The aim of this study is to evaluate the effect of PREHEATING on composite resins' mechanical and physical properties. PREHEATING of composite resins positively affects the degree of conversion, viscosity, microleakage, marginal adaptation, microhardness and color change however, the flexural strength is adversely affected.

A comprehensive thermodynamic analysis is used to characterize the exergy destruction rate in any part of the solar air PREHEATING system (SAPHS) and calculate its efficiency. The system consists of a solar evaporator, a heat exchanger to air PREHEATING and an auxiliary pump. A computer simulation program using EES software is developed to model and analyses the SAPHS. The system provides preheated air during the year. The thermodynamic analyses involves the determination of effects of air PREHEATING (APH) heat exchanger pinch point temperature, solar radiation intensity and overall heat loss coefficient of the solar evaporator on the performance of the SAPHS. The result showed that the main source of the exergy destruction is the solar evaporator. In the solar evaporator, 115. 9 kW of the input exergy was annihilated. Other main source of exergy annihilation is the APHHE, at 7. 45 kW. The overall energetic and exergetic efficiencies of the SAPHS were 70. 11% and 9. 766%, respectively.

Background. Due to the effect of pre-heating on the degree of conversion of composite resins and the possible effect on cytotoxicity, the effect of pre-heating of bulk-fill composite resins was investigated on cytotoxicity in this study. Methods. In this study, three different types of composite resin were used, including Tetric N-Ceram Bulk-Fil, Xtrafil, and Xtrabase. From each composite resin, 10 cylindrical samples (5 mm in diameter and 4 mm in height) were prepared, with five samples preheated to 68° C, and the other five samples polymerized at room temperature (25° C). Twenty-four hours after polymerization, cytotoxicity was assessed by MTT assay on human fibroblasts. Statistical analysis of data was carried out with two-way ANOVA and Sidak Post-Hoc. The significance level of the test was determined at 0. 05. Results. There was no statistically significant difference between the mean percentage of cytotoxicity in terms of pre-heating (P>0. 05), but the cytotoxicity of the studied composite resins was significantly different (P<0. 001). The cytotoxicity of Tetric N-Ceram Bulk-fil composite resin was higher than that of the two other composite resins. Conclusion. Pre-heating of bulk-fill composite resin did not affect their cytotoxicity. In addition, the cytotoxicity of different bulk-fill composite resins was not the same.

Background. Due to incomplete polymerization of composite resin restorations, residual monomers adversely affect their mechanical properties and biocompatibility. PREHEATING of composite resins is advised to increase the degree of conversion and reduce monomer elution. This study aimed to analyze the effect of PREHEATING and repeated PREHEATING on the amount of monomer released from a bulk-fill composite resin. Methods. Forty samples were prepared using Filtek One Bulk Fill Restorative composite resin. Samples in one group were fabricated at room temperature, whereas the composite resins in the other groups were cured after 1, 10, or 20 repeated PREHEATING cycles (55 °C), 10 in each group. Eluted urethane dimethacrylate (UDMA) and bisphenol-A-glycidylmethacrylate (BisGMA) monomers were measured with high-performance liquid chromatography (HPLC) 24 hours and 30 days after immersion. The data were evaluated using one-way ANOVA and post hoc Tukey tests. Paired-sample t tests were used to test the differences between time intervals. Results. At both time intervals, the greatest amounts of released BisGMA, UDMA, and total monomers were obtained from the control group, whereas 10 PREHEATING cycles resulted in the least monomer elution. The decrease in monomer elution was not statistically significant after 10 PREHEATING cycles compared with that after one PREHEATING cycle (P>0. 05). The group with 20 PREHEATING cycles showed a greater amount of monomer elution compared to that with 1 and 10 cycles, which was statistically significant (P < 0. 05). The amount of released monomers on day 30 was significantly higher than on day 1 (P<0. 01). Conclusion. PREHEATING of the bulk-fill composite resin was shown to be effective in reducing monomer elution. However, monomer elution was adversely affected after repeated PREHEATING cycles of 20.

Growing worldwide energy demands, the drawbacks of fossil fuels, and global climate change have prompted the creation of sustainable, clean power. One of the viable alternatives to the consumption of fossil fuels is the use of solar energy. Solar photovoltaics (PV) and solar thermal are the most widely accessible solar technology. Hybrid solar systems that make use of Concentrated PV Thermal (CPV/T) technology give an alluring option for the generation of both electrical and thermal energy at the same time. CPV reduces the area of PV receivers while capturing the same amount of solar energy through the use of solar radiation that has been Concentrated on PV cells. However, a notable concern associated with CPV is the elevated temperature of the PV surface, often necessitating the implementation of cooling measures. This problem can be resolved by the implementation of a CPV/T system. Conditions for modeling a novel CPV/T hybrid system embedded Multi Junction Photovoltaic cells (MJPV) and based on Fresnel Lens (FL) have been presented in this research. The Python programming language was utilized to simulate the functioning of a linear concentrated Photovoltaic System (LCPVS). In addition, the influence of cooling fluid and its impact on the efficiency of MJ cells (MJC) were assessed. The findings indicate that the proposed system's average thermal and electrical energy were 7.259 and 3.737 (kWh) respectively. Moreover, the average efficiency of the new design was 34.713% and the amount of potable and hot water has more optimum outcomes.