耐高温全氟醚橡胶复合材料研究进展与展望

全氟醚橡胶复合材料在较高温时性能保持率最佳,是应对苛刻密封工况的首选材料。近年来,美国、日本、俄罗斯、英国、意大利等国的生产技术日趋成熟,均有批量稳定供货的能力,国内多个机构开展协作攻坚,取得了一定成效,实现工程应用在望。文中对耐275℃高温以上的全氟醚橡胶复合材料的组成及制品的相关国内外研究进展进行了综述,对其在不同领域的应用情况和需要提升的方面做了梳理,并对今后可能突破的拓展方向进行了展望。

Experimental study on mechanical and frost heave behaviors of silty clay improved by polyvinyl alcohol and polypropylene fiber

Silty clay is widely used as subgrade filler in cold regions,which suffer from frost heave in winter and mud pumping in spring.In this study,polyvinyl alcohol(PVA)and polypropylene(PP)fiber were used to improve the mechanical and frost heave behavior of silty clay in cold regions,and the direct shear test and one-dimensional frost heave test were employed in studying improvement effects.Moreover,improvement mechanisms of PVA and PP fiber were analyzed based on test results.The main findings are as follows.(1)Both PP and PVA can heighten the strength of silty clay and suppress frost heave,but the PVA solution has a more decisive influence on improving mechanical properties than PP fiber.(2)The improvement mechanism of the PVA solution is cementing.The improvement effect of 2%PVA solution is the best,which can increase the shear strength by approximately 40%–60%at different stress levels and decrease the frost heave ratio from 0.89%to 0.16%at optimal water content.(3)For 2%PVA improved samples,0.25%PP fiber can further increase soil cohesion by approximately 20–30 kPa at different stress levels and further decrease the frost heave ratio from 0.16%to 0.07%at optimal water content.The improvement effect is neglectable when the PP fiber content exceeds 0.25%.Overall,2%PVA with 0.25%PP fiber is the optimum combination to improve silty clay in cold regions.

Paleozoic post-collisional magmatism and high-temperature granulite-facies metamorphism coupling with lithospheric delamination of the East Kunlun Orogenic Belt,NW China

Lithosphere extension and upwelling of asthenosphere at post-collisional stage of an orogenic cycle generally induce diverse magmatism and/or associated high-temperature metamorphism. Nevertheless, the intimate coexistence of post-collisional magmatic activity and high-temperature metamorphism is rare.In this contribution, a lithological assemblage composing of diverse magmatic rocks deriving from distinct magma sources and coeval high-temperature metamorphism was identified in eastern Kunlun.Petrography, ages, mineral chemistry and whole-rock geochemistry demonstrated that those intimately coexistent diverse rocks were genetically related to post-collisional extension. The garnet-bearing mafic granulites in Jinshuikou area interior of the East Kunlun Orogenic Belt are mainly composed of garnet,orthopyroxene, and plagioclase, with peak metamorphic P–T conditions of ~ 701–756 ℃and 5.6–7.0 kbar,representing a granulite-facies metamorphism at 409.7 ± 1.7 Ma. The diverse contemporaneous magmatic rocks including hornblendites, gabbros and granites yield zircon U–Pb ages of 408.6 ± 2.5 Ma,413.4 ± 4.6 Ma, and 387–407 Ma, respectively. The hornblendites show N-MORB-like REE patterns with(La/Sm)Nvalues of 0.85–0.94. They have positive zircon εHf(t) values of 0.1–4.9 and whole-rock εNd(t) values of 3.9–4.7 but relatively high(^(87)Sr/^(86)Sr)_(i)values of 0.7081 to 0.7088. These features demonstrate that the hornblendites derived from a depleted asthenospheric mantle source with minor continental crustal materials in source. As for the gabbros, they exhibit arc-like elemental signatures, low zircon εHf(t) values(-4.3 to 2.5) and variable whole-rock εNd(t) values(-4.9 to 1.2) as well as high(^(87)Sr/86 Sr)ivalues(0.7068 to 0.7126), arguing for that they were originated from partial melting of heterogeneous lithospheric mantle anteriorly metasomatized by subducted-sediment released melts. Geochemistry of the granites defines their strongly peraluminous S-type signatures. Zircons from the granites yield a large range of εHf(t) values ranging from -30.8 to -5.1, while the whole-rock samples yield consistent(^(87)Sr/86 Sr)ivalues(0.7301 to 0.7342) and negative εNd(t) values(-10.1 to -12.4). These features indicate that the S-type granites could be generated by reworking of an ancient crust. Taken together, the penecontemporaneous magmatism and metamorphic event, demonstrated the early-middle Devonian transition from crustal thickening to extensional collapse. The post-collisional mantle-derived magmas serve as an essential driving force for the high-temperature granulite-facies metamorphism and anataxis of the crust associated with formation of S-type granite. This study not only constructs a more detail Proto-Tethys evolution process of the eastern Kunlun, but also sheds new light on better understanding the intimate relationship between magmatism and metamorphism during post-collisional extensional collapse.

