Mechanical damping of wood as related to species classification: a preliminary survey

International audienceSome morphological and biochemical taxonomic markers are also affecting factors of dynamic mechanical properties of wood. Thus, could these properties reflect the classification/phylogeny of taxa? This work is a first insight into this question. It relied on the gathering (through experimental campaigns and exhaustive literature review) of a large database on the viscoelastic (i.e. including damping) vibrational properties of 445 woody species. relationship between damping was confirmed at a wide interspecific scale, but described no more than 40% of not in a way that could be easily related to the phylogenetic tree. Damping was a bit more -Papilionoideae and, to a lesser extent, Lauraceae, Cupressaceae and Moraceae) damping than average, independently While for some other families no clear characteristics could be observed at least with the present number of represented species. In the future, increasing the amount of data and compiling anatomical and chemical markers / affecting factors will allow further analysis at sub-family levels, and a better understanding of this wide topic

Effect of extractives on vibrational properties of African Padauk (Pterocarpus soyauxii Taub.)

International audienceExtractives can affect vibrational properties tanδ (damping coefficient) and E'/ρ (specific Young's modulus) but this is highly dependent on species, compounds, and cellular locations. This paper investigates such effects for African Padauk (Pterocarpus soyauxii Taub.), a tropical hardwood with high extractives content and a preferred material for xylophones. 5 groups of 26 heartwood specimens with large, yet comparable, ranges in vibrational properties were extracted in different solvents. Changes in vibrational properties were set against yields of extracts and evaluation of their cellular location. Methanol (ME) reached most of compounds (13%), located about half in lumen and half in cell-wall. Water solubility was extremely low. tanδ and E'/ρ were very strongly related (R2≥0.93), but native wood had abnormally low values of tanδ, while extraction shifted this relation towards higher tanδ values. ME extracted heartwood became in agreement with the average of many species, and close to sapwood. Extractions increased tanδ as much as 60%, irrespective of minute moisture changes or of initial properties. Apparent E'/ρ was barely changed (+2% to -4%) but, after correcting the mass contribution of extracts, was in fact slightly reduced (down to -10% for high E'/ρ), and increasingly so for specimens with low initial values of E'/ρ

Vibrational properties of tropical woods with historical uses in musical instruments

This paper presents a collection of wood species with important uses in musical instruments, in reference to historical and geographical cultural specificities, with ranges of viscoelastic vibrational properties by species. Data combine our experimental characterizations and extensive literature review, gathered in a specific relational database. An overview of vibrational properties' distribution on c.400 species is introduced. Two case studies of wood choices for a given function in different epochs or regions are presented: woods for European historical bows, and woods for idiophone bodies in different continents. Trends are contrasted: very different properties associated to historical changes in the first case; some common features over different regions in the second one

Adsorption of Oxoanion onto Layered DoubleHydroxides

金沢大学大学院自然科学研究科Promoting Environmental Pesearch in Pan-Japan Sea Area : Young Researchers\u27 Network, Schedule: March 8-10,2006,Kanazawa Excel Hotel Tokyu, Japan, Organized by: Kanazawa University 21st-Century COE Program, Environmental Monitoring and Prediction of Long- & Short- Term Dynamics of Pan-Japan Sea Area ; IICRC(Ishikawa International Cooperation Research Centre), Sponsors : Japan Sea Research ; UNU-IAS(United Nations University Institute of Advanced Studies)+Ishikawa Prefecture Government ; City of Kanazaw

Characterisation and categorisation of the diversity in viscoelastic vibrational properties between 98 wood types

