Surface finishes by mechanically induced wood surface fusion

Mechanically induced vibration wood fusion welding techniques can also be used to obtain wood surface finishes of increased surface hardness and performance in presence of polymerizing unsaturated oils such as sunflower oil, or other polymerizing finishes. Wood surface hardness values more than double than those for the untreated control timber can be obtained by this method. This result is obtained due to two effects induced by the sharp increase in temperature induced by the mechanical welding vibration (i) the polymerization to a hardened network of the unsaturated oil and (ii) the densification proven to occur in the surface layer of the timber during mechanically-induced vibration-welding. The first of these effects predominates at shorter welding times while at slightly longer welding times both effects occur with the second one progressively becoming the bigger contributor. In the latter case the some μm thin densified surface is a surface composite formed by the networked unsaturated oil permeating the wood fibre/fused lignin composite. © Springer-Verlag 2005

No association between fear of hypoglycemia and blood glucose variability in type 1 diabetes: The cross-sectional VARDIA study

AIMS: In type 1 diabetes (T1D), treatment efficacy is limited by the unpredictability of blood glucose results and glycemic variability (GV). Fear of Hypoglycemia (FOH) remains a major brake for insulin treatment optimization. We aimed to assess the association of GV with FOH in participants with T1D in an observational cross-sectional study performed in 9 French Diabetes Centres (NCT02790060). METHODS: Participants were T1D for ≥5 years, aged 18-75 years, on stable insulin therapy for ≥3 months. The coefficient of variation (CV) of blood glucose and mean amplitude of glycemic excursions (MAGE) were used to assess GV from 7-point self-monitoring of blood glucose (SMBG). FOH was assessed using the validated French version of the Hypoglycemia Fear Survey-II (HFS-II) questionnaire. RESULTS: Among a total of 570 recruited participants, 298 were suitable for analysis: 46% women, 58% on continuous subcutaneous insulin infusion [CSII], mean age 49 ± 16 years, HbA1c 7.5 ± 0.9%, HFS-II score 67 ± 18 and 12% with recent history of severe hypoglycemia during the previous 6 months, mean CV 39.8 ± 9.7% and MAGE 119 ± 42 mg/dL. CV and MAGE did not significantly correlate with HFS-II score (R = -0.05;P = 0.457 and R = 0.08;P = 0.170). Participants with severe hypoglycemia in the previous 6 months had higher HFS scores. Participants with higher HFS scores presented more hypoglycemias during follow-up. CONCLUSIONS: FOH as determined using the HFS-II questionnaire was not associated with 7-point SMBG variability in participants with T1D, but was associated with a positive history of severe hypoglycemia. Higher FOH was associated with higher frequency of hypoglycemia during follow-up

Tannin- caprolactam and Tannin- PEG formulations as outdoor wood preservatives: Weathering properties

International audienceAbstractKey messageThis article presents the leaching, fire and weathering resistance improvements of samples treated with tannin-based wood preservatives added of caprolactam. PEG-added formulations show limited applicability. The FT-IR and13C-NMR analyses of the caprolactam-added formulations show some evidences of copolymerization.ContextTannin-boron wood preservatives are known for their high resistance against leaching, biological attacks, fire as well as for the good mechanical properties that they impart to wood. These properties promoted these formulations for being a candidate for the protection of green buildings. However, the low elasticity of these polymers and their dark colour implied limited weathering resistances.AimsThe aim of the study is to find suitable additives for tannin-based formulations to overcome their limited weathering resistances, without compromising the other properties.MethodsTreatment, leaching and fire tests, dimensional stability as well as artificial and natural weathering of the timber treated with caprolactam-added and PEG-added formulations were performed. FT-IR and 13C-NMR of the formulations were presented.ResultsThe presence of caprolactam improved the properties of the formulation with particularly significant results in terms of resistance against leaching and dimensional stability. These enhancements were imparted also to the weathering resistance of the tannin-caprolactam formulations. Indeed, the colour changes during the artificial and natural exposures were stable for longer periods. FT-IR and 13C-NMR investigations of the advanced formulations were led, and covalent copolymerization of the caprolactam with the tannin-hexamine polymer was observed.ConclusionThe tannin formulations with caprolactam improved the durability of the wood specimens, while the PEG-tannin presented strong application drawbacks

