Deformation nanomechanics and dislocation quantification at the atomic scale in nanocrystalline magnesium

Classical molecular dynamics(MD)simulation method is employed to study the uniaxial tensile deformation of nanocrystalline magnesium(Mg)of varying grain size levels.The mean grain size of the sample is varied from 6.4 nm to 45 nm,with each sample containing about 43 million atoms in the modeling system.The deformation nanomechanics reveals two distinct deformation mechanisms.For larger grain-sized samples,dislocation dominated deformation is observed while,in smaller grain-sized samples,grain boundary-based mechanisms such as grain boundary sliding,grain boundary rotation are observed.The transition of normal and inverse Hall-Petch relation occurs at around lOnm.Dislocation density quantification shows that the dislocation density in the sample drastically reduces with decreasing grain size.Elastic modulus of nanocrystalline Mg with mean grain size above 20 nm remains comparable to that of the coarse-grained polycrystalline bulk,followed by a rapid reduction below that grain size.The present work reveals the nanomechanics of nanocrystalline Mg,facilitating the design and development of Mg-based nanostructured alloys with superior mechanical properties.

C9N4 as excellent dual electrocatalyst:A first principles study

We perform first principles calculations to investigate the catalytic behavior of C_(9)N_(4)nanosheet for water splitting.For the pristine C_(9)N_(4),we find that,at different hydrogen coverages,two H atoms adsorbed on the 12-membered ring and one H atom adsorbed on the 9-membered ring show excellent performance of hydrogen evolution reaction(HER).Tensile strain could improve the catalytic ability of C_(9)N_(4)and strain can be practically introduced by building C_(9)N_(4)/BiN,and C_(9)N_(4)/GaAs heterojunctions.We demonstrate that the HER performance of heterojunctions is indeed improved compared with that of C_(9)N_(4)nanosheet.Anchoring transition metal atoms on C_(9)N_(4)is another strategy to apply strain.It shows that Rh@C_(9)N_(4)exhibits superior HER property with very low Gibbs free energy change of-30 meV.Under tensile strain within~2%,Rh@C_(9)N_(4)could catalyze HER readily.Moreover,the catalyst Rh@C_(9)N_(4)works well for oxygen evolution reaction(OER)with an overpotential of 0.58 V.Our results suggest that Rh@C_(9)N_(4)is favorable for both HER and OER because of its metallic conductivity,close-zero Gibbs free energy change,and low oneset overpotential.The outstanding performance of C_(9)N_(4)nanosheet could be attributed to the tunable porous structure and electronic structure compatibility.

Toxicity effects of disinfection byproduct chloroacetic acid to Microcystis aeruginosa: Cytotoxicity and mechanisms

Chlorine-based disinfectants are widely used for disinfection in wastewater treatment.The mechanism of the effects of chlorinated disinfection by-products on cyanobacteria was unclear.Herein,the physiological effects of chloroacetic acid(CAA)on Microcystis aeruginosa(M.aeruginosa),including acute toxicity,oxidative stress,apoptosis,production of microcystin-LR(MC-LR),and the microcystin transportation-related gene mcyH transcript abundance have been investigated.CAA exposure resulted in a significant change in the cell ultrastructure,including thylakoid damage,disappearance of nucleoid,production of gas vacuoles,increase in starch granule,accumulation of lipid droplets,and disruption of cytoplasm membranes.Meanwhile,the apoptosis rate of M.aeruginosa increased with CAA concentration.The production of MC-LR was affected by CAA,and the transcript abundance of mcyH decreased.Our results suggested that CAA poses acute toxicity to M.aeruginosa,and it could cause oxidative damage,stimulate MC-LR production,and damage cell ultrastructure.This study may provide information about the minimum concentration of CAA in the water environment,which is safe for aquatic organisms,especially during the global coronavirus disease 2019 pandemic period.

An imputed whole-genome sequence-based GWAS approach pinpoints causal mutations for complex traits in a specific swine population

Sequencing-based genome-wide association studies(GWAS) have facilitated the identification of causal associations between genetic variants and traits in diverse species. However, it is cost-prohibitive for the majority of research groups to sequence a large number of samples. Here, we carried out genotype imputation to increase the density of single nucleotide polymorphisms in a large-scale Swine F;population using a reference panel including 117 individuals, followed by a series of GWAS analyses. The imputation accuracies reached 0.89 and 0.86 for allelic concordance and correlation, respectively. A quantitative trait nucleotide(QTN) affecting the chest vertebrate was detected directly, while the investigation of another QTN affecting the residual glucose failed due to the presence of similar haplotypes carrying wild-type and mutant allelesin the reference panel used in this study. A high imputation accuracy was confirmed by Sanger sequencing technology for the most significant loci. Two candidate genes,CPNE5 and MYH3, affecting meat-related traits were proposed. Collectively, we illustrated four scenarios in imputation-based GWAS that may be encountered by researchers, and our results will provide an extensive reference for future genotype imputation-based GWAS analyses in the future.

3D Printing of Nacre-Inspired Structures with Exceptional Mechanical and Flame-Retardant Properties

Flame-retardant and thermal management structures have attracted great attention duc to the requirement of high-temperature exposure in industrial,aerospace,and thermal power fields,but the development of protoctive fire-retardant structures with complex shapes to fit arbitrary surfaces is still challenging.Herein,we reported a rotation-blade casting-assisted 3D printing process to fabricate nacre-inspired structures with exceptional mechanical and flame-retardant properties,and the relatedi fundamental mechanisms are studied.3-(Trimethoxysilyl)propyl methacrylate(TMSPMA)modified boron nitride nanoplatelets(BNs)were aligned by rotation-blade casting during the 3D printing process to build the"hrick and mortar"architecture.The 3D printed structures are more lightweight,while having higher fracture toughness than the natural nacre,which is attributed to the crack deflection,aligned BN(a-BNs)bridging,and pull-outs reinforced structures by the covalent bonding between TMSPMA grafted a-BNs and polymer matrix.Thermal conductivity is enhanced by 25.5 times compared with pure polymer and 5.8 times of anisotropy due to the interconnection of a-BNs.3D printed heat-exchange structures with vertically aligned BNs in complex shapes were demonstrated for efficient thermal control of high-power light-emitting diocles.3D printed helmet and armor with a-BNs show exceptional mechanical and fire-retardant properties,demonstrating integrated mechanical and thermal protection.

Whole-genome sequence-based association study for immune cells in an eight-breed pig heterogeneous population

Pigs are an important domestic animal for meat production and animal models for biomedical research such as research on infectious diseases(Meurens et al.,2012).Immune cells,including T cells,B cells,monocytes,and macrophages,are among the major indicators of immune status in health and disease.Revealing the genetic basis of immune cell phenotypes would be helpful for improving the immunity of pigs genetically and reducing the disease occurrence,antibiotic usage.