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6. Quantitative Formation of Octa‐substituted Cyclobutanes by the [2+2] Photocycloaddition of Stiff‐stilbenes.

Author

Sun, Xiao‐Wen, Li, Yu, Lu, Mengxue, Zhao, Wei, Ma, Hongwei, Yang, Xiao‐Juan, and Wu, Biao

Subjects
*STERIC hindrance, *PHARMACEUTICAL chemistry, *MATERIALS science, *HYDROGEN bonding, *PHOTOCYCLOADDITION
Abstract

The creation of new molecules with specific structural motifs is a primary goal in synthetic chemistry. In this context, cyclobutanes (CBs), the highly strained ring systems, are of great interest because of their wide applications from pharmaceutical chemistry to materials science. The [2+2] photocycloaddition is the most straightforward approach for CBs; however, access to fully substituted cyclobutanes presents a significant challenge due to the steric hindrance imposed by eight substituents. Here, we report an efficient synthesis of structurally unique, octa‐substituted cyclobutanes from stiff‐stilbene precursors, which is enabled by adaptable anion coordination through hydrogen bonding networks. The synthesized spiro‐benzocyclopentyl‐substituted cyclobutanes are confirmed by single‐crystal structures. DFT calculations indicate that these cyclobutanes have high ring‐strain energies (~20.1 kcal/mol) and can be completely converted back to stiff‐stilbenes. Such a reversible cycloaddition/reversion process offers a promising platform for applications in responsive and energy storage materials. [ABSTRACT FROM AUTHOR]

Published
2024
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18. Nonstented versus routine stented ureteroscopic holmium laser lithotripsy: a prospective randomized trial

Author

Shao, Yi, Zhuo, Jian, Sun, Xiao-Wen, Wen, Wei, Liu, Hai-Tao, and Xia, Shu-Jie

Abstract

Abstract: We conducted a prospective, randomized study to evaluate whether postoperative ureteral stenting is necessary after ureteroscopic holmium laser lithotripsy. A total of 115 consecutive patients with distal or middle ureteral calculi amenable to ureteroscopic holmium laser lithotripsy were prospectively randomized into stented group (n = 58) and nonstented group (n = 57). The stent was routinely placed in the treated ureter for 2 weeks. The outcomes were measured with postoperative patient symptoms, stone-free rates, early and late postoperative complications, and cost-effectiveness. The postoperative symptoms were measured with Ureteral Stent Symptom Questionnaire (USSQ). All patients completed a 12-week follow-up. There was no significant difference between two groups with respect to the patient age, stone size, stone location and mean operative time. According to the USSQ, the symptoms of the stented group were significantly worse compared to the nonstented group (P = 0.0001). In the stented group, two patients had high fever for 1 week after the operation, stent migration was found in two patients, and the stents had to be removed earlier in five patients because of severe pain or hematuria. The cost of the stented group was significantly higher than the nonstented group. The stone-free rate was 100% in both groups. No hydronephrosis or ureteral stricture was detected by intravenous pyelogram in the 12th week postoperative follow-up. In conclsion, we believe that routine stenting after ureteroscopic intracorporeal lithotripsy with the holmium laser is not necessary as long as the procedure is uncomplicated for distal or middle ureteral calculis less than 2 cm.

Published
2024
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41. Optimization of the Thickness and Interface Structure of Al 2 O 3 -YAG/ZrO 1.5 -YO 1.5 -TaO 1.5 /8YSZ/NiCoCrAlY Multilayer Thermal Barrier Coatings: A Finite Element Simulation.

Author

Su, Huai-Yu, Zhou, Hong-Xia, Cao, Zhi-Jun, Wan, Jia-Bao, Liu, Yao, Sun, Xiao-Wen, Su, Jia-Hui, Wu, Qian, and Wang, Liang

Subjects
THERMAL barrier coatings, INTERFACE structures, INTERFACIAL bonding, ALUMINUM oxide, COATING processes, INTERFACIAL stresses
Abstract

Highlights: (1)  The thickness and interface structure of the multilayer ceramic layers were optimized using the finite element method, which significantly saved the cost of experiments.(2)  The failure mechanism and thickness selection range of the multilayer coatings were determined, providing theoretical guidance for the coating process.(3)  The effects of different roughness on the magnitude and distribution of interfacial residual stresses were investigated to provide theoretical guidance for the selection of interfacial roughness of thermal sprayed coatings. Thermal barrier coatings (TBCs) prepared using the atmospheric plasma spraying method fail mainly due to coating delamination caused by thermal mismatch in the absence of high temperature assessment. In this study, the thickness optimization of multiple ceramic layers in a TBCs and the influence of the interface structure on the residual stress of the coating were investigated using a finite element simulation method. The results showed that varying the thickness of each layer of a TBCs with multiple ceramic layers affects the distribution and magnitude of the residual stress of the coating. Therefore, a reasonable range of thickness for each layer can be determined. The thickness of the bonding layer should be 110 μm, the thickness of YSZ layer should be about 270 μm, the thickness of tantalate layer should be about 70 μm, and the thickness of Al2O3-YAG layer should be about 100 μm. Simultaneously, the results show that a rough interface can be more effective in reducing the relief of stress concentrations compared to a smooth interface, but the stress values increase. [ABSTRACT FROM AUTHOR]

Published
2022
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