Mucosal loss as a critical factor in esophageal stricture formation after mucosal resection: a pilot experiment in a porcine model.

BACKGROUND AND AIM: Esophageal stricture is a major complication of large areas endoscopic submucosal dissection (ESD). Until now, the critical mechanism of esophageal stricture remains unclear. We examined the role of mucosal loss versus submucosal damage in esophageal stricture formation after mucosal resection using a porcine model. MATERIALS AND METHODS: Twelve swine were randomly divided into two groups, each of 6. In each group, two 5-cm-long submucosal tunnels were made to involve 1/3rd of the widths of the anterior and posterior esophageal circumference. The entire mucosal roofs of both tunnels were resected in group A. In group B, the tunnel roof mucosa was incised longitudinally along the length of the tunnel, but without excision of any mucosa. Stricture formation was evaluated by endoscopy after 1, 2, and 4 weeks, respectively. Anatomical and histological examinations were performed after euthanasia. RESULTS: Healing observed on endoscopy in both groups after 1 week. Group A (mucosa resected) developed mild-to-severe esophageal stricture, dysphagia, and weight loss. In contrast, no esophageal stricture was evident in group B (mucosa incisions without resection) after 2 and 4 weeks, respectively. Macroscopic examination showed severe esophageal stricture and shortening of esophagus in only group A. Inflammation and fibrous hyperplasia of the submucosal layer was observed on histological examination in both groups. CONCLUSION: The extent of loss of esophageal mucosa appears to be a critical factor for esophageal stricture. Inflammation followed by fibrosis may contribute to alteration in compliance of the esophagus but is not the main mechanism of postresection stricture.

Study on Ignition Delay and Reaction Mechanism of RP-3/Air Combustion Adding C6F12O.

RP-3 jet fuel is the main fuel for aircraft in China, and it is also a source of fire. C6F12O (Novec 1230) has an outstanding fire extinguishing performance and minimal environmental impacts. In this study, the application of C6F12O in the inhibition of RP-3 jet fuel fire was considered, and the ignition delay time (IDT) of C6F12O/air and RP-3/air adding C6F12O was measured using a shock tube. In addition, the results showed that the IDT of C6F12O was 500-900 µs and less sensitive to temperature compared with those of common fuels in the range of 1150-1958 K, and the influence of C6F12O on the IDT of RP-3 jet fuel was influenced by many factors including temperature, the concentration of C6F12O, and the stoichiometric ratio of RP-3 jet fuel. According to the experimental results, the mechanism of C6F12O was verified and modified, and then integrated with the mechanisms of RP-3 jet fuel; the integrated mechanism can well predict the IDT of C6F12O/air and RP-3/air adding C6F12O. This work provides a good basis for the chemical kinetics analysis of the inhibition of RP-3 jet fuel combustion by C6F12O.

Development of a Chemical-Kinetic Mechanism of a Four-Component Surrogate Fuel for RP-3 Kerosene.

RP-3 kerosene is the most widely used aviation kerosene in China, and research on its chemical-kinetic mechanism is significant for understanding the combustion characteristics. Based on a novel four-component surrogate fuel consisting of n-dodecane, 2,5-dimethylhexane, 1,3,5-trimethylbenzene, and decalin (54, 22, 14, and 10% by mole), the detailed chemical-kinetic mechanism of the corresponding RP-3 surrogate fuel with 1333 species and 6803 reactions has been developed and then reduced to 145 species and 818 reactions for high-temperature conditions. After that, the merged surrogate mechanism of surrogate fuel was validated by various experimental data sets for each individual surrogate component. Then, the surrogate mechanism was validated by comparing the simulation and experimental data of the ignition delay times, species concentrations in a jet-stirred reactor, and laminar flame speeds. Good agreements between simulations and experiments were observed. In addition, using the sensitivity analysis method, the key reactions of RP-3 surrogate fuels were compared and analyzed. In summary, the mechanism developed in this study can accurately predict the ignition, oxidation, and flame propagation characteristics of RP-3 aviation kerosene. The novel surrogate model can help deeply understand the combustion characteristics of RP-3 aviation kerosene, and it is used for high-precision numerical simulation of combustion reaction flow.

[Flow injection biosensor based on the immobilized AChE].

A biosensor based on the flow injection system was constructed with the immobilized AChE from Scomberomorus niphonius (Curier) as identification element and a pH electrode as transducer. When phosphate buffer was used as carrier liquid, a good reproducibility (RSD = 1.427% , n=10) of the biosensor response was obtained after the substrate was injected repetitively. After an incubation time of 20 min, the calibration graph to methyl-parathion is linear (r = 0.9986) when its concentration ranges from 4.29 x 10(-10) mol x L(-1) to 4.29 x 10(-8) mol x L(-1) , and the detection limit is 1.3 x 10(-10) mol x L(-1). However, the sensitivity of this biosensor to methyl-parathion when using clean seawater as carrier liquid is not as good as that using phosphate buffer. But after preoxidation of methyl-parathion with NaClO as oxidant, the detection limit of the biosensor to methyl-parathion in seawater can be improve to 2.16 x 10(-7) mol x L(-1).