• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.33 no.2
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• pp.103-114
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• 2023

Objectives: This study was conducted to evaluate hand-arm vibration (HAV) exposure levels due to the use of power hand tools and to evaluate the determinants in the automobile assembly process. Methods: The exposure level to HAV was evaluated for 30 work lines in five assembly processes (body, engine, chassis, door, and design) that use air-powered tools and battery-powered tools and operate in circulation for two hours. The 2-hr equivalent energy vibration acceleration, A (2), of the task was measured. The 8-hr equivalent energy vibration acceleration, A (8), was estimated in consideration of the number of tasks that can be performed per day by each process. In addition, a survey on the working environment was conducted with workers exposed to vibration. Results: The geometric mean of the HAV exposure level, A (2), for a total of 30 tasks was 2.51 m/s², and one case was 10.30 m/s², exceeding TLV (2hr). The HAV exposure level of A (8) was evaluated from 1.03 m/s² to 5.36 m/s². A (2) showed a statistically significant difference (P<0.01) for each process, and the chassis process (GM=3.90 m/s²) was the highest. The larger the tool size and the longer the tool length, the higher was the vibration acceleration when using a battery-powered tool than an air-powered tool (P<0.01). Battery-powered tool users showed higher dissatisfaction on all items than did air-powered tool users. Conclusions: As a result of this study, it is necessary to implement a program to reduce the HAV exposure levels.

• Korean Journal of Remote Sensing
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• v.39 no.6_2
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• pp.1541-1551
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• 2023

Radiometric calibration is a fundamental step in ocean color remote sensing since the step to derive solar radiance spectrum in visible to near-infrared wavelengths from the sensor-observed electromagnetic signals. Generally, satellite sensor suffers from degradation over the mission period, which results in biases/uncertainties in radiometric calibration and the final ocean products such as water-leaving radiance, chlorophyll-a concentration, and colored dissolved organic matter. Therefore, the importance of radiometric calibration for the continuity of ocean color satellites has been emphasized internationally. This study introduces an approach to improve the radiometric calibration algorithm for the visible bands of the Geostationary Ocean Color Imager-II (GOCI-II) satellite with a focus on stability. Solar Diffuser (SD) measurements were employed as an on-orbit radiometric calibration reference, to obtain the continuous monitoring of absolute gain values. Time series analysis of GOCI-II absolute gains revealed seasonal variations depending on the azimuth angle, as well as long-term trends by possible sensor degradation effects. To resolve the complexities in gain variability, an azimuth angle correction model was developed to eliminate seasonal periodicity, and a sensor degradation correction model was applied to estimate nonlinear trends in the absolute gain parameters. The results demonstrate the effects of the azimuth angle correction and sensor degradation correction model on the spectrum of Top of Atmosphere (TOA) radiance, confirming the capability for improving the long-term stability of GOCI-II data.

• IMMUNE NETWORK
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• v.22 no.2
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• pp.16.1-16.20
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• 2022

The gastrointestinal tract is the first organ directly affected by fasting. However, little is known about how fasting influences the intestinal immune system. Intestinal dendritic cells (DCs) capture antigens, migrate to secondary lymphoid organs, and provoke adaptive immune responses. We evaluated the changes of intestinal DCs in mice with short-term fasting and their effects on protective immunity against Listeria monocytogenes (LM). Fasting induced an increased number of CD103⁺CD11b^- DCs in both small intestinal lamina propria (SILP) and mesenteric lymph nodes (mLN). The SILP CD103⁺CD11b^- DCs showed proliferation and migration, coincident with increased levels of GM-CSF and C-C chemokine receptor type 7, respectively. At 24 h post-infection with LM, there was a significant reduction in the bacterial burden in the spleen, liver, and mLN of the short-term-fasted mice compared to those fed ad libitum. Also, short-term-fasted mice showed increased survival after LM infection compared with ad libitum-fed mice. It could be that significantly high TGF-β2 and Aldh1a2 expression in CD103⁺CD11b^- DCs in mice infected with LM might affect to increase of Foxp3⁺ regulatory T cells. Changes of major subset of DCs from CD103⁺ to CD103^- may induce the increase of IFN-γ-producing cells with forming Th1-biased environment. Therefore, the short-term fasting affects protection against LM infection by changing major subset of intestinal DCs from tolerogenic to Th1 immunogenic.

