry to the synthesis of a broad array of novel 18F-labeled compounds.
References:
[1] J. Marik, J.L. Sutcliffe, Tetrahedron Lett. 47 (2006) 6681-6684.

Within the framework of reactor safety research of the German Federal Ministry of Economics, the scientific-technical cooperation of selected topics with Russian institutions is supported. Some of these topics are performed by the Institute of Safety Research of the Forschungszentrum Dresden-Rossendorf (FZD) together with Russian institutes. The paper summarizes selected results for the following topics:

• Contribution to the validation of the Russian thermalhydraulic code KORSAR
• Safety analysis for VVER Reactors
• 3D fluiddynamic calculations
• Neutron embrittlement of RPV vessels
• Validation of neutron fluence calculations
• Post operation investigation of RPV material from Greifswald NPP
• Neutron dosimetry of VVER 1000

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Kein Abstract vorhanden.

Introduction:

[18F]Fluoroacetate is discussed as an alternative to the well-established PET radiotracer [11C]acetate for the diagnosis and treatment monitoring of prostate cancer. The first automated synthesis of [18F]fluoroacetate was reported very recently by Sun and co-workers [1]. Herein we describe an alternative convenient remotely-controlled synthesis of no-carrier-added sodium [18F]fluoroacetate and its radiopharmacological evaluation in tumor bearing mice.

Experimental:

Three ethyl esters and three tert.-butyl esters containing either a methanesulfonyloxy- (OMs), p-toluenesulfonyloxy- (OTs) or p-nitrobenzene-sulfonyloxy (ONs) leaving group were investigated as labeling precursors.

Results and Discussion:

The optimized radiosynthesis of n.c.a. sodium [18F]fluoroacetate was performed in two steps: (1) Incorporation of fluorine into (methanesulfonyloxy)-acetic acid tert.-butyl ester 1 as the superior labeling precursor in acetonitrile at 100°C for 5 min followed by (2) acidic hydrolysis of the resulting [18F]fluoroacetic acid tert.-butyl ester at 100°C for 10 min to afford [18F]fluoroacetic acid. Several consecutive purification steps using anion exchange cartridges (Alltech Maxi-Clean SAX) and Sep-Pak neutral alumina cartridges gave sodium [18F]fluoroacetate in very reproducible radiochemical yields (20-25%, decay-corrected, n=20) in high radiochemical purity (>95%) within 50 min (Fig. 1).
Radiopharmacological studies were performed using rats and tumor bearing mice. Metabolism studies in arterial blood showed no metabolites after 60 min p.i. [18F]Fluoroacetate was readily accumulated in HT-29 tumors (tumor/muscle 1.75 ± 0.20 mean ± SEM, n=6) as shown in small animal PET studies (Fig. 2).

References: [1] L.-Q. Sun et al. Nucl. Med. Biol., 2006, 33, 153-158.

Conclusion:

The robust and reproducible remotely-controlled two step/one pot synthesis of [18F]fluoroacetate starting from readily available (methanesulfonyloxy)-acetic acid tert.-butyl ester 3a as a novel labelling precursor represents an alternative to the published procedures. A comparing discussion of data obtained with [11C]acetate in rats and mice will be presented.

Introduction:

Mirror-image oligonucleotides are constructed of an L-configured ribose or deoxyribose. This modification leads to an extraordinary high metabolic stability against enzymatic degradation in biological environments. The radiolabeling of an L-oligonucleotide with the positron emitter ⁸⁶Y (t_1/2 = 14.7 h) is done via the bifunctional chelator approach. The influence of two different [⁸⁶Y]DOTA chelates on the radiopharmacological properties of [⁸⁶Y]DOTA-L-oligonucleotides was investigated with an L-RNA 12mer 1 (sequence: 5'-Aminohexyl UGA CUG ACU GAC-3' MW 3975). Both ⁸⁶Y-labeled L-RNAs 3a, 5a were characterized by a comparative biodistribution study in Wistar rats and metabolite analyses.

Experimental:

The amine functionality of the 5'-hexylamine modified L-RNA 1 was used for conjugations with DOTA-NHS ester 2 and (S)-p-SCN-bz-DOTA 4, accomplished in the formation of a selective amide bond 3 and thiourea bond 5, respectively. After ⁸⁶Y-labeling of 3 and 5 biodistribution studies were performed for each compound 3a, 5a with eight Wistar rats.

