等离子喷涂过程中纳米粒子生长分析

为了研究等离子喷涂过程中纳米粒子的生长情况,从而为喷涂工艺参数优化提供参考,在B rook晶粒生长经典理论基础上,计算了等离子喷涂纳米ZrO2-7%Y2O3粉末过程中纳米粒子尺寸变化,分析了不同温度历程及纳米粒子初始尺寸对其生长的影响.同时,对纳米团聚体粉末进行等离子喷涂试验.结果表明,纳米结构涂层是由一定比例完全熔化区和部分熔化区组成的特殊的两相结构,其中部分熔化区由经过一定长大但仍保持在纳米尺度的纳米粒子组成.试验结果较好的验证了计算结果,表明基于B rook理论的晶粒生长理论对了解纳米粒子在等离子喷涂过程中的生长有一定的理论指导意义.

黄山大气气溶胶新粒子生长特性观测分析

利用2012年9月22日～10月28日黄山地区大气气溶胶、二氧化硫和臭氧观测数据,结合气象数据,分析气溶胶新粒子的生成-增长特征.分析发现,在33个有效观测日中,有新粒子生成-增长的观测日占总数的18.2％,其中晴天的发生频率为37.5％,新粒子生成-增长都开始于晴天上午,与无新粒子观测日相比,太阳辐射量、风速、SO2及O3浓度较高,环境温度和相对湿度较低.气溶胶新粒子的增长具有由小及大的特点,核模态气溶胶粒子（10～20nm）数浓度最先增加,爱根核模态粒子（20～50nm）数浓度随着时间推移逐渐增大,但浓度峰值依次下降,平均增长率为3.58nm/h.SO2浓度先于核模态气溶胶数浓度到达峰值,其氧化后的产物H2SO4为新粒子的核化提供前体物,并且参与新粒子的增长过程,当SO2浓度较低时,不会发生新粒子生长事件.

层流型凝聚核粒子生长器的设计与测试

为了探究层流型凝聚核粒子计数器的关键部分凝聚核粒子生长器的尺寸结构和流场参数之间的相关性,通过多孔介质材料配合相应内部结构的设计,研制气液物理位置重合、流场相互独立的凝聚核粒子生长器;利用该装置实验得到的水蒸气挥发速率耦合入气流流场进行仿真,研究采样流湿度、调节段温度和生长段温度对装置内部流场过饱和度分布造成的影响。结果表明,采样流湿度为100%,调节段壁面温度为10℃,生长段壁面温度为50℃时,能够得到最理想的过饱和度为2.8。

抗冲共聚聚丙烯树脂粒子的生长机理

在抗冲共聚聚丙烯(hiPP)的聚合过程中,通过在乙烯丙烯共聚阶段加入1,9-癸二烯得到了乙丙无规共聚物(EPR)同步交联的hiPP。利用FTIR,SEM,TEM等方法研究了EPR同步交联hiPP的组成、凝胶含量及hiPP粒子在EPR中的分散形态。表征结果显示,EPR发生同步交联后,其流动性受到阻滞,因此高度均匀并稳定分散于聚丙烯粒子中,与催化剂碎片分散形态相对应,与通常情况下EPR未交联时主要在聚丙烯粒子内部孔隙处聚集的现象进行对比,说明hiPP聚合过程中并未发生催化剂碎片的迁移,而只是由于EPR的迁移造成其在聚丙烯孔隙处的聚集。利用交联EPR可进一步提高EPR在hiPP中的含量而不必担心聚合物颗粒发生团聚和黏釜等问题。

纳米非晶Si_3N_4粉的晶化及粒子长大行为研究

本文对激光气相合成的非晶纳米Ｓｉ３Ｎ４粉在１２００～１７００℃进行热处理，用ＴＥＭ、ＸＲＤ及ＢＥＴ对粉的结晶转变及粒子生长过程进行了表征．实验发现，粉体从１２５０℃开始晶化，有少量的β－Ｓｉ３Ｎ４形成，到１３００℃有α－Ｓｉ３Ｎ４形成，在晶化初期非晶粒子靠表面扩散发生硬团聚．在１４００～１６００℃晶化加速，α相急增，此阶段粒子快速生长，在１７００℃粉体发生碳化，与炉中ＣＯ反应形成部分β－ＳｉＣ，同时，发生Ｓｉ３Ｎ４的α－β转变．

