The ab initio conformational analysis of 10 α-aminoaldehydes and α-aminoketones containing the N–C–CO moiety was carried out at the HF/3-21G, HF/6-31G** and MP2/6-31G** levels. Conformational ...preferences are mainly interpreted in terms of different kinds of intramolecular hydrogen bonding, although other effects should also be considered. These effects explains the energetic and geometrical differences observed between N–C–CO and related C–C–CO compounds. Finally, by means of an ab initio method for the treatment of the solvent as a continuum (polarizable continuum model, PCM), the influence of water on the conformational stabilities was estimated. Significant changes in relative energies were found, which were related to the interaction between the dipole moment of the solute and the reaction field of the solvent, although local dipolar interactions or the presence of hydrogen bonding in certain conformations can also be important.
The properties of dental cyanoacrylate cement "FH", which has protective and bacteriostatic effect on dental pulp, were compared with that of glass-ionomer cement. The operational properties such as ...setting time and consistency were good, but the mechanical properties as dental cement were a little inferior. These properties were affected definitely by temperature and humidity than the glass-ionomer cement, especially the influence of humidity was very high. However, the influence on bond strength was almost nothing, especially in the early period of setting. The factors affecting it could be very low disintegration. The bond strength for dentin after 24 hours the start of mixing of FH cement was much higher than that for enamel, but the strength rapidly decreased by thermal cycling between 4℃ and 50℃ in water.
An investigation of the effect of water absorption on the mechanical properties and fatigue strength of ±45° angle-ply carbon/epoxy composites, i.e., 130°C-cure-type composites T-1/347 and ...180°C-cure-type MM-1/982X, has been carried out. In both composites, water absorption lowers the strength of the interface, resulting in a decrease in a tensile strength, an elongation a the break, and fatigue strength. In a higher stress region in laboratory air, cyclic loads make the temperature of a T-1/347 composite so high that plastic deformation of the matrix is enhanced and the fatigue life is shortened. In water, however, the cooling effects of water circulation around specimens become predominant, and hence the fatigue life increases in a high-stress region. We also point out the usefulness of scanning acoustic microscope in the examination of the internal damage of the composites.
Il est connu que l'eau, même en quantité limitée, modifie sérieusement le comportement rhéologique des minéraux comme le quartz et l'olivine. Par contre, on connaît mal l'influence de l'eau sur les ...propriétés de déformation des agrégats de différents silicates.
L'auteur a étudié une aplite à grains fins de Malmberget en Suède septentrionale. Des échantillons secs ou saturés d'eau ont été soumis à des températures jusqu'à 800°C et des pressions de confinement jusqu'à 1.5 GPa. Les essais ont été effectués avec un équipement de Griggs. La pression de confinement était transmise par du chlorure de sodium ou du plomb.
L'eau modifie la résistance de cette roche, mais son effet est modéré. L'auteur présente des résultats expérimentaux à différentes températures et pressions. Les différences des microstructures sont aussi discutées.
Even in small amounts water has been found to affect severely the rheological behaviour of minerals like quartz and olivine. Very little is known, however, about the influence of water on the deformation properties of aggregates of different silicates.
I have deformed both dry and water saturated specimens of a fine grained aplite from Malmberget in Northern Sweden at temperatures up to 800° C and confining pressures up to 1.5 GPa. The experiments were performed in a Griggs'hot creep apparatus operated in the constant strain-rate mode (10-6 < ê < 10-4 s-1). Lead or sodium chloride was used as pressure transmitting medium.
Water influences the strength of this rock, but the effect is moderate. Experimental results at different temperatures and pressures are presented and differences in microstructures are also discussed.
Alm Ove. Influence of water on the strength and deformation properties of a granitic aplite at high pressures and temperatures. In: Bulletin de Minéralogie, volume 102, 2-3, 1979. Mécanismes de déformation des minéraux et des roches.
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