Volume 69, Issue 9

Taiwania ( Taiwania cryptomerioides Hayata) is a conifer species native to Taiwan, which is known for several bioactive secondary metabolites extracted from it. In this study, a sesquiterpene synthase ( TPS ) gene isolated from Taiwania was in focus. First, a pair of degenerate primers was designed for reverse transcription-polymerase chain reaction based on the total RNA extracted from the leaves of a mature tree. A DNA fragment with the conserved region of TPS gene was obtained. After 5′- and 3′-end amplification, the full-length gene was obtained, which contains an open reading frame of 1791 bp and encodes a predicted molecular mass of 70.2-kDa protein. The gene was highly expressed in young leaves, female flowers, and cones. The expression in leaves was enhanced by salicylic acid. To identify the function of TPS , the recombinant protein from Escherichia coli (Migula) Castellani & Chalmers was incubated with farnesyl diphosphate. Gas chromatography/mass spectrometry analysis and retention time as well as mass spectrum matching with authentic standards revealed that the major product of TPS is sesquiterpene α-gurjunene. The gene was, therefore, designated as Tc-Gur .

The behavior of Scots pine ( Pinus sylvestris L.) polysaccharides was studied during modified kraft pulping processes of wood meal by polysulfide (K-PS) and polysulfide anthraquinone (K-PSAQ) at the hydroxide ion concentrations of 0.50 and 1.55 M [OH - ] with a high liquor-to-wood (L/W) ratio of 200. The high L/W ratio was selected for avoiding diffusion phenomena and to be able to focus on the chemistry of polysaccharides. A comparison with the kraft process reference at 160°C revealed a substantial increase in pulp yield (6–7% in K-PS pulping and 7.5–10.5% in K-PSAQ pulping) mainly attributed to galactoglucomannan (GGM) stabilization. Due to the rapid delignification rate at 1.55 M [OH - ] concentration, the temperature could be lowered from 160°C to 130°C without a notable prolongation of cooking time. In K-PS pulping at 130°C, no additional GGM stability was observed compared to 160°C, whereas cellulose and arabinoxylan preservation was improved. In K-PSAQ pulping, GGM preservation was also significantly improved. At 130°C, pulp yield increase of approximately 8% in PS pulping and more than 11% in PSAQ pulping was observed. The amount of dissolved softwood hemicelluloses in black liquor was significantly increased at the higher [OH - ] level and even further in the presence of PS and AQ. Simultaneously, the formation of hydroxy acids was decreased, indicating a significant stabilization of the dissolved polysaccharide fraction parallel to the pulp polysaccharides.

To screen ionic liquid (IL) candidates for wood ionosolv pulping, swelling and viscoelastic studies on Norway spruce wood treated with ionic liquids have been conducted. In particular, the temperature dependency and kinetics of swelling in 1-butyl-3-methylimidazolium acesulfamate ([BMIM]Ace) and in 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc) were in focus. The kinetics of volumetric swelling in [BMIM]Ace yielded an E a of 54 kJ.mol -1 compared to 23 kJ.mol -1 in [EMIM]OAc. The viscoelastic behavior of IL-swollen wood was studied by dynamic mechanical analysis, and the lowest in situ glass transition temperature ( T g ) of lignin was ∼58°C and ∼65°C in [BMIM]Ace and in [EMIM]OAc, respectively. These T g values are lower than that found in water. Higher T g was calculated by the Gordon-Taylor equation, which means that swelling is not only due to the plasticizing effect of the ILs. SEM images showed that [EMIM]OAc has a stronger plasticizing effect than [BMIM]Ace. Overall, [EMIM]OAc is the most efficient agent for wood swelling, softening, and disintegration and, thus, it is the most promising candidate for ionosolv pulping.

In search of new potent bioactive compounds, a series of dehydroabietic acid-based thiadiazole-phosphonate compounds were designed and synthesized by the Mannich-type reaction. All target compounds were characterized by Fourier transform infrared, 1 H nuclear magnetic resonance (NMR), 13 C NMR, 31 P NMR, electrospray ionization-mass spectrometry, and UV-vis spectroscopy. The preliminary bioassay experiments showed that, at the concentration of 50 μg ml -1 , some of the target compounds exhibited excellent antifungal activity against the five fungi tested, in which several compounds displayed even better antifungal effects than the commercial antifungal drug azoxystrobin, which served as the positive control in this study.

