ヤシ植物繊維維管束の解剖学的ならびに力学的特徴に関する研究

京都大学0048新制・課程博士博士(農学)甲第17904号農博第2027号新制||農||1018(附属図書館)学位論文||H25||N4800(農学部図書室)30724京都大学大学院農学研究科森林科学専攻(主査)教授 杉山 淳司, 教授 矢野 浩之, 教授 髙部 圭司学位規則第4条第1項該当Doctor of Agricultural ScienceKyoto UniversityDFA

ANATOMICAL AND MECHANICAL CHARACTERISTICS OF LEAF-SHEATH FIBROVASCULAR BUNDLES IN PALMS

This study presents anatomical characteristics, mechanical properties, microfibril angles (MFAs) and Klason lignin contents of leaf-sheath fibrovascular bundles from 14 palm genera (18 species). Observed by light microscopy, all fibrovascular bundles consisted equally of thick-walled sclerenchyma fibers and vascular tissue, while the shape and localization of vascular tissues on the transverse sections varied among species. It was possible to group these fibrovascular bundles into 3 types based on the vascular tissue’s differences: type A – rounded in the central region; type B – angular in the marginal region; and type C – aliform in the central region. These three anatomical types of fibrovascular bundles showed some correlation with a current phylogenetic classification of palm species. Through mechanical tests, this research confirmed the correlation between diameter and mechanical properties of the fibrovascular bundles of palms; tensile strength and Young’s modulus showed a decreasing trend with increasing diameter. We clarified that this trend was due to a marked increase in the proportion of transverse sectional area comprised by vascular tissue with increasing diameter of fibrovascular bundles. The MFAs of fibrovascular bundles ranged from 10.3º to 47.1º, which were generally larger than those of non-woody plants, conifers, and broad-leaved trees. The Klason lignin contents of palm species were also high, ranging from 18.3% to 37.8%, with a mean value of 29.6%. These large MFAs and high lignin contents could lead to the long-term plastic deformation and relatively low tensile strength of palm fibrovascular bundles

Anisotropic Cellulose Nanofibers/Polyvinyl Alcohol/Graphene Aerogels Fabricated by Directional Freeze-drying as Effective Oil Adsorbents

Under the current situation of frequent oil spills, the development of green and recyclable high-efficiency oil-absorbing aerogel materials has attracted wide attention from researchers. In this study, we report a high-strength, three-dimensional hydrophobic cellulose nanofiber (CNF)/polyvinyl alcohol (PVA)/graphene oxide (GO) composite aerogel with an anisotropic porous structure, which was fabricated by directional freeze-drying technology using anisotropically grown ice crystals as a template, followed by hydrophobic treatment with a simple dip coating process. The prepared composite aerogel presented anisotropic multi-level pore microstructures, low density (17.95 mg/cm3) and high porosity (98.8%), good hydrophobicity (water contact angle of 142°) and great adsorption capacity (oil absorption reaching 96 times its own weight). More importantly, the oriented aerogel had high strength, whose compressive stress at 80% strain reached 0.22 MPa and could bear more than 22,123 times its own weight without deformation. Therefore, the CNF/PVA/GO composite aerogel prepared by a simple and easy-to-operate directional freeze-drying method is a promising absorbent for oil-water separation

Automated identification of Lauraceae by scale-invariant feature transform

An image dataset of the cross-sectional optical micrographs of the Lauraceae species including 39 species in 11 genera, capturing at least one full annual ring, was investigated by scale-invariant feature transform (SIFT), a computer vision-based feature extraction algorithm. We found an image of 900 × 900-pixel size at a pixel resolution of ca. 3 µm, corresponding to the actual size of 2.65 × 2.65 mm2, as the minimum requirement for the image dataset in terms of the accuracy of the recognition at both the genus and species levels. Among the several classifiers investigated, the linear discriminant analysis (LDA) presented the best performance reaching a maximum of 89.4 % in the genus with a species identification of approximately 96.3%. Cluster analysis of all the SIFT descriptors for each image yielded practical information regarding the descriptors; they recognize selectively the cell lumina, cell corners, vessels, and axial and ray parenchyma cells. Therefore, the difference between the genus or species levels was determined per the variation in the quantities of these computer-based properties. Another clustering approach, the hierarchal dendrogram, was applied to visualize the numerical distances between the genus and species. Interestingly, even Machilus and Phoebe, which are difficult to distinguish by conventional visual inspection, are quite distantly classified at the genus level. In contrast, some species in Cinnmamomum, Machilus and Litsea were categorized into different subgroups rather than the original genus. Microscopic wood identification is found to be possible at the genus level; however, the numerical dataset of the morphological features has various overlapping clusters, causing the genus-level identification of the Lauraceae to be more difficult than species-level identification

Defects and Their Elemental Distributions in a Crept Co-Al-W-Ti-Ta Single Crystal Superalloy

The structure of defects and their elemental distributions is the decisive factor to metal’s mechanical properties. The γ/γ′ structure Co-Al-W-based superalloy is a potential replicable alloy to Ni-based superalloys that have been used for a long time. Revealing the microstructure of a defect induced by high-temperature crept provides direct clues for the alloy development. Our work revealed the high-resolution, high-angle annular dark field images and corresponding elemental distributions on crept defects. Defects in the γ phase mainly contain dislocation networks, while the γ′ phase contains lots of stacking faults and anti-phase boundaries. The results indicate that dislocation networks and stacking faults contain more weight elements than the base γ′ phase, while anti-phase boundaries contain more light elements. Disclosing atomic structure and its elemental distributions gives direct evidence for alloy design and further high-temperature mechanical improvement

木材情報学と教育用材鑑調査室デジタルデータベース(XDD_009)

Magnoliaceae; Optical micrograph; 2 genus 18 species 37 individuals 926 images; actual area: 2.7x2.7 mm2; image size 600x600 pixel; resolution 4.44 µm/pixelモクレン科; 木材標本光学顕微鏡写真; 2属18種37個体 926画像； 観察領域 2.7 x 2.7 mm2; 画像サイズ　600x600 ピクセル; 解像度 4.44マイクロメーター/ピクセ

木材情報学と教育用材鑑調査室デジタルデータベース(XDD_014)

Ulmaceae; Optical micrograph; 2 genus 4 species 38 individuals 443 images; actual area: 2.7x2.7 mm2; image size 900x900 pixel; resolution 2.96 µm/pixelニレ科; 木材標本光学顕微鏡写真; 2属4種38個体 443画像； 観察領域 2.7 x 2.7 mm2; 画像サイズ　900x900 ピクセル; 解像度 2.96マイクロメーター/ピクセ