Synthesis and Characterization of the Titanium Containing Mesoporous Molecular Sieve MCM-48

Ti-MCM-48 mesoporous materials have been synthesized by sequential addition of alkoxides. The atomic ratio of Si and Ti in the synthesis gel was 40 and 5, respectively. The materials were characterized by means of powder XRD, N₂ adsorption-desorption measurements, HREM, ²⁹Si MAS NMR, diffuse reflectance FT-IR spectroscopy, electrophoretic mobility measurements and electron probe microanalysis.     

Consistency of Inhalatory Breathing Patterns in Professional Operatic Singers

Respiratory behavior is generally considered important to voice function, the assumption being that it affects the voice source. Accurate and consistent control of the voice source is particularly important in professional operatic singing. An erratic behavior of a factor influencing voice production is incompatible with a well-controlled vocal behavior. We analyzed the consistency of inhalatory breathing patterns during singing in five professional operatic singers, using the same material as in a previous investigation of phonatory breathing patterns. Rib cage (RC) and abdominal wall (AW) movements were recorded by respiratory inductive plethysmography. Consistency was analyzed in terms of the mean correlation between three takes of ten musical phrases. Results revealed a high consistency in lung volume (LV) change and RC movements in all singers and in AW movements in three singers. Consistency across different phrases was slightly lower. The results are compatible with the idea that inhalatory behavior is important to voice source in singing. A high correlation between LV change and RC movement was found in all singers and between LV change and AW movement in three. The contribution to LV change from RC was greater than that from AW in all singers.     

Molecular dynamics computer simulation of the hydration of two simple organic solutes

The hydration of two simple organic solutes has been studied using the molecular dynamics (MD) computer simulation method. Results of the simulations of a single 1,4-dioxane or 1,3-dioxane molecule dissolved in 122 water molecules are compared with those of a MD simulation of an empty cavity of corresponding size in 216 water molecules. This yields the opportunity to trace the specific effects of the polar and dispersion solute-solvent interactions on the properties of the water molecules in the hydration shell of the solute.

The hydration shell properties of 1,4-dioxane (μ) = 0·14 D) are very similar to those of the corresponding cavity, whereas those of 1,3-dioxane (μ) = 1·91 D) show significant deviations. Earlier conclusions that water structure-making and water structure-breaking properties of 1,4-dioxane are about equally balanced, while 1,3-dioxane is definitely structure-breaking, are confirmed. Moreover, it is shown that a slower self-diffusion and reorientation of water molecules upon addition of a cosolvent does not necessarily point at structure-making properties, additional to those that are already induced by the cavity formation. The introduction of an empty cavity also slows down self-diffusion and molecular reorientation in the hydration shell.     

Editorial

Journal of Solution Chemistry -