A description, and a possible structure and genetic mechanism for a “gypsum nest”, a very rare speleothem consisting of gypsum needles growing from a drying clay massif, are considered. Because of conservation concerns, theoretical modeling is the only acceptable method for studying this complicated and delicate feature. The model suggested considers the “nest” as a screw-dislocated spherocryst...

Surface reproduction was evaluated for epoxy resin and polyether resin dies as well as for gypsum dies by observing the changes in roughness. Significant differences were found by the interaction of the impression and the dies. The resin dies generally showed better results than the gypsum dies when the elastomeric impressions were used. Especially the resin dies were both excellent in surface ...

Organic tofu using organic compatible coagulants of magnesium chloride and three polysaccharides including carrageenan, guar gum and gum Arabic were generated. For MgCl2 coagulated tofu, carrageenan significantly increased the hardness from 969.5 g to 1210.5 g whereas guar gum (0.6g) decreased the hardness to 505.5 g. Interestingly, gypsum and guar gum (0.6g) increased the yield of tofu signifi...

The aim of the present study was to evaluate the dimensional accuracy and surface property of titanium casting obtained using a gypsum-bonded alumina investment. The experimental gypsum-bonded alumina investment with 20 mass% gypsum content mixed with 2 mass% potassium sulfate was used for five cp titanium castings and three Cu-Zn alloy castings. The accuracy, surface roughness (Ra), and reacti...

this study investigated the relationship between clay minerals and different soil moisture regimes in gypsiferous soils of fars province in southern iran. the overall climate of the province is arid and semi-arid and, under this condition, parent material is the most important factor affecting clay minerals distribution. beside this factor, climate conditions have determining role too. palygors...

The purpose of this study was to synthesize biomaterials from daily dental waste. Since alginate impression material contains silica and calcium salts, we aimed to synthesize calcium silicate cement from alginate impression material. Gypsum-based investment material was also investigated as control. X-ray diffraction analyses revealed that although firing the set gypsum-based and modified inves...

Neutralization of Acidic Sulfur Species by Calcite in Mineral Aerosols Collected in China and Japan Studied by Ca K-Edge X-Ray Absorption Near-Edge Structure Spectroscopy X-ray absorption near-edge structure studies at the calcium K-edge have been used to show that acidic sulfur species in the atmosphere (e.g., H2SO4), mainly released by human activities, can be neutralized by the calcite prese...

A numerical analysis of the evolution with time of an abandoned gypsum mine flooded by water is presented. The lay-out of the problem is shown first, together with the experimental results obtained in laboratory tests on gypsum specimens retrieved from site. An elastic-plastic strain-hardening constitutive model, capable of taking weathering effects into account, is sketched next. A chemo-mecha...

A methodology for calcium sulfate (gypsum) scale control in nanofiltration of saline waters is presented. The methodology involves the use of both theoretically and experimentally determined parameters. Pitzer’s thermodynamic equations for electrolytes are used to determine the gypsum scaling potential of the feed water based on its ionic composition, whereas the extent of concentration polariz...

The internal surface area of hexagonal (soluble) primary anhydrite CaSO4 produced by dehydration of gypsum decreases by about 70 % when the anhydrite is successively subjected to rehydration and dehydration at room temperature in humid air and in vacuum respectively. In the rehydration step, the hemihydrate is formed; its dehydration yields secondary anhydrite. Additional hydration-dehydration ...