不同预时效挤压态Mg−Gd−Y−Zn−Zr合金的再结晶行为和强化机制

通过控制预时效时间制备3种不同状态的试样,研究不同预时效状态对挤压态Mg−9.5Gd−4Y−2.2Zn−0.5Zr(质量分数,%)合金的动态再结晶行为(DRX)和性能的影响。结果表明,欠时效挤压(UAE)样品的细晶体积分数为17.4%,而峰时效挤压(PAE)和过时效挤压(OAE)样品的细晶体积分数分别达到89.7%和50.4%。在晶粒内部和晶界处分布的致密、细小的β颗粒相通过粒子激发形核机制显著提高了形核位点和位错密度。然而,致密针状γ'相抑制位错滑移,延迟DRX形核。PEA和OAE样品中细小晶粒的差异归因于原始颗粒相的数量和尺寸的不同,而其拉伸性能的差异归因于不同的显微组织。由于晶界强化和析出强化机制的贡献更大,PAE样品具有更优异的拉伸性能。

基础学科高层次、多元化拔尖创新研究生培养的理念与实践——以北京大学化学学科研究生培养为例

基础学科拔尖创新人才培养是高校人才培养工作的重要任务。北京大学化学学科以培养“具有健全人格、独立思辨能力和国际竞争力”的杰出人才为使命,致力于培养热爱祖国、崇尚科学,具有高度社会责任感和科学文化素养的化学及相关领域的引领型人才。历经多年实践探索和传承发展,北大化学不断摸索出一条培养目标明确、培养特色鲜明、培养制度完善,培养成效显著的人才培养之路。与此同时,随着国际科技和人才竞争的加剧,对我国化学学科人才培养提出了新的迫切要求,北大化学也在根据新形势不断探索人才分类培养、本博贯通培养、高层次创新人才培养等人才培养新举措。

Confirmation of a Sub-Saturn-size Transiting Exoplanet Orbiting a G Dwarf:TOI-1194 b and a Very Low Mass Companion Star: TOI-1251 B from TESS

We report the confirmation of a sub-Saturn-size exoplanet,TOI-1194 b,with a mass of about 0.456+0.055-0.051M_(J),and a very low mass companion star with a mass of about 96.5±1.5 MJ,TOI-1251 B.Exoplanet candidates provided by the Transiting Exoplanet Survey Satellite(TESS)are suitable for further follow-up observations by ground-based telescopes with small and medium apertures.The analysis is performed based on data from several telescopes worldwide,including telescopes in the Sino-German multiband photometric campaign,which aimed at confirming TESS Objects of Interest(TOIs)using ground-based small-aperture and medium-aperture telescopes,especially for long-period targets.TOI-1194 b is confirmed based on the consistent periodic transit depths from the multiband photometric data.We measure an orbital period of 2.310644±0.000001 days,the radius is 0.767+0.045-0.041RJ and the amplitude of the RV curve is 69.4_(-7.3)^(+7.9)m s^(-1).TOI-1251 B is confirmed based on the multiband photometric and high-resolution spectroscopic data,whose orbital period is 5.963054+0.000002-0.000001days,radius is 0.947+0.035-0.033 R_(J) and amplitude of the RV curve is 9849_(-40)^(+42)ms^(-1).

Human-like adrenal features in Chinese tree shrews revealed by multi-omics analysis of adrenal cell populations and steroid synthesis

The Chinese tree shrew(Tupaia belangeri chinensis)has emerged as a promising model for investigating adrenal steroid synthesis,but it is unclear whether the same cells produce steroid hormones and whether their production is regulated in the same way as in humans.Here,we comprehensively mapped the cell types and pathways of steroid metabolism in the adrenal gland of Chinese tree shrews using single-cell RNA sequencing,spatial transcriptome analysis,mass spectrometry,and immunohistochemistry.We compared the transcriptomes of various adrenal cell types across tree shrews,humans,macaques,and mice.Results showed that tree shrew adrenal glands expressed many of the same key enzymes for steroid synthesis as humans,including CYP11B2,CYP11B1,CYB5A,and CHGA.Biochemical analysis confirmed the production of aldosterone,cortisol,and dehydroepiandrosterone but not dehydroepiandrosterone sulfate in the tree shrew adrenal glands.Furthermore,genes in adrenal cell types in tree shrews were correlated with genetic risk factors for polycystic ovary syndrome,primary aldosteronism,hypertension,and related disorders in humans based on genome-wide association studies.Overall,this study suggests that the adrenal glands of Chinese tree shrews may consist of closely related cell populations with functional similarity to those of the human adrenal gland.Our comprehensive results(publicly available at http://gxmujyzmolab.cn:16245/scAGMap/)should facilitate the advancement of this animal model for the investigation of adrenal gland disorders.

