Effect of homogenization treatment on microstructure evolution and the distributions of RE and Zr elements in various MgeLieREeZr alloys

Mge3Lie0.4Zr alloys containing RE elements(Gd,La,Nd)(Mge3LieREe0.4Zr alloys)are investigated to reveal the influence of homogenization treatment on microstructures and distributions of RE,Zr elements.It is found that 300
C24 h homogenization treatment shows better improvement on the microstructure including the refinement of grain size,the dispersion of cellular dendrite and low melting point particles.Before treatment,La and Nd segregate effectively at grain boundary and Zr segregates in the form of precipitates.Homogenization treatment induces the reduction of RE segregation.However,the segregation of Zr in precipitates cannot be abated due to the relatively low diffusion rate compared with RE elements.

Microstructural Characteristic of Montmorillonite and Its Thermal Treatment Products

The montmorillonite was studied by differen t methods, such as chemical analysis, DAT, TG, X RD, IR, AFM and MAS NMR. The experimental results show that the hydroxyl in octa hedra sheets begins dehydrating when the thermal treatment temperature reaches 659℃, but th e layer structure remains the same,and the corresponding Al(Ⅵ) is turned into Al(Ⅳ) in octahedra sheets. When the temperature reaches 900℃, the layer struct ure of montmorillontite is destroyed, and the new mineral phase μ-cordierite i s found. When the temperature reaches 1200℃, the μ-cordierite phase loses its stability, and decomposes into cristobalite phase and mullite phase.Meanwhile, the recrystallization phenomenon in thermal treatment products is obvious. There is a small quantity of Al Ⅵ signal in MAS NMR spectrum, corresponding to Al of mullite. When the temperature reaches 1350℃, the cristobalite and mullite phases reduce slightly, and more Fe-cordierite phase appears, corresponding to Fe-cordierite spectrum in XRD and MAS NMR.

INFLUENCES OF MICRO-ALLOY AND HEAT-TREATMENT PROCEDURE ON THE HARDENING OF DJ108TI ALLOY

The influences of micro alloy and heat treatment procedure on the hardening of DJ108Ti alloy, which is based on the electrolytic Al Si(2 05%) Ti(0 25%) Fe(0 30%) multi component alloy, have been investigated. The results indicate that the micro alloy based on the multi component alloy makes α Al dendrites in DJ108Ti alloy refined; that the improved heat treatment procedure makes the eutectic Si phases granulated , the Fe phase refined, and the strengthening phases of Mg2Si and Al2Cu fully precipitated. The micro alloy and the heat treatment procedure harden DJ108Ti alloy and benefit the abrasion resistance of the alloy

Influence of vacuum heat treatment on structure and micro-hardness of electroless Ni-P-SiC composite coating

The electroless Ni-P-SiC composite coatings were prepared and the influence of vacuum heat treatment on its structure and properties was analyzed. The Ni-P-SiC composite coatings were characterized by morphology,structure and micro-hardness. The morphology and structure of the Ni-P-SiC composite coatings were studied by scanning electron microscopy(SEM) and X-ray diffractometry(XRD),respectively. A great deal of particles incorporation and uniform distribution were found in Ni-P-SiC composite coatings. XRD results show a broad peak of nickel and low intensity SiC peaks present on as-deposited condition. Micro-hardness of as-deposited Ni-P-SiC composite coatings is improved greatly,and the best micro-hardness is obtained after heat treatment in a high vacuum at 400 ℃ .

