Combining electrochemical and quantitative elemental analysis to investigate the sulfur poisoning process of ceria thin film fuel electrodes.

This work deals with the effect of sulfur incorporation into model-type GDC thin films on their in-plane ionic conductivity. By means of impedance measurements, a strongly deteriorating effect on the grain boundary conductivity was confirmed, which additionally depends on the applied electrochemical polarisation. To quantify the total amount of sulfur incorporated into GDC thin films, online-laser ablation of solids in liquid (online-LASIL) was used as a novel solid sampling strategy. Online-LASIL combines several advantages of conventional sample introduction systems and enables the detection of S as a minor component in a very limited sample system (in the present case 35 µg total sample mass). To reach the requested sensitivity for S detection using an inductively coupled plasma-mass spectrometer (ICP-MS), the reaction cell of the quadrupole instrument was used and the parameters for the mass shift reaction with O2 were optimised. The combination of electrical and quantitative analytical results allows the identification of a potential sulfur incorporation pathway, which very likely proceeds along GDC grain boundaries with oxysulfide formation as the main driver of ion transport degradation. Depending on the applied cathodic bias, the measured amount of sulfur would be equivalent to 1-4 lattice constants of GDC transformed into an oxysulfide phase at the material's grain boundaries.

A novel approach for analyzing electrochemical properties of mixed conducting solid oxide fuel cell anode materials by impedance spectroscopy.

For application of acceptor-doped mixed conducting oxides as solid oxide fuel cell (SOFC) anodes, high electrochemical surface activity as well as acceptable electronic and ionic conductivity are crucial. In a reducing atmosphere, particularly the electronic conductivity of acceptor-doped oxides can become rather low and the resulting complex interplay of electrochemical reactions and charge transport processes makes a mechanistic interpretation of impedance measurements very complicated. In order to determine all relevant resistive and capacitive contributions of mixed conducting electrodes in a reducing atmosphere, a novel electrode design and impedance-based analysis technique is therefore introduced. Two interdigitating metallic current collectors are placed in a microelectrode, which allows in-plane measurements within the electrode as well as electrochemical measurements versus a counter electrode. Equivalent circuit models for quantifying the spectra of both measurement modes are developed and applied to simultaneously fit both spectra, using the same parameter set. In this manner, the electronic and ionic conductivity of the material as well as the area-specific resistance of the surface reaction and the chemical capacitance can be determined on a single microelectrode in a H2-H2O atmosphere. The applicability of this new tool was demonstrated in SrTi0.7Fe0.3O(3-δ) (STFO) thin film microelectrodes, deposited on single-crystalline yttria-stabilized zirconia (YSZ) substrates. All materials parameters that contribute to the polarization resistance of STFO electrodes in a reducing atmosphere could thus be quantified.

[Variability of quantitative DNA parameters in endometrial carcinoma]. / Untersuchungen zur Variabilität von quantitativen DNA-Parametern in Endometriumkarzinomen.

We performed image analysis examinations of 20 cases of endometrial carcinoma and the compared quantitative DNA parameters within each carcinoma. Specimens were taken from each carcinoma, at standardised, pre-defined sites. Six smear preparations were made from each case and DNA parameters were determined after Feulgen staining. 17 of the 20 cases of endometrial carcinoma (85%) showed in all the examined preparations a uniform diploid or aneuploid (n = 1) DNA distribution. Only 3 carcinomas showed diploid as well as non-diploid DNA distributions. For each carcinoma the mean values of DNA-MG were found to be between 0.37 +/- 0.12 and 2.16 +/- 0.11 and those of the 5cER between 0.91 +/- 0.78 and 15.37 +/- 4.17. Relationships were shown between DNA distribution, DNA-MG, 5cER and morphological prognostic factors while a reliable diagnostic of dignity based on DNA distribution and 5cER as a marker of single cell ploidy seems not possible. With an increase in DNA-MG, the coefficient of variation of this parameter decreased within the individual cases. Concluding, quantitative DNA parameters, owing to their relatively small variability within specific cases of endometrial carcinomas seem to be suitable objective indicators of prognosis to plan a risk-adapted therapy.

The relation between the results of cytophotometric examination of endometrial carcinoma and clinical course of these disease.

We made a prospective cytophotometric study of 48 cases of endometrial carcinoma. Thirty-two (66.7%) of the cases had diploid DNA content and the proportion of non-diploid tumors increased with the staging of tumors, lack of differentiation and depth of myometrial invasion. DNA content (AE), DNA malignancy grade (DNA-MG) and 5c exceeding rate were statistically significant in relation to the clinical course of the disease and the histological grade of differentiation. DNA parameters appear to be especially suitable for the objective assessment of malignancy.