Vocal fold vibrations are more difficult to achieve in obstruents than sonorants due to the aerodynamic voicing constraint (AVC), i.e., the fact that a buildup of air pressure in the supraglottal cavity during oral closures reduces the transglottal airflow. The AVC can be circumvented by various voicing adjustment gestures, such as larynx lowering, tongue root advancement and tongue body lowering. The current study employed laryngeal and lingual ultrasound to investigate the use of these strategies in Canadian French. The vertical movement of the larynx was measured using optical flow analysis, while lingual movement was analyzed by tracking X and Y coordinates at distinct fanlines across consecutive images.

Results revealed that there was more pronounced larynx lowering in voiced obstruents and that it tended to be greater in voiced stops than in voiced fricatives. Tongue-related maneuvers displayed more interspeaker variation but tendencies showed that the tongue root was more advanced in voiced stops than in voiced fricatives and slightly more for /d/ than /b/. Significant tongue body lowering was observed for both voiced stops and voiced fricatives only preceding the vowel /a/. Finally, larynx lowering was strongly correlated with voicing duration in voiced obstruents. A similar but weaker correlation was found for tongue root advancement.

Overall, this study suggests that larynx lowering is an efficient strategy to circumvent the AVC in Canadian French but that some speakers may also resort to lingual adjustments. Additional strategies that are known to play a role, such as nasal or oral leakage, were not considered.

Jarai is a Chamic language of Vietnam and Cambodia that is traditionally described as preserving the original Austronesian voicing contrast in onset obstruents. However, there is anecdotal evidence that it has developed a register contrast, i.e. a binary contrast based on a bundle of spectral properties like pitch, voice quality and vowel quality. We conducted production and perception experiments of the voicing/register contrast in two Jarai varieties spoken in Saom Kaning, Cambodia, and Ea Sup, Vietnam, to determine if they preserve voicing and/or have developed a register contrast. Results show that both dialects have a register contrast primarily based on vowel height modulations (F1) and that onset voicing has become at best an optional secondary property of register. F1 is also the primary cue used for register identification in both dialects. Implications for the diachronic development of the register contrast in Chamic languages and in Mainland Southeast Asia in general are discussed.

There is no consensus on the nature, or even the existence, of Vietnamese word stress. While some authors have proposed that it is morphosyntactically conditioned (Thompson 1963, Thompson 1965, Cao 2003 [1978], Ngô 1984), others have adopted the view that it is consistently word-final (Trần 1967; Nguyễn & Ingram 2006, 2007b; Phạm 2008; Nguyễn 2010) or that it lacks stress altogether (Emeneau 1951). This is due to the elusive nature of word prominence in Vietnamese, and to the small number of studies that tackle the issue experimentally. In this paper, acoustic experiments designed to test previous hypotheses and tease apart possible types of prominence are presented. Southern Vietnamese disyllabic words with various morphosyntactic structures were recorded in controlled environments to test for stress and phrasal effects. Their duration, mean intensity, mean f0, f0 range and formants were then measured to assess word prominence. Results suggest that there is little evidence for word stress in Southern Vietnamese and that reports of final stress can be reinterpreted as phrase-final lengthening. Focus-marking strategies bring no additional evidence for the existence of stress, but they seem to be partly speaker- and tone-specific, which supports results obtained in studies of Northern Vietnamese (Michaud 2005).

Aluminophthalocyanine and fullerene were trapped in solid transparent matrices using the sol-gel process. The covalent bonding to the matrix improved the chemical stability of the fullerene doped sample. Solid state optical limiting at 532 nm, mainly due to reverse saturable absorption processes, was observed with such samples. The non-linear transmission threshold was typically about 10 mJ/cm2 and an induced density of 1.6 was observed with three orders of magnitude greater illumination. Fluorescent decay measurements support the choice of a three energy level absorption model for the process, which allows indirect measurement of the excited-state absorption.