• Advances in nano research
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• v.6 no.3
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• pp.243-255
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• 2018

Polystyrene granules were combined with nanosilver to form a nanocomposite film. One-side migration was conducted to test into three food simulants (3% acetic acid, 10% ethanol and 95% ethanol) at $40^{\circ}C$ temperature on different period of time (2, 4, 6, 8 and 10 days). It was found that, among the simulants, the highest migration amount was obtained with 3% acetic acid, while the 95% ethanol revealed the least migration level. Diffusion coefficients of nanosilver particles into simulants were estimated by inverse simulation using experimental data of concentration variation in the simulants. The finite element method used to solve the mass transfer equation and the numerical results indicates the sameresponse with the experimental data. The numerical results confirmed that the highest diffusion coefficient for acetic acid 3% (1.82E-10 to $1.76E-9m^2\;s^{-1}$) and the lowest diffusion coefficient for ethanol 95% from 2 to 10 days were obtained, respectively. Also, results of diffusion coefficient - concentration relation showed, the diffusion coefficient had in direct correlation with time and concentration. The results indicated that, in the 3% acetic acid, due to the increasing of diffusion coefficient of silver nanoparticles, they are released faster and distributed uniformly.

• Journal of Environmental Health Sciences
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• v.44 no.6
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• pp.524-538
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• 2018

Objective: This study aimed to identify the size distributions of particulate matter emitted during 3D printing according to operational conditions and estimate particle inhalation exposure doses at each respiratory region. Methods: Four types of printing filaments were selected: acrylonitrile-butadiene-styrene (ABS), polylactic acid (PLA), Laywood, and nylon. A fused deposition modeling (FDM) 3D printer was used for printing. Airborne particles between 10 nm and $10{\mu}m$ were measured before, during, and after printing using real-time monitors under extruder temperatures from 215 to $290^{\circ}C$. Inhalation exposures, including inhaled and deposited doses at the respiratory regions, were estimated using a mathematical model. Results: Nanoparticles dominated among the particles emitted during printing, and more particles were emitted with higher temperatures for all materials. Under all temperature conditions, the Laywood emitted the highest particle concentration, followed by ABS, PLA, and nylon. The particle concentration peaked for the initial 10 to 20 minutes after starting operations and gradually decreased with elapsed time. Nanoparticles accounted for a large proportion of the total inhaled particles in terms of number, and about a half of the inhaled nanoparticles were estimated to be deposited in the alveolar region. In the case of the mass of inhaled and deposited dose, particles between 0.1 and $1.0{\mu}m$ made up a large proportion. Conclusion: The number of consumers using 3D printers is expected to expand, but hazardous emissions such as thermal byproducts from 3D printing are still unclear. Further studies should be conducted and appropriate control strategies considered in order to minimize human exposure.

• Nutrition Research and Practice
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• v.2 no.4
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• pp.301-307
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• 2008

This study was aimed to investigate the nutritional status and the role of diabetes mellitus in hemodialysis (HD) patients. Anthropometric, biochemical, and dietary assessments for HD 110 patients (46 males and 64 females) were conducted. Mean body mass index (BMI) was $22.1\;kg/m^2$ and prevalence of underweight (BMI<$18.5\;kg/m^2$) was 12%. The hypoalbuminemia (<3.5 g/dl) was found in 15.5% of the subject, and hypocholesterolemia (<150 mg/dl) in 46.4%. About half (50.9%) patients had anemia (hemoglobin: <11.0 g/dL). High prevalence of hyperphosphatemia (66.4%) and hyperkalemia (43.5%) was also observed. More than 60 percent of subjects were below the recommended intake levels of energy (30-35 kcal/kg IBW) and protein (1.2 g/kg IBW). The proportions of subjects taking less than estimated average requirements for calcium, vitamin $B_1$, vitamin $B_2$, vitamin C, and folate were more than 50%, whereas, about 20% of the subjects were above the recommended intake of phosphorus and potassium. Diabetes mellitus was the main cause of ESRD (45.5%). The diabetic ESRD patients showed higher HMI and less HD adequacy than nondiabetic patients. Diabetic patients also showed lower HDL-cholesterol levels. Diabetic ESRD patients had less energy from fat and a greater percentage of calories from carbohydrates. In conclusion, active nutrition monitoring is needed to improve the nutritional status of HD patients. A follow-up study is needed to document a causal relation between diabetes and its impact on morbidity and mortality in ESRD patients.

