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Electron Microscopy Examination (electron + microscopy_examination)
Selected AbstractsEffect of phenylalanine and tyrosine analogues on Bactrocera oleae Gmelin (Dipt., Tephritidae) reproductionJOURNAL OF APPLIED ENTOMOLOGY, Issue 7 2001E. N. Zografou The effect of nine phenylalanine and tyrosine analogues at various concentrations upon the reproduction of adult olive fruit fly Bactrocera oleae Gmelin (Diptera, Tephritidae), was tested. Fecundity (eggs/female/day) and percentage egg hatchability was significantly reduced by the following anti-amino acids (in parentheses are indicated the antagonized amino acid): p-fluoro- DL -phenylalanine (phe), p-amino- DL - and - L -phenylalanine (tyr), 3-amino- L -tyrosine (tyr) and L -mimosine (tyr), at concentrations of 0.1, 0.25, 0.05 and 0.5% in the diet, respectively. Hatchability was also affected by two other analogues of phenylalanine and tyrosine, p-bromo- DL -phenylalanine at a concentration of 10% and m-fluoro- DL -tyrosine at a concentration of 1.5%. Insect survival was affected only by p-fluorophenylalanine and 3-amino- L -tyrosine at concentrations 0.25 and 6%, respectively. No significant differences were observed between the survival of the two sexes. Finally, ,-2-thienyl- DL -alanine (phe) and ,-methyl- DL -p-tyrosine (tyr) did not affect any of the parameters tested. Electron microscopy examination of the follicles and the egg-shell structure of eggs laid by females fed with diets containing p-amino- L -phenylalanine and 3-amino- L -tyrosine, revealed abnormalities related to the egg-shell fine structure. [source] Epithelioid osteosarcoma presenting as a rapidly expanding maxillary mass,HEAD & NECK: JOURNAL FOR THE SCIENCES & SPECIALTIES OF THE HEAD AND NECK, Issue 7 2007Joseph Rinaggio DDS Abstract Background. Osteosarcomas of the jaws account for less than 10% of reported neoplasms of this type. Patients with osteosarcoma in this region tend to be in the late-third to mid-fourth decades of life. The osteoblastic, chondroblastic, and fibroblastic variants constitute the majority of lesions. Methods. A mass was observed in the maxilla of a 50-year-old male who presented for a complete odontectomy. Over the ensuing weeks, the mass substantially increased in size, despite multimodality treatment efforts. Results. Radiographic findings revealed a mixed density mass of the left maxilla. Histologic, immunohistochemical, and electron microscopy examination of the tumor showed a malignant mesenchymal neoplasm consisting of sheets of epithelioid and spindle cells exhibiting focal osteoid formation. Conclusions. We report a rare and aggressive case of epithelioid osteosarcoma arising in the maxillofacial complex. © 2007 Wiley Periodicals, Inc. Head Neck, 2007 [source] Strain-dependent viral dynamics and virus-cell interactions in a novel in vitro system supporting the life cycle of blood-borne hepatitis C virus,HEPATOLOGY, Issue 3 2009Hussein Hassan Aly We developed an in vitro system that can be used for the study of the life cycle of a wide variety of blood-borne hepatitis C viruses (HCV) from various patients using a three-dimensional hollow fiber culture system and an immortalized primary human hepatocyte (HuS-E/2) cell line. Unlike the conventional two-dimensional culture, this system not only enhanced the infectivity of blood-borne HCV but also supported its long-term proliferation and the production of infectious virus particles. Both sucrose gradient fractionation and electron microscopy examination showed that the produced virus-like particles are within a similar fraction and size range to those previously reported. Infection with different HCV strains showed strain-dependent different patterns of HCV proliferation and particle production. Fluctuation of virus proliferation and particle production was found during prolonged culture and was found to be associated with change in the major replicating virus strain. Induction of cellular apoptosis was only found when strains of HCV-2a genotype were used for infection. Interferon-alpha stimulation also varied among different strains of HCV-1b genotypes tested in this study. Conclusion: These results suggest that this in vitro infection system can reproduce strain-dependent events reflecting viral dynamics and virus-cell interactions at the early phase of blood-borne HCV infection, and that this system can allow the development of new anti-HCV strategies specific to various HCV strains. (HEPATOLOGY 2009.) [source] Crystallization effects on autoclave foaming of polycarbonate using supercritical carbon dioxideADVANCES IN POLYMER TECHNOLOGY, Issue 4 2006L. Mascia Abstract In this study, the conditions leading to the formation of cells and to the onset of crystallization of polycarbonate were examined with the use of supercritical carbon dioxide for the production of foams from preforms. Small plaques cut from extruded sheets were treated with supercritical carbon dioxide in an autoclave at temperatures varying from 60 to 200°C and from 4.5 to 30 MPa pressure. Visual observations and stereoscan electron microscopy examination revealed that penetration of supercritical carbon dioxide takes place via the advancing layer mechanism and that, for the particular grade of polycarbonate used