水/油/水双乳化技术制备高效性神经生长因子

背景:神经生长因子是大分子蛋白类物质,很难透过血脑屏障,基因治疗可以有效地将神经营养因子投递到脑内。目的:探索制备高效性神经生长因子基因纳米粒子的方法。方法:利用水/油/水(W/O/W)双乳化技术制备神经生长因子基因纳米粒子,用壳聚糖对其进行表面修饰,同时偶联Tat多肽。切断穹隆-海马伞诱使基底前脑胆碱能神经元溃变。16只SD雄性大鼠随机数字表均分成损伤组和基底前脑显微注射神经生长因子基因的纳米粒子组。结果与结论:制备的纳米粒子粒径分布为110～150nm。壳聚糖可明显提高其表面正电荷和包封率,但对其粒径大小影响不大。偶联Tat多肽则明显提高其转染效率。说明利用水/油/水技术可以成功制备神经生长因子基因纳米粒子。该粒子移植后对基底前脑有明显的保护作用。

氯化铵对TiO_2纳米晶的形成、结构及性能的影响

以四氯化钛为原料,通过氯化铵诱导晶化和热挥发分解法制备了二氧化钛纳米晶,经粉末XRD,TEM,IR和比表面积及热重分析等手段进行了表征.通过对粒子生长动力学分析,在700℃以下存在两种生长势,400℃时出现转折,400℃以下粒子生长所需活化能为8.23 kJ/mol;400℃以上粒子生长需活化能为45.71 kJ/mol.于200℃时灼烧样品的表面积最大,对甲基橙光催化降解活性最高.

Al原子在Ni基衬底表面的扩散及团簇的形成

NiAl纳米颗粒具有较高的能量密度和良好的高温力学性能,铝吸附原子在不同镍基表面上的扩散行为与不同扩散机制对铝在镍基表面沉积生长的影响有待进一步阐明.本文通过采用肘弹性带和分子动力学结合嵌入原子势的方法,系统地研究了单个铝吸附原子在镍基表面的扩散行为和纳米颗粒团簇在十面体(DEC)、立方八面体(CUB)和二十面体(ICO)结构上的生长.研究结果表明:Al吸附原子在三种Ni基底上表面扩散的交换与跳跃两种机制,最低的Ehrlich-Schwoebel(ES)势垒为0.38 eV(交换CUB{111}→100})、0.52 eV(交换DEC{111}→100})和0.52 e V(跳跃ICO{111}→111}),从{111}面扩散到{100}面主要以交换机制为主,而相邻两个{111}面之间的扩散则以跳跃机制为主.沉积的铝原子首先倾向于扩散到台阶边缘和顶点附近.随着Al原子数量的增加,沉积的Al原子开始聚集.对于Ni团簇上的Al原子,在较低温度下在镍基底表面沉积Al原子,可以获得良好的Ni核/Al壳结构.对于二十面体结构基底,其对应的核壳团簇的缺陷数最小,随后为十面体结构和八面体结构.随着生长温度的增加NiAl纳米粒子的表面逐渐开始合金化.

Oriented Growth of PZT thick film embedded with PZT nanoparticles

This paper reports that dense and crack-free （100） oriented lead zirconate titanate （Pb（ Zr0. 52Ti0. 48 ）O3, PZT） thick film embedded with PZT nanopartieles has been successfully fabricated on Pt/Cr/SiO2/Si substrate by using PT transition layer and PVP additive. The thick film possesses single-phase perovskite structure and perfectly （100） oriented. The （100） orientation degree of the PZT films strongly depended on annealing time and for the 4μm-thick PZT film which was annealed at 700℃ for 5 min is the largest. The （100） orientation degree of the PZT thick film gradually strengthen along with the thickness of film decreasing. The 3μm-thick PZT thick film which was annealed at 700℃ for 5 rain has the strongest （100） orientation degree, which is 82. 3%.