• Journal of Ocean Engineering and Technology
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• v.19 no.1 s.62
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• pp.14-19
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• 2005

As a basic study for establishing the input conditions of a forecasting/estimating model, used for deep-sea water drainage to the ocean, this study was carried out as follows: 1) estimating the amount of river discharge and pollutant loads into the developing region of deep sea water in the East Sea, Korea, 2) a field observation of tidal current, vertical water temperature, and salinity distribution, 3) 3-D numerical experiment of tidal current to analyze the physical oceanographic status. The amount of river discharge flowing into this study area was estimated at about $462.7{\times}103 m\^3/day$ of daily mean in 2002. Annual mean pollutant load of COD, TN, and TP were estimated at 7.02 ton-COD/day, 4.06 ton-TN/day, and 0.39 ton/day, respectively. Field observation of tidal current normally shows 20-40cm/sec of current velocity at the surface layer, and it decreases under 20cm/sec as the water depth increases. We also found a stratification condition at around 30m water depth in the observation area. The differences in water temperature and salinity, between the surface layer and the bottom layer, were about 18 C and 0.8 psu, respectively. On the other hand, we found a definite trend of 34 psu salinity water mass in the deep sea region.

• Journal of Microbiology and Biotechnology
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• v.24 no.9
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• pp.1196-1206
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• 2014

A metagenomic fosmid library was constructed using genomic DNA isolated from the gut microflora of Hermetia illucens, a black soldier fly. A cellulase-positive clone, with the CS10 gene, was identified by extensive Congo-red overlay screenings for cellulase activity from the fosmid library of 92,000 clones. The CS10 gene was composed of a 996 bp DNA sequence encoding the mature protein of 331 amino acids. The deduced amino acids of CS10 showed 72% sequence identity with the glycosyl hydrolase family 5 gene of Dysgonomonas mossii, displaying no significant sequence homology to already known cellulases. The purified CS10 protein presented a single band of cellulase activity with a molecular mass of approximately 40 kDa on the SDS-PAGE gel and zymogram. The purified CS10 protein exhibited optimal activity at $50^{\circ}C$ and pH 7.0, and the thermostability and pH stability of CS10 were preserved at the ranges of $20{\sim}50^{\circ}C$ and pH 4.0~10.0. CS10 exhibited little loss of cellulase activity against various chemical reagents such as 10% polar organic solvents, 1% non-ionic detergents, and 0.5 M denaturing agents. Moreover, the substrate specificity and the product patterns by thin-layer chromatography suggested that CS10 is an endo-${\beta}$-1,4-glucanase. From these biochemical properties of CS10, it is expected that the enzyme has the potential for application in industrial processes.

• Environmental Analysis Health and Toxicology
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• v.27
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• pp.12.1-12.8
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• 2012

Objectives: The aim of this study was to identify the health and environmental risk factors of air contaminants that influence environmental and respiratory diseases in Gyeongju, Pohang and Ulsan in South Korea, with a focus on volatile organic compounds (VOCs). Methods: Samples were collected by instantaneous negative pressure by opening the injection valve in the canister at a fixed height of 1 to 1.5 m. The sample that was condensed in $-150^{\circ}C$ was heated to $180^{\circ}C$ in sample pre-concentration trap using a 6-port switching valve and it was injected to a gas chromatography column. The injection quantity of samples was precisely controlled using an electronic flow controller equipped in the gas chromatography-mass spectrometer. Results: The quantity of the VOC emissions in the industrial area was 1.5 to 2 times higher than that in the non-industrial area. With regards to the aromatic hydrocarbons, toluene was detected at the highest level of 22.01 ppb in Ulsan, and chloroform was the halogenated hydrocarbons with the highest level of 10.19 ppb in Pohang. The emission of toluene was shown to be very important, as it accounted for more than 30% of the total aromatic hydrocarbon concentration. Conclusions: It was considered that benzene in terms of the cancer-causing grade standard, toluene in terms of the emission quantity, and chloroform and styrene in terms of their grades and emission quantities should be selected for priority measurement substances.

