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<jats:title>Abstract</jats:title><jats:p>Mechanical joints with screws or bolts are widely employed in timber structures and are known to provide high toughness. However, they result in low stiffness, which is a representative limitation of wood structural joints. In this study, we investigated the mechanical properties of hybrid joints comprising mechanical and adhesive joints, to prevent the decrease in stiffness while maintaining high toughness. Wood and steel plates were joined with screws and adhesives, and their stiffness, bearing capacity, and fracture energy were evaluated by lap-shear tests. We inferred that the stiffness and bearing capacity of the hybrid joints change with the type of adhesive used, while the fracture energy primarily depends on the diameter of the screws. Interestingly, when the adhesive strength was too large, a decrease in the fracture energy was observed because the precursory rupture of the adhesive joint triggered the wood failure in the fastened regions and lead to the early pull-out of the screws. To suppress such decrease and early pull-out, an adhesive fillet, i.e., the coating of the adhesive onto a larger area than that of the steel plate, was investigated. Accordingly, we successfully improved the toughness. Our results suggest the importance of optimal designs for the hybrid joint in timber structures.</jats:p>

<jats:title>Abstract</jats:title><jats:p>People seem to function and feel better in indoor natural environments, including spaces furnished with wood. When restorative effects of indoor spaces are not detected, suboptimal methodological approaches may be responsible, including stress-inducing activities and measures of affective states and cognitive performance. Our primary objectives were to test (1) whether the Mental Arithmetic Task (MAT) can reliably induce stress and measure cognitive performance, and (2) whether two single-item measures of pleasure and arousal can detect changes in affective states in restoration research. Our secondary objective was to examine whether stress recovery and cognitive performance differ between indoor settings furnished with or without wood. Twenty-two participants, allocated to a space furnished with either a wooden or a white desktop, completed MAT twice, while their electrodermal and cardiovascular activity and affective states were monitored. Participants on average responded to MAT with increased subjective arousal but unchanged subjective pleasure, and with increased physiological arousal on some but not all parameters, suggesting that MAT was effortful but not necessarily stressful. Scores on MAT improved at the 2nd administration, suggesting that MAT did not induce cognitive fatigue at the 1st administration and that its role as a cognitive task in restoration research may be limited. The items assessing affective states performed well. The measured outcomes did not differ between the wooden and non-wooden setting, suggesting that substantial restorative effects of a wooden desktop are unlikely, and that higher wood coverage is needed to increase the chances of observing restorative effects.</jats:p>

<jats:title>Abstract</jats:title><jats:p>This paper describes results and analysis of experiment of compression behavior parallel to grain of glulam (Norway Spruce, Japanese cedar, and Japanese cypress), especially in damage zones near loading plates and joints. To investigate the influence factors of physical properties and the mechanism of the damage zone near the loading plates or the joints, compression tests on 90 specimens and surface-measurement tests on 48 specimens were performed. As a result, it was observed that damage zones existed near the loading plates and the joints. The lengths of the damage zone of wood–wood joints are larger than that of wood–steel joints. The length of the damage zone was independent of the load and the height of the specimens. However, the length of the damage zone and its scatter increase as the width of the cross-section increases, as does the roughness on the contact surface. It was considered that the cause of the damage zone is the roughness on the contact surface and the length of the damage zone depends on the roughness on the contact surface. Therefore, the length of the damage zone depends on the processing accuracy on the contact surface and has an increasing trend as the contact-surface area increases. There was the size effect of the height of the specimens on the compressive strength because of knots.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Borate solution was used to treat two sets of Douglas-fir wood samples, one by spraying cross-laminated timbers (CLT) and another set by dip-treating wood in solutions at different retentions. A novel model was developed to explain and predict borate uptake based on dip-treatment parameters. Small-scale CLT samples were prepared using commercial emulsion polymer isocyanate (EPI) and polyurethane (PU) adhesive with dip-treated wood. The effect of adhesive and borate retention on CLT samples were evaluated through adhesion, fire, termite, and decay tests. The adhesion strength of wood was statistically unaffected by borate treatment. Statistical analysis showed that both spray- and dip-treated samples had significantly higher termite and decay resistance and fire performance than the untreated boards. Untreated CLT samples bonded with PU showed a considerably higher inherent decay and termite resistance than untreated specimens bonded with EPI adhesive.</jats:p>

