TiAl合金低周疲劳失效机理综述

TiAl合金具有优异的比强度和高温稳定性,被广泛应用于航空航天领域。随着社会发展对飞机发动机运行稳定性和可靠性的要求越来越高,TiAl合金的低周疲劳性能和失效机理越来越受到关注。本文综述了近30年来TiAl合金低周疲劳方面的研究进展,包括应变范围、温度、合金成分、组织类型、片层取向、微观变形等对TiAl合金低周疲劳行为的影响机理,重点阐释了测试条件与TiAl合金微观结构的交互作用对疲劳失效行为的影响规律。

Hypoxia-preconditioned bone marrow-derived mesenchymal stem cells protect neurons from cardiac arrest-induced pyroptosis

Cardiac arrest can lead to severe neurological impairment as a result of inflammation,mitochondrial dysfunction,and post-cardiopulmonary resuscitation neurological damage.Hypoxic preconditioning has been shown to improve migration and survival of bone marrow–derived mesenchymal stem cells and reduce pyroptosis after cardiac arrest,but the specific mechanisms by which hypoxia-preconditioned bone marrow–derived mesenchymal stem cells protect against brain injury after cardiac arrest are unknown.To this end,we established an in vitro co-culture model of bone marrow–derived mesenchymal stem cells and oxygen–glucose deprived primary neurons and found that hypoxic preconditioning enhanced the protective effect of bone marrow stromal stem cells against neuronal pyroptosis,possibly through inhibition of the MAPK and nuclear factor κB pathways.Subsequently,we transplanted hypoxia-preconditioned bone marrow–derived mesenchymal stem cells into the lateral ventricle after the return of spontaneous circulation in an 8-minute cardiac arrest rat model induced by asphyxia.The results showed that hypoxia-preconditioned bone marrow–derived mesenchymal stem cells significantly reduced cardiac arrest–induced neuronal pyroptosis,oxidative stress,and mitochondrial damage,whereas knockdown of the liver isoform of phosphofructokinase in bone marrow–derived mesenchymal stem cells inhibited these effects.To conclude,hypoxia-preconditioned bone marrow–derived mesenchymal stem cells offer a promising therapeutic approach for neuronal injury following cardiac arrest,and their beneficial effects are potentially associated with increased expression of the liver isoform of phosphofructokinase following hypoxic preconditioning.

An integrated north–south paleo-Dadu-Anning River: New insights from bulk major and trace element analyses of the Xigeda Formation

The Xianshuihe-Anninghe fault extends SE–S and constitutes the southeastern margin of the Tibetan Plateau.However,the Dadu River which is associated with the fault does not flow following the path,but makes a 90ºturn within a distance of 1 km at Shimian,heading east,and joins the Yangtze River,finally flowing into the East China Sea.Adjacent to the abrupt turn,a low and wide pass near the Daqiao reservoir at Mianning separates the N–S course of the Dadu River from the headwater of the Anning River which then flows south into the Yunnan Province along the Anninghe fault.Therefore,many previous studies assumed southward flow of the paleo-Dadu River from the Shimian to the Anning River.However,evidences for the capture of the integrated N–S paleo-Dadu-Anning River,its timing,and causes are still insufficient.This study explored the paleo-drainage pattern of the Dadu and Anning Rivers based on bulk mineral and geochemical analyses of the large quantities of fluvial/lacustrine sediments along the trunk of the Dadu and Anning Rivers.Similar with sands in the modern Dadu River,the Xigeda sediments also exhibit a granitoid affinity with the bulk major mineral compositions of quartz(>50%),anorthite(about 10%),orthoclase(about 5%),muscovite(about 5%),and clinochlore(about 4%).Correspondingly,bulk major elements show high SiO_(2),with all samples>60%,and some of them>70%,low TiO_(2)(≤0.75%),P_(2)O_(5)(≤0.55%),FeO*(≤5%),and relatively high CaO(1.02%–8.51%),Na_(2)O(1.60%–2.52%),and K_(2)O(2.17%–2.71%),with a uniform REE patterns.Therefore,synthesizing all these results indicate that these lacustrine sediments have similar material sources,which are mainly derived from its course in the Songpan-Ganzi flysch block,implying that the paleo-Dadu originally flowed southward into the Anning River and provided materials to the Xigeda ancient lake.The rearrangement of the paleo-Dadu River appears to be closely related to the locally focused uplift driven by strong activities of the XianshuiheXiaojiang fault system.

