A kinetic study on the thermal behaviour of chitosan

Abstract The thermal behaviour of chitosan was studied by means of thermogravimetry, mass spectrometry and infrared spectrometry. Kinetic parameters were obtained by advanced kinetic evaluation (differential isoconversional analysis) from DSC curves, in non-isothermal conditions, at several heating rates, between 5 and 30°C min−1. The results showed that the decomposition of chitosan does not follow a single mechanism because both the activation energy and the pre-exponential factor are not constant during the course of the reaction. A comparison with the results obtained by applying different conventional calculating methods is also shown.Peer reviewe

Breathing in karate kokyo technique in static imagetic and in motor performance in children of different graduations between 6 and 15 years of age

No karaté o movimento está em estreita articulação com um fluxo respiratório diafragmático controlado. Como a respiração diafragmática ativa o sistema nervoso parassimpático e reduz a frequência respiratória (CR), fomos verificar se crianças e jovens de diferentes graduações de karaté revelavam alteração na CR e na variabilidade da frequência cardíaca (VFC), nas condições de imagética estática (I) e de execução motora (E) da técnica kokyo. Os anos de prática e os anos de competição em Katas revelaram associação direta com a potência de baixa frequência, indicadora de VFC (rho=,614, p=,025; rho=,581, p=,038, respetivamente), podendo indicar que é possível que crianças integrem a respiração na execução do kokyo. A frequência de treino semanal associou-se inversamente com CR (rho=-,584, p=,036) e diretamente com LF (rho=,581, p=,038), na condição E, pelo que deve ser importante para a articulação entre respiração e movimento nestes níveis de formação. Como nos indicadores de VFC e para CR não se encontrou associação entre as condições I e E, é provável que o recurso à imagética, só por si, não propicie sincronização de respiração e movimento no kokyo em crianças, mas permitiu evidenciar o efeito agudo da respiração no aumento da VFC. A análise dos CR e da VFC permitiu apreciar a efetiva capacidade de ajustamento da respiração ao movimento na execução do kokyo nestas crianças.In karate the movement is in close articulation with a controlled diaphragmatic respiratory flow. As diaphragmatic breathing activates the parasympathetic nervous system and reduces the respiratory rate (CR), we checked whether children of different karate graduations showed changes in CR and heart rate variability (HRV), in the conditions of static imagery (I) and motor execution (E) of the kokyo technique. Years of practice and years of competition in Katas revealed a direct association with low frequency, an HRV indicator ((rho=,614, p=,025; rho=,581, p=,038, respectively), which may indicate that it is possible for children to integrate breathing in the performance of kokyo. The weekly training frequency was inversely associated with CR (rho=-,584, p=,036) and directly with LF (rho=,581, p=,038), in condition E, so it must be important for the articulation between breathing and movement in these training levels. As no association was found between conditions I and E in the HRV and CR indicators, it is likely that the use of imagery alone does not provide synchronization of breathing and movement in kokyo in children, but allowed to highlight the acute effect of breathing on the HRV increase. The analysis of CR and HRV made it possible to assess the effective ability to adjust breathing and movement in the performance of kokyo in these children.info:eu-repo/semantics/publishedVersio

Characterisation of microbial attack on archaeological bone

As part of an EU funded project to investigate the factors influencing bone preservation in the archaeological record, more than 250 bones from 41 archaeological sites in five countries spanning four climatic regions were studied for diagenetic alteration. Sites were selected to cover a range of environmental conditions and archaeological contexts. Microscopic and physical (mercury intrusion porosimetry) analyses of these bones revealed that the majority (68%) had suffered microbial attack. Furthermore, significant differences were found between animal and human bone in both the state of preservation and the type of microbial attack present. These differences in preservation might result from differences in early taphonomy of the bones. © 2003 Elsevier Science Ltd. All rights reserved