Growth and Electronic Properties of Ag Nanoparticles on Reduced CeO2-x（111） Films

Ag nanoparticles grown on reduced CeO2-x thin films have been studied by X-ray plhotoelec- tron spectroscopy and resonant photoelectron spectroscopy of the valence band to understand the effect of oxygen vacancies in the CeO2-x thin films on the growth and interracial elec- tronic properties of Ag. Ag grows as three-dimensional particles on the CeO2-x （111） surface at 300 K. Compared to the fully oxidized ceria substrate surface, Ag favors the growth of smaller particles with a larger particle density on the reduced ceria substrate surface, which can be attributed to the nucleation of Ag on oxygen vacancies. The binding energy of Ag3d increases when the Ag particle size decreases, which is mainly attributed to the final-state screening. The interracial interaction between Ag and CeO2_x（lll） is weak. The resonant enhancement of the 4f level of Ce3＋ species in RPES indicates a partial Ce4＋--＋Ce3＋ reduction after Ag deposited on reduced ceria surface. The sintering temperature of Ag on CeO 1.85 （111） surface during annealing is a little higher than that of Ag on CeO2 （111） surface, indicating that Ag nanoparticles are more stable on the reduced ceria surface.

Effect of Electroacupuncture on Platelet-derived Growth Factor and the Ultrastructure of Mitochondria in Rats with Diabetic Gastroparesis

Objective To observe the effect of electroacupuncture(EA)at the pressure points Zu San Li(ST36),San Yin Jiao(SP6)and Liang Men(ST21)on platelet-derived growth factor(PDGF)and the ultrastructure of mitochondria in rats with diabetic gastroparesis(DGP).Methods Sixty Sprague Dawley(SD)rats were randomly separated into a normal control group(NC,n=10)and a modeling group(n=50).Rats in the modeling group received an injection of 2%streptozotocin(STZ)and a high-fat and highglucose diet for eight weeks to establish a DGP rat model.At the same time,blood glucose and a general symptom score were recorded every week.After modeling,30 successfully modeled rats were randomly separated into the following groups:the DGP group(n=10),the EA group(n=10)and the metoclopramide(MP)group(n=10).After three weeks of intervention,the gastrointestinal propulsive rate was measured by measuring the optical density(OD).The concentration of Ca2+was determined by fluorescence immunoassay,and levels of serum insulin(INS)and PDGF were determined by ELISA.The ultrastructure of mitochondria was observed with transmission electron microscopy.Results(1)After intervention,levels of blood glucose and the general symptom score were greatly decreased in the EA group compared to the DGP group(P<0.01).Compared with the DGP group,the gastric emptying rate and the intestinal propulsive rate of the EA group was significantly improved(P<0.01),and there was no statistically significant difference between the EA and the NC groups.(2)Compared with the NC group,the levels of INS in the DGP group markedly decreased(P<0.05),but there was no significant difference of INS levels between the EA and the MP roups.(3)Compared with the DGP group,theconcentration of Ca2+in the EA and the MP groups significantly increased(P<0.01,P<0.05,respectively).(4)Compared with the NC group,the average OD of PDGF in the DGP group was significantly higher(P<0.01).Compared with the DGP group,levels of PDGF in the EA group increased significantly(P<0.01).(5)There were abundant mitochondria with a clear structure and complete cristae in the NC group.However,in the DGP group,mitochondria were severely swollen,partly vacuolated,and cristae were either fractured,absent,or shortened.In the EA group,mitochondria were slightly swollen,with clear cristae.Conclusions Electroacupuncture at the points Zu San Li(ST36),San Yin Jiao(SP6)and Liang Men(ST21)may improve gastric motility in DGP by up-regulating the amount of PDGF and improving the ultrastructure of mitochondria.

In vitro and in vivo suppression of hepatocellular carcinoma growth by midkine-antisense oligonucleotide-loaded nanoparticles

AIM:To synthesize antisense oligonucleotides (ASODNs) of midkine (MK), package the ASODNs with nanoparticles, and to inhibit hepatocellular carcinoma (HCC) growth using these nanoparticles.METHODS: HepG2 cell proliferation was analyzed in vitro using the 3-(4,5-dimethythiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2Htetrazolium, inner salt assay. The in vivo activity of nanoparticles delivering the MK-ASODNs was analyzed by histopathological and immunohistochemical staining and quantitative real time polymerase chain reaction (PCR). RESULTS: The in vitro proliferation of HepG2 cells was signif icantly inhibited by the nanoparticles packaged with MK-ASODNs (NANO-ASODNs). Furthermore, the NANO- ASODNs signif icantly inhibited the growth of HCC in the mouse model. CONCLUSION: NANO-ASODNs can significantly suppress the growth of HCC in vitro and in vivo.

