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Due to the influences of buildings, geographical and geomorphological environments, road conditions, etc., the probabilities and numbers of casualties in different areas after an earthquake are different. Accordingly, we propose the concept of the lethal level, which attains different grades representing the mortality rate of differing intensities. Different regions have unique lethal levels, and regional lethal levels are affected mainly by the proportion of each building type and the corresponding lethal level, as different types of buildings also have unique lethal levels. Based on data of 52 historical earthquake disasters, we constructed a lethal level calculation model and obtained the lethal level of each building type. The results reveal that the lethal level ranges of different building types are fixed and unequal; moreover, the ranges of different building types overlap each other. The lethal level range of adobe structures is 0.85–1, that of civil structures is 0.75–0.95, that of brick-wood structures is 0.6–0.9, that of brick-concrete structures is 0.33–0.6, that of wood structures is 0.2–0.35, and that of reinforced concrete structures is 0.1–0.25. Based on the lethal levels of these building types, the overall level of a region can be quantified and graded, and this classification does not depend on the geographical location or administrative boundaries. In pre-earthquake evaluation efforts, the lethal level of an area can be derived through field research. After an earthquake, the number of casualties can be quickly assessed based on the mortality rate corresponding to the intensity of the area. This approach can further provide scientific support for risk zoning and risk assessment research.

Earthquake disaster risk analyses provide significant scientific guidance for reducing earthquake disaster losses etc. The current commonly used method is based on the vulnerability of different types of buildings to evaluate, and may ignore the difference between the seismic resistance of the same type of buildings in different areas. The lethal level considers a series of reasons such as different types of buildings, resulting in different capacities for casualties, the lethal levels of the cities in the same subregion are considerably different and exhibit obvious distribution characteristics. In Yancheng and Suqian, the lethal levels in urban areas are lower than those in rural areas, but the lethal levels in Guangzhou show the opposite trend (the lethal levels are higher in urban areas than in other towns and rural areas). The average lethal level in Guangzhou is 0.3856, that in Suqian is 0.5844, and that in Yancheng is 0.5912. This study based on the lethal levels, conduct a comparative analysis of the earthquake disaster risk of cities throughout eastern China, and a map of the earthquake disaster risk in each city is obtained. The overall lethal level and risk in Guangzhou is much lower than those in Yancheng and Suqian. The main influencing factors in the different cities also diverge. One reason for the lower lethal levels and risk in Guangzhou is that most of the brick-concrete structures are equipped with ring beams and structural columns; conversely, Yancheng and Suqian exhibit higher lethal levels and risk because the brick-concrete structures have ring beams but no structural columns. These maps provide a technical reference and solid scientific and technological support for further earthquake disaster risk analyses and for disaster prevention, mitigation and disaster relief planning, and this method improves the accuracy of rapid postearthquake assessment.

The cinnamoyl lipid compound youssoufene A1 (1), featuring a unique dearomatic carbon‐bridged dimeric skeleton, exhibits increased inhibition against multidrug resistant Enterococcus faecalis as compared to monomeric youssoufenes. However, the formation process of this intriguing dearomatization/dimerization remains unknown. In this study, an unusual "gene‐within‐gene" thioesterase (TE) gene ysfF was functionally characterized. The gene was found to naturally encodes two proteins, an entire YsfF with α/β‐hydrolase and 4‐hydroxybenzoyl‐CoA thioesterase (4‐HBT)‐like enzyme domains, and a nested YsfFHBT (4‐HBT‐like enzyme). Using an intracellular tagged carrier‐protein tracking (ITCT) strategy, in vitro reconstitution and in vivo experiments, we found that: i) both domains of YsfF displayed thioesterase activities; ii) YsfF/YsfFHBT could accomplish the 6π‐electrocyclic ring closure for benzene ring formation; and iii) YsfF and cyclase YsfX together were responsible for the ACP‐tethered dearomatization/dimerization process, possibly through an unprecedented Michael‐type addition reaction. Moreover, site‐directed mutagenesis experiments demonstrated that N301, E483 and H566 of YsfF are critical residues for both the 6π‐electrocyclization and dimerization processes. This study enhances our understanding of the multifunctionality of the TE protein family. [ABSTRACT FROM AUTHOR]

Two new dimeric cinnamoyl lipids (CL) featuring with an unusual dearomatic carbon-bridge, named youssoufenes A2 (1) and A3 (2), were isolated from the ΔdtlA mutant strain of marine-derived Streptomyces youssoufiensis OUC6819. Structures of the isolated compounds were elucidated based on extensive MS and NMR spectroscopic analyses, and their absolute configurations were determined by combination of the long-range NOE-based 1H-1H distance measurements and ECD calculations. Compounds 1 and 2 exhibited moderate growth inhibition against multi-drug-resistant Enterococcus faecalis CCARM 5172 with an MIC value of 22.2 μM. [ABSTRACT FROM AUTHOR]