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Electronic Microscope (electronic + microscope)
Kinds of Electronic Microscope Selected AbstractsHybrid titanium catalyst supported on core-shell silica/poly(styrene- co -acrylic acid) carrierJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2010Lijun Du Abstract Hybrid titanium catalysts supported on silica/poly(styrene- co -acrylic acid) (SiO2/PSA) core-shell carrier were prepared and studied. The resulting catalysts were characterized by Fourier transform infrared (FTIR) spectroscopy, laser scattering particle analyzer and scanning electronic microscope (SEM). The hybrid catalyst (TiCl3/MgCl2/THF/SiO2·TiCl4/MgCl2/PSA) showed core-shell structure and the thickness of the PSA layer in the two different hybrid catalysts was 2.0 ,m and 5.0 ,m, respectively. The activities of the hybrid catalysts were comparable to the conventional titanium-based Ziegler-Natta catalyst (TiCl3/MgCl2/THF/SiO2). The hybrid catalysts showed lower initial polymerization rate and longer polymerization life time compared with TiCl3/MgCl2/THF/SiO2. The activities of the hybrid catalysts were enhanced firstly and then decreased with increasing P/P. Higher molecular weight and broader molecular weight distribution (MWD) of polyethylene produced by the core-shell hybrid catalysts were obtained. Particularly, the hybrid catalyst with a PSA layer of 5.0 ,m obtained the longest polymerization life time with the highest activity (2071 kg PE mol,1 Ti h,1) and the resulting polyethylene had the broadest MWD (polydispersity index = 11.5) under our experimental conditions. The morphology of the polyethylene particles produced by the hybrid catalysts was spherical, but with irregular subparticles due to the influence of PSA layer. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Fabrication, structures, and properties of acrylonitrile/methyl acrylate copolymers and copolymers containing microencapsulated phase change materialsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2007Na Han Abstract The polyacrylonitrile-methyl acrylate (AN/MA mole ratio 100/0,70/30) copolymers and copolymers (AN/MA mole ratio 85/15) containing up to 40 wt % of microencapsulated n -octadecane (MicroPCMs) are synthesized in water. The MicroPCMs were incorporated at the step of polymerization. The effect of the MA mole ratio and MicroPCMs content on structures and properties of the copolymers were studied by using Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (1H NMR), scanning electronic microscope (SEM), differential scanning calorimetry (DSC), thermogravimetry analysis (TG), gel permeation chromatography (GPC), and X-ray diffraction (XRD). The feeding ratio agreed well with the composition of the AN/MA copolymers. The copolymers are synthesized in the presence of MicroPCMs. The melting point moves to lower temperature (206°C), while the decomposition temperature moves to higher temperature (309°C) with increasing of the MA mole ratio and microcapsules content. The number,average molecular weight of the copolymer is ,30,000. The crystallinity of the copolymer decreases with increasing of the MA mole ratio and microcapsules content. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2776,2781, 2007 [source] Natural bone collagen scaffold combined with OP-1 for bone formation induction in vivoJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2009Yu Qian Abstract The scaffold is a key element to osteogenic tissue engineering as it provides a microenvironment for bone formation. Natural bone collagen scaffold (NBCS) is a novel biomaterial scaffold acid-extracted from organic human bone. The objective of this study was to characterize NBCS and evaluate the osteoconductivity of the scaffold, in combination with osteogenic protein-1 (OP-1), using a rabbit posteolateral lumbar fusion model. Thirty two rabbits were divided into 4 experimental groups, autograft, NBCS alone, OP-1 alone or NBCS combined with OP-1. Bone formation was evaluated by micro-CT, quantitative histological analysis, immunohistochemistry and semi-quantitative RT-PCR at 6 weeks postoperatively. By scanning electronic microscope, we showed that NBCS maintains a porous, interconnecting microarchitecture. Micro-CT analysis demonstrated that NBCS combined with OP-1 significantly induced (p < 