• Journal of Preventive Medicine and Public Health
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• v.21 no.1 s.23
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• pp.10-20
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• 1988

This study was conducted to compare the maternal charactristics, and birth weight of infants delivered at five different categories of medical facility in Taegu to examine the risk level of pregnant women and children by the medical facility for delivery. The study population included 1,410 pregnant women who delivered a baby at one of nine medical facilities (3 university hospitals, 2 general hospitals, 2 private clinics, 1 midwife clinic, 1 MCH center) in Taegu in April, 1987(April and May, 1987 for K university hospital), Pregnant women were interviewed to ask the age and educational level of woman, payment of medical fee, birth order, delivery method. Birth weight of infant was obtained from medical record. Mean ages of the women delivering at the university hospitals(27.5 years) and at general hospitals(26.7 years) were higher than those at midwife clinic(25.4 years) and at MCH center(26.1 years). Also, mean years of school education were higher in women of university hospitals(12.7 years) and general hospitals (12.2 years) than in women of midwife clinic(9.2 years) and MCH center (9.3 years). The percentages of women covered by the medical insurance were far greater in the university hospitals(78.1%) and general hospitals(82.9%) than in private clinics(44.3%) , midwife clinic(29.1%) and MCH center (5.4%). Infants born at the MCH center were mostly the second birth (47.3%) while 56.0% to 61.7% of infants born at all the other medical facilities were the first birth more women delivering at the university hospitals had history of spontaneous abortion as well as still birth than the women delivering at the other medical facilities. The preform birth rate (11.4%) and low birthweight incidence rates(5.8-13.0%) in university hospitals were significantly higher than those of other medical facilities. Accordingly, c-section rates showed a wide variation among the medical facilities. Study findings revealed that most of women delivering at the university hospitals and general hospitals are in the middle of or upper socio-economic class and obstetrically high risk group regardless of socioeconomic class while the wome delivering at the midwife clinic and MCH center are low risk group of low socioeconomic class. Therefore, the data of a specific medical facility are highly limited in interpretation and can not be generalized.

• Radiation Oncology Journal
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• v.21 no.1
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• pp.66-74
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• 2003

Purpose : The matrix metalloprotelnases (MMPs) are a family of enzymes whose main function is the degradation of the extracellular matrix. Several studies have revealed that MMPs and TIMPS are related to the wound heating process and in photoaging caused by ultraviolet Irradiation. However, the expressions of MMP and TIMP after irradiation have not, to the best of our knowledge, been studied. This study investigates the expressions of MMP-2 and TIMP-2 in rat Intestinal mucosa following irradiation. Materials and Methods : The entire abdomen of Sprague-Dawley rats was irradiated using a single dose method. The rats were sacrificed on day 1, 2, 3, 5, 7 and 14 following irradiation. Histopathological observations were made using hematoxilin & eosin staining. The expressions of MMP-2 and TIMP-2 were examined using immunohistochemistry, Irnrnunoblotting and ELISA. Results : Radiation induced damage associated with atrophic villi, and infiltration of inflammatory cell was observed from the first postirradiation day, and severe tissue damage was observed on the second and the third postirradiation days. An increase in mitosis and the number of regenerating crypts, as evidence of regeneration, were most noticeable on the fifth postirradiation day. From the immunohistochemlstry, the MMP-2 expression was observed from the first postirradiation day, but was most conspicuous on the third and the fifth postirradiation days. The TIMP-2 expression was most conspicuous on the fifth postirradiation day. From the irnrnunoblotting, the MMP-2 expression was strongly positive on the third postirradlatlon day, and that of TIMP-2 showed a strong positive response on the fifth postirradiation day. In ELISA tests, the expressions of MMP-2 and TIMP-2 were increased in the postirradiation groups compared to those of the normal controls, and showed a maximum increase on the fifth postirradiatlon day. These results were statistically significant. Conclusion : The expressions of MMP-2 and TIMP-2 were increased in the intestinal mucosa of the rats following irradiation, and these results correlated with the histopathological findings, such as tissue damage and regeneration. Therefore, this study suggests that MMP-2 and TIMP-2 play roles in the mechanisms of radiation-induced damage and regeneration of intestinal mucosa of rats.

• Childhood Kidney Diseases
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• v.2 no.2
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• pp.118-124
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• 1998

Purpose : There is no specific treatment guidelines for Henoch-$Sch{\ddot{o}}nlein$(HS) nephritis. Therefore we performed this study to observe the effect of long term steroid therapy combined with azathioprine Methods : Treatment protocols; 1) Steroid pulse therapy: methylprednisolon 30 mg/kg/dose, maximum 1 gm, intravenolisly 6 times for alternate day. 2) Oral steroid was given 2 mg/kg/day for 1 month, 1 mg/kg/day for following 1 month and alternate day oral steroid combined with azathioprine 2 mg/kg/day for 2 years. Results : Time period from HSP to onset of HS nephritis was between 2 weeks to 5 months with mean $7.4{\pm}7.4$ weeks. Clinical remission were seen in 4 cases out of 5 ($80\%$). Mean time period with disappearance of proteinuria and microscopic hematuria were $5{\pm}2.4$ month and $13.3{\pm}2.9$ month respectively. On pathologic findings by ISKDC, 3 cases were grade IIIb, 2 cases were grade IV in first kidney biopsies and showed pathologic improvement in follow up tidneybiopsiesafterlyearstreatment. Conclusion : As there is no definitive treatment for HS nephritis so far, our study of long term oral steroid therapy with azathioprine was effective in clinical and histologic aspect. Therefore further study in HS nephritis with in a large group will be needed in the future.

