VIBRATIONAL SPECTRA OF H2O3H_{2} O_{3} AND H2O4H_{2} O_{4} MOLECULES TRAPPED IN FROZEN H2O−H2O2H_{2}O-H_{2}O_{2} MATRIX

Author Institution: Centre de Recherches sur les Atomes et les Mol\'{e}cules, University LavalThe infrared and laser Raman spectra of the glassy material condensed at liquid nitrogen temperature from electrically dissociated water vapor show some new bands in the $400-900 cm^{-1}$ region. These have been identified as $O- O$ vibrations by means of $O^{13}$ isotope shifts. Temperature and composition effects indicate that more than one new species is involved. One of them has a half-life of some five hours at -$-65^\circ C$. The new spectra are ascribed to stabilized $H_{2}O_{3}$ and $H_{2}O_{4}$ molecules trapped in low concentration (some 5 mole %) in that material. The observed frequencies are suitable for $O- O$ stretching and bending modes of zigzag chain structures linked by single bonds, as in the hydrogen polysulfides

Thermomechanical analysis of Aminoplast adhesive with wood

The evolution of the viscosity of amino resin adhesives in presence of wood was studied by thermomechanical analysis(TMA). After application of the adhesives on the surface of wood at ambient temperature, their viscosity increases considerably, due to the evaporation of water and absorption of water and small molecules by wood. When the temperature increases, the viscosity of MPUF adhesive decreases until the polymerization begins. Addition of hardener modifies the rheological behaviour and lowers the temperature of polymerization of MPUF adhesiveL'évolution de la viscosité des colle aminoplastes en présence de bois a été étudiée par analyse thermomécanique(TMA). A la surface de bois, la viscosité des colles augmente considérablement immédiatement après encollage à la température ambiante, par suite de l'évaporation de l'eau et de l'absorption de l'eau et des molécules de bas poids moléculaire par le bois. Lorsque la température augmente, la viscosité de la colle MPUF diminue jusqu'au commencement de la polymérisation qui se traduit par une très forte augmentation de la viscosité. L'ajout de durcisseur modifie le comportement rhéologique et abaisse la température de polymérisation de la colle MPU

Modifications de la couleur du bois d'Abies grandis exposé à la lumière solaire

Le principal effet du rayonnement solaire sur le bois d'Abies grandis est une modification de sa couleur. On peut quantifier cette modification grâce au système CIE-LAB mais pour comprendre ce phénomène, une analyse de l'évolution des spectres d'absorption infrarouge et UV-visible est nécessaire. Les bandes d'absorption infrarouge ont pu être attribuées aux groupements chimiques présents en surface du bois. On note en cours d'irradiation, une diminution des groupements hydroxyles, une augmentation des groupements carbonyles et une désaromatisation. La lignine présente les mêmes évolutions de bandes que le bois d'Abies grandis. Ces évolutions sont sensibles à la présence d'oxygène. Les modifications dues au rayonnement ultraviolet sont plus importantes que celles produites par la lumière visible. L'observation des spectres UV-visible permet de suivre le jaunissement du bois d'Abies grandis. En début d'irradiation, la vitesse de jaunissement semble indépendante de l'atmosphère gazeuse. Le jaunissement est surtout imputable aux longueurs d'onde du domaine ultraviolet. Les modifications de couleur induites par l'exposition au rayonnement sont attribuées à la photodégradation de la lignine. L'absorption, directe ou indirecte, de l'énergie lumineuse par la lignine entraînerait la formation d'un radical gaiacoxy coloré qui produirait des dérivés quinoniques colorés en présence d'oxygène ou des produits incolores en absence d'oxygène.Wood photodiscolouration of Abies grandis under solar light exposure. In the present study, the effect of the solar-type irradiation was investigated by focusing mainly on fir (Abies grandis) discolouration. The CIE-LAB system was used for colour change measurements (table II, fig 3) and spectrometric methods such as infrared (IR) and ultraviolet visible (UV), were utilized to determine the mechanism. All the IR absorption bands were assigned to the different chemical groups of the wood surface (table IV). The absorption changes occurring during the solar-type exposure showed a decrease in the hydroxyl groups, an increase in the carbonyls and also desaromatization (table VII, fig 8). These changes were oxygen-dependent (fig 9). By cutting the UV or visible light emitted by the lamp with filters, it was possible to show that UV wavelengths were more important in the IR spectral modification (fig 10). Also, lignin photodegradation was similar in spectral evolution to fir degradation under solar-type irradiation. UV-visible spectroscopy was used to characterize the evolution of yellowing in fir, mainly due to the UV wavelengths (fig 13). At the beginning of light exposure, the yellowing rate seemed to be independent of the gaseous atmosphere. Lignin seemed to be responsible for the light absorption of wood and for discolouration (fig 15), and the main source of radicals. These gaiacoxy radicals appear to form coloured quinonoid structures with oxygen, and colourless products without it (fig 19)

Dynamic thermomechanical analysis as a control technique for thermoset bonding of wood joints

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Modification de couleur du bois de chênes européens exposés à la lumière solaire