0.01) bone formation at the fusion site as compared to control groups. This was confirmed by quantitative histological analysis which demonstrated that the NBCS combined with OP-1 significantly enhanced bone matrix area (17.7 mm2) (p < 0.05) and bone marrow cavity size (71.3 mm2) (p < 0.05) as compared to the controls. Immunohistochemical assessment and RT-PCR also demonstrated that NBCS combined with OP-1 enhanced type I collagen and osteonectin expression. Together, these results suggest that NBCS is an effective scaffold for osteogenesis, and combined with growth factors such as OP-1, possesses both osteoconductive and osteoinductive properties that are sufficient for bone regeneration. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009 [source] Degradation of repaired denture base materials in simulated oral fluidJOURNAL OF ORAL REHABILITATION, Issue 3 2000C.-T. Lin This in vitro study evaluates the degradation of repaired denture bases upon immersion in a simulated oral fluid. Denture base materials (Luciton 199®), after being repaired by Repair Material® and Triad®, using three different joint surface designs (butt, round and 45 ° bevel), were immersed onto 99·5 vol.% ethanol/water solution (with similar solubility parameter) for various amounts of time (0,72 h). The flexural loads of the six combination of groups were measured by the three-point bending tests using a universal testing machine. Acoustic emission (AE) during sample fracturing were processed using the MISTRA 2001 system. The fracture pattern and surface details of the interface were examined with a scanning electronic microscope (SEM). Data were analysed using three-way anova and Tukey LSD tests. SEM micrographs of the fracture interface were used to differentiate the fracture mode. The flexural loads (2·72±0·51 Kgf) of the round joint specimens were significantly higher (P<0·05) than those (butt: 1·66±0·38 Kgf, 45 ° bevel: 1·93±0·41 Kgf) of the other two designs. This corresponds to the microscopic examination in which more cohesive failure mode was found for the round joint group after storage. The flexural loads (2·54±0·39 Kgf) of the specimens repaired with Triad® were significantly higher (P<0·05) than those (1·59±0·40 Kgf) of specimens repaired with Repair Material®. Significant progressive reduction of the flexural load and/or AE signals of the specimens was noted in proportion to the length of time of the immersion in the simulated oral fluid. Mechanical strength of a denture base repaired with a round joint design and light-cured material is significantly higher after immersion in simulated oral fluid. [source] Isothermal Section of a Cu2O,Al2O3,SiO2 Pseudo-Ternary System at 1150°C in AirJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2008Qiuguo Xiao In this study, the isothermal section of a Cu2O,Al2O3,SiO2 pseudo-ternary phase diagram at 1150°C was analyzed by means of a scanning electronic microscope and powder X-ray diffraction of the quenched samples qualitatively, and the compositions of the tie-points of the tie-planes as well as their regions were determined by in situ high-temperature quantitative X-ray diffraction analysis and energy-dispersive X-ray spectroscopy. Then, the isothermal section of the Cu2O,Al2O3,SiO2 pseudo-ternary phase diagram at 1150°C was constructed; it was found that the isothermal section is composed of two single liquid-phase regions, five two-phase regions, and six three-phase regions. [source] Crystalline Transition from H2Ti3O7 Nanotubes to Anatase Nanocrystallines Under Low-Temperature Hydrothermal ConditionsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2006Ning Wang In this paper, we first reported the crystalline transition from H2Ti3O7 nanotubes to anatase TiO2 nanocrystallines under low-temperature hydrothermal conditions (,140°C). A newly proposed mechanism for the crystalline transition from H2Ti3O7 nanotubes to anatase TiO2 nanocrystallines under low-temperature conditions is discussed in detail, which is supported by X-ray diffraction, high-resolution transmission electronic microscope, selected-area electron diffraction, and crystal structure models. [source] Structure and Properties of CdS/Regenerated Cellulose NanocompositesMACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2005Dong Ruan Abstract Summary: Novel inorganic-organic hybrid materials composed of cadmium sulfide (CdS) semiconducting nanocrystals and regenerated cellulose (RC) were prepared by using in situ synthesizing method. Cellulose was dissolved in a 6 wt.