Aliphatic isocyanurates and polyisocyanurate networks

The production, processing, and application of aliphatic isocyanate (NCO)-based thermosets such as polyurethane coatings and adhesives are generally limited by the surprisingly high viscosity of tri-functionality and higher-functionality isocyanurates. These compounds are essential crosslinking additives for network formation. However, the mechanism by which these high viscosities are caused is not yet understood. In this work, model aliphatic isocyanurates were synthesized and isolated in high purity (>99%), and their viscosities were accurately determined. It was shown that the presence of the NCO group has a strong influence on the viscosity of the system. From density functional theory calculations, a novel and significant bimolecular binding potential of À8.7 kJ/mol was identified be- tween NCO groups and isocyanurate rings, confirming the important role of the NCO group. This NCO-to-ring inter- action was proposed to be the root cause for the high viscosities observed for NCO-functional isocyanurate systems. Molecular dynamics simulations carried out to further confirm this influence also suggest that the NCO-to- ring interaction causes a significant additional contribution to viscosity. Finally, model functional isocyanurates were further reacted into densely crosslinked polyisocyanurate networks which showed interesting material properties.This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement no. 642890 (http:// thelink-project.eu/), and it was partially supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the strategic funding UID/FIS/04650/2013, and under the project Search-ON2: NORTE-07-0162-FEDER000086

Publishing scientific research

Springer Author workshop for postgraduate students and researchers including the following : Publishing scientific research; why you should publish, where to publish, how to structure an article, learning from peer reviewers, what is Open Access publishing, Open Access vs traditional publishing, what is an Impact Factor mean etc.Springer Author workshop for postgraduate students and researchers, presented on Tuesday, 28 February 2012, in the Library auditorium, Level 3, Merensky Library II, University of Pretoria,cp201

Expansion of prosodic abilities at the transition from babble to words: a comparison between children with cochlear implants and normally hearing children

Objectives: This longitudinal study examined the impact of emerging vocabulary production on the ability to produce the phonetic cues to prosodic prominence in babbled and lexical disyllables of infants with Cochlear Implants (CI) and normally hearing infants (NH). Current research on typical language acquisition emphasizes the importance of vocabulary development for phonological and phonetic acquisition. Children with cochlear implants (CI) experience significant difficulties with the perception and production of prosody, and the role of possible top-down effects is therefore particularly relevant for this population. Design: Isolated disyllabic babble and first words were identified and segmented in longitudinal audio-video recordings and transcriptions for 9 NH infants and 9 infants with CI interacting with their parents. Monthly recordings were included from the onset of babbling until children had reached a cumulative vocabulary of 200 words. Three cues to prosodic prominence, F0, intensity and duration, were measured in the vocalic portions of stand-alone disyllables. In order to represent the degree of prosodic differentiation between two syllables in an utterance, the raw values for intensity and duration were transformed to ratios, and for f0 a measure of the perceptual distance in semitones was derived. The degree of prosodic differentiation for disyllabic babble and words for each cue was compared between groups. In addition, group and individual tendencies on the types of stress patterns for babble and words were also examined. Results: The CI group had overall smaller pitch and intensity distances than the NH group. For the NH group, words had greater pitch and intensity distances than babbled disyllables. Especially for pitch distance, this was accompanied by a shift towards a more clearly expressed stress pattern that reflected the influence of the ambient language. For the CI group, the same expansion in words did not take place for pitch. For intensity, the CI group gave evidence of some increase of prosodic differentiation. The results for the duration measure showed evidence of utterance-final lengthening in both groups. In words, the CI group significantly reduced durational differences between syllables so that a more even-timed, less differentiated pattern emerged. Conclusions: The onset of vocabulary production did not have the same facilitatory effect for the CI infants on the production of phonetic cues for prosody, especially for pitch. It was argued that the results for duration may reflect greater articulatory difficulties in words for the CI group than the NH group. It was suggested that the lack of clear top-down effects of the vocabulary in the CI group may be due to a lag in development caused by an initial lack of auditory stimulation, possibly compounded by the absence of auditory feedback during the babble phase