Causes of epigastric pain and vomiting after laparoscopic-assisted radical right hemicolectomy-superior mesenteric artery syndrome

BACKGROUND Superior mesenteric artery syndrome(SMAS)is a rare condition causing functional obstruction of the third portion of the duodenum.Postoperative SMAS following laparoscopic-assisted radical right hemicolectomy is even less prevalent and can often be unrecognized by radiologists and clinicians.AIM To analyze the clinical features,risk factors,and prevention of SMAS after laparoscopic-assisted radical right hemicolectomy.METHODS We retrospectively analyzed clinical data of 256 patients undergoing laparoscopicassisted radical right hemicolectomy in the Affiliated Hospital of Southwest Medical University from January 2019 to May 2022.The occurrence of SMAS and its countermeasures were evaluated.Among the 256 patients,SMAS was confirmed in six patients(2.3%)by postoperative clinical presentation and imaging features.All six patients were examined by enhanced computed tomography(CT)before and after surgery.Patients who developed SMAS after surgery were used as the experimental group.A simple random sampling method was used to select 20 patients who underwent surgery at the same time but did not develop SMAS and received preoperative abdominal enhanced CT as the control group.The angle and distance between the superior mesenteric artery and abdominal aorta were measured before and after surgery in the experimental group and before surgery in the control group.The preoperative body mass index(BMI)of the experimental group and the control group was calculated.The type of lymphadenectomy and surgical approach in the experimental and control groups were recorded.The differences in angle and distance were compared preoperatively and postoperatively in the experimental group compared.The differences in angle,distance,BMI,type of lymphadenectomy and surgical approach between the experimental and control groups were compared,and the diagnostic efficacy of the significant parameters was assessed using receiver operating characteristic curves.RESULTS In the experimental group,the aortomesenteric angle and distance after surgery were significantly decreased than those before surgery(P<0.05).The aortomesenteric angle,distance and BMI were significantly higher in the control group than in the experimental(P<0.05).There was no significant difference in the type of lymphadenectomy and surgical approach between the two groups(P>0.05).CONCLUSION The small preoperative aortomesenteric angle and distance and low BMI may be important factors for the complication.Over-cleaning of lymph fatty tissues may also be associated with this complication.

Molecular dynamics simulation of the flow mechanism of shear-thinning fluids in a microchannel

Shear-thinning fluids have been widely used in microfluidic systems,but their internal flow mechanism is still unclear.Therefore,in this paper,molecular dynamics simulations are used to study the laminar flow of shear-thinning fluid in a microchannel.We validated the feasibility of our simulation method by evaluating the mean square displacement and Reynolds number of the solution layers.The results show that the change rule of the fluid system's velocity profile and interaction energy can reflect the shear-thinning characteristics of the fluids.The velocity profile resembles a top-hat shape,intensifying as the fluid's power law index decreases.The interaction energy between the wall and the fluid decreases gradually with increasing velocity,and a high concentration of non-Newtonian fluid reaches a plateau sooner.Moreover,the velocity profile of the fluid is related to the molecule number density distribution and their values are inversely proportional.By analyzing the radial distribution function,we found that the hydrogen bonds between solute and water molecules weaken with the increase in velocity.This observation offers an explanation for the shear-thinning phenomenon of the non-Newtonian flow from a micro perspective.

circRNA及其调控动物骨骼肌发育研究进展

环状RNA(circular RNA,circRNA)是一类反向剪接形成的闭合环状RNA分子,广泛存在于生物体内,近年来成为非编码RNA中的研究热点。骨骼肌在生物体中起到协调运动的作用,是维持体内正常代谢和内分泌的器官之一。随着测序技术和生物信息学分析技术的发展,circRNA在动物骨骼肌发育中的功能和调控机制逐渐被揭示。本文就当前circRNA的分子调控机制类型、circRNA经典研究思路及功能研究方法以及circRNA参与骨骼肌正常发育与骨骼肌疾病发生调控的研究进展进行了综述,以期为进一步深入研究circRNA参与骨骼肌生长发育调控的遗传机制以及circRNA相关研究方法提供参考。