• Journal of dental hygiene science
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• v.22 no.2
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• pp.99-107
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• 2022

Background: Obesity weakens acquired immunity and causes infection. This study aimed to investigate the relationship between the inflammatory markers in the gingival crevicular fluid and serum and periodontal bacteria in saliva through obesity control for 4 weeks. Methods: Forty-six subjects with a body mass index (BMI) of ≥23 kg/m² stayed in the camp for 4 weeks, followed by exercise and a low salt-low fat diet. Body size measurements, oral examinations, blood, saliva, and gingival crevicular fluid were collected before and after the program. C-reactive protein (CRP) in serum, matrix metalloproteinase (MMP)-8, MMP-9, and interleukin (IL)-1β in the gingival sulcus fluid were measured. After extracting bacterial genomic DNA from saliva, the presence of periodontal bacteria were detected using Taq probe. The relationship of each index before and after the program was analyzed through paired t-test and partial correlation analysis. Results: Campylobacter rectus (Cr) increased after the program, and there was no significant change in other bacteria. Serum CRP and Fusobacterium nucleatum (Fn), Aggregatibacter actinomycetemcomitans, Cr, ratio of Fn, and ratio of Cr had a positive relationship at baseline; however, the relationship was not significant after the program. Ratio of Prevotella intermedia had a positive relationship with MMP-9, MMP-8, IL-1β at baseline. Moreover, the ratio of Treponema denticola and the ratio of Tannerella forsythia showed a positive relationship with MMP-8, MMP-9, and IL-1β. The relationship between the ratio of Porphyromonas gingivalis and IL-1β showed a constant positive relationship at baseline and after the program. Conclusion: Obesity control program in subjects with a BMI of ≥23 kg/m² accompanied by diet and exercise did not affect the changes in periodontal bacteria itself, but changes in the relationship between periodontal bacteria and serum CRP, the relationship between the inflammatory index in the gingival crevicular fluid and periodontal bacteria was observed.

• Safety and Health at Work
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• v.14 no.3
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• pp.303-308
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• 2023

Background: Occupational workers at altitudes are more prone to falls, leading to catastrophic outcomes. Acrophobia, height-related anxiety, and affected executive functions lead to postural instabilities, causing falls. This study investigated the effects of repeated virtual height exposure and training on cognitive processing and height-related anxiety. Methods: Twenty-eight healthy volunteers (age 20.48 ± 1.26 years; mass 69.52 ± 13.78 kg) were recruited and tested in seven virtual environments (VE) [ground (G), 2-story altitude (A1), 2-story edge (E1), 4-story altitude (A2), 4-story edge (E2), 6-story altitude (A3), and 6-story edge (E3)] over three days. At each VE, participants identified occupational hazards present in the VE and completed an Attitude Towards Heights Questionnaire (ATHQ) and a modified State-Trait Anxiety Inventory Questionnaire (mSTAIQ). The number of hazards identified and the ATHQ and mSTAIQ scores were analyzed using a 7 (VE; G, A1, A2, A3, E1, E2, E3) x 3 (DAY; DAY 1, DAY 2, DAY 3) factorial repeated measures analysis of variance. Results: The participants identified the lowest number of hazards at A3 and E3 VEs and on DAY 1 compared to other VEs and DAYs. ATHQ scores were lowest at G, A1, and E1 VEs. Conclusion: Cognitive processing is negatively affected by virtual altitudes, while it improves with short-term training. The features of virtual reality, such as higher involvement, engagement, and reliability, make it a better training tool to be considered in ergonomic settings. The findings of this study will provide insights into cognitive dual-tasking at altitude and its challenges, which will aid in minimizing occupational falls.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2018.04a
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• pp.23-23
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• 2018