Quick Surface Treatment of AZ31B by AC Micro-arc Oxidation

In order to explore an effective way to shorten treatment time and enhance the quality of treatment coating, AC micro-arc oxidation was conducted to treat the surface of AZ31 B deformation magnesium alloy in KF＋KOH treatment solution. The infl uences of micro-arc oxidation parameters such as concentration of KF, concentration of KOH, output voltage of booster, temperature of treatment solution, and treatment time on treatment coating thickness were raveled out under different conditions. The structure and composition of treatment coating were determined, the growth mechanism of treatment coating was discussed, and the quick surface treatment technology for compact treatment coating with maximum thickness was developed. The experimental results show that： A maximum 33 μm-thick compact treatment coating, consisting of MgF2 and MgO mainly, can be formed on AZ31 B in 112 s under the conditions of 1 132 g/L KF, 382 g/L KOH, 66 V for output voltage of booster and 34 ℃ of treatment solution which were optimized by a genetic algorithm from the model established by artifi cial neural networks. There are no ＂crater-shaped＂ pores in this treatment coating as the heat shock resulting from the smooth variation of AC sinusoidal voltage is far smaller than that of the rigidly varied DC or pulse current. The treatment time is only one sixth of that adopted in the other surface treatment technology at best, principally for the reason that the coating can always grow irrespective of the electric potential of AZ31 B. This investigation lays a fi rm foundation for the extensive application of magnesium alloy.

基于micro-CT评估3种去龋方法清除龋损组织效果及微创潜力的研究

目的使用微型计算机断层扫描(micro-computerized tomography,micro-CT)评价传统球钻去龋法、去腐凝胶辅助去龋法和龋显像笔辅助去龋法的清除龋损组织效果和微创潜力。方法本研究已获得医院生物医学研究伦理委员会审批及患者知情同意。收集30颗有牙本质龋的磨牙或前磨牙,随机分为3组,分别使用传统球钻去龋法(传统球钻组)、去腐凝胶去龋法(去腐凝胶组)和龋显像笔去龋法(龋显像笔组)对样本进行去龋处理,并记录每个样本的去龋操作时间,去龋前后均使用micro-CT进行扫描并记录每颗牙齿的龋损及健康牙体体积。根据去龋前后的龋损体积及去龋前后的健康牙体体积分别评估3种去龋方法的清除龋损组织效果、微创潜能。结果在去龋时间方面,去腐凝胶组所用时间(501.7±143.6)s高于传统球钻组(263.9±121.2)s和龋显像笔组(284.2±135.6)s,差异具有统计学意义(P<0.01);传统球钻组和龋显像笔组差异无统计学意义。在清除龋损组织效果方面,残余龋损体积与初始龋损体积的比值传统球钻组(0.087±0.04)最低,去腐凝胶组(0.51±0.10)最高,龋显像笔组(0.36±0.10)介于前两组之间,差异有统计学意义(P<0.01)。在微创潜能方面,去龋前后健康牙体体积比值传统球钻组(0.87±0.05)低于去腐凝胶组(0.99±0.01)和龋显像笔组(0.98±0.01),差异有统计学意义(P<0.01);去腐凝胶组和龋显像笔组差异无统计学意义。结论传统球钻组操作时间最短,但会过多去除健康牙本质和脱矿牙本质,微创潜能最差。去腐凝胶组可保留脱矿牙本质和全部健康牙本质,微创潜能最好,但清除龋损组织效果不佳,操作时间较长。龋显像笔组可以保留部分脱矿牙本质和健康牙本质,具有一定微创潜力,临床操作时间适中。

不同相主牙胶尖对根尖区三维封闭的Micro CT观察

目的观察α相与β相主牙胶尖在热垂直加压充填法中对根尖区的三维封闭作用。方法实验筛选出根尖区4mm具有侧支根管或根尖分歧的下颌第一前磨牙20颗,以镍钛根管锉Prota Per冠向下法预备至F3,将20例样本随机分为2组,分别采用α相牙胶与β相牙胶,以热垂直加压根管充填技术进行根管充填。充填完成前、后采用微计算机断层扫描技术对根尖区4mm容积进行扫描及三维重建,计算根尖区4mm充填程度即充填后容积与充填前容积之比,观察2种不同相的主牙胶尖对根尖区的封闭效果。结果 2种牙胶的根尖区充填程度均在81%以上,α相牙胶组在根尖区的充填程度与β相牙胶组差异无统计学意义。结论α相牙胶组与β相牙胶组均对根尖区有良好的三维封闭效果,二者无显著性差异。