Metformin promotes anti-tumor immunity in STK11 mutant NSCLC through AXIN1-dependent upregulation of multiple nucleotide metabolites

Background:Metformin has pleiotropic effects beyond glucose reduction,including tumor inhibition and immune regulation.It enhanced the anti-tumor effects of programmed cell death protein 1(PD-1)inhibitors in serine/threonine kinase 11(STK11)mutant non-small cell lung cancer(NSCLC)through an axis inhibition protein 1(AXIN1)-dependent manner.However,the alterations of tumor metabolism and metabolites upon metformin administration remain unclear.Methods:We performed untargeted metabolomics using liquid chromatography(LC)-mass spectrometry(MS)/MS system and conducted cell experiments to verify the results of bioinformatics analysis.Results:According to the Kyoto Encyclopedia of Genes and Genomes(KEGG)pathway database,most metabolites were annotated into metabolism,including nucleotide metabolism.Next,the differentially expressed metabolites in H460(refers to H460 cells),H460_met(refers to metformin-treated H460 cells),and H460_KO_met(refers to metformin-treated Axin1-/-H460 cells)were distributed into six clusters based on expression patterns.The clusters with a reversed expression pattern upon metformin treatment were selected for further analysis.We screened out metabolic pathways through KEGG pathway enrichment analysis and found that multiple nucleotide metabolites enriched in this pathway were upregulated.Furthermore,these metabolites enhanced the cytotoxicity of activated T cells on H460 cells in vitro and can activate the stimulator of the interferon genes(STING)pathway independently of AXIN1.Conclusion:Relying on AXIN1,metformin upregulated multiple nucleotide metabolites which promoted STING signaling and the killing of activated T cells in STK11 mutant NSCLC,indicating a potential immunotherapeutic strategy for STK11 mutant NSCLC.

Platelet-derived microparticles and their cargos: The past, present and future

All eukaryotic cells can secrete extracellular vesicles, which have a double-membrane structure and are important players in the intercellular communication involved in a variety of important biological processes. Platelets form platelet-derived microparticles (PMPs) in response to activation, injury, or apoptosis. This review introduces the origin, pathway, and biological functions of PMPs and their importance in physiological and pathological processes. In addition, we review the potential applications of PMPs in cancer, vascular homeostasis, thrombosis, inflammation, neural regeneration, biomarkers, and drug carriers to achieve targeted drug delivery. In addition, we comprehensively report on the origin, biological functions, and applications of PMPs. The clinical transformation, high heterogeneity, future development direction, and limitations of the current research on PMPs are also discussed in depth. Evidence has revealed that PMPs play an important role in cell-cell communication, providing clues for the development of PMPs as carriers for relevant cell-targeted drugs. The development history and prospects of PMPs and their cargos are explored in this guidebook.

V0405 Dra:A New Deep and Low Mass Ratio Contact Binary with Extremely Fast Decrease in the Orbital Period

V0405 Dra is a W UMa-type binary star.Based on the TESS data,we have conducted an orbital period study and performed a light curve analysis for the system.The orbital period study reveals that the O-C curve for V0405 Dra exhibits secular decrease at an extremely high rate of d P/dt=-2.71×10^(-6)day year^(-1),along with periodic variations characterized by an amplitude of A_(3)=0.0032 day and a period of P_(3)=1.413 years.The orbital periodic change is possibly due to the light-travel time effect resulting from an additional third body in the system,for which we estimate a minimum mass of M_(3)=0.77M_(⊙).By employing the 2013 version of the Wilson-Devinney(W-D)method to synthesize a light curve,we derived photometric solutions indicating that V0405 Dra is a new deep(f=68.7%)and low-mass ratio(q=0.175)contact binary.The fast decrease in its orbital period is likely caused by mass transfer from the more massive primary star to the less massive secondary star,or due to angular momentum loss.With further mass transfer and loss of angular momentum,the binary will gradually evolve into a tighter contact configuration,eventually leading to a merger into a single star,following the evolutionary paths suggested for such deep and low mass ratio contact binaries.

