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.

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.

二氧化碳的捕获和转化——第54届国际化学奥林匹克试题第3题解析

二氧化碳是引起温室效应的“罪魁祸首”,其吸收和转化一直是科学研究的热点之一。第54届国际化学奥林匹克试题第3题围绕CO_(2)的处理,从NaOH碱液吸收CO_(2)出发,结合H2辅助的电化学循环实现吸收剂重生和高纯CO_(2)回收、新型类沸石咪唑骨架多孔材料的结构和催化CO_(2)转化,讲述了一个从经典到前沿、从普通的溶液体系到新型固体材料应用而解决科学问题的故事。藉此,引导年轻的学子关注气候变化,了解基础化学原理在解决环境问题中的重要作用,鼓励学生打好学科基础,投身探索和发展新方法和创制新材料的研究之中。

幼儿园环境对教师学习投入的影响：基本心理需求的中介作用

学习投入是教师为提升专业素养、改进工作效能,参与基于幼儿园日常教学与科研等方面的学习活动时,所综合表现出来的学习行为卷入程度、情绪情感体验质量及认知策略运用水平。为探究教师学习投入、幼儿园环境和基本心理需求之间的关系,采用幼儿园教师学习投入量表、幼儿园环境量表和基本心理需求量表,对1037名幼儿园教师进行问卷调查,结果表明幼儿园教师学习投入总体状况较好,学习投入各维度水平之间以及不同职务、荣誉的幼儿园教师学习投入水平之间差异显著;学习投入、幼儿园环境、基本心理需求之间呈显著正相关;幼儿园环境显著正向预测教师学习投入,并通过基本心理需求的中介作用影响教师学习投入。幼儿园应创设良好的园所环境,并重点关注3年以下教龄、非骨干、配班等教师群体,以满足教师的基本心理需求,提升其学习投入水平,同时教师自身应加大学习行为投入,重视基本心理需求特别是自主感的提升,在日常工作中积极开展自我导向学习,主动参加园内各项活动与事务,为幼儿园发展建言献策。

Effects of dietary Clostridium butyricum supplementation on growth performance,intestinal development,and immune response of weaned piglets challenged with lipopolysaccharide

Background: Weanling pigs, with immature immune system and physiological function, usually experience postweaning diarrhea. This study determined the effects of dietary Clostridium butyricum supplementation on growth performance, diarrhea, and immunity of weaned pigs challenged with lipopolysaccharide(LPS).Methods: In Experiment(Exp.) 1,144 weaned piglets were weaned at 21 d and randomly assigned to six groups,with six replicates per group and four pigs per replicate, receiving a control diet(CON) or diet supplemented with antibiotics(AB) or C. butyricum(CB)(0.1%, 0.2%, 0.4%, or 0.8%), respectively. All diets in Exp. 1 were a highly digestible basal diet, with 3,000 mg/kg zinc oxide supplied in the first 2 wk only. In Exp. 2, 180 piglets were weaned at 21 d and randomly assigned to five groups, with six replicates per group and six pigs per replicate, receiving CON, AB, or CB(0.2%, 0.4%, or 0.6%) diets. The digestibility of diets was lower than those in Exp. 1, and did not include zinc oxide. At 36 d of Exp. 2, 12 piglets were selected from each of the CON and 0.4% CB groups, six piglets were intraperitoneally injected with LPS(50 μg/kg body weight) and the other six piglets with normal saline;animals were killed at 4 h after injection to collect blood, intestine, and digesta samples for biochemical analysis.Results: In Exp. 1, CB and AB diets had no effect on growth performance of piglets. In Exp. 2, 0.4% CB decreased feed-gain ratio(P < 0.1), diarrhea score(P < 0.05), and increased duodenal, jejunal, and ileal villus height and jejunal villus height/crypt depth(P < 0.05). The 0.4% CB decreased the plasma tumor necrosis factor(TNF) α(P < 0.05) but increased ileal mucosa IL-10 and TLR2 mRNA expression(P < 0.05). Furthermore, 0.4% CB altered the microbial profile, with Bacillus and Ruminococcaceae UGG-003 at genus level and Lactobacillus casei and Parasutterella secunda at species level were higher than CON in colonic content(P < 0.05).Conclusions: Dietary C. butyricum supplementation had positive effects on growth of weaned piglets with less digestible diets. There was a tendency to reduce the feed-gain ratio, which could reduce feed costs in pig production. Moreover, C. butyricum decreased post-weaning diarrhea by improving the intestinal morphology,intestinal microflora profile, and immune function.

Hepatitis B virus X protein promotes liver cell proliferation via a positive cascade loop involving arachidonic acid metabolism and p-ERK1/2

Hepatitis B virus X protein （HBx） plays a crucial role in the development of hepatocellular carcinoma. Here, we sought to identify the mechanisms by which HBx mediates liver cell proliferation. We found that HBx upregulated the levels of cyclooxygenase-2 （COX-2）, 5-1ipoxygenase （5-LOX） and phosphorylated extracellular signal-regulated protein kinases 1/2 （p-ERK1/2） in liver cells. HBx-induced p-ERK1/2 was abolished by inhibition of Gi/o proteins, COX or LOX. In addition, HBx increased the amounts of prostaglandin E2 （PGE2） and leukotriene B4 （LTB4） released from cell lines derived from hepatocytes. Moreover, these released arachidonic acid metabolites were able to activate ERK1/2. Interestingly, activated ERK1/2 could upregulate the expression of COX-2 and 5-LOX in a positive feedback manner. In conclusion, HBx enhances and maintains liver cell proliferation via a positive feedback loop involving COX-2, 5-LOX, released arachidonic acid metabolites, Gi/o proteins and p-ERK1/2.

