Numerical simulation of carbon arc discharge for graphene synthesis without catalyst

In this study, graphene sheets are prepared under a hydrogen atmosphere without a catalyst, and the growth mechanism of graphene by direct current arc discharge is investigated experimentally and numerically. The size and layer numbers of graphene sheets increase with the arc current.Distributions of temperature, velocity, and mass fraction of carbon are obtained through numerical simulations. A high current corresponds to a high saturation temperature, evaporation rate, and mass density of carbon clusters. When the carbon vapor is saturated, the saturation temperatures are 3274.9, 3313.9, and 3363.6 K, and the mass densities are 6.4×1022,8.42×1022, and 1.23×1023 m-3 under currents of 150, 200, and 250 A, respectively. A hydrogen-induced marginal growth model is used to explain the growth mechanism. Under a high current, the condensation coefficient and van der Waals force increase owing to the higher saturation temperature and mass density of carbon clusters, which is consistent with experimental results.

Ecosystem Service Value Assessment of Wutong Mountain Rhododendron moulmainense Ecological Landscape Forest in Shenzhen City in 2021

Taking Wutong Mountain Rhododendron moulmainense ecological landscape forest in Shenzhen City as an example,the value of the forest was assessed by constructing an ecological service value assessment system and accounting method.The assessment results showed that the total ecosystem service value of R.moulmainense ecological landscape forest was 13.195 billion yuan,and the top three services included the value of forestry products,the value of biodiversity maintenance and the value of leisure and recreation,indicating that the ecosystem service of Wutong Mountain R.moulmainense ecological landscape forest in Shenzhen has great ecological and economic value,especially in forestry products,biodiversity maintenance,and leisure and recreation.

Preliminary Study on the Population Structure Characteristics of Symplocos in Xiaolingjiao Area of Huangshan Mountain

[Objectives] This study was conducted to understand the species diversity of plant communities in the Xiaolingjiao area of Anhui Province,and to analyze the current status of the plant resources of Symptocos.[Methods]Quadrats with a total area of 3 600 m^2 were set up in typical evergreen broad-leaved forests in the Xiaolingjiao area of Huangshan Mountain.[Results] There were 79 species of woody plants in the quadrats,belonging to 53 genera of 29 families.As seen from the age class structure,evergreen trees such as Castanopsis eyrei and Eurya nitida were growing populations,and Cyclobalanopsis glauca,Cunninghamia lanceolata,Pinus massoniana and Loropetalum chinense were declining populations.The age class structure of each species in Symplocos was of the growing type,and the various populations had not reached a stable state and would grow continuously.The communities had a tendency to develop to evergreen broad-leaved forests.[Conclusions]This study provides a scientific basis for the protection,development and utilization of Symplocos plants.

A Pilot Study on Biodiversity Friendly Park in Longhua District:Taking Guanlan Printmaking Base as an Example

In order to actively implement the Convention on Biological Diversity and help Shenzhen build a "park city" and a model of beautiful China, the concepts of landscape ecology, landscape urbanism and bio friendly city are introduced to build an evaluation system for biodiversity friendly parks in Longhua District, and explore the relationship between "bio friendly living space" and "city". According to the evaluation system, the Guanlan Printmaking Base scores a total of 273 points, which is rated as a relatively friendly level. In order to coordinate the development between the city and the biosphere and contribute to the goal of building a biodiversity based urban park, the construction of a biodiversity friendly park in Guanlan Printmaking Base is carried out in terms of comprehensive design, plant community construction and biodiversity friendly facilities construction according to the construction principles of biological priority guidance, functional integration and diversification, respect for the park's regionality, and valuing the reachability of natural space.

亚洲水塔水循环和水资源研究进展与展望

亚洲水塔是亚洲地区重要的水资源供给单元,为其周边约8亿人的水资源需求提供保障.亚洲水塔水资源的稳定性与可持续性对周边地区社会经济稳定与可持续发展具有重要意义.受气候变化和人类活动的影响,在过去几十年中,亚洲水塔水资源存量及其可持续性引起了学界高度关注.亚洲水塔冰川消融、冻土退化、湖泊面积扩张、陆地水储量下降等进一步打破了亚洲水塔水资源平衡状态.本文围绕亚洲水塔水循环过程及其效应、水资源变化及其未来预测这一主线,梳理了亚洲水塔气候状态、冰川、径流、湖泊和陆地水储量等水资源组分的变化和影响因素系列研究成果,系统总结了气候变化下亚洲水塔水资源研究进展.在此基础上,从气候变化影响下亚洲水塔水资源存量及变化、亚洲水塔的人类福祉服务与可持续发展和跨域协同系统治理等方面讨论了亚洲水塔水资源失衡面临的挑战和未来的研究展望,以期推动亚洲水塔周边国家未来水资源科学管理与经济社会可持续发展.

