超小Ag纳米粒子的控制制备及其丙烯气相环氧化性能

负载型金属催化剂的性能与金属纳米粒子的粒径密切相关,但目前传统合成方法还无法高效地合成颗粒尺寸为1～3 nm的超小金属纳米粒子。以Ag纳米粒子为研究模型,在油胺体系中,采用改进的"降温法"制备得到尺寸分布在1～3 nm范围内的超小Ag纳米粒子。在此基础上,将所合成的超小Ag纳米粒子和尺寸在10 nm的Ag纳米粒子分别负载到经油酸改性的碳酸钡载体上,并经"两步焙烧法"制备了负载不同尺寸Ag纳米粒子的Ag/BaCO_3催化剂(分别标记为Ag-BaCO_3~#-10 nm和Ag-BaCO_3~#-3 nm)。同时,研究了两种催化剂在丙烯气相环氧化反应中的性能。结果表明相比于Ag-BaCO_3~#-10 nm催化剂, Ag-BaCO_3~#-3 nm表现出更好的催化活性,在较低温度下具有更高的丙烯转化率和环氧丙烷选择性。在150℃时其催化性能达到最佳,具有88.2%的PO选择性和0.8%的丙烯转化率。     

高能球磨合成纳米WC-Co复合粉末的特性

采用变转速多次循环高能球磨工艺在32min制备出了平均晶粒尺寸约为25nm的纳米WC-10CO-0．8VC-0．2Cr3C2(重量分数)复合粉末，并用化学元素分析、XRD，TEM，DTA对纳米WC—Co复合粉末的特性进行了表征和分析。结果表明，变转速多次循环高能球磨工艺制备的纳米WC—CO复合粉末，化学成分合格，杂质含量低，球磨效率高；球磨过程是一个晶粒逐渐细化的过程，同时也是一个晶格畸变逐渐增加、粉末体系能量逐渐增大的过程；球磨得到的WC-Co纳米复合粉末颗粒形貌基本为球形，粒径分布较宽，颗粒中存在着一些团聚体，平均颗粒尺寸约为50nm；纳米WC-10Co-0．8VC-0．2Cr3C2(wt％)复合粉末的共晶点约为1280℃。纳米复合粉末中W，Co，V，Cr元素分布均匀弥散。     

CoPt3磁性纳米颗粒的制备及其磁性能的优化

采用湿化学还原法制备了CoPt3磁性纳米颗粒,并研究了第三组元Ag对其磁性能的改善作用.结果表明,采用多重还原法可成功制备出fcc结构且平均粒径约2.6 nm的CoPt3磁性纳米颗粒,而Ag的加入使得CoPt3磁性纳米颗粒的矫顽力由78.4kA/m提高到240 kA/m.     

约束弧等离子体制备铝纳米粉体的研究

利用自行研制的约束弧等离子体制备金属纳米粉试验装置,成功制备了平均粒度为44nm的铝纳米粉体。利用X射线衍射(XRD)、BET吸附法、透射电子显微镜(TEM)和相应选区电子衍射(SAED)等测试手段对所制备样品的晶体结构、形貌、粒度及其分布、比表面积进行性能表征。试验结果表明:约束弧等离子体法制备的铝纳米粉晶体结构为fcc结构的晶态,与体材料相比晶格常数发生膨胀。比表面积为41m2.g-1,粒径范围分布在20~70nm之间,平均粒径为44nm,粒度均匀,分散性好,呈规则球形链状分布。     

原位制备细晶Si3N4-Si2N2O复相陶瓷

以Y2O3和Al2O3纳米陶瓷粉体作为烧结助剂，液相烧结非晶纳米Si3N4陶瓷粉体，制备Si3N4-Si2N2O复相陶瓷。Si2N2O相通过原位反应2Si3N4(s) 1．5O2(g)：3S12N2O(s) N2(g)生成。160012烧结，烧结体保温30min，Si2N2O体积分数达到52％，基本由细小均匀的球形晶粒构成。平均粒径尺寸210nm，相变过程中，个别颗粒异常长大，长径比达到1．5。保温时间对孔隙、密度和粒径产生重要影响：随着保温时间的延长，孔隙逐渐收缩减小，烧结体的致密度逐渐提高，晶粒逐渐长大，保温60min，孔隙几乎完全闭合，相对密度达到99．1％，平均粒径280nm。当保温时间达到90min时，相对密度增加并不明显，但平均粒径长大到360nm。     

铕掺杂对二氧化钛光催化降解甲基橙性能的影响

以钛酸四正丁酯为原料,利用溶胶-凝胶法制备了纯的和不同Eu含量掺杂的TiO2纳米粒子,利用XRD对样品进行了表征,并以甲基橙的光催化降解研究了样品的光催化性能.发现Eu的掺杂抑制了TiO2粒径的增长,细化了晶粒;同时,Eu掺入到TiO2的晶格中,引起了晶格的畸变和膨胀.结果表明,适量Eu的掺杂可提高TiO2的光催化性能,在本试验进行的条件下,当掺杂摩尔分数为0.1%时,光催化性能最好.     