Results and Discussion:

Both DOTA-modified L-RNAs 3, 5 were radiolabeled with ⁸⁶Y(III) (QSA Global, Germany) with radiochemical yields of 76 % and 85 %, respectively. High renal excretions were found for both ⁸⁶Y-labeled L-RNAs 3a, 5a whereas differences in the retention were observed for the radiolabeled compounds in the kidneys and the adrenal glands. The standardized uptake value (SUV) of compound 3a in the kidneys reached 10 ± 2.0 after 5 min and decreased to 6.1 ± 0.53 after 60 min. For compound 5a the SUV in the kidneys increased from 13 ± 1.6 after 5 min to 14 ± 1.1 after 60 min. Remarkably high SUVs (3.5 ± 0.48 and 3.2 ± 0.33) were also observed in the adrenal glands after 60 min for both compounds. The SUVs in other organs were below 1.0 after 60 min for 3a and 5a in this study. Over 85% intact 3a and 5a were found in urine samples of Wistar rats 60 min after application of 3a, 5a as confirmed by Radio-HPLC.

Conclusion:

Differences in the kidney excretion profile of 3a and 5a indicate an influence of the different chemical attachments of the [⁸⁶Y]DOTA chelates to L-RNA 1. The high metabolic stability of the L-RNA suggests the potential of L-oligonucleotides as molecular probes for PET.

Acknowledgement: This work was supported by the EU-FP6 integrated project BioCare contract no.: 505785.

Kein Abstract vorhanden.

Introduction:

We report on formation and structures of ⁶⁸Ga '4+1' complexes, [Ga(NS₃)R], with the tripodal ligand tris(2-mercaptoethyl) amine (NS₃) and water or secondary amines as co-ligands (R). To improve the bio-behavior of such compounds new hydrophilic NS₃ chelators have been introduced. Challenge experiments with transferrin have been performed to study the influence of the co-ligand on the in vitro stability of the gallium complexes. Their in vivo stability was evaluated in the rat using HSA microspheres.

Experimental:

⁶⁸Ga was eluted from a ⁶⁸Ge/⁶⁸Ga generator (Obninsk, Russia) as GaCl₃ in hydrochloric solution (0.1 M) and added to the aqueous solution of the oxalate salt of the NS₃ ligand in presence of the corresponding amine. Ga complexes were formed in aqueous solution at ambient temperature. Challenge experiments were carried out at 37°C with the plasma protein transferrin (5 mg/ml), the exchange was controlled by thin layer chromatography on silicagel (Merck) and methanol as eluent.

Results and Discussion:

The labelling procedure with ⁶⁸Ga generator eluate runs in high yield under weakly alkaline conditions within some minutes. It is not necessary to heat the reaction mixture so that sensitive molecules can also be labelled. Challenge experiments with apotransferrin were carried out for several hours. Amine-coordinated complexes as well as non-amine compounds showed high in vitro stability within 240 minutes. The in vivo stability of the complexes was evaluated in the rat using HSA microspheres. ⁶⁸Ga-labelled HSA microspheres were completely accumulated in the lung. In small animal PET studies no significant loss of ⁶⁸Ga activity was observed within three hours.

Conclusion:

The '4+1' mixed-ligand approach enables the ⁶⁸Ga-labelling of biomolecules under physiological conditions. The lipophilicity of the complexes can be controlled by introducing pharmacological modifiers (e.g. PEG, glucosamine, crown ether) into the tetradentate ligand and/or derivatization of the monodentate ligand. Moreover, the described approach allows the functionalization of a biomolecule with the tripodal as well as with the monodentate ligand.

Introduction:

Hypoxia is a common feature of solid malignant tumors. The vascular endothelial growth factor (VEGF) is upregulated by hypoxia inducible factors (HIFs) as a result of central hypoxia and plays an outstanding role for the formation of new tumoral blood vessels by promoting proliferation and migration of endothelial cells. Beside [^18F]fluorodeoxyglucose (¹⁸F-FDG) as standard radiotracer for tumor imaging with PET, oxygenation status in experimental and human tumors can be visualized by using [¹⁸F]fluoromisonidazole (¹⁸F-FMISO).

