The dissolution of cellulose in tetrabutylammonium acetate (TBAA) and dimethyl sulfoxide (DMSO) mixed solvent was studied at room temperature (approximately 25 °C). The ratio of TBAA in the mixed solvent system (W TBAA) was found to have great influence on the solubility of cellulose and the corresponding dissolution time. The mixed solvent of W TBAA = 0.15 possessed the highest cellulose solubility and shortest dissolution time. Various cellulosic materials were well-dissolved in the solvent with a maximum solubility up to 8.17 wt %. A mechanistic study regarding the interaction between the solvent system and the model compound cellobiose was conducted using 1H NMR, 13C NMR, ATR-FTIR, conductivity, and viscosity measurements. The results implied that TBAA existed at two different states in the mixed solvent as the ratio of TBAA varied (i.e., ion-split stage (W TBAA ≤ 0.15) and ion-paired stage (W TBAA ≥ 0.15)). W TBAA = 0.15 was the turning point of these two stages, and the mixed solvent displayed the best dissolving ability at this ratio. This finding suggests that a balance between the ion concentration and ion mobility is crucial to the dissolving ability of a mixed solvent. The solvation effect of the cosolvent DMSO helped to dissociate TBAA into free ions and facilitate the ion mobility. The hydroxyl protons of cellobiose were demonstrated to form strong hydrogen bonds with CH3COO–, which was key to the dissolution of cellulose. Finally, the interaction between cellobiose and DMSO in the TBAA/DMSO/cellobiose system was investigated and was demonstrated to be another important factor for the dissolution of cellulose by stabilizing the dissolved cellulose chain from further formation of inter- and intramolecular hydrogen bonds.

Epoxidation of three fatty acid methyl esters (FAMEs) were carried out with peroxyacid catalysts to investigate the influences of the alkenyl structure on the epoxidation efficiency and selectivity.

Homogeneous modification of cellulose with succinic anhydride was performed using tetrabutylammonium acetate (TBAA)/dimethyl sulfoxide (DMSO) mixed solvent. The molar ratio of succinic anhydride (SA) to free hydroxyl groups in the anhydroglucose units (AGU), TBAA dosage, reaction temperature, and reaction time were investigated. The highest degree of substitution (DS) value of 1.191 was obtained in a 10 wt% TBAA/DMSO mixed solvent at 60 °C for 60 min, and the molar ratio of SA/AGU was 6/1. The molar ratio of SA/AGU and the TBAA dosage showed a significant influence on the reaction. The succinoylated cellulose was characterized by ATR-FTIR, TGA, XRD, solid state CP/MAS 13C NMR spectroscopy (CP/MAS 13C NMR), and SEM. Moreover, the modified cellulose was applied for the adsorption of Cu2+ and Cd2+, and both the DS values of modified cellulose and pH of the heavy metal ion solutions affected the adsorption capacity of succinylated cellulose. The highest capacity for Cu2+ and Cd2+ adsorption was 42.05 mg/g and 49.0 mg/g, respectively.

In this paper, we study an integrable coherently-coupled nonlinear Schrödinger system arising from low birefringent fibers and weakly anisotropic media. We construct the Nth iterated Darboux transformation (DT) in the explicit form and give a complete proof for the gauge equivalence of the associated Lax pair. By the DT-based algorithm, we derive the N-soliton solutions which can be uniformly represented in terms of the four-component Wronskians. We analyze the properties of coherently coupled solitons, revealing the parametric criterion for the non-degenerate solitons to respectively display the one-and double-hump profiles. In addition, we point out that the doublehump solitons may have potential application in realizing the multi-level optical communication.

AIM:To evaluate the application o� magnetic resonance imaging (MRI) to the preoperative staging o� advanced gastric cancer. METHODS:An MRI (SE sequence) was preoperatively per�ormed on 34 patients with advanced gastric cancer. The tumors were located at the cardia �undus in 11 patients, the corpus in 14, the antrum in ten and throughout the entire stomach in two. The images were analyzed and staged on the basis o� the criteria proposed by Matsushita M. The results were compared with the corresponding histopathologic findings to analyze the rate of diagnostic accordance. RESULTS:The diagnostic rate accuracy by MRI was 77.8% (seven out o� nince) �or T2 tumors; 77.3% (17 out o� 22) �or T3 tumors and 100% (three out o� three) �or T4 tumors, with the overall accuracy equaling 79.4%. When grades T3 and T4 tumors were considered as a single group to determine the presence or absence o� extraserosal invasion using MRI technology, the diagnostic accuracy was 88.3%. Statistically, MRI staging showed a signi�icant correlation with the corresponding histopathologic staging using the Spearman correlation test (r s′ = 0.743, P < 0.01). When the concordance between MRI and histopathologic staging results were studied according to tumor location, the staging accuracy was highest (90.9%) in tumors located in gastric cardia �undus.CONCLUSION: MR imaging is moderately valuable when staging advanced gastric cancer, especially �or tumors located in gastric cardia �undus.