<jats:title>Abstract</jats:title><jats:p>The mechanical performance of bolt joints in wooden structures is known to vary significantly with the initial tightening force (axial force) of the bolts during the construction work. When a joining method that considers axial force is applied to a structure, the control of the axial force is important. This study attempts to evaluate the elastic stiffness of bolted timber joints during tightening for the purpose of applying the turn-of-nut tightening method, one of the methods for controlling axial force. Considering the elastic stiffness of joints during tightening as a series spring model using the spring constant of the bolt and the embedment spring constant of the washer, elastic stiffness is calculated using the washer embedment spring constant obtained through a washer embedment test. This result is compared with the elastic stiffness obtained through the tightening test using four species of timber. It was found that while the washer embedment spring constant varies greatly with timber species, the calculated values agreed well with the test results.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Balsa (<jats:italic>Ochroma pyramidale</jats:italic>), which is the lowest density wood, is a useful species in various industries. In general, balsa can be divided into three types (low density: LD, middle density: MD, high density: HD). In this study, we classified the porosities of the three balsa types into through-pore porosity, blind-pore porosity, and closed-pore porosity. As a result, the total porosity of balsa showed a high positive (+) correlation with closed-pore porosity, but total porosity of balsa showed negative (−) correlations with blind-pore porosity and through-pore porosity. Such information can be useful when using balsa as a natural porous material.</jats:p>

<jats:title>Abstract</jats:title><jats:p>The application of citric acid and glycerol as natural binder was investigated for the manufacturing of jute stick particleboard in this study. The effects of citric acid content (0–30 wt%), citric acid and glycerol mixture (ratio of CA–G), and pressing temperatures on the properties of jute stick particleboard were investigated. Citric acid-bonded jute stick particleboard had good mechanical properties and dimensional stability when citric acid concentration was 20 wt% at pressing temperature of 200 °C. By addition of glycerol concentration (40/60), the properties were further increased. The modulus of rupture (MOR) and thickness swelling (TS) values of CA–G (40/60) bonded jute stick particleboard were 19.67 N/mm<jats:sup>2</jats:sup> and 9%, respectively, which satisfy the minimum requirement for type-18 of particleboard JIS A 5908 (2003). FTIR analysis confirmed the formation of ester linkage by polymerization reaction between carboxyl groups and alcohol groups. Citric acid and glycerol polymer reacted with jute stick particles and produced cross-linked networks with enhanced properties, hence improved the adhesiveness during particleboard production. It could be concluded that citric acid and glycerol mixture can be a potential natural binder for the production of jute stick particleboard. </jats:p>

<jats:title>Abstract</jats:title><jats:p>In the present study, crystalline cellulose biomass material was converted into carbon nanoparticles via carbonization to activated carbon with micropores of various sizes. This was subsequently subjected to aqueous counter collision (ACC) to produce hydrophobic porous functional particles. Initially, raw crystalline cellulose material was carbonized into activated carbon materials with various pore distributions prior to ACC. Pore distribution depended on the activation time, and was confirmed by nitrogen (N<jats:sub>2</jats:sub>) adsorption isotherms. The surface areas and pore volumes of carbon activated for 8 h were larger than those of carbon activated for 2 h. When they were subjected to ACC, the width and length of the carbon particles decreased as the number of pulverizing cycles during the ACC treatment increased. Eventually, carbon nanoparticles of 70 nm width that had improved dispersibility and stability were produced. The diameters of the carbon nanoparticles and their dispersibility were dependent on the pore distribution and surface areas of the activated carbon subjected to the ACC treatment. The ACC process facilitated the preparation of carbon nanoparticles from activated carbon derived from biomass, and is, therefore, an important strategy for the sustainable production of a sought-after and valuable resource.</jats:p>