Identification and validation of a new prognostic signature based on cancer-associated fibroblast-driven genes in breast cancer

BACKGROUND Breast cancer(BC),a leading malignant disease,affects women all over the world.Cancer associated fibroblasts(CAFs)stimulate epithelial-mesenchymal transition,and induce chemoresistance and immunosuppression.AIM To establish a CAFs-associated prognostic signature to improve BC patient out-come estimation.METHODS We retrieved the transcript profile and clinical data of 1072 BC samples from The Cancer Genome Atlas(TCGA)databases,and 3661 BC samples from the The Gene Expression Omnibus.CAFs and immune cell infiltrations were quantified using CIBERSORT algorithm.CAF-associated gene identification was done by weighted gene co-expression network analysis.A CAF risk signature was established via univariate,least absolute shrinkage and selection operator regression,and mul-tivariate Cox regression analyses.The receiver operating characteristic(ROC)and Kaplan-Meier curves were employed to evaluate the predictability of the model.Subsequently,a nomogram was developed with the risk score and patient clinical signature.Using Spearman's correlations analysis,the relationship between CAF risk score and gene set enrichment scores were examined.Patient samples were collected to validate gene expression by quantitative real-time polymerase chain reaction(qRT-PCR).RESULTS Employing an 8-gene(IL18,MYD88,GLIPR1,TNN,BHLHE41,DNAJB5,FKBP14,and XG)signature,we attemp-ted to estimate BC patient prognosis.Based on our analysis,high-risk patients exhibited worse outcomes than low-risk patients.Multivariate analysis revealed the risk score as an independent indicator of BC patient prognosis.ROC analysis exhibited satisfactory nomogram predictability.The area under the curve showed 0.805 at 3 years,and 0.801 at 5 years in the TCGA cohort.We also demonstrated that a reduced CAF risk score was strongly associated with enhanced chemotherapeutic outcomes.CAF risk score was significantly correlated with most hallmark gene sets.Finally,the prognostic signature were further validated by qRT-PCR.CONCLUSION We introduced a newly-discovered CAFs-associated gene signature,which can be employed to estimate BC patient outcomes conveniently and accurately.

Hydrogen generation from NaBH_(4) for portable proton exchange membrane fuel cell

Sodium borohydride(NaBH_(4)) is considered as the most potential hydrogen storage material for portable proton exchange membrane fuel cells(PEMFC)because of its high theoretical hydrogen capacity.However,the slow and poor kinetic stability of hydrogen generation from NaBH_(4) hydrolysis limits its application.There are two main factors influencing the kinetics stability of hydrogen generation from NaBH_(4).One factor is that the alkaline byproducts(NaBO_(2)) of the hydrolysis reaction can increase the pH of the solution,thus inhibiting the reaction process.It mainly happens in the NaBH_(4) solution hydrolysis system.Another factor is that the monotonous increase in reaction temperature leads to uncontrollable and unpredictable hydrolysis rates in the solid NaBH_(4) hydrolysis system.This is due to the excess heat generated from this exothermic reaction in the initial reaction of NaBH_(4) hydrolysis.In this perspective,we summarize the latest research progress in hydrogen generation from NaBH_(4) and emphasize the design principles of catalysts for hydrogen generation from NaBH_(4) solution and solid state NaBH_(4).The importance of carbon as catalyst support material for NaBH_(4) hydrolysis is also highlighted.

All-optical controlled-NOT logic gate achieving directional asymmetric transmission based on metasurface doublet

Optical logic gates play important roles in all-optical logic circuits,which lie at the heart of the next-generation optical computing technology.However,the intrinsic contradiction between compactness and robustness hinders the development in this field.Here,we propose a simple design principle that can possess multiple-input-output states according to the incident circular polarization and direction based on the metasurface doublet,which enables controlled-NOT logic gates in infrared region.Therefore,the directional asymmetric electromagnetic transmission can be achieved.As a proof of concept,a spin-dependent Janus metasurface is designed and experimentally verified that four distinct images corresponding to four input states can be captured in the far-field.In addition,since the design method is derived from geometric optics,it can be easily applied to other spectra.We believe that the proposed metasurface doublet may empower many potential applications in chiral imaging,chiroptical spectroscopy and optical computing.

