ChromoGenics (Sweden)

Polymer electrolytes containing polyethyleneimine and different concentrations of lithium bis(trifluoromethylsulfonyl) imide were investigated by impedance spectroscopy at different temperatures. Two equivalent circuit models were compared for the bulk impedance response. The first one includes a conductive Havriliak–Negami (HN) element which represents ionic conductivity and ion pair relaxation in a single process, and the second model includes a dielectric HN element, which represents ion pair relaxation, in parallel with ion conductivity. Comparison of the two circuit models showed that the quality of the fit was similar and in some cases better for the conductive model. The experimental data follow the Barton–Nakajima–Namikawa relation, which relates the ion conductivity and the parameters of the relaxation. This indicates that ion conductivity and ion pair relaxation are two parts of the same process and should be described by the conductive model.

1/f noise was observed in electrochromic (EC) devices capable of modulating their opticaltransmittance by an applied voltage. The device comprised nanoporous W oxide and Ni–Voxide films and an intervening polymer electrolyte between transparent conductingIn2O3:Sn films backed bypolyester foils. Current (I) 1/f noisewas observed when the charged (colored) device was discharged via a resistor. The power spectral densitySi at fixed frequencyvaried as Si∼I2. Continuous coloration/bleaching degraded the optical quality andhomogeneity of the device and led to a concomitant increase of the1/f noise intensity,thus indicating that 1/f noise has the potential to serve as a quality measure for EC devices.

This study was aimed at evaluating the performance of a chromogenic factor VIII assay on STA, an automated coagulation analyzer. Additionally, a correlation study was conducted with an aPTT-based one-stage factor VIII clotting assay. Throughout the study the performance of the chromogenic assay was tested in two ranges of factor VIII activity: a high range with activity between 20% and 150% and a low range with activity below 20%. Inter-assay coefficient of variation ranged from 1.9% to 8.9% and intra-assay coefficient of variation from 0.5% to 11.4%, depending on factor VIII concentration. Day-to-day reproducibility was tested over a 5-day period; between-day imprecision ranged from 7.1% to 9.4%. The chromogenic factor VIII assay showed a good correlation with the clotting assay in both ranges. The correlation coefficients were 0.924 and 0.792 for the high and low range, respectively. A statistically significant difference in mean values was observed in the high range (p<0.0001). Comparison between the chromogenic assay on STA versus on microplates showed a high correlation (0.991), which was highly significant (p<0.0001). In conclusion, the chromogenic assay for factor VIII on STA shows good analytical performance. It correlates well with the one-stage factor VIII clotting assay, although significant differences between individual samples occur. Probably these are partly related to differences in measurement principle and standardization. Altogether, this precise and rapid assay is suitable for determination of factor VIII by an automated procedure.