Context : Increased knowledge on diversity in wood properties would have implications both for fundamental research and for promoting a diversification of uses as material. Aims : The objective is to contribute to overcoming the critical lack of data on the diversity of wood dynamic mechanical/viscoelastic vibrational properties by testing lesser known species and categorising sources of variability. Methods : Air-dry axial specific dynamic modulus of elasticity (E′/γ) and damping coefficient (tanδ) were measured on a wide sampling (1,792 specimens) of 98 wood types from 79 species. An experimental device and protocol was designed for conducting systematic (i.e. rapid and reproducible) characterisations. Results : Diversity at the specimens' level corroborates the "standard” relationship between tanδ and E′/γ, which is discussed in terms of orientation of wood elements and of chemical composition. Diversity at the species level is expressed on the basis of results for normal heartwood, with specific gravity (γ) ranging from 0.2 to 1.3. Axial E′/γ ranges from 9 to 32GPa and tanδ from 4 × 10−3 to 19 × 10−3. Properties distribution follows a continuum, but with group characteristics. The lowest values of tanδ are only found in certain tropical hardwoods. Results can also suggest alternative species for musical instruments making. Conclusion : The variations in specific gravity, in stiffness or in "viscosity” appear to be predominantly linked to different levels of diversity: between species or between wood types (reaction wood or taxonomy-related differences in heartwood extractives

Identification of anisotropic vibrational properties of Padauk wood with interlocked grain

International audienceGrain deviations and high extractives content are common features of many tropical woods. We aimed at clarifying their respective impact on vibrational properties, referring to African Padauk (Pterocarpus soyauxii Taub.), a species selected for its interlocked grain, high extractives content, and uses in xylophones. Specimens were cut parallel to the trunk axis (L), and local variations in grain angle (GA), microfibril angle (MFA), specific Young's modulus (E'L/ρ, where r stands for specific gravity) and damping coefficient (tanδL), were measured. GA dependence was analyzed by a mechanical model which allowed to identify the specific Young's modulus (E'3/ρ) and shear modulus (G'/ρ) along the grain (3), as well as their corresponding damping coefficients (tanδ3, tanδG). This analysis was done for native and then for extracted wood. Interlocked grain resulted in 0-25° GA and in variations of a factor 2 in E'L/ρ and tanδL. Along the grain, Padauk wood was characterized, as compared to typical hardwoods, by a somewhat lower E'3/ρ and elastic anisotropy (E'/G'), due to a wide microfibril angle plus a small weight effect of extracts; and a very low tanδ3 and moderate damping anisotropy (tanδG/tanδ3). Extraction affected mechanical parameters in the order: tanδ3 ≈ tanδG > G'/ρ >> E'3/ρ. That is, extractives' effects were nearly isotropic on damping but clearly anisotropic on storage moduli

Robotic stepwise synthesis of hetero-multinuclear metal oxo clusters as single-molecule magnets

An efficient stepwise synthesis method for discovering new heteromultinuclear metal clusters using a robotic workflow is developed where numerous reaction conditions for constructing heteromultinuclear metal oxo clusters in polyoxometalates (POMs) were explored using a custom-built automated platform. As a result, new nonanuclear tetrametallic oxo clusters {FeMn4}Lu2A2 in TBA5[(A-α-SiW9O34)2FeMn4O2{Lu(acac)2}2A2] (IIA; A = Ag, Na, K; TBA = tetra-n-butylammonium; acac = acetylacetonate) were discovered by the installation of diamagnetic metal cations A+ into a paramagnetic {FeMn4}Lu2 unit in TBA7[(A-α-SiW9O34)2FeMn4O2{Lu(acac)2}2] (I). POMs IIA exhibited single-molecule magnet properties with the higher energy barriers for magnetization reversal (IIAg, 40.0 K; IINa, 40.3 K; IIK, 26.7 K) compared with that of the parent I (19.7 K). Importantly, these clusters with unique properties were constructed as designed by a step of the predictable sequential multistep reactions with the time-efficient platform

Characterisation and categorisation of the diversity in viscoelastic vibrational properties between 98 wood types

International audienceContext Increased knowledge on diversity in wood properties would have implications both for fundamental research and for promoting a diversification of uses as material. *Aims The objective is to contribute to overcoming the critical lack of data on the diversity of wood dynamic mechanical/viscoelastic vibrational properties, by testing lesser-known species and categorizing sources of variability. *Methods Air-dry axial specific dynamic modulus of elasticity (E'/γ) and damping coefficient (tanδ) were measured on a wide sampling (1792 specimens) of 98 wood types from 79 species. An experimental device and protocol was designed for conducting systematic (i.e. rapid and reproducible) characterizations. *Results Diversity at the specimens' level corroborates the "standard" relationship between tanδ and E'/γ, which is discussed in terms of orientation of wood elements and of chemical composition. Diversity at the species level is expressed on the basis of results for normal heartwood, with specific gravity (γ) ranging from 0.2 to 1.3. Axial E'/γ ranges from 9 to 32 GPa and tanδ from 4×10-3 to 19×10-3. Properties distribution follows a continuum, but with group characteristics. The lowest values of tanδ are only found in certain tropical hardwoods. Results can also suggest alternative species for musical instruments making

