The use of visual cues in the perception of non-native consonant contrasts

This study assessed the extent to which second-language learners are sensitive to phonetic information contained in visual cues when identifying a non-native phonemic contrast. In experiment 1, Spanish and Japanese learners of English were tested on their perception of a labial/ labiodental consonant contrast in audio (A), visual (V), and audio-visual (AV) modalities. Spanish students showed better performance overall, and much greater sensitivity to visual cues than Japanese students. Both learner groups achieved higher scores in the AV than in the A test condition, thus showing evidence of audio-visual benefit. Experiment 2 examined the perception of the less visually-salient /1/-/r/ contrast in Japanese and Korean learners of English. Korean learners obtained much higher scores in auditory and audio-visual conditions than in the visual condition, while Japanese learners generally performed poorly in both modalities. Neither group showed evidence of audio-visual benefit. These results show the impact of the language background of the learner and visual salience of the contrast on the use of visual cues for a non-native contrast. Significant correlations between scores in the auditory and visual conditions suggest that increasing auditory proficiency in identifying a non-native contrast is linked with an increasing proficiency in using visual cues to the contrast.     

On triangle-free projective graphs

The 2-projection property was introduced by Corominas for ordered sets; it was generalized to other structures and arities by Pouzet, Rosenberg and Stone and independently by Davey, McKenzie, Nation and Pálfy. We investigate triangle-free projective graphs and give a characterization for graphs that satisfy a certain condition on their cycles. In those cases, projectivity is equivalent to quasiprojectivity. As a corollary, we obtain a characterization of projective orders of height 1.Dedicated to the memory of Alan DayPresented by J. Sichler.     

Microstructure Evolution of Nonhydrolytic Alumina Gels

Nonhydrolitic sol-gel processes of aluminum chloride and aluminum bromide with isopropyl ether and aluminum sec-butoxide were performed at various temperatures. Based on the Arrhenius type variation of the gelation time with temperature, activation energies for the gelation were found to be in the range 19–25 Kcal/mol range. The energies were found to be sensitive to the nature of the aluminum ligands and the chemical scheme. Due to the large activation energy, it is possible to stop the reaction at any time before gelation by cooling the sol to room temperature. Small angle X-ray scattering (SAXS) of sols from the AlClAlCl₃/Pr O system shows unique development of a fractal like structure with nanometer scale order, demonstrated by discrete peaks in the SAXS data. A fractal dimension D = 1.64 was found. An aggregation scheme is proposed to explain this phenomenon. A fractal dimension of 2.4 without small scale ordering found for xerogels prepared from the AlCl₃/ASB system reflects the effect of the different precursors on the microstructure of nonhydrolytic gels.     

Effect of Aging on Nonhydrolytic Alumina Xerogels

Nonhydrolytic sol-gel route is a relatively recent process which enables production of complex, multicomponent oxide materials. This process has some advantages over the conventional hydrolytic sol-gel route due to the ability to produce low-shrinkage, homogeneous, multicomponent gels. The objective of this work was to determine the effects of aging of nonhydrolytic gels on the composition, yield, phase transformations and morphology. Xerogels were prepared from aluminum chloride and isopropyl ether. Properties were studied using AgNO₃ titrations, TGA/DTA, XRD, and BET analysis. We have found that the gels contain significant amount of chlorine where the Cl/Al atomic ratio ranges from 1.1–0.6 depending on the aging time. The crystallization temperature and enthalpy of crystallization decreased with aging time. The decrease of the surface area near the crystallization temperature correlates well with the decrease of the enthalpy of crystallization as a function of aging time. A closed pore phenomenon has been observed in the nonhydrolytic alumina system. Finally, analysis of the condensation degree (CD) yielding Al–O–Al bonds suggests that the rate determining step before the gel point is the alkoxy groups formation. However, during aging of the gels, the CD remains constant since the condensation of chloride with isopropoxy groups is stericly inhibited. Surface areas in the 300–650 m²/g range were obtained depending on the aging time.     

Two properties of projective orders

We prove a closure property of the class of projective orders without infinite chains, and strengthen Larose's theorem on the equivalence between projectivity and quasiprojectivity for finite orders.     

