Chemical composition of Norway spruce and pine, two softwood species, has been investigated by X-ray Photoelectron Spectroscopy (XPS). Contrary to results previously obtained with beech wood, which ...allow to obtain information on bulk chemical composition from surface composition analysis, XPS analysis appears to be unsuitable for the characterisation of Norway spruce and pine wood chemical composition. Indeed, chemical compositions calculated from XPS data differ strongly from those obtained from microanalyses which are in good agreement with theoretical composition described in the literature. XPS analysis of both the softwood surfaces indicated high carbon contents explained by migration of lipophilic extractives to the surface under the influence of the vacuum necessary for XPS analysis. Nonvolatile extractives contained in wood were extracted and deposited on glass plates and analysed. Survey and detailed C1s spectra indicated similar signals to those recorded on wood surfaces. This phenomenon was not observed when samples had been previously extracted before analysis. These results strongly evidenced that extractives present in both species are able to migrate through resin canals from the bulk of the sample to the surface when put into ultra high vacuum. XPS presents, therefore, some limits in the case of the analysis of softwood species containing extractives able to migrate to the surface during analysis. This behaviour, difficult to control, could lead to erroneous interpretations due to extractives enrichment of the surface under the effect of vacuum.
Wood heat treatment is an attractive alternative to improve decay resistance of wood species with low natural durability. However, this improvement of durability is realized at the expense of the ...mechanical resistance. Decay resistance and mechanical properties are strongly correlated to thermal degradation of wood cells wall components. Mass loss resulting from this degradation is a good indicator of treatment intensity and final treated wood properties. However, the introduction of a fast and accurate system for measuring this mass loss on an industrial scale is very difficult. Nowadays, many studies are conducted on the determination of control parameters which could be correlated with the treatment conditions and final heat treated wood quality such as decay resistance. The aim of this study is to investigate the relations between kinetics of temperature used during thermal treatment process representing heat treatment intensity, mass losses due to thermal degradation and conferred properties to heat treated wood. It might appear that relative area of treatment temperature curves is a good indicator of treatment intensity. Heat treatment with different treatment conditions (temperature-time) have been performed under vacuum, on four wood species (one hardwood and three softwoods) in order to obtain thermal degradation mass loses of 8, 10 and 12%. For each experiment, relative areas corresponding to temperature kinetics, mass loss, decay resistance and mechanical properties have been determined. Results highlight the statement that the temperature curves' area constitutes a good indicator in the prediction of needed treatment intensity, to obtain required wood durability and mechanical properties such as bending resistance and Brinell hardness.
The oxidation of soda lignin extracted from sugar cane bagasse was studied in acid medium. Soda lignin was precipitated from black liquor by adding (36N) sulphuric acid until the pH of the resultant ...solution was close to 2. The resultant, dried, material was oxidized using hydrogen peroxide. Soda lignin oxidized at different times was investigated by CHNS and EDX chemical analysis, GPC, FTIR and solid state CP-MAS
13C NMR spectroscopy. Oxidation increased the amount of carboxylic groups, while that of associated carbohydrates decreased. In addition, self-condensation with increase of molecular weight was observed.
Asperger's syndrome is a neurodevelopmental disorder which is part of the large family of autism spectrum disorders. People with Asperger's syndrome have difficulties in social interactions, verbal ...and non-verbal communication, and may display behavioural oddities, with stereotypies and limited interests. They show no language delay and their cognitive development is not marked by an overall delay but by specific impairments in certain areas such as the executive functions. The clinical presentations are very heterogeneous, varying according to age and psychiatric comorbidities. Screening, diagnosis and specialized treatment are not made any easier by the diversity of the clinical manifestations. Asperger's syndrome is often diagnosed belatedly, at 11years of age on average and even in adulthood in some cases. This late diagnosis has a significant impact on the risks of depression and a poor quality of life. However, in adulthood or in adolescence, certain situations, personality traits and cognitive profiles or certain comorbidities should suggest the hypothesis of an Asperger-type autism spectrum disorder. We propose here a review of the clinical situations at different ages of life that could help with the screening and the referral of patients to specialized clinicians for diagnosis and appropriate treatment.
