ABSTRACT
This study aims to improve polyurethane-based coating by modified zirconium oxide and aluminum oxide nanoparticles for preparing thin polymeric heat insulation coatings. In the first step, the nanoparticles were chemically modified with the silane coupling agent. Then, three different weight percent of modified nanoparticles (1, 3, and 5% w/w) were mixed with polyurethane, to prepare the nanocomposites, which were coated on metallic plate samples. Then, these plates are used to measure the radiation heat transfer coefficients, absorption coefficient in a region of short wavelengths (UV/VIS/NIR), the emissivity coefficient, and thermography of the samples in a region of long wavelengths (IR). Results showed that by adding the modified nanoparticles to the polyurethane matrix, absorption was decreased and the emissivity coefficient was increased. According to the thermography results, it was observed that the surface temperature of both samples with 3% w/w of nanoparticles had the minimum temperature compare to others. Minimum heat surface observed for 3% w/w of modified nano zirconium oxide.
ABSTRACT
PURPOSE: Few studies have assessed the relationship between meal skipping with subjective health complaints in children and adolescents. The aim of our study was to determine the association between meal skipping and subjective health complaints in this population. METHODS: A total of 14,400 students aged 7-18 years were selected using multistage stratified cluster sampling method from 30 provinces of Iran. Data were collected as a part of the fifth national school-based surveillance program (CASPIAN-V) in Iran. Information about students' lifestyle, health behaviours, health status and health complaints were gathered through a validated questionnaire. RESULTS: The mean (standard deviation) age of participants was 12.3 (3.2) years old. Breakfast skipping was associated with increased odds of stomachache (OR 1.77, 95% CI 1.56, 2.00), backache (OR 1.68, 95% CI 1.46, 1.92), difficulty in getting to sleep (OR 1.66, 95% CI 1.48, 1.86), feeling nervous (OR 1.59, 95% CI 1.43, 1.76) and irritability (OR 1.29, 95% CI 1.02, 1.25). There were 27, 63, 58 and 107% increase in odds of headache, stomachache, backache and difficulty in getting to sleep by lunch skipping, respectively. While dinner skipping was related to 39, 59 and 52% increase in odds of headache, feeling low and difficulty in getting to sleep, respectively, it was associated with decreased odds of stomachache (OR 0.33, 95% CI 0.25, 0.44). CONCLUSIONS: Our study suggests that meal skipping is associated with some somatic and psychological health complaints among children; therefore, regular meal consumption, at least three times a day, is highly recommended in this population. LEVEL OF EVIDENCE: V, cross-sectional descriptive study.