• Polymer(Korea)
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• v.26 no.4
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• pp.468-476
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• 2002

Oxy-PAN fiber prepared from the preoxidation and saponification of raw PAN fiber is known to elongate and contract when immersed in basic and acidic solutions, respectively. In this study, about 30% elongation in NaOH solution and 30∼50% contraction in HCl solution have been observed. In mechanical test, the mechanical properties of oxy-PAN fiber in the contracted state was stronger than that in the elongated state. These behaviors and mechanical properties are compared to those of living muscle and linear actuator. The change of length in NaOH and HCl solutions is due to switching between a hydrophilic and a hydrophobic structure. Other reasons are exchange of ion and water in/out of oxy-PAN fiber, and osmotic pressure difference associated with relevant ions. Much studies are needed to clarify the effective factors on but the oxy-PAN fiber's elongation/contraction behavior and mechanical properties, but the oxy-PAN fiber perpared in our laboratory has a sufficient potential for application as artificial muscle and linear actuator.

• Polymer(Korea)
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• v.26 no.4
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• pp.492-500
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• 2002

Oxidized-polyacrylonitrile (oxy-PAN) was prepared by oxidation of PAN fiber at $240^{\circ}C$, followed by base catalyzed hydrolysis reaction. The chemical structure of PAN fiber in various pH conditions was characterized by $^{13}C-NMR$ spectroscopy. The characteristic contraction and expansion behavior of oxy -PAN fiber was observed in acidic and basic medium, respectively. In basic condition, water molecules might be absorbed into the fiber with the movement of charge balancing $Na^+$ ion, on the other hand, the water molecules seemed to be expelled in acidic condition to result in contraction. It was also observed that the facile chemical modification occurred due to free diffusion of aqueous reagent into the hydrophilic PAN fiber, and the morphology was affected by pH condition.

• Journal of Environmental Health Sciences
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• v.44 no.4
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• pp.301-314
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• 2018

Objectives: The aim of this study was to introduce the overall progress of exposure assessment to humidifier disinfectant (HD); to present participants' demographic characteristics, exposure characteristics to humidifier disinfectant, and exposure classification; and furthermore to compare those characteristics between survivors and non-survivors. Methods: An assessment of environmental exposure to HD was conducted using modified HD-specific questionnaires that had been previously validated. We analyzed the data from 4,482 participants who had been potentially exposed to HD and had registered with the KEITI (Korea Environmental Industry & Technology Institute) from September 2016 to May 2018 (the fourth survey). Environmental exposure assessments were performed as follows: 1) contact with participants, 2) environmental exposure assessment though face-to-face interviews, 3) assessment review and coding, and 4) exposure rating. Results: Overall, survivors made up 77.1% (3,457 subjects) and non-survivors made up 22.9% (1,025 subjects). When compared with the survivors, non-survivors had a higher proportion of subjects aged >60 years and subjects who answered as suffering lung damage and having purchased HD because it is "Beneficial to health" (p<0.05). For the exposure characteristics compared to survivors, non-survivors had a higher proportion of cases of distance from humidifier to face being less that one meter and the spray direction being toward the face (p<0.05). Overall, respondents who used the "Oxy Ssak Ssak New Gaseupgi Dangbun", "Aekyung Gaseupgi Mate", "Homeplus Gaseupgi Chungjungje", and "E-Mart Gaseupgi Salgyunje" products made up 66.1, 12.3, 4.0, and 3.6%, respectively, and 72.5% of respondents used products with PHMG as the active chemical. When compared with survivors, non-survivors had a higher proportion of use of "Oxy Ssak Ssak New Gaseupgi Dangbun" but a lower proportion of use of products with CMIT/MIT, PGH, or PHMG as the active chemical. Conclusions: This study provided demographic characteristics and exposure assessment for applicants who have been injured by HD. In spite of the limitations of performing past exposure assessment through a questionnaire survey, such as recall bias, useful results may be obtained by comparing survivors with non-survivors. Further studies such as the exposure rating method and so on are necessary to assess past exposure to HD.

• Food Science of Animal Resources
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• v.28 no.2
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• pp.196-203
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• 2008

This study was carried out to investigate the effect of sawdust-bedded thickness in floors (SBTF) of Hanwoo on meat quality of M. longissimus after slaughter. The 7 mon-aged bulls (22 heads) were housed in single sheds ($3{\times}8\;m^2$/animal) bedded with sawdust of 10, 15, and 20 cm thickness for 20 mon prior to slaughter. The M. longissimus from carcasses were then stored at $4{\pm}0.2^{\circ}C$ for 9 d. SBTF had no significant effect on carcass traits and pH, water-holding capacity, drip loss, cooking loss, Warner-Bratzler shear force, aroma pattern with electronic nose, and sensory attributes of beef. The 20 cm group had the highest crude fat and the lowest n6/n3 (p<0.05). At 9 d, the 10cm group showed the highest total reducing ability and the lowest TBARS content (p<0.05). During storage, the 10 and 20 cm groups had lower MetMb content, higher OxyMb content, and redder meat color than the 15 cm group (p<0.05).

• Journal of Environmental Health Sciences
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• v.46 no.4
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• pp.433-443
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• 2020

Objective: This study aimed to introduce the use of humidifier disinfectant (HD) in hospitals based on an on-site investigation. Methods: A preliminary survey and on-site investigation of HD use were conducted in 23 hospitals. Among them, one hospital without previous information on HD use was selected for a pilot investigation; 22 hospitals were selected based on previous documents and exposure statements from parliamentary investigation and exposure assessment regarding HD. Descriptive statistics were used to present distribution and characteristics of HD purchase and HD use in hospitals. Also, details on interviews from the on-site investigation were described. Results: Among the 23 hospitals, a total of ten were confirmed to have purchased and used an HD (nine hospitals) or HD-like product (one hospital). For the purchased HD products, four hospitals reported 'Aekyung Gaseupgi Mate', two hospitals reported 'Oxy Ssakssak New Gaseupgi Dangbun', and one hospital reported 'Homeplus Gaseupgi Chungjungje' (one hospital used three kinds of HD products). One hospital reported an HD-like product and four hospitals were 'Unknown'. For the number of HD products purchased, five hospitals reported '100 or less', two hospitals reported 'More than 100', and three hospitals were 'Unknown'. For each of the ten hospitals, we described detailed characteristics of HD purchase and its exposure status obtained through on-site investigation, including the purchase volume (i.e., number of products), exposure space (i.e., patient's room, staff space), and exposure period. Additionally, a comparison of on-site investigation and parliamentary investigation or exposure assessment regarding HD was reported. Conclusion: This study introduced detailed cases of HD purchase and HD use in hospitals based on an on-site investigation, and our findings revealed a possibility of a considerable volume of HD exposure in various multiuse facilities, including hospitals.