<jats:title>Abstract</jats:title><jats:p>There is increasing interests in the significant improvement of impregnation amount and efficiency in wood by the pre-treatment of compression. Thus, attention is paid to pre-treatment by compression for harder impregnation with resin because of the large viscosity and relatively large molecular weight of the resin. Low-molecular-weight phenol formaldehyde (PF) resin of solid content of 10–48% were impregnated by pre-treatment of compression at a compression ratio of 60% and 40% for poplar and Chinese fir, respectively, to systematically study the effects of solid content on the impregnation amount, weight gain percentage (WGP). In addition, the distribution of resin in wood was analyzed by profile density and was observed by confocal laser scanning microscope (CLSM), and the change of crystallinity index (C<jats:sub>r</jats:sub>I) of resin-impregnated wood was investigated by X-ray diffractometer. The results showed: (1) compared with immersion impregnation without compression, the impregnation by pre-treatment of compression, was much larger in amount and higher in efficiency for resins in all solid contents. In a solid content range of 10–48% and at a molecular weight of about 517, there was no significant difference of impregnation amount by compression among the resins at different solid content. (2) The WGP of poplar and Chinese fir increased with the increase of resin solid content. When the resin solid content increased from 10 to 48%, the WGP increased from 8.9 to 44.2% and from 5.2 to 24.9% for poplar and Chinese fir, respectively. (3) Resin is mainly distributed in vessels and tracheids despite a few being distributed in the fiber near the longitudinal end of the poplar specimens. With the increase of solid content, the resin distribution gradually changed from diffusing on the wall to depositing in the vessel or tracheid, while the resin distribution evenness along the longitudinal direction decreased. There was more resin deposited near the longitudinal end of Chinese fir at deeper depth than that of poplar. (4) The resin can be impregnated into the amorphous area of wood without causing any change in the crystallization area. The C<jats:sub>r</jats:sub>I decreases with the increase of resin solid content. After all, it is concluded that the pre-treatment by compression for wood impregnation with low-molecular-weight PF resin is effective for all the solid contents for both poplar and Chinese fir. The WGP increased with the increase of resin solid content, despite the decrease of evenness of resin distribution at high solid content.</jats:p>

<jats:title>Abstract</jats:title><jats:p>In a previous study, we reported a transient transformation system using repeated screening for hygromycin B (Hyg) resistance in the basidiomycete <jats:italic>Ceriporiopsis subvermispora</jats:italic>. In the present study, by combining this technique with CRISPR/Cas9, we demonstrated successful marker-free genome editing in <jats:italic>Pleurotus ostreatus</jats:italic>, which is one of the most economically important cultivated mushrooms as well as a model white-rot fungus. At first, transformant selection mediated by the transient expression of marker genes was demonstrated using a plasmid harboring the Hyg resistance gene (<jats:italic>hph</jats:italic>) in <jats:italic>P. ostreatus</jats:italic>. Then, genome editing of <jats:italic>fcy1</jats:italic>, which confers 5-fluorocytosine (5-FC) resistance to the host cell, was performed by the transient expression of Cas9, gRNA, and <jats:italic>hph</jats:italic> and strains with 5-FC resistance and Hyg sensitivity were isolated. Additionally, genome editing of <jats:italic>fcy1</jats:italic> in these strains was confirmed by Sanger sequencing. To our knowledge, this is the first report of marker-free genome editing through the transient expression of Cas9, gRNA, and <jats:italic>hph</jats:italic> in agaricomycetes, which opens the door for repeated genome editing in these fungi.</jats:p>