An evaluation of masking nuisance odors from a source by chemical and sensory analyses.

There are many products in the market advertised as masking agents used to overpower strong nuisance odors, such as in or around water resource recovery facilities, solid waste processing facilities, landfills, composting sites, and so forth. Very little is known about the chemical component of these masking agents because they are protected by trade secrets. This is a problem for the parties involved, as the process of choosing the most adequate agent for the particular odor source falls into guesswork. This paper demonstrates that it is possible to determine how effective the masking product would be before spending time and resources in trials. It proposes to show this by comparing the Weber-Fechner curves of the odor-causing compounds known to be emitted at the facility with the curves from the potential masking agents prepared in the laboratory using an olfactometer. Several sensorial examples show that when the Weber-Fechner curves of the odorants and those of candidate masking agents are compared, it is possible to define the effectiveness of the masking agent tested. This is a novel use of the Weber-Fechner curves. The results show there is direct correlation between what is observed by a panel with real life odor samples subjected to incremental dilution and the Weber-Fechner odor intensity-odor concentration curve interaction between the odorants involved. Future work characterizing additional potential masking compounds by Weber-Fechner accompanied by odor profiling with dynamic olfactometry should shed light on the definitive effectiveness of this method in predicting masking effects and discovering useful masking compounds. PRACTITIONER POINTS: Weber-Fechner curves provide relationships between odorant concentration and odor intensity. Dynamic olfactometry, in which real-life air samples are sensorially analyzed by the odor profile method after subsequent dilutions, shows that odor masking occurs. Analyzing the Weber-Fechner curves of the odorants present in the dynamic olfactometry test show the existing odorant interactions. It is possible to predict the extent of the masking of potential compounds by comparing Weber-Fechner curves of masking agents against odorants causing nuisance. This methodology could help avoid spending resources in masking field trials that may result in further exacerbating the affected public.

The mediating role of resilience in the relationship between stress and life satisfaction among Chinese medical students: a cross-sectional study.

BACKGROUND: The psychological distress of medical students has been widely acknowledged. However, few studies focused on positive well-being among medical students. The purpose of this study was to investigate related demographic factors of life satisfaction among Chinese medical students, to examine the relationship between stress and life satisfaction among this group of people, and to explore the mediating role of resilience in this relationship. METHODS: This multicenter cross-sectional study was carried out in June 2014. Self-reported questionnaires consisting of Perceived Stress Scale (PSS), Wagnild and Young Resilience Scale (RS-14), Satisfaction with Life Scale (SWLS), as well as demographic section were distributed to students at four medical colleges and universities in Liaoning province, China. A total of 2925 students (effective response rate: 83.6%) became our subjects. Hierarchical linear regression models were used to explore the mediating role of resilience. RESULTS: Among the demographic factors, life satisfaction was significantly different in gender (P = 0.001) and study programs (P < 0.001). Stress was negatively correlated with life satisfaction (r = -0.35, P < 0.01). After adjusting for the demographic factors, stress accounted for 12% of the variance in life satisfaction (ß = -0.34, P < 0.001) while resilience explained an additional 18% of the variance (ß = 0.46, P < 0.001). Resilience functioned as a partial mediator in the relationship between stress and life satisfaction among Chinese medical students. CONCLUSIONS: Both stress and resilience played a big role in life satisfaction among Chinese medical students. Besides reducing perceived stress, the university authorities should adopt evidence-based intervention strategies to enhance their resilience in order to promote life satisfaction among the students.