Lung function and dust in climbing halls: two pilot studies

In climbing halls, high levels of dust are found because magnesia powder is used to dry hands. Concerns have been raised about possible health effects after reports from asthmatics experiencing worsening of symptoms while or after climbing. We investigated acute and sub-acute effects of climbing in dusty halls on lung function in two pilot studies. The first study examined 109 climbers before and after a climbing activity that lasted at least 1 h. In the second study, 25 climbers from different age classes participated in a 2-day climbing competition. Of these, 24 agreed to take part in our investigation, but only 22 provided valid lung function tests on both days. The climbers underwent lung function tests before the first round of the competition (in the morning), after the second round approximately 3 h later and in the morning of the second day before the competition started again. In the first study, we found acute effects, a decline in lung function immediately after the exposure, likely due to protective reflexes of the bronchial muscles and stronger declines in persons with higher exhaled nitric oxide (NO) pre-climbing. In the second study, we also expected sub-acute effects on the next day due to inflammation. On the first day of the competition (second study), dust levels at a central monitor increased over time in a linear manner. Most of the dust was in the size range between 2.5 and 10 μm and dust levels of particulate matter (PM10) reached 0.5 mg/m

Study on the Storage Stability of High Neutralization Degree Phosphate-Bonded No-Bake Sand

Effect of particle size of Al (OH)3 and Mg-containing modifier of binder and hardener on the dry strength and storage stability of high neutralization degree phosphate-bonded no-bake sand were studied. Results show that particle size of Al (OH)3 has little effect on the dry strength and storage stability when its varieties are 4.552 μ m toothpaste-grade Al (OH)3 and 6.136μm industrial special Al (OH)3, 6.136μm industrial special Al (OH)3 is more appropriate in consideration of cost and source. Adding Mg-containing modifier to binder code 32B8M15B cannot improve the dry strength and storage stability, but adopting compound modifier, 2% fused magnesia powder+2% iron powder+4% copper powder ,can obtain better properties , dry strength can reach 3.022MPa, and the minimum strength is above 1MPa with humidity fluctuation from 21%RH to 60%RH in 18 days.

Study on Antibacterial Efficacy and Catalytic Capability of Nanocrystalline Magnesia

Objective: To study the antibacterial efficacy and the catalytic capability of nanocrystalline magnesia powder(nano-MgO). Methods: The antibacterial efficacy was evaluated in Bacteriostatic circle and the shake flask test and the catalytic capability was evaluated by paraoxon. Results: The nano-MgO had good antibacterial efficacy and highly catalytic capability. The catalytic capability was not influenced by light. When 50mL 20μg/L paraoxon solution was catalyzed by 0.5g nano-MgO for 5min, the disappearance of paraoxon was about 77.9%, and for 60min, the disappearances of them was 99.6％. Conclusion：The nano-MgO had good antibacterial efficacy and highly catalytic capability. Key words: nanocrystalline magnesia , antibacterial efficacy, paraoxon, catalytic degradation

Effect of Molar Ratio of MgO/Al2O3 on the Performance of MgO-Al2O3-Fe2O3 Composite

The MgO-Al2O3-Fe2O3 composite was prepared at 1600°C for 3h with magnesia powder and alumina powder as raw materials and with ferric oxide powder as additive. The effect of the molar ratio of MgO/Al2O3 on the sintering and thermal shock resistance of the composite materials was studied. The results showed that increasing the molar ratio of MgO/Al2O3 could improve the densification of the Al2O3-Fe2O3 composites, with the molar ratio of MgO/Al2O3 increased from 3 to 5, densification of the composites didn't increased but decreased. The optimum molar ratio of MgO/Al2O3 of the Al2O3-Fe2O3 composite is equal to 3, the sample MA-3 exhibits better sintering densification and thermal shock resistance. Its primary crystal phases are spinel and periclase, and less amount of sosoloid 20MgO·19Al2O3·Fe2O3. So, the MgO-Al2O3-Fe2O3 composite is acceptable for application in cement rotary kiln linings and high temperature gas filter support.

Dissolution of Fused Magnesia in Alkaline Solution

This work mainly studied the corrosion and dissolution performance of fused magnesia in alkaline solution . The influences of temperature, time and the concentration of alkaline solution on the weight change and particle morphology of magnesia powder were investigated. The corrosion mechanism and dynamics of the magnesia in alkaline solution were discussed by measuring the weight change and XRD analysis. Above results of dissolution studied of fused magnesia powders in alkaline solution would offer important corrosion information for ceramic bulks.

The Hydration of Magnesium Phosphate Cements: Effect of Powder Characteristics on the Reaction Kinetics

The setting reaction of magnesium phosphate cements starts with water addition to a mixture of ammonium phosphate and magnesium oxide, is very fast and takes place at room temperature (cold setting). Literature shows that controversy is still going on about the reaction mechanism, hence, about the effect on the setting time of factors such as the water/cement ratio or the magnesia specific surface area. This work is focused on the magnesia powder characteristics, which were varied by calcining MgO at temperatures ranging from 900 to 1050°C, for periods of 30 to 60 min. Cement pastes were obtained by mixing MgO and diammonium phosphate with water and setting aids. The pastes were left to set in air and were characterized in terms of mineralogical composition (XRD) and microstructure (SEM). The results obtained show how the combined effect of the magnesia characteristics can be used to control the workability and adjust the setting time.