Technetium is the lightest element whose isotopes are all radioactive. Among them, 99Tc (hereafter simply referred as technetium or Tc) is the most abundant and raises great environmental concern due to its relatively long half-life of 2.14×105 years and the high mobility of pertechnetate, Tc(VII)O4, its most stable form under aerobic conditions. The reduction from Tc(VII) to Tc(IV) is one of the most successful strategies for Tc immobilization; however, the mechanism of this redox reaction is not yet fully understood. This presents a large gap in the general knowledge of technetium chemistry and a significant obstacle for the modeling of its reactivity in contexts like a nuclear waste repository. This thesis was developed in the frame of the BMWi funded VESPA II project, and it studies the surface-mediated reduction of 99Tc(VII) using a combination of fundamental chemistry and its application for remediation and nuclear waste management. First, spectro-electrochemical methods (cyclic voltammetry, rotating disk electrode, chronoamperometry coupled with UV-vis, Raman microscopy and nuclear magnetic resonance) were employed to study the reduction mechanism of 0.5 mM KTcO4 in non-complexing media (2 M NaClO4) in the pH range from 2.0 to 10.0. It was found that the mechanism depends on the pH. At pH 2.0 it splits into two steps: Tc(VII) gains 2.1 ± 0.3 electrons and becomes Tc(V) that rapidly reduces to Tc(IV) with the transfer of further 1.3 ± 0.3 electrons. In contrast, at pH ≥ 4.0 there is a direct transfer of 3.2 ± 0.3 electrons. The complete reduction of Tc(VII) yielded a black solid that was successfully characterized by NMR and Raman microscopy as Tc(IV) regardless of the initial pH at which the reaction occurred. Unfortunately, it was not possible to observe the Tc(V) species at pH 2.0 by the spectroscopic tools used. Second, the reductive immobilization of Tc(VII) by pure pyrite and a synthetic mixture marcasite-pyrite 60:40 (synthetic FeS2, with both minerals being polymorphs) was studied by a combination of batch sorption experiments (Tc-removal was studied varying pH, contact time, ionic strength and Tc concentration) and several spectroscopies and microscopies such as Raman microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and VIII X-ray absorption spectroscopy. It was found that both pyrite and the synthetic FeS2 promote the reduction of Tc(VII) to Tc(IV). In the case of pure pyrite, the Tc-removal is complete after one day in contact at pH ≥ 5.5. The spectroscopic analysis showed at pH 6.0 an inner-sphere complex between Tc(IV) dimers and hematite formed as secondary mineral on the pyrite surface. In contrast, at pH 10.0 Tc(IV) gets incorporated into surficial magnetite by replacing Fe3+ in octahedral position, with Fe2+ providing reasonable charge compensation for Tc4+. The presence of marcasite made the process slower and less efficient since the synthetic FeS2 was capable to remove 100% Tc from solution only after seven days in contact at 6.0 < pH ≤ 9.0 while the Tc-removal at pH 10.0 was only around 80%. At pH 6.0 the formation of hematite was also observed, suggesting that the formed Tc(IV) species at the surface is the same as with pure pyrite. However, at pH 10.0 the formation of sulfate minerals evidences a change of redox active species: S2- instead of Fe2+. This, combined with the fact that in both solids the formation of TcSx species was detected by XPS at pH 10.0, shows the potential of sulfur as another reducing agent for Tc(VII). The effect of polymorphism on the Tc removal is remarkable and this work shows the relevance of more studies on the interaction of radionuclei with other mineral polymorphs. Regardless of the kinetics of the Tc removal, both pyrite and synthetic FeS2 hindered the re-oxidation of Tc(IV) when exposed to ambient atmosphere for two months. This feature makes them good candidates for the remediation of technetium from contaminated waters. Moreover, natural attenuation effects can be expected for technetium in the near and far field of nuclear waste repositories wherever iron sulfide is present. The results presented in this work contribute to a better understanding of the fundamental aqueous chemistry of technetium and confirm pyrite, a ubiquitous mineral, as a very good candidate for technetium scavenging even in the presence of marcasite. These results close important gaps in thermodynamic databases that are needed for the safety assessment, i.e. modeling of fission products.

