Authors:P. Melnikov, M. Secco, W. Guimarães, and H. dos Santos
A vitreous form of antimony orthophosphate has been obtained using antimony polyphosphate as a precursor. Morphologically,
it is composed of small uniform grains having ellipsoidal shapes. Prolonged thermal treatment leads to the transformation
into a crystalline variety. According to TG curves, both forms start to evaporate at 920°C without decomposition. Melting
point of crystalline SbPO4 has been determined to be 877°C. Thermomechanical study reveals plastic behavior due to the capacity to flow under shearing
stress. Ceramics formation in the system Sb2O3-SbPO4 is discussed. The presence of glass domains in this system has not been confirmed.
Many wheat species and cultivars, independent of genetic markers of hardness, can produce grain with a vitreous, mealy or mixed appearance. This study analyzed selected chemical and physical differences between kernels with a vitreous and mealy appearance, hand-picked from grain of four winter wheat cultivars cultivated in Poland. Separated fractions were examined for protein content and composition, friabilin presence, carotenoids and total phenolic compounds content, specific kernel density, hardness, as well as kernel surface color. It was found that the ratio of vitreous kernels in the cultivars ranged from 39.18% to 76.28%. Vitreous kernels were darker, slightly heavier and harder than mealy kernels. Additionally, these kernels were more abundant in proteins (an average increase of 2.13%, with variation among cultivars from 0.71% to 2.89%). This type of kernels was also richer in phenolic compounds (on average by 4.02%) and less abundant in carotenoids (on average by 4.53%). Mealy (softer) kernels fractured to a finer flour.
Authors:G. Chiodelli, G. Campari-Vigano′, G. Flor, A. Magistris, and M. Villa
Most optimized vitreous electrolytes are obtained by doping an oxide glass with a salt (MX); the resulting substance has an increased ionic conductivity, but a reduced thermal stability. On the other hand, this paper shows that it is possible to obtain vitreous electrolytes with enhanced electrical and thermal performances by mixing two glass formers. This phenomenon may be called the “mixed anion effect”. The Ag2O∶B2O3∶P2O5 system is shown to offer a very interesting example of such a phenomenon.
The special position occupied by glasses amongst solids is again underlined by their thermal behaviour. This feature was studied using As2Se3 as model glass. The range of transformation characteristic of glass is less sharply defined than the freezing point. In the thermal characterization of glass the former is highly dependent on the rate of heating and the thermal history of the glass. The recrystallization and melting temperatures are subject to corresponding modifications.
Thermochemistry and structural mechanism of crystallization of MgO-Al2O3-SiO2 glasses with TiO2 as crystallization activator were studied. Thermal and HREM investigation proved that near the Tg temperature crystallization is going by rearrangement of glass structure elements and part of its components redistribution
like at disorder — order phase transition in solid bodies. Nanocrystals of Mg-titanate and high quartz structure solid solution
are formed then. Next enstatite and cordierite are crystallizing. Thermochemical and chemical bonds strength analysis indicate
that during multistage crystallization of glasses, kind and order of crystal phase formation, is determined by the glass structure
decomposition progress and its particular components release accompanying increase of temperature. It has been proved that
molar heat capacity change (ΔCp) accompanying the glass transition is the significant measure of degree of changes in the structure of glass preceding crystallization.
Authors:N. Vedishcheva, B. Shakhmatkin, and M. Shultz
The enthalpies of solution in 2 N nitric acid at 298 K were measured for alkali metal borate glasses and crystals. From the data obtained, their enthalpies of formation from the oxides and the heats of crystallization of the glasses were calculated.
, glaucoma, ocular inflammations like uveitis; corneal opacities; haemorrhage in the vitreous, macular, and retinal degenerations; and retinal detachment.
Ophthalmic Disorders in Historical Paintings
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