High temperature and pressure electrochemical test station.

An electrochemical test station capable of operating at pressures up to 100 bars and temperatures up to 400 °C has been established. It enables control of the partial pressures and mass flow of O2, N2, H2, CO2, and H2O in a single or dual environment arrangement, measurements with highly corrosive media, as well as localized sampling of gas evolved at the electrodes for gas analysis. A number of safety and engineering design challenges have been addressed. Furthermore, we present a series of electrochemical cell holders that have been constructed in order to accommodate different types of cells and facilitate different types of electrochemical measurements. Selected examples of materials and electrochemical cells examined in the test station are provided, ranging from the evaluation of the ionic conductivity of liquid electrolytic solutions immobilized in mesoporous ceramic structures, to the electrochemical characterization of high temperature and pressure alkaline electrolysis cells and the use of pseudo-reference electrodes for the separation of each electrode contribution. A future perspective of various electrochemical processes and devices that can be developed with the use of the established test station is provided.

Electronic conductivity of Ce0.9Gd0.1O(1.95-δ) and Ce0.8Pr0.2O(2-δ): Hebb-Wagner polarisation in the case of redox active dopants and interference.

The electronic conductivity of Ce(0.9)Gd(0.1)O(1.95-δ) and Ce(0.8)Pr(0.2)O(2-δ) under suppressed ionic flow was measured as a function of pO(2) in the range from 10(3) atm to 10(-17) atm for temperatures between 600 °C and 900 °C by means of Hebb-Wagner polarisation. The steady state I-V curve of Ce(0.9)Gd(0.1)O(1.95-δ) could be well described by the standard Hebb-Wagner equation [M. H. Hebb, J. Chem. Phys., 1952, 20, 185; C. Wagner, Z. Elektrochem., 1956, 60, 4], yielding expressions for the n- and p-type conductivity as a function of pO(2). On the other hand, significant deviation of the steady state I-V curve from the standard Hebb-Wagner equation was observed for the case of Ce(0.8)Pr(0.2)O(2-δ). It is shown that the I-V curve can be successfully reproduced when the presence of the redox active dopant, Pr(3+)/Pr(4+), is taken into account, whereas even better agreement can be reached when further taking into account the interference between the ionic and electronic flows [C. Chatzichristodoulou, W.-S. Park, H.-S. Kim, P. V. Hendriksen and H.-I. Yoo, Phys. Chem. Chem. Phys., 2010, 12, 33]. Expressions are deduced for the small polaron mobilities in the Ce 4f and Pr 4f bands of Ce(0.8)Pr(0.2)O(2-δ).

Rickettsia conorii in Greece: comparison of a microimmunofluorescence assay and western blotting for seroepidemiology.

Since 1972, there have been no reports of Mediterranean spotted fever (MSF) in Greece. In 1991, a seroepidemiologic survey was conducted in three rural villages in the Province of Fokida in central Greece, using both an immunofluorescence assay (IFA) and Western blot to evaluate the prevalence of specific IgG and IgM antibodies to Rickettsia conorii, and to compare these two techniques. Of 254 sera tested by IFA, 148 (58.3%) were positive for IgG at a titer > or = 32 and 117 (46.1%) at a titer > or = 64. Two sera were positive for IgM at a titer > or = 32. Among the IFA-positive sera, 115 reacted against the specific protein antigen (SPA) using Western blotting and were considered as confirmed positive results, indicating a seroprevalence of 45.3%. Using the SPA reaction as a reference, the IFA diagnostic value of a single serum is poor in such an endemic area, suggesting the need for more specific tests. The results of this study have led us to conclude that for seroepidemiologic use, the IFA is not specific for MSF. Thus, the IFA is useful for sero-epidemiologic analysis only in areas where the true prevalence of MSF has been estimated using Western blotting.