in this study, the nucleation of the cells can take place at temperatures as low as 60°C. It requires, however, long treatment times and high pressures, and the growth of foam cells is severely restricted. Nucleation and growth of cells occurred much more readily at somewhat higher temperatures. With treatments at around 80°C, the onset of crystallization started to impose considerable hindrance to the formation of uniform and evenly distributed cells. This becomes increasingly evident at higher temperatures, between 100 and 180°C, owing to the formation of large spherulitic crystalline domains. A very effective nucleation and growth mechanism for the formation of cells was obtained, on the other hand, with treatments at 200°C due to the absence of crystallization phenomena. The degree of crystallinity increased with increasing treatment temperature, and the resulting morphology gave rise to two broad melting peaks. These are displaced to higher temperatures and become closer, merging into one peak with a low-temperature shoulder. These events were monitored by thermal analysis and wide-angle X-ray diffraction examinations. © 2007 Wiley Periodicals, Inc. Adv Polym Techn 25:225,235, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20075 [source] Laser-Assisted Machining of Damage-Free Silicon Nitride Parts with Complex Geometric Features via In-Process Control of Laser PowerJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2006Yinggang Tian A methodology to achieve optimal operating conditions for laser-assisted machining (LAM) is developed for silicon nitride parts with complex geometric features by applying a three-dimensional, transient thermal model and in-process laser power control. Complex silicon nitride parts are successfully produced by the LAM operation, where the maximum and material removal temperatures are carefully designed and controlled to achieve good machining results and avoid thermal damage on the final part. On-line temperature and laser power measurements are conducted and compared with prescribed values to show the effectiveness of the power control scheme. Scanning electron microscopy examination reveals virtually no subsurface microcrack or thermal damage on the silicon nitride parts. The X-ray diffraction (XRD) study shows the preservation of the silicon nitride microstructure and no phase transformation of ,-Si3N4 during the LAM experiments. XRD residual stress measurements show moderate compressive residual stresses on the silicon nitride workpieces produced by the LAM operation. [source] Fracture behaviour of cracked carbon nanotube-based polymer composites: Experiments and finite element simulationsFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 2 2010Y. KURONUMA ABSTRACT This paper studies the fracture behaviour of cracked carbon nanotube (CNT)-based polymer composites by a combined numerical,experimental approach. Tensile tests were conducted on single-edge cracked plate specimens of CNT/polycarbonate composites at room temperature and liquid nitrogen temperature (77 K), and the critical loads for fracture instabilities were determined. Elastic,plastic finite element simulations of the tests were then performed to evaluate the,J -integrals corresponding to the experimentally determined critical loads. Scanning electron microscopy examinations were also made on the specimen fracture surfaces, and the fracture mechanisms of the CNT-based composites were discussed. [source] Synthesis of Nanotube Array Composed of an Amorphous Matrix Embedded with NaCl-Type SiC Crystallites by Chemical Vapor Infiltration TechniquesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2010Wen Yang Highly dense oriented arrays of nanotubes were synthesized via a chemical vapor infiltration process using anodic alumina membrane as a template. The nanotubes have a unique granular structure, which is composed of SiC nanocrystals embedded in an amorphous matrix. X-ray diffraction and high-resolution transmission electron microscopy examinations both indicate an NaCl-type crystalline structure of the SiC nanocrystals in the nanotubes. The process described here can be extended to the preparation of other nanomaterials that are suitable to be obtained via a vapor,solid approach. [source] Synthesis and Characterization of Nanoscaled Cerium (IV) Oxide via a Solid-State Mechanochemical MethodJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2006Jun Lu Solid-state reactions have the potential for direct preparation of ceramic powders and offer a low-temperature and low-cost alternative to conventional techniques for production of oxide powders. This paper describes a simple and effective mechanochemical method based on solid-state reactions during ball milling for synthesis of nanoscaled ceria (CeO2) particles. By using an organic base instead of an inorganic base, metal-ion-free nanoscaled CeO2 can also be made. The effects of annealing temperature on particle sizes and lattice strain are investigated. The results show that the average particle sizes of the particles increases and the average crystal lattice distortion decreases with the annealing temperature. Transmission electron microscopy examinations demonstrate that the CeO2 particles synthesised by this method are near-spherical shaped. [source] | |||||||||||||