Computational models of music perception and cognition II: Domain-specific music processing

In Part I [Purwins H, Herrera P, Grachten M, Hazan A, Marxer R, Serra X. Computational models of music perception and cognition I: The perceptual and cognitive processing chain. Physics of Life Reviews 2008, in press, doi:10.1016/j.plrev.2008.03.004], we addressed the study of cognitive processes that underlie auditory perception of music, and their neural correlates. The aim of the present paper is to summarize empirical findings from music cognition research that are relevant to three prominent music theoretic domains: rhythm, melody, and tonality. Attention is paid to how cognitive processes like category formation, stimulus grouping, and expectation can account for the music theoretic key concepts in these domains, such as beat, meter, voice, consonance. We give an overview of computational models that have been proposed in the literature for a variety of music processing tasks related to rhythm, melody, and tonality. Although the present state-of-the-art in computational modeling of music cognition definitely provides valuable resources for testing specific hypotheses and theories, we observe the need for models that integrate the various aspects of music perception and cognition into a single framework. Such models should be able to account for aspects that until now have only rarely been addressed in computational models of music cognition, like the active nature of perception and the development of cognitive capacities from infancy to adulthood.     

Modeling the effect of molecular architecture of comb polymers on the behavior of Al2O3 dispersions using charge/composition factors (CCF)

In this work, we study the effect of periodicity and PEO side-chain length in four PMAA-PEO (sodium salt) comb polymers with known molecular architecture on Al₂O₃ colloidal dispersions in DI water. We introduce here charge composition factors (CCF) representing charge density of the comb polymers defined as (number of charged units in a repeating unit)/(molecular weight of a repeating unit). We find, for the first time to our knowledge, that the CCF can be used along with dispersant dosage to obtain explicit functions predicting the conductivity of the dispersants in solution, the zeta potential behavior during dispersant titrations, and the isoelectric point (IEP) of the dispersions. In addition, the dosage normalized by the CCF provides a basis for comparison for the dispersants to elucidate the trends found in adsorption and potentiometric titrations. Thus, the CCF can be used as a tool for the design of improved and new comb polymer molecular architectures.     

Acoustic-phonetic characteristics of speech produced with communicative intent to counter adverse listening conditions

This study investigated whether speech produced in spontaneous interactions when addressing a talker experiencing actual challenging conditions differs in acoustic-phonetic characteristics from speech produced (a) with communicative intent under more ideal conditions and (b) without communicative intent under imaginary challenging conditions (read, clear speech). It also investigated whether acoustic-phonetic modifications made to counteract the effects of a challenging listening condition are tailored to the condition under which communication occurs. Forty talkers were recorded in pairs while engaged in "spot the difference" picture tasks in good and challenging conditions. In the challenging conditions, one talker heard the other (1) via a three-channel noise vocoder (VOC); (2) with simultaneous babble noise (BABBLE). Read, clear speech showed more extreme changes in median F0, F0 range, and speaking rate than speech produced to counter the effects of a challenging listening condition. In the VOC condition, where F0 and intensity enhancements are unlikely to aid intelligibility, talkers did not change their F0 median and range; mean energy and vowel F1 increased less than in the BABBLE condition. This suggests that speech production is listener-focused, and that talkers modulate their speech according to their interlocutors' needs, even when not directly experiencing the challenging listening condition.     

Tracking Surface Glycans on Live Cancer Cells with Single‐Molecule Sensitivity

Using a combination of metabolically labeled glycans, a bioorthogonal copper(I)‐catalyzed azide–alkyne cycloaddition, and the controlled bleaching of fluorescent probes conjugated to azide‐ or alkyne‐tagged glycans, a sufficiently low spatial density of dye‐labeled glycans was achieved, enabling dynamic single‐molecule tracking and super‐resolution imaging of N‐linked sialic acids and O‐linked N‐acetyl galactosamine (GalNAc) on the membrane of live cells. Analysis of the trajectories of these dye‐labeled glycans in mammary cancer cells revealed constrained diffusion of both N‐ and O‐linked glycans, which was interpreted as reflecting the mobility of the glycan rather than to be caused by transient immobilization owing to spatial inhomogeneities on the plasma membrane. Stochastic optical reconstruction microscopy (STORM) imaging revealed the structure of dynamic membrane nanotubes.     

Fixed points of posets and clique graphs

The fixed point property for partial orders has been the object of much attention in the past twenty years. Recently, M. Roddy ([7]) proved this famous conjecture of Rival (see [6]): the class of finite orders with the fixed point property is closed under finite products.In this article, we prove that a finite order has the fixed point property if the sequence of iterated clique graphs of its comparability graph tends to the trivial graph.