Étudiants adultes et études collégiales à la formation régulière

La présente recherche a été subventionnée par le ministère de l’Éducation et de l’Enseignement supérieur dans le cadre du Programme de recherche et d’expérimentation pédagogique (PREP) de l’Association des collèges privés du Québec (ACPQ)

Fano Resonances in Mid-Infrared Spectra of Single-Walled Carbon Nanotubes

This work revisits the physics giving rise to the carbon nanotubes phonon bands in the mid- infrared. Our measurements of doped and undoped samples of single-walled carbon nanotubes in Fourier transform infrared spectroscopy show that the phonon bands exhibit an asymmetric lineshape and that their effective cross-section is enhanced upon doping. We relate these observations to electron-phonon coupling or, more specifically, to a Fano resonance phenomenon. We note that only the dopant-induced intraband continuum couples to the phonon modes and that defects induced in the sidewall increase the resonance probabilities.Comment: 5 pages, 4 figures and 1 Supplementary Information File (in pdf

Consonance and Dissonance of Simultaneous Trichords in Western Music: A Listening Experiment to Test Models of Harmonicity and Roughness

Previous empirical studies have suggested that the perceived consonance/dissonance (C/D) of a musical chord depends on its psychoacoustic smoothness (lack of roughness), spectral harmonicity (perceptual fusion), and/or musical familiarity. We tested the dependence of C/D on smoothness and harmonicity in a hearing experiment that included all 19 possible trichords in musical pitch-class set theory. In each trial, a listener heard a chord (duration: 300 or 500 ms) and rated its C/D on an 11-point scale. Each trichord was presented 10 times: 4 times constructed from octave-complex tones (OCTs, sounding like an electronic organ) and 6 times from natural piano tones. Each OCT chord was presented in 4 different transpositions. The piano chords were in close or open position, and root position or 1st/2nd inversion (2 levels of spacing x 3 levels of inversion = 6 levels of voicing). We found no main effect of timbre (OCT versus piano) and no interaction between trichord and timbre. Results correlated closely with predictions of simple models of roughness and harmonicity. The roughness model performed better, and the predictions correlated with each other. A combined model was not superior to roughness alone. The results were consistent with a multifactorial model of the C/D of a musical chord, the main factors being roughness, harmonicity, and familiarity

Belugas (Delphinapterus leucas) create facial displays during social interactions by changing the shape of their melons

Beluga whales are considered unique among odontocetes in their ability to visibly alter the appearance of their head by changing the shape of the melon, but only anecdotal observations are available to evaluate the use or potential function of these melon shapes. This study of belugas in professionally managed care aimed to establish an ethogram for the repertoire of categorizable melon shapes and then evaluate their potential function as intentional communication signals by determining if they were produced and elaborated during social interactions of varying behavioral contexts while in the line of sight of a recipient. Five different melon shapes were reliably identified in video observations of the primary study population (n = 4) and externally validated in a second aquarium population (n = 51). Among the 2570 melon shapes observed from the primary study subjects, melon shapes occurred 34 × more frequently during social interactions (1.72 per minute) than outside of social interactions (0.05 per minute). Melon shapes occurring during social interactions were performed within the line of sight of a recipient 93.6% of the time. The frequency of occurrence of the different melon shapes varied across behavioral contexts. Elaboration of melon shapes through extended duration and the occurrence of concurrent open mouth displays varied by shape type and across behavioral contexts. Melon shapes seem to function as visual displays, with some characteristics of intentional communication. This ability could yield adaptive benefits to belugas, given their complex social structure and hypothesized mating system that emphasizes pre-copulatory female mate choice

Estrogen replacement therapy induces functional asymmetry on an odor memory/discrimination test

The secondary afferents of the olfactory system largely project to the ipsilateral cortex without synapsing in the thalamus, making unilateral olfactory testing a useful probe of ipsilateral hemispheric activity. In light of evidence that lateralized performance on some perceptual tasks may be influenced by estrogen, we assessed left:right nostril differences in two measures of olfactory function in 14 post-menopausal women receiving estrogen replacement therapy (ERT) and 48 post-menopausal women receiving no such therapy. Relative to women not taking ERT, those receiving ERT exhibited better performance in the left nostril and poorer performance in the right nostril on an odor memory/discrimination test. Similar laterality effects were not observed for an odor detection threshold test employing phenyl ethyl alcohol. These results suggest that estrogen influences the lateralization of an odor memory/discrimination task and that hormone replacement therapy in the menopause may be an excellent paradigm for understanding lateralizing effects of hormones on some sensory processes. (C) 2008 Elsevier B.V. All rights reserved

Travail du sol, structure et fonctionnement hydrique du sol en régime d'évaporation.

16 ref.Une des fonctions assignées au travail du sol est la modification de la structure en vue de contrôler le fonctionnement hydrique du sol. L'étude que nous avons conduite avait pour but d'analyser l'effet de la structure sur le dessèchement d'un sol cultivé au printemps. Trois traitements se différenciant par leur niveau de compacité (fort/faible) et/ou par la date de travail du sol (automne/printemps) ont été créés dans un sol de craie (Rendoll Typic) et dans un sol de limon (Luvisol Orthic). Un suivi de la teneur en eau et du potentiel de l'eau a été réalisé, respectivement, à partir de prélèvements gravimétriques et de mesures par des tensiomètres. Le flux d'évaporation a été calculé par la méthode du plan de flux nul. Les propriétés hydrodynamiques ont été estimées par la méthode évaporative de Wind. Dans le sol de craie, le traitement compacté avait un flux d'évaporation supérieur à celui des traitements travaillés d'environ 1mm/jour. Les premiers centimètres du traitement compacté restaient humides tandis que ceux des traitements travaillés s'asséchaient rapidement. Au contraire, en profondeur, la teneur en eau du traitement compacté était inférieure à celle des traitements travaillés. Cet effet de la compacité du sol est à mettre en relation avec les variations de conductivité hydraulique du sol non saturé en fonction de la masse volumique du sol. La conductivité hydraulique était plus élevée dans le traitement compacté, probablement à cause d'une surface de contact entre fragments terreux plus grande, donc d'une meilleure continuité de la phase liquide du sol non saturé. L'augmentation de la conductivité hydraulique du traitement compacté a permis une meilleure ré-alimentation en eau de la surface du sol depuis les couches profondes, donc un flux d'évaporation plus élevé et un dessèchement de l'ensemble de la couche labourée. Cet effet n'a pas été observé dans le sol de limon pour lequel les variations de structure du sol n'ont pas eu de conséquences marquées sur le dessèchement du sol. La conductivité hydraulique était la même, à une teneur en eau donnée, quelle que soit la masse volumique. Ceci pourrait résulter de la formation de pores structuraux reliques par compactage. Il apparaît qu'un sol trop poreux en sortie d'hiver peut limiter le dessèchement de la couche labourée au printemps. La présence des pores reliques dans un sol pourrait permettre de caractériser les conditions de compactage qu'il a subie