Dynamical analysis of submesoscale fronts associated with wind-forced offshore jet in the western South China Sea

This study investigates the submesoscale fronts and their dynamic effects on the mean flow due to frontal instabilities in the wind-driven summer offshore jet of the western South China Sea(WSCS),using satellite observations,a 500 m-resolution numerical simulation,and diagnostic analysis.Both satellite measurements and simulation results show that the submesoscale fronts occupying a typical lateral scale of O(~10)km are characterized with one order of Rossby(Ro)and Richardson(Ri)numbers in the WSCS.This result implies that both geostrophic and ageostrophic motions feature in these submesoscale fronts.The diagnostic results indicate that a net cross-frontal Ekman transport driven by down-front wind forcing effectively advects cold water over warm water.By this way,the weakened local stratification and strong lateral buoyancy gradients are conducive to a negative Ertel potential vorticity(PV)and triggering frontal symmetric instability(SI)at the submesoscale density front.The cross-front ageostrophic secondary circulation caused by frontal instabilities is found to drive an enhanced vertical velocity reaching O(100)m/d.Additionally,the estimate of the down-front wind forcing the Ekman buoyancy flux(EBF)is found to be scaled with the geostrophic shear production(GSP)and buoyancy flux(BFLUX),which are the two primary energy sources for submesoscale turbulence.The large values of GSP and BFLUX at the fronts suggest an efficient downscale energy transfer from larger-scale geostrophic flows to the submesoscale turbulence owing to down-front wind forcing and frontal instabilities.In this content,submesoscale fronts and their instabilities substantially enhance the local vertical exchanges and geostrophic energy cascade towards smaller-scale.These active submesoscale processes associated density fronts and filaments likely provide new physical interpretations for the filamentary high chlorophyll concentration and frontal downscale energy transfer in the WSCS.

Evaluation of CMPAS precipitation products over Sichuan,China

高质量和高分辨率的降水产品在天气预报,数值模式模拟和气象防灾减灾方面起着重要的作用.本文利用四川地区高密度的地面降水传感器观测数据,比较CMPAS四种不同时空尺度的降水实况分析产品,评估CMPAS的融合准确性与在四川地区的适用性.研究表明:四种CMPAS降水产品都在四川盆地内精度较高,攀西地区和川西高原次之.随着降水量的增加,产品的误差也随之增加.CMPAS在夏秋两季对降水量高估,在春冬两季对降水量低估.总而言之,CMPAS在四川盆地内与观测数据的融合准确性较高.由于高原地区气象观测站点数量不足且观测数据受复杂地形和气候条件影响较大,CMPAS在高原地区的适用性检验仍需进一步研究.

基于红外相机的黔金丝猴及其同域分布物种种间关联

种间关系是群落生态学研究的核心内容之一,是研究物种演化和物种多样性保护的关键。掌握黔金丝猴(Rhinopithecus brelichi)与其所在群落物种的种间生态学关系对黔金丝猴的综合保护具有重要指导意义。本研究基于2017–2022年在梵净山国家级自然保护区开展的红外相机监测数据,运用空间关联方法构建黔金丝猴地栖鸟兽关联网络,探讨了黔金丝猴在群落中的生态学作用及其保护问题。结果表明:(1)黔金丝猴与藏酋猴(Macacathibetana)、红腹角雉(Tragopantemminckii)、中华鬣羚(Capricornis milneedwardsii)、食蟹獴(Herpestes urva)、马来豪猪(Hystrix brachyura)、猪獾(Arctonyx collaris)、野猪(Sus scrofa)、勺鸡(Pucrasiamacrolopha)和小麂(Muntiacusreevesi)存在空间关联,其所处群落的物种组成与川金丝猴(Rhinopithecus roxellana)较为相似。(2)梵净山国家级自然保护区没有捕食黔金丝猴的地栖性天敌。(3)黔金丝猴与中华鬣羚、食蟹獴、马来豪猪、野猪、小麂和勺鸡存在竞争生态学关系,这些物种种群的过度增长可能会排挤黔金丝猴的生存空间,抑制黔金丝猴种群的增长。(4)黔金丝猴能够从藏酋猴和红腹角雉的存在中获利,对二者的有效保护在一定程度上有助于黔金丝猴的生存。(5)对黔金丝猴的有效保护有助于猪獾和红腹角雉的生存,也更有利于维持群落的稳定。本研究从空间角度初步探讨了黔金丝猴的种间生态学关系,研究发现,黔金丝猴不仅从群落中获益,也具有维持群落稳定的重要作用。在未来的保护和管理中,加强对黔金丝猴的单物种保护措施的同时,应强化多物种的综合平衡保护措施。

