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Tunnel fire is a major research topic in tunnel safety. Because of the tunnel's narrow and enclosed structure, smoke movement plays an important role in the investigation of the tunnel fire. In this paper, the Froude similarity principle is used to study the variation rule of the smoke back-layering length of tunnel ceiling jet induced by strong fire plume with different heat release rates, longitudinal ventilation velocities, and effective heights of fire source analyzed. It is found that the smoke back-layering length of tunnel ceiling jet induced by strong fire plume increases with the increase of effective height of fire source and decreases with the increase of longitudinal ventilation velocity. When the heat release rate is relatively small (Q < 60kW), the smoke back-layering length of the tunnel ceiling jet induced by strong fire plume increases as the heat release rate increases. However, for the larger heat release rate (Q ≥ 60kW), the smoke back-layering length of the tunnel ceiling jet induced by strong fire plume is mainly related to the longitudinal ventilation velocity. Based on Thomas's model and Li's model, by introducing the correction coefficient, correction formulas of the smoke back-layering length of tunnel ceiling jet induced by strong fire plume changing with the effective height of fire source are proposed.

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Background Recently, a systematic review and meta-analysis demonstrated that overexpression of p53 immunoprotein was significantly associated with progression risk of oral potentially malignant disorders (OPMD). However, the results of investigations on TP53 genetic typing in OPMD were inconsistent and inconclusive. Methods A systematic evaluation was conducted to identify all eligible case-control studies on the associations between TP53 codon 72 polymorphism and both onset and progression of OPMD. Results A total of 768 OPMD patients and 1173 healthy individuals were identified from 12 eligible case-control studies on TP53 codon 72 polymorphism OPMD onset. In overall and subgroup analyses, no significantly risk of OPMD onset was observed in the cases for genetic models including allele C vs. G, homozygote CC vs. GG, heterozygote GC vs. GG, dominant GC + CC vs. GG, and recessive CC vs. GG + GC (all P-value of association test > 0.05). Further, a total of 465 OPMD patients and 775 oral squamous cell carcinoma (OSCC) ones were identified from 8 eligible case-control studies on this polymorphism in OPMD progression to OSCC. The analyses revealed that there was also no significantly risk of OPMD progression in the cases for the genetic models (all P-value of association test > 0.05). Conclusion Our data of a pooled-analysis indicates that TP53 codon 72 polymorphism may not act as genetic factor for the risk of OPMD onset and progression. Combined with the conclusion by a systematic review and meta-analysis, we put forward a new opinion that TP53 genetic typing cloud not influence p53 protein expression in OPMD.

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