-% NaOH/4 wt.-% urea/thiourea aqueous solution at low temperature followed by addition of cadmium chloride (CdCl2), resulting that the CdS nanocrystals were successfully grown in situ in the cellulose solution. Nanocomposite films containing homogeneous CdS nanoparticles were obtained by casting the resulting solution. Their structure and optical properties were characterized by X-ray photoelectron spectroscopy, wide-angle X-ray diffraction, thermogravimetry analysis, dynamic mechanical analysis, atomic force microscopy, transmittance electronic microscope, UV-vis spectroscopy, and photoluminescence spectroscopy. The experimental results confirmed that the CdS nanocrystalline existed in the composite films, and cellulose matrix provided a confined medium for CdS particle growth in uniform size. The CdS/RC composites showed narrow emission in photoluminescence spectra, and their optical absorbance in the UV range was higher than that of the cellulose film without CdS. This work provided a simple method to prepare cellulose functional materials in NaOH/urea aqueous solution. Photoluminescence of CdS/RC nanocomposites and TEM image of CdS nanocrystals dispersed in RC matrix. [source] Impact fracture toughness and morphology of diatomite-filled polypropylene compositesPOLYMER ENGINEERING & SCIENCE, Issue 8 2009Jizhao Liang Impact fracture strength is an important characterization for impact toughness of materials. A polypropylene (PP) filled with diatomite with different diameter (5, 7, and 13 ,m) was fabricated by means a twin-screw extruder. The impact fracture strength of these composites was measured at room temperature to identify the effects of diatomite content and diameter on impact fracture strength of filled polypropylene composites. The results showed that the influence of diatomite on the notched impact strength was significant. When the volume fraction of the diatomite (,f) was less than 10%, the notched impact strength (,I) increased quickly with an addition of ,f, and then the variation of ,I was slight. The notched impact strength of the composite with the diatomite diameter of 7 ,m is the highest when ,f was 10%. Furthermore, the impact fracture surface was observed by using a scanning electronic microscope (SEM) to study the toughening mechanisms. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source] A Novel Cyclic Squamosamide Analogue Compound FLZ Improves Memory Impairment in Artificial Senescence Mice Induced by Chronic Injection of D-Galactose and NaNO2BASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 6 2007Fang Fang Artificially senescent mouse model was induced by consecutive injection of D-galactose (120 mg/kg) and NaNO2 (90 mg/kg) once daily for 60 days. Compound FLZ (75 and 150 mg/kg) was orally administered once daily for 30 days after D-galactose and NaNO2 injection for 30 days. The water maze test was used to evaluate the learning and memory function of mice. The content of malondialdehyde (MDA) and the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in serum were determined using different biochemical kits. The alterations in hippocampus morphology were assessed by light and electronic microscope. Immunoreactive cells of Bcl-2 in the hippocampus were counted by immunohistochemical staining, and Bcl-2 protein expression was analysed by Western blot method. The results indicate that injection of D-galactose and NaNO2 induces memory impairment and neuronal damage in hippocampus of mice. In addition, serum SOD and GSH-Px activities decreased, while MDA level increased. Bcl-2-positive neurons and Bcl-2 protein expression in the hippocampus decreased remarkably. Oral administration of FLZ for 30 days significantly improved the cognitive deficits and the biochemical markers mentioned above, and also reduced the pathological alterations in mouse hippocampus. The results suggest that FLZ ameliorates memory deficits and pathological injury in artificially senescent mice induced by chronic injection of D-galactose and NaNO2, indicating that FLZ is worth further studies for fighting antisenescence and dementia. [source] | |||||||||||||