Micro-CT三维重建技术在根管治疗研究中的应用

熟悉根管系统的解剖形态特征、彻底的根管预备和严密的根管充填是根管治疗成功的重要保障。随着医学影像学技术的发展,三维影像重建技术已广泛应用于根管形态学、根管预备效果、根管充填质量、根管再治疗效率、三维有限元力学等相关研究。通过不同角度和层面观察和定性定量地分析三维重建后的根管三维图像,了解根管解剖形态,评价根管治疗各个环节的操作效果,对于临床操作具有重要的指导意义。本文就基于Mirco-CT的三维重建技术在根管解剖形态、根管预备、根管充填、根管再治疗效率以及三维有限元力学等研究中的应用作一综述。文献综述结果表明,Micro-CT分辨率高,Micro-CT扫描三维重建后的立体影像能精确地显示根管的细微解剖形态;准确测算根管预备前后的根管体积和形态变化、根管充填后的空隙发生率和空隙体积;准确计算根管再治疗前后根管充填材料的体积变化,是目前根管系统形态学研究和评价根管预备和充填质量的金标准。Micro-CT扫描三维重建后,可建立三维有限元模型,模拟根管治疗的过程并进行应力分析,分析根管治疗器械应力分布和根管预备对牙体组织应力的影响、根管充填过程中根管壁的应力分布等,从而筛选合适的操作方法、预防器械折断及牙根的折裂。Micro-CT三维重建技术在根管形态及根管治疗评价中具有重要价值。

MicroRNA在非小细胞肺癌的诊断、治疗和预后评估中的作用

肺癌是最常见的恶性肿瘤之一,居全球癌症死亡的首位。肺癌预后差的原因是缺乏有效的早期诊断方法及治疗手段。微小核糖核酸（Micro RNA,miRNA）是一种大小为18~23个碱基的非编码单链小分子RNA。近年研究发现,miRNA在肺癌的发生发展发挥着重要作用。本文对miRNA在非小细胞肺癌的诊断、治疗和预后判断中的作用做一综述。

外泌体中microRNAs在神经胶质瘤中的研究进展

外泌体是一种膜源性囊泡,在尿液、精液、血液、眼泪、淋巴液、脑脊液等体液中稳定存在。在电子显微镜下,它们呈杯状或碟状。一般尺寸在25~100 nm左右。人体内的各种细胞可以释放不同类型的外泌体,其中包含microRNA、mRNA、蛋白质和其他遗传物质,其在细胞通讯中起重要作用,尤其是在调控细胞的生长,构建细胞生长环境等方面。本文针对外泌体中的microRNA在胶质瘤的相关方面进行总结。

Reduction of Residual Stress in Low Alloy Steel with Magnetic Treatment in Different Directions

The behavior that different magnetic treatment directions induce various amounts of welding residual stress reductions in low alloy steel was studied. Reductions of 26%-28% in the longitudinal stress σ x were obtained when low frequency alternating magnetic treatment was applied perpendicularly to the welding bead, whereas reductions of 20%-21% in σ x were measured by using the same treatment parameters except that the field direction was applied parallel to the bead. It is proposed that different extent of stress reductions caused by the above two treatment directions is attributed primarily to the alteration of the energy absorbed by domains from the external magnetic field, which part of energy can arouse plastic deformation in microstructures by the motion of domain walls.

