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排序方式： 共有157条查询结果，搜索用时 15 毫秒
151.
Delignification rate expressions for neutral sulfite semichemical (NSSC) and neutral sulfite semichemical anthraquinone (NSSC-AQ) pulping of black spruce have been developed. The rates take into account the effects of temperature and reaction times on the rates of delignification. NSSC in this study is defined by an alkali ratio [sodium sulfite/(sodium sulfite + sodium carbonate)] of 0.60 (expressed as sodium oxide) giving a final pulp yield between 55 and 60%. NSSC-AQ is identical to NSSC with the addition of anthraquinone. Reaction temperature and pulping chemical concentrations were held essentially constant in all kinetic experiments. Isothermal experiments were conducted in the temperature range between 165 and 180°C. A concentration of 150 g/L sodium sulfite with a liquor to wood ratio 62 were used. 相似文献
152.
Ceren Tabak Serhat Keskin Tughan Akbasak Guralp Ozkoc 《Polymer Engineering and Science》2020,60(2):352-361
In this study, the spray dried nanofibrillated cellulose (NFC) was modified by a silane coupling agent to be used in polypropylene (PP)-copolymer matrix in the presence of maleic anhydride grafted PP (PP-g-MAH) compatibilizer. The PP/NFC composites were melt compounded and injection molded. In the first stage, the NFC was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). It was shown that fibrillation in aqueous media through high-pressure homogenization was successfully achieved. The nanofibrils having diameter smaller than 50 nm were obtained. The X-ray photo electron spectroscopy (XPS) showed the presence of the silane groups on the NFC surface. Elastic modulus improved by the addition of the high modulus NFC to PP, but the yield strength was not improved. On the other hand, different than many inorganic micron-sized fillers, the elongation-at-break value did not drop much. Differential scanning calorimeter experiments indicated that the NFC acted as a nucleating agent. Rheological investigations exhibited that NFC decreased the viscosity of the PP. The addition of NFC to PP improved the thermal resistance of the PP as can be understood from the TGA experiments. It was demonstrated that renewable nanofiller can be a feasible method to functionalize the existing synthetic polymers. POLYM. ENG. SCI., 60: 352–361, 2019. © 2019 Society of Plastics Engineers 相似文献
153.
Polyvinyl alcohol (PVA) electrospun nanofibers and boric acid (BA) complexes of these nanofibers were synthesized with and without using TritonX-100(TX-100) as a water soluble surfactant (PVA, PVA/BA, PVA/TX-100, PVA/TX-100/BA). The electrospun nanofibers were characterized by SEM, FTIR and TGA. Preliminary results showed that certain amount of boric acid decreased the number of Stapylococcus aureus from 6,8x107(CFU/mL) to 3x107(CFU/mL). In the preparation of polymer, boric acid was used as a crosslinker and antimicrobial agent whereas TX-100 was used as surfactant. The viscosity and conductivity measurements indicated that the BA increased viscosity but decreased conductivity. In contrast, TX-100 increased conductivity without considerable effect on viscosity, which affects the production and resulting nanofiber properties such as diameter and bead formation. The antimicrobial activities of the nanofibers were assayed in vitro by Gram-negative (E. coli) and Gram-positive(S. aureus) bacteria. It was observed that PVA/TX-100/BA showed better antibacterial activity against S.aureus bacteria compared to PVA and PVA/TX-100 nanofibers. 相似文献
154.
155.
The aim of this study was to compare the cyclic fatigue resistance of rotary NiTi files, produced with four different manufacturing methods on specially designed dynamic models that simulated clinical conditions. In this study, 120 files, consisting of 30 files for Typhoon, ProTaper Next, RaCe, and Twisted Files nickel titanium rotary systems were used. The 30 files of each group were divided into three subgroups to be used in artificial canals with a 60° angle of curvature and radii of curvature of 2, 5, and 8 mm (n = 10). All files were rotated in the artificial canals until fracture occurred and the number of cycles to fracture was calculated. The data were analyzed using one‐ and two‐way analyses of variance and Tamhane multiple comparison tests. In all three groups, Typhoon instruments had the highest number of cycles to failure than the RaCe, ProTaper Next, and Twisted Files instruments, and the difference statistically significant (p < .05). There were no significant differences between the RaCe, ProTaper Next, and Twisted Files groups (p > .05). The CM wire Typhoon system was significantly more resistant to cyclic fatigue compared to the other file systems in all three artificial canals. When the fracture resistance of an instrument in three different artificial canals was compared, the mean NCFs decreased as the radius of the curvature of the canal decreased from 8 to 2 mm. Manufacturing method is one of the most important factors on cyclic fatigue resistance, also the radius of curvature effects the cyclic fatigue. 相似文献
156.
Gulsun Akdemir Evrendilek Eda Keskin Ozgur Golge 《Journal of the science of food and agriculture》2020,100(4):1653-1661
157.
Ozkan Kaya;Fadime Ates;Selda Daler;Nurhan Keskin;Metin Turan; 《Food and Energy Security》2024,13(4):e562
In the context of global efforts to improve food quality against the backdrop of climate change and increasing demands for food, this study sought to investigate the influence of tillage and fertilization methods on essential nutritional components. Thus, this extensive investigation into the variability of organic acid, sugar, and vitamin content within berries over the years 2020 to 2022 shows the critical influence of agricultural practices on the nutritional quality of grape. Our findings revealed significant fluctuations in the levels of various organic acids, with oxalic and propionic acids seeing a notable increase in 2022, while tartaric, citric, and maleic acids decreased. Similarly, a significant rise in sucrose, glucose, and fructose levels was documented by 2022, alongside a variable trend in vitamin content. The PCA results revealed a clear impact of tillage and organic amendments on the biochemical composition of Royal grapes. Heatmap findings confirmed the results obtained from PCA and showed that certain treatments resulted in high organic acid content, while others resulted in high sugar content. However, disc harrow and olive blackwater 2021 followed by disc harrow and Antep radish 2021 and no-tillage broccoli 2020 were the best treatments with a balanced distribution of organic acids, soluble sugars, and vitamins among all treatments. On the other hand, chisel and olive blackwater '20 was the treatment with the lowest ratio of organic acids, sugars, and vitamins, followed by chisel and Antep radish 2020. These results show that the concentration of organic acids, soluble sugars, and vitamins in grapes is more affected by the tillage method than the type of organic fertilizer used. To sum up, our study holds valuable implications for viticulture and agriculture at large, highlighting the potential to tailor farming practices for enhanced nutritional outcomes. Such advancements not only promise to elevate the quality of agricultural produce but also contribute to the broader objective of achieving food security and nutritional adequacy, thus offering a roadmap for future research and practice in sustainable agriculture and viticulture. 相似文献