Inversion of O_(2) 1.27 μm nightglow emissions: A climatological analysis using satellite Limb-Viewed spectra and Harmonic analysis method

This study employs a linear inversion algorithm to retrieve volume emission rates(VERs)of molecular O_(2) nightglow at 1.27μm,utilizing Limb-Viewed spectra obtained from the SCanning Imaging Absorption spectroMeter for Atmospheric for CHartographY(SCIAMACHY)payload on board the Envisat satellite.The retrieved results are compared with VERs data from the SABER payload on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics(TIMED)satellite,exhibiting consistency.This will help to facilitate accurate revelation of spatial distribution and periodic variation in O_(2) nightglow.VERs are extracted monthly within the altitude range of 75-110 km from 2002 to 2012,yielding a climatology of spatial and temporal distributions.The meridional structure exhibits two maxima,at the equator and at 45°N.Between August and October,the VERs exhibit a meridional bimodal structure,with the weaker one above the equator and the stronger one above 45°N.In April,the VERs reach their annual maximum.Additionally,harmonic analysis reveals significant temporal variations on different scales.The emission shows characteristics of annual and semi-annual variation,and a non-linear long-term trend associated with solar cycle activity.

Co-MOF作为电子供体用于提高g-C3N4纳米片的可见光催化还原CO2性能（英文）

作为温室效应的主要气体CO2浓度持续上升,已经成为全球环境问题.将CO2光催化还原成可再生能源不仅可以解决CO2带来的温室效应,而且可以将太阳能转化为燃料物质而取代传统意义上的化石能源.实际上光催化的研究可以追溯到1979年,自从Inoue首次报道了光催化CO2和水制取甲酸、甲烷等有机物,人们一直在努力开发高效的CO2转化光催化剂.近年来,随着光催化技术的快速稳定发展,各种半导体光催化剂,如Zn2Ge O4,CdS,Fe3O4,g-C3N4和SrTiO3等,已被开发用于光催化还原二氧化碳.在这些半导体中,有的材料具有较大的带隙导致较低的可见光活性,有的材料具有毒性引起额外的环境问题.因此,寻求具有适度带隙且环境友好的半导体材料是解决全球变暖问题的关键.近年来,g-C3N4因其带隙(约2.7e V)较窄,具有一定的可见光吸收性能,无污染,以及化学和热稳定性良好等特点,被视为理想的可见光响应光催化材料之一.但是,g-C3N4光吸收有限、光生电子空穴复合率较高等缺点严重限制了其光催化活性.为了进一步提高g-C3N4的CO2可见光催化还原活性,国内外研究者开发了许多方法来提高电荷分离效率,进而提高g-C3N4光催化剂的总体活性.在这些策略中,将g-C3N4与具有合适导带位置的其他材料偶联以促进电子空穴分离是提高光催化性能的有效方法之一.由于Co-MOF具有较窄的带隙且导带位置与g-C3N4匹配,我们选择Co-MOF与g-C3N4复合来克服g-C3N4的缺点,进而达到提高其光催化活性的目的.作为电子供体的Co-MOF能够将最低未占分子轨道(LUMO)上的光生电子转移到g-C3N4的导带以促进电荷分离,同时水被g-C3N4价带上的空穴氧化,最终生成氧气,从而提高光催化还原CO2的性能.制备的Co-MOF/g-C3N4纳米复合材料在可见光照射下具有优异的光催化还原CO2性能,约为纯g-C3N4的光催化活性的2倍.一系列分析表明,Co-MOF的引入不仅拓宽了可见光的吸收范围,而且促进了电荷分离,有利于提高g-C3N4的光催化活性.特别是在590nm单波长照射下进行的羟基自由基实验进一步证明了Co-MOF的LUMO上的光生电子可以转移到g-C3N4.该研究结果为基于g-C3N4的光催化体系的合理构建提供了新思路.

Honokiol alleviated neurodegeneration by reducing oxidative stress and improving mitochondrial function in mutant SOD1 cellular and mouse models of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis(ALS)is a progressive neurodegenerative disease affecting both upper and lower motor neurons(MNs)with large unmet medical needs.Multiple pathological mechanisms are considered to contribute to the progression of ALS,including neuronal oxidative stress and mitochondrial dysfunction.Honokiol(HNK)has been reported to exert therapeutic effects in several neurologic disease models including ischemia stroke,Alzheimer’s disease and Parkinson’s disease.Here we found that honokiol also exhibited protective effects in ALS disease models both in vitro and in vivo.Honokiol improved the viability of NSC-34 motor neuron-like cells that expressed the mutant G93A SOD1 proteins(SOD1-G93A cells for short).Mechanistical studies revealed that honokiol alleviated cellular oxidative stress by enhancing glutathione(GSH)synthesis and activating the nuclear factor erythroid 2-related factor 2(NRF2)-antioxidant response element(ARE)pathway.Also,honokiol improved both mitochondrial function and morphology via fine-tuning mitochondrial dynamics in SOD1-G93A cells.Importantly,honokiol extended the lifespan of the SOD1-G93A transgenic mice and improved the motor function.The improvement of antioxidant capacity and mitochondrial function was further confirmed in the spinal cord and gastrocnemius muscle in mice.Overall,honokiol showed promising preclinical potential as a multiple target drug for ALS treatment.