Experimental:

The aim of our study was the evaluation of the uptake of the radiotracers ¹⁸F-FDG and ¹⁸F-FMISO under standardized hypoxic conditions in various primary endothelial cells compared with three tumor cell lines in vitro. Experimental hypoxia was characterized by measurement of expression of HIF-1α, VEGF and various VEGF receptors by quantitative real-time PCR.

Results and Discussion:

Experimental hypoxia was confirmed by significant upregulation of characteristic hypoxia-related genes like VEGF in all analyzed primary endothelial cells and the tumor cell lines. VEGF receptors 1, 2 and 3 were almost absent in tumor cells and only expressed in endothelial cells. In contrast, the VEGF co-receptor Neuropilin-1 showed an increased expression in tumor cells under experimental hypoxia. In comparison to normoxic conditions, cellular uptake of ¹⁸F-FDG was significantly increased under experimental hypoxia in both tumor and endothelial cells. Otherwise, uptake of ¹⁸F-FMISO was always higher in tumor cells than in endothelial cells under hypoxic conditions.

Conclusion:

Our data showed a strong dependence of ¹⁸F-FDG uptake on the availability of oxygen in vitro. The study demonstrates relevance of endothelial cells as one important part of the tumor microenvironment under hypoxic conditions. This may have implications when performing PET studies aiming at the visualization and characterization of highly vascularized tumors, in particular, when using ¹⁸F-FDG.

Kein Abstract vorhanden.

no abstract available
Short-wavelength intersubband transitions and quantum cascade lasers in InP-based material systems

Kein Abstract vorhanden.

no abstract available
Silicon light-emitting pn diodes

Kein Abstract vorhanden.

Introduction:

Various Tc and Re chelates are currently under investigation for stable labeling of biomolecules. Unfortunately, most of the ¹⁸⁸Re chelates degrade more rapidly than the ^99mTc analogues which is limiting the further development of rhenium-based therapeutic agents. To overcome this problem, we developed a tetradentate S₄ ligands derived from DMSA [1].

Experimental:

Labeling. To a kit vial, containing 5 mg oxalic acid, 5 mg γ-cyclodextrin, 5 mg ascorbic acid and 0.01 - 0.05 mg Sn-S4 complex, 1.0 ml of perrhenate eluate (50–500 MBq) was added. After heating at 50 °C for 60' the yield was 90 – 93% (HPLC and TLC). For stability and biodistribution studies the isomers were separated by semi-preparative HPLC. The identity of the species obtained was confirmed by comparison with the HPLC profiles of fully characterized reference ^185/187Re analogues.
Biodistribution: Male Wistar rats (5 – 6 weeks old), 0.5 ml of the ¹⁸⁸Re complex solution (0.5 MBq) was injected into the tail vein under slight ether anesthesia. After the injection, the rats were sacrificed by heart puncture 5 min and 60 min post injection.

Results and Discussion:

A kit formulation was developed which contains only microgram amounts of the S₄ ligand stabilized in the form of a stannous complex. Several isomers were separated by HPLC from the preparation solutions and characterized in vitro and in vivo. All of them were absolutely stable in rat and human plasma solutions. Challenge experiments with cysteine corroborated the high inertness of the isomers towards ligand exchange reactions. Samples of blood, intestine and urine of rats confirmed the high in vivo stability of the ¹⁸⁸Re complexes. Biodistribution studies resulted in a high uptake and fast clearance from the liver of the more lipophilic cis and trans isomers of complex I (logD_o/w 1.5 - 1.7), whereas the hydrophilic isomers of complex II (logD_o/w about -1.75) were preferentially excreted via the renal pathway. The low level of radioactivity in the stomach indicated good in vivo stability too.

Conclusion:

The ¹⁸⁸Re-S₄ complexes offer the possibility of stable and high specific activity labeling of biomolecules. Their charge and lipophilicity may be controled by various possibilities to introduce functional groups. The amine group of the bridging framework makes available a position for coupling biomolecules.

