Analytical evaluation of steady-state solute distribution in through- diffusion and membrane behavior test under non-perfectly flushing boundary conditions

The through-diffusion and membrane behavior testing procedure using a closed-system apparatus has been widely used for concurrent measurement of diffusion and membrane efficiency coefficients of low-permeability clay-based barrier materials.However,the common assumption of perfectly flushing conditions at the specimen boundaries could induce errors in analyses of the diffusion coefficients and membrane efficiencies.In this study,an innovative pseudo three-dimensional(3D)analytical method was proposed to evaluate solute distribution along the boundary surfaces of the soil-porous disks system,considering the non-perfectly flushing conditions.The results were consistent with numerical models under two scenarios considering different inflow/outflow positions.The proposed model has been demonstrated to be an accurate and reliable method to estimate solute distributions along the bound-aries.The calculated membrane efficiency coefficient and diffusion coefficient based on the proposed analytical method are more accurate,resulting in up to 50%less relative error than the traditional approach that adopts the arithmetic mean value of the influent and effluent concentrations.The retar-dation factor of the clay specimen also can be calculated with a revised cumulative mass approach.Finally,the simulated transient solute transport matched with experimental data from a multi-stage through-diffusion and membrane behavior test,validating the accuracy of the proposed method.

Enhanced sampling for lipid-protein interactions during membrane dynamics

The inflexible concept of membrane curvature as an independent property of lipid structures is today obsolete.Lipid bilayers behave as many-body entities with emergent properties that depend on their interactions with the environment.In particular,proteins exert crucial actions on lipid molecules that ultimately condition the collective properties of the membranes.In this review,the potential of enhanced molecular dynamics to address cell-biology problems is discussed.The cases of membrane deformation,membrane fusion,and the fusion pore are analyzed from the perspective of the dimensionality reduction by collective variables.Coupled lipid-protein interactions as fundamental determinants of large membrane remodeling events are also commented.Finally,novel strategies merging cell biology and physics are considered as future lines of research.

Insight into fouling behavior of poly(vinylidene fluoride)(PVDF)hollow fiber membranes caused by dextran with different pore size distributions

Membrane fouling is the key problem that occurs in membrane process for water treatment. However, how membrane microstructure influences the fouling behavior is still not clear. In this study, fouling behavior caused by dextran was deeply and systematically investigated by employing four poly（vinylidene fluoride） （PVDF） membranes with different pore sizes, ranging from 24 to 94 nm. The extent of fouling by dextran was accurately characterized by pore reduction, flux decline, and the change of critical flux. The result shows that membrane with the smallest pore size of 24 nm experienced the smallest fouling rate and the lowest fouling extent. As the membrane pore size increased, the critical flux ranges were 105-114, 63-73, 38-44 and 34- 43 L. m 2. h t, respectively. The critical flux and fouling resistances indicated that the fouling propensity in- creases with the increase of membrane pore size. Two pilot membrane modules with mean pore size of 25 nm and 60 nm were applied in membrane filtration of surface water treatment. The results showed that serious ir- reversible membrane fouling occurred on the membrane with pore size of 60 nm at the permeate flux of 40.5 L.m 2.h 1. On the other hand, membrane with pore size of 25 nm exhibited much better anti-fouling per- formance when permeate flux was set to 40.5, 48 and 60 L-m 2-h- 1.

Electro-viscoelastic behaviors of circular dielectric elastomer membrane actuator containing concentric rigid inclusion

The time-dependent electro-viscoelastic performance of a circular dielectric elastomer(DE) membrane actuator containing an inclusion is investigated in the context of the nonlinear theory for viscoelastic dielectrics. The membrane, a key part of the actuator, is centrally attached to a rigid inclusion of the radius a, and then connected to a fixed rigid ring of the radius b. When subject to a pressure and a voltage, the membrane inflates into an out-of-plane shape and undergoes an inhomogeneous large deformation. The governing equations for the large deformation are derived by means of non-equilibrium thermodynamics, and viscoelasticity of the membrane is characterized by a rheological spring-dashpot model. In the simulation, effects of the pressure, the voltage, and design parameters on the electromechanical viscoelastic behaviors of the membrane are investigated. Evolutions of the considered variables and profiles of the deformed membrane are obtained numerically and illustrated graphically. The results show that electromechanical loadings and design parameters significantly influence the electro-viscoelastic behaviors of the membrane. The design parameters can be tailored to improve the performance of the membrane. The approach may provide guidelines in designing and optimizing such DE devices.

