• Journal of Korean Neurosurgical Society
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• v.62 no.4
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• pp.442-449
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• 2019

Objective : Bone mineral density (BMD) is an important consideration during fusion surgery. Although dual X-ray absorptiometry is considered as the gold standard for assessing BMD, quantitative computed tomography (QCT) provides more accurate data in spine osteoporosis. However, QCT has the disadvantage of additional radiation hazard and cost. The present study was to demonstrate the utility of artificial intelligence and machine learning algorithm for assessing osteoporosis using Hounsfield units (HU) of preoperative lumbar CT coupling with data of QCT. Methods : We reviewed 70 patients undergoing both QCT and conventional lumbar CT for spine surgery. The T-scores of 198 lumbar vertebra was assessed in QCT and the HU of vertebral body at the same level were measured in conventional CT by the picture archiving and communication system (PACS) system. A multiple regression algorithm was applied to predict the T-score using three independent variables (age, sex, and HU of vertebral body on conventional CT) coupling with T-score of QCT. Next, a logistic regression algorithm was applied to predict osteoporotic or non-osteoporotic vertebra. The Tensor flow and Python were used as the machine learning tools. The Tensor flow user interface developed in our institute was used for easy code generation. Results : The predictive model with multiple regression algorithm estimated similar T-scores with data of QCT. HU demonstrates the similar results as QCT without the discordance in only one non-osteoporotic vertebra that indicated osteoporosis. From the training set, the predictive model classified the lumbar vertebra into two groups (osteoporotic vs. non-osteoporotic spine) with 88.0% accuracy. In a test set of 40 vertebrae, classification accuracy was 92.5% when the learning rate was 0.0001 (precision, 0.939; recall, 0.969; F1 score, 0.954; area under the curve, 0.900). Conclusion : This study is a simple machine learning model applicable in the spine research field. The machine learning model can predict the T-score and osteoporotic vertebrae solely by measuring the HU of conventional CT, and this would help spine surgeons not to under-estimate the osteoporotic spine preoperatively. If applied to a bigger data set, we believe the predictive accuracy of our model will further increase. We propose that machine learning is an important modality of the medical research field.

• Korean Journal of Metals and Materials
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• v.46 no.11
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• pp.762-769
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• 2008

Hydrogenated amorphous silicon(a-Si : H) layers, 120 nm and 50 nm in thickness, were deposited on 200 $nm-SiO_2$/single-Si substrates by inductively coupled plasma chemical vapor deposition(ICP-CVD). Subsequently, 30 nm-Ni layers were deposited by E-beam evaporation. Finally, 30 nm-Ni/120 nm a-Si : H/200 $nm-SiO_2$/single-Si and 30 nm-Ni/50 nm a-Si:H/200 $nm-SiO_2$/single-Si were prepared. The prepared samples were annealed by rapid thermal annealing(RTA) from $200^{\circ}C$ to $500^{\circ}C$ in $50^{\circ}C$ increments for 30 minute. A four-point tester, high resolution X-ray diffraction(HRXRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and scanning probe microscopy(SPM) were used to examine the sheet resistance, phase transformation, in-plane microstructure, cross-sectional microstructure, and surface roughness, respectively. The nickel silicide on the 120 nm a-Si:H substrate showed high sheet resistance($470{\Omega}/{\Box}$) at T(temperature) < $450^{\circ}C$ and low sheet resistance ($70{\Omega}/{\Box}$) at T > $450^{\circ}C$. The high and low resistive regions contained ${\zeta}-Ni_2Si$ and NiSi, respectively. In case of microstructure showed mixed phase of nickel silicide and a-Si:H on the residual a-Si:H layer at T < $450^{\circ}C$ but no mixed phase and a residual a-Si:H layer at T > $450^{\circ}C$. The surface roughness matched the phase transformation according to the silicidation temperature. The nickel silicide on the 50 nm a-Si:H substrate had high sheet resistance(${\sim}1k{\Omega}/{\Box}$) at T < $400^{\circ}C$ and low sheet resistance ($100{\Omega}/{\Box}$) at T > $400^{\circ}C$. This was attributed to the formation of ${\delta}-Ni_2Si$ at T > $400^{\circ}C$ regardless of the siliciation temperature. An examination of the microstructure showed a region of nickel silicide at T < $400^{\circ}C$ that consisted of a mixed phase of nickel silicide and a-Si:H without a residual a-Si:H layer. The region at T > $400^{\circ}C$ showed crystalline nickel silicide without a mixed phase. The surface roughness remained constant regardless of the silicidation temperature. Our results suggest that a 50 nm a-Si:H nickel silicide layer is advantageous of the active layer of a thin film transistor(TFT) when applying a nano-thick layer with a constant sheet resistance, surface roughness, and ${\delta}-Ni_2Si$ temperatures > $400^{\circ}C$.