Cellulose Nanopaper:Fabrication,Functionalization,and Applications

Cellulose nanopaper has shown great potential in diverse fields including optoelectronic devices,food packaging,biomedical application,and so forth,owing to their various advantages such as good flexibility,tunable light transmittance,high thermal stability,low thermal expansion coefficient,and superior mechanical properties.Herein,recent progress on the fabrication and applications of cellulose nanopaper is summarized and discussed based on the analyses of the latest studies.We begin with a brief introduction of the three types of nanocellulose:cellulose nanocrystals,cellulose nanofibrils and bacterial cellulose,recapitulating their differences in preparation and properties.Then,the main preparation methods of cellulose nanopaper including filtration method and casting method as well as the newly developed technology are systematically elaborated and compared.Furthermore,the advanced applications of cellulose nanopaper including energy storage,electronic devices,water treatment,and high-performance packaging materials were highlighted.Finally,the prospects and ongoing challenges of cellulose nanopaper were summarized.

Improving the stability and bioavailability of tea polyphenols by encapsulations:a review

Tea polyphenols(TPPs)have attracted significant research interest due to their health benefits.However,TPPs are sensitive to certain environmental and gastrointestinal conditions and their oral bioavailability was found to be very low.Delivery systems made of food-grade materials have been reported to improve the shelf-life,bioavailability and bioefficacy of TPPs.This review discusses the chemistry of TPPs;the setbacks of TPPs for application;and the strategies to counteract application limitations by rationally designing delivery systems.An overview of different formulations used to encapsulate TPPs is provided in this study,such as emulsion-based systems(liposome,nanoemulsion,double emulsion,and Pickering emulsion)and nano/microparticles-based systems(protein-based,carbohydrate-based,and bi-polymer based).In addition,the stability,bioavailability and bioactivities of encapsulated TPPs are evaluated by various in vitro and in vivo models.The current findings provide scientific insights in encapsulation approaches for the delivery of TPPs,which can be of great value to TPPs-fortified food products.Further explorations are needed for the encapsulated TPPs in terms of their applications in the real food industry as well as their biological fate and functional pathways in vivo.

Straw mulch-based no-tillage improves tillering capability of dryland wheat by reducing asymmetric competition between main stem and tillers

The moisture-conserving effect of straw mulch-based no-tillage(SMNT)is expected to increase fertile spikes and grain yield in environments with rainfall less than 200 mm.However,the mechanisms under-lying the positive effect of SMNT on wheat tillering are not fully elucidated.A split-plot experiment was designed to investigate the combined effects of SMNT and cultivars on tillering of dryland wheat grown under both dry and favorable climates.Application of SMNT to a cultivar with 1-2 tillers exploited both tillering and kernel-number plasticity,increasing the mean grain yield by 20.5%.This increase was attrib-uted primarily to an increased first-tiller emergence rate resulting from increased N uptake,leaf N con-tent,and N remobilization from tillers to their grain.The second and third tillers,as transient sinks,contributed to the tiller survival rate,which depends on tiller leaf number.The increased total N uptake by SMNT also increased the dry mass yield of tillers and the C:N ratio,reducing the asymmetric compe-tition between main stem and tillers.Owing to these beneficial effects,reduced mitogen-activated pro-tein kinase(MAPK)and abscisic acid signals were observed under SMNT,whereas indole-3-acetic acid(IAA)signals and genes involved in DNA replication and mismatch repair were increased.These signals activated three critical transcription factors(the calmodulin-binding transcription activator,GRAS domain,and cysteine-2/histidine-2 family)and further increased rapid drought response and tiller main-tenance after stem extension.Phenylpropanoid biosynthesis,sphingolipid biosynthesis,and galactose metabolism were most relevant to increased tillering under SMNT because of their critical role in drought response and lignin biosynthesis.Our results suggest that straw mulch-based no-tillage activates rapid drought response and improved wheat tillering by coordinating root N uptake,N remobilization,and asymmetric competition between main stem and tillers.