• Korean Journal of Veterinary Research
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• v.37 no.1
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• pp.71-78
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• 1997

This study was designed to investigate the number of the growing and mature follicles following gonadotrophin treatments for superovulation in mature rats. Eighteen mature rats (Sprague-Duwely, initially 190~230gm) were randomly alloted into 3 groups. One group was control group, another FSH-treated group was injected intramuscularly with 0.5 units of follicular stimulating hormone (FSH) / rat, and third PMS and HCG-treated group was intramuscularly injected with 20~25IU of pregnant mare serum (PMS) / rat and then at the 48 hrs later, with 20~25IU of human chorionic gonadotrophin (HCG) / rat. The uteri and ovaries of rats were collected and then were observed grossly and serial sections of paraffin embedding ovaries were stained with H-E. Number of ovarian follicles by following 3 grades of large, middle and small follicles from secondary and tertiary follicles were investigated by LM photography of preparations. Small follicles were classified as secondary follicles of preantral follicles with more than 2 layers of granulosa cells surrounding the oocyte and middle follicles were classified as secondary follicles with early signs of antral cavity or with more than one small cavity on either side of the oocytes and large follicles were classified as tertiary follicles with a single medium sized antral cavity or large well-formed antral cavity. In gross findings, the uteri were slightly swelling in FSH-treated group and markedly swelling or filled with fluid in the uterine lumen in PMS and HCG-treated group. In histological findings, the shape and size of the follicles were diverse in middle and large follicles of FSH-treated group and PMS and HCG-treated group, and proportion of atretic follicles was increased in FSH-treated group and PMS and HCG-treated group than those in control group. The uteri of FSH-treated group and PMS and HCG-treated group were hypertropied or filled with fluid in the lumens and walls of uteri. The wall tissue layers were flattened and their blood and lymph vessels were dilated. The mean number of follicle per ovary in control group were appeared to be $17.1{\pm}5.6$($14.0%{\pm}4.6%$), $37.8{\pm}9.1$($30.9{\pm}7.4%$) and $67.6{\pm}30.1$($55.2{\pm}24.6%$) respectively at large, middle and small follicles and total number of these 3 grade follicles were appeared to be $122.5{\pm}40.0$. The mean number of follicle per ovary in FSH-treated group were appeared to be $22.8{\pm}7.0$($17.4%{\pm}5.3%$), $43.4{\pm}6.6$($33.2{\pm}5.1%$) and $64.5{\pm}13.0$($49.3{\pm}9.9%$) respectively at large, middle and small follicles and total number of these 3 grade follicles were appeared to be $130.7{\pm}16.6$. The mean number of follicle per ovary in PMS and HCG-treated group were appeared to be $29.7{\pm}11.0$($16.3%{\pm}6.0%$), $61.9{\pm}17.2$($33.9{\pm}9.4%$) and $91.1{\pm}28.2$($49.9{\pm}15.4%$) respectively at large, middle and small follicles and total number of these 3 grade follicles were appeared to be $182.6{\pm}32.7$. The above findings reveal that large follicles were increased 29.8% in FSH-treated group and 73.7% in PMS and HCG-treated group than those in control group and in histologic findings, proportion of atretic follicles were more increased in ovaries with more number of more developing follicles.

• Journal of Periodontal and Implant Science
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• v.29 no.3
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• pp.483-509
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• 1999