B-cell-specific signatures reveal novel immunophenotyping and therapeutic targets for hepatocellular carcinoma

BACKGROUND Immunotherapy presents both promises and challenges in treating hepatocellular carcinoma(HCC)due to its complex immunological microenvironment.The role of B cells,a key part of the immune system,remains uncertain in HCC.AIM To identify B-cell-specific signatures and reveal novel immunophenotyping and therapeutic targets for HCC.METHODS Using the Tumor Immune Single-cell Hub 2 database,we identified B-cell-related genes(BRGs)in HCC.Gene enrichment analysis was performed to explore the possible collaboration between B cells and T cells in HCC.We conducted univariate Cox regression analysis using The Cancer Genome Atlas liver HCC collection dataset to find BRGs linked to HCC prognosis.Subsequently,least absolute shrinkage and selection operator regression was utilized to develop a prognostic model with 11 BRGs.The model was validated using the International Cancer Genome Consortium dataset and GSE76427.RESULTS The risk score derived from the prognostic model emerged as an independent prognostic factor for HCC.Analysis of the immune microenvironment and cell infiltration revealed the immune status of various risk groups,supporting the cooperation of B and T cells in suppressing HCC.The BRGs model identified new molecular subtypes of HCC,each with distinct immune characteristics.Drug sensitivity analysis identified targeted drugs effective for each HCC subtype,enabling precision therapy and guiding clinical decisions.CONCLUSION We clarified the role of B cells in HCC and propose that the BRGs model offers promising targets for personalized immunotherapy.

Three-dimensional general magneto-electro-elastic finite element model for multiphysics nonlinear analysis of layered composites

In this paper,by defining a general potential energy for the multiphase coupled multiferroics and applying the minimum energy principle,the coupled governing equations are derived.This system of equations is then discretized as a general three-dimensional(3D)finite element(FE)model based on the COMSOL software.After validating the formulation,it is then applied to the analysis and design of the common sandwich structure of multiferroics composites.Under the typical static loading,the effects of general lateral boundary conditions,material grading,nonlinearity,as well as polarization orientation on the composites are analyzed.For the magneto-electro-elastic(MEE)sandwich made of piezoelectric BaTiO_(3)and magnetostrictive CoFe_(2)O_(4)with different stacking sequences,various interesting features are observed which should be very helpful for the design of high-performance multiphase composites.

Spin-polarized electron beam generation in the colliding-pulse injection scheme

Employing colliding-pulse injection has been shown to enable the generation of high-quality electron beams from laser-plasma accelerators.Here,by using test particle simulations,Hamiltonian analysis,and multidimensional particle-in-cell simulations,we lay the theoretical framework for spin-polarized electron beam generation in the colliding-pulse injection scheme.Furthermore,we show that this scheme enables the production of quasi-monoenergetic electron beams in excess of 80%polarization and tens of pC charge with commercial 10-TW-class laser systems.

2022美术:共情与共创

本文将从三方面讨论2022年中国美术的年度问题。第一,多方参与共同建构话语平台,以不同城市举办的国际美术双年展为例,讨论大众与精英的话语消长;第二,主题性美术创作中的新时代精神,以第7届全国青年美术作品展览和第15届全军美术作品展览为例,讨论主题与时代的联动关系;第三,艺术与科技深度融合的学科定位,以教育部新增本科专业名录及各地实施情况为例,讨论系统设置中的序列与依存。所论三者,无一不处于变动之中,并让我们看到动之根本,在于场域的境况。2022年中国美术正处在当代转型的关键时期,优化生态系统,共情共创,是一种解决的方式,而到后疫情时代,也许还会再次面临个体性问题的挑战。