利用Micro CT技术进行微创根管治疗方法的体外实验研究

目的确定利用Micro CT技术进行恒磨牙根管口面定位、保留髓顶的微创根管治疗方法的可行性。方法选择恒磨牙100颗,随机配对分为2组;实验组通过Micro CT技术定位根管口在咬合面投影,微孔开髓,进行保留髓顶的根管治疗,对照组常规行揭髓顶根管治疗;卡方检验根管充填密合性、操作时间和咬合面硬组织损耗面积。结果 2种根管治疗方法在根管充填密合性、操作时间上没有明显差异,但利用Micro CT技术进行恒磨牙定位确定保留髓顶根管治疗方法可显著减少牙体面硬组织的去除。结论利用Micro CT技术进行恒磨牙根管口定位,从而开展保留髓顶的根管治疗方法具有可行性,利于保存更多健康牙体组织。

基于气体吸附法和X射线Micro-CT三维成像技术定量解析天然和电化学处理绿松石孔隙特征

绿松石是一种多孔材料,其孔隙特征直接影响其颜色、光泽、硬度、耐久性等性质,进而影响其市场价值,电化学处理的主要目的是降低绿松石孔隙度从而使其耐久、保色。采用全自动比表面仪、X射线显微CT(Micro-CT)等测试分析手段,对电化学处理前后绿松石的孔隙特征进行了对比研究。比表面仪研究发现,电化学处理后的绿松石总孔隙度、总孔体积、平均孔径及比表面积均有一定程度的变化;吸附-脱附曲线高压区域天然绿松石吸附曲线斜率变大,而电化学处理绿松石吸附曲线斜率变小;天然绿松石孔径分布曲线为类抛物线,而电化学处理绿松石孔径分布曲线呈内凹曲线状。Micro-CT研究结果表明:天然绿松石中出现的由表面贯穿至内部的大孔洞,经电化学处理后孔洞被不完全充填;天然绿松石存在"流纹状"结构,孔隙沿"流纹"分布,而电化学处理绿松石的"流纹状"结构消失,孔隙分布杂乱无章。本研究首次从孔隙特征角度入手,发现天然绿松石与电化学处理绿松石在高压区域吸附曲线特征、50nm孔径以上孔隙分布曲线、孔隙充填情况和内部结构等方面存在明显差异。通过检测绿松石的钾(K)含量,并结合孔隙特征差异,可以有效地对绿松石是否经过电化学处理进行检验判定。

Osteoblast Behavior on Hierarchical Micro-/Nano-Structured Titanium Surface

In the present work, osteoblast behavior on a hierarchical micro-/nano-structured titanium surface was investigated. A hi- erarchical hybrid micro-/nano-structured titanium surface topography was produced via Electrolytic Etching （EE）. MG-63 cells were cultured on disks for 2 h to 7 days. The osteoblast response to the hierarchical hybrid micro-/nano-structured titanium surface was evaluated through the osteoblast cell morphology, attachment and proliferation. For comparison, MG-63 cells were also cultured on Sandblasted and Acid-etched （SEA） as well as Machined （M） surfaces respectively. The results show signifi- cant differences in the adhesion rates and proliferation levels of MG-63 cells on EE, SLA, and M surfaces. Both adhesion rate and proliferation level on EE surface are higher than those on SLA and M surfaces. Therefore, we may expect that, comparing with SLA and M surfaces, bone growth on EE surface could be accelerated and bone formation could be promoted at an early stage, which could be applied in the clinical practices for immediate and early-stage loadings.

Effect of Heat Treatment on the Mechanical Properties of FeCoZrWB Bulk Metallic Glass

A Fe61Co10Zr5W4B20 bulk metallic glass （BMG） with a diameter of 2 mm was prepared by using copper mould suction casting. The X-ray diffraction （XRD）, differential scanning calorimetry （DSC）, micro-hardness and compression tests were adopted to investigate the structure, thermal stability, especially, the effect of heat treatment on the micro-hardness and compression strength of this BMG. The BMG exhibits micro-hardness of about 1 207 Hv and compression fracture strength of about 1 707.6 MPa. After being annealed below the onset of crystallization temperature, the micro-hardness almost keeps constant. But after being annealed above the peak of crystallization temperature, the micro-hardness increases firstly and then declines gradually with the elongation of annealing time. However, annealed for the same period of time, the micro-hardness will increase with the rise of annealing temperature, while the compression fracture strength will apparently decrease.

