High-resolution Transmission Electron Microscopy Characterization of the Structure of Cu Precipitate in a Thermal-aged Multicomponent Steel

High-dispersed nanoscale Cu precipitates often contribute to extremely high strength due to precipitation hardening,and whereas usually lead to degraded toughness for especially ferritic steels.Hence,it is important to understand the formation behaviors of the Cu precipitates.High-resolution transmission electron microscopy(TEM)is utilized to investigate the structure of Cu precipitates thermally formed in a high-strength low-alloy(HSLA)steel.The Cu precipitates were generally formed from solid solution and at the crystallographic defects such as martensite lath boundaries and dislocations.The Cu precipitates in the same aging condition have various structure of BCC,9 R and FCC,and the structural evolution does not greatly correlate with the actual sizes.The presence of different structures in an individual Cu precipitate is observed,which reflects the structural transformation occurring locally to relax the strain energy.The multiply additions in the steel possibly make the Cu precipitation more complex compared to the binary or the ternary Fe-Cu alloys with Ni or Mn additions.This research gives constructive suggestions on alloying design of Cu-bearing alloy steels.

Mophological and Molecular Identification of Potato Cyst Nematode from Sichuan,China

[Objectives]The infection symptoms of cyst nematodes were found in Yuexi, Sichuan. In order to identify the pathogen, the isolated nematodes were identified by morphology and molecular biology. [Methods] The potato roots and soil around the roots were collected, the nematodes in the roots were stained and observed, and the cysts were separated by the simple floating method. The second-stage juveniles(J2 s), females and cysts were found, and they were photographed and morphologically measured. The DNA of cysts and J2 s were extracted and identified by species-specific PCR. The DNA sequences of 18 S gene, 28 S D2-D3 region and ITS region in ribosomal DNA were obtained. Sequences of some cyst nematode species were downloaded from GenBank for sequence alignment, and MrBayes 3.2.3 software was used to construct a Bayesian phylogenetic tree. [Results] The nematodes could invade hosts’ root system. The basal knobs of J2 s was nearly round and inclined backward;the average length of the stylet was shorter than 23 μm;the Granek ratio of cysts was greater than or equal to 3, which is highly consistent with that of Globodera rostochiensis. The DNA templates of three cysts and four J2 s were amplified by species-specific PCR, and a band of about 430 bp was obtained. After further sequencing, the length was 434 bp, which is consistent with G. rostochiensis. The evolutionary analysis of rDNA 18 S and 28 S showed that the cyst nematode population was a Globodera species, and further evolutionary analysis of ITS gene confirmed that the population was G. rostochiensis. [Conclusions] The nematodes are G. rostochiensis, which is a quarantine species of great concern to both domestic and import quarantine. Once introduced and colonized, it is hard to eradicate. It is necessary to establish a monitoring system as soon as possible, strengthen the quarantine, supervision and management, increase investment in G. rostochiensis research and development, and develop detection and control technologies, so as to escort the healthy and sustainable development of China’s potato industry.

Auxiliary generative mutual adversarial networks for class-imbalanced fault diagnosis under small samples

The effect of intelligent fault diagnosis of mechanical equipment based on data-driven is often premised on big data and class-balance.However,due to the limitation of working environment,operating conditions and equipment status,the fault data collected by mechanical equipment are often small and imbalanced with normal samples.Therefore,in order to solve the abovementioned dilemma faced by the fault diagnosis of practical mechanical equipment,an auxiliary generative mutual adversarial network(AGMAN)is proposed.Firstly,the generator combined with the auto-encoder(AE)constructs the decoder reconstruction feature loss to assist it to complete the accurate mapping between noise distribution and real data distribution,generate highquality fake samples,supplement the imbalanced dataset to improve the accuracy of small sample class-imbalanced fault diagnosis.Secondly,the discriminator introduces a structure with unshared dual discriminators.Realize the mutual adversarial between the dual discriminator by setting the scoring criteria that the dual discriminator are completely opposite to the real and fake samples,thus improving the quality and diversity of generated samples to avoid mode collapse.Finally,the auxiliary generator and the dual discriminator are updated alternately.The auxiliary generator can generate fake samples that deceive both discriminators at the same time.Meanwhile,the dual discriminator cannot give correct scores to the real and fake samples according to their respective scoring criteria,so as to achieve Nash equilibrium.Using three different test-bed datasets for verification,the experimental results show that the proposed method can explicitly generate highquality fake samples,which greatly improves the accuracy of class-unbalanced fault diagnosis under small sample,especially when it is extremely imbalanced,after using this method to supplement fake samples,the fault diagnosis accuracy of DCNN and SAE are relatively big improvements.So,the proposed method provides an effective solution for small sample class-unbalanced fault diagnosis.

