Further research is necessary to provide a better understanding of the links between unsafe behavior theories and empirical findings, challenge theoretical assumptions, develop new applied theories, and make stronger recommendations.
Among fibers with lignocellulosic origin, Kenaf fiber, because of its advantages and as a sustainable alternative to synthetic fibers has received increasing attention for manufacturing hybrid composites with reasonable acoustical and physical properties. The present study deals with the impact of chemical treatment of Kenaf fibers on the overall properties of hybrid composites fabricated from these fibers. Also, the results from predictive analytical model of sound absorption for these composites were employed for comparison with the experimental findings. Kenaf fibers were treated at room temperature with 6% concentration of sodium hydroxide (NaOH) and 4 h immersion time. Having manufactured the composites with the treated and untreated fibers, the normal sound absorption coefficients and tensile strength properties of these sample composites were determined according to ISO 10534-2 and ASTM C1557 − 14, respectively. The SEM analysis of the treated and untreated fibers revealed that in terms of fiber diameter and morphology the former was thinner and had better surface appearance. The experimental measurement of acoustic absorption coefficients of the composites made of treated fibers demonstrated superior sound absorption properties and tensile strength. The revised empirical models proposed by Delany & Bazley and Garai & Pompoli along with Nelder-Mead simplex method were employed and well predicted the sound absorption coefficients of the sample composites. There was also a fair consistency between the experimental and predicted results.
The new instrument appears to be a valid, reliable and sensitive instrument that will contribute to investigating the root causes of workers' unsafe behaviors, thus promoting safety performance in the construction industry.
Background:Exposure to Air pollution PM10 results in lung inflammation increased risk of lung cancer. Regular aerobic exercise improves the inflammatory status in different lung diseases. However, the effects of long-term aerobic exercise on the pulmonary response to PM10 have not been investigated. Objectives:The present study evaluated the effect of aerobic exercise on the lung inflammatory and risk of lung cancer of rat exposed to PM10 carbon black.Materials and Methods:Twenty four adult male Wistar rats were divided into 4 groups: A: control (without exposure PM10 and aerobic exercise; n = 6), B: aerobic exercise (five times per week for 4 weeks; n = 6), C: exposure to PM10 carbon black (5 mg/m3; per rat; n = 6), D: and aerobic exercise concomitantly with exposure to PM10 carbon black (n = 6). The gene expression of TLR4, NF-κB and TNF-α were analyzed in lung tissue by Real time-PCR. In order to determine the significant differences between groups, one way ANOVA and LSD post hoc and Kruskal-Vallis test were used.Results:Aerobic exercise inhibited the PM10 -induced increase in the gene expression of TLR4, NF-κB and TNF-α. But there was significant different only between B and C groups for TNF-α and NF-κB (P = 0.047, 0.014, respectively).Conclusions:We conclude that four week aerobic exercise presents protective effects in a rat model of PM10 carbon black-induced lung inflammation and risk of lung cancer. Our results indicate a need for human studies that evaluate the lung Responses to aerobic exercise chronically performed in polluted areas.
Exposure to inhalation aerosols and particulate matter (PM) in different concentrations can increase the risk of respiratory, cardiovascular, and other related diseases. The inhalation exposure studies are implemented to assess the biological effects of these hazardous agents in human or animal models, in whole-body (WB) or nose/head-only conditions. Several factors can affect the performance of the inhalation exposure chambers and if left uncontrolled, the results may not be desirable. The current study reviewed the characteristics, structures, and factors affecting the performance of the WB chambers, especially the ones designed for small animal exposure to the PM. At the primary stage, the criteria and the search strategy were determined and the keywords were searched in the scientific electronic databases. Totally, 1051 articles were extracted in the first stage, and finally seven articles were adopted. The technical and design details, materials, coefficient variations (CVs) of concentration, assessment methods, type and number of laboratory animals, procedure, and animals housing conditions were extracted from the selected articles. Then the most desirable WB inhalation exposure chamber was determined based on the criteria for assessing the presented exposure chambers such as the animal housing and least CVs of the concentration in the respiratory zones of the animals under study. It was concluded that the Kimmel design was the best and the most desirable chamber structurally and geometrically, since the concentration of the particle (NaCl) injected into the chamber varied from 3.5% to 5.2%, under standard conditions.
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