High Temperature Oxidation of SiC under Helium with Low Oxygen Partial Pressure

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Parameters influencing wood-dowel welding by high-speed rotation

Oven-dry dowels, insertion of hot dowels, cross-cut dowels, substrate holes of stepdecreasing diameter as a function of depth, use of ethylene glycol or other compounds able to decrease the glass transition temperature of wood components have all been shown to contribute to improving weld joint strengths in a variety of less drastic conditions than the 10 mm/8 mm dowel/substrate hole diameter difference. The results show that once the depth of the dowel is much greater than 15 mm, then almost all the conditions used improve the weld strength. This means that the proportion of area welded in relation to the tensile strength of the dowel itself is a determining factor. The greater this area the higher the strength, irrespective of the application conditions used. Thus, over a certain welded area the dowel breaks when tested in tensile, i.e., the joint is stronger than the dowel. Temperatures > 180°C are reached during the quick welding step with the temperature decreasing in less than l min to 60-70°C. The same chemical reactions as occurring in vibrational welding have been shown by solid-state 13C-NMR analysis to also occur in dowel rotation welding. In dowel rotation welding the production of carbohydrate-derived furanic aldehydes is higher (a) from the wood material of the substrate in which the hole is pre-drilled rather than from the material of the wood dowel itself, (b) when the weld joint strength is good, and (c) when the rate of dowel insertion is highe

High temperature oxidation of SiC under helium with low-pressure oxygen—Part 1: Sintered α-SiC

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High temperature oxidation of SiC under helium with low-pressure oxygen. Part 3: β-SiC–SiC/PyC/SiC

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High temperature oxidation of SiC f /PyC/SiC composite in helium for the Gas-cooled Fast Reactor

International audienceThe cladding material envisaged for the Gas-cooled Fast Reactor (GFR) is a SiC f /PyC/SiC composite with a β-SiC coating on the surface that is subjected to temperatures going up to 1500 K in nominal operating condition and up to 2300 K in accidental operating conditions, in helium pressurized at 7 MPa. An experimental approach was made on SiC f /PyC/SiC under active oxidation conditions (1400 ≤ T ≤ 2300 K; 0.2 ≤ pO 2 ≤ 2 Pa). The variation of the mass loss rates according to the temperature showed the existence of three domains. The oxygen partial pressure had a weak impact on the mass loss rate for temperatures lower than 2070 K. Beyond 2070 K, the mass loss rate increased leading to important damage of the material, at lower temperature under pO 2 = 0.2 Pa than under pO 2 = 2 Pa, which was associated to the effect of the oxygen partial pressure on the sublimation of SiC

Characterization of DEF affected concretes: detection and modification of properties

International audienceThe evolutions of the different physicochemical and mechanical properties as a function of the expansion due to Delayed Ettringite Formation (DEF) in concrete are studied. In comparison of sound materials, some characterizations were made in accordance to the level of expansion: in the initial time, in the latent period, in the accelerating phase and at the end of expansion. The characterization was as follows; SEM analysis was used to observe the presence of DEF. Physical tests linked to transfer properties; gas permeability and electrical resistivity were measured to detect micro-cracks generated by the DEF advancement. To observe the impact of micro-cracks, compressive strength and static modulus were experimentally determined. It was observed that few tests can be used to detect theses pathologies earlier, during the latent period. Gas permeability, electrical resistivity and elastic modulus results were promising. These tests are very sensitive to the development of micro-cracks generated in the concrete by the development of swelling due to DEF