大豆异黄酮genistein的长期暴露通过下调MCM复合物抑制胆囊癌增殖的研究

大豆异黄酮是天然的酪氨酸激酶抑制剂,与多种肿瘤发病率和死亡率的降低密切相关.同时,酪氨酸激酶如ERBB2的激活是胆囊炎转化为胆囊癌的重要机制,因此,研究长期接触大豆异黄酮与胆囊癌的发生和发展之间的关系十分重要.这项85对的病例对照研究发现,高血浆大豆异黄酮genistein水平与较低的胆囊癌风险相关(≥326.0与≤19.3 ng/mL对比,OR=0.15,95%可信区间0.04~0.59;趋势检验P=0.016),并且genistein暴露水平与胆囊癌组织中Ki67表达负相关(85例).与这些结果一致,体外和体内的长期genistein暴露模型中,胆囊癌细胞的增殖受到抑制.长期暴露于genistein降低了ERBB2的酪氨酸激酶活性,并影响了PTK6-AKT-GSK3β轴的功能,导致胆囊癌细胞中MCM复合物的表达下调.总之,长期接触与大豆制品摄入相关的genistein可能在预防甚至抑制胆囊癌的增殖方面起到一定的作用.

Compositional Variants of Cu-rich Precipitate in Thermally Aged Ferritic Steel

Atom probe tomography was utilized to investigate Cu precipitation in a high-strength low-alloy steel isothermally aged at 500℃ for 1, 4, 16, and 64 h after water-quenching from 900℃. With prolonged aging time, the Curich precipitates（CRPs） increased in size and decreased in number density, and gradually evolved from spheroidal to elliptical in morphology. The small CRPs were rich in a high amount of Fe and a certain amount of Ni and Mn at their early nucleation stage. The large CRPs with increased size due to extensive aging contained less Fe and more Cu at their later growth stage. Additionally, Ni and Mn were both readily to segregate at the CRP/matrix heterophase interfaces, and Mn was higher in content than Ni in the precipitate interior especially when the CRPs were large in size.

Chemical, microstructure, and mechanical property of TiAl alloys produced by high-power direct laser deposition

Additive manufactured metals sometimes exhibit extraordinary microstructures and mechanical properties due to the particular processes. In this paper, we focus on a novel gradient TiAl alloys fabricated byhigh-power direct laser deposition, whose chemical composition, microstructure, and mechanical property vary along the building direction. The results indicate that Al concentration dramatically decreasesfrom 39.5 at.% to 30.1 at.% as the height increases from the bottom to the top. Meanwhile, microstructural characterization indicates that the specimen appears basket-weave microstructure at the bottom,then the α_(2) and γ phase gradually decrease, and eventually it transforms into acicular martensite microstructure in the top region. The indentation analysis shows that the associated hardness increases asthe height increases, while the plasticity reaches a minimum value in the middle region. The increasingamount of β_(o)(ω) is considered to be responsible for the increasing hardness because of the strong precipitation strengthening effect. The high plasticity in the bottom and top regions results from the strongdeformation behaviors of the γ and β_(o) phases.

Visualization of microstructural factors resisting the crack propagation in mesosegregated high-strength low-alloy steel

While relationship between fracture mechanism and homogeneous microstructures has been fully understood,relationship between fracture mechanism and inhomogeneous microstructures such as the mesosegregation receives less attention as it deserves.Fracture mechanism of the high-strength low-alloy(HSLA)steel considering the mesosegregation was investigated and its corre s ponding micro structure was characterized in this paper.Mesosegregation re fers to the inhomogeneous distribution of alloy elements during casting solidification,and leads to the formation of positive segregation zones(PSZ)and negative segregation zones(NSZ)in ingots.The fracture surface of impact sample exhibits the quasi-cleavage fracture at-21℃,and is divided into ductile and brittle fracture zone.Meanwhile,the PSZ and NSZ spread across ductile and brittle fracture zone randomly.In ductile fracture zone,micro-voids fracture mechanism covers the PSZ and NSZ,and higher deformation degree is shown in the PSZ.In brittle fracture zone,secondary cleavage cracks are observed in both PSZ and NSZ,but present bigger size and higher quantity in the NSZ.However,some regions of the PSZ still present micro-voids fracture mechanism in brittle fracture zone.It reveals that the microstructures in the PSZ exhibit a higher resistance ability to crack propagation than that in the NSZ.All observations above provide a better visualization of the microstructural factors that resist the crack propagation.It is important to map all information regarding the fracture mechanism and mesosegregation to allow for further acceptance and industrial use.