Application of wavelet filtering techniques to Lau interferometric fringe analysis for measurement of small tilt angles

This communication presents the results of investigation undertaken towards testing the viability of wavelet filtering techniques in analyzing the Lau interferometric fringes. Towards this, the applicability of Haar, Daubechies and Symlet wavelet based filtering schemes have been tested. Of these schemes, the Symlet based filtering scheme gives the best results in terms of improved signal to noise ratio. This scheme is then used to analyze Lau interferograms recorded in the experimental arrangement for tilt angle measurement. The processed interferograms yield improved accuracy and precision of measurement.     

Unexpected 5,6,7,8,9,10-hexahydro-6,6-pentamethylenephenanthridines and 2,3,4,5-tetrahydro-4,4-tetramethylene-1H-cyclopenta[c]quinolines from Skraup-Doebner-Von Miller quinoline synthesis and their implications for the mechanism of that reaction

The real mechanism of the Skraup-Doebner-Von Miller quinoline synthesis remains controversial and not well understood despite several mechanistic studies reported on the matter. A series of unexpected and unusual 5,6,7,8,9,10-hexahydro-6,6-pentamethylenephenanthridines and 2,3,4,5-tetrahydro-4,4-tetramethylene-1H-cyclopenta[c]quinolines have been obtained through the Skraup-Doebner-Von Miller quinoline synthesis. On the basis of these unexpected results and in agreement with some of the previously reported quinoline syntheses, an alternative mechanistic pathway is proposed for this variant of the reaction. It involves the formation of a Schiff base through a reaction between the ketone and the aniline derivative in the first step, followed by a cycloalkenylation at the ortho-position to the amine functional group of the aniline derivative, and an annulation in the final step to close the quinoline ring, leading to a dihydroquinoline derivative. To the best of our knowledge, this is the first report of such a mechanistic pathway being proposed for any variant of the Skraup-Doebner-Von Miller quinoline synthesis.