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Used Scanning Electron Microscopy (used + scanning_electron_microscopy)
Selected AbstractsImmobilization of the heavy metals Cd, Cu and Pb in an acid soil amended with gypsum- and lime-rich industrial by-productsEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2004V. Illera Summary In situ stabilization of heavy metals in contaminated soils by the addition of various types of soil amendment is an attractive technique for remediation. We investigated the potential of three industrial by-products (phosphogypsum, red gypsum and dolomitic residue) for boosting the heavy metal sorption capacity of an acid soil (patents pending, Spanish applications no 200201704 and 200201375) by using sorption isotherm experiments. The three by-products were found substantially to increase the retention of lead, cadmium and copper on the solid components of the soil. The increase in lead retention of the soil horizons upon the addition of both phosphogypsum and red gypsum was dominated by the formation of anglesite minerals. The dolomitic residue increased the metal retention capacity of the soil horizons through the precipitation of laurionite-type minerals as well as cadmium and copper hydroxy-chlorides. In addition to the batch sorption study, we used scanning electron microscopy to investigate the metal sorption processes in the soil by the effect of the treatments. Lead was frequently found to be linked to the edge charges of kaolinite minerals. The three metals were found to be associated with organic matter in the Ap horizon treated with the three by-products. Finally, the three metals were found to be associated with undissolved dolomitic residue particles. [source] Cranial neural crest cell migration in the Australian lungfish, Neoceratodus forsteriEVOLUTION AND DEVELOPMENT, Issue 4 2000Pierre Falck SUMMARY A crucial role for the cranial neural crest in head development has been established for both actinopterygian fishes and tetrapods. It has been claimed, however, that the neural crest is unimportant for head development in the Australian lungfish (Neoceratodus forsteri ,), a member of the group (Dipnoi) which is commonly considered to be the living sister group of the tetrapods. In the present study, we used scanning electron microscopy to study cranial neural crest development in the Australian lungfish. Our results, contrary to those of Kemp, show that cranial neural crest cells do emerge and migrate in the Australian lungfish in the same way as in other vertebrates, forming mandibular, hyoid, and branchial streams. The major difference is in the timing of the onset of cranial neural crest migration. It is delayed in the Australian lungfish in comparison with their living sister group the Lissamphibia. Furthermore, the delay in timing between the emergence of the hyoid and branchial crest streams is very long, indicating a steeper anterior-posterior gradient than in amphibians. We are now extending our work on lungfish head development to include experimental studies (ablation of selected streams of neural crest cells) and fate mapping (using fluoresent tracer dyes such as DiI) to document the normal fate as well as the role in head patterning of the cranial neural crest in the Australian lungfish. [source] Electron microscopy evaluation of block needle-related trauma to the tibial nerveACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 4 2010K. S. MACDONALD Background: Direct puncture by a needle is a risk factor for nerve damage. This investigation used scanning electron microscopy (SEM) to attempt to visualize the damage caused by different needles. Method: A 15 cm section of the tibial nerve was removed from the ankle of a patient undergoing below-the-knee amputation. The nerve specimen was punctured perpendicular to the fibers once by each of four needles: an insulated 22 G short-beveled (30°), a 25 G long-beveled Quincke spinal needle, an 18 G Tuohy, and a 25 G Whitacre pencil point. The distal and proximal ends on either side of the needles were marked and the nerve was sectioned into 0.5 cm pieces. Each sample was preserved and then prepared for SEM. The needle tract was observed for evidence of mechanical damage at magnifications between × 47 and × 102 using SEM. Results: The epineurium, perineurium, fascicles, endoneurium, and vessels were identified in each sample. In both the short-beveled and the Whitacre samples, all fascicles along with the surrounding perineurium were intact. In both the Tuohy and the Quincke samples, obvious transection of fascicles and disruption of the perineurium were observed. Conclusions: This investigation suggests that both the Tuohy and the Quincke needles may be more likely to cause trauma to the tibial nerve than either the short-beveled or the Whitacre needles. [source] Dense fimbrial meshwork enhances Porphyromonas gingivalis adhesiveness: a scanning electron microscopic studyJOURNAL OF PERIODONTAL RESEARCH, Issue 2 2007H. Hongo Background and Objective:, The aim of this study was to determine how the fimbriae of Porphyromonas gingivalis function in plaque formation. Material and Methods:, We used scanning electron microscopy to examine aggregates and hemaggregates of fimbria-rich ATCC33277 (parent) and fimbra-poor OZ6301C (pgmA -knockout, mutant) strains of P. gingivalis. We also assessed the hemagglutination activity of the two strains as