The chemical changes which occur during the process of carious destruction of enamel are complex due to a number of factors. First, substituted hydroxyapatite, the main component of dental enamel, can behave in a very complex manner during dissolution. This is due not only to its ability to accept substituent ions but also to the wide range of calcium phosphate species which can form following ...

Distinctive sediments containing mostly quartz, kaolinite, and both detrital authigenic hematite goethite blanket ~5000 km of the Atlantic coast Brazil from Rio de Janeiro all way to mouth Amazon River. The represent a significant period continental erosion followed by renewed weathering. Here we present (UTh)/He ages goethites hematites collected six weathering profiles in Espírito Santo, sout...

Abstract The role of nanoparticle gold in the formation deposits has long been debated. Evidence support this process is generally limited to epithermal-, Carlin- and seafloor massive-sulfide-type where nanoparticles are associated with primary fluid related processes. At Kenty orogenic deposit Ontario, Canada, remobilized from early pyrite through secondary coupled dissolution-reprecipitation ...

Thick regoliths developed under tropical climate, namely, laterites, resulting from long-term and pronounced geochemical mineralogical rearrangement of the parent rock in response to environmental changes. Little information is available on timing laterite bauxite formations, especially chronology main weathering episodes responsible for lateritic cover formation Guiana shield. For this purpose...

The global production and consumption of plastics have continued to increase. Plastics degrade slowly, causing persistent environmental pollution Developed waste plastic recycling methods are discussed in this report, with a focus on the dissolution/reprecipitation technique restore low-density polyethene (LDPE) wastes. Aspen HYSYS is used simulate LDPE. Turpentine/petroleum ether (TURP/PetE) c...

Many studies of lignins in solution invoke association and aggregation phenomena to explain their solution behavior (e.g., reprecipitation onto pulp fibers, condensation, etc.). Following their colloidal (apparent) molecular weights in solution as a function of time allows us to explore observable dissociation phenomena. These measurements were carried out using multiple angle laser light scatt...

Ostwald ripening, the interfacial-energy-driven dissolution and reprecipitation of solutes, becomes an increasingly significant problem for nanoparticle formulations. We present the first quantitative study of Ostwald ripening for nanoparticle dispersions. The Lifshitz-Slyozov-Wagner (LSW) theory of particle growth driven by diffusion is applied to study -carotene nanoparticles with sizes of O ...

It is known that fractures are more likely to occur in altered teeth, particularly following restoration or endodontic repair; consequently, it is important to understand the structure of altered forms of dentin, the most abundant tissue in the human tooth, in order to better define the increased propensity for such fractures. Transparent (or sclerotic) dentin, wherein the dentinal tubules beco...