Investigating the consistency of woodwind instrument manufacturing by comparing five nominally identical oboes

For large-scale woodwind instrument makers, producing instruments with exactly the same playing characteristics is a constant aim. This paper explores manufacturing consistency by comparing five Howarth S10 student model oboes. Psychophysical testing involving nine musicians is carried out to investigate perceived differences in the playing properties of the two Howarth oboes believed to be most dissimilar. Further testing, involving one musician and combinations of the five oboes, provides information regarding the relative playabilities of the instruments at specific pitches. Meanwhile, input impedance measurements are made on the five oboes for fingerings throughout the playing range and their bore profiles are measured. The main findings are (1) the two instruments used in the preliminary psychophysical testing are perceived as identical by most of the musicians, although differences are identified by two players when playing the note F6 and by one player when playing in the lowest register, (2) a variation in the playability of F6 across the five oboes is due to differences in the elevation of the C key, and (3) variations in the playing properties in the lowest register are related to input impedance differences,which, in turn, appear to be at least partly due to bore profile differences.     

Role of nanomechanical properties in the tribological performance of phospholipid biomimetic surfaces

The role of phospholipid bilayers in controlling and reducing frictional forces between biological surfaces is investigated by three complementary experiments: friction forces are measured using a homemade tribometer, mechanical resistance to indentation is measured by AFM, and lipid bilayer degradation is controlled in situ during friction testing using fluorescence microscopy. DPPC lipid bilayers in the solid phase generate friction coefficients as low as 0.002 (comparable to that found for cartilage) that are stable through time. DOPC bilayers formed by the vesicle fusion method or the adsorption of mixed micelles generate higher friction coefficients. These coefficients increased through time, during which the bilayers degraded. The friction coefficient is correlated with the force needed to penetrate the bilayer with the AFM tip. With only one bilayer in the contact region, the friction increased to a similar value of about 0.08 for the DPPC and DOPC. Our study therefore shows that good mechanical stability of the bilayers is essential and suggests that the low friction coefficient is ensured by the hydration layers between adjacent lipid bilayers.     

Conformational Analysis of Thermotropic Liquid Crystalline Polyesters

PCILO conformational calculations have been carried out on several model compounds of thermotropic liquid crystalline polyesters [—OC—φ—φ—φ—CO—Os—R—O—] where R = (—CH₂—)₂; (—CHCH₃—)₂; (—CHCH₃—CH₂—). Several conformations corresponding to the trans and gauche states of the C-C single bonds are preferred, the TGT form being of lower energy than the TTT form. The replacement of—CH₂—group by—CH(CH₃) group results in a decrease of the number of the energy minima, an increase in the energy of the molecule in all the preferred conformations, compared to that of the TGT form, a sharpening of the potential energy wells and an increase in the energy barriers. The presence of a methyl group also shifts the aliphatic chain away from the ideal trans and gauche positions.     

Polyesters with Mesogenic Elements and Flexible Spacers in the Main Chain: A Further Investigation by Conformational Energy Calculations

PCILO conformational calculations have been carried out on several model compounds of thermotropic liquid crystalline polyesters [- OC-R₁ -CO-O-R₂]- where R₁ = biphenyl, terphenyl and R₂ = (-CH₂-)₃, -CH₂-C(CH₃)₂-CH₂–CH₂-C(C₂H₅-) CH₂-. The calculated structures can be compared to the X-ray crystallographic data. The conformational characteristics of the carboxyl groups are independent of the number of phenyl rings. The introduction of substituents into the flexible spacer results in a sharpening of the potential energy wells and an increase in the energy barriers.     

Enantiomer separaton of tifluadom and analogues by liquid chromatography with cellulose-based chiral stationary phases

Chromatographia - The resolution of nine recamic mixtures of tifluadom analogues has been evaluated using the chiral stationary phases Chiralcel OD and Chiralcel OJ. The separation was performed on...