Theoretical insight into the enhanced CH_4 desorption via H_2O adsorption on different rank coal surfaces

The density functional theory was used to investigate the adsorption of CH4and H2O on different rank coal surfaces. The coal rank is the dominant factor in affecting the adsorption capacity of coal. In order to better understand gas and water interaction with coal of different maturity, we developed fourteen coal models to represent the different rank coal. The interactions of CH4and H2O with coal surfaces were studied and characterized by their adsorption energies, Mulliken charges and electrostatic potential surfaces. The results revealed that the interaction between coal and CH4was weak physical adsorption, and that the interaction between coal and H2O consisted of physical and chemical adsorption. Adsorption energy of coal–H2O system was larger than that of coal–CH4on all rank coals, suggesting that the adsorption priority in the coal models is H2O > CH4. Consequently, the injection of H2O into the different rank coal could effectively enhance the coal bed methane (CBM) recovery. © 2016 Science Press

Polycystic ovary syndrome patients with high BMI tend to have functional disorders of androgen excess:a prospective study

Biochemical or clinical changes of hyperandrogenism are important elements of polycystic ovary syndrome （PCOS）. There is currently no consensus on the definition and diagnostic criteria of hyperandrogenism in PCOS. The aim of this study was to investigate the complex symptoms of hyperandrogenic disorders and the correlations between metabolism and hyperandrogenism in patients with PCOS from an outpatient reproductive medicine clinic in China. We conducted a case control study of 125 PCOS patients and 130 controls to evaluate differences in body mass index （BMI）, total testosterone （TT）, modified Ferriman-Gallwey hirsutism score, sex hormone binding globulin （SHBG）, homeostasis model assessment-estimated insulin resistance （HOMA-IR） and free androgen index （FAI） between PCOS patients and controls and subgroups of PCOS. The prevalence of acne and hirsutism did not differ significantly between the hyperandrogenic and non-hyperandrogenic subgroup. Patients with signs of hyper- androgenism had significantly higher BMI （P 〈 0.05）, but differences in TT, SHBG, FAI and waist/hip ratio were insignificant. The odds ratio of overweight was calculated for all PCOS patients. Our results suggest that PCOS patients with high BMI tend to have functional disorders of androgen excess; therefore, BMI may be a strong pre-dictor of hyperandrogenism in PCOS.

Allometry-based estimation of forest aboveground biomass combining LiDAR canopy height attributes and optical spectral indexes

Accurate estimates of forest aboveground biomass(AGB)are essential for global carbon cycle studies and have widely relied on approaches using spectral and structural information of forest canopies extracted from various remote sensing datasets.However,combining the advantages of active and passive data sources to improve estimation accuracy remains challenging.Here,we proposed a new approach for forest AGB modeling based on allometric relationships and using the form of power-law to integrate structural and spectral information.Over 60 km^(2) of drone light detection and ranging(LiDAR)data and 1,370 field plot measurements,covering the four major forest types of China(coniferous forest,sub-tropical broadleaf forest,coniferous and broadleaf-leaved mixed forest,and tropical broadleaf forest),were collected together with Sentinel-2 images to evaluate the proposed approach.The results show that the most universally useful structural and spectral metrics are the average values of canopy height and spectral index rather than their maximum values.Compared with structural attributes used alone,combining structural and spectral information can improve the estimation accuracy of AGB,increasing R^(2) by about 10%and reducing the root mean square error by about 22%;the accuracy of the proposed approach can yield a R^(2) of 0.7 in different forests types.The proposed approach performs the best in coniferous forest,followed by sub-tropical broadleaf forest,coniferous and broadleaf-leaved mixed forest,and then tropical broadleaf forest.Furthermore,the simple linear regression used in the proposed method is less sensitive to sample size and outperforms statistically multivariate machine learning-based regression models such as stepwise multiple regression,artificial neural networks,and Random Forest.The proposed approach may provide an alternative solution to map large-scale forest biomass using space-borne LiDAR and optical images with high accuracy.