Membrane behavior of bentonite-amended Fukakusa clay in K, Na and Ca solutions

Bentonite has been proven to be effective in enhancing the membrane property of clay, by which landfill liners can have better barrier performance with regard to the migration of contaminants. In this work, 5% sodium bentonite amended with locally available Fukakusa clay was utilized to evaluate the membrane behavior toward different kinds of ions： K, Na and Ca. The chemico-osmotic efficiency coefficient, co, was obtained in electrolyte solution with different concentrations of 0.5, 1, 5, 10, and 50 mmol/L. According to the results, solute type and ion valence have a significant effect on membrane behaviors. Additionally, co continually decreased as the Na and Ca concentrations increased, which is consistent with the Gouy-Chapman theory. The membrane behavior toward Na was similar to that toward K, according to the chemico-osmotic efficiency coefficient co. In the case of the divalent ion Ca, the membrane behavior was lower compared to monovalent ions Na and K at the same concentration. The mechanisms of the membrane performance change were discussed with the assistance of XRD patterns, free-swelling results and SEM images.

STUDY ON THE ELECTROCHEMICAL BEHAVIOR OF ION EXCHANGE MEMBRANE IN PREPARING POTASSIUM CARBONATE

This investigation describes the one step preparation of potassium carbonate by electrolysis of potas-sium chloride solution in electrolyzers with various Nation membranes.Potassium bicarbonate solution wasfed to the cathode compartment,where it was converted into carbonate by reaction with the hydroxideformed at cathode.Because of the low OH^- concentration in the cathode compartment,the back migrationof OH^- through the membrane was almost negligible,resulting in a higher current efficiency,say 90% or more.In this study,electroconductivity,mass transfer,current efficiency and cell voltage were measured.Thefeasibility of the process was discussed and the optimal conditions examined.

Effects of Sintering Atmosphere on the Microstructure and Surface Properties of Symmetric TiO2 Membranes

The effects of sintering atmosphere on the properties of symmetric TiO2 membranes are studied with regard to sintering behavior, porosity, mean pore size, surface comPosition. and surface charge properties. The exerimental results show that the symmetric TiO2 membranes display better sintering activity in the air than in argon, and the mean pore diameters and porosities of the membrane sintered in argon are higher than those of the membrane sintered in the air at the same temperature. The surface compositions of the symmetric TiO2 membrane sintered in the air and in argon at different temperatures, as studied by X-ray photoelectron spectroscopy, are discussed in terms of their chemical composition, with particular emphasis on the valence state of the titanium ions. The correlation between the valence state of the titanium ions at the surface and the surface charge properties is examined.It is found that the presence of Ti^3＋, introduced at the surface of the symmetric TiO2 membranes by sintering in a lower partial pressure of oxygen, is related to a significant decrease in the isoelectric point. TiO2 with Ti^4＋ at the interface has an isoelectric point of 5.1, but the non-stoichiometric TiO2-x with Ti^3＋ at the interface has a lower isoelectric point of 3.6.

Microstructure-Property Relationship in Self-Crosslinked Non-Derivative Acetic Acid Lignin-Containing Polyurethane Membranes

With the assistance of different solvents, self-crosslinked acetic acid lignin-containing polyurethane (LPU) membranes were synthesized. Compared with tetrahydrofuran and dioxane, N, N-dimethylacetamide with stronger polarity together with higher boiling point was demonstrated to be beneficial for preparing LPU particles of smaller size and enhanced binding force. It was also found that lignin domain can interpenetrate into polyurethane domain well with 43.3% lignin addition, resulting in enhanced phase mixing and better performance. In addition, relative homogeneous and smooth LPU membrane can be obtained with 2% TMP addition, while stress crack took place when TMP content was greater than 3%.

