SCHWEFELVERBINDUNGEN DES ERDÖLS XVI.1 DIBENZOTHIOPHENE MIT EINEM UNVERZWEIGTEN C1[sbnd]C5-ALKYLREST

Abstract

The preparation of all position isomeres of dibenzothiophenes with a linear C₁[sbnd]C₅-sidechain and of the corresponding 5,5-dioxides is described. ¹H-NMR-data and GC-purities are given.

Die Darstellung von allen stellungsisomeren Dibenzothiophenen mit einer unverzweigten C₁[sbnd]C₅-Seitenkette und der zugehörigen 5,5-Dioxide wird beschrieben. ¹H-NMR-Daten und GC-Reinheiten werden gebracht.     

Kinetic Modeling as a Tool to Understand and Improve the Nitroxide Mediated Polymerization of Styrene

Kinetic modeling is used to obtain insight in the complex interplay between reaction rates and obtained polymer properties in the SG1 and the TEMPO mediated bulk polymerization of styrene at 396 K. The increase of the viscosity during NMP is accounted for. At higher targeted chain lengths, chain transfer to dimer and transfer from nitroxide to dimer are shown to cause the experimentally observed reduced control over the average polymer properties and to result in a clear fronting of the polymer chain length distribution. The potential of kinetic modeling to design tailor‐made synthesis strategies is illustrated. Simulations indicate that careful control of the polymerization conditions allows to obtain an important improvement of the polymer properties. The approach is also applicable for NMP mediated by other alkoxyamines/nitroxides and allows to expand the application range of NMP for styrene polymerization in particular to synthesize complex polymer architectures by assembly of functionalized polymers.

     

On the influence of strain on ion transport: microstructure and ionic conductivity of nanoscale YSZ|Sc2O3 multilayers

Multilayer samples of the type (YSZ|Sc2O3) × n with layer thicknesses between 8 nm (n=100) and 250 nm (n=5) were prepared on (0001) sapphire substrates by pulsed laser deposition (PLD). The samples were characterised using X-ray diffraction (XRD), scanning electron microscopy (HRSEM) and transmission electron microscopy (TEM/HRTEM, SAED (selected-area electron diffraction) and quantitative EELS (electron energy-loss spectroscopy)). The polycrystalline layers show a columnar microstructure, which is typical for the used preparation technique. The layers are highly textured and only one axial orientation relation is found between yttria-stabilised zirconia (YSZ), scandium oxide and the substrate: (0001) Al2O3‖(111) Sc2O3‖(111) YSZ. A preferred orientation relationship also exists for the azimuthal rotation of the crystallites, which was demonstrated by SAED, XRD pole figure measurements and fast Fourier transformation (FFT) of HRTEM micrographs. The interfaces between YSZ, Sc2O3 and the substrate are sharp and do not contain diffuse transition regions. Dislocations appear not to be arranged in regular arrays. With increasing interface density (thinner individual layers in the multilayer), the conductivity of the multilayers decreases. We relate this to the negative nominal misfit present at the YSZ|Sc2O3 interfaces (compressive stress in YSZ at the phase boundaries). This observation agrees well with the previously investigated case of YSZ|Y2O3 (A. Peters et al., Phys. Chem. Chem. Phys., 2008, 10, 4623), where tensile misfit strain was present in YSZ at the phase boundaries, leading to a conductivity increase.     

Multi-elemental bio-imaging of rat tissue from a study investigating the bioavailability of bismuth from shotgun pellets

In recent years, bismuth has been promoted as a "green element" and is used as a substitute for the toxic lead in ammunition and other applications. However, the bioavailability and toxicity of bismuth is still not very well described. Following a hunting accident with bismuth-containing shots, a bioavailability study of bismuth from metal pellets inoculated into rat limb muscles was carried out. Bismuth could be found in urine and blood of the animals. Bio-imaging using laser ablation ICP-MS of thin sections of the tissue around the metal implant was carried out to find out more about the distribution of the metal diffusing into the tissue. Two laser ablation systems with different ablation cell designs were compared regarding their analytical performance. Low concentrations of bismuth showing a non-symmetrical pattern were detected in the tissue surrounding the metal implant. This was partly an artefact from cutting the thin sections but also bio-mobilisation of the metals of the implant could be seen. An accumulation of zinc around the implant was interpreted as a marker of inflammation. Challenges regarding sample preparation for laser ablation and bio-imaging of samples of diverse composition became apparent during the analysis.     

Microanalytical isotope ratio measurements and elemental mapping using laser ablation ICP-MS for tissue thin sections: zinc tracer studies in rats

The kinetics of zinc absorption, metabolism and excretion is extensively studied by nutritionists. Stable isotopes of zinc can be used to identify body zinc compartments that have different turnover kinetics. Since the compartments might belong to physiological subsections of different organs, there is a need for microsampling analysis to determine isotope ratios of the trace element zinc in tissue samples. Here, we study the feasibility to use laser ablation coupled to quadrupole ICP-MS for the determination of zinc tracers given to rats at different time points with the aim to generate isotope ratio bioimages of heart tissue. A double tracer (⁷⁰Zn and ⁶⁷Zn) experiment with rats was designed to label the exchangeable zinc pool as well as the stable zinc pool. The isotope ratios determined by laser ablation ICP-MS were evaluated by additional measurements of tissue digests. Accumulated tracers which made up more than 0.1% of total zinc could be identified in the tissues of the treated rats. It was established that at least 50 measurements from the microsampling were necessary to distinguish between controls and a tracer treated rat resulting in reduced resolution of the bioimage. With the parameters used, features in the tissue thin sections of at least 250 μm² in size are necessary to detect the incorporation of a tracer. When different time points have to be measured, higher precisions are required and therefore a larger area needs to be ablated (1 mm²). Using the bioimages and pool measurements from one physiological feature, it was possible to show that the aorta cell walls incorporate the zinc tracer at the different time points.     