Biodegradable barrier membrane has been demonstrated to have guided bone regeneration capacity on the animal study. The purpose of this study is to evaluate the effects of cultured calvarial cell inoculated on the biodegradable barrier membrane for the regeneration of the artificial bone defect. In this experiment 35 Sprague-Dawley male rats(mean BW 150gm) were used. 30 rats were divided into 3 groups. In group I, defects were covered periosteum without membrane. In group II, defects were repaired using biodegradable barrier membrane. In group III, the defects were repaired using biodegradable barrier membrane seeded with cultured calvarial cell. Every surgical procedure were performed under the general anesthesia by using with intravenous injection of Pentobarbital sodium(30mg/Kg). After anesthesia, 5 rats were sacrificed by decapitation to obtain the calvaria for bone cell culture. Calvarial cells were cultured with Dulbecco's Modified Essential Medium contained with 10% Fetal Bovine Serum under the conventional conditions. The number of cell inoculated on the membrane were $1{\times}10^6$ Cells/ml. The membrane were inserted on the artificial bone defect after 3 days of culture. A single 3-mm diameter full-thickness artificial calvarial defect was made in each animal by using with bone trephine drill. After the every surgical intervention of animal, all of the animals were sacrificed at 1, 2, 3 weeks after surgery by using of perfusion technique. For obtaining histological section, tissues were fixed in 2.5% Glutaraldehyde (0.1M cacodylate buffer, pH 7.2) and Karnovsky's fixative solution, and decalcified with 0.1M disodium ethylene diaminetetraacetate for 3 weeks. Tissue embeding was performed in paraffin and cut parallel to the surface of calvaria. Section in 7${\mu}m$ thickness of tissue was done and stained with Hematoxylin-Eosin. All the specimens were observed under the light microscopy. The following results were obtained. 1 . During the whole period of experiment, fibrous connective tissue was revealed at 1week after surgery which meant rapid soft tissue recovery. The healing rate of defected area into new bone formation of the test group was observed more rapid tendency than other two groups. 2 . The sequence of healing rate of bone defected area was as follows ； test group, positive control, negative control group. 3 . During the experiment, an osteoclastic cell around preexisted bone was not found. New bone formation was originated from the periphery of the remaing bone wall, and gradually extended into central portion of the bone defect. 4 . The biodegradable barrier membrane was observed favorable biocompatibility during this experimental period without any other noticeable foreign body reaction. And mineralization in the newly formed osteoid tissue revealed relatively more rapid than other group since early stage of the healing process. Conclusively, the cultured bone cell inoculated onto the biodegradable barrier membrane may have an important role of regeneration of artificial bone defects of alveolar bone. This study thus demonstrates a tissue-engineering the approach to the repair of bone defects, which may have clinical applications in clinical fields of the dentistry including periodontics.

• The korean journal of orthodontics
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• v.31 no.3 s.86
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• pp.369-379
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• 2001

The aim of this study was to investigate the periodontal response according to the timing of orthodontic force application after bone graft into the angular bony defect. Nine dogs were divided into three groups, 2, 4, and 6 weeks, according to the timing of orthodontic force application after bone graft. Periodontal angular bony defects were created surgically at the distal aspect of both maxillary third incisors. Two weeks later, flap operation was performed to eliminate inflammation and reference notch was made on the root surface at the level of the bottom of each defect. Demineralized freeze-dried bone was implanted on the left side whereas only debridement was done on the other side. Experimental tooth movement was executed during 8 weeks on both graft and non-graft sides. After 2 weeks of retention period, animals were sacrificed for histologic specimens. The results were obtained as follows 1 New bone formation was more pronounced in the graft side than in the non-grad side in all experimental animals. 2. In the 6-week group, new bone and cementum formation was observed in more than half from the notch to the cemento-enamel junction, and the zone of connective tissue attachment was found without apical migration of junctional epithelium. 3. In the 4-week group, the amount of new bone formation was smaller than in the 6-week group whereas the overall remodeling pattern was similar. 4. New bone formation was confined to around the notch and the junctional epithelium migrated apically to the level of the notch with no connective tissue attachment and cementum formation in the 2-week group. The results of the present study suggest that periodontal response may be influenced by the timing of orthodontic force application after bone graft into angular bony defect.

• The korean journal of orthodontics
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• v.33 no.1 s.96
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• pp.11-20
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• 2003

The purpose of the present study is to evaluate the stress distribution on the length and diameter of the miniscrew and cortical bone width. Three dimensional finite element models were made of diameter 1.2mm, 1.6mm, 2.0mm and length 6.0mm, 8.0mm, 10.0mm, 12.0mm and cortical bone width 1.0mm. Also, another three dimensional finite element models were made of diameter 1.2mm, 1.6mm, 2.0mm and length 8.0mm and cortical bone width 1.0mm, 1.5mm, 2.0mm, 2.5mm. Two-hundred grams horizontal force were applied on the center of the miniscrew head and at that stress distribution and its magnitude had been analyzed by ANSYS, which is three dimensional finite element analysis program. The obtained results were as follows : 1. The comparison of the maximum von-Mises stress in the miniscrew showed that as the diameter increases from 1.2mm to 2.0mm stress has been decreased, while on the same diameter stress was not changed regardless of the length change. 2. The comparison of the maximum von-Mises stress in the cortical and cancellous bone showed that as the diameter increases from 1.2mm to 2.0mm stress has been decreased, while on the same diameter stress was not changed regardless of the length change. 3. In the analysis of the stress distribution in the cortical and cancellous bone, the most of the stress had been absorbed in the cortical bone, and did not transmitted much to the cancellous bone. 4. In the analysis of the maximum von-Mises stress according to the cortical bone width, the same diameter of the miniscrew showed a constant stress value regardless of the cortical bone width change. The above results suggest that the maintenance of the miniscrew is more reliable on diameter than length of the miniscrew.