型壳加热温度对单晶高温合金显微组织及“雀斑”形成的影响

利用所设计的阶梯试样进行定向凝固试验和模拟,研究定向凝固过程型壳加热温度对单晶高温合金铸件显微组织和“雀斑”形成的影响。分析糊状区的温度场及形貌。结果表明,升高型壳加热温度,一次和二次枝晶间距减小,糊状区液相的渗透率和对流通道的宽度降低,“雀斑”形成倾向性降低,“雀斑”宽度减小,“雀斑”区域枝晶碎片减少。此外,随着型壳加热温度的升高,糊状区液相冷却速率增加,糊状区熔体的冷却时间减少,液体流动对枝晶的破碎程度得到削弱,这进一步降低单晶高温合金铸件“雀斑”形成的倾向性。

基于代理模型的风力机轴承疲劳寿命高效估计

双列调心滚子轴承广泛用于不同功率风力机主轴轴承,其结构复杂,工况繁多,以至其疲劳损伤具有极大的离散性,难以实现其使用寿命的快速准确估计。本文提出了一种针对双列滚子轴承疲劳数物融合的快速预估方法。首先结合拉格朗日方程和赫兹接触理论建立了轴承动力学机理仿真模型,然后使用序列加点方法和Kriging插值模型实现了应力的快速仿真,最后结合S-N曲线和累积损伤寿命理论获得轴承的疲劳损伤程度。通过某实际风场的主轴承算例,证明了本文所提方法的精度和计算效率。

Effect of Ti and Al on microstructure and partitioning behavior of alloying elements in Ni-based powder metallurgy superalloys

The microstructure and partitioning behaviors of alloying elements in the γ and γ′ phases in Ni-based powder metallurgy superalloys with different Ti and Al contents were investigated. The results showed that Ti and Al were mainly enriched in the γ′ phase, partially partitioned in the γ matrix, and slightly distributed in the carbides. Different Ti and Al contents in various alloys influenced the composition and amount of MC carbides but did not influence the MC carbides' morphology. With increasing Ti and Al contents, γ + γ′ fan-type structures formed at the grain boundary, eventually resulting in a coarsened γ′ phase. In addition, the morphology of the secondary γ′ phase transformed from nearly spherical to cuboidal. The saturation degrees of Cr, Co, and Mo in the γ matrix were substantially improved with increasing Ti and Al contents.

Effects of oxygen vacancy concentration and temperature on memristive behavior of SrRuO3/Nb:SrTiO3 junctions

Metal/semiconductor memristive heterostructures have potential applications in nonvolatile memory and computing devices.To enhance the performance of the memristive devices,it requires a comprehensive engineering to the metal/semiconductor interfaces.Here in this paper,we discuss the effects of oxygen vacancies and temperature on the memristive behaviors of perovskite-oxide Schottky junctions,each consisting of SrRuO3 thin films epitaxially grown on Nb:SrTiO3 substrates.The oxygen partial pressure and laser fluence are controlled during the film growth to tune the oxygen defects in SrRuO3 films,and the Schottky barrier height can be controlled by both the temperature and oxygen vacancies.The resistive switching measurements demonstrate that the largest resistance switching ratio can be obtained by controlling oxygen vacancy concentration at lower temperature.It suggests that reducing Schottky barrier height can enhance the resistive switching performance of the SrRuO3/Nb:SrTiO3 heterostructures.This work can conduce to the development of high-performance metal-oxide/semiconductor memristive devices.

Revisiting the evolutionary history of domestic and wild ducks based on genomic analyses

Although domestic ducks have been important poultry species throughout human history,their origin remains enigmatic,with mallards and/or Chinese spot-billed ducks being proposed as the direct wild ancestor(s)of domestic ducks.Here,we analyzed 118 whole genomes from mallard,Chinese spotbilled,and domestic ducks to reconstruct their evolutionary history.We found pervasive introgression patterns among these duck populations.Furthermore,we showed that domestic ducks separated from mallard and Chinese spotbilled ducks nearly 38 thousand years ago(kya)and 54 kya,respectively,which is considerably outside the time period of presumed duck domestication.Thus,our results suggest that domestic ducks may have originated from another wild duck population that is currently undefined or unsampled,rather than from present-day mallard and/or Chinese spot-billed ducks,as previously thought.Overall,this study provides new insight into the complex evolution of ducks.