• Journal of Preventive Medicine and Public Health
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• v.54 no.6
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• pp.412-421
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• 2021

Objectives: Non-alcoholic fatty liver disease (NAFLD) is an increasingly prevalent metabolic disease. Muscle is known to influence NAFLD development. Therefore, this study aimed to determine the relationships among low muscle mass, NAFLD, and hepatic fibrosis using various definitions of low muscle mass and NAFLD diagnostic methods, including magnetic resonance imaging-based proton density fat fraction (MRI-PDFF). Methods: This cross-sectional study included 320 participants (107 males, 213 females) from the Korean Genome and Epidemiology Study on Atherosclerosis Risk of Rural Areas in the Korean General Population cohort. Muscle mass was assessed using whole-body dual-energy X-ray absorptiometry and adjusted for the height squared, body weight, and body mass index (BMI). NAFLD was diagnosed using ultrasonography (US), MRI-PDFF, and the comprehensive NAFLD score (CNS). Hepatic fibrosis was assessed using magnetic resonance elastography. Multivariable logistic and linear regression analyses were performed to determine the aforementioned associations. Results: According to US, 183 participants (57.2%) had NAFLD. Muscle mass adjusted for body weight was associated with NAFLD diagnosed using US (odds ratio [OR], 3.00; 95% confidence interval [CI], 1.70 to 5.31), MRI-PDFF (OR, 2.00; 95% CI, 1.13 to 3.53), and CNS (OR, 3.39; 95% CI, 1.73 to 6.65) and hepatic fibrosis (males: β=-0.070, p<0.01; females: β=-0.037, p<0.04). Muscle mass adjusted for BMI was associated with NAFLD diagnosed by US (OR, 1.71; 95% CI, 1.02 to 2.86) and CNS (OR, 1.95; 95% CI, 1.04 to 3.65), whereas muscle mass adjusted for height was not associated with NAFLD. Conclusions: Low muscle mass was associated with NAFLD and liver fibrosis; therefore, maintaining sufficient muscle mass is important to prevent NAFLD. A prospective study and additional consideration of muscle quality are needed to strengthen the findings regarding this association.

• Journal of Korean Neurosurgical Society
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• v.65 no.1
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• pp.96-106
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• 2022