Cellulose nanofibrils (NF) are usually produced by disintegration processes at low solids content (<5%). However, the high water content reduces the capacity of production, increases the transportation costs of NF suspensions and narrows the possible applications of NF. The goal of the present study was to test a grinding technique based on oscillatory ball milling. Bleached kraft pulp cellulose was nanofibrillated at high solids contents (≥50%), which was obtained from 2,2,6,6-tetramethylpiperidine-1-oxyl radical-oxidized pulp. The grinding method was only successful when the charge density was at least 0.5 mmol g -1 . NFs and cellulose nanocrystals were identified at a charge density of 1.1 mmol g -1 and a solids content of 50%. The size reduction of the formed particles was observed by means of flow fractionation and imaging and viscosity measurements after increasing the charge density from 0.3 to 1.1 mmol g -1 . A solids content increment and a charge density decrement resulted in particles with low aspect ratio rather than in nanofibrils. Wide angle X-ray diffraction measurements showed the transformation of crystalline cellulose into amorphous material in the case of grounding at 93% solids content.

Eleven different lignosulfonates (LS) and nine different free radical initiators have been tested in different concentrations to study the possibility of forming LS gels. It was found that the initiator must have a potential high enough for oxidizing the phenolic groups but not so high that would lead to a complete destruction of the LS. The chemical changes of the LS with different oxidants were observed in tests with low concentration of LS. The course of the reaction depends strongly on the type of oxidants that are able to gel the LS.

Lignin-based activated carbon fibers (ACFs) were prepared by electrospinning of hardwood acetic acid lignin (HW-AAL) solution followed by thermostabilization, carbonization, and steam activation. The thermostabilization process was able to be remarkably shortened from 38 h to 3 h with hexamethylenetetramine (hexamine) in binary solvents, AcOH/CCl 4 (8/2), when compared with conventional thermostabilization processes. The resultant ACFs possessed higher specific surface area (2185 m 2 g -1 ) than those from commercial activated carbon and electrospun lignin fibers without hexamine. These ACFs also exhibited good electrical capacitance (133.3 F g -1 at a current density of 1 A g -1 ) as electrodes of electric double layer capacitor (EDLC) are efficient not only due to their large surfaces area but also due to their porous structure with well-developed micropores (diameter: 0.5–1.3 nm). High energy density and power density of this EDLC (42 Wh kg -1 and 91 kW kg -1 , respectively) were also achieved.

The goal of the study is to investigate the non-standard deformation behaviour of wood loaded by compression parallel to the grain. This is represented as a negative increment of strain in the range of plastic deformations when the load continues to increase. The objectives of this study are to point out this problem and to provide its description based on the deformation fields that have been analysed using three approaches: a) full-field optical technique based on digital image correlation (DIC); b) “clip on” extensometer and its virtual analogy, and c) crosshead displacement method. Further, the negative strain phenomenon was studied depending on the sample length. The samples were made from the European beech ( Fagus sylvatica L.) and Norway spruce ( Picea abies L. Karst.). Based on the strain analysis, it can be concluded that the deformation field consists of three sub-regions exhibiting different stiffness values (three-spring model). The failure of less stiff zones near the compression plates during the “non-standard” compression behaviour causes almost zero compression deformation of the stiffer middle zone or even leads to its expansion. The three-zone heterogeneity of deformation field induces a deviation of the displacement and strain measured by the proposed approaches. This phenomenon substantially influences the resulting longitudinal Young’s modulus and, therefore, should be of concern when measuring wood in such mode.