Laser-modified luminescence for optical data storage

The yearly growing quantities of dataflow create a desired requirement for advanced data storage methods.Luminescent materials,which possess adjustable parameters such as intensity,emission center,lifetime,polarization,etc.,can be used to enable multi-dimensional optical data storage(ODS)with higher capacity,longer lifetime and lower energy consumption.Multiplexed storage based on luminescent materials can be easily manipulated by lasers,and has been considered as a feasible option to break through the limits of ODS density.Substantial progresses in laser-modified luminescence based ODS have been made during the past decade.In this review,we recapitulated recent advancements in laser-modified luminescence based ODS,focusing on the defect-related regulation,nucleation,dissociation,photoreduction,ablation,etc.We conclude by discussing the current challenges in laser-modified luminescence based ODS and proposing the perspectives for future development.

The dynamic metabolic profile of Qi-Yu-San-Long decoction in rat urine using UPLC-QTOF-MS^(E) coupled with a post-targeted screening strategy

Qi-Yu-San-Long decoction(QYSLD)is a traditional Chinese medicine that has been clinically used in the treatment of non-small-cell lung cancer(NSCLC)for more than 20 years.However,to date,metabolicrelated studies on QYSLD have not been performed.In this study,a post-targeted screening strategy based on ultra-performance liquid chromatography coupled with quadrupole time-of-flight full information tandem mass spectrometry(UPLC-QTOF-MS^(E))was developed to identify QYSLD-related xenobiotics in rat urine.The chemical compound database of QYSLD constituents was established from previous research,and metabolites related to these compounds were predicted in combination with their possible metabolic pathways.The metabolites were identified by extracted ion chromatograms using predicted m/z values as well as retention time,excimer ions,and fragmentation behavior.Overall,85 QYSLD-related xenobiotics(20 prototype compounds and 65 metabolites)were characterized from rat urine.The main metabolic reactions and elimination features of QYSLD included oxidation,reduction,decarboxylation,hydrolysis,demethylation,glucuronidation,sulfation,methylation,deglycosylation,acetylation,and associated combination reactions.Of the identified molecules,14 prototype compounds and 58 metabolites were slowly eliminated,thus accumulating in vivo over an extended period,while five prototypes and two metabolites were present in vivo for a short duration.Furthermore,one prototype and five metabolites underwent the process of“appearing-disappearing-reappearing”in vivo.Overall,the metabolic profile and characteristics of QYSLD in rat urine were determined,which is useful in elucidating the active components of the decoction in vivo,thus providing the basis for studying its mechanism of action.

蚕丝丝肽嗜热栖热菌发酵液对皮肤抗炎抗衰功效的增效作用

为研究嗜热栖热菌发酵的蚕丝丝肽在皮肤抗炎抗衰功效上的增效作用,以脂多糖(LPS)诱导的角质形成细胞(HaCaT细胞)和双氧水(H2O2)诱导的成纤维细胞(HDF细胞)为研究模型,通过比色法、酶联免疫吸附(ELISA)等方法检测蚕丝丝肽、嗜热栖热菌发酵液和蚕丝丝肽发酵液对细胞活力、炎症因子白介素1β(IL-1β)和白介素6(IL-6)的含量、屏障保湿相关蛋白水通道蛋白3(AQP3)和丝聚蛋白(FLG)的含量、衰老相关标志物超氧化物歧化酶(SOD)、晚期糖基化终产物(AGEs)和人1型胶原蛋白(Col-1)的含量变化的影响。结果表明,蚕丝丝肽发酵液能够显著降低IL-1β,IL-6,AGEs含量,显著促进FLG,AQP3,SOD和Col-1表达,且相较于蚕丝丝肽能更显著抑制IL-6和AGEs表达,更显著促进HDF细胞迁移和SOD合成,而相较于嗜热栖热菌发酵液能更显著降低IL-1β,IL-6和AGEs表达,更显著促进AQP3表达、HDF细胞迁移和SOD的合成,即认为蚕丝丝肽发酵液相较于单一的蚕丝丝肽和嗜热栖热菌发酵液具备抗炎、屏障保湿及抗衰功效的增效作用。