[1] S. Seifert et al., Bioconjugate Chem. 2006, 17, 1601-1606.

Kein Abstract vorhanden.

Introduction:

Radiolabelled particles are an attractive tool in the therapy of malignancies of the liver. We consider particles manufactured from denatured human serum albumin (HSAM) as useful carriers of therapeutic radionuclides, e.g. Y-90.

Experimental:

Two batches of HSAM (ROTOP Pharmaka GmbH; diameter: 20 – 30 μm) with smooth or rough surface, as determined by REM, were used for our studies. HSAM were functionalized by coupling DOTA via its isothiocyanate derivative in aqueous solution at pH 8.5 to lysine ε-amino groups on the surface of the spheres. Stability of Y-86 labelled DOTA-HSAM was investigated both in vitro (DTPA challenge) and in vivo (i. v. injection into the tail vein of healthy Wistar rats).

Results and Discussion:

Approximately 25 DOTA molecules per molecule HSA could be attached as estimated from elemental analysis of DOTA-HSAM. Y-86 labelling was performed under optimized conditions in 96 ± 1 % yield. No significant differences between smooth- and rough-surfaced HSAM were found for both, DOTA coupling and Y-86-labelling. In DTPA challenge experiments 98 ± 0 % of the radioactivity were still particle-associated after 24 hours incubation at 37 °C. In the in vivo experiments radiolabelled smooth and rough microspheres were completely trapped in the lungs. After 48 h the two batches differed significantly in their biodistribution pattern. For the clearance of radioactivity from the lungs decay-corrected half-lives of 85 h (rough microspheres) and 187 h (smooth microspheres) were calculated.

Conclusion:

For the preparation of HSA-derived microspheres for radiotherapeutic application smooth-surfaced spheres are superior to rough spheres due to their higher in vivo stability.

The introduction of mammography screening programs in some countries initiated a continuous discussion about the benefit or possible accompanied risk of the used radiation qualities. Contributing to this discussion we used different methods, such as clonogenic survival and the analysis of chromosomal aberrations by FISH, to study biological effects with the human mammary epithelial cell line 184A1, which is of interest especially for the induction of breast cancer. Radiation qualities applied were 10 and 25 kV soft X-rays and a 200 kV X-ray tube as reference radiation source. Furthermore, we develop these methods and investigate the repair kinetics of DNA double strand breaks (DSB) with cell line 184A1 to learn more about the underlying processes.
The DNA damage response, following irradiation, includes an efficient DSB recognition system as well as different DSB repair mechanisms. Important contributions to these processes are the phosphorylation of histone H2AX (gH2AX) and the localization and phosphorylation of the p53 binding protein 1 (53BP1) at the sides of DNA DSBs. Both molecules are essential for the recognition of DNA DSBs and hence for the induction of repair processes. Using appropriate antibodies, the phosphorylated molecules can be visualized as nuclear foci and their time-dependent formation can be followed after irradiation.
The time-dependent formation of gH2AX- and 53BP1-foci was used in the present work to investigate the induction and rejoining of DNA DSBs up to 48 hours after irradiation. Two different antibodies were used to visualize and quantify the foci induced by two different doses of 0.25 and 2 Gy of 25 and 200 kV X-rays, respectively.
The kinetics obtained after irradiations with 2 Gy show a similar shape and therefore energy independence for both energies, which can be explained by the same underlying repair processes. Shortly after irradiation the number of foci per cell shows a steep increase, resulting in a maximum after 2 hours and a subsequent 2-phase decrease. Although the position of the maximum is the same, the number of foci per cell differs for 25 kV and 200 kV X-rays, being 7.99 ± 0.12 and 6.19 ± 0.10, respectively. The rejoining of DSBs, deduced by the decrease of number of foci per cell can be divided in a first phase, which seems to be faster, and a slower second one. During the first phase, the number of foci per cell is reduced to about 50 % of the maximum and in the second phase they are reduced to the control level, whereas for 25 kV a significant number of foci per cell remain. These results implicate that, on the one hand, the number of the induced DNA DSBs is significantly higher for 25 kV X-rays and, that on the other hand, some DSBs remain unrepaired. These DSBs can influence the genomic integrity and can result in chromosomal aberrations.
First experiments for the irradiation with 0.25 Gy of 25 kV show the same shape as that with higher dose, but the maximum is derived at 30 minutes after irradiation. The maximum number of foci per cell was 4.03, which is about the half compared to a dose of 2 Gy with the same energy.