实验室无水无氧手套箱操作和安全运行管理的探索和实践

近年来,化学实验室中无水无氧手套箱的普及率日渐提高,手套箱被广泛应用在有机合成、锂电池制造和研究、OLED (有机发光二极管)封装、对水氧敏感试剂的存储与分装等方面。在手套箱的使用及维护过程中,涉及强还原性金属试剂、气体钢瓶、易燃废弃物等多种危险源,因此存在安全隐患,容易引发安全事故。本文介绍了实验室无水无氧手套箱的安全操作方法和南京大学化学化工学院探索的手套箱新型管理办法。学院开创性地制作了手套箱安全使用视频并应用于安全培训中,制订并执行了手套箱使用记录以及手套箱净化柱材料更换备案的管理办法。该方法取得了良好的运行管理效果,可为国内外同类型化学实验室手套箱的安全管理提供借鉴和参考。

Phellinus igniarius ameliorates renal aging in a rat model of focal and segmental glomerulosclerosis

Objective:To comparatively investigate the ameliorative effect of Phellinus igniarius(P.igniarius)on renal aging in a rat model of focal and segmental glomerulosclerosis(FSGS).Methods:The FSGS model was established in rats by uninephrectomy combined with tail vein injection of doxorubicin.The FSGS rats were randomly divided into the model group,the P.igniarius decoction group,the P.igniarius polysaccharides group,and the P.igniarius polyphenols group.Molecular indicators of cell senescence,renal function indexes,and podocyte injury markers were tested after ten weeks of intragastric administration.Besides,the pathological renal lesions and the ultrastructural changes were observed.Results:FSGS developed in the model group within ten weeks and showed segmental glomerular scarring and renal aging.Following the 10-week intervention,24 h proteinuria,serum creatinine,blood urea nitrogen,P16^(INK4α),thrombospondin-1,and transforming growth factor-β1 were decreased in each treatment group,whereas albumin,erythropoietin,nephrin,and podocin were increased;the pathological renal injury was alleviated,and the number of senescent cells was reduced,especially in rats treated with P.igniarius decoction.Conclusions:P.igniarius ameliorates renal aging and renal injury in the FSGS rat model.Compared with the effective constituents(polysaccharides and polyphenols),P.igniarius decoction has a better curative effect,which is expected to provide a new therapeutic idea for FSGS.

Dietary fiber during gestation improves lactational feed intake of sows by modulating gut microbiota

Background The feed intake of sows during lactation is often lower than their needs.High-fiber feed is usually used during gestation to increase the voluntary feed intake of sows during lactation.However,the mechanism underlying the effect of bulky diets on the appetites of sows during lactation have not been fully clarified.The current study was conducted to determine whether a high-fiber diet during gestation improves lactational feed intake(LFI)of sows by modulating gut microbiota.Methods We selected an appropriate high-fiber diet during gestation and utilized the fecal microbial transplanta-tion(FMT)method to conduct research on the role of the gut microbiota in feed intake regulation of sows during lactation,as follows:high-fiber(HF)diet during gestation(n=23),low-fiber(LF)diet during gestation(n=23),and low-fiber diet+HF-FMT(LFM)during gestation(n=23).Results Compared with the LF,sows in the HF and LFM groups had a higher LFI,while the sows also had higher peptide tyrosine tyrosine and glucagon-like peptide 1 on d 110 of gestation(G110 d).The litter weight gain of piglets during lactation and weaning weight of piglets from LFM group were higher than LF group.Sows given a HF diet had lower Proteobacteria,especially Escherichia-Shigella,on G110 d and higher Lactobacillus,especially Lactobacil-lus_mucosae_LM1 and Lactobacillus_amylovorus,on d 7 of lactation(L7 d).The abundance of Escherichia-Shigella was reduced by HF-FMT in numerically compared with the LF.In addition,HF and HF-FMT both decreased the perinatal concentrations of proinflammatory factors,such as endotoxin(ET),lipocalin-2(LCN-2),tumor necrosis factor-α(TNF-α),and interleukin-1β(IL-1β).The concentration of ET and LCN-2 and the abundance of Proteobacteria and Escheri-chia-Shigella were negatively correlated with the LFI of sows.Conclusion The high abundance of Proteobacteria,especially Escherichia-Shigella of LF sows in late gestation,led to increased endotoxin levels,which result in inflammatory responses and adverse effects on the LFI of sows.Add-ing HF during gestation reverses this process by increasing the abundance of Lactobacillus,especially Lactobacil-lus_mucosae_LM1 and Lactobacillus_amylovorus.