5-Demethylnobiletin and its major metabolites:efficient preparation and mechanism of their anti-proliferation activity in HepG2 cells

5-Demethylnobile tin(5-DMN),a hydroxylated polymethoxyflavone(OH-PMF)identified in aged citrus peels,has demonstrated health benefiting effects in previous studies.5-DMN undergoes biotransformation in vivo,yielding 5,3’-didemethylnobiletin(5,3’-DDMN),5,4’-didemethylnobiletin(5,4’-DDMN)and5,3’,4’-tridemethylnobiletin(5,3’,4’-TDMN).However,the anti-cancer effects of 5-DMN and its in vivo metabolites against HepG2 cells remain unclear.In this study,an efficient chemical synthetic method was developed to obtain 5-DMN and its 3 metabolites,and their molecular structures were confirmed by;H NMR and LC-MS.Cytotoxicity,cell cycle arrestment,apoptosis and caspase-3 expression were investigated to evaluate the anti-liver cancer effects of these OH-PMFs on HepG2 cells.The results showed that all 4 compounds inhibited the proliferation of HepG2 cells in a concentration-dependent manner.Their anti-proliferative activity was exerted through inducing G2/M phase arrestment,cell apoptosis and promoting expression of a key apoptotic protein called cleaved caspase-3.Our results indicated that 5,3’-DDMN and5,3’,4’-TDMN showed a stronger inhibitory activity on cell proliferation than 5-DMN,followed by 5,4’-DDMN.The expression of cleaved caspase-3 was the highest in cells treated with 5,4’-DDMN,implying that the apoptosis induced by other OH-PMFs might be mediated by other apoptotic execution proteins.Our research reveals the application potential and scientific evidence for the production and functionality of OH-PMFs.

界面水分子扩散对超高分子量聚乙烯摩擦学性能影响的反应分子动力学模拟研究

采用基于反应力场(ReaxFF)的分子动力学模拟方法,研究了摩擦界面水分子向超高分子量聚乙烯(UHMWPE)基体扩散和渗透的基本过程.分子模拟结果表明:摩擦过程中,水分子稳定吸附在Fe板表面,并与聚乙烯链形成分子内摩擦,使聚乙烯分子产生剪切变形.当Fe板表面存在纳尺度外凸结构时,其在UHMWPE表面的耕犁作用更为显著,使摩擦界面的内摩擦力显著增加.当摩擦速度增加时,摩擦界面原子温度显著升高.在水润滑条件下,界面水分子逐渐扩散到UHMWPE基体中,引起相邻聚乙烯链之间的原子距离增加,这导致聚乙烯链之间的相互作用强度降低.此外,摩擦界面处还伴随着水分子中氢氧键断裂,并引起相应原子的电荷跃变.此时,水氧原子与Fe原子形成Fe―O化合物,且具有与Fe2O3相似的晶体结构.水分子扩散进入UHMWPE内时,还引起其周围聚乙烯分子的电荷发生改变,造成UHMWPE表层原子电荷分布不均匀.

多维协同效应诱导的高压电性及可靠性的KNN压电陶瓷应用于高频超声换能器

高频超声换能器已成为现代医学诊断和治疗的有力工具.目前,大多数超声换能器使用压电陶瓷进行机电耦合,在高频(>20 MHz)下会发生周期性的电声转换,因此对材料可靠性要求较高.本文提出了一种结构调控策略,以提高铌酸钾钠(KNN)基无铅陶瓷的压电性与可靠性,并用于高频超声成像.该KNN基陶瓷具有增强的压电性(d33~550±20 pC N^(-1))及抗疲劳特性,同时针对其良好性能,我们从涉及宏观到微观的多项共存、完好微观结构与灵活畴翻转的多维度协同效应阐述其机理.该多维度协同效应抑制了疲劳过程中性能恶化裂纹的出现及空间电荷的聚集,从而减少了畴壁的钉扎,增强了抗疲劳性.此外,基于该高性能压电陶瓷制备的超声换能器具有高可靠性及温度稳定性(从室温到80℃,频带宽度几乎不变).我们利用该超声换能器扫描罗非鱼眼球结构测试了器件成像效果.相信通过结构策略实现性能提升的新方法可以促进KNN基超声器件在生物医学方面的应用.

