Analysis of the effects of some surface preparation methods on the bond strength of orthodontic attachments to amalgam surface

This in-vitro research was aimed to examine the shear bond strength of metal brackets to silver amalgam using various surface preparation techniques to determine the best method to achieve appropriate bond strength between bracket and amalgam surface. Ninety amalgam blocks were divided into six groups and randomly assigned to one of the following conditioning groups (n=15): group 1 (control): etching with 37% phosphoric acid for 20 seconds, group 2: sand blasting with aluminum oxide (Al2O3), group 3: CO2 laser, group 4: CO2 laser plus sand blast, group 5: Er:YAG laser and group 6:Er:YAG laser plus sandblast. All Bond II was used in all groups and brackets were bonded with Transbond XT. After thermocycling, all samples were tested for shear bond strength by a universal testing machine. Data were analyzed by SPSS-22 software using Kruskal-Wallis and Mann-Whitney tests. The significance level was set at p <= 0.05.The results showed the mean shear bond strength was significantly higher in all five experimental groups than in control group (p <= 0.05). Shear bond strength was significantly higher in CO2 + sandblasting group than in sandblast group, but it was not significantly higher than Er:YAG,Er:YAG + sandblast and CO2 groups. Moreover, the results indicated a significantly higher shear bond strength in Er:YAG group than in sandblast group (p <= 0.05). Preparation by CO2 + sandblast (with mean shear bond strength of 6.3 Mpa) showed a higher shear bond strength than other methods, so it is considered an acceptable preparation method. Keywords:Surface treatment; amalgam; CO2 laser; Er:YAG laser; shear bond strengt

Survey Electrocoagulation Process in Removal of Acid Blue 113 Dye from Aqueous Solutions

Background: Treatment of textile industry wastewaters, due to having color and many pollutants, is one of the most important environmental issues. Acid Blue 113 dyes because of having benzene ring, which is not biodegradable, is toxic and carcinogen. The main objective of this study was determination of electrochemical process efficacy for removal acid blue 113 from aqueous solutions by using aluminum electrodes in batch reactor. Methods: This study performed in lab-scale in batch reactor. The effect of different parameters such as voltages (10, 20, and 40 volt), electrode distance (0.5 and 1 cm), and electrolysis times (5 to 80 min) was investigated. Results: The results of experiments demonstrated that with applying voltage 40V, 0.5 cm distance between electrodes, electrolyte concentration equal to 5 g/l, and 20 minutes electrolysis time, the color and COD removal rate was 99 and 78%, respectively. By increasing voltage and reaction time and reducing distance between the electrodes, power consumption is reduced and also final pH and dye removal efficiency increased. Conclusion: According to the results, the best removal efficiency of dye was obtained after 20 minutes contact time on the electric potential of 40 V, which was 99%. This process is environmental friendly and can be economically acceptable. Therefore, it can be results that electrocoagulation process by using aluminum electrode is an efficient and suitable method for acid blue 113 dye removal from aqueous solutions

Effect of SnO2, ZrO2, and CaCO3 nanoparticles on water transport and durability properties of self-compacting mortar containing fly ash: experimental observations and ANFIS predictions

This paper investigates the influence of the addition of nanoparticles, namely SnO2, ZrO2 and CaCO3, at different doses on the durability and the microstructure of self-compacting mortar (SCM). Rheological characteristics were observed through mini slump flow diameter and mini V-funnel flow time. Transport properties were studied by the water absorption and capillary absorption tests. Mechanical properties were determined by the compression tests. Durability properties were examined by the electrical resistivity and rapid chloride permeability tests. Microstructure of SCMs was investigated through scanning electron microscopy (SEM). The mixtures containing nanoparticles exhibit improved transport properties, with increased compressive strengths and resistance to water and chloride ion penetration. These improvements are attributed to the compact microstructures, as the micro pore system was refined in the presence of nanoparticles. Based on fresh and hardened mortar properties, it is found that 5 wt% SnO2, 4 wt% ZrO2, and 3 wt% CaCO3 would serve as suitable replacement levels in optimizing the overall performance. An adaptive neuro-fuzzy inference system (ANFIS) was employed to predict the SCM properties. The numerical results show that the metamodels provide accurate estimates of experimental results

Diminishing benefits of urban living for children and adolescents’ growth and development

Optimal growth and development in childhood and adolescence is crucial for lifelong health and well-being1–6. Here we used data from 2,325 population-based studies, with measurements of height and weight from 71 million participants, to report the height and body-mass index (BMI) of children and adolescents aged 5–19 years on the basis of rural and urban place of residence in 200 countries and territories from 1990 to 2020. In 1990, children and adolescents residing in cities were taller than their rural counterparts in all but a few high-income countries. By 2020, the urban height advantage became smaller in most countries, and in many high-income western countries it reversed into a small urban-based disadvantage. The exception was for boys in most countries in sub-Saharan Africa and in some countries in Oceania, south Asia and the region of central Asia, Middle East and north Africa. In these countries, successive cohorts of boys from rural places either did not gain height or possibly became shorter, and hence fell further behind their urban peers. The difference between the age-standardized mean BMI of children in urban and rural areas was <1.1 kg m–2 in the vast majority of countries. Within this small range, BMI increased slightly more in cities than in rural areas, except in south Asia, sub-Saharan Africa and some countries in central and eastern Europe. Our results show that in much of the world, the growth and developmental advantages of living in cities have diminished in the twenty-first century, whereas in much of sub-Saharan Africa they have amplified