The aim of the current study is to investigate the effect of different concentrations of Ag nanoparticles on the compressive strength of type IV dental stone. Materials and Methods: Total specimens of this research are 66 specimens, it is divided into 3 groups, the first group is for wet strength , second group is for dry strength and third group is for scanning electron microscope analysis. 0.2%, 0.5% ,1.0% ,1.5% and 2.0% weight of Ag NPs incorporated into type IV dental stone then evaluated both wet and dry compressive strength and compared them with the control specimen and investigate it under SEM. The results are analyzed statistically by (Mean ± standard deviation, ANOVA and Duncan's multiple range test). It is considered significant at p ≤ 0.05. Results: the compressive strength is decreased in comparison to the control specimens. This drop in strength value is not significant in wet strength, while significant in dry strength. SEM image exhibited the morphology of both stone crystals and silver NPs and exhibited the distribution of NPs inside the specimens. Conclusions: The study showed that, the incorporation of silver nanoparticles into dental stone reduced the compressive strength property of dental stone and NPs evenly distributed into dental stone.

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Spherical layer quantum dots (SLQDs) attract a great deal of importance, and have various optoelectronics applications due to their outstanding optical and electrical properties. The photoluminescence (PL) and the electroluminescence (EL) spectra of InAs (SLQDs) were investigated theoretically under the presence of external parameters (pressure, temperature, electric field). Existing of both the temperature and the applied electric field lead to a significant decrease in photoluminescence peak energy (red-shift), while an increase existed in presence of applied hydrostatic pressure (blue-shift). Also with increasing the quantum azimuthal number the photoluminescence peak energy increase. In addition, we found no effect on the band shape of the luminescence as a result of existing such parameters. The study indicates the importance of such parameters as fitting parameters for photoluminescence spectra.