• Journal of Korean Academy of Oral Health
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• v.41 no.4
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• pp.231-236
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• 2017

Objectives: The objectives of this study were to investigate the changes in bisphenol A (BPA) concentrations in urine from before to after sealant filling and the relationship between BPA and the number of teeth with sealed surfaces. Methods: Thirty-one children aged 6 and 7 years from three elementary schools in Daegu city who did not have any sealant and resin filling were selected as subjects. Urine samples were collected before and after sealant filling until 24 hours, with informed consent from their caregivers. The BPA concentration in all the collected urine samples was analyzed at Seegene Medical. Statistical analysis was performed using the Friedman test, Scheirer-Ray-Hope test, and the repeated-measures generalized linear mixed model of SPSS version 22.0. Results: The BPA concentrations increased from $3.49-{\mu}g/g$ creatinine before to $4.91-{\mu}g/g$ creatinine 2-3 hours later and to $4.15-{\mu}g/g$ creatinine after 24 hours. The more teeth with sealed surfaces, the higher the BPA concentration in children, but the difference was not statistically significant (P>0.05). Conclusions: The BPA concentrations were highest at 2-3 hours after sealant filling and decreased at 24 hours. Exposure to the sealant appears to have a meaningful correlation with the concentration of BPA in the urine of children.

• Journal of the Korean Society of Physical Medicine
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• v.13 no.4
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• pp.139-148
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• 2018

PURPOSE: This study compared the effects of indoor and outdoor environmental changes on the activity of the major lower limb muscles and walking factors in people 40-50 years and those aged older than 70 years. METHODS: Ten middle-aged people in their forties (age:$44.2{\pm}2.7$, BMI:$21.8{\pm}1.8$) and 10 elderly aged more than 70 years (age:$76.4{\pm}5.9$, BMI:$22.2{\pm}1.9$) with a normal walking ability were included. The participants walked 100 m both indoors and outdoors at their own speed. Using a 3D motion analyzer and EMG, the walking speed, angle of the ankle and activity changes of the lower limb muscles were compared. RESULTS: Significant differences in walking speed and peak-plantar flexion angle were observed between the two groups (p<.05). The muscular activity of the gastrocnemius muscle (GCM) was significantly different outdoors in the swing phase between the two groups (p<.05). In the people aged in their forties, the muscular activity of the rectus femoris (RF) was significantly higher outdoors than indoors (p<.05). In the elderly, however, the muscular activity of the RF was lower outdoors than indoors (p<.05). When compared to those in there forties, the muscular activity of the outdoor RF significantly decreased in the elderly group (P<.05). The muscular activity of the biceps femoris (BF) in the elderly decreased significantly outdoors compared to indoors (p<.05). CONCLUSION: For the elderly, increasing the exposure to the new environments or focusing on the performance of repeated movements for gradual speed control and precise movements is required to maintain normal gaits and movements that are less affected by environmental changes.

• Journal of Digital Convergence
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• v.16 no.12
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• pp.441-447
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• 2018

This study aims to develop digital techniques that enable repeated practice of dental radiography using augmented reality technology. A three-dimensional object was fabricated by superimposing a photograph of an adult model and a computed tomography image of a manikin phantom. The system was structured using 106 radiographs such that one of these saved radiographs is opened when the user attempts to take a radiograph on a mobile device. This system enabled users to repeatedly practice at the pre-clinical stage without exposure to radiation. We attempt to contribute to enhancing dental hygienists' competency in dental radiography using these techniques. However, a system that enables the user to actually take a radiograph based on face recognition would be more useful in terms of practice, so additional studies are needed on the topic.

• Journal of Acupuncture Research
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• v.39 no.4
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• pp.310-316
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• 2022