2020美术:自觉的主体

2020年的中国美术,其最突出的特征就是主体互动,以此呈现其自觉性。这与抗击新冠肺炎疫情有关,与主题性创作有关,与全球化时代文化主体相互依存的关系有关。本文从"主题、主体与整体性"切入,讨论艺术抗疫中的主体多元,以及传统与当代文化中的主体建构,再及公共空间中的大众审美问题。在2020年复杂的中国美术现象中,本文力图抓住典型案例,针对热点问题展开分析,既反映上半年艺术抗疫的整体情况,又通过下半年大量出现的双年展现象,看到文化主体性在创作中的活跃程度,关注在脱贫攻坚决胜之年艺术介入美丽乡村建设的主体性作用,最后提出当代美术学学科发展应注意的问题。

Protective effects of curcumin against human immunodeficiency virus 1 gp120 V3 loop-induced neuronal injury in rats

Curcumin improves the learning and memory deficits in rats induced by the gp120 V3 loop. The present study cultured rat hippocampal neurons with 1 nM gp120 V3 loop and 1 μM curcumin for 24 hours. The results showed that curcumin inhibited the gp120 V3 loop-induced mitochondrial membrane potential decrease, reduced the mRNA expression of the pro-apoptotic gene caspase-3, and attenuated hippocampal neuronal injury.

An online coronavirus analysis platform from the National Genomics Data Center

DEAR EDITOR,Since the first reported severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)infection in December 2019,coronavirus disease 2019(COVID-19)has become a global pandemic,spreading to more than 200 countries and regions worldwide.With continued research progress and virus detection,SARS-CoV-2 genomes and sequencing data have been reported and accumulated at an unprecedented rate.

Curcumin ameliorates hippocampal neuron damage induced by human immunodeficiency virus-1

Our previous studies have shown that infection with the gp120 V3 loop can cause human immunodeficiency virus-1 associated neurocognitive disorders. Curcumin has been shown to improve these effects to some degree, but the precise mechanisms remain unknown. The present study analyzed the neuroprotective effect and mechanism of curcumin in relation to hippocampal neurons. Results showed that 1 nmol/L gp120 V3 loop suppressed the growth of synapses. After administration of 1 !umol/L curcumin, synaptic growth improved. Curcumin is neuroprotective against gp120 V3 loop-induced neuronal damage by inhibiting the activation of L-type calcium currents, relieving intracellular Ca^2＋ overload, promoting Bcl-2 expression, and inhibiting Bax activation. The effect of curcumin was identical to nimodipine, suggesting that curcumin has the same neuroprotective effects against gp120 V3 loop-induced neuronal damage.

Processes,feedbacks,and morphodynamic evolution of tidal flat-marsh systems:Progress and challenges

Tidal flats and saltmarshes have been a long-standing research focus because of their high socio-economic and ecological values.The evolution of tidal flat-marsh systems is highly complex due to the intertwined processes operating over a variety of spatial and temporal scales.As a traditional research highlight,the role of regular hydrodynamic processes such as tides,waves,and river flows have been explored comprehensively with fruitful outcomes.Over past decades,the changing environment(e.g.,sea level rise,increasing anthropogenic activities,and extreme weather conditions)has attracted more attention with many reported insightful results.More recent advances indicate that biological activities play a critical role in tidal flat-marsh morphodynamics but are still poorly understood.The field of research that connects the bio-logical and physical processes is commonly described as"biogeomorphology"and requires the joint efforts by scientists from multiple dis-ciplines ranging from hydraulics,ecology,and geography to sociology.This review aims to provide a synthesis of the current research status of tidal flat-marsh morphodynamics,with a particular emphasis on the understanding of various processes and feedbacks underlying the devel-opment of morphodynamic models.Some future research needs and challenges are identified to facilitate a more sustainable management strategy for tidal flats and saltmarshes under climate change.