MnO_(2) nanosheet modified N, P co-doping carbon nanofibers on carbon cloth as lithiophilic host to construct high-performance anodes for Li metal batteries

Lithium (Li) metal batteries have attracted much attention owing to its ultra-high energy density.However,as important part of Li metal batteries,Li anodes still face many challenges,mainly including uncontrolled dendritic Li formation,dramatical volume variation and serious pulverization.Herein,manganese dioxide (MnO_(2)) nanosheet modified nitrogen (N),phosphorus (P) co-doping carbon nanofibers(NPC) on carbon cloth (CC)(MnO_(2)@NPC-CC) is successfully fabricated through electrodeposition approach and further treated with Li by the molten-infusion method to prepare Li based Mn@NPC-CC(Li-Mn@NPC-CC) electrode.The synergy of MnO_(2) and NPC obviously increases the reaction rate between MnO_(2)@NPC-CC and Li and guides even Li distribution over infusion process.Additionally,theoretical calculation,simulation and experimental results further indicate that N,P,Mn multi-doping effectively improves the superior lithiophilicity of Li-Mn@NPC-CC,which induces uniform Li deposition/dissolution to suppress dendrite growth over cycles.Moreover,conductive and porous NPC matrix not only effectively improves the stability of Li-Mn@NPC-CC,but also provides abundant spaces to accelerate the transfer of ion/electron and buffer electrode dimension variation during cycling.Hence,Li-Mn@NPC-CC-based symmetric cells exhibit extra-long cycling life (over 2200 h) with small hysteresis of 20 mV.When the LiMn@NPC-CC anode couples with air,Li iron phosphate (LiFePO_(4)),or hard carbon (C) cathode,the assembled full cells exhibit outstanding performance with low hysteresis and stable cycling properties.Especially,the corresponding pouch-typed Li–air cells also exhibit good performance at different bending angles and even power a series of electronic devices.

Canopy structure:An intermediate factor regulating grassland diversity-function relationships under human disturbances

Grasslands are one of the largest coupled human-nature terrestrial ecosystems on Earth,and severe anthropogenic-induced grassland ecosystem function declines have been reported recently.Understanding factors influencing grassland ecosystem functions is critical for making sustainable management policies.Canopy structure is an important factor influencing plant growth through mediating within-canopy microclimate(e.g.,light,water,and wind),and it is found coordinating tightly with plant species diversity to influence forest ecosystem functions.However,the role of canopy structure in regulating grassland ecosystem functions along with plant species diversity has been rarely investigated.Here,we investigated this problem by collecting field data from 170 field plots distributed along an over 2000 km transect across the northern agro-pastoral ecotone of China.Aboveground net primary productivity(ANPP)and resilience,two indicators of grassland ecosystem functions,were measured from field data and satellite remote sensing data.Terrestrial laser scanning data were collected to measure canopy structure(represented by mean height and canopy cover).Our results showed that plant species diversity was positively correlated to canopy structural traits,and negatively correlated to human activity intensity.Canopy structure was a significant indicator for ANPP and resilience,but their correlations were inconsistent under different human activity intensity levels.Compared to plant species diversity,canopy structural traits were better indicators for grassland ecosystem functions,especially for ANPP.Through structure equation modeling analyses,we found that plant species diversity did not have a direct influence on ANPP under human disturbances.Instead,it had a strong indirect effect on ANPP by altering canopy structural traits.As to resilience,plant species diversity had both a direct positive contribution and an indirect contribution through mediating canopy cover.This study highlights that canopy structure is an important intermediate factor regulating grassland diversity-function relationships under human disturbances,which should be included in future grassland monitoring and management.

Immunogenicity and Safety of Homologous Booster Doses of CoronaVac COVID-19 Vaccine in Elderly Individuals Aged 60 Years and Older:A Dosing Interval Study—Yunnan Province,China,2021–2022

Summary What is already known about this topic?Neutralization levels induced by inactivated vaccines rapidly wane after primary immunization,and a homologous booster can recall specific immune memory,resulting in a remarkable increase in antibody concentration.The optimal interval between primary and booster doses has yet to be determined.

