关注三十岁:脑科学视角下的三十岁女性

随着一些有关30岁女性影视节目的热播,“30岁女性”的相关话题在社交媒体上引起广泛的讨论.在古代社会,30岁左右的女性曾被称作“半老徐娘”.在历史文化长河中,这一称谓已延续千年.但在今天,“徐娘”这一称谓已经不再适合现代背景下的新时代女性.古时的认识受时代限制,认为30岁就已是“半老”,但在现代社会中,30岁恰恰是刚踏入事业发展高峰、迈向人生新阶段的黄金岁月.

Acoustic emission characteristics of damage evolution of multi-scale fiber reinforced rubberized concrete under uniaxial compression and tension after being subjected to high temperatures

Recently developed multi-scale fiber(i.e.,CaCO3 whisker,polyvinyl alcohol(PVA)fiber,and steel fiber)reinforced rubberized concrete exhibits excellent mechanical properties and spalling resistance at high temperatures.Measurement of macro properties such as strength and Young’s modulus cannot reveal and characterize damage mechanisms,particularly those relating to the multi-scale fiber strengthening effect.In this study,acoustic emission(AE)technology is applied to investigate the impact of multi-scale fiber on the damage evolution of rubberized concrete exposed to high temperatures,under the uniaxial compression and tension loading processes.The mechanical properties,AE event location,peak frequency,b-value,the ratio of rise time to amplitude(RA),average frequency(AF)values,and AE energy of specimens are investigated.The results show that the number of events observed using AE gradually increases as the loading progresses.The crumb rubber and fibers inhibit the generation and development of the cracks.It is concluded that both the peak frequency and b-value reflect the extension process of cracks.As the cracks develop from the micro scale to the macro scale,the peak frequency tends to be distributed in a lower frequency range,and the b-value decreases gradually.At the peak stress point,the AE energy increases rapidly and the b-value decreases.The specimens without multi-scale fibers exhibit brittle failure,while the specimens with fibers exhibit ductile failure.In addition,adding multi-scale fibers and crumb rubber increases the peak frequency in the medium and high frequency ranges,indicating a positive effect on inhibiting crack development.After being subjected to high temperatures,the maximum and minimum b-values decrease,reflecting an increase in the number of initial cracks due to thermal damage.Meanwhile,the RA and AF values are used to classify tensile and shear cracks.The specimens fracture with more shear cracks under compression,and there are more tensile cracks in specimens with multi-scale fibers under tension.

New insights into the effect of molecular crowding environment induced by dimethyl sulfoxide on the conformation and stability of G-quadruplex

Various structures of G-quadruplex in biosystems play an important role in different diseases and are often regulated by a variety of molecular crowding environments induced by internal and even external factors(e.g.,a solvent).Dimethyl sulfoxide(DMSO),a universal solvent,has been widely used in biological studies and for drug therapy,but little is known regarding its effect on G-quadruplex structure and stability.Here,we report the influence of molecular crowding environment induced by DMSO on the conformation and stability of G-quadruplex structure.We show that the G-quadruplex-forming sequences such as human telomeric sequence,which may have diverse conformations in different environments,tend to convert their topologies to parallel structures under the molecular crowding stimulated by DMSO.Moreover,DMSO can increase the stability of the parallel and antiparallel topologies,especially the parallel G-quadruplex sequence c-kit,but not the hybrid topologies.Further analysis of c-kit using the CD and NMR technique,combined with the unique structural characteristics of c-kit,reveals that the crowding,dehydration and interaction of DMSO are conductive to the formation and stability of the parallel G-quadruplex.The present study suggests that,DMSO,a common solvent used in DNA experiments,may have a nonnegligible influence on the structure and stability of G-quadruplex.

Controlled growth of ultrathin ferromagneticβ-MnSe semiconductor

Two-dimensional(2D)magnetic crystals with intrinsic ferromagnetism are highly desirable for novel spin-electronic devices.However,the controllable synthesis of 2D magnets,especially the direct growth of 2D magnets on substrate surfaces,is still a challenge.Here,we demonstrate the synthesis of ultrathin zinc-blende phase manganese selenide(β-MnSe)nanosheets using the chemical vapor deposition(CVD)technique.The 2Dβ-MnSe crystals exhibit distinct ferromagnetic properties with a Curie temperature of 42.3 K.Density functional theory(DFT)calculations suggest that the ferromagnetic order inβ-MnSe originates from the exchange coupling between the unsaturated Se and Mn atoms.This study presents significant progress in the CVD growth of ultrathin 2D magnetic materials by thinning bulk magnets,and it will pave the way for the building of energy-efficient spintronic devices in the future.

Different Flooding Behaviors Due to Varied Urbanization Levels within River Basin: A Case Study from the Xiang River Basin,China

Booming urbanization due to a fast-growing population results in more impervious areas, less infiltration,and hence greater flood peak and runoff. Clear understanding of flood responses in regions with different levels and expansions of urbanization is of great importance for regional urban planning. In this study, comparison of flooding responses to urbanization processes in terms of flood peak and runoff volume in the upper, middle,and lower Xiang River Basin(XRB), China, was carried out using the Hydrologic Engineering Center-Hydrologic Modeling System(HEC-HMS) model. From 2005 to 2015, urbanization level and intensity were higher in the lower XRB compared to the upper and middle XRB, and the overall expansion rate of urban areas was 112.8%.Modeling results by the HEC-HMS model indicate elevated flood peak discharges and volumes due to fast urbanization in the XRB from the 1980 s to 2015. This rapid increase is particularly the case in the lower XRB. The study also revealed different hydrological responses of flood regimes—urbanization tends to have larger impacts on peak flood flow rather than on flood volume in the lowerXRB, which further corroborated urbanization-induced intensifying flood processes in terms of peak flood flow.Urbanization has increasing impacts on flood volume from the upper to the lower XRB, which can be attributed to accumulated runoff down the river system. This study provides a reference for basin-wide land use and urban planning as well as flood hazard mitigation.