Influence of laser read and bias power levels on the performance of thermomagnetooptic recording media.

Read and bias power levels are capable of noticeably altering the response of thermomagnetooptic recording materials. The heating caused by the read power can decrease signal levels due to the temperature dependence of the polar Kerr rotation. Preheating caused by bias power levels also influences media sensitivity and responses during the writing process. Increased bias levels reduce the optimum recording power and increase the severity of mark length variations caused by write power fluctuations. Simple predictive expressions were derived to describe the influence of bias and read power levels during the mark formation and readout processes. The predicted results were in good qualitative and quantitative agreement with experimental observations.

Dependence of maximum readout power on various properties of thin-film magnetooptic media.

In magnetooptic recording it is desirable that the read laser power be as large as possible without causing degradation of the recorded information. We have developed a test that efficiently simulates the repeated reading of the recorded magnetic domains. This technique is used to determine the maximum read power and minimum write power of a variety of magnetooptic materials on a variety of substrates. We report the correlation between maximum read power, coercivity of the sample, and thermal properties of the substrate.

Protein conformation from electron spin relaxation data.

Electron spin relaxation data from five ferric proteins are analyzed in terms of the fractal model of protein structures. Details of this model are presented. The results lead to a characterization of protein structures by a single parameter, the fractal dimension, d. This structural parameter is shown to determine the temperature dependence of the Raman electron spin relaxation rate, which varies as T3 + 2d. Computations of d are made using x-ray data for 17 proteins. The results range from d = 1.76 for lysozyme to d = 1.34 for ferredoxin. These values are compared with values of d obtained from the present electron spin relaxation data on five ferric proteins. Typical results are d = 1.34 +/- 0.06 from relaxation data and 1.34 +/- 0.05 from x-ray data for ferredoxin; d = 1.67 +/- 0.03 from relaxation data and 1.66 +/- 0.05 from x-ray data for ferricytochrome c. The data thus support the theoretical model. Applications of this spin resonance technique to the study of changes in protein conformation are discussed.