Lead-bismuth alloys are under intense consideration as target material of spallation sources. The thermohydraulic design of such a target or related coolant systems requires a reliable data basis regarding the temperature dependent physical properties of such alloys. We present new measurements of the electrical conductivity and the thermoelectric power up to about one hundred degree above the melting point for various alloy compositions. For the eutectic alloy the measurements were performed up to a temperature of 1000 K including, in addition, viscosity, thermal conductivity and surface tension. A comparison with data and scaling relations available in literature will be given. New temperature scaling relations will be derived for each of those properties, which we recommend as input for thermohydraulic simulations.

The objective of the European 6th framework project EUROTRANS, is to demonstrate the technical feasibility of transmutation of high level nuclear waste using Accelerator Driven Systems (ADS). Within this objective the design of a European experimental ADS (XT-ADS) should demonstrate the technical feasibilities to transmute a sizeable amount of waste and to operate an ADS safely. The XT-ADS will be a subcritical reactor system having liquid lead-bismuth eutectic (LBE) as coolant.
This liquid LBE is also intended to serve as target material for the spallation reaction which forms a crucial part to the subcritical reactor core. Since LBE is used as core coolant and spallation material, knowledge of the thermal hydraulic behaviour of LBE is essential.
Within the DEMETRA domain of the EUROTRANS project, basic thermal hydraulic studies in order to support the design and safety analysis of XT-ADS components and the development of measurement techniques have been started. In particular, the work focuses on:
• Characterisation of the free surface flow for the windowless spallation target design.
Validated numerical methods are needed to predict the LBE heat removal capability in the windowless spallation target configuration. For this purpose, computational fluid dynamics (CFD) simulation methods are most appropriate. CFD methods allow to capture the specific three-dimensional local effects of the LBE free surface including the heat deposition.
Various methods are assessed and first promising results have been obtained for the simulation of an isothermal windowless spallation target. For the improvement and validation of the developed numerical models, an experimental campaign has started. This campaign exists of experiments in a water-loop and in an LBE loop.
• The interaction of LBE with water as secondary coolant.
Since the XT-ADS design foresees the presence of steam generator modules placed inside the main vessel in direct contact with the lead-bismuth and the probability of a steam generator tube rupture is not negligible, the consequences of such an accident have to be assessed. Experimental campaigns aim at assessing the physical effects and possible consequences related to the interaction of LBE and water in representative conditions for the XT-ADS design. The experimental data are also used for the validation of the SIMMER code. First experimental campaigns have been performed successfully. Simulation of the experimental data with the SIMMER code showed a good agreement.
• The development of measurement techniques for heavy liquid metal (HLM) flows.
Measurement techniques are developed for different purposes (i.e. thermal-hydraulics experiments and operational techniques for large facilities in relation to the development of the XT-ADS) and tested within the laboratories of FZD (Germany), FZK (Germany), and SCK•CEN (Belgium). The focus is on local velocity meters, integral flow meters, and free surface level sensors. The various methods studied are briefly described.

Finally, the links with the DESIGN domain of the EUROTRANS project, with the European Commission Integrated Infrastructure Initiative VELLA (Virtual European Lead LAboratory), and with the European Commission Specific Targeted Research Project ELSY (European Lead-cooled System) are also addressed.

Objective:

To investigate the role of magnetic resonance imaging (MRI) of bone metastases in nonseminomatous germ cell tumors.

Methods and Materials:

There were 5 consecutive patients with bone metastases from nonseminomatous germ cell tumors treated
between 2003 and 2006 who underwent imaging studies, including MRI. The characteristic imaging findings are discussed in the light of the clinical course.

