Simple model of adsorption on external surface of carbon nanotubes: a new analytical approach basing on molecular simulation data

Nitrogen adsorption on carbon nanotubes is wide- ly studied because nitrogen adsorption isotherm measurement is a standard method applied for porosity characterization. A further reason is that carbon nanotubes are potential adsorbents for separation of nitrogen from oxygen in air. The study presented here describes the results of GCMC simulations of nitrogen (three site model) adsorption on single and multi walled closed nanotubes. The results obtained are described by a new adsorption isotherm model proposed in this study. The model can be treated as the tube analogue of the GAB isotherm taking into account the lateral adsorbate-adsorbate interactions. We show that the model describes the simulated data satisfactorily. Next this new approach is applied for a description of experimental data measured on different commercially available (and characterized using HRTEM) carbon nanotubes. We show that generally a quite good fit is observed and therefore it is suggested that the observed mechanism of adsorption in the studied materials is mainly determined by adsorption on tubes separated at large distances, so the tubes behave almost independently

The Motor Somatotopy of Speech Perception

open6siL.F. is supported by Italian Ministry of Education; by the E.C. grants Contact, Robot-cub, and Poeticon; and by Fondazione Cassa di Risparmio di Ferrara. F.P. is supported, in part, by MRC grants (U1055.04.003.00001.01, U1055.04.003.00003.01) and by the E.C. grant Nestcom.Listening to speech recruits a network of fronto-temporo-parietal cortical areas [1]. Classical models consider anterior (motor) sites to be involved in speech production whereas posterior sites are considered to be involved in comprehension [2]. This functional segregation is challenged by action-perception theories suggesting that brain circuits for speech articulation and speech perception are functionally dependent [3, 4]. Although recent data show that speech listening elicits motor activities analogous to production [5-9], it's still debated whether motor circuits play a causal contribution to the perception of speech [10]. Here we administered transcranial magnetic stimulation (TMS) to motor cortex controlling lips and tongue during the discrimination of lip- and tongue-articulated phonemes. We found a neurofunctional double dissociation in speech sound discrimination, supporting the idea that motor structures provide a specific functional contribution to the perception of speech sounds. Moreover, our findings show a fine-grained motor somatotopy for speech comprehension. We discuss our results in light of a modified "motor theory of speech perception" according to which speech comprehension is grounded in motor circuits not exclusively involved in speech production [8].openA. D'Ausilio; F. Pulvermüller; P. Salmas; I. Bufalari; C. Begliomini; L. FadigaD'Ausilio, Alessandro; Pulvermüller, F.; Salmas, P.; Bufalari, I.; Begliomini, C.; Fadiga, Lucian

The role of the motor system in discriminating normal and degraded speech sounds

Listening to speech recruits a network of fronto-temporo-parietal cortical areas. Classical models consider anterior, motor, sites involved in speech production whereas posterior sites involved in comprehension. This functional segregation is more and more challenged by action-perception theories suggesting that brain circuits for speech articulation and speech perception are functionally interdependent. Recent studies report that speech listening elicits motor activities analogous to production. However, the motor system could be crucially recruited only under certain conditions that make speech discrimination hard. Here, by using event-related double-pulse transcranial magnetic stimulation (TMS) on lips and tongue motor areas, we show data suggesting that the motor system may play a role in noisy, but crucially not in noise-free environments, for the discrimination of speech signals