Synergy of lead vacancies and morphotropic phase boundary to promote high piezoelectricity and temperature stability of PBZTN ceramics

The flourishing development of emerging electromechanical applications has stimulated an urgent demand for ferroelectric ceramics with high piezoelectric properties and broad temperature usage range.However,it remains a challenge to simultaneously obtain good piezoelectricity and reliable temperature stability in lead zirconate titanate(PZT)-based piezoelectric ceramics.To solve this issue,a synergetic strategy was proposed to introduce lead vacancies through niobium doping and construct morphotropic phase boundary(MPB).In this work,Pb_(0.905)Ba_(0.085)(V Pb″)_(0.01)[(Zr_(x)Ti_(1-x))_(0.98)Nb_(0.02)]O_(3)(PBZTN-x)material system was designed.Good comprehensive properties(d_(33)=864 pC/N,k_(p)=84%,T_(C)=201℃)and excellent temperature stability(less than 10%variation of electrical properties from 20℃ to 160℃)were obtained in PBZTN-0.540 ceramics.Good piezoelectricity can be attributed to high extrinsic contribution(domain wall motion)induced by Pb^(2+)vacancies and the existence of nano-domains emerged at MPB,while excellent temperature stability is mainly attributed to the minimized local stress in the lattice and the stable domain structure.

Cation-anion synergetic interactions achieving tunable birefringence in quasi-one-dimensional antimony(Ⅲ)fluoride oxalates

Birefringent materials with large optical anisotropy,which can be used to modulate the polarization of light,play a key role in laser techniques and science.However,the exploration studies of new,superior birefringent materials develop extremely slowly due to the lack of effective guidelines for rational design.Herein,three antimony(Ⅲ)fluoride oxalates,namely,Na_(2)Sb_(2)(C_(2)O_(4))F_(6),K_(2)Sb_(2)(C_(2)O_(4))F_(6),and Cs_(2)Sb_(2)-(C_(2)O_(4))_(2)F_(4)·H_(2)O,were successfully synthesized through a rational combination ofπ-conjugated C_(2)O_(4)^(2-)anions and Sb^(3+)cations with stereochemically active lone pairs.These oxalates feature unique quasi-one-dimensional chain structures that induce large optical anisotropy.Remarkably,Cs_(2)Sb_(2)(C_(2)O_(4))_(2)-F_(4)·H_(2)O exhibits the largest birefringence(0.325@546 nm)among all reported antimony(Ⅲ)-based oxysalts.Detailed structural analysis and theoretical calculations confirmed that the optical anisotropy of these oxalates could be tuned through the synergetic interactions of templated cations and anionic functional groups.This work may open the door to efficiently designing excellent birefringent materials and guide the further discovery of other novel structure-driven functional materials.

