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In order to improve the storage stability and pavement performance of waste crumb rubber modified asphalt, a new additive polyalkyl phenol disulfide was used to activate waste crumb rubber in this work. By preparing the activated waste rubber powder modified asphalt (AMA) and corresponding unactivated ones(UMA) with different dosages, the variation of asphalt pavement performance with the addition of activated waste rubber powder was studied. Meanwhile, the high and low temperature performance and microscopic action mechanism of activated waste rubber powder modified asphalt were researched. The results showed that the surface of the waste mastic powder became fluffy and porous after activation by additives and the swelling and cracking were more adequate, so that it absorbed more light components and distributed more uniformly, which improved the storage stability, low-temperature performance and construction ease of the waste mastic powder modified asphalt, but its high-temperature performance was reduced. The optimal dosage of activated waste rubber powder in modified asphalt is 25%~30%. [ABSTRACT FROM AUTHOR]

Cemented sand and gravel (CSG) is a kind of green building material that has emerged in recent years. The cement content has a great impact on the deformation characteristics of CSG, but the current constitutive models cannot reflect this problem. Based on the previous research results, this paper depicted the volume strain and shear strain of CSG, established a nonlinear constitutive model of CSG, and finally verified the new constitutive model with experimental data. Results showed that the model could well simulate the deformation characteristics of the CSG with cement content of more than 40 kg/m3, and the entire stress–strain relationship was basically consistent with the experimental value, reflecting the adaptability and superiority of the nonlinear constitutive model of CSG. [ABSTRACT FROM AUTHOR]

Carbon fiber, graphite and steel fiber were selected as conductive phase materials to prepare three-phase conductive concrete with good grounding characteristics. The mixing technology,mix proportion and grounding characteristics of three-phase conductive concrete were studied. The results show that the optimum mix proportion of three-phase conductive concrete is carbon fiber of 0.4%, graphite of 2% and steel fiber of 0.8%. The 28d bending strength and the compressive strength of three-phase conductive concrete is 6.1 MPa and 36.5MPa respectively,and the 28d resistivity of three-phase conductive concrete is 1.97 Ω⋅m, which meets the requirements of mechanical properties and conductivity of grounding materials. The rangeability of resistivity between -10 t and 60 t is 0.56Ω⋅m and the resistivity variation with ambient humidity is 0.28 Ω⋅m. The conductive performance is stable. [ABSTRACT FROM AUTHOR]

The production of optimized strains of a specific phenotype requires the construction and testing of a large number of genome modifications and combinations thereof. Most bacterial iterative genome-editing methods include essential steps to eliminate selection markers, or to cure plasmids. Additionally, the presence of escapers leads to time-consuming separate single clone picking and subsequent cultivation steps. Herein, we report a genome-editing method based on a Rock-Paper-Scissors (RPS) strategy. Each of three constructed sgRNA plasmids can cure, or be cured by, the other two plasmids in the system; plasmids from a previous round of editing can be cured while the current round of editing takes place. Due to the enhanced curing efficiency and embedded double check mechanism, separate steps for plasmid curing or confirmation are not necessary, and only two times of cultivation are needed per genome-editing round. This method was successfully demonstrated in Escherichia coli and Klebsiella pneumoniae with both gene deletions and replacements. To the best of our knowledge, this is the fastest and most robust iterative genome-editing method, with the least times of cultivation decreasing the possibilities of spontaneous genome mutations., (© The Author(s) 2020. Published by Oxford University Press on behalf of Nucleic Acids Research.)

To evaluate the ability of microbial mix-culture fermenting syngas into ethanol, we studied the microbial mix-cultures A-fm 4, G-fm 4, Lp-fm 4 and B-fm 4 obtained by enrichment and compared with Clostridium autoethanogenum DSM10061 with 10% and 25% inoculation size. The results show that, with 10% inoculation size, the ethanol production of A-fm 4, G-fm 4, Lp-fm 4, B-fm 4 and C. autoethanogenum were 349.15, 232.16, 104.25, 79.90 and 26.99 mg/L respectively. With 25% inoculation size, the ethanol production were 485.81, 472.73, 348.58, 272.52 and 242.15 mg/L respectively. Higher inoculation size will increase the production of ethanol. The tested mix-culture exhibited a significant yield advantage compared with the maximum production of C. autoethanogenum reported in the literature (259.64 mg/L). This research provided a practical method to improve ethanol production from syngas.