粉末冶金Cu-0．6％A1合金内氧化析出产物的观察

用扫描电子显微镜、透射电子显微镜及其携带的能谱分析仪、高分辨透射电子显微镜等设备，对粉末冶金内氧化法制备的Cu-0．696A1合金的微观组织进行了观察分析，重点观察了弥散析出相的颗粒形貌、大小及分布，并对其物相及影响因素进行了分析和讨论。结果表明：铜基体相上弥散分布的颗粒相为A12O3，晶内A12O3颗粒的平均粒径5nm，平均间距20nm；晶界处A12O3颗粒的平均粒径20nm，平均间跑50nm。     

Ag^＋掺杂TiO2纳米粉体制备及光催化性能研究

以钛酸四丁酯为原料,利用溶胶凝胶法制备Ag 掺杂TiO2纳米粉体,采用正交实验考察了掺杂量、浓硝酸、冰醋酸、煅烧温度等因素对其制备的影响,从而确定制备工艺最佳条件.通过XRD、TEM、TG-DSC等测试技术对掺杂纳米TiO2粉体进行表征.最佳工艺条件为:掺Ag 量0.5 %(摩尔分数),冰醋酸1mL,浓硝酸0.2mL,煅烧温度450℃,制得颗粒粒径为12.16nm.以甲基橙为降解物,通过自制光催化反应装置,研究了光催化剂的活性,结果表明:Ag 掺杂制备的TiO2纳米粉体具有较高的光催化活性,试验条件下Ag 掺杂TiO2纳米粉体最高降解率为79.38%.     

多流气雾化工艺参数的研究

采用正交实验方法系统地研究了上层气流压力、下层气流压力、金属熔液温度、导液管突出高度对多流气雾化法工艺所制备粉末的平均粒径及粒度分布的影响，通过直观分析和方差分析，评价了各参数对粉末粒度的显著程度，优化了多流气雾化粉末制备法的丁艺参数。以焊锡63A为原材料的实验结果表明：最佳的工艺参数为上层喷嘴压力0．7MPa，下层喷嘴压力0．4MPa．金属熔液温度350℃．导液管突出高度为4mm；所制备粉末的平均粒径为6．3μm，粒度小于10μm的比例达到77．3％．且粒径分加曲线中的第一波峰值达到500nm左右，比现有报道的粒径分布曲线第一波峰值减小了一个数量级；     

纳米二氧化钛热处理过程研究

以四氯化钛为原料,采用碱中和法制备水合二氧化钛,然后在不同温度下热处理分别制备锐钛型纳米二氧化钛和金红石型纳米二氧化钛。采用拉曼光谱、XRD和紫外可见光谱等手段分析了热处理过程对样品的晶体结构、比表面积、微孔体积、紫外吸收光谱等性能的影响。试验结果表明,未经热处理的样品存在氧空位缺陷,具有较大的晶格畸变,随着热处理温度的提高,样品晶粒尺寸从6 nm逐渐长大至70 nm,比表面积从186 m~2·g~(-1)减少至5.6 m~2·g~(-1),总孔体积从0.085 cm~3·g~(-1)减小至0.001 3 cm~3·g~(-1),晶型由无定型向锐钛型和金红石相逐步转化,晶格畸变逐渐减小。在600℃以下热处理样品为锐钛型,在600～650℃的温度下处理形成金红石与锐钛的混晶,680～750℃有六钛酸钠生成,800℃以后全部转化为金红石结构。     

The filament lattice of striated muscle

The filament lattice of striated muscle is an overlapping hexagonal array of thick and thin filaments within which muscle contraction takes place. Its structure can be studied by electron microscopy or X-ray diffraction. With the latter technique, structural changes can be monitored during contraction and other physiological conditions. The lattice of intact muscle fibers can change size through osmotic swelling or shrinking or by changing the sarcomere length of the muscle. Similarly, muscle fibers that have been chemically or mechanically skinned can be compressed with bathing solutions containing very large inert polymeric molecules. The effects of lattice change on muscle contraction in vertebrate skeletal and cardiac muscle and in invertebrate striated muscle are reviewed. The force developed, the speed of shortening, and stiffness are compared with structural changes occurring within the lattice. Radial forces between the filaments in the lattice, which can include electrostatic, Van der Waals, entropic, structural, and cross bridge, are assessed for their contributions to lattice stability and to the contraction process.     