A human PSMB11 variant affects thymoproteasome processing and CD8+ T cell production

The Psmb11-encoded β5t subunit of the thymoproteasome, which is specifically expressed in cortical thymic epithelial cells (cTECs), is essential for the optimal positive selection of functionally competent CD8+ T cells in mice. Here, we report that a human genomic PSMB11 variation, which is detectable at an appreciable allele frequency in human populations, alters the β5t amino acid sequence that affects the processing of catalytically active β5t proteins. The introduction of this variation in the mouse genome revealed that the heterozygotes showed reduced β5t expression in cTECs and the homozygotes further exhibited reduction in the cellularity of CD8+ T cells. No severe health problems were noticed in many heterozygous and 5 homozygous human individuals. Long-term analysis of health status, particularly in the homozygotes, is expected to improve our understanding of the role of the thymoproteasome-dependent positive selection of CD8+ T cells in humans

ホルムアルデヒド処理によるパーティクルボードの寸法安定化

尿素 - ホルムアルデヒド (UF) 系, メラミン - ホルムアルデヒド (MF) 系, 及びフェノール - ホルムアルデヒド (PF) 系の3種類の樹脂接着剤を用いて作られた, 市販のパーティクルボードに対して, ホルムアルデヒド処理を適用し, 寸法安定性の改良を試みた。処理試片について, 寸法安定性, 吸湿性, 及び機械的性質を測定し, 他の木質材料との性能の比較を行った。その結果, 二酸化イオウを触媒とした, 120℃における24時間までの処理で, 厚さ膨潤率, 及び線膨潤率は, パーティクルボードの種類に関係なく, 反応時間とともに低下し, 抗膨潤能 (ASE) は厚さ方向で70%, 面方向で60%に達した。耐水性の低いUF系のボードでさえ, 冷水浸せきにおける寸法安定性は, UF系樹脂接着剤で作られた屋内用合板に匹敵する程度にまで向上した。膨潤の抑制効果は, 水浸せき時だけでなく, 繊維飽和点以下においても発現し, 平衡含水率は無処理の約半分にまで低下した。これらの結果は, 水分吸着性の低下がパーティクルボードの寸法安定化に大きく寄与していることを示す。常態の曲げ強さは, 70%のASEレベルで20 - 30%低下したが, 湿潤状態の曲げ強さは無処理とほとんど変わらず, また曲げ弾性係数は20 - 40%増大した。これに対して, 剥離強度の低下は, とくにUF系ボードにおいて深刻であった。A vapor phase treatment with formaldehyde (formalization) was applied to the dimensional stabilization of three types of commercial particleboard : urea-formaldehyde (UF), melamine-formaldehyde (MF), and phenol-formaldehyde (PF) types. Dimensional stability, hygroscopic property, and mechanical properties of the treated particleboard were compared with those of the other wood-based materials. By a sulfur dioxide catalyzed formalization up to 24hr at 120℃, thickness swelling and linear expansion decreased with reaction time irrespective of the types of particleboard. The antiswelling efficiency (ASE) reached 70 and 60% in thickness and linear directions, respectively. Even a low waterproofing UF type particleboard, the dimensional stability in water soaking at room temperature was enhanced to the same degree as that for UF type plywood. The restraint of swelling was revealed not only in water soaking state but also below fiber saturation point, and the equilibrium moisture content decreased to about a half of the untreated one. These results show that the decrease of moisture adsorptive property contributed effectively and largely to the dimensional stabilization of the particleboard. The modulus of rupture (MOR) in dry state decreased by 20 to 30% when ASE reached at the level of 70%, whereas the water saturated state MOR and the modulus of elasticity (MOE) was unchanged and increased by 20 to 40%, respectively. On the other hand, the loss of internal bond was much more serious than that of bending strength, especially in UF type particleboard