Leaky Rayleigh wave investigation on mortar samples

Aggressive mineralized ground water may harm the concrete cover of tunnels and other underground constructions. Within a current research project mortar samples are used to study the effects of sulfate interaction in accelerated laboratory experiments. A nondestructive test method based on ultrasonic surface waves was developed to investigate the topmost layer of mortar samples. A pitch and catch arrangement is introduced for the generation and reception of leaky Rayleigh waves in an immersion technique allowing the measurement of their propagation velocity. The technique has been successfully verified for the reference materials aluminium, copper, and stainless steel. First measurements performed on mortar specimens demonstrate the applicability of this new diagnostic tool.     

Die Addition von Nucleophilen an Alkinderivate mit Push-pull-Gruppen

The preparative aspects of the addition of nucleophiles to alkyne-derivatives having both push- and pull-groups ( 1 ) are discussed: The addition of primary and secondary amines as well of aliphatic alcohols to the alkyne-derivatives 1 in most cases predominantly yields the Michael-adducts 2 – 10 . The importance of a side-reaction consisting in an addition of amines to C(2) of the alkyne-derivatives 1 increases in the series 1c ? 1b < 1a and is controlled by stereoelectronic effects. The spectroscopic properties of the compounds 2 – 10 are given.     

Discrimination between an Antiparallel and a Parallel β5.6-Helix Using 1Hα-NMR Spin-Lattice Relaxation

The ¹H-NMR spectrum of Boc-(L -Val-D -Val)₄-OH in CDCl₃ can be attributed either to an antiparallel or to a parallel double-stranded β^5.6-helical structure. To resolve this ambiguity, T₁-measurements have been carried out for the α-protons of Boc-(L -Val-D -Val)₄-OH and its monodeuterated analogue Boc-(L -Val-D -Val)₂ -α-²H-L -Val-D -Val-L -Val-D -Val-L -Val-D -Val-OH. The results show that the H^α of the fifth residue in one strand is close to the H^α of the seventh residue in the other strand, as expected for an antiparallel arrangement, a conclusive demonstration that the correct structure of Boc-(L -Val-D -Val)₄-OH is antiparallel.     

13C-NMR-Spektren von Poly-(S)-4-methyl1-hexen und Poly-(R,S)-4-methyl-l-hexen

Ohne Zusammenfassung