Biomechanical Effects of Tibial Stems with Different Structures on Human Knee Joint after Total Knee Arthroplasty: A Finite Element Analysis

Porous structure in orthopedic prosthesis may reduce micromotion and increase the service life of implants.The purposes of this study were to compare the influence of the tibial stems with solid and porous structures in Total Knee Arthroplasty(TKA)on knee joint and prostheses,and to improve the mechanical stability of the host bone by seeking favorable structure for the tibial stem.The Finite Element(FE)models of TKA knee with four different structures in the middle segment of the tibial stem(i.e.,solid,cubic,truncated cubic,and octahedral structures)were constructed.The distributions of von Mises stress in the knee joint,tibial prosthesis and proximal tibia,and the compressive stresses of the tibial prosthesis and ultra-high-molecular-weight polyethylene for the four FE models were analyzed.The results showed that the tibial stem filled with the octahedral structure has the best mechanical performance among the above four types of tibial stems.It could effectively reduce the stress concentration and stress shielding effects,and provide an improved mechanical environment for knee joint after TKA.This study would shed some lights on the design and fabrication of porous implants targeted to biomedical applications.

Magnetic Micromanipulation for In Vivo Measurement of Stiffness Heterogeneity and Anisotropy in the Mouse Mandibular Arch

The mechanical properties of tissues are pivotal for morphogenesis and disease progression.Recent approaches have enabled measurements of the spatial distributions of viscoelastic properties among embryonic and pathological model systems and facilitated the generation of important hypotheses such as durotaxis and tissue-scale phase transition.There likely are many unexpected aspects of embryo biomechanics we have yet to discover which will change our views of mechanisms that govern development and disease.One area in the blind spot of even the most recent approaches to measuring tissue stiffness is the potentially anisotropic nature of that parameter.Here,we report a magnetic micromanipulation device that generates a uniform magnetic field gradient within a large workspace and permits measurement of the variation of tissue stiffness along three orthogonal axes.By applying the device to the organ-stage mouse embryo,we identify spatially heterogenous and directionally anisotropic stiffness within the mandibular arch.Those properties correspond to the domain of expression and the angular distribution of fibronectin and have potential implications for mechanisms that orient collective cell movements and shape tissues during development.Assessment of anisotropic properties extends the repertoire of current methods and will enable the generation and testing of hypotheses.

Papillary fibroblast-recruiting injectable self-healing multifunctional hydrogels for wound regeneration

The recruitment of key cells to regeneration sites is a promising strategy to promote functional wound healing.Dermal fibroblasts exhibit a heterogeneous population of cells during homeostasis and in response to injury.Papillary fibroblasts play central regulatory roles in the regeneration of skin appendages during wound healing.Inspired by the phenomenon where bait for grass carp can attract grouped grass carps to a fishing spot soon,“Grass Carp Fishing”multifunctional hydrogels,that is,codelivery of an antibody of leucine-rich repeats and immunoglobulin-like domains 1(Lrig1)on the surface of papillary fibroblasts and insulinlike growth factor 1(IGF1)with recruitment function,can recruit papillary fibroblasts.In the experiments,carboxymethyl chitosan showed positive effects in promoting cell proliferation and neovascularization,while dopamine-grafted gelatin was effective in stabilizing the structure and prolonging the degradation time.The sustained release of Lrig1 antibodies and IGF1 from injectable self-healing multifunctional hydrogels persistently accelerated the migration and proliferation of Lrig1+fibroblasts.The in vivo results from a full-thickness cutaneous wound model showed that injectable self-healing multifunctional hydrogel accelerated wound healing and skin regeneration through the recruitment of Lrig1+papillary fibroblasts in wound tissue.Our findings reveal an injectable self-healing multifunctional hydrogel for regeneration,a promising approach to promoting skin wound healing.

Evolution characteristics of the Atlantic Meridional Overturning Circulation and its thermodynamic and dynamic effects on surface air temperature in the Northern Hemisphere

