Fabrication of transparent lead-free KNN glass ceramics by incorporation method

The incorporation method was employed to produce potassium sodium niobate [KNN] (K0.5Na0.5NbO3) glass ceramics from the KNN-SiO2 system. This incorporation method combines a simple mixed-oxide technique for producing KNN powder and a conventional melt-quenching technique to form the resulting glass. KNN was calcined at 800°C and subsequently mixed with SiO2 in the KNN:SiO2 ratio of 75:25 (mol%). The successfully produced optically transparent glass was then subjected to a heat treatment schedule at temperatures ranging from 525°C -575°C for crystallization. All glass ceramics of more than 40% transmittance crystallized into KNN nanocrystals that were rectangular in shape and dispersed well throughout the glass matrix. The crystal size and crystallinity were found to increase with increasing heat treatment temperature, which in turn plays an important role in controlling the properties of the glass ceramics, including physical, optical, and dielectric properties. The transparency of the glass samples decreased with increasing crystal size. The maximum room temperature dielectric constant (εr) was as high as 474 at 10 kHz with an acceptable low loss (tanδ) around 0.02 at 10 kHz

Study on Mechanisms of Heat Acclimatization Due to Thermal Sweating : Comparison of Heat-tolerance between Japanese and Thai Subjects

Heat tolerance and sweat response to heat load of tropical subjects in Chiang Mai and temperate subjects in Nagasaki were compared under identical conditions. Male students in Chiang Mai (n=10) and in Nagasaki (n=10) volunteered for this study. The Thai subjects were a little shorter and slightly leaner than the Japanese. Heat load was applied on the legs by immersion into hot water (43℃) for 30 min in the room at 26.6℃ and 33%rh. Sublingual (oral) temperature was measured with a thermistor probe and local sweat rate was measured by the capacitance hygrometer-sweat capsule method. Change in oral temperature, sweat onset time and local sweat volume were compared between Japanese and Thai. Initial oral temperatures (36.76±0.11℃ in Japanese, 36.71±0.23℃ in Thai) were identical, and no sweat was observed before heat load. Mean sweat onset time (9.3±2.1 min chest in Japanese, 16.6±5.6 min chest in Thai) were significantly longer and local sweat volume (10.19±5.00 mg/cm^2, chest in Japanese, 1.39±0.91 mg/cm^2, chest in Thai) was significantly smaller in Thai subjects than Japanese, however, oral temperature (37.18±0.32℃) of Thai subjects was kept slightly lower than oral temperature (37.42±0.10℃) of Japanese even under a 30 min heat load. Sweat volume on the abdomen was larger than on the chest in 9 of 10 Thai subjects. On the contrary, sweat volume on the chest was larger than that on the abdomen in 7 of 10 Japanese subjects. These results suggest that heat tolerance of tropical subjects in due to a more efficient evaporative ability due to a greater heat loss brought about by their long term exposure to heat. Furthermore, the habituation phenomenon related to the reduction of thermoregulatory effector mechanisms were also considered so as to clarify the mechanisms of thermal acclimatization

Analysis of the Mechanisms of Heat Acclimatization : Comparison of Heat-tolerance between Japanese and Thai Subjects

In order to clarify the mechanisms of heat acclimatization to tropical climates by permanent residence, changes in oral temperature due to heat load were compared in 10 male subjects in Chiang Mai, Thailand (tropical region) and 10 male subjects in Nagasaki, Japan (temperate region). Mean annual ambient temperature is 16.6℃ in Nagasaki and 25.9℃ in Chiang Mai. The experiments for the Thai subjects were performed in Chiang Mai and those for the Japanese subjects in Nagasaki during each region\u27s hottest months. The constitutional characteristics of the Thai subjects were a little shorter and slightly leaner than the Japanese. After staying at rest in the experimental room at 32℃ and 35% of relative humidity for at least 30 min, the lower legs were immersed into a hot water bath of 43℃ for 30 min. Mean initial oral temperature was 37.06±0.07℃ in Japanese and 37.12±0.05℃ in Thai subjects (P>0.05). Oral temperature rose after heat load and reached to 37.54±0.06℃ and 37.59±0.06℃ in Japanese and Thai subjects (P>0.05), respectively. Although the inhabitants in Chiang Mai were expected to be more acclimatized to heat compared to those in Nagasaki, no significant difference in the oral temperature was found between two groups throughout the experiment. It is speculated that the same rise in oral temperature in both groups of subjects is attributed to a lower sweat rate and an increase of dry heat loss in Thai subjects. In future studies, not only core temperature but also skin temperatures (dry heat loss) and sweat rate (evaporative heat loss) should be measured and analyzed

Human exposure to hydrogen sulphide concentrations near wastewater treatment plants

The hydrogen sulphide (H2S) levels from wastewater treatment plants (WWTPs) in Curitiba, Brazil have been quantified for the first time. H2S generated by anaerobic decomposition of organic matter in WWTPs is a cause for concern because it is an air pollutant, which can cause eye and respiratory irritation, headaches, and nausea. Considering the requirement for WWTPs in all communities, it is necessary to assess the concentrations and effects of gases such as H2S on populations living and/or working near WWTPs. The primary objective of this study was to evaluate the indoor and outdoor concentration of H2S in the neighbourhood of two WWTPs located in Curitiba, as well as its human health impacts. Between August 2013 and March 2014 eight sampling campaigns were performed using passive samplers and the analyses were carried out by spectrophotometry, presenting mean concentrations ranging from 0.14 to 32 μg m− 3. Eleven points at WWTP-A reported H2S average concentrations above the WHO recommendation of 10 μg m− 3, and 15 points above the US EPA guideline of 2 μg m− 3. At WWTP-B the H2S concentration was above US EPA guideline at all the sampling points. The I/O ratio on the different sampling sites showed accumulation of indoor H2S in some instances and result in exacerbating the exposure of the residents. The highest H2S concentrations were recorded during the summer in houses located closest to the sewage treatment stations, and towards the main wind direction, showing the importance of these factors when planning a WWTP. Lifetime risk assessments of hydrogen sulphide exposure showed a significant non-carcinogenic adverse health risk for local residents and workers, especially those close to anaerobic WWTPs. The data indicated that WWTPs operated under these conditions should be recognized as a significant air pollution source, putting local populations at risk