PubMed · 7864342
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M F James. 1994. Problem with soda lime.. https://doi.org/10.1111/j.1365-2044.1994.tb04378.x
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The minerals (Mg,Fe)SiO3-ilmenite and -perovskite were identified in the shock-induced veins in the Tenham chondritic meteorite. Both phases are inferred to have transformed from pyroxene at high pressures and temperatures by shock metamorphism. Columnar-shaped ilmenite grains, one of two types of morphologies, have a topotaxial relationship with neighboring pyroxene grains, indicating shear transformation. Granular-shaped perovskite grains showed a diffraction pattern consistent with orthorhombic perovskite, but these grains were not stable under the electron beam irradiation and became amorphous. The higher iron concentration in both phases compared with those experimentally reported may suggest their metastable transition from enstatite because of shock compression.
Energy filtering transmission electron microscopy in combination with energy dispersive X-ray analysis (EDX) and quantumchemical calculations opens new possibilities for elemental and bone analysis at the ultrastructural level. The possibilities and limitations of these methods, applied to botanical samples, are discussed and some examples are given. Ca-oxalate crystals in plant cell vacuoles show a specific C K-edge in the electron energy loss spectrum (EELS), which allows a more reliable identification than light microscopical or cytochemical methods. In some dicots crystalline inclusions can be observed in different cell compartments, which are identified as silicon dioxide or calcium silicate by the fine structure of the Si L2,3-edge. Their formation is discussed on the basis of EEL-spectra and quantumchemical calculations. Examples concerning heavy metal detoxification are given for some tolerant plants. In Minuartia Zn is bound as Zn-silicate in cell walls; Armeria accumulates Cu in leaf idioblasts by chelation with phenolic compounds and Cd is precipitated as CdS/phytochelatin-complexes in tomato.
Death of the dental pulp before completion of root development results in a tooth with an open apex. During endodontic treatment, the open apex makes obturation difficult, because there is no apical stop against which the filling can be packed and condensed. For many years, open apices have been treated by root canal fillings or by periapical surgery with or without a reverse seal. Currently, the conservative approach is preferred over surgical management, to avoid the physical and psychological trauma of surgery to a young patient. Two patients were treated by calcium hydroxide-sterile water paste to promote the apexification of the nonvital teeth with an incompletely formed apex. Normal endodontic preparation of the canal had been carried out in the immature tooth. Radiologic examination after 6 to 9 months showed that the apex of the maxillary incisors was completed by newly formed tissue.