Mikiji Shigematsu

Compressive-molding of wood by high-pressure steam-treatment : Part 1. Development of compressively molded squares from thinnings

We attempted to compressive-mold logs of sugi (Cryptomeria japonica D.Don) to squares, and to permanently fix the transformed shape. The transformation and fixation were successively conducted under high-temperature saturated steam atmosphere by a newly designed apparatus which was a combined pressure vessel and a press machine. The results are summarized as follows: (1) The logs were successively softened by steaming at 150°C, compressively molded to square, and fixed the transformed shape by steaming at 200°C in this apparatus. (2) The shape of square fixed by high-pressure steam-treatment did not recover to original log shape by water-soaking and boiling. The result shows that the high-pressure steaming is effective for permanent fixation of the transformed shape. (3) The condition for sufficient fixation of the compressive transformation was steaming at 220°C for 3min when a 15 cm of diameter and 10cm of length sugi-thinning was used as a specimen. (4) Inner stress within a compressed wood was gradually reduced during steaming and. finally, the stress was removed completely.

Compressive-molding of wood by high-pressure steam-treatment : Part 2. Mechanism of permanent fixation

Permanent fixation of the compressively transformed shape of Harigiri (Kalopanax pictus Nakai) specimens was attempted by steaming them, compressively transforming their shapes, and processing them with high-pressure steam again. Also, the mechanism of the shape fixation was examined. The results are summarized as follows: (1) Compressively transformed Harigiri specimens, after being processed with high-pressure steam, did not recover to their original shape with heat and moisture, thus achieving permanent fixation of compressed shape. (2) The conditions under which the fixed specimens would not recover to their original shape were found to be steaming with saturated steam at 200°C for 4min or longer or at 180°C for 8min or longer, within the scope of the current experiment. (3) Hemicellulose and lignin do not affect the fixation of compressive transformation. (4) The fixation of compressive transformation is caused by a structural change of cellulose. (5) The mechanism of fixation of compressive transformation is supposed to be that the inner stress is released because the paracrystalline region of cellulose, which is distorted by compressive transformation, is partially hydrolyzed. Further, steam-rearrangement of hydrolyzed constituent into crystalline region occurs, keeping the transformed shape intact.

Substituent effects of 3,5-disubstituted p-coumaryl alcohols on their oxidation using horseradish peroxidase–H2O2 as the oxidant

The consumption rates of three monolignols (p-coumaryl, coniferyl, and sinapyl alcohols) and eight analogues using horseradish peroxidase (HRP)–H2O2 as an oxidant were measured and compared with the anodic peak potentials thereof measured with cyclic voltammetry. 3-Monosubstituted p-coumaryl alcohols, i.e., 3-methoxy-, 3-ethoxy-, 3-n-propoxy-, and 3-n-butoxy-p-coumaryl alcohols, had faster reaction rates than p-coumaryl alcohol. This is most probably due to the electron-donating effect of alkoxyl groups. However, the reaction rates gradually decreased with an increase in the molecular weight of the alkoxyl groups. Furthermore, t-butoxyl group, which is a very bulky substituent, caused an extreme reduction in the reaction rate, even though its electron-donating effect was almost the same as that of other alkoxyl groups. The reaction rates of 3,5-disubstituted p-coumaryl alcohols, especially 3,5-dimethyl-p-coumaryl alcohol, were very low compared with 3-monosubstituted p-coumaryl alcohols. These results suggest that there are three main factors of hindrance during the approach of monolignols to the active site of HRP. First, from the results of 3-monoalkoxy-p-coumaryl alcohols, it was suggested that the volume of substituents could decrease their oxidation rates. Second, from the results of 3,5-disubstituted p-coumaryl alcohols, it was suggested that local steric hindrance by the amino residues quite near the heme decreased the oxidation rates. Third, from the results of the substrates with hydrophobic substituents at their 3,5-positions, we suggested that hydrophilicity near heme would decrease their oxidation rates.

Solvent effects on the electronic state of monolignol radicals as predicted by molecular orbital calculations

The spin and charge densities in three monolignol radicals were computed using the UB3LYP/6-31G* method of molecular orbital calculation. As well, the effects of solvents were simulated by using an SCI-PCM model. It was confirmed that an unpaired electron was localized at C1, C3, C5, C8, and O4 for all monolignol radicals. In solvents, the spin density decreased at O4 with increasing solvent polarity, but increased at C8. The atomic charges at all reactive atoms had a negative value and were obviously strengthened at O4 with increasing solvent polarity. These tendencies support the experimental results for radical coupling reactions of monolignols in various solvents; that is, that 8-O4′ linkages are produced much more often than 8-8′ linkages in nonpolar solvents.

Transition state leading to β-O′ quinonemethide intermediate of p -coumaryl alcohol analyzed by semi-empirical molecular orbital calculation

The radical coupling reaction leading to the β-0′ quinonemethide intermediate of p-coumaryl alcohol was analyzed by semi-empirical molecular orbital calculation with MOPAC2002. By analyzing the radical monomer in a one-electron oxidation, the spin density of the unpaired electron at the 4-oxygen was less than half of the values at the C1, C3, C5, and Cβ positions. By analyzing the transition state during the radical coupling reaction, the activation enthalpy was evaluated as 9.76 kcal/mol, which corresponds to the activation energies for the propagation of common vinyl polymers. From the analysis of atomic interactions in the transition state, it was found that the activation enthalpy was largely composed of a high coulombic repulsion between Cβ of the first monomer and the phenolic oxygen of the second monomer. After passing the transition state, the two radical monomers formed a metastable quinone-methide intermediate. The optimum conformation of the quinonemethide intermediate was formed from the meta-stable conformation through a second transition state with a small energy barrier.