The aim of this work was the development of a method for the generation of surface features on n-type silicon samples with deeply buried p-implants, in the form of heterogeneities aligned directly above the buried implants. This task was motivated by the realisation of a simpler process for the formation of superjunction transistors, which currently require the repeated creation of the same implantation structure over multiple steps of photolithography These lithography steps can be potentially replaced, if a suitable process for the self-alignment in accordance to the buried implants can be found. The work on this goal was separated into three parts: the analysis of samples for suitable surface properties, the generation of surface heterogeneities using such a property and the analysis of the mechanism for the used process of contrast generation. Within this doctoral thesis, a before unseen method of selective etching on silicon was discovered and investigated. Hence, the overall aim of this work was successfully achieved. • Samples containing buried p-implants inside a n-type silicon substrate were characterised with regard to various properties. Of these, the through-sample resistance showed a significant variation in accordance to the buried implants also through a homogeneous epitaxial layer. • Various methods aimed at the usage of the resistance variation in order to generate a surface heterogeneity through electrodeposition failed to enable a suitable process. Instead, another method was found, which enables the replication of the implant structure via selective etching. This novel process enables the lithography free patterning of the substrates through a simple alkaline etch process performed under illumination. This results in a surface heterogeneity as an alteration of the sample topography combined with a material contrast due to the formation of an in-situ SiO2 etch mask. This material variation can also be used for the selective deposition of polymers, enabling further processing of the etched samples. • For this new method, named Light Induced Selective Etching (LISE), a mechanism underlying the selectivity was proposed and through a number of experiments. In essence, the illumination during the etching process produces a flux of photogenerated electrons directed from the buried implants toward the surface, which increase the negative surface charge in the areas above these implants. The locally increased surface charge causes a local protection of the native silicon oxide layer against the alkaline etching, leading to the structuring of the substrate. In essence, this novel method allows for the previously unreported self-adjusted structuring of silicon based on deeply buried implant structures. In general, even the characterisation of such implant structures is difficult, whereas this method allows for structuring with regard to such buried structures with a very simple setup of only an etchant solution and a suitable light source. With regard to the introduction and motivation of this thesis, this process can possibly be applied for the intended purpose of creating a self-aligned resist in order to replace repeating lithography steps. This is the case in particular in combination with polymer deposition, as shown in the last part of the results. Certain limitations, such as the resolution limit and dimensional size increase exist, but can be circumvented by appropriate device design and further optimisation of the process parameters. Furthermore, the LISE process appears applicable for the manufacturing of MEMS and MOEMS devices, as the typical feature sizes in these cases fit well to the achieved resolution of the LISE process. For devices needing a certain implant structure in combination with a corresponding topography, the new method allows for the elimination of at least one lithography step, including the necessary substeps such as alignment and measurement. Accordingly, LISE has the potential of simplifying the manufacturing process, enabling better and cheaper devices.