Multiscale Structure Engineering for High-Performance Pb-Free Piezoceramics

CONSPECTUS:The increasing world energy crisis drives humans to harvest the energy in nature as much as possible without heavily damaging the environment.However,most of the energy in nature cannot be used directly.Therefore,pursuing technologies or matter that can directly interconvert different energies has been one of the most cutting-edge fields in science and technology.Such a magic ability exists in true-life piezoelectric materials that generate charge when being given a force and vice versa,rendering them highly promising for energy harvesting and conversion because of the tremendous mechanical energy on the earth,such as tide energy.Thus,piezoelectric materials,represented by the lead zirconate titanate(Pb(Zr,Ti)O_(3),PZT)family,have been largely used in various traditional and burgeoning fields,such as electronic information,biomedical treatment,and wearable flexible electronic devices,and are one of the most important favorites in multidisciplinary fields.However,Pb is highly toxic.Driven by environmental protection and concern for human health,Pb-free piezoceramics are rapidly being developed to hopefully replace Pb-based ones.In particular,the renewal of Restriction of the use of certain Hazardous Substances(e.g.,RoHS 2),issued by the European Union,declared that replacement of PZT“...may be scientif ically and technologically practical to a certain degree...”.Therefore,developing high-performance Pb-free piezoceramics has become more urgent than ever.In this context,some Pb-free piezoceramics,represented by potassium sodium niobate((K,Na)NbO_(3),KNN),barium titanate(BaTiO_(3),BT),bismuth barium titanate((Bi,Na)TiO_(3),BNT),and bismuth ferrite(BiFeO_(3),BFO),stand out because of their unique or similar traits.However,several key challenges,including an inferior overall performance compared to Pb-based counterparts and an unclear structure−property relationship from multiscale viewpoints,have severely hindered the development of Pb-free piezoceramics for a long time.Pb-based piezoceramics possess decent performance due to the strategy of phase boundary engineering,which inspired the researchers to pursue it in Pb-free counterparts.In the last 10 years,our group has been aiming at the new phase boundary(NPB)and new physical phenomenon in Pb-free piezoceramics.This Account presents our recent contributions to the development of Pbfree piezoceramics concerning the good performance and emerging phenomenon.First,we introduce the construction of the NPB in KNN-based piezoceramics by emphasizing the role of some key elements(i.e.,Bi,Sb,Zr,and Hf).Then,we summarize the effects of the NPB on KNN-and BT-based ceramics and the new physical phenomenon in BNT-based ceramics.The NPB boosts the piezoelectric properties and temperature stability of KNN-and BT-based piezoceramics,comparable to some Pb-based piezoceramics.Combining the NPB and the multilayer ceramics substantially enhances the temperature stability of the piezoelectric constant.A new physical phenomenon of the nanoscale bubble domains with polar topologies is for the first time revealed in BNTbased ceramics,showing potential applications for nonconventional and high-density nonvolatile memories.In particular,we emphasize structure engineering from multiscale viewpoints including the local,microscopic,mesoscopic,and macroscopic structure(e.g.,lattice structure,ferroelectric domains,and phase structure).Finally,we provide perspectives on the future developments of Pb-free piezoceramics toward practical applications.

Progress on the doping and phase boundary design of potassium–sodium niobate lead-free ceramics

Potassium–sodium niobate(K,Na)NbO3/(KNN)lead-free ceramics have drawn vast amount of attention as one of the effective alternatives to lead-based ones.In recent years,the author’s group concentrated their work on KNN-based ceramics.This paper reviews the main obtained results in authors’laboratory on how to enhance the piezoelectric properties of KNN-based ceramics,including the ions or compounds substitution,the constructing and types of phase boundaries near room temperature,the investigation of other tools(sintering aids,synthesis technique,poling conditions)on properties.All the published papers up to now show the developing higher performance with maintaining high Curie temperature of KNN-based ceramics which has great potential for the future and is the key to success for the field.

Sealing performance and mechanical response of mud pump piston

In order to explore the effect of piston cup structure on its sealing characteristics and mechanical properties,a numerical simulation model of the piston cup in the BW-160 mud pump was established.Effects of work load,friction coefficient and cup structure parameters on the sealing and mechanical properties of the piston were discussed under mud discharge condition.The results show that stress concentration on the root and lips of the cup is becoming more and more obvious with the working load increases.The average contact pressure increases with the friction coefficient increases,but an excessive friction coefficient accelerate the wear of the cup and the heat generation.Effect of the piston lip interference and thickness on the sealing performance of the cup is greater than that of the inner wall width.The piston with groove structure can effectively improve the sealing performance of the piston.The mechanical properties of triangular groove cup are better than that of semicircular and trapezoidal groove cup.