본 연구는 참우드풀과 우드풀의 중간형으로 알려진 좀우드풀(Woodsia intermedia Tagawa)의 전엽체 증식 및 포자체 형성을 위한 기내 외 번식조건을 구명하고자 수행되었다. 실험재료는 포자를 발아시켜 획득한 전엽체를 8주 간격으로 계대배양하면서 확보하였다. 전엽체 증식에 적합한 배양조건을 탐색하고자, 전엽체 300mg을 다진 후 배지종류(Knop, 1/4, 1/2 및 1MS)와 배지구성물질(sucrose와 활성탄)의 농도를 달리하여 8주간 배양하였다. 배양실은 온도 $25{\pm}1.0^{\circ}C$와 광도 $30{\pm}1.0{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$(16/8h)로 조절되었다. 연구결과, Knop배지에서 생체중이 2.4g으로 전엽체의 증식이 가장 왕성하였다. 한편 MS계열 배지는 농도에 관계없이 매우 저조한 증식을 보였다. Sucrose는 0.5%를 첨가한 배지에서 생체중의 증가량이 가장 컸으며, 활성탄은 첨가농도에 관계없이 유사한 증식수준을 나타냈다. 포자체 형성에 적합한 토양조건을 확인하고자, 인공토양(원예상토, 피트모스, 펄라이트 및 마사토)의 비율을 달리하여 5종류의 혼합토양을 조성하였다. 혼합토양을 사각분($7.5{\times}7.5{\times}7.5cm$)에 충진하고, 준비된 전엽체 1g을 10초간 분쇄한 다음 토양표면에 분주하여 11주간 재배하였다. 재배환경은 온도 $25{\pm}1.0^{\circ}C$, 광도 $43{\pm}2.0{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$(16/8h) 및 습도 $72{\pm}2.0%$로 조절되었다. 연구결과, 모든 처리구에서 포자체의 형성이 확인되었으며, 특히 원예상토와 마사토를 2:1(v:v)로 혼합한 토양에서 포트당 421.0개의 많은 포자체가 형성되었다. 다음으로 원예상토와 펄라이트를 2:1(v:v)로 혼용한 토양, 원예상토, 피트모스, 마사토를 1:1:1(v:v:v)로 혼합한 토양, 원예상토 단용, 원예상토, 피트모스, 펄라이트를 1:1:1(v:v:v)로 혼합한 토양 순으로 각 228.0, 203.3, 126.8, 91.5개 형성되었다. 따라서 좀우드풀의 포자체를 대량으로 생산하기 위해서는 원예상토와 마사토를 2:1(v:v)로 혼용한 토양에 전엽체를 분주하여 재배하는 방법이 효과적일 것으로 판단된다.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.49 no.2
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• pp.1-8
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• 2012

This paper presents the accelerometer which is a key component of TPMS(Tire Pressure Monitoring System). Generally a piezoresistive accelerometer has characteristics of lower cost, better linearity and better immunity about the environmnet noise than a capacitive one. Three types of piezoresistive accelerometers are degined and simulated using ANSYS program. The best one is a piezoresistive sensor which is supported by four beams located at the center of the edge of the mass after comparing the characteristics of resonant frequency of the three types. Considering the sensor size and a simulated maximum stress and maximum displacement, the length of beams is set as $200{\mu}m$. The size of a piezoresistive accelerometer is $3.0mm{\times}3.0mm{\times}0.4mm$. The sensor output is characterized by measuring the output characteristic depending on angle. As a result the offset voltage of the accelerometer is 43.2 mV and its sensitivity is $42.5{\mu}V/V/g$. The temperature bias drift is measured. The shock durability of the sensor is 1500g and the measuring range is 0 ~ 60 g.