In order to observe the effect of atomic resonant scattering on X-ray topography, topographs of a GaAs crystal with the 200 reflection have been taken using synchrotron X-rays with energy near the K-absorption edges of Ga and As. The X-ray energy has been tuned to four typical resonant scattering conditions. It is shown that the contrast of lattice defects observed in topographs changes with the resonant scattering conditions. Such topography taken under resonant scattering is useful for studying lattice defects in crystals.

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6-Arylidene-2-furfurylidenecyclohexanones were obtained by the condensation of cyclohexanone with aldehydes of the aromatic and furan series under conditions of base or acid catalysis. The effect of substituents in the aromatic ring on the activity of the initial aldehyde was studied. According to data from the IR spectra, the obtained ketones exist in the form of trans,trans isomers. Diarylidene(dihetarylidene)cyclanones have various types of biological activity [1], are pesticides [2], and are used in organic synthesis for the construction of practically important heterocyclic compounds [3]. The possibility of using compounds of this type as antioxidant additives [2] and as components of rocket fuel [4] has been reported. New polymers based on furfurylidenecyclohexanones are stable and resistant to the action of laser radiation [5].The literature contains fairly comprehensive data on the synthesis and properties of symmetrical diarylidene-and difurfurylidenecyclohexanones (see, for example, [6]). The amount of information on unsymmetrical arylidenecyclohexanones is significantly smaller [7]. Furfurylidenearylidenecyclohexanones have hardly been studied at all.In the present work we describe the synthesis of previously unknown 6-arylidene-2-furfurylidenecyclohexanones 1a-h and discuss their stereochemistry. The ketones 1a-g were obtained by crotonic condensation of 2-furfurylidenecyclohexanone (2) with aromatic aldehydes 3a-g in solution in isopropyl alcohol under conditions of base catalysis (an aqueous solution of sodium hydroxide) at room temperature. O O R O O O H OH R + _ 2 3a-g 1a-g 1, 3 a R = H; b R = 4-OМе; c R = 4-NМе 2 ; d R = 4-Br; e R = 3-NO 2 ; f R = 2-Cl; g R = 2-F