In der vorliegenden Arbeit werden Synthesen von sterisch anspruchsvollen sekundären wie auch tertiären Aminen und Enaminen untersucht. Ein Großteil der Arbeit befasst sich mit der Darstellung von N-Chloraminen, die im weiteren Verlauf zu sek. und tert. Aminen und Enaminen, mit Hilfe von metallorganischen Reagenzien und N,N,N',N'-Tetramethylethylendiamin (TMEDA), umgesetzt werden. Die dabei resultierenden Amine werden, auf Grund ihrer gehinderten Rotation, NMR-spektroskopisch untersucht. Dabei werden diverse dynamische Effekte bei verschiedenen Temperaturen beobachtet und gedeutet. So lassen sich auf diese Weise Rotationsbarrieren berechnen und vergleichen. Das gibt Aufschluss über die sterische Hinderung von verschiedenen Alkylgruppen. Weiterhin wird eine Eliminierung von Olefinen bei tert. Aminen beobachtet, welche der Hofmann-Eliminierung ähnelt. Diese verläuft anders als in Lehrbüchern beschrieben. Außerdem werden die Aktivierungsenergie und Isotopeneffekte der Eliminierung untersucht. Diese Zersetzung erfolgt auch mit Alkalimetallen als Katalysatoren. Eine Herstellung von neuartigen Enaminen aus 'turbo'-Amiden und gespannten Verbindungen wie Cyclooctin wird ebenfalls beschrieben. Die Enamine werden durch NMR-Spektroskopie auf ihren Olefincharakter untersucht. Eine neue Synthese von hochsubstituierten Pyrrolidinen und entsprechenden Iminiumsalzen, aus sek. tert-Octylaminen, wird vorgestellt. Diese Darstellung ist eine Erweiterung der Hofmann-Löffler-Freytag-Reaktion, welche eine radikalische Ringschlussreaktion beinhaltet. Die Darstellung der Iminiumsalze erfolgt metallfrei, durch die Oxidation mit N-Bromsuccinimid (NBS).:Abkürzungsverzeichnis VIII Abbildungsverzeichnis XII 1 Einleitung 1.1 Bedeutung von Aminen 1.2 Alkylierung von N -Haloaminen 1.3 Sterische Hinderung und Dynamische NMR-Spektroskopie 1.4 Zielstellung 2 Ergebnisteil 2.1 Darstellung neuer, sekundärer Amine als Vorstufen weiterer Synthesen 2.2 Darstellung tertiärer Amine 2.2.1 Darstellung diverser N -Chloramine für die elektrophile Aminierung 2.2.2 Reaktionen an N,N-Dichloraminen 2.2.3 Alkylierungen am tert-Butyl-tert-octylamin 2.2.4 Elektrophile Aminierungen an weiteren N-Chloraminen 2.2.4.1 Cycloalkylierung zu tert. Aminen 2.2.4.2 Isopropylierung am Stickstoff 2.2.4.3 Einführung der Neopentylgruppe 2.2.4.4 Versuche der Einführung tertiärer Gruppen 2.2.5 Synthese von tertiären Enaminen 2.2.6 Reaktion zwischen gespannten Verbindungen und Metallamiden 2.2.7 Acylierungen von sterisch anspruchsvollen Aminen 2.2.8 Synthese von tertiären Aminen aus Amiden 2.2.9 Ringschlussreaktionen zu möglichen CAAC-Vorläufern 2.3 Untersuchungen zur Hofmann-Eliminierung bei tertiären Aminen 2.3.1 Untersuchung der Aktivierungsenergie der Eliminierung 2.3.2 Hofmann-Eliminierung katalysiert durch Alkalisalze 2.3.3 Untersuchungen zum Isotopeneffekt 2.3.4 Zersetzungen von tertiären Aminen durch Methanol 2.4 Dynamische NMR-Spektroskopie bei tertiären Aminen 2.4.1 Rotamere in der C2V -Symmetrie 2.4.2 Rotamere in der C2H-Symmetrie 2.4.3 Komplexe dynamische Rotamere 3 Zusammenfassung und Ausblick 4 Experimenteller Teil 4.1 Experimentelles Arbeiten 4.1.1 Arbeiten unter inerten Bedingungen 