CD9 negatively regulates collective electrotaxis of the epidermal monolayer by controlling and coordinating the polarization of leader cells

Background:Endogenous electric fields(EFs)play an essential role in guiding the coordinated collective migration of epidermal cells to the wound centre during wound healing.Although polarization of leadercells is essential for collective migration,the signal mechanisms responsible for the EF-induced polarization of leader cells under electrotactic collective migration remain unclear.This study aims to determine how the leader cells are polarized and coordinated during EF-guided collective migration of epidermal cell sheets.Methods:Collective migration of the human epidermal monolayer(human immortalized ker-atinocytes HaCaT)under EFs was observed via time-lapse microscopy.The involvement of tetraspanin-29(CD9)in EF-induced fibrous actin(F-actin)polarization of leader cells as well as electrotactic migration of the epidermal monolayer was evaluated by genetic manipulation.Blocking,rescue and co-culture experiments were conducted to explore the downstream signalling of CD9.Results:EFs guided the coordinated collective migration of the epithelial monolayer to the anode,with dynamic formation of pseudopodia in leader cells at the front edge of the monolayer along the direction of migration.F-actin polarization,as expected,played an essential role in pseudopod formation in leader cells under EFs.By confocal microscopy,we found that CD9 was colocalized with F-actin on the cell surface and was particularly downregulated in leader cells by EFs.Interestingly,genetic overexpression of CD9 abolished EF-induced F-actin polarization in leader cells as well as collective migration in the epidermal monolayer.Mechanistically,CD9 determined the polarization of F-actin in leader cells by downregulating a disintegrin and metalloprotease 17/heparin-binding epidermal growth factor-like growth factor/epidermal growth factor receptor(ADAM17/HB-EGF/EGFR)signalling.The abolished polarization of leader cells due to CD9 overex-pression could be restored in a co-culture monolayer where normal cells and CD9-overexpressing cells were mixed;however,this restoration was eliminated again by the addition of the HB-EGF-neutralizing antibody.Conclusion:CD9 functions as a key regulator in the EF-guided collective migration of the epidermal monolayer by controlling and coordinating the polarization of leader cells through ADAM17/HB-EGF/EGFR signalling.

有生育要求子宫腺肌病患者的妊娠结局真实世界临床数据分析

目的回顾性分析有生育要求子宫腺肌病患者的妊娠结局。方法选取2015年6月至2020年5月在青岛大学附属妇女儿童医院就诊的有生育要求、超声诊断为妊娠合并子宫腺肌病且临床资料完整的患者231例。根据妊娠前子宫腺肌病的治疗方式分为:期待组78例、药物组111例和手术组42例, 分析3组患者治疗前的一般资料, 并总结妊娠结局。再根据早孕期是否予药物保胎治疗, 将自然受孕的无先兆流产症状的患者分为观察组和保胎组, 比较两组患者的早孕期妊娠结局。结果 (1)与期待组相比, 药物组和手术组患者的年龄较大, 分别为(31.5±1.8)、(34.1±3.7)、(36.9±3.6)岁(P<0.05)。期待组有临床症状的患者比例低, 仅占11.5%(9/78), 而药物组和手术组患者发生痛经、经量增多的比例较高。药物组和手术组患者的子宫体积大于期待组, 分别为(151±46)、(166±27)、(97±18)cm^(3)(P<0.05)。手术组患者78.6%(33/42)为局灶型病灶。期待组患者自然受孕的比例为97.4%(76/78), 药物组和手术组患者以辅助生殖治疗为主。(2)期待组、药物组、手术组患者的流产率分别为48.7%(38/78)、46.8%(52/111)、59.5%(25/42)。与药物组和手术组相比, 期待组患者的早产率低, 分别为55.9%(33/111)、11/17、12.5%(5/78), 自然分娩率高, 分别为44.1%(26/111)、4/17、67.5%(27/78)。(3)自然受孕无先兆流产症状的患者共89例, 其中观察组31例、保胎组58例;与观察组相比, 保胎组患者流产率低[41.9%(13/31)、34.5%(20/58)], 两组比较, 差异有统计学意义(P<0.05)。结论有生育要求的子宫腺肌病患者应综合评估, 予以个体化治疗方案。妊娠合并子宫腺肌病患者流产率高, 应纳入高危孕产妇管理。早孕期积极进行保胎治疗, 在一定程度上可改善妊娠结局。

Local engineering of topological phase in monolayer MoS2

Monolayer transition metal dichalcogenides(TMDCs) with the 1 T0 structure are a new class of large-gap two-dimensional(2 D) topological insulators, hosting topologically protected conduction channels on the edges. However, the 1 T0 phase is metastable compared to the 2 H phase for most of 2 D TMDCs, among which the 1 T0 phase is least favored in monolayer MoS2. Here we report a clean and controllable technique to locally induce nanometer-sized 1 T0 phase in monolayer 2 H-MoS2 via a weak Argon-plasma treatment,resulting in topological phase boundaries of high density. We found that the stabilization of 1 T0 phase arises from the concerted effects of S vacancies and the tensile strain. Scanning tunneling spectroscopy(STS) clearly reveals a spin-orbit band gap(~60 meV) and topologically protected in-gap states residing at the 1 T0-2 H phase boundary, which are corroborated by density-functional theory(DFT) calculations.The strategy developed in this work can be generalized to a large variety of TMDCs materials, with potentials to realize scalable electronics and spintronics with low dissipation.

