3D anisotropy in shear failure of a typical shale

It is inadequate to study the shear failure anisotropy of shale in only 2D space.Aiming at a 3D analysis,a series of direct shear tests was conducted on Longmaxi shale with three typical bedding orientations:arrester,divider and short-transverse orientations.During testing,acoustic emission(AE)and digital image correlation(DIC)techniques were simultaneously employed to monitor failure development,after testing,X-ray computed tomography(CT)scanning was adopted to acquire and reconstruct the fractures inside typical ruptured samples for more detailed analysis.The results indicated that the shear strength parameters exhibited 3D anisotropies and those of the arrester sample did not have equivalent shear strength parameters to the shale matrix.The maximum(minimum)shear strength and cohesion were obtained with the divider(short-transverse)orientation,and the internal friction angle reached its maximum(minimum)with the divider(arrester)orientation.Combining the AE,DIC and CT techniques,four characteristic stress levels that can capture the progressive shear failure process of shale rocks were identified,and the onset and accelerated development of shear damage-induced dilation were observed at the crack initiation and coalesce stress thresholds,respectively.During the crack coalescence stage,the dominated microcracking mechanism transferred from tensile-mode to shear-mode.For the arrester and divider orientations,more tensile-mode AE events were generated due to the microcracking along the vertical beddings.Compared with the divider samples,a more complex fracture network with a larger fracture area and volume was obtained in the arrester samples,whose strengths were smaller.

Analysis of var genes cloned from a Plasmodium falcivarum isolate in China

Objective:To analyse the rar gene repertoire and characterise the rhondroitin sulphate A (CSA)-binding activity of the Duffy-binding like(I)BI.) domains encoded by the var2csa gene of a Plasmodium falciparum(P.falciparum) isolate in Hainan Province,China.Methods:The sequences of var DBL1 regions were PCR-amplified,sequenced and the sequence characteristics was bioinformalically analysed.Recombinant proteins encoded by the var2csa genes were expressed and purified.The binding activities of the recombinant proteins to CSA receptor was detected by ELISA assays.Results:Fifty six unique DBI.a sequences were obtained,and the sequences represented similar diversity to the var genes of the genome parasite 3D7.There are two var2csa genes in the P.falciparum isolated from Hainan Province.Unlike in other falciparum parasites such as HB3,the two var2csa genes are more diverged.The receptor-binding capacity of DBL-5εand DBI.-6 e domains of HN var2CSA was studied.Conclusions:This work represented the diversity of rar genes of a P.falciparum isolate in China.

Codon usage and evolutionary dynamics of genetic diversity of novel imported porcine reproductive and respiratory syndrome virus in China

Porcine reproductive and respiratory syndrome(PRRS)is a problem that has significant economic impact on the global pig industry.In recent years,there has been an increased importation of pork into China,contributing to the emergence of novely imported porcine reproductive and respiratory syndrome virus(PRRSV)sub-types.Nevertheless,codon usage patterns and their effects on the evolution and adaptation of these new input PRRSV sub-types in hosts remain elusive.To investigate this,we employed a Bayesian approach to analyze two novel imported PRRSV sub-types,namely,NADC30-like and NADC34-like viruses.These sub-types have different codon preferences.Besides,the Effective Number of Codon(ENC)analysis revealed that both NADC30-like and NADC34-like fall within the expected curve distribution,describing a balanced codon usage for both NADC30-like and NADC34-like virus.Based on the Codon Adaptation Index(CAI),NADC30-like showed the highest similarity to the host,aligning with the main prevalence trend of the host.In contrast,NADC34-like exhibited the highest frequency of optimal codon usage;this analysis is based on Frequency of Optimal Codons(FOP).Moreover,the Relative Codon Deoptimization Index(RCDI)indicates that NADC30-like sub-types have a greater degree of inverse optimization sub-type.These findings suggest that mutational pressure affects codon usage preferences of genes in newly imported PRRSV,and that natural selection plays a vital role in determining PRRSV gene codon preferences.Our study provides new insights into the disease,origin,evolutionary patterns,and host adaptation of these newly imported PRRSV sub-types in China.It also contributes to the development of theoretical frameworks for studying genetics and the evolution of PRRSV.