新加坡民族政策的变迁与族群意识的演化

新加坡素有“世界人种博物馆”之称,因而处理好各个族群之间的关系是新加坡自独立以来一项非常重要的课题。新加坡独立初期,国内各民族间诸如宗教、语言问题丛生,且主要民族间冲突不断。然而,50年后的今天,新加坡主要族群间关系却呈现出显著的和谐局面。族群关系的前后变化反映的是新加坡族群意识的淡化和国民意识提高的演化逻辑。那么,这一演化逻辑背后新加坡民族政策发挥了怎样的作用?基于这一思考,本文着眼于新加坡民族议题,以不同时期的民族政策和民族关系的变迁为脉络,剖析新加坡民族意识发展及国民意识提高的过程。研究认为,民族政策对族群意识有着淡化和塑造的双重功能,当不同的政策作用于多元民族国家时,政策的张力(即包容性和适用性范围)也使民族关系呈现融合或冲突的情形。新加坡独立后多元一体的民族政策调控淡化了狭隘的民族自我意识,并塑造演化出国民意识,这是如今新加坡主要族群之间关系和睦与民族凝聚力增强的根本原因。

Bioadaptable bioactive glass-β-tricalcium phosphate scaffolds with TPMS-gyroid structure by stereolithography for bone regeneration

Bone defect repair remains a troubling problem in clinical orthopedics,which involves complex biological processes.Calcium phosphates(CaPs)have been widely used owing to their advantage of biocompatibility.However,single component and traditional fabrication methods cannot meet the requirements of bioadaptability during the tissue repair process.In this work,0%,5%,15%,25%wt%of BG-TCP(bioactive glass-β-tricalcium phosphate)bioresorbable scaffolds with triply-periodic minimal surfaces(TPMS)-gyroid structure were prepared by the stereolithography(SLA)technology.TPMS-gyroid structure provided an accurate mimicry of natural bone tissue,and the incorporation of BG improved the compressive strength ofβ-TCP matrix,matched with the defective bone(2–12 MPa).Rapid but tunable degradation kinetics(compared with pure TCP)of BG enabled the BG-TCP system to sh8ow adaptable biodegradability to new bone generation.In vitro studies have shown that composite scaffolds have better mechanical properties(7.82 MPa),and can released appropriate contents of calcium,phosphorous,and magnesium ions,which promoted the osteogenic differentiation of bone marrow mesenchymal stem cells(BMSCs)and angiogenic ability of endothelial progenitor cells(EPCs).Moreover,the in vivo assessment of rat femoral defect revealed that TPMS-structure-based TCP scaffolds accelerated bone ingrowth to the pores.Moreover,BG-TCP scaffolds,especially 15BG-TCP group,exhibited superior bone regeneration capacity at both 4 and 8 weeks,which achieved an optimal match between the rate of material degradation and tissue regeneration.In summary,this study provides insight into influences of bioactive components(BG)and bionic structures(TPMS)on the physical-chemical properties of materials,cell behavior and tissue regeneration,which offers a promising strategy to design bioadaptive ceramic scaffolds in the clinical treatment of bone defects.

Application of heat-activated peroxydisulfate process for the chemical cleaning of fouled ultrafiltration membranes

Na Cl O has been widely used to restore membrane flux in practical membrane cleaning processes,which would induce the formation of toxic halogenated byproducts.In this study,we proposed a novel heatactivated peroxydisulfate(heat/PDS)process to clean the membrane fouling derived from humic acid(HA).The results show that the combination of heat and PDS can achieve almost 100%recovery of permeate flux after soaking the HA-fouled membrane in 1 mmol/L PDS solution at 50℃ for 2 h,which is attributed to the changes of HA structure and enhanced detachment of foulants from membranes.The properties of different treated membranes are characterized by scanning electron microscopy(SEM),atomic force microscope(AFM),attenuated total reflection Fourier transform infrared spectroscopy(ATRFTIR),and X-ray photoelectron spectroscopy(XPS),demonstrating that the reversible and irreversible foulants could be effectively removed by heat/PDS cleaning.The filtration process and fouling mechanism of the cleaned membrane were close to that of the virgin membrane,illustrating the good reusability of the cleaned membrane.Additionally,heat/PDS which can avoid the generation of halogenated byproducts shows comparable performance to Na Cl O on membrane cleaning and high performance for the removal of fouling caused by sodium alginate(SA),HA-bovine serum albumin(BSA)-SA mixture and algae,further suggesting that heat/PDS would be a potential alternative for membrane cleaning in practical application.