Background: Verbenalin is an iridoid glucoside, which is among the active components of some medicinal herbs such as Verbena officinalis Linn, and Cornus officinalis Siebold and Zucc. Previous studies have confirmed the antioxidant activity and neuroprotective potential of verbenalin. To confirm the safety of verbenalin, an approximate lethal dose was determined based on a single oral dose toxicity study. Methods: Institute of Cancer Research mice were randomly assigned to three verbenalin exposure groups (250, 500, and 1,000 mg/kg) and a control group (5% methylcellulose solution). There were (5 male and 5 female mice per group). Mortality, clinical signs, and body weight were monitored for 14 days, and necropsies were conducted. Results: No mortalities were observed in the control group or the verbenalin 250 mg/kg group, whereas mortalities were observed in the 500 mg/kg and 1,000 mg/kg verbenalin groups. During the observation period, stool abnormalities such as mucous stools were observed. Clinical signs such as loss of locomotor activity were observed in the 500 mg/kg and 1,000 mg/kg verbenalin groups. During the study period, significant changes in body weight were observed in the 500 mg/kg and 1,000 mg/kg verbenalin groups; however, no gross abnormalities were observed at necropsy. Overall, no toxicity was found in the 250 mg/kg group. Conclusion: The approximate lethal dose of verbenalin was estimated to be 500 mg/kg. For a more accurate assessment of the safety of verbenalin, other types of studies such as repeated-dose toxicity studies should also be conducted.

• Journal of Microbiology and Biotechnology
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• v.33 no.5
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• pp.634-643
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• 2023

Chronic obstructive pulmonary disease (COPD), one of the leading causes of death worldwide, is caused by repeated exposure to harmful matter, such as cigarette smoke. Although Lilium longiflorum Thunb (LLT) has anti-inflammatory effects, there is no report on the fermented LLT bulb extract regulating lung inflammation in COPD. Thus, we investigated the protective effect of LLT bulb extract fermented with Lactobacillus acidophilus 803 in COPD mouse models induced by cigarette smoke extract (CSE) and porcine pancreas elastase (PPE). Oral administration of the fermented product (LS803) suppressed the production of inflammatory mediators and the infiltration of immune cells involving neutrophils and macrophages, resulting in protective effects against lung damage. In addition, LS803 inhibited CSE- and LPS-induced IL-6 and IL-8 production in airway epithelial H292 cells as well as suppressed PMA-induced formation of neutrophil extracellular traps in HL-60 cells. In particular, LS803 significantly repressed the elevated IL-6 and MIP-2 production after CSE and LPS stimulation by suppressing the activity of the nuclear factor kappa-light-chain-enhancer of activated B (NFκB) in mouse peritoneal macrophages. Therefore, our results suggest that the fermented product LS803 is effective in preventing and alleviating lung inflammation.

• Steel and Composite Structures
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• v.46 no.3
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• pp.385-401
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• 2023

Steel is becoming increasingly popular due to its high strength, excellent ductility, great assembly performance, and recyclability. In reality, steel structures serving for a long time in atmospheric, industrial, and marine environments inevitably suffer from corrosion, which significantly decreases the durability and the service life with the exposure time. For the mechanical properties of corroded steel, experimental studies are mainly conducted. The existing numerical analyses only evaluate the mechanical properties based on corroded morphology at the isolated time-in-point, ignoring that this morphology varies continuously with corrosion time. To solve this problem, the relationships between pit depth expectation, standard deviation, and corrosion time are initially constructed based on a large amount of wet-dry cyclic accelerated test data. Successively, based on that, an in-situ pitting evolution method for evaluating the residual tensile strength of corroded steel is proposed. To verify the method, 20 repeated simulations of mass loss rates and mechanical properties are adopted against the test results. Then, numerical analyses are conducted on 135 models of corrosion pits with different aspect ratios and uneven corrosion degree on two corroded surfaces. Results show that the power function with exponents of 1.483 and 1.091 can well describe the increase in pit depth expectation and standard deviation with corrosion time, respectively. The effect of the commonly used pit aspect ratios of 0.10-0.25 on yield strength and ultimate strength is negligible. Besides, pit number ratio α equating to 0.6 is the critical value for the strength degradation. When α is less than 0.6, the pit number increases with α, accelerating the degradation of strength. Otherwise, the strength degradation is weakened. In addition, a power function model is adopted to characterize the degradation of yield strength and ultimate strength with corrosion time, which is revised by initial steel plate thickness.

• Journal of the Korean Society of Radiology
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• v.17 no.6
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• pp.819-825
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• 2023

In this study, among chest CT examination conditions, the tube voltage was changed to 100 and 80 kVp and the reconstruction algorithm was changed to FBP, ASIR-V, and DLIR to compare and analyze changes in examination dose and image quality. As a result, when applying ASIR-V and DLIR at a tube voltage of 100 kVp, which is lower than the existing tube voltage, the dose is lowered while achieving image quality most similar to that when applying 120 kVp and FBP. especially, DLIR reconstructed images had excellent SNR and CNR at all tube voltages. In addition, the SSIM index was analyzed to be closest to 1, showing the highest similarity to the original image. Therefore, when performing repeated chest CT examinations, the application of DLIR can reduce the examination dose by about 29.7%, which is expected to help solve some of the biggest problems with CT examinations, namely radiation exposure due to the examination.

