Ethnic Differences in Preterm Birth Risks for Pregnant Women with Thyroid Dysfunction or Autoimmunity:A Meta-analysis

Objective Abnormal maternal thyroid function is associated with preterm birth.However,this association stays dubious in relevant individual studies for ethnic difference reasons and lack of direct supporting data.This study aimed to evaluate the relationship between preterm birth and thyroid dysfunction or autoimmunity based on ethnic differences.Methods Relevant studies were identified through searches of MEDLINE,Excerpta Medica,Wan Fang,China Biological Medicine disc,and China National Knowledge Infrastructure from inception to June 15,2016.Original articles in which an incidence or prevalence of thyroid dysfunction or autoimmunity before second trimester of pregnancy could be extracted were included.Results Thirty-two unique studies were included for the final meta-analysis.Patients involved were divided into two groups：Group 1（G1） and Group 2（G2） comprising of Asian and Caucasian populations,respectively.Positive thyroid antibodies were associated with the occurrence of preterm birth in both G1 [odds ratio（OR）：3.62,95% confidence interval（CI）：2.83-4.65] and G2（OR：1.35,95% CI：1.17-1.56）;hypothyroidism,only in G2（OR：1.20,CI：1.09-1.33）;and subclinical hypothyroidism or hypothyroxinemia,in neither group.Conclusion Thyroid autoimmunity may be a more favorable factor leading to preterm birth among pregnant women of different ethnicities,compared with thyroid dysfunction.

Crack status analysis for concrete dams based on measured entropy

The integrity and safety of concrete darns are seriously affected by the existing cracks in dam bodies, and some serious cracks may cause dam failure or disaster. The propagation of cracks in concrete dams is accompanied by changes in energy distribution, which can be represented by changes in the structure＇s system entropy. Therefore, the entropy theory can be used in analyzing the behavior of dam cracks. Due to the randomness and locality of crack propagation, it is difficult to predict the loca- tion of cracks by traditional monitoring methods. To solve this problem, the influence of spatial positions of monitoring points on inspection zones is represented by a weight index, and the weight index is determined by the distance measure method proposed in this paper. Through the weighted linear fusion method, the entropy of multiple monitoring points is obtained for analyzing the behavior of dam cracks in the selected zones. Meanwhile, the catastrophe theory is used as the variation criterion of an entropy sequence in order to predict the instability time of dam cracks. Case studies are put forward on a high arch darn, and the fusion entropy is calculated according to the monitoring data from strain gauges. Results show that the proposed method can effectively predict the occurrence time and location of dam cracks regardless of the layout of monitoring instruments, and it is a new way to analyze the occurrence and propagation of dam cracks.