Ground penetrating radar (GPR) is a handheld system showing good potential for the real-time and nondestructive characterization of wood moisture content (MC). However, measurements performed over logs can be challenging because of their curved surface that can affect the GPR signal. In this study, the MC of thawed and frozen logs was estimated for three species (quaking aspen, balsam poplar, and black spruce) using the full GPR signals and the partial least squares (PLS) regression method. The signal was acquired from the cross-section (CS) and through the bark (TB) of the logs with and without an aluminum plate placed under the log. The full GPR signal does not provide better log MC prediction accuracy for small logs compared with the early-time GPR signal. The information about the shape and diameter of the log is contained in the direct and reflected waves of the GPR signal. CS models provided more accurate log MC prediction (RMSE v =7–25%) than TB models (RMSE v =6–40%) for the hardwood species. Thawed and frozen log models showed similar performances. This study demonstrates that GPR in combination with PLS regression is suitable for predicting log MC in the field.

Log moisture content (MC) has been determined based on the propagation velocity (PV) of ground penetrating radar (GPR) signals. This approach is based on measuring the travel time of the GPR signal through the log, from which its PV and the apparent log dielectric permittivity can be retrieved. Linear regression between the log dielectric permittivity and MC was established for each of the investigated wood species (quaking aspen, balsam poplar, and black spruce), log state (thawed and frozen), and direction of measurement [on the log cross-section (CS) and through the bark (TB)]. CS and TB measurements led to different results depending on the log state and wood species. Linear models with different slopes were found for thawed (slope=6.4–9.8) and frozen (slope=12–29) logs due to the difference in the dielectric properties of the frozen and unfrozen water in wood. The models for quaking aspen and balsam poplar were very similar to each other and differed from that of black spruce in terms of slopes and intercepts. Generally, the PV method leads to poorer log MC prediction accuracy than the partial least squares method presented in Part 1 of this study.

An accurate, rapid, and convenient method is presented for moisture content (MC) determination of solid wood based on dual-energy X-ray absorptiometry (DXA). Poly(methyl methacrylate)-equivalent thicknesses (PMMA-EThs) of sugi ( Cryptomeria japonica D. Don) wood blocks and pure water were measured by means of a wide range of X-ray tube voltages (20–100 kV). The ratio of the PMMA-ETh of pure water to that of wood decreased as X-ray tube voltage was increased, suggesting that an appropriate pair of tube voltages for DXA is 20 and 100 kV. According to this result, X-ray images of 30 wood samples were taken at 20- and 100-kV tube voltages, and their average PMMA-Eths from both images was determined. There was a strong negative correlation between the wet-basis MC of the wood sample and the ratio of its PMMA-Eth at 100 kV to that at 20 kV. A regression equation was developed for estimating the dry-basis MC of wood samples from their PMMA-ETh ratios. The standard error of estimate was 2.2%, which is better than those determined for electric moisture meters. This approach may lead to the development of a practical, nondestructive moisture meter for wood.

A comparison of moisture loss from Pinus radiata sapwood by conventional forced air-drying and a novel supercritical carbon dioxide (scCO 2 ) dewatering process has been examined in situ using magnetic resonance microimaging. Air-drying results in the nonuniform removal of moisture within the wood volume, leading to a dry core and wet perimeter where water evaporated, whereas the scCO 2 dewatering process resulted in moisture expulsion more uniformly throughout the volume of the specimen, especially so within the earlywood.

Most studies on preservative depletion from treated wood are performed with small samples on a laboratory scale. Although these studies provided repeatable and constant test parameters, the results have little applicability to real conditions. Therefore, a series of laboratory tests were carried out according to CEN/TS 15119 part 1 and part 2 by means of EN 252 and non-standard sized Scots pine sapwood as well as spruce stakes. The stakes were impregnated by vacuum pressure with chromium (Cr)-copper(Cu)-containing wood preservative. For comparison, a set of 18 stakes per test parameter was installed at a test site (in ground use), whereby, every 4 months, three stakes from each series were removed for analysis. Both the time depending losses of metal as well as the remaining element contents were determined for samples exposed under lab conditions, whereas distribution and remaining element contents were measured for samples exposed in the field. The obtained data were evaluated regarding factors influencing the metal leaching, such as exposure time, wood species, or dimension. The results showed that wood species had a significant effect on the Cu depletion, while it had less influence on the Cr loss. Cr and Cu distribution in the standard and non-standard sized pine sapwood significantly changed as compared to spruce. In addition, comparison of the laboratory and field test results indicated that metal depletion is greater in field exposure compared to both laboratory tests.