A considerable amount of waste heat is produced by internal combustion engines. Bottoming cycle application of Organic Rankine Cycles (ORC) is one of the promising technologies that recuperates the waste heat of engines. A lot of engine waste heat is released into the environment. There are a lot of working fluids that can be applied in these cycles. As the engine waste heat temperature is extremely high, finding a suitable working fluid, which operates properly in the combined cycle, is challenging. In this paper, the thermodynamic analysis of ten working fluids including cyclohexane, HFE7000, HFE7100, n-hexane, n-pentane, R11, R123, R134a, R141b, and R245fa is conducted to observe the influence of different parameters on the system performance and introduce the most appropriate working fluid. Results indicated that, in the studied ranges, R134a had the best performances since (a) its thermal and exergy efficiencies were 17. 39 % and 17. 34 %, respectively; (b) the thermal efficiency of the engine increased by 9 %, and the net power of the system reached 7. 5 kW. Furthermore, there was about 9 % reduction in fuel consumption. On the other hand, among the studied working fluids, cyclohexane operates as the least suitable one by possessing the minimum amounts.

Background and the purpose of the study: Bifidobacterial strains are excessively sensitive to acidic conditions and this can affect their living ability in the stomach and fermented foods, and as a result, restrict their use as live probiotic cultures. The aim of the present study was to obtain bifidobacterial isolates with augmented tolerance to simulated gastrointestinal condition using cross-protection method.Methods: Individual bifidobacterial strains were treated in acidic environment and also in media containing bile salts and NaCl. Viability of the acid and acid-bile-NaCl tolerant isolates was further examined in simulated gastric and small intestine by subsequent incubation of the probiotic bacteria in the corresponding media for 120 min. Antipathogenic activities of the adapted isolates were compared with those of the original strains. Results and major conclusion: The acid and acid-bile-NaCl adapted isolates showed improved viabilities significantly (p<0.05) in simulated gastric fluid compared to their parent strains. The levels of reduction in bacterial count (Log cfu/ml) of the acid and acid-bile-NaCl adapted isolates obtained in simulated gastric fluid ranged from 0.64-3.06 and 0.36-2.43 logarithmic units after 120 min of incubation. There was no significant difference between the viability of the acid-bile-NaCl-tolerant isolates and the original strains in simulated small intestinal condition except for Bifidobacterium adolescentis (p<0.05). The presence of 15 ml of supernatants of acid-bile-NaCl-adapted isolates and also those of the initial Bifidobacterium strains inhibited pathogenic bacterial growth for 24 hrs. Probiotic bacteria with improved ability to survive in harsh gastrointestinal environment could be obtained by subsequent treatment of the strains in acid, bile salts and NaCl environments.

In this study, the performance of direct absorption solar collector is experimentally investigated using Fe3O4/Silica hybrid nanofluid based on deionized water. First, stability of prepared nanofluids is considered using spectral absorbency method. Then, spectrophotometry method is used for measuring optical properties of nanofluids. A prototype of this new type of collector was built with applicability for solar water heating systems. The procedure of EN 12975-2 standard was used for testing the thermal performance of the collector. Results show that collector efficiency is enhanced by nanofluid concentration, so that collector maximum efficiency is 73.9%, 79.8% and 83.7%using nanofluid with concentration of 500 ppm, 1000 ppm and 2000 ppm, respec/tively. This vaule is 63% using the base fluid as working fluid. Regarding very low volume fractions of nanofluids used in direct absorption solar collectors, the viscosity of the base fluid experience insignificant increase, therefore, pumping power will not increase significsantly. Such increase in efficiency show that direct absorption solar collector performance using hybrid nanofluid is much better than that of using the water at the same operating conditions. Application of stable hybrid nanofluid results in higher conversion efficiency of solar energy to useful energy.

Introduction: Use of an adhesive with a suitable composite resin is an important factor in tooth-colored restorations and increasing marginal sealing ability. The aim of this study was to evaluate the microleakage of various adhesives with composite resins using fluid filtration and dye extraction techniques and assessment of the correlation between these two techniques.Materials and Methods: In this in vitro study, class II cavities were prepared on the proximal surfaces of 48 extracted sound human premolar teeth, measuring 1.5±0.5 mm in gingival width, 4 mm in occluso-gingival height and 1.3 of the inter-cuspal distance in width. The samples were divided into four groups (n=12). Group 1; OptiBond Solo Plus adhesive/Herculite XRV composite resin; Group 2: OptiBond Solo Plus adhesive/Master Dent composite resin; Group 3: Prime & Bond NT adhesive/Herculite XRV composite resin; Group 4: Prime & Bond NT adhesive/Master Dent composite resin. Microleakage was assessed primarily by fluid filtration and then by dye extraction techniques. Data were analyzed with Kruskal-Wallis and Mann-Whitney tests, with Bonferroni correction and Spearman's rho correlation test at 95% confidence interval.Results: The minimum and maximum mean microleakage values were recorded in fluid filtration and dye extraction techniques groups 1 and 4, respectively. There were significant differences between the experimental groups in microleakage with the two methods of leakage assessment (p value=0.001). Spearman's rho revealed a strongly direct correlation between the two methods (r=0.797, p value=0.000).Conclusion: In both methods of microleakage assessment, use of ethanol-based in comparison to acetone-based adhesive resulted in microleakage reduction. Application of light-cured composite resin contrary to self-cured composite resin with both types of adhesives increased marginal sealing ability.

Purpose: Managers are one of the important elements of an organization, for this reason, in order to draw the future of the organization, it is necessary for the planners to specify the conditions of their selection and appointment. Therefore, the current research has been done with the aim of identifying and analyzing the components of selecting future principals.Method: In this research, comparative and benchmarking method is used as a prospective approach. This approach is based on the belief that today's advanced organizations/countries can be considered as a model for the future of another organization/countries in their respective subjects. For this, first, the fields of comparison and benchmarking were determined using Brody's four-step comparison method; then the countries of Canada, Finland, Australia, South Africa, and Japan were selected according to the qualitative balance value in the international advanced TEAMS test, human development index, life quality index(health, instruction, and welfare), education quality index, and other scientific-scholarly indexes; finally, by extracting the criteria for the selection and appointment of principals through content analysis and comparison with Iran, the proposed framework for Iran has been presented.Findings: A total of 61 components for the selection of secondary school principals were identified from among the studies conducted in the selected countries in this article. By extracting the commonalities and differences of each of the components among the countries, it was found that the highest index of manager selection and appointment belongs to Japan and the lowest one is related to Finland.Conclusion: There are similarities between the components of selection of principals of secondary schools in Iran and selected countries. In Iran, special attention should be paid to important components such as adherence to religious principles, appropriate personality traits, creativity and innovation, motivation to develop capabilities, professional growth, power of supervision and accountability, social image, leader skills, and purposefulness and foresight.