Objective : The most common complication of anterior cervical discectomy and fusion (ACDF) is cage subsidence and maintenance of disc height affects postoperative clinical outcomes. We considered cage subsidence as an inappropriate indicator for evaluating preservation of disc height. Thus, this study aimed to consider patients with complications such as reduced total disc height compared to that before surgery and evaluate the relevance of several factors before ACDF. Methods : We retrospectively reviewed the medical records of 40 patients who underwent stand-alone single-level ACDF using a polyetheretherketone (PEEK) cage at our institution between January 2012 and December 2018. Our study population comprised 19 male and 21 female patients aged 24-70 years. The minimum follow-up period was 1 year. Twenty-seven patients had preoperative bone mineral density (BMD) data on dual-energy X-ray absorptiometry. Clinical parameters included sex, age, body mass index, smoking history, and prior medical history. Radiologic parameters included the C2-7 cobb angle, segmental angle, sagittal vertical axis, disc height, and total intervertebral height (TIH) at the preoperative and postoperative periods. Cage decrement was defined as the reduction in TIH at the 6-month follow-up compared to preoperative TIH. To evaluate the bone quality, Hounsfield unit (HU) value was calculated in the axial and sagittal images of conventional computed tomography. Results : Lumbar BMD values and cervical HU values were significantly correlated (r=0.733, p<0.001). We divided the patients into two groups based on cage decrement, and 47.5% of the total patients were regarded as cage decrement. There were statistically significant differences in the parameters of measuring the HU value of the vertebra and intraoperative distraction between the two groups. Using these identified factors, we performed a receiver operating characteristic (ROC) curve analysis. Based on the ROC curve, the cut-off point was 530 at the HU value of the upper cortical and cancellous vertebrae (p=0.014; area under the curve [AUC], 0.727; sensitivity, 94.7%; specificity, 42.9%) and 22.41 at intraoperative distraction (p=0.017; AUC, 0.722; sensitivity, 85.7%; specificity, 57.9%). Using this value, we converted these parameters into a bifurcated variable and assessed the multinomial regression analysis to evaluate the risk factors for cage decrement in ACDF. Intraoperative distraction and HU value of the upper vertebral body were independent factors of postoperative subsidence. Conclusion : Insufficient intraoperative distraction and low HU value showed a strong relationship with postoperative intervertebral height reduction following single stand-alone PEEK cage ACDF.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.32 no.1
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• pp.21-30
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• 2022

Objectives: The purpose of this study is to suggest an optimal method by comparing the analysis methods of work environment measurement datasets including left-censored data where one or more measurements are below the limit of detection (LOD). Methods: A computer program was used to generate left-censored datasets for various combinations of censoring rate (1% to 90%) and sample size (30 to 300). For the analysis of the censored data, the simple substitution method (LOD/2), β-substitution method, maximum likelihood estimation (MLE) method, Bayesian method, and regression on order statistics (ROS)were all compared. Each method was used to estimate four parameters of the log-normal distribution: (1) geometric mean (GM), (2) geometric standard deviation (GSD), (3) 95th percentile (X95), and (4) arithmetic mean (AM) for the censored dataset. The performance of each method was evaluated using relative bias and relative root mean squared error (rMSE). Results: In the case of the largest sample size (n=300), when the censoring rate was less than 40%, the relative bias and rMSE were small for all five methods. When the censoring rate was large (70%, 90%), the simple substitution method was inappropriate because the relative bias was the largest, regardless of the sample size. When the sample size was small and the censoring rate was large, the Bayesian method, the β-substitution method, and the MLE method showed the smallest relative bias. Conclusions: The accuracy and precision of all methods tended to increase as the sample size was larger and the censoring rate was smaller. The simple substitution method was inappropriate when the censoring rate was high, and the β-substitution method, MLE method, and Bayesian method can be widely applied.

• The Korea Journal of Herbology
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• v.32 no.3
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• pp.45-53
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• 2017