L'étude du comportement photochimique du bois d'Abies grandis caractérisé par la quasi-absence de substances extractibles colorées, a permis d'établir un modèle mécanistique capable de rendre compte à l'échelle moléculaire des modifications de couleur du bois exposé à une lumière de type solaire. Ce modèle a été étendu au bois de chênes européens (Quercus robur et petraea), essences riches en substances extractibles colorées et pour lesquelles les caractéristiques de couleur sont un critère de qualité. En plus du jaunissement observé et analysé sur le bois d'Abies grandis, un éclaircissement correspondant à une diminution de l'absorption sur le domaine spectral 500 à 600 nm a été noté. Cette décoloration a pu être imputée, au moins en partie, à la photodégradation des lignines.Wood photodiscoloration of European oak under solar light exposure. A previous study concerning the photochemistry of Abies grandis wood, a species which is characterized by the very low content of colored extractable substances, has made it possible to establish a mechanical model (fig 22) to take into account the discoloration of wood under solar-type light exposure at the molecular level. In this paper, this model was extended to European species of oak (Quercus robur and petraea) with high levels of colored extractable substances and for which the color characteristics are a quality criterion. In addition to the observed and analyzed yellowing in Abies grandis wood, a color lightening corresponding to a lowered absorption over the spectral range (500-600 nm) (figs 2, 6) has been observed. Lignin photodegradation is certainly in part responsible for this decoloration. It has also been shown that oak sapwood and heartwood undergo different kinds of photodecoloration (fig 3). For color photostabilization of oak wood under solar light, the results indicate that it is necessary to use UV absorbers to lower the yellowing due to UV light and antioxidants to inhibit color lightening due to reactions with oxygen

Stent graft exclusion of a ruptured mycotic popliteal pseudoaneurysm complicating sternoclavicular joint infection.

A mycotic pseudoaneurysm of the popliteal artery is usually a consequence of septic embolization and often a result of bacterial endocarditis. Conventional treatment is surgical and avoids the placement of foreign material in infected sites. Here we report our treatment of a 59-year-old man who presented with a rupture of a mycotic pseudoaneurysm of the popliteal artery due to septic embolism from sternoclavicular infectious arthritis. Radiological investigations are included. This is the first documented case of septic arthritis complicated by a rupture of a mycotic popliteal false aneurysm and treated using an endovascular procedure. Combining endovascular stent grafts with evacuation of the joint abscess and antibiotic therapy can offer a safe alternative for frail and unstable patients

Pyrolyse-flash de déchets ligno-cellulosiques en vue de leur valorisation par l'énergie solaire concentrée

The purpose of this paper is to propose a method for the valorization of wood wastes by flash pyrolysis and use of concentrated solar energy. An experimental study has been made between 700 and 1 000 °C with Douglas pine sawdust in electric and image furnace (similar conditions to a solar concentrator). In these conditions, we obtain CO and H2 rich gaseous mixtures with non negligible proportions of light hydrocarbons and with gasification yields up to 80 %. The energetical and chemical values of the gas are emphasized.On propose un procédé de valorisation de déchets de bois par pyrolyse flash grâce à l'énergie solaire concentrée. Une étude expérimentale est effectuée entre 700 et 1 000 °C avec de la sciure de pin Douglas au four électrique et au four à image dans des conditions voisines d'un concentrateur solaire. Il est possible, dans ces conditions, de produire avec des rendements atteignant 80 %, des mélanges gazeux riches en carbone monoxyde et hydrogène avec des proportions non négligeables d'hydrocarbures légers. On discute de l'intérêt du gaz sur les plans chimique et énergétique

Physical methods for characterizing wood composite panel products

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A new approach in the treatment of high flow native AV fistula: the open-pore external scaffolding prosthesis

Objective: The vascular access steal syndrome is a complication occurring in 1-6% after native arterio-venous (AV) fistulas, often due to huge diameter of the vein. This results in very high flow, which could also be responsible for cardiac overload. The aim of this study is to evaluate the efficiency of a new approach in the treatment of this pathology using open-pore external scaffolding prosthesis.Methods: This a retrospective review of all patients presenting symptomatic high flow after native AV fistula between January 2007 and December 2009 in 3 vascular centers. Pre-operative duplex exam confirmed the diagnosis of high flow. The operation consisted in preparation of the whole fistula, measurement of the flow and section on the venous side. The vein was wrapped with this 6 to 8 mm open-pore external scaffolding prosthesis (ProVena, BBraun, Germany) according to its diameter and to the flow and then sutured. Measurement of the flow was repeated. Patients were followed by duplex exam at 1 week and at 1, 3, 6 and 12 months. Procedural success was defined as complete implantation of the prosthesis and reduction of the flow. Primary outcomes were reduction of the flow and recovery of the symptoms and secondary endpoint was patency of the fistula.Results: During the study period, 14 patients, with a mean age of 65・8 years old, have been operated with this technique.There were 2 native forearmfistulas and 12 on the armwith a mean pre-operative flow of 2600 ml/min (1800-3800). The mode of presentation was pain in 6 patients, neurological disorders in 10 and necrosis in 4. Moreover, 3 patients had cardiac insufficiency due to high flow in the fistula. The procedure was technically successful in 100% of cases. Re-intervention was necessary in 2 patients due to hematoma. Recovery of the initial symptoms occurred in 13 patients (93%). The mean flow reduction was 1200 ml/min (600-2000). In 1 patient, a persistent steal syndrome despite flow reduction to 1400 ml/min resulted in fistula closure 2 months later. At a mean follow-up of 22 months (4-35), all remaining patients (13/14) presented a patent fistula without recurrence.Conclusion: This new approach seems to be safe and effective in the treatment of symptomatic high flow native AV fistulas by significantly reducing the flow and avoiding closure of the vascular access. Longer follow-up with more patients are necessary to evaluate the risk of recurrence