Results:

Of the 5 patients, 3 had symptoms related to bone involvement at diagnosis. All patients received conventional x-ray of their bony lesions, but only 1 of them was considered abnormal. Skeletal MRI was obtained in all patients. A bone scan was available in 3 cases with spinal involvement. It was normal in 1 case and detected only a minority of the lesions visible on MRI in the other 2 cases. Follow-up MRIs were available in all patients. A partial resolution of bone involvement during chemotherapy was observed in only 1 of them. In 2 cases, there was a slight progression of a diffuse alteration of the bone marrow during treatment. In 1 patient, severe spinal bone marrow
changes were visible on MRI 2 years after cessation of treatment without evidence of disease recurrence.

Conclusions:

MRI may disclose bone metastases in nonseminomatous germ cell tumors, which otherwise may be missed. MRI findings of bone lesions during treatment do not directly reflect the course of the disease and have to be interpreted with caution using clinical information.

Administration of ionizing radiation for diagnostic purposes can be associated with a risk for the induction of tumors. Therefore, particularly with regard to general screening programs, e.g. with mammography, cost-benefit considerations must be discussed including risk estimation depending upon the radiation quality administered. The present study was initiated to investigate the in vitro X-ray energy dependence for the induction of chromosomal aberrations in the two mammary epithelial cell lines, 184A1 and MCF-12A. The induced excess fragments, dicentric chromosomes and centric rings were analyzed and the relative biological effectiveness (RBE) was determined for 10 and 25 kV X-rays relative to 200 kV X-rays. The assumed energy dependence with higher values for 10 kV X-rays was confirmed for the excess fragments, with RBEM values of 1.92 +/- A 0.26 and 1.40 +/- A 0.12 for 10 kV X-rays and 1.17 +/- A 0.12 and 0.97 +/- A 0.10 for 25 kV photons determined for cell lines 184A1!
and MCF-12A, respectively. Meaningful results for the induction of dicentric chromosomes and centric rings were obtained only for higher doses with RBE values of 1.31 +/- A 0.21 and 1.70 +/- A 0.29 for 184A1 and 1.08 +/- A 0.08 and 1.43 +/- A 0.12 for MCF-12A irradiated with 25 and 10 kV X-rays, respectively.

Die Anwendung dynamischer Betriebsweisen bei abwärts durchströmten Festbettreaktoren zur Erhöhung der Phaseninteraktion und zur Steigerung der Katalysatoreffektivität wurde experimentell bereits erfolgreich nachgewiesen. Aufgrund der komplexen Zusammenhänge erfordern Modellierung und Simulation dynamisch betriebener Festbettreaktoren ein umfangreiches Wissen über makroskopische und mikroskopische Vorgänge und deren Kopplung. Bisherige Reaktormodelle vernachlässigen die Vorgänge im Katalysatorpartikel nahezu komplett oder verzichten auf die Kopplung mit Reaktormodellen.
Das entwickelte mehrskalige isotherme Modell setzt sich aus dem axialen Dispersionsmodell im Reaktormaßstab und einem Partikelmodell zur Berücksichtigung von dynamischen intrapartikulären Konzentrationsprofilen und Akkumulationen zusammen. Zusätzlich zur veränderlichen Teilbenetzung der Katalysatoroberfläche wird ein Verteilungsfaktor eingeführt, der die Morphologie der Flüssigkeit auf der Katalysatoroberfläche als Maß für die Gleichmäßigkeit der Verteilung beschreibt.
Das quasi-3D-Modell wurde in COMSOL MultiphysicsTM 3.2 umgesetzt und ermöglicht die Simulation ausgewählter dynamischer Zustände, die Ableitung günstiger Betriebsparameter zur Leistungssteigerung bei Festbettreaktoren und die Analyse optimaler Katalysatorkonfigurationen ohne aufwendige experimentelle Parameterstudien. Die Simulationsergebnisse für die Hydrierung eines organischen Lösungsmittels werden mit experimentellen Daten verglichen.

