Volume 18 Issue 1

This study aimed to determine the insecticidal effectiveness of commercial fast- and slow-acting termiticides against Reticulitermes speratus by observing the changes in its activity patterns over time. Both the Petri dish and planar arena methods were used to evaluate colony mortality and activity changes over time associated with each termiticide, and the evaluation methods were compared. A colony elimination pattern was observed weekly in R. speratus colonies that ingested fast- or slow-acting termiticides using the planar arena method; however, the results showed that the Petri dish method was not suitable for evaluating slow-acting termiticides with an insecticidal effect that appeared after 3 weeks or more. In the colony-level evaluation, using the planar arena method, termites that ingested fipronil bait became sublethal within 1 week and died inside the 2 m plastic tube connected to the bait feeding site. The dead termites accumulated in the plastic tube and blocked access to the bait feeding site. In contrast, termites that ingested bait treated with bistrifluron or hexaflumuron during the first 3 weeks of the experiment spread throughout the colony. Decreased colony activity and immune mechanism collapse were observed in all screens and subnests, and more than 95% of termites in the colony had died after 10 weeks.

To gain insight into the mechanical properties of crushed sugarcane tail leaves during stress relaxation, a self-made compression equipment was used in this study. The variation law of different factors on the stress relaxation process of crushed cane tail was explored and a stress relaxation model was established. The three-element and five-element generalized Maxwell models were selected to fit the regression analysis of the stress relaxation curve of the crushed cane tail. The comparison showed that the determination coefficient R2 of the five-element stress relaxation model was higher, and a three-factor and three-level response surface test was designed. Following the quadratic regression polynomial of the stress rapid decay time and the equilibrium elastic modulus, the final optimization results obtained are as follows: The moisture content was 60.8%, the crushing particle size was 45 mm, the feeding amount was 150 g, and the stress rapid decay time was 14.0 s. The equilibrium elastic modulus was 129 kPa.

A cellulose ether that is easier to melt than benzyl cellulose was produced from the lignin degradation product veratryl alcohol. Veratryl chloride and bromide were synthesized from the alcohol, and these two chemicals were used to react with Avicel® cellulose to form the novel cellulose ether veratryl cellulose (VC). Spectroscopic characterisation techniques (1H NMR, FTIR) indicated the successful conversion of Avicel® cellulose to the cellulose ether VC, by both routes, at a degree of substitution of 1.4 to 1.6. Melting measurements of the VC samples showed a gradual softening from approximately 110 °C; the VC was melted below 200 °C. XRD analysis confirmed that the chemical treatments affect the degree of crystallinity. Size exclusion chromatography results showed that the products differ remarkably in molecular weight. The VC synthesized with veratryl chloride degraded almost twice as much as when veratryl bromide were used. The cellulose ethers were soluble in DMSO, DMAc, and CHCl3.

The effect of crack length on the fracture behavior of particleboard was investigated using the single-edge-notched bending (SENB) test method under mode I loading. The initial slope (kinit), critical stress intensity factor (KIC), specific fracture energy (Gf), and brittleness number were calculated for five different crack length/specimen width (a/W) ratios varying from 0.1 to 0.9 at intervals of 0.2. The results show that the fracture properties were significantly higher for specimens with an a/W ratio of 0.1 than for the others. However, for the critical stress intensity factor and specific fracture energy, there were no significant differences among the a/W ratios of 0.3, 0.5, and 0.7 where the crack tip was placed in the core layer of the particleboard. In general, as the a/W ratio decreased, the stiffness of the material increased, and the specimens with an a/W ratio of 0.1 showed brittle behavior. However, there was no statistically significant difference between a/W ratios of 0.5 and 0.7.

Molecular dynamics simulation was used to better understand a single, non-crystalline cellulose molecular chain and its response to high-temperature treatment. The system temperature was varied from 430 K to 510 K, and the temperature interval was 20 K. Under the polymer consistent force field (PCFF), the dynamics simulation of each temperature was completed under the constant pressure/constant temperature dynamics (NPT). The experimental results showed that the mechanical properties of cellulose heat-treated at high temperature in a vacuum environment initially increased and then decreased with the increase of temperature. When the temperature was at 450 K, the mechanical properties reached an optimal state. Moreover, its mechanical properties were noticeably related to the connection of hydrogen bonds in the cellulose molecular chain and the thermal motion of the molecular chain.