燃料电池气体扩散层表面液相涌出行为

燃料电池流道内的两相分布特性对于提升燃料电池水管理能力至关重要,探究多液滴在流道表面流动行为利于优化结构及运行条件。使用流体体积(Volume of Fluid)法对液态水从气体扩散层(Gas diffusion layer)涌出到流道内的动态过程进行模拟,研究流道内气体流速、GDL表面接触角和水孔间距对水涌出过程和流动行为影响。结果表明,液滴在GDL表面经历了生长、分离、传输和碰撞凝并等过程。气体流速明显影响压降和液滴分离周期,随着气体流速增加,压降增加,液滴分离周期从14.7 ms降至4.7 ms,水去除能力显著增强,高气体流速造成液滴形态和流动情况不稳定。GDL表面润湿性改变了表面张力,影响液滴形态和流动,显著影响水覆盖率,随着接触角增大,GDL表面平均水覆盖率从20.03%降至9.01%;水孔间距对液滴碰撞周期影响大,小水孔间距时液滴在生长中发生凝并,大液滴飞溅造成流道内气流速度下降,压降和GDL表面水覆盖率产生大波动;大水孔间距时,流道内速度场受影响明显,前一液滴获得大速度后发生碰撞更易造成液滴飞溅,导致最大水孔间距时水覆盖率下降,从16.84%(D=0.8 cm)骤降至14.69(D=1.2 cm)。研究结果为流道表面接触角,GDL孔隙分布、进气条件等参数优化提供理论指导和技术借鉴,改善质子交换膜燃料电池水传输能力提高工作效率。

下调上皮内膜蛋白1抑制胶质母细胞瘤恶性生物学行为的实验研究

目的研究下调上皮内膜蛋白1(EMP1)对胶质母细胞瘤U251与U87细胞系增殖、侵袭、迁移、凋亡及U87细胞系荷瘤小鼠肿瘤体积及免疫组化指标的影响。方法采用siRNA干扰技术下调胶质母细胞瘤细胞系U87与U251中EMP1的表达。RT-qPCR和Western blot检测EMP1mRNA和蛋白的表达;CCK8和Transwell实验检测EMP1下调后肿瘤细胞增殖迁移及侵袭能力;流式细胞术检测EMP1下调后肿瘤细胞凋亡表达水平;构建U87细胞系裸鼠荷瘤模型,免疫组化法检测Ki-67和MMP2的表达。结果RT-qPCR和Western blot结果显示siRNA-EMP1导致EMP1的表达降低(P<0.05),CCK8和Transewll实验显示下调EMP1后肿瘤细胞的增殖、迁移及侵袭能力被显著抑制(P<0.05);流式细胞术结果显示下调EMP1后肿瘤细胞的凋亡能力明显增强(P<0.05);U87细胞系裸鼠荷瘤模型中下调EMP1后肿瘤细胞生长延缓,Ki-67及MMP2的表达降低。结论EMP1的表达下调可以抑制胶质母细胞瘤的增殖、迁移及侵袭,促进凋亡,延缓荷瘤小鼠肿瘤的生长与侵袭,从而抑制胶质母细胞瘤的恶性生物学行为。

载酶微球/聚乳酸复合纤维膜的制备及降解调控

为了调控聚乳酸纤维膜降解周期,制备了载酶微球/聚乳酸复合纤维膜,对不同载酶微球含量的复合纤维膜进行降解试验并测试复合膜在降解过程中的表面形貌、力学性能、化学结构、黏均相对分子量以及质量损失情况。结果表明:随着降解时间的增加,复合纤维膜表面逐渐粗糙并发生纤维断裂;力学性能、质量以及黏均相对分子量均逐渐下降;制得的复合纤维膜能够实现在20周~32周的降解调控,其中,载酶微球质量分数为2.5%的纤维膜在20周时基本完全降解。认为:在脂肪酶的作用下,载酶微球/聚乳酸复合纤维膜的降解速度逐渐加快,拓宽了医用聚乳酸纤维膜的应用范围。

油水膜分离中高黏度油滴行为研究和影响因素分析

膜法分离油田采出废水中的重油组分是膜污染的重要影响因素,且不同膜分离条件下膜面附近的复杂油滴行为直接影响膜分离效果,所以研究膜面附近的高黏度油滴行为十分必要。基于实际油田采出废水物性数据的实验测定结果,采用耗散粒子动力学(DPD)方法结合高黏度油滴轨迹和油滴间相互作用能结果对油滴行为进行细化分析。结果表明,双油滴呈现掠过和聚并两大类行为,又可各分为三个行为阶段:油滴间排液、油滴接触和油滴复稳;双油滴间距和油滴与膜面间距的减小有助于油滴聚并,从而有利于油水分离,且油滴与膜面间距的减小会导致油滴碰撞后的位置更远离膜面;表面活性剂的存在阻碍油滴聚并,不利于油水分离,且离子型表面活性剂因其亲水头间的强排斥力而阻碍作用更强;第3油滴的存在会促进双油滴聚并,有利于油水分离,其促聚并程度受油滴碰撞角的影响。研究结果可为后续的油滴与分离膜相互作用及油水分离效果的研究提供依据,也可为油水膜分离条件的设置和技术优化提供理论支持。