Study on the emission characteristics of nitrogen oxides with coal combustion in pressurized fluidized bed

Nitrogen oxides are one of the most significant pollution sources during coal combustion. This experimental study was conducted in a 15 kWth lab-scale pressurized fluidized bed (inner diameter = 81-100 mm, H = 2100 mm) firing with bituminous coals. The effects of operating parameters, including bed temperature (800℃-900℃), operating pressure (0.1-0.4 MPa), excess air level (16%-30%) and flow pattern on NOX and N2O emissions were systematically studied during the tests. During each test the interaction effects of all the operating parameters were properly controlled. The results show that most operating parameters have an opposite effect on NOX and N2O emissions, and the N2O emissions mainly depend on the bed temperature. Increasing the operating pressure can significantly suppress the fuel-N conversion to NOX but enhance its conversion to N2O. With the rise of the excess air level and fluidization number, NOX emissions grow distinctly while N2O emissions remain almost unchanged. Total nitrogen oxide emissions increase with the bed temperature while decrease with the operating pressure.

人与物之间:中国书籍设计现代性问题

当前的中国书籍设计不断借鉴传统文化元素以求塑造民族性的现代性品质,书籍设计的材质与人对书籍的感性问题不断被重视,但书籍的物质性与设计现代性关联仍不清晰。设计其实处于人与物之间,为人与物的间性存在。当前中国书籍设计不断探索和生成自然化与场域化的间性设计。一种中国式的流动的现代性,对于解决世界现代性分化危机、重新开启人与自然关系,以及探究设计的现代性问题有着积极意义。

Recent developments in seismological geodesy

With the advanced development of the modern geodetic techniques, the geodetic obser- vations have been proved to be more powerful to uncover the geophysical phenomena, especially the seismic one, than that in the past time. The recent developments and achievements in the seismological geodesy are summarised here. Several popular geodetic techniques, such as high-rate GNSS, InSAR and Satellite Gravimetry, are introduced first to present their recent contributions in studying the seismic deformations. The developments of the joint inversion of the seismic source parameters from multiple observations are then highlighted. Some outlooks in seismological geodesy are presented in the end.

熔模精密铸造技术研究进展

熔模精密铸造是一种原料利用率高的近净成形技术,适合难加工类零件和复杂薄壁件的精密成形,是航空航天、先进制造等领域高附加值精密部件的重要生产技术。以高温合金、钛合金和钛铝金属间化合物为例,概述了熔模精密铸造技术在航空发动机叶片领域的应用,综述了型壳材料与型芯成形等技术的发展历史与研究现状。主要围绕耐火材料介绍了高温合金、钛合金等金属精密铸造型壳技术的特性与优缺点,重点介绍了氧化物陶瓷型壳的发展情况,最后结合金属-陶瓷界面反应和铸件氧含量控制这两个突出问题,评述了熔模精密铸造技术目前存在的难题与发展前景。

Sediment transport following water transfer from Yangtze River to Taihu Basin

To meet the increasing ：need of fresh water and to improve the water quality of Taihu Lake, water transfer from the Yangtze River was initiated in 2002. This study was performed to investigate the sediment distribution along the river course following water transfer. A rainfall-runoff model was first built to calculate the runoff of the Taihu Basin in 2003. Then, the flow patterns of river networks were simulated using a one-dimensional river network hydrodynamic model. Based on the boundary conditions of the flow in tributaries of the Wangyu River and the water level in Taihu Lake, a one-dimensional hydrodynamic and sediment transport numerical model of the Wangyu River was built to analyze the influences of the inflow rate of the water transfer and the suspended sediment concentration （SSC） of inflow on the sediment transport. The results show that the water transfer inflow rate and SSC of inflow have significant effects on the sediment distribution. The higher the inflow rate or SSC of inflow is, the higher the SSC value is at certain cross-sections along the ：river course of water transfer. Higher inflow rate and SSC of inflow contribute to higher sediment deposition per kilometer and sediment thickness. It is also concluded that a sharp decrease of the inflow velocity at the entrance of the Wangyu River on the river course of water transfer induces intense sedimentation at the cross-section near the Changshu hydro-junction. With an increasing distance from the Changshu hydro-junction, the sediment deposition and sedimentation thickness decrease gradually along the river course.