SUMO1 regulates post-infarct cardiac repair based on cellular heterogeneity

Small ubiquitin-related modifier(SUMOylation)is a dynamic post-translational modification that maintains cardiac function and can protect against a hypertrophic response to cardiac pressure overload.However,the function of SUMOylation after myocardial infarction(MI)and the molecular details of heart cell responses to SUMO1 deficiency have not been determined.In this study,we demonstrated that SUMO1 protein was inconsistently abundant in different cell types and heart regions after MI.However,SUMO1 knockout significantly exacerbated systolic dysfunction and infarct size after myocardial injury.Single-nucleus RNA sequencing revealed the differential role of SUMO1 in regulating heart cells.Among cardiomyocytes,SUMO1 deletion increased the Nppa^(+)Nppb^(+)Ankrd1^(+)cardiomyocyte subcluster pro-portion after MI.In addition,the conversion of fibroblasts to myofibroblasts subclusters was inhibited in SUMO1 knockout mice.Importantly,SUMO1 loss promoted proliferation of endothelial cell subsets with the ability to reconstitute neovascularization and expressed angiogenesis-related genes.Computational analysis of ligand/receptor interactions suggested putative pathways that mediate cardiomyocytes to endothelial cell communication in the myocardium.Mice preinjected with cardiomyocyte-specific AAV-SUMO1,but not the endothelial cell-specific form,and exhibited ameliorated cardiac remodeling following MI.Collectively,our results identified the role of SUMO1 in cardiomyocytes,fibroblasts,and endothelial cells after MI.These findings provide new insights into SUMO1 involvement in the patho-genesis of MI and reveal novel therapeutic targets.

Low-cycle fatigue behaviour of Mg-9Gd-4Y-2Zn-0.5Zr alloys with different structures

The strain-controlled cyclic deformation behaviour of Mg-9Gd-4Y-2Zn-0.5Zr with different structures was investigated. Alloys were prepared by solution, extrusion and pre-ageing extrusion, and the microstructures before and after the fatigue tests were characterized.Experimental results indicated that the bimodal structure owned the better performance in fatigue test, which was attributed to the higher yield strength. For the equiaxed structure, cyclic hardening induced stress concentration until the failure. Stable cyclic deformation and persistent cyclic softening played an important role at the low and high strain amplitudes, respectively. This was attributed to the formation of fine grains relieving the stress concentration during cyclic loading. In addition, residual twins were observed in equiaxed structure to induce crack, and the bimodal structure effectively restrain it.

Microstructure and mechanical properties of Fe/NbC composite layer prepared by in-situ reaction

NbC ceramic surface-reinforced steel matrix composites were prepared by an in-situ reaction method at different temperatures(1,050℃,1,100℃and 1,150℃)for different times(1 h,2 h and 3 h).The phase constitution,microstructure and fracture morphology of NbC ceramic surface-reinforced steel matrix composites were analyzed by XRD,SEM and EDS,and the effects of the in-situ reaction temperature and time on the mechanical properties were systematically studied.The results indicate that the NbC reinforcement layer is formed through the reaction between Nb atoms and carbon atoms diffused from the steel matrix to the Nb plate.The thickness of this reinforcement layer increases as the reaction time prolongs.Additionally,an increase in reaction temperature results in a thicker reinforcement layer,although the rate of increase gradually decreases.The relationship among the thickness of the Nb C reinforcement layer,the reaction time and temperature was established by data fitting.The optimal tensile performance is achieved at 1,100℃for 1 h,with a tensile strength of 228 MPa.It is also found that the defects between the reinforcement layer and the steel matrix are related to reaction temperature.At 1,100℃,these defects are minimal.Fracture mostly occurs in the NbC reinforced layer of the composites,and the fracture mode is characterized by typical intergranular brittle fracture.

