A detailed experimental and theoretical study of the linear and nonlinear absorption of a series of asymmetrical D-p-A cyanine dyes with the same trimethylindolin donor (D) and diethylaminocoumarin-dioxaborine acceptor (A) terminal groups and different conjugation lengths, is presented. Strong solvatochromic behavior affecting the fluorescence quantum yields, lifetimes, and the linear and nonlinear absorption properties is observed due to the presence of permanent ground state dipole moments. Detailed experimental studies of lifetime dynamics are performed by direct time-correlated single photon counting and pump-probe techniques. We find that an increase in p-conjugation in the investigated series of dyes leads to an enhancement of the excited-state absorption and two-photon absorption (2PA) cross-sections (d 2PA ). The 2PA spectra for all of the investigated dyes consist of two well-separated bands. The first band occurs at two-photon excitation into the vibrational levels and not into the absorption peak of the main transition, S 0 / S 1 , which is more typical of that observed for symmetrical cyanines. The position of the second 2PA band for all the molecules remains unchanged in solvents of different polarity contrary to the large solvatochromic shift of the S 0 / S 1 band, resulting in a large intermediate state resonance enhancement and, therefore, a larger 2PA in acetronitrile (d 2PA z 10000 GM) compared to toluene (d 2PA z 4700 GM). Experimental methods and results Materials characterization and linear spectroscopic propertiesThe molecular structures of the dyes studied in this paper are shown in the inset of Fig. 1a-c. Their chemical names are:

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A VME -bus image pipeline processor for extracting vectorized contours from grey -level images in real -time is presented. This 3 Giga operation per second processor uses large kernel convolvers and new non -linear neighbourhood processing algorithms to compute true 1 -pixel wide and noise -free contours without thresholding even from grey -level images with quite varying edge sharpness. The local edge orientation is used as an additional cue to compute a list of vectors describing the closed and open contours in real -time and to dump a CAD -like symbolic image description into a symbol memory at pixel clock rate.