Effect of moisture on microwave ignition of bituminous coal.

The interaction between water and microwave is of vital importance to reveal the microwave ignition mechanism of water-bearing coal. This study used two group of bituminous coal after drying and water saturation treatment, for experimental testing and contrastive analysis. During the experiment, permeability of coal samples was obtained based on nuclear magnetic resonance(NMR) test, then different power of microwaves were applied to coal samples, and the occurrence of hot spots within coal samples was regarded as a sign of microwave ignition. Microwave ignition of water-saturated coal is mainly affected by microwave power and coal permeability. The pore water in low permeability coal is conducive to microwave ignition, while the pore water in high permeability coal will prolong the ignition time. There is a permeability threshold, above which the average ignition time of water-saturated coal samples is longer than that of dry coal samples, but below which the opposite is true. These insights can be used to evaluate the safety of microwave technology when applied to coal engineering.

External validation of alternative fistula risk score (a-FRS) for predicting pancreatic fistula after pancreatoduodenectomy.

BACKGROUND: The utility of the proposed alternative fistula risk score (a-FRS) for predicting risk of clinically relevant postoperative pancreatic fistula (CR-POPF) after pancreaticoduodenectomy (PD) has not been validated widely. METHODS: This retrospective analysis included data of patients undergoing open and laparoscopic PD during March 2012-May 2018 in our institution. The predictive abilities of a-FRS and original-FRS were compared. Risk factors for CR-POPF were also evaluated by multivariate regression analysis. RESULTS: Of the 370 patients, 80 (21.62%) developed CR-POPF. The incidences of CR-POPF in patients classified as low risk, intermediate risk, and high risk by a-FRS were 5.88%, 24.38%, and 57.69%, respectively (R2 = 0.97). The incidences of CR-POPF in patients classified as negligible risk, low risk, intermediate risk, and high-risk by original-FRS were 0%, 8.62%, 21.51%, and 52.50%, respectively (R2 = 0.92). The area under the ROC curve (AUC) was 0.74 for a-FRS vs. 0.70 for original-FRS. The a-FRS performed better than original-FRS for prediction of CR-POPF in open PD patients (AUC: 0.74 vs. 0.69) and was comparable with original- FRS in laparoscopic PD patients (AUC: 0.70 vs. 0.72). CONCLUSIONS: The a-FRS appears to be an accurate and convenient tool for predicting occurrence of CR-POPF after PD.