Aim To determine which prediabetes definition is the best predictor of progression to diabetes in Reunion Island where 10% of the population has treated diabetes.
Methods This follow-up study used ...data from the REDIA cross-sectional study, a population-based study conducted in two stages. Participants were enrolled in 1999–2001 (REDIA-1) and followed-up years later in 2006–2009 (REDIA-2). Odds ratios (OR) for prediabetes were estimated with their 95% confidence interval (95%CI) from logistic regression models. REDIA-1 participants with no previously identified diabetes in REDIA-1 were assessed for new pharmacologically treated diabetes in REDIA-2. We evaluated several biological definitions of prediabetes, each based on the combination of fasting plasma glucose (FPG), 2-h post-load plasma glucose (2hPG), and/or HbA1c: FPG-ADA (American Diabetes Association), FPG-WHO (World Health Organization), 2hPG, HbA1c-ADA, HbA1c-IEC (International Expert Committee), FPG-WHO/2hPG, and FPG-WHO/HbA1c-ADA.
Results A total of 432 participants met all inclusion criteria. Of these, 102 (23.6%) were classified as prediabetic using the FPG-WHO/2hPG definition, including 58 (56.9%) with isolated impaired glucose tolerance, 17 (16.6%) with isolated impaired fasting glucose, and 27 (26.5%) with both impairments. A total of 54 (12.5%) participants became treated diabetics and in descending order, the ORs for the FPG-WHO/2hPG, 2hPG, FPG-WHO, FPG-WHO/HbA1c-ADA, FPG-ADA, HbA1c-ADA, and HbA1c-IEC definitions were 6.96 3.72–13.03, 5.91 3.24–10.77, 5.82 2.86–11.81, 4.68 2.38–9.19, 4.37 2.34–8.17, 3.24 1.72–6.10, and 2.74 1.32–5.70, respectively.
Conclusion The FPG-WHO/2hPG definition had the highest strength of association with the progression to treated diabetes, closely followed by the 2hPG and FPG-WHO definitions. Our findings highlight the importance of performing both FPG test and OGTT to diagnose prediabetes in primary care.
Effect of heat treatment on extracellular enzymes involved in wood degradation by Trametes versicolor was investigated. Heat-treated and untreated beech blocks were exposed to T. versicolor on ...malt-agar medium and extracellular enzymatic activities investigated. A strong ABTS oxidizing activity has been detected during the first stage of colonization in both cases, while cellulase activities are mainly detected in the case of untreated beech wood. Further investigations carried out on holocellulose, isolated using sodium chlorite delignification procedure and subjected to heat treatment or not, indicate that commercially available cellulases and xylanases are able to hydrolyse untreated holocellulose, while heat-treated holocellulose was not affected. All these data suggest that chemical modifications of wood components during heat treatment disturb enzymatic system involved in wood degradation.
Wettability of Heat-Treated Wood Pétrissans, M.; Gérardin, P.; bakali, I. El ...
Holzforschung,
01/2003, Letnik:
57, Številka:
3
Journal Article
Recenzirano
The aim of this work was to study the wettability and chemical composition of heat-treated wood. Heat treatment was performed at 240°C under inert atmosphere on four European wood species (pine, ...spruce, beech and poplar). Contact angle measurements before and after treatment indicated a significant increase in wood hydrophobicity. Advancing contact angles of a water drop were in all cases systematically higher for heat-treated than for untreated wood. Chemical modifications of wood after heat treatment were investigated using FTIR and 13C NMR analysis. FTIR spectra indicated little structural change which could be attributed either to carbon-carbon double bond formation or to adsorbed water. NMR spectra also revealed little chemical change except for the degree of cellulose crystallinity which was considerably higher in heat-treated wood and could explain the higher contact angles.
Le chikungunya chez l'enfant Gérardin, P.
Archives de pédiatrie : organe officiel de la Société française de pédiatrie,
20/May , Letnik:
22, Številka:
5
Journal Article
PDF
