Dielectric relaxation, the superposition principle, and age-dependent transition rates

1992 ◽  
Vol 25 (10) ◽  
pp. 1533-1537 ◽  
Author(s):  
V Halpern
1961 ◽  
Vol 39 (3) ◽  
pp. 571-594 ◽  
Author(s):  
D. W. Davidson

Methods are described for the determination from experimental data of the parameters used in the skewed-arc representation in the complex dielectric constant plane of dielectric relaxation in liquids. Graphs give the frequency dependence of the real and imaginary parts of the dielectric constant predicted by the skewed-arc equation. Evidence, which includes an analysis of published data and of some new data, is presented for the frequent occurrence of this type of relaxation behavior in liquids. The resolution of the effects of different relaxation processes is discussed.The recent defect-diffusion model of Glarum is found to lead, under some conditions, to complex dielectric constant loci which are practically indistinguishable from skewed-arc loci over much of the frequency range of dispersion. It predicts departures from skewed-arc behavior at relatively high frequencies which are possibly related to experimentally observed departures.It is concluded that skewed-arc characteristics arise from the presence of co-operative relaxation processes, possibly aided by the diffusion of disordered regions, in which the individual mechanisms of relaxation cannot be resolved by application of the superposition principle.


Author(s):  
Gladys Harrison

With the advent of the space age and the need to determine the requirements for a space cabin atmosphere, oxygen effects came into increased importance, even though these effects have been the subject of continuous research for many years. In fact, Priestly initiated oxygen research when in 1775 he published his results of isolating oxygen and described the effects of breathing it on himself and two mice, the only creatures to have had the “privilege” of breathing this “pure air”.Early studies had demonstrated the central nervous system effects at pressures above one atmosphere. Light microscopy revealed extensive damage to the lungs at one atmosphere. These changes which included perivascular and peribronchial edema, focal hemorrhage, rupture of the alveolar septa, and widespread edema, resulted in death of the animal in less than one week. The severity of the symptoms differed between species and was age dependent, with young animals being more resistant.


2007 ◽  
Vol 177 (4S) ◽  
pp. 411-412
Author(s):  
Javier Miller ◽  
Angela Smith ◽  
Kris Gunn ◽  
Erik Kouba ◽  
Eric M. Wallen ◽  
...  

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