4.1.2 Umkondensation 4.1.3 Säulenchromatographie 4.2 Analytisches Arbeiten 4.2.1 NMR-Spektroskopie 4.2.2 GC-MS 4.2.3 Analytischer Gaschromatograph 4.2.4 HRMS 4.3 Elementaranalyse 4.4 Röntgeneinkristallstrukturanalyse 4.5 Synthesevorschriften 4.5.1 Synthese von tert-Butyl-diisopropylamin (2) 4.5.2 Synthese von tert-Butyl-diisopropylamin (2) und Di-tert-Butylamin (14) 4.5.3 Synthese von N -(1-Adamantyl)-N-tert-octylamin 23 4.5.4 Synthese von N -tert-Octyl-tritylamin 24 4.5.5 Synthese von N -(2,6-Dimethylheptan-2-yl)acetamid (26) 4.5.6 Synthese von 2-Amino-2,6-dimethylheptan (27) 4.5.7 Synthese von 2-Azido-2,6-dimethylheptan (28) 4.5.8 Synthese von N -Isopropyl-2,6-dimethylheptan-2-amin (29) 4.5.9 Synthese von N -(1-Adamantyl)-2,6-dimethylheptan-2-amin (32) 4.5.10 Synthese von 4-Chlor-3,3,5,5-tetramethylmorpholin (34a) 4.5.11 Synthese von 2,2'-(Chlorimino)bis(2-methylpropan-1-ol) (34b) 4.5.12 Synthese von N -tert-Butyl-N -chlorcyclohexylamin (34c) 4.5.13 Synthese von N -Chlor-N -isopropyl-N -tert-octylamin (34d) 4.5.14 Synthese von N -(1-Adamantyl)-N -chlor-N -tert-octylamin 34e 4.5.15 Synthese von N -(1-Adamantyl)-N -chlor-2,6-dimethylheptan-2-amin (34f) 4.5.16 Synthese von 8-Chlor-7,7,9,9-tetramethyl-1,4-dioxa-8-azaspiro- [4.5]decan (34g) 4.5.17 Synthese von 4-Chlor-3,3,5,5-tetramethylmorpholin-2-on (34h) 4.5.18 Synthese von N -Chlor-N -tert-butyl-N -tritylamin (34i) 4.5.19 Synthese von Di-tert-butyldiazen (37) 4.5.20 Synthese von N -(1-Adamantyl)-neopentylamin (38d) 4.5.21 Synthese von N -tert-Butyl-N -cyclohexyl-N -tert-octylamin (40b) 4.5.22 Synthese von N -tert-Butyl-N -cyclopentyl-N -tert-octylamin (40c) 4.5.23 Synthese von N -tert-Butyl-N -isobutyl-N -tert-octylamin (40d) 4.5.24 Synthese von N -tert-Butyl-N -sec-butyl-N -tert-octylamin (40e) 4.5.25 Synthese von N,N -Diisopropyl-tert-octylamin (40f) 4.5.26 Synthese von N 1,N 4-Di-tert-butyl-2,2,4-trimethyl-N 1-(2,4,4-trimethylpentan-2-yl)pentan-1,4-diamin (43) 4.5.27 Synthese von 8-Cyclohexyl-7,7,9,9-tetramethyl-1,4-dioxa-8-azaspiro[4.5]decan (44a) 4.5.28 Synthese von N -Cyclopentyl-2,2,6,6-tetramethylpiperidin (44b) 4.5.29 Synthese von N,N -Di-tert-butylcyclohexylamin (44c) 4.5.30 Synthese von Di-tert-butyl-cyclopentylamin (44d) 4.5.31 Synthese von N -tert-Butyl-N,N -dicyclohexylamin (44e) 4.5.32 Synthese von 8-Isopropyl-7,7,9,9-tetramethyl-1,4-dioxa-8-azaspiro[4.5]decan (46a) 4.5.33 Synthese von 4-Isopropyl-3,3,5,5-tetramethylmorpholin-2-on (46b) 4.5.34 Synthese von N -(1-Adamantyl)-N -isopropyl-N -tert-octylamin (46c) 4.5.35 Synthese von N -(1-Adamantyl)-N -isopropyl-2,6-dimethylheptan2-amin (46d) . 4.5.36 Synthese von 8-Neopentyl-7,7,9,9-tetramethyl-1,4-dioxa-8-azaspiro [4.5]decan (47a) 4.5.37 Synthese von N -Neopentyl-2,2,6,6-tetramethylpiperidin (47b) 4.5.38 Synthese von 4-Neopentyl-3,3,5,5-tetramethylmorpholin (47c) 4.5.39 Synthese von N,N -Di-tert-butyl-neopentylamin (47d) 4.5.40 Synthese von N -tert-Amyl-N -tert-butyl-neopentylamin (47e) 4.5.41 Synthese von 1,1,3-Triethyl-1H -isoindol (49) 4.5.42 Synthese von (E)-4-(Di-tert-butylamino)but-3-en-1-ol (51) 4.5.43 Synthese von N -tert-Butyl-N -tert-octyl-N -prop-1-en-2-ylamin (58a) 4.5.44 Synthese von N,N -Di-tert-butylprop-1-en-2-amin (58b) 4.5.45 Synthese von 2,2,6,6-Tetramethyl-1-(prop-1-en-2-yl)piperidin (58c) 4.5.46 Synthese von (E)-N,N -Diisopropylcyclooct-1-enamin (60a) 4.5.47 Synthese von (E)-N -(tert-Butyl)-N -isopropylcyclooct-1-enamin (60b) 4.5.48 Synthese von (E)-1-(Cyclooct-1-en-1-yl)-2,2,6,6-tetramethylpiperidin (60c) 4.5.49 Synthese von 1,2:3,4:5,6-tris(hexamethylen)benzol (61) 4.5.50 Synthese von (Z)-2-(Diisopropylammonio)-3-oxocyclooct-1-enolat (62) 4.5.51 Synthese von N -(2,4,4-trimethylpentan-2-yl)acetamid (66a) 4.5.52 Synthese von 2-Phenyl-N -(2,4,4-trimethylpentan-2-yl)acetamid (66b) 4.5.53 Synthese von Di-tert-butyl-ethenylamin (69) 4.5.54 Synthese von 1-(1-Methoxyvinyl)-2,2,6,6-tetramethylpiperidin (71) 4.5.55 Synthese von N -tert-Butyl-N -isobutyl-N -isopropylamin (75) 4.5.56 Synthese von 1-tert-Butyl-2,2,4,4-tetramethyl-3,4-dihydro-2H-pyrroliumchlorid (77a) 4.5.57 Synthese von 1-tert-Butyl-2,2,4,4-tetramethyl-3,4-dihydro-2H-pyrroliumbromid (77b) 4.5.58 Synthese von 1-(1-Adamantyl)-2,2,4,4-tetramethyl-3,4-dihydro-2H-pyrroliumbromid (77f) 4.5.59 Synthese von 1-(tert-Butyl)-5-butyl-2,2,4,4-tetramethylpyrrolidin (79c) 4.5.60 Synthese von 1-(tert-Butyl)-2,2,4,4,5-pentamethylpyrrolidin (79d) 4.5.61 Synthese von 5-(Dibrommethyl)-2,2,4,4-tetramethyl-3,4-dihydro-2H-pyrrol (80) 4.5.62 Synthese von 1-(1-Adamantyl)-2,2,4,4,5-pentamethylpyrrolidin (85) 4.5.63 NMR-Daten von 2,2'-(tert-Butylazadiyl)bis(2-methylpropanal) (101)

This PhD thesis aims to improve the knowledge on the processes and chemical species in the gas- and particle-phases that are involved in the production of secondary organic aerosol (SOA) from monoterpene oxidation in the atmosphere. A denuder/filter technique that enabled the simultaneous sampling of gaseous and particulate compounds was applied in the present study. The sampling technique was comprehensively characterised and optimised using twelve atmospherically relevant carbonyl compounds. The present study improved the denuder coating procedure and the sampling performance. An additional coating with the derivatisation reagent, 2,4‑dinitrophenylhydrazine (DNPH), reduced the break-through potential (e.g., from 98% to 0.9% for methyl vinyl ketone) and the fraction of carbonyl compounds on the filter material (e.g., from 8.7% to 0% for acetone). Calibration experiments against an aerosol chamber were performed to reduce the relative standard deviation (RSD) of the calibration points in the denuder measurements. The RSDs were reduced by half for acetone, acetaldehyde, methyl vinyl ketone, glyoxal, benzaldehyde and campholenic aldehyde using a XAD‑4/DNPH denuder, and the quantification error was also reduced. This sampling technique was then applied to a series of α- and β-pinene ozonolysis experiments. The present study examined the influence of an OH radical scavenger (CO), and hence the HO2/RO2 ratio, on the SOA formation, product distribution and partitioning behaviour of selected oxidation products in conjunction with different seed particle acidities. It was shown that SOA yields increased by about 8% in α-pinene ozonolysis when CO and acidic seed particles co-existed, whereas only a marginal difference was observed (increase of 2%) for β-pinene compared to neutral seed particles. From the denuder/filter sample analysis, it was possible to tentatively identify a new compound from the α-pinene ozonolysis, i.e., terpenylic aldehyde. Gas- and particle-phase yields were estimated for the first time for this compound (i.e., 1% and 0.4%, respectively). The atmospheric relevance of terpenylic aldehyde was demonstrated based on ambient filter measurements and a possible formation pathway was suggested. Furthermore, the present study provided an additional explanation for enhanced SOA formation when acidic seed particles are used in monoterpene ozonolysis. It was demonstrated that the isomerisation of monoterpene oxides on acidic seed particles leads to the formation of highly reactive SOA precursors, whose subsequent reaction with ozone contributes significantly to SOA formation.