Neutron Powder Diffraction Study on the Non-Superconducting Phases of ThFeAsN1-xOx（x=0.15,0.6）Iron Pnictide

We use neutron powder diffraction to study the non-superconducting phases of ThFeAsN1-xOx with x = 0.15,0.6.In our previous results of the superconducting phase ThFeAsN with Tc = 30 K,no magnetic transition is observed by cooling down to 6 K,and possible oxygen occupancy at the nitrogen site is shown in the refinement[Europhys.Lett.117(2017)57005].Here in the oxygen doped system ThFeAsN1-xOx,two superconducting regions(0≤x≤0.1 and 0.25≤x≤0.55)are identified by transport experiments[J.Phys.:Condens.Matter30(2018)255602].However,within the resolution of our neutron powder diffraction experiment,neither the intermediate doping x= 0.15 nor the heavily overdoped compound x = 0.6 shows any magnetic order from 300 K to 4 K.Therefore,while it shares the common phenomenon of two superconducting domes as most 1111-type iron-based superconductors,the magneticall.y ordered parent compound may not exist in this nitride family.

Effects of Euphorbiasteroid on gene expression in lung cancer cells based on gene chip

Objective Using gene chip technology to explore the molecular mechanism of euphorbiasteroid in the treatment of non-small cell lung cancer(NSCLC).Methods A549 cells were used as the in vitro model,and they were randomly divided into control group and different concentrations of euphorbiasteroid administration groups.Each group had 3 duplicate wells,after the cells were cultured in vitro,the cell viability was evaluated by CCK-8 method.Gene chip technology was used to screen the differentially expressed genes(DEGs)between the control group and the euphorbiasteroid administration group.The differential genes were further analyzed for Gene Ontology(GO)function enrichment and Kyoto Encyclopedia of Genes and Genome(KEGG)pathway enrichment analysis.The STRING online analysis platform combined with Cytoscape software to construct a target protein interaction(PPI)network and perform topological analysis to screen key targets,and use Real-time PCR(RT-PCR)and molecular docking technology to verify key targets.Results According to the analysis of gene chip data,276 differentially expressed genes were screened,including 117 up-regulated genes and 159 down-regulated genes.GO analysis showed that differentially expressed genes were mainly involved in cell division,cell proliferation,cell cycle and other processes,involving protein binding,protein kinase binding and other functions,and were mainly distributed in nucleoplasm,chromosomes and other parts.KEGG signaling pathway analysis showed that differentially expressed genes were involved in cell cycle,pyrimidine metabolism,p53 signaling pathway and other pathways.PPI network analysis showed that CCNA2,TOP2A,CCNB1,CDC20,and RRM2 may be the key targets of euphorbiasteroid in the treatment of NSCLC.RT-PCR results showed that the expressions of CCNA2,TOP2A,CCNB1,CDC20,and RRM2 were significantly down-regulated in the euphorbiasteroid administered group,which was consistent with the gene chip results.Molecular docking results showed that euphorbiasteroid had good affinity with key targets and could bind spontaneously and stably.Conclusion The combination of gene chip,RT-PCR technology and molecular docking technology can find out the differential genes after the intervention of euphorbiasteroid,which can be used to explore the mechanism of euphorbiasteroid in the treatment of NSCLC.

Key genes of deficiency of liver and kidney type chronic pain through bioinformatics analyses

Objective To screen the key genes of chronic pain and provide a reference for the treatment of chronic pain.Methods We performed comprehensive bioinformatics analysis by screening chronic primary pain-related datasets to obtain differentially expressed genes(DEGs)and then imported DEGs into the DAVID database for Gene Ontology(GO)and Kyoto Encyclopedia of Genes and Genomes(KEGG)enrichment analysis.Gene Set Enrichment Analysis(GESA)analysis was done by GSEA_4.1.0 software.At the same time,we imported the intersecting genes into the STRING database and processed them by Cytoscape_3.8.1 software to obtain the protein-protein interaction(PPI)network and the central gene.Results As a result,a total of 54 DEGs were screened,including 47 up-regulated genes,1 down-regulated gene,and 6 genes that were expressed differently in different datasets.23 GO terms and 8 KEGG pathways were enriched by DAVID.PPI network analysis found that SPI1,STAT3,TNFRSF1B,PTGS2,and CXCL1 genes interacted more strongly with other genes,and were predicted to be key genes in chronic primary pain.Conclusion Our results suggested that 5 DEGs,STAT3,SPI1,TNFRSF1B,PTGS2,and CXCL1,have the potential to be used as prognostic and predictive markers for the clinical management of patients with this disease.