Unveiling the rolling texture variations ofα-Mg phases in a dual-phase Mg-Li alloy

LZ91 Mg-Li alloy plates with three types of initial texture were rolled by 70%reduction at both room temperature and 200℃to explore the rolling texture formation ofα-Mg phase.The results showed that the rolling texture is largely affected by the initial texture.All the samples exhibited two main texture components as RD-split double peaks texture and TD-split double peaks texture after large strain rolling.The intensity of the two texture components was strongly influenced by the initial orientation and rolling temperature.Extension twinning altered the large-split non-basal orientation to a near basal one at low rolling strain.The basal orientation induced by twinning is unstable,which finally transmitted to the RD-split texture.The strong TD-split texture formed due to slip-induced orientation transition from its initial orientation.The competition between prismaticaand basal slip determined the intensity and tilt angle of the TD-split texture.By increasing the rolling temperature,the TD-split texture component was enhanced in all three samples.Limitation of extension twinning behavior and the promotion of prismatic slip at elevated temperature are the main reasons for the difference in hot and cold rolling texture.

Natural-ageing-enhanced precipitation near grain boundaries in high-strength aluminum alloy

Artificial ageing above 165℃directly after quenching induces the formation of^50 nm wide precipitatefree zone(PFZ)and^100 nm wide precipitate-sparse zone(PSZ)consisting of coarse precipitates with a gradient in size and density toward the grain center in a commercial Al-Zn-Mg-Cu alloy.With the grain size decreasing,the fraction of PFZ and PSZ in a grain becomes larger and could even occupy the entire volume of the grain.This undesirable microstructure near the grain boundary is mitigated substantially by natural pre-ageing,leading to an exceptional enhancement of the age hardening potential at elevated temperatures.Natural ageing could fundamentally alter the precipitation near grain boundary,and is a promising method to optimize the precipitation hardening in high strength aluminum alloys with unconventionally small grains.

Variation of mechanical properties and microstructure of hot-rolled AA2099 Al-Li alloy induced by the precipitation during preheating process

Preheating is the first step for thermal-mechanical processing of the materials. Several preheating schedules were designed based on industrial manufacturing to explore their effect on the microstructure and mechanical properties of AA2099 Al-Li alloy during the following hot rolling. The results show that the mechanical properties of as-rolled sheets are quite sensitive to preheating. Various types of secondary phases, including δ', T1 and T2 phases, were precipitated during the heating process. The difference among precipitates is the main reason to induce the variation of mechanical properties for as-rolled sheets. A rapid heating rate gave rise to the precipitation of δ' phase, which largely promoted yield stress and ultimate tensile strength in as-rolled sheets. T1 phase was more favorable in the preheating with a holding period at 150–250 °C, which caused a moderated strain hardening behavior. Precipitates formed during preheating induced different slip behaviors in the following deformation. The coexistence of T1 and δ' phase could restrict planar slip, which inhibited the formation of the shear band. The difference in the activity of non-octahedral slips and planar slips determined the strain hardening effect, which should be the reason for the variation of mechanical properties of as-rolled sheets.

The Effect of Internal Delamination Damage on the Tensile Strength of Aeronautical Composites

For aeronautical composite materials,the appearance of internal delamination has a fatal impact on their mechanical properties and may even seriously threaten aircraft flight safety.In this study,the effect of internal delamination damage with different sizes and depths on the tensile strength of aeronautical composites was investigated.Firstly,based on carbon-fiber-reinforced composites commonly used in aircraft,laminate specimens with internal delamination damages of different depths and diameters were fabricated,and tensile tests of composite materials were carried out.Then,the finite element model for the carbon-fiber-reinforced laminate specimens was established,and the validity of the model was verified by comparing its simulation results with the experimental data.Furthermore,by changing the geometric parameters of the internal delamination damage model,the influence of delamination damage on the tensile strength of carbon-fiber-reinforced composites was analyzed and summarized.The results show that,on the one hand,for the internal delamination damages of the same area,the closer is the delamination damage to the surface layer,the lower is the tensile strength.In particular,the closer is the delamination damage to the surface layer,the greater is the decrease in tensile strength,which exhibits an obvious nonlinear relationship.On the other hand,for the internal delamination defects of the same depth,the difference in delamination area has little effect on the tensile strength.This law provides a reference for the damage detection and maintenance focus of aeronautical composite structures,which is of great significance to ensure the safe use of aeronautical composites.