AZ31B 镁合金板材中晶界滑移的晶体塑性仿真

建立一种耦合滑移、动态再结晶以及晶界滑移的晶体塑性模型以仿真镁合金的高温变形行为及织构演化。首先,通过实验测量单轴拉伸、压缩后的织构以及显微组织演化,研究AZ31B镁合金在300°C的变形机制。结果发现,动态再结晶在应变小于0.2时起到细化晶粒的作用,之后晶界滑移在变形过程中起显著作用。此外,建立晶界滑移模型来评估由晶界滑移产生的应变以及晶粒转动,并与多晶体塑性模型VPSC相耦合。所建立的VPSC-DRX-GBS模型可以很好地计算应力−应变曲线、晶粒尺寸、织构演化以及实验中所发现的拉伸与压缩织构演化显著差异。计算的晶界滑移贡献率在拉伸条件下显著高于压缩条件的,这是由于在拉伸时晶界上更易产生孔洞形核。

铝合金应变诱导晶粒异常长大行为的晶体塑性-相场法耦合模拟

提出一种预测变形铝合金在退火过程中应变诱导晶粒异常长大行为的介观耦合建模方法。基于晶体塑性有限元法(CPFE)计算塑性变形中的位错密度和变形储能分布;以储能和局部界面曲率为晶界迁移驱动力,建立基于连续场法的改进相场(PF)模型,并采用插值法将CPFE计算结果向PF模型进行映射,实现CPFE-PF的耦合模拟。采用理想双晶组织模拟初步校准PF模型,然后将该CPFE-PF耦合模型应用于变形AA3102铝合金退火过程的多晶组织演化模拟,进一步验证模型有效性。结果表明,退火时变形基体中的低储能形核点优先长大;而当变形量在临界塑性应变附近时,由于结晶形核数量的有限性和储能分布的不均匀性,将产生晶粒异常长大现象。

Population and conservation status of a transboundary group of black snub-nosed monkeys(Rhinopithecus strykeri)between China and Myanmar

DEAR EDITOR,We examined the distribution,population,and conservation status of the critically endangered Myanmar or black snub-nosed monkey(Rhinopithecus strykeri)via field surveys over 26 months(2019-2021)in the Pianma region of the China-Myanmar border.Contrary to previous reports,we only identified one group in the region,which was a cross-border group occupying a multi-year home range of 51.50-57.02 km^(2).The current group size was much larger(155-160 individuals)than that in 2012-2014(ca 100 individuals),and the group appeared to be growing.However,confirmed poaching,mining,and transboundary forest fires on the Myanmar side of the border threaten their survival.

Controllable synthesis and photocatalytic activities of rod-shaped mesoporous titanosilicate composites with varied aspect ratios

Rod-shaped mesoporous titanosilicate composites （RMTSs） with controllable aspect ratios （ARs） were fabricated using cetyltrimethylammonium bromide （CTAB） and ammonium hydroxide （NH4OH） at a continuous stirring rate, resulting in ARs ranging from 1 to 5. Slowing the stirring rate or increasing the concentration of CTAB mainly impacted the length growth, whereas NH4OH affected the width growth. Photocatalytic activity studies revealed that the length of RMTSs played a more significant role than the width at lower ARs in their photocatalytic activity.

How to disentangle microbially functional complexity: an insight from the network analysis of C, N, P and S cycling genes

A complete ecosystem is also a complex network in which multifarious species interact with each other to achieve system-level functions, such as nutrient biogeochemistry (1)Microbial community is commonly considered as the primary driving force of ecosystem nutrient mobilization and metabolism, especially carbon (C), nitrogen (N), phosphorus (P), sulfur (S) and methane coupling process (2)The rise of metagenomics and high-throughput array (e.g. PhyloChip, GeoChip, etc.

Experimental observation of topological Hall effects in compensated ferrimagnet-heavy metal layered structures

The topological Hall effect(THE) as a powerful probe for the experimental observation of topological spin textures, such as magnetic skyrmions, has been observed in a wide variety of distinct material systems. However, limited experimental observations have been reported for antiferromagnetic(AFM) materials. Here, the THE signals in the AFM state were observed in compensated ferrimagnetic thin films interfaced with heavy metals at the magnetization compensation temperature(TM).Ferrimagnetic CoTb thin films grown on Pt thin films were used in the experiments. The Co Tb films exhibited a magnetization compensation point at which the moments of Co and Tb sublattices canceled each other, giving rise to the AFM state. The temperature(T)-dependent Hall measurements showed anomalous Hall effect(AHE) and THE responses at T≠T_(M) but pure THE responses at T=T_(M). Control measurements and analyses suggest that the THE responses are associated with interfacial Dzyaloshinskii-Moriya interaction(DMI) rather than the overlapping of different AHE signals in the structure. This work presents the first-ever observation of interfacial DMI-induced THE in AFM metal trilayered systems and demonstrates a new approach for electrical reading of chiral spin textures in AFM thin film-based heterostructures.

Spontaneous positive exchange bias effect in SrFeO_(3-x)/SrCoO_(3-x) epitaxial bilayer

A novel phenomenon of spontaneous positive exchange bias(PEB)is reported in SrFeO_(3-x)/SrCoO_(3-x) epitaxial bilayer without undergoing any magnetic field treatment.When inserting a thick SrTiO3(STO)nonmagnetic spacer(about 6 nm)into the bilayer interface,this phenomenon still exists.Based on a series of testing means,the spontaneous PEB effect is supposed to be mainly related to short-range ferromagnetic(FM)exchange coupling at the interface when there is no STO spacer.As the STO interlayer reaches up to a certain thickness,shortrange coupling interaction basically disappears.At this time,the long-range dipole field may be responsible for the coupling of the FM and antiferromagnetic(AFM)layer across the nonmagnetic STO and then leads to the same bias effect.Our discoveries provide a new way to realize and manipulate spontaneous exchange bias-based spintronics devices,such as magnetic recording heads and spin valves.

Metabolic diversification of anaerobic methanotrophic archaea in a deep-sea cold seep

Anaerobic methanotrophic archaea(ANME)can assimilate methane and govern the greenhouse effect of deep-sea cold seeps.In this study,a total of 13 ANME draft genomes representing five ANME types(ANME-la,ANME-lb,ANME-2a,ANME-2b and ANME-2c),in size between 0.8 and 1.8 Mbp,were obtained from the Jiaolong cold seep in the South China Sea.The small metagenome-assembled genomes(MAGs)contained all the essential pathways for methane oxidization and carbon dioxide fixation.All genes related to nitrate and sulfate reduction were absent from the MAGs,indicating their syntrophic dependence on partner organisms.Aside from acetate secretion and sugar storage,propanoate synthesis pathway,as an alternative novel carbon flow,was identified in all the MAGs and transcriptionally active.Regarding type-specific features of the MAGs,the genes encoding archaellum and bacteria-derived chemotaxis were specific to ANME-2,perhaps for fitness under fluctuation of methane and sulfate concentration flux.Our genomic and transcriptomic results strongly suggested that ANME could carry out simple carbon metabolism from Cl assimilation to C3 biosynthesis in the SCS cold seep,which casts light on a novel approach for synthetic biology.