Analytic Representation of Volume Flow as a Function of Geometry and Pressure in a Static Physical Model of the Glottis

A static physical model of the larynx (model M5) was used to obtain a large set of volume flows as a function of symmetric glottal geometry and transglottal pressure. The measurements cover ranges of these variables relevant to human phonation. A generalized equation was created to accurately estimate the glottal volume flow given specific glottal geometries and transglottal pressures. Both the data and the generalized formula give insights into the flow behavior for different glottal geometries, especially the contrast between convergent and divergent glottal angles at different glottal diameters. The generalized equation produced a fit to the entire M5 dataset (267 points) with an average accuracy of 3.4%. The accuracy was about seven times better than that of the Ishizaka-Flanagan approach to glottal flow and about four times better than that of a pressure coefficient approach. Thus, for synthesis purposes, the generalized equation presented here should provide more realistic glottal flows (based on steady flow conditions) as suitable inputs to the vocal tract, for given values of transglottal pressure and glottal geometry. Applications of the generalized formula to pulses generated by vocal fold motions typical of those produced by the Ishizaka-Flanagan coupled-oscillator model and the more recent body-cover model of Story and Titze are also included.     

Phonation threshold pressure: comparison of calculations and measurements taken with physical models of the vocal fold mucosa

In an important paper on the physics of small amplitude oscillations, Titze showed that the essence of the vertical phase difference, which allows energy to be transferred from the flowing air to the motion of the vocal folds, could be captured in a surface wave model, and he derived a formula for the phonation threshold pressure with an explicit dependence on the geometrical and biomechanical properties of the vocal folds. The formula inspired a series of experiments [e.g., R. Chan and I. Titze, J. Acoust. Soc. Am 119, 2351-2362 (2006)]. Although the experiments support many aspects of Titze's formula, including a linear dependence on the glottal half-width, the behavior of the experiments at the smallest values of this parameter is not consistent with the formula. It is shown that a key element for removing this discrepancy lies in a careful examination of the properties of the entrance loss coefficient. In particular, measurements of the entrance loss coefficient at small widths done with a physical model of the glottis (M5) show that this coefficient varies inversely with the glottal width. A numerical solution of the time-dependent equations of the surface wave model shows that adding a supraglottal vocal tract lowers the phonation threshold pressure by an amount approximately consistent with Chan and Titze's experiments.     

Synthetic aspects of the characterization of some silica-bound complexing agents

A number of synthetic aspects of silica-bound complexing agents are considered. Modifications of the procedure for amidization of bound amines and of the diazotizationcoupling sequence are discussed. The amidization of aminopropyl silica gel appears to be complete while that of ethylenediamine silica gel is less so. Loss of activity of the dried, bound diazonium salt appears to result from return to the Ar-NH₂ form, while a decrease in metal-ion complexation capacity for 8-quinolinol silica gel compared to the aminopropyl or ethylenediamine silica gel seems to be related to steric clogging of the matrix pores by bound organic moieties. A method of stripping the azo-coupled ligand from the appendage is examined, and some infrared and thermogravimetric characterizations are presented.     

Cyclotrimerization of cyclic diynes via metal atom cocondensation; revised structure for the reported “percyclophane-4”

A compound previously assigned the “percyclophane-4” structure $\text{3}$ has been shown to be the triyne $\text{2}$.     

Ion formation in fast atom bombardment mass spectrometry: a divided probe investigation of gas-phase reactions

Some ion-formation processes during fast atom bombardment (FAB) are discussed, especially the possibility of reactions in the gas phase. Divided (two halves) FAB probe tips were used for introducing two different samples into the source at the same time. Our results showed [M + A]⁺ ions (where M = crown ethers and A = alkali metal ions), can be produced, at least in part, in the gas phase when crown ethers and sources of alkali metal ion are placed on two halves of the FAB probe tip. The extent of this ion formation depends on the volatility of the crown ether and on steric factors. Cluster ions such as (M + LiCl)Li⁺, (2M + LiCl)Li⁺, [2M + K]⁺ and [2M + Na]⁺ are also observed to form in the gas phase. Unimolecular decompositions contribute to some ions detected in FAB. When the alkali ion salt and the crown ether are mixed together the probability of [M + A]⁺ ion formation increases significantly, regardless of the volatility of the crown ether.