Fly ash was modified using calcium oxide and carbon dioxide. The morphology of precipitated calcium carbonate was controlled by adding different crystal-shape-forming additives. Effects of sodium hexametaphosphate, zinc chloride, sodium tetraborate decahydrate, and aluminium chloride on the crystal shape of precipitated calcium carbonate were studied. The effects of crystal-shaped additives of precipitated calcium on the whiteness of modified fly ash and hand sheets were analyzed. The results showed that the addition of ZnCl₂ (0.35%) can play a role in coating fly ash well. The coating effect of the acicular, chain, and lamellar precipitated calcium carbonate on the surface of fly ash was slightly less effective than that of globular crystals.

Modern solid wood armchairs are developing in the direction of simplicity and lightness, and favored by the market. However, the low mechanical strength of the connecting joint of cantilevered handrails is an issue that needs to be improved. In this study, the armrest joints of a cantilever armchair made by beech (Fagus orientalis Lipsky) were examined. To improve the mechanical strength of handrail joints, three novel joints were proposed including dovetail tenon, cross-stepped tenon, and rear plug corner tenon. The finite element analysis (FEA) was used to compare and analyze the five joints to obtain the optimal joint. Finally, experimental tests were conducted to verify the results of the FEA. The novel cross-stepped tenon had better mechanical performance, i.e., bending moment capacity and stiffness, than other joints evaluated. The maximum load of the novel cross-stepped tenon was greater than that of the commonly used tenon. In conclusion, the cross-stepped tenon was most suitable for cantilevered handrail joint of chair. This study will contribute to the structural design of modern solid wooden chairs.

Nitrogen (N) is a major limiting factor for improvement in grain production. The return of straw to the soil (straw return) is regarded as a very effective option to develop sustainable agriculture. Soil N content could be increased by the straw return because straw itself contains some nitrogen. However, whether N retention could be increased by the straw return is worthy of further study. In the present study, a laboratory simulative incubation experiment was conducted to study the effects of straw addition on N leaching from soil. The experimental results showed that the pH values in soil with time were changed slightly with different straw application, there was no notable change in relative abundance of microbial taxa of different straw application in soil at domain level, and the EC of the soil did not show any clear trends after straw incorporation. The highest EC in the soil was 0.18 ds/m occurred with straw addition of 0.3%. Moreover, the N leaching amounts from soil with different straw application were decreased over time, the higher the amount of straw added in soil, the greater content of N leaching from the soil.

Furfural produced during lignocellulose pretreatment to reduce the recalcitrance inhibits the growth of Saccharomyces cerevisiae and reduces ethanol yield. To reduce the adverse effect of furfural on S. cerevisiae, exogenous ergosterol was supplemented and the impact on S. cerevisiae under furfural stress was studied. The lag phage was shortened by 50%, and the maximum ethanol yield was increased by 158% with 50 mg/L ergosterol supplementation under 4 g/L furfural stress. Flow cytometry analysis results showed that permeable cells and intracellular reactive oxygen species were decreased by 45 and 53%, respectively with the addition of ergosterol under furfural stress. The fatty acid composition of S. cerevisiae was changed; the intracellular glycerol and ergosterol content was increased after ergosterol supplementation. The saturation of fatty acid was increased. Addition of ergosterol promoted cell growth by decreasing oxidative stress. Under 4 g/L furfural stress, the lag phage of S. cerevisiae BY4741 (erg3△) and S. cerevisiae BY4741 (erg5△) was longer than that of S. cerevisiae BY4741, and the maximum ethanol concentration was decreased.

Using cotton pulp fibers as raw material, through composite enzymolysis and purification, two different forms of high-purity cellulose nanocrystals were obtained, namely spherical CNCs (SCNCs) and rod-like CNCs (RCNCs). Vacuum filtration was used to obtain pure SCNCs film and pure RCNCs film. The films were characterized by scanning electron microscopy, ultraviolet–visible spectrometry, and X-ray diffraction and tested for their mechanical properties. The films were shown to have good light transmittance and softness, and the structures were unchanged compared with the cellulose raw materials. This article mainly introduces the preparation process of high-purity cellulose nanocrystals films and provides data support for subsequent research.