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Keshan Disease (KD) is still a serious endemic public health problem in Northeast China. Previous studies have mainly focused on soil selenium content, staple food selenium content, and human selenium level, but there are few systematic studies on soil selenium existing forms and their migration from soil to crops and human body. In order to provide visualization of the spatial distribution characteristics and migration status of soil selenium content, and to provide a reference basis for the etiological analysis, prevention, control and elimination of KD, the 121183 topsoil soil (0-20 cm) geochemical data and 30295 soil parent material data which were collected and analysed by two-layer gridding method were used to infer the barrier factors in the migration and transformation of selenium from soil to crop and human body. The total selenium average of soil, staple food and human body be counted, the soil selenium existing forms and the correlation analysis between soil aluminum trioxide, iron trioxide were analysed.The average content of topsoil selenium in Northeast China was 0.20 mg/kg, which was significantly lower than the world soil selenium content average (0.4 mg/kg) and slightly lower than the Chinese soil selenium content average (0.239 mg/kg).The average selenium content of human hair is only 0.16mg/kg in Baiquan, Heilongjiang Province. Soil-forming parent material has some influence on soil selenium content, however, epigenetic enrichment is a more significant enrichment factor on soil selenium content. Soil selenium existing in humic acid state selenium, strongly organic bound state selenium, and the contents of selenite, selenate and methyl selenocysteine which are easily used by plants are all relatively high, correlation analysis between soil selenium content and organic matter, iron and aluminium oxides shows that soil organic matter and iron and aluminium oxides were the main barrier factors for selenium migration and transformation. Lower soil selenium content may be the basic factor for the biogeochemical deficiency of selenium, the sequestration of selenium by clay chemical constituents such as iron and aluminium oxides and soil organic matter is the direct factor for the biogeochemical low selenium in the Northeastern China, which increasing the risk of KD in the population. These research findings can provide more evidence to assess the elimination of biogeochemical aetiology of diseases from a selenium nutrient perspective.

Simulation wells with known parameters are vital in the study of anisotropic methods and logging equipment development. We propose a symmetrically partitioned isotropic (SPI) model, which can quantitatively control the parameters of equivalent circumferential anisotropy. First, the circumferential anisotropy of the flexural wave dispersion in the SPI model is analysed using a perturbation method, and the azimuth characteristics of the flexural wave and the wave velocity in the model are evaluated using a numerical simulation algorithm. Next, the circumferential anisotropy characteristics of the model are verified. Finally, the linear relationship between the fast and slow shear-wave velocities of the model and the model parameters is obtained through multiple linear regression analyses, and then, the equivalent circumferential anisotropy is predicted. The feasibility of the quantitative equivalent simulation of circumferential anisotropy media using the SPI model is verified.

A method for carrier-free immobilization of multi-enzyme complexes with more than four enzymes was developed by utilization of polypeptide interactions (SpyCatcher/SpyTag and dockerin/cohesin) and enzyme component self-oligomerization. Two pairs of scaffoldins with different arrangements of SpyCatcher/SpyTag and cohesins were prepared to recruit the four dockerin-containing cascade enzymes (i.e., alpha-glucan phosphorylase, phosphoglucomutase, inositol 1-phosphate synthase, and inositol 1-phosphatase) that can convert starch to inositol, forming multi-enzyme complexes. These self-assembled enzyme complexes showed higher initial reaction rates than the four-enzyme cocktail. Also, water insoluble self-assembled multi-enzyme complexes were observed, being the carrier-free immobilized multi-enzyme complex aggregates. These immobilized enzyme complexes can be recycled easily by simple centrifuging followed by resuspension for another round of reaction. Not only can these immobilized enzyme complexes be obtained by mixing the purified enzyme components, but also by the mixing of crude cell extracts. Therefore, the strategy for the carrier-free immobilization of enzyme complex shed light on improving the catalytic capability of in vitro synthetic enzymatic biosystem.

Phosphatases catalyze the irreversible dephosphorylation of phosphate-containing compounds, and hence can be applied as the final enzymatic step for the synthesis of various biochemicals. However, the extensive substrate spectrums of phosphatases impose a great challenge for efficient biomanufacturing. Characterization of phosphatases is therefore of extreme importance. In this study, MmPase, a putative HAD phosphatase from Methanothermobacter marburgensis, was expressed, purified, and characterized. Recombinant MmPase was readily expressed in Escherichia coli, and required metal ions such as Mn