The Flow Behavior of Red Blood Cell Reduced Deformability in Microchannel

Blood cells are mainly(~99%)comprised of red blood cells.The most remarkable properties of are their high deformability,which allow they flow through microcapillaries of diameter even smaller than their size.The RBC’s remarkable mechanical properties originate from the unique architecture of its membrane.To study the mechanism of RBC’s deformability,a commonly adopted approach is to localize the cytoskeleton protein by immunofluorescence,followed by exploring the changes of cytoskeleton protein during cell deformation.During this process,the fixed treatment of RBC using GA and PFA is of great importance.However,RBC’s deformability is reduced by the fixation process and skeletal protein of membrane is changed accordingly.The flow behavior of red RBCs through the microchannel also changed.Given the difficulty of observing RBC flow in vivo,in vitro simulation by virtue of microfluidic devices provides a feasible alternative.An important physiological phenomenon of the blood flow is the formation of cell free layer(CFL),with RBCs show a tendency to concentrate towards the central axis of the pipeline and move faster than the plasma layer.However,this phenomena is weaken if the stiffness of the membrane increase,which occurs in some disease,such as hereditary spherocytosis and hereditary elliptocytosis.To study the effects of GA and PFA fix treatment on RBC deformability,a microfluidic platform is employed to measuring the CFL and flow velocity of blood flow in this work.The PDMS micro flow channel used is 100 micrometers in width and 50 micrometers in deep.The RBC suspension is fed into the flow channel by the injection pump(NE-1000.USA),and the experiments are observed and recorded by the inverted microscope(IX70,Olympus,Japan)and high-speed camera(Memrecam GX-1,NAC,Japan)system.Three GA concentrations,i.e.,0.000 5,0.000 75,and 0.001 wt.%were used.Meanwhile,the effect of PFA at a concentration of 2wt.%work with GA was also investigated.Images of the flowing RBCs are processed mainly based on Memrecam GXLink.The results show that,the diameter of the RBC be treated is bigger and the shape of the RBC is became more flat after treated.Some of RBCs lost their biconcave structure.When the RBC suspension with 5%Hct flow in the microchannel,the CFL thickness decrease after being treated.And with concentrations of GA increase,the CFL thickness become thinner.The CFL thickness decrease significantly when GA and 2 wt.%PFA work combined.The velocity of RBCs decreases after treated with the GA or/and 2wt.%PFA.GA is known to relieve the dissolution of red blood cells during fluorescence labeling.On the other hand,the crosslinking of the aldehyde group(-cho)of GA with the amino group(-nh2)of RBC membrane protein will change the conformation of the membrane protein and its visco-elastic properties in turn.Then,the transparent fluidity orrheology characteristics of RBC is altered.Since GA and PFA are commonly used to immobilize red blood cells and keep the fluorescence constant,and PFA works similarly as GA,as a result,the variation of membrane protein conformation is intensified,and the membrane becomes stiffer.

Degradation of Nitrobenzene Wastewater via Iron/Carbon Micro-electrolysis Enhanced by Ultrasound Coupled with Hydrogen Peroxide