Mass transfer characteristics of chiral pharmaceuticals on membrane used for polar organic chemical integrative sampler

Passive sampling technology has good application prospects for monitoring trace pollutants in aquatic environments.Further research on the sampling mechanism of this technology is essential to improve the measurement accuracy and extend the application scope of this approach.In this study,adsorption and permeation experiments were performed to investigate the sorption and mass transfer properties of five chiral pharmaceuticals at the enantiomeric level on polyethersulfone(PES)and polytetrafluoroethylene(PTFE)membranes used in a polar organic chemical integrative sampler.Batch adsorption experiments showed that the PES membrane had an adsorption phenomenon for most selected pollutants and an insignificant sorption behavior was observed for all selected pharmaceuticals on the PTFE membrane except for R(S)-fluoxetine.The diffusion coefficients of selected pharmaceuticals onto the PTFE membrane were approximately one order of magnitude higher than those onto the PES membrane.The permeation experiment indicated that under different hydraulic conditions,the change of the relative pollutant concentration through the PTFE membrane for the composite pollutant system was more obvious than that for the single pollutant system,and mass transfer hysteresis exists for both contaminant systems through PES membranes.Using the first-order equation or 3-component model to estimate the overall mass transfer coefficients,the results showed that the overall mass transfer coefficient values of pollutants in the composite pollutant system onto both membranes were higher than those in the single pollutant system.This parameter was mainly influenced by the synergistic effects of the multi-analyte interaction and diminished water boundary layers during the mass transfer process.

质子交换膜燃料电池密封系统热力耦合仿真研究

温度影响质子交换膜燃料电池(PEMFC)的密封性能和力学行为,因而影响其使用寿命和可靠性。为研究PEMFC在热力耦合下的密封性能和力学行为,建立PEMFC单电池和多电池结构的二维模型,研究密封系统在不同工作温度下的应力-应变分布,讨论橡胶密封圈压缩比、双极板错位和密封垫尺寸对PEMFC密封性能和力学性能的影响。结果表明:温度对密封圈的Mises应力和膜电极组件(MEA)框架接触压力有很大影响;在不同工作温度下单电池和多电池结构的密封性能相似,应力和接触压力分布差别也不大,因此单电池结构的研究结论可以推广到多电池结构;随着橡胶密封圈压缩比和密封圈尺寸的增加,燃料电池密封性能得到改善;而双极板错位会加剧MEA框架的变形;高应力区出现在橡胶密封圈的横截面内部,容易导致局部应力集中和密封失效。

Scaling Behaviors of Polymers on Lipid Membranes:Coupling of Polymer Chain Dynamics and Surface Thermal Fluctuations

Despite extensive researches on the motion of polymer chains on lipid membranes,the effect of membrane fluctuations on polymer chain dynamics remains poorly understood.Here we report single molecule tracking experiments that allow for comparable measurements of polymer chain diffusion dynamics on nanotubular and planar phospholipid membranes.We observe a super-diffusion behavior and no apparent chain-length-dependent mobility of polymer chains on nanotubular membranes,while a Brownian motion and apparent chain-lengthdependent mobility of polymer chains on planar membranes.We suggest the super-diffusion nature of polymer chains may be due to the thermal-fluctuations of lipid nanotubes,which can be described from a statistical thermodynamic phenomenon coupling of polymer chain dynamics and surface thermal fluctuations.We suggest that the existence of surface environment fluctuations should influence the dynamics of the adsorbed polymer chains.This study provides previously uncharacterized insights into polymer diffusion dynamics on thermal-fluctuating flexible surfaces,which is essential to understanding the effect of environment fluctuations on polymer chain behaviors.

Molecular dynamics simulation of water transport through graphene-based nanopores: Flow behavior and structure characteristics

The flow behavior of pressure-driven water infiltration through graphene-based slit nanopores has been studied by molecular simulation.The simulated flow rate is close to the experimental values,which demonstrates the reasonability of simulation results.Water molecules can spontaneously infiltrate into the nanopores,but an external driving force is generally required to pass through the whole pores.The exit of nanopore has a large obstruction on the water effusion.The flow velocity within the graphene nanochannels does not display monotonous dependence upon the pore width,indicating that the flow is related to the microscopic structures of water confined in the nanopores.Extensive structures of confined water are characterized in order to understand the flow behavior.This simulation improves the understanding of graphene-based nanofluidics,which helps in developing a new type of membrane separation technique.