Metallorganische Verbindungen, wie beispielsweise Grignard-Reagenzien, haben große Bedeutung als Zwischenprodukte für organische Synthesen in der Feinchemie und der pharmazeutischen Industrie. Auf Grund des spezifischen Prozessverhaltens der stark exothermen Bildungsreaktionen und der hohen Reaktivität der Grignard-Reagenzien besitzen Grignard-Reaktionen ein hohes Gefahrenpotential. Von großer Bedeutung für die Prozesssicherheit ist deshalb die Entwicklung industriell anwendbarer Methoden für eine objektive Detektion des Reaktionsstarts und für die Online-Verfolgung von Edukt-Akkumulationen im Reaktionsgemisch des Rührkessel-Reaktors. Hierfür wurde eine wärmebilanzbasierte Online-Überwachungsmethode entwickelt und anhand von Experimenten im Miniplant getestet. Neben der Ermittlung von Konzentrationsverläufen ist mit der Methode eine Abschätzung von sicherheitsrelevanten Parametern realisierbar (on-line worst case calculations). Die Ergebnisse ermöglichen den Einsatz sicherheitsorientierter Regelungsstrategien für Grignard-Reaktionen. Gleichzeitig können derartige Systeme zu einer Erhöhung der Effizienz durch Steigerung der Raum-Zeit-Ausbeute sowie zur Realisierung einer inhärenten Prozesssicherheit beitragen. Durch Einbindung in ein komplexes Batch Information Management System (BIMS) können die Ergebnisse des Monitoring Systems chargenweise zusammen mit den Prozess-, Anlagen- und Analysedaten gespeichert und archiviert werden und dienen somit einer späteren Prozessanalyse und –optimierung.

There is no abstract provided.

Low-energy (<100eV) ion bombardment has been shown to be a key parameter in the production of hard and elastic carbon nitride (CNx) thin films with fullerene-like (FL) structure [1]. The production of FL-CNx is mostly reported for reactive magnetron sputtering but still the growth mechanisms are not clear [2]. In this way, the growth by ion beam assisted deposition (IBAD) would provide a better understanding since the source of neutrals and ions are independent. In this work we study the growth of CNx films produced by e-beam evaporation of graphite and simultaneous low-energy N2 ion assistance at different substrate temperatures. The low-energy ions were provided by an End-Hall ion source. The samples were characterized by spectroscopic ellipsometry, elastic recoil detection analysis (ERDA), Raman and high resolution transmission electron microscopy (HRTEM). Despite the low-energy ions, a high thermal-activated re-sputtering of the deposited films has been observed, indicating its chemical origin. In addition, the maximum nitrogen content in the films is limited to ~25 at.%, which should be related to the re-sputtering process. The Raman spectra and the optical properties indicate the dominance of sp2 hybrids. However, the results differ from those of FL-CNx, indicating that the sp2 hybrids are not arranged in a FL microstructure. This is also corroborated by HRTEM, where the samples were found to be mainly amorphous. Therefore, our results suggest that low-energy ion bombardment is not the main driving force for the promotion of FL arrangements, although this condition may be necessary to avoid damage on the growing microstructure. In this sense, the incorporation of neutrals, such as CxNy species formed during magnetron sputtering, may play a dominant role for the growth of FL-CNx [3].
1. Sjöstrom et al. Phys. Rev. Lett. 75 (1995) 1336. 2. Hultman et al. MRS Bulletin 28/3 (2003) 194. 3. Neidhardt et al. J. Appl. Phys. (in press).

Thermal treatment of indium tin oxide (ITO) is often used as a method to decrease its resistivity. The amorphous-to-crystalline transition is often assumed as the reason for this improvement due to a Sn donor activation at elevated temperatures (Frank-Koestlin model), but the physical mechanisms behind the experimental observation are not clear. In present work, ITO thin films produced by reactive middle frequency magnetron sputtering were annealed in vacuum in two ways: 1) annealing within the temperature range Ta=20-330 °C at a constant heating rate of 5 °C/min, 2) isothermal annealing at Ta=210 and 240 °C. The amorphous layers and films with a small crystalline fraction have been investigated. This study is focused on in situ spectroscopic ellipsometry (SE) monitoring of the film properties during annealing. The SE data were reduced by using the Drude-Lorentz parameterization of ITO optical constants. In separate experiments, the films were investigated by in situ four point probe resistivity measurement technique and the in situ X-ray diffraction (XRD) in Bragg-Brentano geometry.
The observed temperature dependences of the ellipsometry parameters and resistivity indicate several stages (typically four) in contrast to the simpler two-stage behavior of these characteristics obtained during isothermal annealing. Even in the XRD-amorphous state, the film resistivity significantly decreases with increasing temperature due to a free-electron density enhancement as shown by SE. The increase of the free-electron density in this case can be attributed to the creation of oxygen vacancies due to relaxation of distorted In-O bonds in the amorphous phase. Since Sn is known not to be electrically active in amorphous ITO and does not affect the free-electron density, any creation of substitutional Sn in the amorphous film can be neglected. Tin donor activation gives significant contribution to a free electron density only at temperatures above 250 °C which agrees with the crystallization onset suggested by in situ XRD. The crystallization kinetics is analyzed by using the Kolmogorov–Johnson–Mehl-Avrami equation which yielded a kinetic exponent of the process of approximately 3. Under the condition that the coherently diffracting domain size is smaller than the film thickness, this kinetic exponent indicates a three-dimensional crystallization process. The refractive index decreases at increasing annealing temperature above 150 °C. An even stronger decrease is observed above Ta=250 °C, both processes are related to the enhancement of the free electron density.

