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We report on seven nights of optical observation taken over a two-week period, and the resultant analysis of the intermediate-frequency peaked BL Lac object (IBL), BL Lac itself, at redshift z = 0.069. The microvariable behavior can be confirmed over the course of minutes for each night. A relativistic beaming model was used in our analysis, to infer changes to the line of sight angles for the motion of the different relativistic components. This model has very few free parameters. The light curves we generated show both high and moderate frequency cadence to the variable behavior of BL Lac itself, in addition to the well documented long-term variability.

We report a morphological transition in the magnetic domain pattern exhibited by perpendicular anisotropy ferromagnetic ${[\mathrm{Co}/\mathrm{Pt}]}_{50}$ multilayer films at room temperature and remanence. We found that the remanent magnetic domain morphology and the associated domain density, defined as the number of domains of a given magnetization direction per area, strongly depend on the magnetic history. When the magnitude of the previously applied external field approaches a specific value, typically 75--95% of the saturation field, the magnetic pattern, which generally forms a maze of interconnected stripe domains, decays into a shorter stripe pattern, and the domain density increases. We mapped out this morphological transition as a function of the previously applied field magnitude as well as the Co thickness. We found that a Co thickness close to 30 \AA{} yields the highest domain density with the formation of a pure bubble domain state. Three-dimensional micromagnetic simulations confirm the formation of a pure bubble state in that parameter region and allow an estimation of the perpendicular anisotropy (here $2\ifmmode\times\else\texttimes\fi{}{10}^{5}\phantom{\rule{0.16em}{0ex}}\mathrm{J}/{\mathrm{m}}^{3}$ for an input magnetization of 1080 kA/m), as well as the interpretation of distinct features of the samples' hysteresis loop based on the corresponding domain pattern.