Global model of plasma-activated water over long time scale:Pulsed discharge and afterglow

Plasma-activated water(PAW)has been utilised in various application fields,and a deep understanding on the plasma chemistry is the foundation of application-orientated optimisation.In this paper,a global model is built to study the chemical properties of PAW produced by a dielectric barrier discharge that is powered by nanosecond voltage pulses.The applied voltage is firstly repeated with 10 kHz frequency for 100 s,and then shut down for 200 s afterglow,providing a long-term evolution regarding the production and consumption of some typical reactive oxygen/nitrogen species(RONS)in PAW.The calculated results agree principally with experimental measurements from literature.During the pulsed discharge,the water gradually acidises,and the long-lived species accumulate;while in the afterglow,most of the aqueous RONS decay rapidly,except for O_(3aq),NO_(3aq)^(−),H_(2)O_(2aq)and N_(2)O_(aq),which might be the main sources to sustain long-term effects.Furthermore,the effects of applied voltage and gap distance on RONS are investigated.Correlation analyses from Pearson correlation coefficient indicate that gaseous RONS are more sensitive to the gap distance,while the aqueous ones are more sensitive to the voltage amplitude,suggesting the possibility to independently regulating the gaseous and aqueous chemistry.

The root structures of 21 aquatic plants in a macrophyte-dominated lake in China

Aims Aquatic plants play an important role in freshwater ecosystems.Previous works have largely focused on the functional significance of plant above ground parts,with much less attention on the root structures of aquatic plants.In this study,we divided 21 aquatic plants(including five introduced plants)into multiple plant groups(different life forms,monocot/eudicot and introduced/native)with the goal of addressing two questions:(i)what root structures do aquatic plants exhibit,and(ii)are there differences among these plant groups?Methods Twenty-one aquatic plants belonging to four life forms(free-float-ing,emergent,floating-leaved and submerged)were collected at the near flowering stage from a typical macrophyte-dominated lake in the yangtze River Basin,China.The following root topological parameters were quantified:altitude(a),path length(pe),magnitude(M),mean topological length(b),topological index(TI)and normed indices qa and qb.Important Findings The root topological indices TI,qa and qb for the 21 aquatic plants were 0.724±0.013,0.290±0.031 and 0.152±0.024(means±S.E.),respectively,revealing a general pattern of dichotomous branching,except for the aquatic root of Myriophyllum aquati-cum(Vell.)Verdc.,which displays herringbone branching.All three topological indices were significantly lower for monocots(TI=0.700±0.130,qa=0.191±0.149 and qb=0.086±0.236)than eudicots(TI=0.752±0.206,qa=0.405±0.569 and qb=0.229±0.393),indicating that the roots of monocots are typi-cally more dichotomous-like than those of eudicots.Among the four life forms,the three topological indices for emergent plants(TI=0.832±0.006,qa=0.616±0.018 and qb=0.381±0.014)were significantly higher than those of the other three life forms.Overall,there was no difference between the topological indices of introduced and native aquatic plants,but the introduced species M.aquaticum and Alternanthera philoxeroides(Mart.)Griseb.had both aquatic and edaphic roots as well as unusual functions,which may help explain their strong viability.

3种入侵和本地沉水植物形态和生理性状对螺类牧食的响应

沉水植物水盾草(Cabomba caroliniana)已成为中国太湖流域的优势入侵水生植物。与外来物种的原产地环境相比,引入地新环境中存在的专食性天敌较少。外来物种可能会逃避其原产地环境中的天敌牧食,又因为它们的适口性相对较差,从而导致在引入地外来物种通常比本地物种遭受的牧食者影响更低(天敌逃逸假说)。本研究的目的是比较水盾草与共生的本地沉水植物对本地牧食者的响应。我们进行了一个中宇宙尺度实验,研究了水盾草和两种共生的本地沉水植物黑藻(Hydrilla verticillata)和穗花狐尾藻(Myriophyllum spicatum)对两种本地广食性腹足纲螺类萝卜螺(Radix swinhoei)和环棱螺(Sinotaia quadrata)的牧食响应。记录了它们的形态性状指标(总生物量、冠根比和相对生长率)和生理性状指标(叶片总非结构性碳、木质素和纤维素)。研究结果表明,环棱螺对3种沉水植物性状指标的影响较少。随着本地广食性螺类萝卜螺数量的增加,黑藻和穗花狐尾藻大部分植物性状发生了改变,而水盾草的植物性状表现出相对稳定的趋势。水盾草对萝卜螺的牧食更具抵抗力,这与天敌逃逸假说的假设一致。这一发现说明牧食性螺类促进了水盾草的入侵,这可能会改变沉水植物群落中的物种组成。