Z/I and A-band lattice spacings in frog skeletal muscle: effects of contraction and osmolarity

A-band and Z-line/I-band lattice spacings were measured by small-angle X-ray diffraction from relaxed and isometrically-contracting whole frog sartorius muscles with lattice spacings reduced or swollen by changing the osmolarity of the bathing solution. A-band spacing increased by approximately 3% upon isometric contraction at reduced lattice spacings (245-356 mOsm) and decreased by approximately 1% at swollen spacings (172 mOsm), similarly to the behaviour of skinned muscles upon changing from the relaxed state to rigor. The Z/I lattice underwent a significant lattice expansion (3-8%) upon isometric contraction at all osmolarities, in qualitative agreement (but quantitative disagreement) with results from electron microscopy on mammalian skeletal muscle. Lattice areas calculated for the Z/I and A-band lattices indicate a barrel-shaped sarcomere in the resting state, which may provide a partial explanation for how longitudinal forces produced in the A-band can produce a radial expansive force in the Z-line during contraction. The radial component of cross-bridge stiffness was calculated from the A-band data for contracting muscle, using a lattice stability model incorporating structural, osmotic and electrostatic forces. The calculations gave a radial cross-bridge stiffness during contraction of about 9 x 10(5) N m-2, and outward radial force per thick filament in normal Ringer's solution of 6 x 10(-9) N, corresponding to a radial force per cross-bridge of 10(-11) N.     

Topical tamoxifen--a potential therapeutic regime in treating excessive dermal scarring?

Abnormal dermal scarring which affects a large number of people is aesthetically disfiguring and can be functionally disabling. Existing medical and surgical strategies to prevent or to treat scars are frequently disappointing and more effective therapies are needed. Tamoxifen, which has been used extensively in the treatment of breast cancer over the last 20 years has recently been shown to inhibit the proliferation of fibroblasts cultured from keloid biopsies. Successful treatment of retroperitoneal fibrosis and desmoid tumours with tamoxifen has also been reported. We have investigated the potential of tamoxifen as an inhibitor of wound contraction, using fibroblast-populated collagen lattices as an in vitro model. From these studies we postulate that tamoxifen may have potential clinical significance in the treatment of abnormal scarring. Normal adult human skin fibroblasts were embedded within type I collagen, then medium either with or without addition of tamoxifen was added to the collagen lattices. Lattice diameters were measured at intervals to assess the influence of tamoxifen on the lattice contraction. The reversibility of the inhibitory effect of tamoxifen on lattice contraction was investigated by 'washing out the tamoxifen' at different time-points. To visualise changes in the morphology of fibroblasts MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] was added to the lattices. Tamoxifen at 1 and 5 microM had no significant influence on lattice contraction but higher concentrations of 50 and 100 microM completely inhibited contraction. At intermediate concentrations from 10 to 20 microM the degree of lattice contraction was dose-dependent. The reversibility of the inhibition was both dose- and time-dependent. Both the inhibition of contraction and the reversibility of inhibition appeared to correlate with changes in fibroblast morphology. The dose- and time-dependent inhibition of contraction by fibroblasts suggests that tamoxifen could be investigated as a novel potential therapeutic agent in treating abnormal dermal scarring.     

