The electrical modulus and other dielectric properties by the impedance spectroscopy of LaCrO3 and LaCr0.90Ir0.10O3 perovskites.

We have prepared LaCrO3 (LCO) and 10% Ir doped LCO samples by the solid state reaction method and studied the electrical modulus and the other dielectric properties of the samples by means of the impedance spectroscopy in the -100 °C to 100 °C range, with steps of 20 °C. It has been clearly observed that the dielectric properties change due to Ir doping. The absolute dielectric constant value of Ir doped LCO has decreased and this reduction was attributed to decreasing Cr6+ ions which may play a vital role in space charge polarization and charge hopping. A plateau region appeared in the temperature-dependent real electrical modulus M' versus f curves of the pure LCO sample while almost no plateau region is visible in the Ir doped LCO sample. The temperature-dependent imaginary modulus M'' versus f curves has two peaks at each temperature; one of the peaks is at low frequency and the other at the high frequency region, which shifts through higher frequency region with increasing temperature. This originates from free charge accumulation at the interface with the increase of the temperature. Furthermore, it has been seen that the Ir doped LCO sample has higher impedance and resistance values than the undoped LCO sample at the same frequency and temperature. This phenomenon was attributed to doped Ir ions behaving like a donor in LCO because LCO is a p-type compound. Moreover, the activation energy values of 0.224 eV and 0.208 eV for LCO and of 0.161 eV and 0.265 eV for the Ir doped LCO have been obtained from the slopes of the ρ dc vs. (kT)-1 curves, respectively. Also the activation energies were calculated from the slopes of the f max vs. (kT)-1 curves and the obtained results from low frequency region were in good agreement with ρ dc vs. (kT)-1 ones.

Electrochemical behaviour of 3,8-difluorobenzo[c]cinnoline at mercury electrode.

Voltametric and coulometric methods have been used to study the electroanalytical behaviour of 3,8-difluorobenzo[c]cinnoline. The number of electrons transferred, the wave characteristics, diffusion coefficient and reversibility of the reactions have been investigated in ethyl alcohol-BR. Adsorption of the molecule on the surface of the mercury drop electrode was analyzed and this phenomena was exploited to calculate the diffusion coefficient of 3,8-difluorobenzo[c]cinnoline. A mechanism for the electrode reaction was proposed.

Aspects of pre-eclamptic toxaemia of pregnancy, consanguinity, twinning in Ankara.

It appears that women classed as having pre-eclamptic toxaemia are less frequently consanguineous with their husbands than all other mothers and in particular those mothers classed as having pregnancies complicated by chronic hypertensive disease. Search revealed no evidence for possible biases which could have stimulated such findings. Further evidence is advanced suggesting that, though pre-eclamptic toxaemia is more common in all types of twin pregnancies than in single births, it is more common where the twins are dizygous than where they are monozygous. It is pointed out that both these findings would be expected if there was a contribution to the aetiology of pre-eclamptic toxaemia by maternal/fetal immunological incompatibility. However, if such a mechanism exists it is not always determined at the same gene locus.