Bradykinin postconditioning protects rat hippocampal neurons after restoration of spontaneous circulation following cardiac arrest via activation of the AMPK/mTOR signaling pathway

Bradykinin(BK)is an active component of the kallikrein-kinin system that has been shown to have cardioprotective and neuroprotective effects.We previously showed that BK postconditioning strongly protects rat hippocampal neurons upon restoration of spontaneous circulation(ROSC)after cardiac arrest.However,the precise mechanism underlying this process remains poorly understood.In this study,we treated a rat model of ROSC after cardiac arrest(induced by asphyxiation)with 150μg/kg BK via intraperitoneal injection 48 hours after ROSC following cardiac arrest.We found that BK postconditioning effectively promoted the recovery of rat neurological function after ROSC following cardiac arrest,increased the amount of autophagosomes in the hippocampal tissue,inhibited neuronal cell apoptosis,up-regulated the expression of autophagy-related proteins LC3 and NBR1 and down-regulated p62,inhibited the expression of the brain injury marker S100βand apoptosis-related protein caspase-3,and affected the expression of adenosine monophosphate-activated protein kinase/mechanistic target of rapamycin pathway-related proteins.Adenosine monophosphate-activated protein kinase inhibitor compound C clearly inhibited BK-mediated activation of autophagy in rats after ROSC following cardiac arrest,which aggravated the injury caused by ROSC.The mechanistic target of rapamycin inhibitor rapamycin enhanced the protective effects of BK by stimulating autophagy.Our findings suggest that BK postconditioning protects against injury caused by ROSC through activating the adenosine monophosphate-activated protein kinase/mechanistic target of the rapamycin pathway.

Ecological impact of land reclamation on Jiangsu coast(China):A novel ecotope assessment for Tongzhou Bay

China’s continuous and rapid economic growth has led to the reclamation of large sections of the intertidal mud coast in combination with port construction,such as that of the proposed Tongzhou Bay port on the Jiangsu coast.These reclamations threaten the local ecosystem services.An ecotope distribution map was created and a hydrodynamic numerical model of Tongzhou Bay was set up to quantify the impacts of reclamation on the ecosystem.Based on the field data and model results,several abiotic features were classified into 11 ecotopes and visualized in an ecotope map of the Tongzhou Bay ecosystem.Validation with spatial distributions of two threatened shorebird species(bar-tailed godwit and great knot) showed confirmation with the mid-range and low-range littoral zones(inundated from 40% to 100% of a tidal cycle),indicating the importance of the areas with these conditions to these populations.Overlaying the ecotope map with recent and proposed land reclamation schemes revealed a loss of ecotopes,composed of the high-range(42%),mid-range(48%),and low-range(38%) littoral habitats,corresponding to a 44%-45% loss of the most important ecotopes for bar-tailed godwit and great knot(mid-range and low-range littoral zones).These results confirm the applicability of the novel ecotope assessment approach in practice.

Radiation reaction induced spiral attractors in ultra-intense colliding laser beams

The radiation reaction effects on electron dynamics in counter-propagating circularly polarized laser beams are investigated through the linearization theorem and the results are in great agreement with numeric solutions.For the first time,the properties of fixed points in electron phase-space were analyzed with linear stability theory,showing that center nodes will become attractors if the classical radiation reaction is considered.Electron dynamics are significantly affected by the properties of the fixed points and the electron phase-space densities are found to be increasing exponentially near the attractors.The density growth rates are derived theoretically and further verified by particle-in-cell sim-ulations,which can be detected in experiments to explore the effects of radiation reaction qualitatively.The attractor can also facilitate realizing a series of nanometer-scaled flying electron slices via adjusting the colliding laser frequencies.