Evaluation of Structural and Optical Properties of Mn-Doped ZnO Thin Films Synthesized by Sol-Gel Technique

Undoped ZnO and Mn-doped ZnO (MZO) films with 0.25, 0.50, and 0.75?mol pct were synthesized onto glass substrates by sol-gel spin-coating technique, and the effects of Mn on structural, morphologic, and optical properties were investigated. The XRD results indicate that the films have wurtzite structure with polycrystalline nature. However, the dominant peak was (002) diffraction peak for all samples; other diffraction peaks with less intensity such as (100), (101), (102), (110), (103), (112), and (004) were observed for the undoped ZnO. The lattice parameter values of MZO thin films were lower than that of the undoped ZnO. Plane stress values indicated that the films had the tensile stress. A decrease in the grain sizes was observed with the increasing Mn mole?percent. The optical transmission values were found to be 82?pct for the undoped ZnO and 80, 78, and 75?pct for the MZO with 0.25, 0.50, and 0.75?mol?pct, respectively, at the wavelength of 405?nm. The optical band gap values decreased from 3.287 to 3.270?eV, the surface roughness values increased from 58.13 to 60.67?nm, Urbach energy values increased??a 18.3-meV difference in Urbach energy was observed??and in addition, the steepness parameters decreased with increasing Mn content from 0 to 0.75?mol?pct.     

Agents with periodontal regenerative potential regulate cell-mediated collagen lattice contraction in vitro

A variety of pharmaceutical agents has been proposed for use in periodontal therapy to inhibit loss of alveolar bone and to promote regeneration of tissues lost to disease. The purpose of this study was to determine the effects of such agents on periodontal cell-mediated gel contraction, an in vitro process considered representative of wound contraction and remodeling in vivo. Human gingival fibroblasts were cultured in a type I collagen lattice, and contraction was quantified by means of a computer-assisted video imaging system. Cell-gel combinations were prepared with cells both pre-exposed and non-exposed to agents; non-anchored cell-gels were then incubated with agents for various time periods. Agents tested included Demecolcine (an inhibitor of cytoskeletal contraction), growth factors (i.e., TGF-beta 1, PDGF, and IGF-1), and non-steroidal anti-inflammatory drugs (NSAIDs) (indomethacin, ibuprofen, naproxen, and flurbiprofen). While Demecolcine inhibited gel contraction, TGF-beta 1 (1-20 ng/mL), PDGF (100 ng/ML), IGF-1 (1000 ng/mL), and [PDGF + IGF], all of which have been reported to enhance wound healing in vivo, promoted lattice contraction in this system. In contrast, NSAIDs inhibited cell-gel contraction. Ethanol, used to solubilize two specific NSAIDs, also inhibited cell proliferation and gel contractile ability, even at very low concentrations. These findings indicate that periodontal cells respond differently to various agents in vitro and may be adversely affected by alcohol. Furthermore, the results of this study suggest that the cell-lattice contraction system holds potential as a method for screening agents for positive or negative effects on cell activity.     

Crystal structure,microstructure and magnetic properties of SmCo-based films treated by different annealing methods

Effect of conventional thermal annealing(CTA) and rapid recurrent thermal annealing(RRTA) processes on crystal structure,mi-crostructure,and magnetic properties of the SmCo-based films were investigated.The results indicated that the CTA-treated films exhibited poor permanent magnetic properties,and a low intrinsic coercivity of 72.8 kA/m was observed.Wide hysteresis loop was obtained for the RRTA-treated films,providing better permanent magnetic properties.The intrinsic coercivity reached 312.0 kA/m.According to the X-ray diffraction(XRD) and atomic force microscopy(AFM) results,the magnetic properties of the CTA-treated films and RRTA-treated films were found to be correlated with the crystal structure and microstructure,which were strongly determined by the annealing treatment.CTA treatment led to poor crystallization effects for the films,and a rough surface(RMS=3.47 nm and P-V=35.42 nm) and large grain size of 92.7 nm were observed correspondingly.However,the RRTA treatment exhibited great contributions on the crystallization of the films,which is accountable for the smooth surface(RMS=2.047 nm and P-V=16.43 nm) and fine grain size of 60.8 nm.     

Gd掺杂CdTe薄膜的结构和光学特性研究

用真空热蒸发法在玻璃衬底制备CdTe和Cd掺杂CdTe薄膜.研究热处理和Gd掺杂量对CdTe薄膜结构、光学特性的影响.结果表明,薄膜均为立方闪锌矿结构,Gd的掺入没有改变薄膜的晶体结构,但使薄膜的晶粒尺寸减小,晶格常数和晶胞体积略有增大,并使其择优取向由[220]晶向变为[111]晶向.掺Gd使薄膜在可见光范围透过率增强,但对光能隙影响不大.     