an indicator of P. gingivalis adhesiveness. Results:, Aggregates of P. gingivalis were composed of bacterial chains and clusters. Rich fimbriae projecting from cells of the parent strain tended to bunch and form a dense meshwork among bacterial cells. In contrast, cells of the mutant strain projected fewer fimbriae and the meshwork was looser. Hemaggregates including cells of the parent strain contained a detached, dense fimbrial meshwork that adhered to erythrocytes. Hemaggregates comprising cells of the mutant strain included bacterial chains and clusters that adhered to erythrocytes by shorter fimbriae than those of the parent strain. The hemagglutination titer of the parent strain was 10-fold higher than that of the mutant strain, although the number of fimbriae per cell of the parent strain was only double that of the mutant strain. Conclusion:, The results indicate that P. gingivalis adhesiveness is prominently enhanced by the dense fimbrial meshwork. Thus, the virulence of P. gingivalis is increased by the presence of rich fimbriae. [source] Corrosion of Borosilicate Sealing Glasses for Molten Carbonate Fuel CellsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2003Maria J. Pascual The development of a new sealant for molten carbonate fuel cells (MCFC) requires a study of the attack of molten carbonates on selected materials. Silica and Pyrex® glasses have better corrosion resistance against molten carbonates than other glasses, but they have unsuitable thermal expansion coefficients. Comparisons have also been made between borosilicate glasses of suitable thermal expansion for sealants for MCFC and silica and Pyrex® glasses. The corrosion kinetics in molten carbonates follows two limiting relations and involves two corrosion mechanisms. The weight loss varied linearly with time, indicating a dissolution of the glass network at short times. Longer times show corrosion, depending on the square root of time, typical of a diffusion mechanism and indicating formation of a protective layer on the surface of the glass. The main crystalline corrosion product is lithium methasilicate. The glass-corrosion rate follows the well-known Arrhenius law. These studies used scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and chemical analysis. A general corrosion mechanism of borosilicate glasses in molten carbonates is proposed. [source] IR and UV laser-induced morphological changes in silicon surface under oxygen atmospherePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2005J. Jiménez-Jarquín Abstract We irradiated silicon (100) wafers with IR (1064 nm) and UV (355 nm) nanosecond laser pulses with energy densities within the ablation regime and used scanning electron microscopy to analyze the morphological changes induced on the Si surface. The changes in the wafer morphology depend both on the incident radiation wavelength and the environmental atmosphere. We have patterned Si surfaces with a single focused laser spot and, in doing the experiments with IR or UV this reveals significant differences in the initial surface cracking and pattern formation, however if the experiment is carried out in O2 the final result is an array of microcones. We also employed a random scanning technique to irradiate the silicon wafer over large areas, in this case the microstructure patterns consist of a "semi-ordered" array of micron-sized cones. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Notochordal intervertebral disc cells: Sensitivity to nutrient deprivationARTHRITIS & RHEUMATISM, Issue 4 2009Thorsten Guehring Objective The nucleus pulposus (NP) of the intervertebral disc develops from the notochord. Humans and other species in which notochordal cells (NCs) disappear to be replaced by chondrocyte-like mature NP cells (MNPCs) frequently develop disc degeneration, unlike other species that retain NCs. The reasons for NC disappearance are unknown. In humans, the change in cell phenotype (to MNPCs) coincides with changes that decrease nutrient supply to the avascular disc. We undertook this study to test the hypothesis that the consequent nutrient stress could be associated with NC disappearance. Methods We measured cell densities and metabolic rates in 3-dimensional cultures of porcine NCs and bovine MNPCs, and we determined survival rates under conditions of nutrient deprivation. We used scanning electron microscopy to examine end plate porosity of discs with NCs and those with MNPCs. Nutrient,metabolite profiles and cell viability were calculated as a function of cell density and disc size in a consumption/diffusion mathematical model. Results NCs were more active metabolically and more susceptible to nutrient deprivation than were MNPCs. Hypoxia increased rates of glycolysis in NCs but not in MNPCs. Higher end plate porosity in discs with NCs suggested greater nutrient supply in keeping with higher nutritional demands. Mathematical simulations and experiments using an analog disc diffusion chamber indicated that a fall in nutrient concentrations resulting from increased diffusion distance during growth and/or a fall in blood supply through end plate changes could instigate NC disappearance. Conclusion NCs demand more energy and are less resistant to nutritional stress than MNPCs, which may shed light on the fate of NCs in humans. This provides important information about prospective NC tissue engineering approaches. [source] | ||||||||||