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Cross striation in human permanent and deciduous enamel measured with confocal Raman microscopy
摘要： Dental enamel is the most mineralized tissue in the human body and has a very complex organization. The aim of the present study was to evaluate chemical composition and orientation of crystals in human enamel cross striation using confocal Raman microscope. Slices of teeth were prepared and scanned using a confocal Raman microscope. Cross striation spacing was calculated according to the variation of PO4 3? peak intensity. The measurements showed a characteristic length between two cross striations of 2.70 (SD 0.43) μm for permanent teeth and 1.75 (SD 0.37) for deciduous teeth. Ratios between OH and PO4 3? peaks, for 0 and 90 degrees angulation, are, respectively, 9.18 (SD 0.80) and 44.74 (SD 3.12) for decidual teeth, and 11.72 (SD 1.46) and 22.12 (SD 3.15) for adult teeth. This confirmed that the hydroxyapatite crystal is well oriented along the enamel prism, as reported in the literature, but with a significant increase in deciduous teeth. K‐mean cluster binary images were calculated to compare the ratio of the centroid peaks of the cross striation zone and inter cross striation material. The regions corresponding to inner prism, included cross striations, are more mineralized than the outer part of enamel prism. In the prism, the Pearson correlation test was performed based on the intensity of hydroxyapatite characteristic peaks (ν1 PO4 3?, ν1 CO3 2?, and OH). The variations were well correlated: These results indicated that cross striations corresponded to the variation of hydroxyapatite concentration and not to a variation of crystals orientation.
关键词： Raman microscopy,cross striation,enamel prism,K‐mean cluster analysis,decidual teeth
更新于2025-09-23 15:23:52
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Understanding the Surfaces and Crystal Growth of Pyrite FeS2
摘要： Pyrite is a common sulfide mineral, which has arisen early interest by its euhedral shape and by its metallic glow similar to gold. However, it is only in our century that we began to understand pyrite crystal growth, considering the thermodynamic and kinetic aspects of crystal formation as a function of temperature and concentration of the elements present in the medium. This article reports an analysis by molecular mechanics of 11 surfaces associated to observed morphologies in order to explain the growth of natural and synthesized minerals. The lowest surface and attachment energies (respectively 1.04 J/m2 and -20.3 kJ/mol) were obtained for the (001) plane, indicating that it is the most stable surface and that kinetic growth also preferentially occurs on this plane. Less known properties, such as crystal striations along the <100> directions, are also discussed.
关键词： pyritohedron,force field,striation,surface,morphology
更新于2025-09-23 15:21:01
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[Laser Institute of America ICALEO? 2015: 34th International Congress on Laser Materials Processing, Laser Microprocessing and Nanomanufacturing - Atlanta, Georgia, USA (October 18–22, 2015)] International Congress on Applications of Lasers & Electro-Optics - Wavelength effect on striation formation during metal laser cutting
摘要： We develop a study on laser cutting of metals with assist gas jet, the aim is to investigate the effect of the beam wavelength on striation formation. The finite volume method is used to discretize the differential governing conservation equations, which are numerically solved. The interfaces are tracked by implementation of the VOF method, whereas an enthalpic approach allows to take into account the melting and re-solidification phenomena. The results show that the used wavelength may play a role in striation formation.
关键词： laser cutting,metal,assist gas jet,wavelength effect,striation formation
更新于2025-09-16 10:30:52