认知行为护理在特发性膜性肾病患者中的应用效果

目的:探讨认知行为护理在特发性膜性肾病(IMN)患者中的应用效果。方法:选择2021年2月—2022年6月于无锡市人民医院诊治的136例IMN患者作为研究对象,根据随机数表法将患者分为对照组和观察组,各68例。对照组采用常规传统护理,观察组在对照组基础上采用认知行为护理。对比两组治疗依从性、临床疗效、认知能力、心理状态及护理满意度。结果:两组干预前认知能力、心理状态比较,差异无统计学意义(P>0.05);观察组干预后一般自我效能感量表(GSES)评分、90项症状自评量表(SCL-90)评分均优于对照组,差异有统计学意义(P<0.05)。观察组治疗依从性、临床疗效和护理总满意度均高于对照组,差异有统计学意义(P<0.05)。结论:认知行为护理可明显改善IMN患者的心理状态和认知能力,且能提高治疗依从性、临床疗效及护理满意度。

不同工艺类型的MBR膜污染行为解析

膜生物反应器(MBR)具有诸多优点,然而膜污染限制了MBR的广泛应用。从工艺类型来讲,水处理MBR工艺可分为好氧、厌氧和缺氧MBR。对于这三种类型的MBR,很少有关于其膜污染行为方面的直接比较。通过对比好氧和厌氧MBR在有机污染、无机污染、生物污染三方面的膜污染行为差异,阐明了造成不同膜污染的主要原因,同时对缺氧MBR的膜污染研究进行展望,为不同类型的MBR膜污染研究提供了理论依据。

模拟高放废物地质处置条件下锝在去离子水体系中的胶体行为

^(99)Tc是高放废物地质处置中重点关注的关键核素,深地质处置条件下其在地下水中的胶体行为对其迁移行为可能存在较大影响,亟需系统开展研究。本文在模拟高放废物地质处置的低氧和低浓(氧气含量小于5 ppm、^(99)Tc初始浓度10^(-9)~10^(-5) mol/L)条件下,首先探讨了用膜过滤法研究锝胶体行为的可行性,发现pH值和离子强度等对^(99)Tc的液闪测定无明显影响,且过滤器对Tc(Ⅳ)和Tc(Ⅶ)均无显著吸附行为,基于此初步建立了锝胶体行为研究的膜过滤实验方法,并采用该方法研究了去离子水体系中锝的胶体行为。结果表明:Tc(Ⅶ)不易发生水解反应,在低氧条件下无明显胶体行为,并能长期稳定地存在于体系中,可能具有较强的迁移能力;Tc(Ⅳ)易水解而聚集为胶体,在较宽pH值范围内(pH=4~11)以真胶体形式在398 d实验周期内较长期地稳定存在于体系中,其浓度高于以离子形态存在的Tc(Ⅳ)的数倍甚至1个数量级,所形成的胶体可能会提高地质处置条件下Tc(Ⅳ)的迁移能力,但体系离子强度升高会使Tc(Ⅳ)胶体易凝聚为大颗粒物质甚至沉淀,导致锝以真胶体形态存在和迁移的可能性降低,因此高放废物处置中,锝胶体行为对其迁移行为的影响应予以足够重视和研究。

Thermo-responsive stick-slip behavior of advancing water contact angle on the surfaces of poly(N-isopropylacrylamide)-grafted polypropylene membranes

Wettability of a solid surface is highly important to its practical application,especially for the surface that shows thermoresponsive properties.In this paper,we describe a thermo-responsive stick-slip behavior of water droplets on the surfaces of poly(N-isopropylacrylamide)(PNIPAM)-grafted polypropylene membranes.Field emission scanning electron microscope(FESEM) images elucidate that the morphology of PNIPAM-grafted membrane surface is thermo-responsive,i.e.,the surface becomes rougher above the lower critical solution temperature(LCST) of PNIPAM.On the surface of nascent polypropylene membranes,the water droplet shows a smooth motion resulting in advancing and receding water contact angles of 111° and ～65°,respectively.On the PNIPAM-grafted membrane surfaces,the water droplet shows a stick-slip pattern above the LCST,whereas it advances smoothly below the LCST.This phenomenon is reproducible and can be ascribed to the energy barriers enhanced by the shrink of PNIPAM chains above the LCST.We also find that the slip contact angle decreases from 102° to 92° after several stick-slip cycles.This decrease is attributed to the water adsorption on the grafted PNIPAM layer,which is confirmed by the continuous decrease of the receding water contact angle.