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Microscopy images of birefringent samples are obtained by means of polarization microscopy, In combination with Differential Interference Contrast (DIC). A photo of the combination of the electrical cell and the microscope is given in Fig.8. An Inverted Axiovert 40CFL Zeiss microscope is used. A program has been developed where pixel-averaged dynamic correlation functions of dynamical states can be measured. For fd-suspensions, for example, a dynamical state is found in a particular range of frequencies and field amplitudes, where nematic domains melt and reform, a snap shot of which is given in Fig.9a. The dynamics of this state can be characterized by pixel-time correlation functions as measured from time-resolved microscopy images and the newly developed program. A few of the correlation functions for this case are given in Fig.9b, for several applied field strengths at a fixed frequency, together with fits to a stretched exponential function. A transmitted intensity trace for a single pixel is shown in Fig.9c.Typical field of views are a few hundreds of microns, with a resolution of about 5 micron.


Kang_Bild6_jpgFig.8: A photo of the microscope with the mounted electrical cell (encircled in red).

Kang_Bild8_jpgFig.9: (a) A snap shot of the dynamical state of melting and reforming nematic domains. (b) A transmitted intensity trace for a given crystal. (c) Image-time correlation functions for several field amplitudes (as indicated in the figure) at a fixed frequency, together with fits to a stretched exponential.

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( K. Kang )