An efficient algorithm for elasto-viscoplastic vibrations of multi-layered composite beams using second-order theory

An efficient time-domain algorithm for plane non-linear flexural vibrations of multi-layered composite beams, which are driven into the inelastic range by severe transverse loadings, is presented. The influence of an axial static preload is considered in the sense of the quasi-linear second-order theory of structures. The inelastic parts of strain are treated as additional sources of selfstress in the linear elastic background-structure, driving the elastic response into the inelastic one. The efficiency of this exact formulation lies in the fact that linear solution techniques can be used in their most powerful form: Rubin's useful formulation for the quasi-static second-order transfer-matrix of linear elastic structures is applied in combination with modal analysis. Having in mind multi-metal beams, the classical lamination theory is assumed to be valid. Beams with overhang composed of ideal elastic-plastic and viscoplastic layers are studied as example structures. The fictitious sources of selfstress are calculated from the different material laws of the layers in a numerical time-stepping procedure, where a generalized midpoint-rule in combination with Crisfield's secant-Newton procedure is used.     

Tetrajodterephtalsäure-derivate als Röntgen-Kontrastmittel

New monoamides and diamides of tetraiodoterephthalic acid have been synthesized for evaluation as X-ray contrast agents. Solubility, toxicity, bilitropism, urotropism, and in some cases cholecystographic quality of these compounds are given.     

Optisch aktive übergangsmetall-komplexe XX. Optisch aktive cyclopentadienyl-perfluoropropyl-kobalt-komplexe mit zweizähnigen schiff-basen

In the reaction of C₅H₅ Co(C₃F₇)(CO)I with the Schiff base NN′, derived from S-(-)-?-phenylethylamine and pyridine carbaldehyde-2, the salt [C₅H₅Co(C₃F₇)NN′]⁺ I^? (Ia,b) is formed, which can be transformed to [C₅H₅ Co(C₃F₇)NN′]⁺ PF₆^? (IIa,b). The sodium salt Na⁺ [NN″]^? of the Schiff base, derived from S-(-)-α-phenylethylamine and pyrrol carbaldehyde-2, in the reaction with C₅H₅ C0(C₃F₇)(CO)I yields the neutral complex C₅H₅ Co(C₃F₇)NN″ (IIIa,b). The diastereoisomeric pairs IIa,b and IIIa,b are separated by fractional crystallisation and chromatography respectively into the optically pure components which differ in their ¹H NMR spectra. The IR, UV, CD, mass spectra and optical rotations of the new compounds IIa, IIb, IIIa and IIIb are compared.     

Synthesen in der Naphthalinreihe: Methoxylierte Tetralone und Naphthole

Ohne ZusammenfassungHerrn Prof. Dr.A. Franke in aufrichtiger Verehrung zum 80. Geburtstag gewidmet.     

Construction of Large Carbocyclic Rings by Ireland-Claisen Rearrangement of O-Silylated Lactone Enolates: Synthesis of (±)-muscone

(±)-Muscone (5) has been synthesized from methyl 13-(chloroformyl)tridecanoate (6) in nine steps in an overall yield of 24%. The key steps involve an efficient transformation of the readily accessible 14-hydroxy-15-methyl-15-hexadecenoic acid (9) into the tetradecanolide 1 and a subsequent Ireland-Claisen rearrangement of its triethylsilyl enolate 2 to a 8:1-mixture of the stereoisomeric 15-membered carbocycles 4 and 10 (Scheme 4).     

Optisch aktive übergangsmetall-komplexe : XXV. Substituenteneinflüsse auf die intramolekulare epimerisierung von tetragonal-pyramidalen molybdanund wolfram-komplexen

The synthesis, IR, ¹H NMR and UV spectra of optically active square pyramidal cyclopentadienyldicarbonyl-molybdenum and -tungsten complexes with Schiff bases, derived from methyl-substituted pyridine carbaldehyde(2) and S-(—)-α-methylbenzylamine, are described. The epimerisation of these complexes, measured polarimetrically at 75–97°C in DMF, follows a 1^st order rate law and represents a regular pentatopal skeletal rearrangement. The inductive effect of a methyl group in the para position of a pyridine ring leads to a retardation of the epimerisation compared to unsubstituted complexes. The rate constants decrease even more if an ortho methyl group is introduced into the pyridine system, since additional steric effects are introduced. If the metal complex contains a 4,6-dimethyl-substituted Schiff base as a chelating ligand, the contributions of a 4- and a 6-methyl group are additive. A benzene ring fused to the 5,6-positions of the pyridine system also leads to stabilisation of the configuration.