Objective : Nelumbo nucifera, its rhizome and semen have been used as a traditional medicine which was studied on antioxidant, hepatoprotective effect, anti-obesity and the others. However, Nelumbinis Flos have not studied. We investigated protective effects on oxidative DNA damage and anti-inflammatory effects of Nelumbinis Flos. Methods : The antioxidant activity was conducted by 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical, 2, 2'-Azino-bis (3-ethylbenzothiazoline-6 sulfonic acid) diammonium salt (ABTS) radical scavenging assay and reducing power assay. Total phenolic content was analyzed. Also, phenolic compounds were detected by HPLC/UV. The inhibitory effect on oxidative DNA damage was determined using ${\Phi}X-174$ RF I plasmid DNA cleavage assay. The anti-inflammatory effect of Nelumbinis Flos was measured by the amount of nitric-oxide (NO) produced and protein levels of iNOS, and COX-2 in LPS induced RAW 264.7 cells. Results : The results of DPPH and ABTS radical scavenging activity at $200{\mu}g/m{\ell}$ of extraction were $97.02{\pm}0.88%$ and $96.42{\pm}0.25%$. Reducing power (fold of L-ascorbic acid as control) was $100.14{\pm}0.31$ at $200{\mu}g/m{\ell}$. Total phenol content was $8.70{\pm}0.02mg/g$. Chlorogenic acid, catechin and epicatechin were found by HPLC. Nelumbinis Flos has inhibitory effect in dose-manner against oxidative DNA damage. In addition, it showed the anti-inflammatory effect by suppression of NO production as well as protein levels of iNOS, and COX-2. Conclusion : This study suggested that Nelumbinis Flos showed potential antioxidant and suppression activities of various factors were related in NO produced. Therefore, Nelumbinis Flos as natural plant resources that may help reduce inflammation and alleviate DNA damage.

• Journal of Periodontal and Implant Science
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• v.52 no.5
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• pp.422-434
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• 2022

Purpose: The purpose of this study was to evaluate and compare the healing patterns of 2-mm and 4-mm proximal infrabony defects adjacent to dental implants in canine mandibles. Methods: Four male beagles were used. Two groups were created: a 2-mm group (n=4) and a 4-mm group (n=4) depending on the horizontal dimension of proximal infrabony defects adjacent to implants. Bone healing patterns between the 2 groups were evaluated and compared at 8 and 16 weeks using radiographic, histological, histomorphometric, and fluorescent labelling analyses. Results: According to microcomputed tomography, the median bone volume fraction, bone mineral density, and the percentage of radiographic distance from the defect bottom to the most coronal bone-to-implant contact (radio-mcBIC) were 32.9%, 0.6 g/cm³, and 73.7% (8 weeks) and 45.7%, 0.7 g/cm³, and 76.0% (16 weeks) in the 2-mm group and 57.7%, 0.8 g/cm³, and 75.7% (8 weeks) and 50.9%, 0.8 g/cm³, and 74.7% (16 weeks) in the 4-mm group, respectively. According to histomorphometry, the median bone area fraction, mcBIC and the percentage of BIC amounted to 36.7%, 3.4 mm, and 58.4% (8 weeks) and 49.2%, 3.4 mm, and 70.2% (16 weeks) in the 2-mm group and 50.0%, 3.0 mm, and 64.8% (8 weeks) and 55.7%, 3.0 mm, and 69.6% (16 weeks) in the 4-mm group, respectively. No statistically significant differences were found between the groups for any variables (P>0.05). Conclusions: The proximal defects that measured 2 mm and 4 mm showed similar healing patterns at 8 and 16 weeks, and the top of bone formation in the defects was substantially limited to a maximum of 1.6 mm below the implant shoulder in both groups.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.6 no.9
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• pp.59-70
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• 2016

The rapid development of the Chinese version of Twitter, the groom Weibo has become an important communication means for Chinese SNS users to obtain and share information. As a result, in China, the phenomenon of the power shift has emerged from the traditional opinion leaders to SNS opinion leasers. The relationship analysis of demographic variables of the Chinese SNS users and their Information on the relationship between keywords was made by utilizing the centrality analysis using Social Network Program NetMiner. China's SNS opinion leaders have general interest in daily activities with their families or friends rather than in social issues. And in case of SNS opinion leaders of high betweenness centrality, it was analyzed that general users was a key mediator role that organically out lead to the adjacent information. These properties are not independent of demographic variables, such as professional, therefore, the demographic characteristics of SNS opinion leaders showed a significant effect on the parameters of betweenness centrality. This study analyzed the characteristics of SNS users, especially opinion leaders in China by looking at the aspects of Chinese social phenomenon in terms of information. Through this study, we expect to provide basic information about the social characteristics of China through collective communication.