Perspectives and challenges of hydrogen storage in solid-state hydrides

Hydrogen has been widely considered as a clean energy carrier that bridges the energy producers and energy consumers in an efficient and safe way for a sustainable society.Hydrogen can be stored in a gas,liquid and solid states and each method has its unique advantage.Though compressed hydrogen and liquefied hydrogen are mature technologies for industrial applications,appropriate measures are necessary to deal with the issues at high pressure up to around 100 MPa and low temperature at around 20 K.Distinct from those technologies,storing hydrogen in solid-state hydrides can realize a more compact and much safer approach that does not require high hydrogen pressure and cryogenic temperature.In this review,we will provide an overview of the majormaterial groups that are capable of absorbing and desorbing hydrogen reversibly.The main features on hydrogen storage properties of each material group are summarized,together with the discussion of the key issues and the guidance of materials design,aiming at providing insights for new material development as well as industrial applications.

Relaxant Effects of Matrine on Aortic Smooth Muscles of Guinea Pigs

Objective To determine whether matrine, a kind of traditional Chinese medicinal alkaloid, can relax the aortic smooth muscles isolated from guinea pigs and to investigate the mechanism of its relaxant effects. Methods Phenylephrine or potassium chloride concentration-dependent relaxation response of aortic smooth muscles to matrine was studied in the precontracted guinea pigs. Results Matrine （1×10^-4 mol/L -3.3×10^-3 mol/L） relaxed the endothelium-denuded aortic rings pre-contracted sub-maximally with phenylephrine, in a concentration-dependent manner, and its pre-incubation （3.3× 10^- 3 mol/L） produced a significant rightward shift in the phenylephrine dose-response curve, but had no effects on the potassium chloride-induced contraction. The anti-contractile effect of matrine was not reduced by the highly selective ATP-dependent K^＋ channel blocker glibenclamide （10.5 mol/L）, either by the non-selective K^＋channel blocker tetraethylammonium （10^-3 mol/L）, or by the β-antagonist propranolol （10^-5 mol/L）. In either ＂normal＂ or ＂Ca^2＋-free＂ bathing medium, the phenylephrine-induced contraction was attenuated by matrine （3.3×10^-3 mol/L）, indicating that the vasorelaxation was due to inhibition of intracellular and extracellular Ca^2＋ mobilization. Conclusion Matrine inhibits phenylephrine-induced contractions by inhibiting activation of α-adrenoceptor and interfering with the release of intracellular Ca^2＋ and the influx of extracellular Ca^2＋.

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.

Microstructure and mechanical properties of AZ31 alloy prepared by cyclic expansion extrusion with asymmetrical extrusion cavity

The microstructure,texture evolution and mechanical properties of AZ31 magnesium alloy were investigated during the cyclic expansion extrusion with the asymmetrical extrusion cavity(CEE-AEC)process.The results show that continuous dynamic recrystallization(CDRX)and discontinuous dynamic recrystallization(DDRX)occur during the CEE-AEC process.After 3 passes,the microstructures of the deformed samples are refined,and the average grain size of the alloys in asymmetrical cavity region is 6.9μm.The maximum intensities of the basal textures increase with the increase in the number of passes,and the basal textures are deflected during the deformation process.The basal texture of the alloys in asymmetrical cavity region is tilted by approximately±45°from the normal direction(ND)to the extrusion direction(ED).Grain refinement strengthening and texture deflection significantly improve the comprehensive mechanical properties of the deformed alloys.After 3 passes,tensile yield strength(TYS),ultimate tensile strength(UTS)and elongation-to-failure of the alloy in the asymmetric cavity region are 146 MPa,230 MPa and 29.7%,respectively.

Bimetallic Ru-Ni/TiO2 catalysts for hydrogenation of N-ethylcarbazole:Role of TiO2 crystal structure

Hydrogenation of N-ethylcarbazole(NEC),the hydrogen lean form of a liquid organic hydrogen carrier,on TiO2 supported Ru-Ni bimetallic catalysts is investigated.Crystal structure of TiO2 plays a critical role on the hydrogenation activity and selectivity towards fully hydrogenated product.Ru/anatase catalyst exhibits higher selectivity but lower reactivity compared to Ru/rutile catalyst.Ni addition significantly promotes the performance of Ru/anatase catalyst while causes severe performance deterioration of Ru/rutile catalyst.Commercial P25,a mixture of anatase and rutile phases in approximate ratio A/R1/4,is found to be the best TiO2 support for NEC hydrogenation.Ru/P25 catalyst outperforms both Ru/rutile and Ru/anatase and its activity can be further slightly improved by Ni addition.The unexpected synergism between the two different TiO2 phases for Ru based NEC hydrogenation catalysts is related to metal-support interaction and Ru-Ni interaction.