Mit der vorliegenden Broschüre werden die Ergebnisse des Sächsischen Landesamtes für Umwelt, Landwirtschaft und Geologie, des Staatsbetriebes Sachsenforst und der Staatlichen Betriebsgesellschaft für Umwelt und Landwirtschaft gemeinsam vorgestellt. Aus mehrjährigen acker- und pflanzenbaulichen sowie forstlichen Untersuchungen liegen umfangreiche Ergebnisse zu Stickstoffdüngung, -aufnahme, -bilanz und -dynamik unter sächsischen Bedingungen vor. Die zusammenfassende Darstellung der Ergebnisse zeigt, dass regelmäßige Auswertungen der in den verschiedenen Messnetzen erhobenen Parameter und Messreihen die Plattform für ein integriertes und ressortübergreifendes Stickstoffmonitoring bilden können. Die Broschüre liefert einen Beitrag zur Bewertung der Stickstoffbelastung und enthält Handlungsempfehlungen für Flächenbewirtschafter sowie für die Verwaltung.

Articular cartilage is a highly specialized, hierarchically organized tissue covering the articular surfaces of diarthrodial joints that absorbs and distributes forces upon mechanical loading and enables low-friction movement between opposing bone ends. Despite a strong resilience towards mechanical stress, once damaged cartilage is generally not regenerated due to a limited repair potential of the residing cells (chondrocytes) and the local absence of vascularized blood vessels and nerves. Eventually, this may lead to osteoarthritis, a chronic degenerative disorder of the synovial joints which has a strongly growing prevalence worldwide. Modern regenerative therapies that aim to rebuild cartilage tissue in vivo and in vitro using chondrocyte- and stem cell-based methods are still not able to produce tissue constructs with desired biomechanical properties and organization for long-term repair. Therefore, cartilage tissue engineering seeks for new ways to solve these problems. In this regard, the application of hydrogel-based scaffolding materials as artificial matrix environments to support the chondrogenesis of embedded cells and the implementation of appropriate biofabrication techniques that help to reconstitute the zonal structure of articular cartilage are considered as promising strategies for sophisticated cartilage regeneration approaches. In this thesis, a modular starPEG-heparin hydrogel platform as cell-instructive hydrogel scaffold was used in combination with a custom-designed 3D inkjet bioprinting method with the intention to develop a printable 3D in vitro culture system that promotes the chondrogenic differentiation of human mesenchymal stromal cells (hMSC) in printed cell-laden hydrogels with layered architectures in order to fabricate cartilage-like tissue constructs with hierarchical organization. Firstly, the successful bioprinting of horizontally and vertically structured, cell-free and -laden hydrogel scaffolds that exhibit layer thicknesses in the range of the superficial zone, the thinnest articular cartilage layer is demonstrated. The long-term integrity of the printed constructs and the cellular functionality of the plotted cells that generally had a high viability after the printing process are shown by a successful PDGF-BB-mediated hMSC migration assay in a printed multilayered hydrogel construct over a culture period of 4 weeks. Secondly, when the established printing procedures were applied for the chondrogenic differentiation of hMSCs, it was found that the printed cell-laden constructs showed a limited potential for in vitro chondrogenesis as indicated by a weaker immunostaining for cartilage-specific markers compared to casted hydrogel controls. In order to increase the post-printing cell density to tackle the limited printable cell concentration which was regarded as the primary reason for the impaired performance of the printed scaffolds, different conditions with varying culture medium and hydrogel compositions were tested to stimulate 3D cell proliferation. However, a significant 3D cell number increase could not be achieved which ultimately resulted in shifting the further focus to casted hMSC-laden starPEG-heparin hydrogels. Thirdly, the chondrogenic differentiation of hMSCs in casted hydrogels proved to be successful which was indicated by a uniform deposition of cartilage-specific ECM molecules comparable with the outcomes of scaffold-free MSC micromass cultures used as reference system. However, the quantitative analysis of biochemical and physical properties of the engineered hydrogel constructs yielded still significant lower values in relation to native articular cartilage tissue. Fourthly, in order to improve these properties and to enhance the chondrogenesis in starPEGheparin hydrogels, a dualistic strategy was followed. In the first part, specific externally supplied stimulatory cues including a triple growth factor supply strategy and macromolecular crowding were applied. As second part, intrinsic properties of the modular hydrogel system such as the crosslinking degree, the enzymatic degradability and the heparin content were systematically and independently altered. It was found that while the external cues showed no supportive benefits for the chondrogenic differentiation, the reduction of the heparin content in the hydrogel proved to be a key trigger that resulted in a significantly increased cartilage-like ECM deposition and gel stiffness of engineered constructs with low and no heparin content. In conclusion, this work yielded important experiences with regards to the application of inkjet bioprinting for hMSC-based cartilage tissue engineering approaches. Furthermore, the obtained data provided valuable insights into the interaction of MSCs and a surrounding hydrogel-based microenvironment that can be used for the further development of chondrosupportive scaffolding materials which may facilitate the fabrication of cartilage-like tissue constructs.