Based on modern observations,historical proxy data,and climate model simulations,this paper provides a comprehensive overview of the past,present and future evolution characteristics of the Atlantic Meridional Overturning Circulation(AMOC),as well as its impact on the surface air temperature(SAT)at regional and hemispherical scales.The reconstruction results based on the proxy data indicate that the AMOC has weakened since the late 19th century and experienced overall weakening throughout the 20th century with low confidence.Direct observations show that the AMOC weakened during 2004–2016,but it is not possible to distinguish between its decadal variability and long-term trend.Climate models predict that if greenhouse gas emissions continue to increase,AMOC will weaken in the future,but there will not be a sudden collapse before 2100.For the thermodynamic effects of AMOC,the increased surface heat flux release and meridional heat transport(MHT)over the North Atlantic associated with the strong AMOC cause an increase in the hemispherical SAT.At the millennial scale,climate cooling(warming)periods correspond to a weakened(strengthened)AMOC.The enhanced MHT of a strong AMOC can affect Arctic warming and thus influence regional SAT anomalies and SAT extremes through mutual feedback between Arctic sea ice and AMOC.In terms of dynamic effects,a strong AMOC modulates the Rossby wave trains originating from the North Atlantic and spreading across mid-to-high latitudes in the Northern Hemisphere and causes an increase in the variabilities in the circulation anomalies over the Ural and Siberian regions.Ultimately,a strong AMOC significantly affects the frequencies of extreme cold and warm events in the mid-to-high latitude regions over Eurasia.In addition,AMOC can also influence regional and global SAT anomalies through its dynamic adjustment of planetary-scale circulation.Decadal variation in AMOC is closely related to the Atlantic Multidecadal Oscillation(AMO).During positive phases of AMO and AMOC,enhanced surface heat fluxes over the North Atlantic lead to abnormal warming in the Northern Hemisphere,while during negative phases,the reverse case occurs.Under high emission scenarios in the future,the possibility of AMOC collapse increases due to freshwater forcing.However,most advanced climate models underestimate the strength of the AMOC and its impact on the AMO and relevant climate change,which presents a major challenge for future understanding and prediction of the AMOC and its climate effects.

早期筛查老年人群糖尿病视网膜病变的卫生经济学分析

目的从社会角度和卫生系统角度探讨中国50岁以上人群行糖尿病视网膜病变(DR)筛查的经济学效益。方法检索中国知网、万方数据库、PubMed及Medline等数据库,检索日期为自建库之始至2020年12月,搜集中国50岁以上人群DR的患病率、转归率、筛查依从性、治疗依从性、筛查敏感性、筛查特异性、DR不同分期的效用值及死亡率等指标。按照国际分级系统将DR分为不威胁视力DR、威胁视力DR,糖尿病性黄斑水肿及DR致盲等4个阶段。筛查项目、转诊检查及治疗费用来源于邯郸眼病研究和2020年首都医科大学附属北京同仁医院住院系统。使用TreeAge Pro软件构建DR筛查的马尔可夫模型,以社区筛查、远程筛查及人工智能(AI)辅助筛查为研究策略,以无筛查为对照策略,以我国农村和城市50岁以上人群为队列人群,比较不同策略的成本效益,并比较1~5年筛查间隔的成本效益。2020年中国农村和城市人均生产总值(GDP)分别为49000元和84000元。经济学效益以增量成本-效用比(ICUR)和增量成本-效果比(ICER)表示。成本效益阈值按照世界卫生组织规定的ICER或ICUR<3倍人均GDP为具有成本效益,<1倍人均GDP为具有高成本效益,>3倍人均GDP则不具备经济性。通过敏感性分析评价模型的稳健性。结果农村和城市人群的成本效益阈值分别为147000元和252000元。从社会角度看,对农村50岁以上人群进行社区、远程及AI辅助筛查的ICUR分别为4214元、2772元及3206元;每避免1个致盲年导致的ICER分别为216524元、152726元及164745元;对城市人群筛查的ICUR分别为7133元、5061元及5894元;每避免1个致盲年导致的ICER分别为57792元、37632元及55839元。与无筛查人群相比,农村和城市的ICUR以及城市人群的ICER均<1倍人均GDP;3种筛查方式对农村50岁以上人群的ICER均略高于成本效益阈值。从卫生系统角度看,3种筛查方式对农村和城市老年人群的ICUR和ICER均低于成本效益阈值。社区或AI辅助筛查对城市老年人群间隔2年以上具有成本效益,远程筛查间隔1年以上已具有成本效益;而对农村人群各筛查间隔均不具有成本效益。经概率敏感性分析,当成本效益阈值为3倍人均GDP时,农村老年人群社区、远程及AI辅助筛查成本效益概率分别为87.34%、87.56%及87.54%;城市老年人群筛查的成本效益概率分别为89.19%、89.48%及89.61%。当成本效益阈值为1倍人均GDP时,3种筛查方式对农村老年人群筛查有成本效益的概率分别为86.03%、86.84%及86.55%;城市老年人群的成本效益概率分别为87.83%、88.55%及88.62%。说明构建马尔可夫模型的设计和结果稳健,对参数的浮动不敏感。结论对我国50岁以上老年人群进行DR筛查具有成本效益,因农村和城市的经济发展水平和疾病负担不同,应制定适宜当地的DR筛查模式。