Gap junctional intercellular communication contributes to the contraction of rat osteoblast populated collagen lattices

The contraction of native collagen lattices by resident mesenchymal cells mimics the organization of collagen during development and repair. Lattice contraction is cell density dependent, suggesting that cell-to-cell communications may contribute to the process. This possibility was investigated by comparing lattice contraction by four rat osteoblastic cell lines: ROS 17/2.8 cells (ROS); ROS transfected with an antisense cDNA sequence of the gap junctional protein connexin 43 (RCx16); ROS transfected with connexin 45 cDNA, a connexin not normally expressed in ROS cells (ROS/Cx45); and ROS transfected with cDNA encoding carboxy-terminal truncated Cx45 (ROS/Cx45tr). The cell coupling indices, which reflect gap junctional communication, were quantitated by the fluorescent dye scrape loading. ROS cells were well coupled (index 3.0), ROS/Cx45tr were better coupled (index 4.2), ROS/Cx45 were poorly coupled (index 1.7), and RCx16 showed no coupling (index 1.1). As determined by immunoblotting, the level of connexin 43 protein was increased in both ROS/Cx45tr and ROS/Cx45 cell lines compared with ROS cells, while the level in RCx16 cells was reduced. ROS populated collagen lattices (PCLs) contracted significantly more at day 5 (177 mm2 to 67 mm2) than ROS/Cx45tr (84 mm2), ROS/Cx45 (108 mm2), or RCx16 (114 mm2). Myosin ATPase activity, which is required for lattice contraction, was equivalent in all four cell lines, indicating that it was not responsible for inhibiting PCL contraction. ROS cells in collagen appeared elongated compared with the other cell lines which were more rounded. These experiments suggest gap junctional communication contributes to PCL contraction by resident osteoblasts.     

射频磁控溅镀掺杂铜对钛酸锌薄膜中相变化及微结构的影响

探讨了ZnTiO₃薄膜掺杂Cu元素对于薄膜性质、相变化与微结构之影响.实验是在一定温度下以射频磁控溅镀系统将铜沉积于ZnTiO₃陶瓷靶上,控制沉积于ZnTiO₃陶瓷靶上铜含量之后,再沉积掺杂铜的钛酸锌薄膜于SiO₂/Si基板上.成长出来的薄膜经由ESCA分析得知铜的质量分数分别为0.84%、2.33%和2.84%.从XRD分析常温下掺杂Cu的ZnTiO₃薄膜为非晶质态,经过600℃退火后,ZnTiO₃薄膜则由非晶质态转变成Zn₂Ti₃O₈结晶相,而未掺杂铜的ZnTiO₃薄膜在600℃退火时并没有结晶相产生.ZnTiO₃薄膜经过900℃退火后,Zn₂Ti₃O₈相分解成Zn₂TiO₄相和TiO₂相,且ZnTiO₃晶格常数因为Cu离子置换至Zn离子的位置有变小的趋势.由TEM分析证实Cu离子与Zn离子的置换,导致晶格应变产生双晶缺陷.经由XRD、SEM和TEM分析得知掺杂太多的铜会抑制TiO₂相的生成,而随着过多的Cu析出,晶体平均晶粒慢慢变小晶格应变也随之降低,以致晶格常数回复往原来晶格常数方向趋近.      

SmCo/Co多层交换弹性纳米晶复合永磁薄膜的制备和磁耦合研究

利用磁控溅射的方法,在室温条件的Si基片上制备了[SmCo(25nm)/Co(x)]4/SmCo(25 nm)多层交换弹性纳米晶复合永磁薄膜(Co层厚度x=0～10 nm),经过550 ℃/20 min的真空退火处理使薄膜结晶后,进行磁性测试和磁耦合分析.结果表明:SmCo层厚度固定为25 nm时,调整Co层的厚度,从0至10 nm逐渐增加,矫顽力从2270.3 kA·m-1逐渐降低至1040.5 kA·m-1,同时,饱和磁化强度和剩磁随Co层厚度增加逐渐增加,上升了60％.当加入10 nm的Co层后,多层膜的最大磁能积比125 nm的单层SmCo薄膜增加了46％.另外,与SmCo/Co双层交换弹性薄膜在退磁过程中表现的零场附近的软硬磁双相行为相比,SmCo/Co多层交换弹性薄膜表现出单相反转行为,说明体系中的两种磁性层具有更好的磁耦合.经过磁耦合研究发现,当Co软磁层较薄时,薄膜中磁性颗粒以颗粒间交换耦合为主;当软磁层厚度增加时,颗粒间交换耦合减弱,静磁耦合增强,保证了软硬磁相之间的良好磁耦合作用.Co层的加入有效地提高了薄膜的磁性能.