Probabilistic Durability Assessment of Concrete Structures in Marine Environments:Reliability and Sensitivity Analysis

A probabilistic framework for durability assessment of concrete structures in marine environments was proposed in terms of reliability and sensitivity analysis, which takes into account the uncertainties under the environmental,material, structural and executional conditions. A time-dependent probabilistic model of chloride ingress was established first to consider the variations in various governing parameters, such as the chloride concentration,chloride diffusion coefficient, and age factor. Then the Nataf transformation was adopted to transform the nonnormal random variables from the original physical space into the independent standard Normal space. After that the durability limit state function and its gradient vector with respect to the original physical parameters were derived analytically, based on which the first-order reliability method was adopted to analyze the time-dependent reliability and parametric sensitivity of concrete structures in marine environments. The accuracy of the proposed method was verified by comparing with the second-order reliability method and the Monte Carlo simulation. Finally, the influences of environmental conditions, material properties, structural parameters and execution conditions on the time-dependent reliability of concrete structures in marine environments were also investigated. The proposed probabilistic framework can be implemented in the decision-making algorithm for the maintenance and repair of deteriorating concrete structures in marine environments.

Comprehensive Assessment of Eco-environment Vulnerability in Hebei Province Based on ArcGIS

[Objective] This study aimed to assess the vulnerability of ecological environment in Hebei Province.[Method] Based on ArcGIS,by using the dominant factor and maximum limits factor method,we established the sensitivity-reality indicator system and assessment model of the eco-environment vulnerability in Hebei Province to quantitatively evaluate its eco-environment vulnerability,and analyzed its spatial distribution.[Result] The status quo of environmental degradation was inconsistent with the sensitivity of eco-environment in Hebei Province.The area of severely vulnerable region accounted for only 4.1% of total area in Hebei Province,mainly distributed in nine counties or districts of Baxia region,Zhangjiakou,northwestern Hebei,which was covered with mountains and basins,showing bands,which resulted from the vulnerability of soil erosion and land desertification.In addition,the moderately vulnerable region made up 38.4%,having the largest proportion,and mainly distributed in the mountain and basin region in northwestern Hebei,Yanshan Mountain and the most regions of Taihang Mountain,due to the vulnerability of soil erosion.At the same time,there were also large patches of moderately vulnerable region in Bashang and Baxia of Zhangjiakou,owning to the vulnerability of land desertification.Besides,most plains were mildly vulnerable and slightly vulnerable regions,and their areas accounted for 25.1% and 32.4% respectively of total area.[Conclusion] The research could provide scientific references for safeguarding the ecological security and main functional district planing of Hebei Province.

In vivo precision imaging of vicinal-dithiol-containing proteins by a FRET molecular probe sensitive to protein environment

We here present a Förster resonance energy transfer(FRET)-based and environment-sensitive fluorescent probe VG-1 for vicinal-dithiol-containing proteins(VDPS).VG-1 uniquely contalns two sites sensitive to the protein environment(SPE)thus it shows weak fluorescence in both blue and green channels(a low FRET efficiency)in solution.After specifically binding with VDPs,its fuorescence in the green channel increases,while that in the blue channel disappears,achieving the specific detection of VDPs.The obvioussignal changes in fluorescence may be attributed to that the increased rigidity of the molecular skeletons causes the enhanced FRET eficiency,The probe also achleved the cell super-resolution imaging of VDPs and the confocal imaging of VDPs in zebrafish.

Preliminary study on radiocarbon AMS dating of pollen

17 samples were collected from aeolian and lacustrine profiles within the environment sensitive zone of the Loess Plateau, and an experimental method was established which is suitable for pollen extraction from aeolian sediment. A comparative study of pollen dating was carried out using the accelerator mass spectrometry (AMS)14C dating of known age samples, and then an experiment with the pollen concentrates was performed. The results indicate that pollen that has been deposited simultaneously with sediment in a stable environment can provide reliable ages. This technique will provide a way of improving the chronological framework for the Loess Plateau since the late Pleistocene. TheI4c dating was combined with field investigations, and from the geological record within this zone, evidence was extracted of four major monsoon precipitation changes during the transition from the late Pleistocene to Holocene.