Es werden die Entdeckung der organischen Szintillatoren durch Hartmut Kallmann und seine anderen Arbeiten, insbesondere die Entwicklung der flüssigen Szillitatoren beschrieben. / The discovery of organic scintillators by Hartmut Kallmann and his further work, especially the development of liquid scintillators are described.

Es wird die Geschichte der Arbeitsgemeinschaft Radiochemische Analysenmethoden in der Chemischen Gesellschaft der DDR beschrieben. / The History of the working-pool Radioanalytical Chemistry of the Chemical Society of the GDR is described.

In dem Bericht werden Strahlungsquelle aufgeführt, die den Untergrund bei der Messung geringer Radioaktivitäten verursachen und dargestellt wie zur Unterdrückung der kosmischen Strahlung Laboratorien untertägig eingerichtet werden und wie durch Koinzidenz und Antikoinzidenzverfahren der verbleibende Untergrund weiter reduziert werden kann. / The radiation sources are described, which causes the background at the measurement of low radioactivities. To reduce the influence of cosmic rays counting devises are installed in underground laboratories. The remaining background may be further reduced by coincidence and anti-coincidence methods.

Vor 200 Jahren fiel ein Meteorit in der Nähe von Erxleben, der von den drei deutschen Chemikern Stromeyer, Klaproth und Bucholz analysiert wurde. Aus diesem Anlass wird eine Übersicht der chemischen Analyse von Meteoriten beginnend mit den ersten Untersuchungen gegeben. In jenen Jahren wurden die Hauptkomponenten bestimmt. In den meisten Steinmeteoriten fand man sehr ähnliche Gehalte der Hauptbestandteile, charakteristische Körner aus Eisen und Eisensulfid in einer mineralischen Grundmasse aus Bittererde und Kieselerde genannten Oxiden von Magnesium und Silicium. Man fand in den Eisenmeteoriten und den metallischen Körnern der Steinmeteoriten hohe Gehalte an Nickel, wie sie nicht in natürlichen irdischen Materialien vorkommen. Der britische Chemiker Howard und Klaproth waren die ersten, die Chladnis Theorie akzeptierten, dass die Meteoriten aus dem Kosmos stammen / 200 years ago a meteorite was fallen near Erxleben between Magdeburg und Helmstedt, which was analyzed by the three German Chemist Stromeyer, Klaproth and Bucholz. For this reason a survey of chemical analysis of meteorites from the first investigation in 1769 until 1820 is given. In this period the contents of main components were determined and were found to be similar for most of the stony meteorites, which contains characteristic grains of iron and iron sulfide in a mineral matrix of oxides of magnesium and silicon in German named “Bittererde” and “Kieselerde”. The metal in iron meteorites and in the metallic grains of stony meteorites contain a high content of nickel, which was not found in natural iron on the earth. The British Chemist Howard and Klaproth were the first, who accepted the Theory of Chladni, that the meteorites have been fallen from the sky.