• Journal of the Korean Society of Food Culture
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• v.21 no.5
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• pp.473-480
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• 2006

The purpose of this study were to investigate middle and high school students' food habits and food attitudes, and to assess student's nutrient consumption. A self-administered questionnaire was developed based on review of literature. The questionnaire consisted of three sections (food habits, food attitudes, and food consumption). The questionnaires were distributed to 4,050 students enrolled in 34 middle and high schools located in Seoul, Gyeonggi, and Gyeongnam provinces. A final response rate was 88.2% (3,570) excluding responses that had significant missing data. Data of the food habits and food attitudes were analyzed with descriptive analysis, $x^2$-test, and t-test using SPSS WIN(ver.11.0). The student's self-reported food consumption data was converted into nutrient consumption using conversion factor. Many middle and high school students skipped breakfast and/or dinner. Approximately 29% of the students did not eat vegetables and fruits. Scores of the middle school student's attitudes(19.1) towards foods were significantly higher than those of the high school student's attitudes(18.7)(p<.001). Student's nutrient intakes were estimated according to the student's self-reported food consumption data. The nutrient intakes were compared with DRIs(Dietary Reference Intakes: DRIs) for their age groups. The result of EAR(Estimated Average Requirement: EAR) cut-point method demonstrated 57.7% of middle school boys, 64.4% of middle school girls, 70.2% of high school boys, and 71.0% of high school girls did not meet EAR for Calcium. Additionally, it showed that 39.0% of middle school boys, 23.7% of middle school girls, 58.4% of high school boys, and 24.4% of high school girls did not consume EAR for Vitamin $B_1$. 25.7% of middle school boys did not meet EAR for Vitamin $B_2$, while 44.4% high school boys did not satisfy EAR for Vitamin $B_2$.

• Economic and Environmental Geology
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• v.56 no.6
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• pp.799-816
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• 2023

Mineralogical and geochemical studies of shales within the Lower Anambra Basin was conducted to unravel the depositional environment, provenance, maturity, paleo-weathering conditions, and tectonic settings. Mineralogical studies conducted using X-ray diffraction analysis revealed that the samples were composed of kaolinite, montmorillonite, chlorite, and illite. KaolinIite is the dominant mineral, constituting approximately 41.5% of the bulk composition, whereas the non-clay minerals are quartz, ilmenite, and sillimanite. Geochemical analysis showed a predominance of SiO₂, Al₂O₃, and Fe₂O₃ contents of the shale samples with mean values of 52.29%, 14.09%, and 6.15% for Imo Shale (IS); 52.31%, 16.70%, and 7.39% for Mamu Shale (MS); 43.21%, 21.33%, and 10.36% for Enugu Shale (ES); 53.35%, 15.64%, and 7.17% for Nkporo Shale (NS); and 51.24%, 17.25%, and 7.78% for Agwu Shale (AS). However, the shales were depleted in Na₂O, MgO, K₂O, MnO, TiO₂, CaO, and P₂O₅. The trace element ratios of Ni/Co and Cu/Zn of the shale suggest an oxic depositional environment. The average SiO₂ vs. Al₂O₃ ratio of the shales indicated textural maturity. Compared to the PAAS standard, the shales plot below the PAAS value of 0.85, suggesting a high degree of maturity and intensive chemical weathering, further confirmed on a CIA vs. PIA plot. On log (K₂O/Na₂O) against SiO₂ and tectonic setting discriminant function diagrams, the shales plot mostly in the field of passive continental margin tectonic setting. The discriminant function diagrams as well as Al₂O₃/TiO₂ ratio of the shales showed that they were derived from a mixed source (mafic and intermediate igneous rocks).