Transmission electron microscopy investigation of AlN growth on Si(111)

AlN layers with a thickness of 250 nm were grown by plasma-assisted gas source molecular-beam epitaxy on Si(111) at substrate temperatures between 600 °C and 900 °C. The surface morphology and microstructure of the AlN layers were analyzed by scanning and transmission electron microscopy. Different defect types are observed in the AlN layers and at the AlN/Si(111) interfaces as a function of the temperature: inclusions of pure Al in the Si-substrate, crystallites of the cubic AlN phase, dislocations, stacking faults and inversion domain boundaries. The formation and concentration of the defects depends strongly on the substrate temperature during the growth. X-ray diffraction rocking curves for the (0002) reflection yield minimum full width at half maximum values for the sample grown at the 900 °C under Al-rich conditions indicating optimum structural quality. However, the discussion of the entity of defects will show that a more differentiated view is required to assess the overall quality of the AlN layers.     

Quantitative high-resolution transmission electron microscopy of single atoms

Single atoms can be considered as the most basic objects for electron microscopy to test the microscope performance and basic concepts for modeling image contrast. In this work high-resolution transmission electron microscopy was applied to image single platinum, molybdenum, and titanium atoms in an aberration-corrected transmission electron microscope. The atoms are deposited on a self-assembled monolayer substrate that induces only negligible contrast. Single-atom contrast simulations were performed on the basis of Weickenmeier-Kohl and Doyle-Turner form factors. Experimental and simulated image intensities are in quantitative agreement on an absolute intensity scale, which is provided by the vacuum image intensity. This demonstrates that direct testing of basic properties such as form factors becomes feasible.     

Development and validation of a liquid chromatography method for the simultaneous determination of alpha-tocopherol, retinol and retinyl esters in human serum using a monolithic column for the monitoring of anticancer therapy side effects

Among other side effects, administration of anticancer agents is accompanied by manifestations of gastrointestinal toxicity and disturbances of antioxidant balance. The monitoring of these toxic effects in clinical practice is impeded by a dearth of reliable laboratory methods. Therefore, a simple and rapid reversed-phase high-performance liquid chromatography procedure for selective and sensitive determination of retinol, a-tocopherol, and retinyl esters (retinyl-palmitate and retinyl-stearate) in blood serum has been developed and presented in this study. A Series 200 LC HPLC instrument from Perkin Elmer (Norwalk, USA) with diode-array detector (DAD) was used for the analysis. Separations of retinol, alpha-tocopherol, retinyl-palmitate, and retinyl-stearate were performed using a Chromolith Performance RP-18e, 100 x 4.6 mm monolithic column from Merck (Darmstadt, Germany). Gradient elution was used at a flow rate of 3 mL/min; the mobile phase was methanol-water (95:5, v/v) for 0-2.1 min and methanol-2-propanol (60:40, v/v) for 2.1-4.9 min. The total time of analysis was 6 min. The injection volume was 20 microL and the analysis was performed at ambient temperature. Detection of retinol, alpha-tocopherol, and retinyl esters was carried out at 325, 295, and 330 nm, respectively. For practical assessment of the method, the vitamin A absorption test was performed on seven healthy controls as well as on six patients with non-small cell lung carcinoma or head and neck carcinoma previously treated by chemotherapy and/or radiotherapy, six patients with rectal carcinoma before chemoradiotherapy, four patients with gastrointestinal stromal tumor (GIST) before treatment with imatinib, and a breast cancer patient with chemotherapy-induced diarrhea. Present data demonstrate the feasibility of large scale HPLC determination of vitamin E, vitamin A, and retinyl esters in human serum using a silica monolithic column, and this method may represent a valuable aid in the laboratory monitoring of the toxicity of anticancer therapy.     

Thermal decomposition study and biological characterization of zinc(II) 2-chlorobenzoate complexes with bioactive ligands

New zinc(II) 2-chlorobenzoates of general formula [Zn(2-ClC₆H₄COO)₂(L)₂] (where L = caffeine—caf, urea—u, methyl-3-pyridylcarbamate—mpc, phenazone—phen, theophylline—thp) were synthesised and characterised by elemental analysis and IR spectroscopy. The thermal behaviour of the complexes was studied by TG/DTG and DTA methods in nitrogen and in air atmosphere. During the thermal decomposition of the studied compounds the release of organic ligands take place followed by the decomposition of 2-chlorobenzoate anion. The volatile decomposition intermediates were proved by mass spectrometry. Zinc oxide was found as the final product of the thermal decomposition performed up to 1,000 K. The antimicrobial activity of the zinc(II) complexes against various strains of bacteria, yeasts and filamentous fungi has been investigated. It was found that the prepared compounds decreased the growth of Staphylococcus aureus, Escherichia coli, Candida albicans, Rhizopus oryzae and Microsporum gypseum, respectively. The most resistant to all tested compounds was probiotic strain of Lactobacillus plantarum. The presence of zinc and ligands in the prepared compounds increased the inhibitory effect compared to sodium salt of prepared compounds and free ligands.