The zero valent iron/granular active carbon(ZVI/GAC) micro-electrolysis enhanced by ultrasound(US) coupled with hydrogen peroxide(H_2O_2) was investigated for the deep degradation of nitrobenzene-containing wastewater. The results of scanning electron microscopy-energy dispersive X-rays analysis(SEM-EDS) demonstrated that continuously accelerated regeneration of ZVI and GAC in situ by US could improve the process for converting nitrobenzene(NB) to aniline(AN). H_2O_2 was decomposed catalytically by the byproduct Fe^(2+) ions generated in the micro-electrolysis process to hydroxyl radicals and the organic pollutants in the wastewater were finally mineralized to CO2 and H2O. Effects of the ZVI dosage, the ZVI/GAC mass ratio, the initial pH value and the H_2O_2 dosage on the efficiency for degradation of NB were studied in these experiments. The optimal operating conditions covered a ZVI dosage of 15 g/L, a ZVI/GAC mass ratio of 1:2,an initial pH value of 3 and a H_2O_2 dosage of 4 mL. In this case, the NB removal efficiency reached 97.72% and the total organic carbon(TOC) removal efficiency reached 73.42% at a NB concentration of 300 mg/L. The reduction of NB by USZVI/GAC followed the pseudo-first-order kinetics model, and the pseudo-first-order rate constants were given at different initial pH values. The reaction intermediates such as AN, benzoquinonimine, p-benzoquinone, p-nitrophenol and other organic acids were detected and a probable pathway for NB degradation has been proposed.

The influence of four dual-cure resin cements and surface treatment selection to bond strength of fiber post

In this study, we evaluate the influence of post surface pre-treatments on the bond strength of four different cements to glass fiber posts. Eighty extracted human maxillary central incisors and canines were endodontically treated and standardized post spaces were prepared. Four post pre-treatments were tested： （i） no pre-treatment （NS, control）, （ii） sandblasting （SA）, （iii） silanization （SI） and （iv） sandblasting followed by silanization （SS）. Per pre-treatment, four dual-cure resin cements were used for luting posts： DMG LUXACORE Smartmix Dual, Multilink Automix, RelyX Unicem and Panavia F2.0. All the specimens were subjected to micro push-out test. Two-way analysis of variance and Tukey post hoc tests were performed （α=0.05） to analyze the data. Bond strength was significantly affected by the type of resin cement, and bond strengths of RelyX Unicem and Panavia F2.0 to the fiber posts were significantly higher than the other cement groups. Sandblasting significantly increased the bond strength of DMG group to the fiber posts.

Fabrication of Micro/Nano-textured Titanium Alloy Implant Surface and Its Infl uence on Hydroxyapatite Coatings

We put forward a protocolcombining laser treatment and acid etching to obtain multiscale micro/nano-texture surfaces of titanium alloy implant.Firstly,the operationalparameters of the laser were optimized to obtain an optimum current.Secondly,the laser with the optimum operationalparameters was used to fabricate micro pits.Thirdly,multiple acid etching was used to clean the clinkers of micro pits and generate submicron and nanoscale structures.Finally,the bioactivity of the samples was measured in a simulated body fluid.The results showed that the micropits with a diameter of 150 μm and depth of 50 μm were built successfully with the optimized working current of 13 A.In addition,submicron and nanoscale structures,with 0.5-2 μm microgrooves and 10-20 nm nanopits,were superimposed on micro pits surface by multiple acid etching.There was thick and dense HA coating only observed on the multiscale micro/nano-textured surface compared with polished and micro-textured surface.This indicated that the multiscale micro/nano-texture surface showed better ability toward HA formation,which increased the bioactivity of implants.

Micro-yield behaviors of Al_2O_3-SiO_(2(sf))/Al-Si metal matrix composites

Effects of the volume fraction and the size of crystallized alumina silicate short fibers as well as heat treatment processes on micro-yield strength(MYS) of Al2O3-SiO2(sf)/Al-Si metal matrix composite(MMC) that was fabricated by squeezing cast, were investigated by using continuous loading method on an Instron 5569 tester with a special extensometer with an accuracy of 10?7. The results show that MYS of MMC decreases with the increase of volume fraction and length of the alumina silicate short fibers in the metal matrix composite, respectively. MYS of quenched Al2O3-SiO2(sf)/Al-Si MMC is the lowest, MYS of the MMC through peak-aging treatment is higher than that through other heat treatment methods. And before the peak-aging, MYS of MMC aging treated gradually increases with the increase of the aging time. Aging treatment after solution treatment is a preferred way that enhances micro and macro-yield strength of Al2O3-SiO2(sf)/Al-Si MMC.