Truss-arch model for shear strength of seismic-damaged SRC frame columns strengthened with CFRP sheets

Carbon fiber reinforced polymer(CFRP)materials are important reinforcing substances which are widely used in the shear strengthening of seismic-damage steel reinforced concrete(SRC)frame structures.To investigate the shear strength of SRC frame columns strengthened with CFRP sheets,experimental observations on eight seismic?damaged SRC frame columns strengthened with CFRP sheets were conducted at Yangtze University and existing experimental data of 49 SRC columns are presented.Based on the existing experiments,the theories of damage degree,zoning analysis of concrete,and strengthening material of the column are adopted.To present the expression formula of the shear strength of SRC frame columns strengthened with CFRP sheets,the contributions of strengthening material and transverse reinforcement to shear strength in the truss model are considered,based on the truss-arch model.The contribution of arch action is also considered through the analysis of the whole concrete and that of the three zones of the concrete are also considered.The formula is verified,and the calculated results are found to match well with the experimental results.Results indicate that the proposed whole analysis model can improve the accuracy of shear strength predictions of shear seismic-damaged SRC frame columns reinforced with CFRP sheets.

The highly dispersed Co-based nanoparticles encapsulated into porous N-doping carbon polyhedral with the low content of Ru modification as a promising cathode catalyst for long-life Li-O_(2)batteries

Lithium(Li)-O_(2)batteries have triggered worldwide interest due to their ultrahigh theoretical energy density.However,it is a long shot for the grand-scale applications of Li-O_(2)battery at current stage owing to its significant polarization,inferior cycling life,and irreversible decomposition of Li2O_(2).Herein,a facile way of preparing the highly dispersed Co-based nanoparticles encapsulated into porous N-doping carbon polyhedral with the low content of Ru modification(LRu@HDCo-NC)is explored through the pyrolysis of Co/Zn based zeolitic imidazole frameworks(ZIFs)containing Ru-based ligands.Even with the very small amount of Ru introduction(1.8%),LRu@HDCo-NC still exhibits the superior oxygen evolution reaction/oxygen reduction reaction(OER/ORR)performance and also inhibits side reactions in Li-O_(2)battery because of the abundant pores,plentiful surface N heteroatoms,and highly dispersed metal-based sites which are induced by the volatilization of Zn,and conductive/stable carbon skeleton derived from ZIFs.When applied in Li-O_(2)batteries,LRu@HDCo-NC cathode delivers a high discharge capacity of 15,973 mAh·g^(-1)at 200 mA·g^(-1),good capacity retention at higher rate(12,362 mAh·g^(-1)at 500 mA·g^(-1))and outstanding stability for>300 cycles with low voltage polarization of<2.3 V under a cut-off capacity of 1,000 mAh·g^(-1)at 500 mA·g^(-1).More critically,a series of ex situ and in situ characterization technologies disclose that the LRu@HDCo-NC cathodes can effectively promote the reversible reactions in Li-O_(2)batteries.

Nonscalability of Fractal Dimension to Quantify Canopy Structural Complexity from Individual Trees to Forest Stands

Canopy structural complexity is a critical emergent forest attribute,and light detection and ranging(lidar)-based fractal dimension has been recognized as its powerful measure at the individual tree level.However,the current lidar-based estimation method is highly sensitive to data characteristics,and its scalability from individual trees to forest stands remains unclear.This study proposed an improved method to estimate fractal dimension from lidar data by considering Shannon entropy,and evaluated its scalability from individual trees to forest stands through mathematical derivations.Moreover,a total of 280 forest stand scenes simulated from the terrestrial lidar data of 115 trees spanning large variability in canopy structural complexity were used to evaluate the robustness of the proposed method and the scalability of fractal dimension.The results show that the proposed method can significantly improve the robustness of lidar-derived fractal dimensions.Both mathematical derivations and experimental analyses demonstrate that the fractal dimension of a forest stand is equal to that of the tree with the largest fractal dimension in it,manifesting its nonscalability from individual trees to forest stands.The nonscalability of fractal dimension reveals its limited capability in canopy structural complexity quantification and indicates that the power-law scaling theory of a forest stand underlying fractal geometry is determined by its dominant tree instead of the entire community.Nevertheless,we believe that fractal dimension is still a useful indicator of canopy structural complexity at the individual tree level and might be used along with other stand-level indexes to reflect the“tree-to-stand”correlation of canopy structural complexity.