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Background The development of tumor cells inside the lymphatics or blood vessels is known as lymphovascular invasion (LVI). The correlation between LVI, lymph node metastasis (LNM), and the diagnosis of superficial esophageal carcinoma (SEC) remains unclear. Methods We searched Embase, PubMed, Web of Science, and Cochrane Library databases for prospective articles to better understand the relationship between LVI, LNM, and SEC diagnosis. Results We included 23 articles containing data for 4749 patients (range: 54–598) in our meta-analysis. The hazard ratio between LVI and overall survival (OS) was 1.85 with 95% confidence interval (CI) (1.10–3.11, P = 0.02). LNM rate was higher in SEC patients with LVI than SEC patients without LVI (univariate: OR = 4.94, 95% CI: 3.74–6.53, P P Conclusions The results indicate that LVI plays a dominant role in the prognosis of LNM in SEC and in the prognostic prediction for SEC.

Prestressed concrete cylinder pipes (PCCPs) have been applied for various water conveyance projects recently, especially in long distance. PCCPs not only bear internal water pressures, but also external loads. The excess of external loads may cause major accidents. However, the mechanical behavior of PCCPs under external load is different from that of PCCPs under internal pressure. In this study, a three-edge bearing test (TEBT) of a PCCP was performed to study its mechanical properties under external load. Meanwhile, the fiber Bragg grating (FBG) sensing technology and pulse pre-pump Brillouin optical time-domain analysis (PPP-BOTDA) optical fiber sensing technology were successfully employed to monitor the deformation of PCCPs. The test results show that the deformation of five components of the pipe is proportional to the external load. At the springline of the pipe, the outer concrete core and the prestressing wire are in tension, the inner concrete core and the steel cylinder are in compression. The loading status at the crown and invert of the pipe are opposite with those at the springline of the pipe, but the deformation coordination is consistent. Moreover, the test results demonstrate that PPP-BOTDA-based distributed optical fiber sensors can not only accurately monitor the real-time loading response of the PCCP under the external load like FBG point optical fiber sensors, but also obtain the dynamic and continuous strain distribution of the circumferential section of the pipe. This study has identified the relationship of the external load and deformation, the interaction and strain distribution of each component of PCCPs. This study also confirms that the distributed optical fiber sensing technology can provide an effective means for the structural health monitoring in long-term operation of PCCPs.

Prestressed concrete cylinder pipes (PCCPs) are widely used in large-scale water conveyance projects. It is important to study the mechanical properties and loading response of PCCPs to ensure trouble-free operation. There were insufficient test data pertaining to the deformation of the concrete cores (including the inner and the outer concrete core), the prestressing wire, the mortar coating, especially the steel cylinder. In this paper, a full-scale test was performed on a PCCP under internal water pressure through fiber Bragg grating (FBG) sensing technology. The test results showed that the state of PCCPs would reach three limit-states successively. Firstly, the strains of the concrete cores, the prestressing wire, the steel cylinder and the mortar coating increased linearly with the growth of the internal water pressure. The cracks in the concrete cores indicated the beginning of the serviceability limit-state. The corresponding pressure is 1.8 MPa. The growth of the internal water pressure primarily affected the steel cylinder and the prestressing wire during the continuous period. When the steel cylinder yielded at the pressure of 2.25 MPa, the pipe reached its elastic limit-state. At last, the strength of the pipe decreased obviously as the cracks propagated throughout the concrete cores. The pipe would come to the strength limit-state until the prestressing wire yielded. The test results found that the internal water pressure relieved final prestress of the inner concrete core was different from that of the outer concrete core in the embedded-cylinder pipe (ECP). It was also proved that FBG sensing technology could be the continuous monitoring system for the condition assessment of PCCPs. In particular, the test results demonstrated that the appropriate quality of materials and proper operation guaranteed trouble-free operation of PCCPs. The objective of this research is to provide experimental references for the application of PCCPs and push back safety assessment of this type of large-diameter pipes.

Prestressed concrete cylinder pipes (PCCPs) can suffer from prestress loss caused by wire-breakage, leading to a reduction in load-carrying capacity or a rupture accident. Reinforcement of PCCPs with external prestressed steel strands is an effective way to enhance a deteriorating pipe&rsquo, s ability to withstand the design load. One of the principal advantages of this reinforcement is that there is no need to drain the pipeline. A theoretical derivation is performed, and this tentative design method could be used to determine the area of prestressed steel strands and the corresponding center spacing in terms of prestress loss. The prestress losses of strands are refined and the normal stress between the strands and the pipe wall are assumed to be distributed as a trigonometric function instead of uniformly. This derivation configures the prestress of steel strands to meet the requirements of ultimate limit states, serviceability limit states, and quasi-permanent limit states, considering the tensile strength of the concrete core and the mortar coating, respectively. This theory was applied to the reinforcement design of a PCCP with broken wires (with a diameter of 2000 mm), and a prototype test is carried out to verify the effect of the reinforcement. The load-carrying capacity of the deteriorating PCCPs after reinforcement reached that of the original design level. The research presented in this paper could provide technical recommendations for the application of the reinforcement of PCCPs with external prestressed steel strands.