Chemical constituents from acid hydrolyzates of Panax quinquefolius total saponins and their inhibition activity to α-glycosidase and protein tyrosine phosphatase 1B

Objective:To investigate the hypoglycemic components from the acid hydrolyzates of Panax quinquefolius total saponins,and screen the active compounds by in vitro inhibitory activities toα-glycosidase enzymes and protein tyrosine phosphatase-1 B(PTP1 B).Methods:The hydrolyzates were chromatographed repeatedly over silica gel column,and the structures of the compounds were determined by means of NMR.The in vitro bioassay was performed through the inhibitory effects onα-glucosidase or/and PTP1 B.Results:Eight compounds were isolated,which identified as 20(S)-panaxadiol(1),(20 S,24 R)-dammarane-20,24-epoxy-3β,6α,12β,25-tetraol(2),20(R)-dammarane-3β,12β,20,25-tetraol(3),20(S)-dammarane-3β,6α,12β,20,25-pentol(4),20(R)-dammarane-3β,12β,20,25-tetrahydroxy-3β-O-β-D-glucopyranoside(5),β-sitosterol(6),oleanolic acid(7)and 20(S)-protopanaxadiol(8).Compound 5 was ginseng triterpenoid isolated from the acid hydrolysates of total saponins from P.quinquefolius for the first time.In this paper,the possible in vitro inhibitory activities were investigated.Compound 5 exhibited significantly inhibitory activity againstα-glucosidase,and the IC50 value[(0.22±0.21)μmol/L]was about 43-fold lower than positive control.For the PTP1 B inhibition assay,compound 5 indicated the strongest inhibitory effect with IC50 of(5.91±0.38)μmol/L,followed by compound 4 with IC50 of(6.21±0.21)μmol/L,which were all showed competitive inhibitory pattern by using a Lineweaver-Burk plot.Conclusion:These results supported the potential application of dammaranes from acid hydrolyzates of P.quinquefolius total saponins can be used as ingredients of ancillary anti-diabetic agent or functional factor.

BaTh2Fe4As4(N0.7O0.3)2: An iron-based superconductor stabilized by inter-block-layer charge transfer

The discovery of superconductivity at Tc = 26 K in fluorine-doped LaFeAsO [1] has led to the subsequent findings of dozens of new superconducting materials in the class of Fe-based superconductors (FeSCs)[2,3]. All those FeSCs were found to possess antifluorite-like Fe2X2 (X = As, Se) layers which were believed to be the crucial structural motif for the emergence of high-temperature superconductivity. This common feature makes it possible to design a new FeSC with the crystal chemistry [3-5]. For example, with the consideration of the intergrowth of BaFe2As2 and BaTi2As2O, the new FeSC Ba2Fe2Ti2As4O (Tc=21 K) was discovered [6]. The block-layer-design approach was also demonstrated to be effective for other class of layered materials, such as Eu3Bi2S4F4 [7], LaPb- BiS3O [8], La5Cu4As4O4C12 [9], Pb5BiFe3O10Cl2 [10], and Bi4Q4CU1.7Se2.7CI03 [11].

Multiple positive periodic solutions for a generalized delayed population model with an exploited term

In this paper, the existence of two positive periodic solutions for a generalized delayed population model with an exploited term is established by using the continuation theorem of the coincidence degree theory.

Synthesis,Structure and Properties of Layered Phosphide Nitrides AkTh_(2)Mn_(4)P_(4)N_(2)(Ak=Rb,Cs)

Main observation and conclusion We report the design,synthesis,structure,and properties of two complex layered phosphide nitrides,AkTh_(2)Mn_(4)P_(4)N_(2)(Ak=Rb,Cs),which contain anti-fluorite-type[Mn_(2)P_(2)]bilayers separated by fluorite-type[Th_(2)N_(2)]layers as a result of the intergrowth between AkMn2P2 and ThMnPN.The new compounds are featured with an intrinsic hole doping associated with the interlayer charge transfer and a built-in chemical pressure from the[Th_(2)N_(2)]layers,both of which are reflected by the changes in the lattice and the atomic position of phosphorus.The measurements of magnetic susceptibility,electrical resistivity,and specific heat indicate existence of local moments as well as itinerant electrons in relation with d-p hybridizations.The expected dominant antiferromagnetic interactions with enhanced d-p hybridizations were demonstrated by the first-principles calculations only when additional Coulomb repulsions are included.The density of states at the Fermi level derived from the specific-heat analysis are 3.5 and 7.5 times of the calculated ones for Ak=Rb and Cs,respectively,suggesting strong electron correlations in the title compounds.