An OP-TEE Energy-Efficient Task Scheduling Approach Based on Mobile Application Characteristics

Trusted Execution Environment(TEE)is an important part of the security architecture of modern mobile devices,but its secure interaction process brings extra computing burden to mobile devices.This paper takes open portable trusted execution environment(OP-TEE)as the research object and deploys it to Raspberry Pi 3B,designs and implements a benchmark for OP-TEE,and analyzes its program characteristics.Furthermore,the application execution time,energy consumption and energy-delay product(EDP)are taken as the optimization objectives,and the central processing unit(CPU)frequency scheduling strategy of mobile devices is dynamically adjusted according to the characteristics of different applications through the combined model.The experimental result shows that compared with the default strategy,the scheduling method proposed in this paper saves 21.18%on average with the Line Regression-Decision Tree scheduling model with the shortest delay as the optimization objective.The Decision Tree-Support Vector Regression(SVR)scheduling model,which takes the lowest energy consumption as the optimization goal,saves 22%energy on average.The Decision Tree-K-Nearest Neighbor(KNN)scheduling model with the lowest EDP as the optimization objective optimizes about 33.9%on average.

Analysis and Identification of miRNA Expression in the Skeletal Muscle of Sichuan White Rabbits

[Objectives]miRNAs play an important role in the proliferation and differentiation of different myoblasts.This study was conducted to elucidate the complex genetic mechanisms that affect the meat production performance of Sichuan white rabbits and reveal the regulatory role of miRNAs in their muscle growth and meat quality formation.[Methods]Three constructed skeletal muscle libraries of Sichuan white rabbits aged six months were sequenced by the solexa technology to identify known miRNAs,predict new miRNAs and construct an expression profile of muscle miRNAs.[Results]A total of 511 known miRNAs and 42 miRNAs were detected in 34089472 pure sequences,and the proportion of miRNAs with a length of 22 nt was the highest.The number of known miRNA sequences accounted for 71.38%of pure sequences,which was much higher than the proportion of other types of RNAs.The proportion of sequences from exons was 0.38%,indicating a low degree of mRNA degradation in the samples.Base U had the highest proportion at the first position,and the bases with the highest proportions at positions 8 and 10 were U and A,respectively.Muscle-specific miRNAs(miR-1,miR-133,and miR-206)ranked in the top 10 in terms of expression level.The number and expression levels of new miRNAs were lower than those of known miRNAs.The length distribution,base bias at different positions and expression profile characteristics of miRNAs might be related to the biological function of miRNAs in regulating muscle proliferation and differentiation and the action mechanisms with target genes.[Conclusions]The identification and expression of miRNAs in muscle tissues of Sichuan white rabbits will help to understand the complex molecular mechanisms of meat production performance and provide a theoretical basis for the functional research of miRNAs in meat rabbits.

角膜塑形镜控制儿童近视发展的影响因素

随着儿童近视发病率的不断增高,近视防控已引起人们越来越多的重视。角膜塑形术作为一种非手术性的矫正近视以及控制近视进展的治疗方式已经在全球范围内广泛应用。大量临床研究表明角膜塑形术是目前最有效地控制近视进展的重要手段之一。但是,并不是所有配戴角膜塑形镜的儿童均能获得理想的近视控制疗效,诸多因素可以影响角膜塑形镜对儿童近视发展的控制效果。现就角膜塑形镜控制儿童近视的影响因素进行综述。

Characterization of Silver Nanoparticles Thin Films with Various Thicknesses by AFM

Ag nanoparticles (NPs) thin films with various thicknesses were prepared by thermal evaporation method. Atomic force microscopy (AFM) and UV-Vis spectrophotometer were used to study the surface morphology, growth nature and optical properties of the films. The results indicate that the growth rates of Ag particles in lateral and vertical direction are variable, and the dominant growth rate of Ag particles in lateral direction will convert into dominant growth rate in vertical direction as films grow thicker. The mean value and distribution of Ag NPs height related with the location and width of SPR (surface plasmonresonance) peak. Higher mean height shifts SPR peak to longer wavelengths, and smaller deviation results in narrower width of SPR peaks.