• Journal of Environmental Health Sciences
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• v.49 no.6
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• pp.295-304
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• 2023

Background: Adolescents are relatively more sensitive than adults to exposure to indoor pollutants. The indoor air quality in classrooms where students spend time together must therefore be managed at a safe level because it can affect the health of students. Objectives: In this study, three types of green-wall models were applied to classrooms where students spend a long time in a limited space, and the resulting effects on reducing PM were evaluated. Methods: In the middle school classrooms which were selected as the experimental subjects, IoT-based indoor air quality monitoring equipment was installed for real-time monitoring. Three types of plant models (passive, active, and active+light) were installed in each classroom to evaluate the effects on improving indoor air quality. Results: The concentration of PM in the classroom is influenced by outdoor air quality, but repeated increases and decreases in concentration were observed due to the influence of students' activities. There was a PM reduction effect by applying the green-wall model. There was a difference in PM reduction efficiency depending on the type of green-wall model, and the reduction efficiency of the active model was higher than the passive model. Conclusions: The active green-wall model can be used as an efficient method of improving indoor air quality. Additionally, more research is needed to increase the efficiency of improving indoor air quality by setting conditions that can stimulate the growth of each type of plant.

• The korean journal of orthodontics
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• v.54 no.3
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• pp.153-159
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• 2024

Objective: This study aimed to assess the effects of commonly consumed hot drinks on the force decay of orthodontic elastomeric chains. Methods: This in vitro experimental study evaluated 375 pieces of elastomeric chains with six rings placed on a jig. Four rings were stretched by 23.5 mm corresponding to the approximate distance between the canine and the second premolar. Fifteen pieces served as reference samples at time zero, and 360 pieces were randomized into four groups: control, hot water, hot tea, and hot coffee. Each group was further divided into six subgroups (n = 15) according to the different exposure periods. The specimens in the experimental groups were exposed to the respective solutions at 65.5℃ four times per day for 90 seconds at 5-second intervals. The control group was exposed to artificial saliva at 37℃. The force decay of the samples was measured at 1, 2, 7, 14, 21, and 28 days using a universal testing machine. Data were analyzed using repeated-measures analysis of variance. Results: Maximum force decay occurred on day 1 in all groups. The minimum force was recorded in the control group, followed by the tea, coffee, and hot water groups on day 1. At the other time points, the minimum force was observed in the tea group, followed by the control, coffee, and hot water groups. Conclusions: Patients can consume hot drinks without concern about any adverse effect on force decay of the orthodontic elastomeric chains.

• Progress in Medical Physics
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• v.26 no.1
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• pp.28-35
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• 2015

In this study, we investigated the effects of an iterative reconstruction algorithm and an automatic exposure control (AEC) technique on image quality and radiation dose through phantom experiments with coronary computed tomography (CT) angiography protocols. We scanned the AAPM CT performance phantom using 320 multi-detector-row CT. At the tube voltages of 80, 100, and 120 kVp, the scanning was repeated with two settings of the AEC technique, i.e., with the target standard deviations (SD) values of 33 (the higher tube current) and 44 (the lower tube current). The scanned projection data were reconstructed also in two ways, with the filtered back projection (FBP) and with the iterative reconstruction technique (AIDR-3D). The image quality was evaluated quantitatively with the noise standard deviation, modulation transfer function, and the contrast to noise ratio (CNR). More specifically, we analyzed the influences of selection of a tube voltage and a reconstruction algorithm on tube current modulation and consequently on radiation dose. Reduction of image noise by the iterative reconstruction algorithm compared with the FBP was revealed eminently, especially with the lower tube current protocols, i.e., it was decreased by 46% and 38%, when the AEC was established with the lower dose (the target SD=44) and the higher dose (the target SD=33), respectively. As a side effect of iterative reconstruction, the spatial resolution was decreased by a degree that could not mar the remarkable gains in terms of noise reduction. Consequently, if coronary CT angiogprahy is scanned and reconstructed using both the automatic exposure control and iterative reconstruction techniques, it is anticipated that, in comparison with a conventional acquisition method, image noise can be reduced significantly with slight decrease in spatial resolution, implying clinical advantages of radiation dose reduction, still being faithful to the ALARA principle.