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Transmission Electron Microscope Observation (transmission + electron_microscope_observation)
Selected AbstractsSpray Pyrolysis of Fe3O4,BaTiO3 Composite ParticlesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2009Tomoyuki Adachi Fe3O4,BaTiO3 composite particles were successfully prepared by ultrasonic spray pyrolysis. A mixture of iron(III) nitrate, barium acetate and titanium tetrachloride aqueous solution were atomized into the mist, and the mist was dried and pyrolyzed in N2 (90%) and H2 (10%) atmosphere. Fe3O4,BaTiO3 composite particle was obtained between 900° and 950°C while the coexistence of FeO was detected at 1000°C. Transmission electron microscope observation revealed that the composite particle is consisted of nanocrystalline having primary particle size of 35 nm. Lattice parameter of the Fe3O4,BaTiO3 nanocomposite particle was 0.8404 nm that is larger than that of pure Fe3O4. Coercivity of the nanocomposite particle (390 Oe) was much larger than that of pure Fe3O4 (140 Oe). These results suggest that slight diffusion of Ba into Fe3O4 occurred. [source] Mechanical and dynamic mechanical properties of nylon 66/montmorillonite nanocomposites fabricated by melt compoundingPOLYMER INTERNATIONAL, Issue 8 2004Zhong-Zhen Yu Abstract Nylon 66 nanocomposites were prepared by melt compounding of nylon 66 with organically modified montmorillonite (MMT). The organic MMT was pre-modified with about 14 wt% of ammonium surfactant, much lower than the 35,46 wt% in most commercial organic MMT powders. Transmission electron microscope observation indicated that the MMT layers were well exfoliated in nylon 66 matrix. Dynamic mechanical analysis confirmed the constraint effect of exfoliated MMT layers on nylon 66 chains, which benefited the increased storage modulus, increased glass transition temperature and reduced magnitude of alpha relaxation peak. The effects of organic MMT loading levels on reinforcement and fracture behaviour of the nanocomposites were evaluated using tensile and three-point bending tests. The addition of the organic MMT clearly increased Young's modulus and tensile strength but decreased ductility and fracture toughness of nylon 66. Copyright © 2004 Society of Chemical Industry [source] d -Alanyl ester depletion of teichoic acids in Lactobacillus reuteri 100-23 results in impaired colonization of the mouse gastrointestinal tractENVIRONMENTAL MICROBIOLOGY, Issue 7 2007Jens Walter Summary The dlt operon of Gram-positive bacteria encodes proteins required for the incorporation of d -alanine esters into cell wall-associated teichoic acids (TA). d -Alanylation of TA has been shown to be important for acid tolerance, resistance to antimicrobial peptides, adhesion, biofilm formation, and virulence of a variety of pathogenic organisms. The aim of this study was to determine the importance of d -alanylation for colonization of the gastrointestinal tract by Lactobacillus reuteri 100-23. Insertional inactivation of the dltA gene resulted in complete depletion of d -alanine substitution of lipoteichoic acids. The dlt mutant had similar growth characteristics as the wild type under standard in vitro conditions, but formed lower population sizes in the gastrointestinal tract of ex- Lactobacillus -free mice, and was almost eliminated from the habitat in competition experiments with the parental strain. In contrast to the wild type, the dlt mutant was unable to form a biofilm on the forestomach epithelium during gut colonization. Transmission electron microscope observations showed evidence of cell wall damage of mutant bacteria present in the forestomach. The dlt mutant had impaired growth under acidic culture conditions and increased susceptibility to the cationic peptide nisin relative to the wild type. Ex vivo adherence of the dlt mutant to the forestomach epithelium was not impaired. This study showed that d -alanylation is an important cell function of L. reuteri that seems to protect this commensal organism against the hostile conditions prevailing in the murine forestomach. [source] Awns play a dominant role in carbohydrate production during the grain-filling stages in wheat (Triticum aestivum)PHYSIOLOGIA PLANTARUM, Issue 4 2006Xiaojuan Li In wheat (Triticum aestivum L), the leaves particularly flag leaves have been considered to be the key organs contributing to higher yields, whereas awns have been considered subsidiary organs. Compared with extensive investigations on the assimilation contribution of leaves, the photosynthetic characteristics of awns have not been well studied. In this study, we investigated the ultrastructure of chloroplasts, oxygen evolution, and phosphoenolpyruvate carboxylase [phosphoenolpyruvate carboxylase (PEPCase) EC 4.1.1.31)] activity in both flag leaves and awns during the ontogenesis of wheat. Transmission electron microscope observations showed initial increases in the sizes of grana and the degree of granum stacks from the florescence-emergence stage both in flag leaves and in awns, followed by the breakdown of membrane systems after the milk-development stage. The results of oxygen evolution assays revealed that in both organs, the rate of photosynthesis increased in the first few stages and then decreased, but the decrease occurred much earlier in flag leaves than in awns. A PEPCase activity assay demonstrated that the activity of PEPCase was much higher in awns than in flag leaves throughout ontogeny; the value was particularly high at the late stages of grain filling. Our results suggest that awns play a dominant role in contributing to large grains and a high grain yield in awned wheat cultivars, particularly during the grain-filling stages. [source] Synthesis and Characterization of Nanostructured Manganese Dioxide Used as Positive Electrode Material for Electrochemical Capacitor with Lithium Hydroxide ElectrolyteCHINESE JOURNAL OF CHEMISTRY, Issue 1 2008An-Bao YUAN Abstract A nanostructured manganese dioxide electrode material was prepared using a solid-reaction route starting with MnCl2·4H2O and NH4HCO3, and its electrochemical performance as a positive electrode for MnO2/activated carbon hybrid supercapacitor with 1 mol·L,1 LiOH electrolyte was reported. The material was proved to be a mixture of nanostructured , -MnO2 and , -MnO2 containing some bound water in the structure, which was characterized by X-ray diffraction analysis, infrared spectrum analysis, and transmission electron microscope observation. Electrochemical properties of the MnO2 electrode and the MnO2/AC capacitor were investigated by cyclic voltammetry, ac impedance and galvanostatic charge/discharge methods. Experimental results showed that the MnO2 electrode exhibited faradaic pseudocapacitance behavior and higher specific capacitance in 1 mol·L,1 LiOH electrolyte. The MnO2/AC hybrid capacitor with 1 mol·L,1 LiOH electrolyte presented excellent rate charge/discharge ability and cyclic stability. [source] | |||||||||||||