Three-dimensional printed tissue engineered bone for canine mandibular defects

Background:Three-dimensional(3D)printed tissue engineered bone was used to repair the bone tissue defects in the oral and maxillofacial(OMF)region of experimental dogs.Material and methods:Canine bone marrow stromal cells(BMSCs)were obtained from 9 male Beagle dogs and in vitro cultured for osteogenic differentiation.The OMF region was scanned for 3D printed surgical guide plate and mold by ProJet1200 high-precision printer using implant materials followed sintering at 1250℃.The tissue engineered bones was co-cultured with BASCs for 2 or 8 d.The cell scaffold composite was placed in the defects and fixed in 9 dogs in 3 groups.Postoperative CT and/or micro-CT scans were performed to observe the osteogenesis and material degradation.Results:BMSCs were cultured with osteogenic differentiation in the second generation(P2).The nanoporous hydroxyapatite implant was made using the 3D printing mold with the white porous structure and the hard texture.BMSCs with osteogenic induction were densely covered with the surface of the material after co-culture and ECM was secreted to form calcium-like crystal nodules.The effect of the tissue engineered bone on the in vivo osteogenesis ability was no significant difference between 2 d and 8 d of the compositing time.Conclusions:The tissue-engineered bone was constructed by 3D printing mold and hightemperature sintering to produce nanoporous hydroxyapatite scaffolds,which repair in situ bone defects in experimental dogs.The time of compositing for tissue engineered bone was reduced from 8 d to 2 d without the in vivo effect.

Open-cell mullite ceramic foams derived from porous geopolymer precursors with tailored porosity

Porous geopolymer precursors were firstly prepared by the direct foaming method using bauxite,fly ash(FA),and metakaolin(MK)as raw materials,and porous mullite ceramics were prepared after ammonium ion exchange and then high-temperature sintering.The effects of chemical foaming agent concentration,ion-exchange time,and sintering temperature on porous geopolymerderived mullite ceramics were studied,and the optimal preparation parameters were found.Studies have shown that the concentration of blowing agent had great influence on open porosity(q)and porosity and cell size distributions of geopolymer samples,which in turn affected their compressive strength(σ).Duration of the ion exchange had no obvious effect on the sintered samples,and the amount of mullite phase increased with the increase in the sintering temperature.Mullite foams,possessing an open-celled porous structure,closely resembling that of the starting porous geopolymers produced by directly foaming,were obtained by firing at high temperatures.Stable mullite(3Al_(2)O_(3)·2SiO_(2))ceramic foams with total porosity(ε)of 83.52 vol%,high open porosity of 83.23 vol%,and compressive strength of 1.72 MPa were produced after sintering at 1400 for 2 h in℃ air without adding any sintering additives using commercial MK,bauxite,and FA as raw materials.

魔芋葡甘聚糖水合层承载及润滑机理的分子动力学模拟

魔芋葡甘聚糖(KGM)溶液具有优良的承载和润滑能力,为研究其微观作用机理,采用分子动力学模拟的方法,阐明了魔芋葡甘聚糖水合层的形成过程,探讨其在模拟工况下(压力范围:0~1000 MPa、剪切速度范围:0.02~1 nm/ps)的承载能力及剪切特性,揭示了其润滑机理.模拟结果表明,魔芋葡甘聚糖分子与水分子通过氢键形成水合分子,由于吸附效应,水合分子向铁原子层表面吸附聚集构成水合层作为承压载体;在剪切作用下,界面处吸附的魔芋葡甘聚糖水合分子层削弱了水分子与铁原子层的相互作用,从而降低界面剪切应力;魔芋葡甘聚糖分子数过多时,液相层中间部位的魔芋葡甘聚糖浓度增加,造成其周围液相层流动阻力增大,导致界面剪切应力增大.随着剪切速度的增加,KGM与水分子间的氢键随之减弱,从而削弱了KGM水合分子对水分子的约束,导致界面剪切应力随剪切速度的增大而增大.