The report summarizes the most important technical developments realized in 2003/2004 at the Materials Research end-station. There are described new programs which simplify the visualisation and analysis of a large amount of data. These data are collected by a linear position sensitive detector (PSD) and a multi-channel analyzer. Additionally, an electronic stepperrmotor controller switch had been developed. It allows to use two different types of stepper motor controllers to control four of the axes of a 6-circle HUBER-diffractometrer by two different instrumentation systems.

Tag des offenen Labors, FZD

A new multi-element detector with higher energy resolution was aqcuired which is instrumented with a high-rate digital multi-analysis spectrometer from X-ray Instrumentation Associates (XIA) which is particularly well suited for EXAFS with multi-element detectors. The installation of this new detector involved not only electronic instrumentation and software development, but - due to the complex radiochemical safety system at the Radochemistry end-station -also mechanical engineering.

A tin liquid metal ion source (LMIS) containing ~ 13% Pb has been studied. From a careful examination of the mass spectra of the source it is concluded that post-ionisation is a most probable mechanism for the formation of Pb++ ions. In the case of tin, however both Sn+ and Sn++ appear to form by direct field-evaporation. This view is supported by energy deficit measurements on the Sn+ and Sn++ beams . Our results for Pb++/Pb+ agree with those of Komuro (1983) with a pure Pb source. The reason for this is understandable and is related to the similarity between the evaporation fields of Sn and Pb. For the sake of completeness we also present measurements of the energy spread of the Sn++ and Sn+ beams.

Focused ion beam applications using ions other than Gallium are of increasing interest during the previous years. A promising candidate is Germanium due to its compatibility to the semiconductor technology, i.e. for local doping of SixGe1-x structures. The energy spread ΔE½ of the source, which, through the chromatic aberrations of the system, determines the final spot size at the target and the peak energy deficit (PED) as well as the mass spectra emitted from an eutectic Au73Ge27 (m.p.=366°C) alloy liquid metal ion source were investigated as a function of the emitter temperature. ΔE½, measured with a retarding field analyser, is expressed as the full width of the distribution at half its maximum height (FWHM). Doubly-charged ions achieve double of energy, compared to singly-charged ions, which is taken into account for analysis. Furthermore, Ge shows a much more abundant in the doubly-charged state, following Brandon`s criterion. Due to the analysis of PED we think Ge++ as well as Au+ and Ge+ are directly field-evaporated in the doubly- and singly-charged state, respectively. Au++ should be post-ionized from the singly-charged state.
Due to the regular expected behaviour of the surface tension dependence on temperature shows in contrast to Si containing metallic glass alloys, like AuSi or AuGeSi, that the ion emission is enhanced with increasing temperature, obtained from a field of I-V-characteristics. The slope of this change also depends on the volume of the source reservoir, which is demonstrated for a drop volume of 0.5 and 3.4 mm3, respectively, in the temperature range from 400 to 1000 °C. The mass spectra, measured with an E x B analyser are evaluated with respect to the emission intensity for the main ion species Au+ and Au++, Ge+ and Ge++ and for various molecular ions and clusters, formed by droplet disintegration. The ratio of doubly-charged to singly-charged monomer species is given as a function of temperature in the emission current range of 1 to 30 µA.