More stories on Th17 cells

For more than two decades, immunologists have been using the so-called Th1/Th2 paradigm to explain most of the phenomena related to adaptive immunity. The Thl/Th2 paradigm implied the existence of two different, mutu- ally regulated, CD4＋ T helper subsets： Thl cells, driving cell-mediated immune responses involved in tissue damage and fighting infection against intracellular parasites; and Th2 cells that mediate IgE production and are particu- larly involved in eosinophilic inflammation, allergy and clearance of helminthic infections. A third member of the T helper set, IL-17-producing CD4＋ T cells, now called Th17 cells, was recently described as a distinct lineage that does not share developmental pathways with either Thl or Th2 cells. The Th17 subset has been linked to autoimmune disorders, being able to produce IL-17, IL-17F and IL-21 among other inflammatory cytokines. Interestingly, it has been reported that there is not only a cross-regulation among Thl, Th2 and Th17 effector cells but there is also a di- chotomy in the generation of Th17 and T regulatory cells. Therefore, Treg and Th17 effector cells arise in a mutually exclusive fashion, depending on whether they are activated in the presence of TGF-β or TGF-β plus inflammatory cytokines such as IL-6. This review will address the discovery of the Th17 cells, and recent progress on their development and regulation.

Quantifying growth and breakage of agglomerates in fluid-particle flow using discrete particle method

The cohesive solids in liquid flows are featured by the dynamic growth and breakage of agglomerates, and the difficulties in the development, design and optimization of these systems are related to this significant feature.In this paper, discrete particle method is used to simulate a solid–liquid flow system including millions of cohesive particles, the growth rate and breakage rate of agglomerates are then systematically investigated. It was found that the most probable size of the agglomerates is determined by the balance of growth and breakage of the agglomerates the cross point of the lines of growth rate and breakage rate as a function of the particle numbers in an agglomerate, marks the most stable agglomerate size. The finding here provides a feasible way to quantify the dynamic behaviors of growth and breakage of agglomerates, and therefore offers the possibility of quantifying the effects of agglomerates on the hydrodynamics of fluid flows with cohesive particles.

Changes of Circulating Platelet-Derived Growth Factor and Granulocyte Colony-Stimulating Factor in Patients with Condyloma Acuminatum

Objective: To study the expression levels of platelet-derived growth factor (PDGF) and granulocyte colony-stimulatingfactor (G-CSF) in peripheral blood and their role in thepathogenesis of Condyloma acuminatum (CA). Methods: Sera were taken from 70 patients with Condylomaacuminatum and compared with 35 healthy controls. PDGFand G-CSF in serum were quantitated using a dual antibodysandwich enzyme-linked immunoabsorbent assay (ELISA). Results: Serum concentrations of PDGF and G-CSF weresignificantly increased in patients with Condylomaacuminatum (CA) compared to controls (P<0.001 and P<0.005respectively). Serum levels of PDGF and G-CSF correlatedwith clinical severity of CA, but no significant difference wasobserved between different duration of disease groups. Asignificant positive correlation was noticed between neutrophilcount and G-CSF levels (γ=0.38, P<0.001), and the neutrophilcount showed no significant correlation with PDGE Conclusion: The results indicated that increased expressionof PDGF an -CSF in peripheral blood might be involved in pathogenesis of CA.

The mitochondrial serine protease HtrA2/Omi cleaves RIP1 during apoptosis of Ba/F3 cells induced by growth factor withdrawal

Interleukin-3 （IL-3） deprivation of the mouse pro-B cell line Ba/F3 induces cell death that is abrogated by B-cell lymphoma 2 （Bcl-2） overexpression, but remains unaffected by the pan-caspase inhibitor carbobenzoxy-valyl-analyl- aspartyl-[O-methyl]-fluoromethylketone （zVAD-fmk）. IL-3 withdrawal causes receptor-interacting protein （RIP）I cleavage into C-terminal fragments of 30 and 25 kDa, and only cleavage leading to the former was prevented by zVAD-fmk, siRNA experiments demonstrated that generation of the 25-kDa fragment was due to a Bcl-2-modulated release of the mitochondrial serine protease high temperature requirement protein A2 （HtrA2）/Omi. Accordingly, recombinant HtrA2/Omi efficiently cleaved mouse RIP1 in vitro, generating fragments matching those observed in IL-3-deprived Ba/F3 cells. The HtrA2/Omi cleavage site in mouse RIP1 was mapped to the intermediate domain and the corresponding N- and C-terminal fragments were impaired in their ability to activate nuclear factor-r,B, c-Jun N-terminal kinase and p38 mitogen-activated protein kinase. Interestingly, knockdown of HtrA2/Omi afforded pro- tection against IL-3 withdrawal-induced death in the presence of zVAD-fmk, demonstrating a role for HtrA2/Omi in caspase-independent cell death during growth factor withdrawal by cleaving RIP1.