Stopped-flow kinetic study on aggregation of dilauroylphosphatidic acid vesicles induced by divalent cations

Abstract Aggregation kinetics of dilauroylphosphatidic acid (DLPA) vesicles induced by divalent cations (Mg 2+ , Ca 2+ , Sr 2+ , and Ba 2+ ) was studied by a stopped-flow rapid mixing technique with turbidity detection. The aggregation rate was evaluated in terms of the initial velocity of turbidity increase, V 0 . With the increase of cation concentrations above a threshold, V 0 increased and reached a maximum value, V 0,max . No significant difference in the relation between V 0 and the cation concentration was observed among the divalent-cation species. The threshold concentration and the concentration at which V 0,max is attained were independent of the lipid concentration. From the temperature dependence of V 0,max ; the activation energy for the aggregation was estimated to be 3.9 kcal/mole, which corresponds to the activation energy for the diffusion-controlled reaction in aqueous media. These experimental results for the divalentcation-induced aggregation of DLPA vesicles are well explained on the basis of the Derjaguin-Landau-Verwey-Overbeek theory for electrically stabilized colloids.

A pressure and temperature study on solubility and micelle formation of sodium perfluorodecanoate in aqueous solution

Both the critical solution temperature (CST, or the Krafft temperature) and the critical solution pressure (CSP, or the Tanaka pressure) were determined for sodium perfluorodecanoate (NaPFDe) in water, and the result shows that the Krafft temperature is raised with the increase in the Tanaka pressure. A thermodynamic analysis has been made on the data for the critical micellization concentration (cmc) and of the solubility at various temperatures and pressures. The estimated change in the partial molal volume, resulting from micelle formation from the singly dispersed state and from the hydrated solid state, was found to be conspicuously higher for NaPFDe compared to hydrocarbon surfactants. This has been ascribed to the more pronounced role of carbon chain-water interactions and water structure effects of the fluorocarbon surfactants.

Abnormal aggregation behavior of acidic phospholipid vesicles in the very low concentration range of divalent cations

Abstract Aggregation behavior of dilauroylphosphatidic acid (DLPA) vesicles was investigated in the presence of divalent cations (Mg2+, Ca2+, Ba2+, and Cd2+) at extremely low concentration range (below 1 mM). Ca2+ induced the vesicle aggregation, which starts after an induction period of several hours. The induction period was shortened by the increase of Ca2+ concentration to 0.15 mM, above which it disappeared. The size of aggregates formed by the vesicle aggregation showed a bell-shaped dependence on Ca2+ concentration below 0.05 mM; it also depended on both lipid concentration and cationic species. These experimental findings suggest that the aggregation of DLPA vesicles occurring at low concentration range of divalent cations proceeds by the intervesicular salt-linkage mechanism rather than by the Derjanguin-Landau-Verwey-Overbeek mechanism.

Conformational Study of α‐N‐Acetyl‐D‐Neuraminic Acid by Density Functional Theory

The stable structures of α‐N‐acetyl‐D‐neuraminic acid (Neu5Acα) in the gas phase were studied at the B3LYP level of theory using 6‐31G(d,p) and 6‐31++G(d,p) basis sets. They are classified into five types according to the patterns of the intramolecular hydrogen bond formations. One of the stable structures had intramolecular hydrogen bond network of O9HO9 … O8HO8 … O˭C1‐O1HO1 and O7HO7…O˭CHN‐C5 similar to the crystal structure of Neu5Ac‐α‐methyl glycoside methyl ester. The stable structures of Neu5Acα are reasonable for the following sialooligosaccharide ligand studies with respect to the relationship between OH group orientations and intramolecular hydrogen bond formations. The barrier heights for isomerizations between the stable structures were computed to be 2.8 to 6.7 kcal/mol at the B3LYP/6‐31++G(d,p)//B3LYP/6‐31G(d,p) level, which are basic factors for the conformational behavior of Neu5Acα before its interactions with receptors. We also calculated Neu5Acα–4 or 5‐water complexes to take account of the solvent effect on the intramolecular hydrogen bonds in the stable structures. Consequently, the structures of Neu5Acα in the complexes are similar to each other, which is consistent with the known NMR data. Thus, the optimum Neu5Acα‐water complexes are some of the reasonable pseudohydrous Neu5Acα.

Improvement of oxidation stability of biodiesel by an antioxidant component contained in spent coffee grounds

ABSTRACT In this work, biodiesel was produced from spent coffee grounds (SCG) oil extracted using n-hexane as a non-polar solvent, and acetone and 1-butanol as polar solvents, in order to simultaneously obtain SCG oil and antioxidant component. Moreover, oxidation stability and antioxidant capacity of SCG oil and their biodiesel production process were evaluated using the Rancimat method and oxygen radical absorbance capacity (ORAC) method, respectively. ORAC values of SCG oil from polar solvents and a non-polar solvent were 97–98 and 93–386 μmol-TE/g, respectively. Antioxidant activities of SCG oils from polar solvents were higher than those of SCG oil from non-polar solvent. However, these ORAC values were decreased by one third on raw oils during biodiesel production model experimental. These characteristics were utilized to develop an improved method of producing waste rapeseed biodiesel: (1) blending the SCG oil with rapeseed oil; (2) soaking powdered SCG in the reaction mixture during biodiesel production; and (3) adding active components extracted using methanol. In method (1), oxidation stability was improved such that 10 wt% of polar solvent extracted SCG oils increased the stability from 1 to 3 h. Also, oxidation stabilities in methods (2) and (3) were improved by soaking 40 wt% SCG and adding 1 wt% SCG extract, respectively.