Electrochemical impedance spectroscopy of proton exchange membrane fuel cell stacks

Electrochemical Impedance Spectroscopy (EIS) is applied to a small, four cell Proton Exchange Membrane (PEM) fuel cell stack to examine the stack response as the load current changes. The measured stack response is compared to a simulated response generated by a stack model that has been developed using MATLAB. The results show that the model predicted well the behavior of the VI curve for currents less than 50 Amps. The model also qualitatively predicted the impedance response as a function of current and frequency. Because of apparent model incompleteness, it was not able to predict accurately the shape of the response in the complex plane at currents larger than 20 Amps and did not match the change in ohmic resistance with current

Further Studies on Selection for Resistance to Salmonella aertrycke in Mice

It was demonstrated by Schott in 1932 that selection for resistance in mice to a standard dose of 5 x 104 S. aertrycke bacteria was effective in decreasing the mortality from 82.3 per cent for the unselected foundation stock to 24.7 per cent in the sixth selected generation. Using the same material as the basis for further study, the complete results for the sixth generation gave a mortality of 22.5 per cent. Further decreases in mortality to 14.7 and 15.6 per cent were observed in the seventh and eighth generations respectively. Groups of mice belonging to the eighth generation when tested with a dose of 2 x 105 organisms gave a mortality of 25.4 per cent. With the 2 x 105 dose the mortalities decreased to 15.8 and 16.2 per cent in the tenth and eleventh generations respectively. Similar sets of mice belonging to the tenth and eleventh generations when tested with a dose of 2 x 106 bacteria gave mortalities of 32.4 and 23.3 per cent respectively. With a dose of 1 x 107 organisms the mortality rose to 40.3 per cent in the eleventh generation. A mortality of 47.2 per cent was observed in the twelfth generation with the dose 1 x 107

Inheritance of Resistance and Susceptibility to Salmonella aertrycke in Mice

In previous reports by the writer and others it has been shown that the resistance of a strain of mice to controlled infections of Salmonella acrtrycke could be greatly increased by selective breeding. After fourteen generations of selection for resistance to a standard close of 2 x 105 organisms the mortality in the selected stock (S) was only 8 per cent as compared with a mortality of approximately 98 per cent in the highly susceptible Silver (Sil) and Bagg albino (Ba) strains

Martin Hetzer: Taking the nuclear membrane beyond the barrier

Hetzer investigates how the nuclear envelope and nuclear pores organize chromatin and regulate gene expression