Study of Plasma and Ion Beam Sputtering Processes

The effects of plasma （ions, electrons） and other energetic particles are now widely used for substrate cleaning as well as to assist and control thin film growth and various applications. In this work, historical review of the plasma and its various types are given and described. Different types of gas discharge and plasma production are also discussed in detail. Furthermore, technique of ion beam extraction from a plasma source for sputtering process by using a suitable electrode is carefully studied and given. In further consequence, a general review about the physics and mechanism of sputtering processes is studied. Different types of sputtering techniques are investigated and clarified. Theoretical treatment for determination of sputtering yield for low and high atomic species elements as a function of energy from 100 to 5,000 eV are studied and discussed. Finally, various applications of plasma-and-ion beam sputtering will also be mentioned and discussed.

Densification and grain growth kinetics of boron carbide powder during ultrahigh temperature spark plasma sintering

Dense B;C material was fabricated using spark plasma sintering(SPS), and the densification mechanisms and grain growth kinetics were revealed. The density, hardness, transverse flexure strength and toughness of samples were investigated and the model predictions were confirmed by SEM and TEM experimental observations. Results show that SPSed B;C exhibits two sintering periods: a densification period(1800-2000 °C) and a grain growth period(2100-2200 °C). Based on steady-state creep model, densification proceeds by grain boundary sliding and then dislocation-climb-controlled mechanism. Grain growth mechanism is controlled by grain boundary diffusion at 2100 °C,and then governed by volume or liquid-phase diffusion at 2200 °C.

The current G-CSF use in cancer patients with chemotherapy

Objective: The purpose of the study was to survey current G-CSF use in cancer patients, investigate whether the use of granulocyte colony-stimulating factor(G-CSF) is standardized. Methods: From July 2012 to October 2012, patients in a third-grade class-A hospital were investigated by self-designed questionnaires, according to ASCO's recommendations for white blood cell growth factors in 2006 and NCCN myeloid growth factors guideline in 2012. Results: Two hundred and twenty-two patients treated with 724 courses of chemotherapy were included. In prophylactic use, 259(35.8%) cases used G-CSF that the guideline doesn't recommend, which belonged to excessive use, the dose were 274 700 μg, accounting for 59.7% of the totle prophylactic use; 105(14.5%) didn't use while the guideline recommend, belonging to lack of use. 89.0% of the prophylactic use were 24–72 h after chemotherapy, only a few(5.4%) on the day of chemotherapy. In therapeutic use, only 3.1% were standardized, with the dose of 23 000 μg, accounting for 7.4% of the total. So 92.6% were excessive. 14.2% of the therapeutic use were 24–72 h after chemotherapy, 21.2% on the day of chemotherapy. Conclusion: More than 50% use of G-CSF weren't standardized, especially the excessive use.

拉瓦尔喷管内射流凝结流动数值研究

为明确拉瓦尔喷管内流动凝结效应以及喷管几何条件、水蒸气含量等因素对凝结状态的影响,采用综合了流动控制方程、相变成核模型和粒子生长模型的欧拉离散相计算方法,对扩张比分别为2、3、4、5和水蒸气含量分别为10%、30%、50%、70%、90%、100%的模型进行数值计算分析。计算结果表明:水蒸气凝结对喷管内的流场参数具有显著影响,水蒸气凝结释放潜热,流场温度明显高于不考虑凝结效应的模型状态;随着扩张比增大,轴线上喷管出口处液滴半径增随着喷管扩张半角增大,轴线上液滴出现位置更靠近喉部,轴线上喷管出口处液滴半径增大;随着水蒸气含量增大,轴线上液滴出现位置更靠近喉部,水蒸气含量与液滴粒径之间表现为非线性关系。