The first cyanine dye, named cyanine because of its blue color, was serendipitously synthesized by C. H. G. Williams as early as 1856. Since the end of the 19th century, the class of cyanine dyes have dominated the field of photography as photosensitizers and are unrivalled even today. The generic cyanine dyes consist of two nitrogen centers, one of which is positively charged and linked to the other center by a conjugated chain of an odd number of carbon atoms (Fig. 1). Symmetrical cyanine dyes commonly contain two benzazole moieties connected by a polymethine chain, whereas the unsymmet-rical cyanines usually consist of a benzazole group and a quinoline or pyridine heterocycle, also connected by a methine bridge. The extensive conjugation and the delocalization of charge lead to long-wavelength absorption maxima and large molar absorptivities. Apart from use as photosensitizers, cyanine dyes have been employed as laser materials, photorefractive materials, antitumor agents, and in optical disks as recording media to name but a few applications.

Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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