Search

Low-molar ratio UF resin was used in bonding veneers of five wood species. Significantly different bonding strengths were observed among the used wood species. Much higher bonding strengths were found for cherry, sapele mahogany and black walnut, which would be attributed to their natural roughness that allows formation of more mechanical interlockings. After 60s Gliding Arc Discharge (GAD) plasma treatment of wood surface, the wet bonding performance was significantly improved for most of the wood species. The SEM images of wood surface indicated that the roughening, micrometer-scale peeling or etching effects of GAD plasma treatment would be related to the improved bonding performance. XPS characterizations showed that plasma treatment resulted in remarkable increase of O/C ratio for all wood species. Detailed analysis of C1s spectra revealed that drastic oxidation induced by plasma generated high content of oxygen-containing groups, while degradation led to exposure of more oxygen-containing components like cellulose and hemicellulose. In contrast to untreated surface, stronger interactions can be formed between highly polar wood surface and UF resin. GAD plasma appeared to be an efficient tool in both physical and chemical modifications of wood surface. [ABSTRACT FROM AUTHOR]

Soil aggregates and associated carbon (C) and nitrogen (N) stocks are important for soil organic matter (SOM) consequences and quality. The study is meant to understand the mechanisms of how fertilization management affects Cand Nstocks. Tobacco monocropping systems with four fertilizer treatments (0, 75, and 112kg Nha−1, and 60kg Nha−1 + manure) were established in 1998. After 19 years, crop monocrop and fertilization management redetermined soil aggregates and related indicators. The results showed the large aggregates proportion (LMP) and small macroaggregates proportion (SMP) varied inversely with changing season. The LMP gradually rose after the implementation of tillage while microaggregates gradually declined. By manure fertilizer, LMP and SMP were significantly higher than those in inorganic fertilizer treatments, while microaggregates proportion (MIP) and silt and clay proportion (SCP) were lower than in inorganic fertilizer treatments. Soil water-stable aggregate and their associated soil organic stocks are changed with growing season, and tillage practices would have potentially affected these indicators, while the proportion and soil organic stocks more quickly recovered in large aggregates by manure application. Therefore, the proper application of manure combined with chemical fertilizer would maintain soil quality in tobacco cultivation. [ABSTRACT FROM AUTHOR]

Tobacco leaves are flue-cured to create desired appearance and internal quality, but the effects of flue-curing on transformation of chemical substances in tobacco have not been fully studied. The half-leaf method and a mass balance approach were used to compare two drying methods (i.e., oven-drying and flue-curing) in terms of chemical substances in tobacco. These substances included: carbon, nitrogen, plastid pigments, and polyphenols and some important elements in tobacco leaves. Compared with oven-drying, starch content significantly decreased while saccharides (including total sugar, glucose, fructose, maltose, and sucrose) increased in flue-cured tobacco leaves. There was only numerical change in reducing-sugar content between two drying methods. Protein, total nitrogen, and nicotine content in flue-cured tobacco leaves significantly decreased compared to oven drying. Two important elements (potassium and chlorine) showed no significant change. Compared with oven-drying, four plastid pigments (lutein, chlorophyll A, chlorophyll B, β-carotene) significantly decreased and six polyphenol substances (neochlorogenic acid, chlorogenic acid, caffeic acid, chrysatropic acid, rutin, kaempferol) significantly increased. This research clarified the transformation mechanisms of chemical substances after flue-curing of tobacco leaves, which provides a reference for the transformation and an insight into the procedures to study flue-cured tobacco leaf processing. [ABSTRACT FROM AUTHOR]