• Korean Journal of Ecology and Environment
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• v.42 no.4
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• pp.476-486
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• 2009

Major objective of our study was to introduce initial researches of national long-term ecological monitoring studies on Daechung Reservoir, as one of the representative lentic reservoir ecosystems in Korea. For the long-term ecological research (LTER), we conducted preliminary field monitoring during 2008~2009 and analyzed biological parameters such as phytoplankton, zooplankton, and freshwater fish along with chemical water quality and empirical model analysis. According to phytoplankton surveys, major taxa have varied largely depending on seasons and sites sampled. Overall phytoplankton data showed that cyanophyta dominated in the summer period and diatoms dominated in the winter. In zooplankton analysis, 25 species including 20 rotifers, 3 cladocerans and 2 copepods were collected during the survey. The relative abundance of rotifers (86.5%) was always greater than that of cladocerans (6.3%) or copepods (5.1%). There were distinct spatial and inter-annual changes in the abundance of zooplankton in the reservoir, displaying similar patterns in three sites with the exception of S3 during the study. According to fish surveys, 8 families and 39 species were observed during 2008~2009. The most dominant fish was an exotic species of Lepomis macrochirus (23%), indicating an severe influence of exotic species to the ecosystem. TP averaged $17.9\;{\mu}g\;L^{-1}$ ($6{\sim}80\;{\mu}g\;L^{-1}$), which was judged as a mesotrophy, and showed a distinct longitudinal gradients. TN averaged $1.585\;{\mu}g\;L^{-1}$ during the study and judged as hypereutrophic condition. Unlike TP, TN didn't show any large seasonal and spatial variations. Under the circumstances, nitrogen limitation may not happen in this system, indicating that nitrogen control is not effective in the watershed managements. These data generated in the LTER station will provide key information on long-term biological and water quality changes in relation to global warming and some clues for efficient reservoir ecosystem managements.

• Imaging Science in Dentistry
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• v.50 no.3
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• pp.199-208
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• 2020

Purpose: This study was performed to introduce an in vivo hybrid multimodality technique involving the coregistration of micro-computed tomography (micro-CT) and high-resolution magnetic resonance imaging (HR-MRI) to concomitantly visualize and quantify mineralization and vascularization at follow-up in a rat model. Materials and Methods: Three adult female rats were randomly assigned as test subjects, with 1 rat serving as a control subject. For 20 weeks, the test rats received a weekly intravenous injection of 30 ㎍/kg zoledronic acid, and the control rat was administered a similar dose of normal saline. Bilateral extraction of the lower first and second molars was performed after 10 weeks. All rats were scanned once every 4 weeks with both micro-CT and HR-MRI. Micro-CT and HR-MRI images were registered and fused in the same 3-dimensional region to quantify blood flow velocity and trabecular bone thickness at T0 (baseline), T4 (4 weeks), T8 (8 weeks), T12 (12 weeks), T16 (16 weeks), and T20 (20 weeks). Histological assessment was the gold standard with which the findings were compared. Results: The histomorphometric images at T20 aligned with the HR-MRI findings, with both test and control rats demonstrating reduced trabecular bone vasculature and blood vessel density. The micro-CT findings were also consistent with the histomorphometric changes, which revealed that the test rats had thicker trabecular bone and smaller marrow spaces than the control rat. Conclusion: The combination of micro-CT and HR-MRI may be considered a powerful non-invasive novel technique for the longitudinal quantification of localized mineralization and vascularization.

• Sleep Medicine and Psychophysiology
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• v.11 no.1
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• pp.44-49
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• 2004

Objectives: The purpose of this study was to investigate whether longitudinal changes in positive and negative symptoms affect cognitive functioning in chronic schizophrenia. Methods: Sixty-eight patients diagnosed with DSM-IV schizophrenia were examined on two occasions over 6 months for symptoms and cognitive changes. Symptoms were measured by PANSS. Cognitive functions were examined for sustained attention, executive function, concentration and attention, and verbal memory and learning using Degraded Stimulus Continuous Performance Test, Wisconsin Card Sorting Test, Digit Span, and Rey Auditory Verbal Learning Test, respectively. Twenty control subjects were assessed to compare the cognitive scores of remitted schizophrenic patients. Results: Patients showed significant improvement in symptoms and all cognitive tests after 6 months treatments. Significant improvements in positive and negative symptoms did not predict improvements in any aspect of cognitive functioning measured. Normal controls performed significantly better than remitted schizophrenic patients on all cognitive tests. The results show no relationship between change in symptoms and change in cognition in chronic schizophrenia. Conclusion: We suggest that symptomatic and cognitive impairment may be a distinct construct. These findings highlight the importance of treating cognitive impairment in addition to the clinical symptoms of schizophrenia.

• Journal of Korean Neurosurgical Society
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• v.60 no.5
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• pp.577-583
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• 2017

Objective : Laminoplasty is an effective surgical method for treating cervical degenerative disease. However, postoperative complications such as kyphosis, restriction of neck motion, and instability are often reported. Despite sufficient preoperative lordosis, this procedure often aggravates the lordotic curve of the cervical spine and straightens cervical alignment. Hence, it is important to examine preoperative risk factors associated with postoperative kyphotic alignment changes. Our study aimed to investigate preoperative radiologic parameters associated with kyphotic deformity post laminoplasty. Methods : We retrospectively reviewed the medical records of 49 patients who underwent open door laminoplasty for cervical spondylotic myelopathy (CSM) or ossification of the posterior longitudinal ligament (OPLL) at Pusan National University Yangsan Hospital between January 2011 and December 2015. Inclusion criteria were as follows : 1) preoperative diagnosis of OPLL or CSM, 2) no previous history of cervical spinal surgery, cervical trauma, tumor, or infection, 3) minimum of one-year follow-up post laminoplasty with proper radiologic examinations performed in outpatient clinics, and 4) cases showing C7 and T1 vertebral body in the preoperative cervical sagittal plane. The radiologic parameters examined included C2-C7 Cobb angles, T1 slope, C2-C7 sagittal vertical axis (SVA), range of motion (ROM) from C2-C7, segmental instability, and T2 signal change observed on magnetic resonance imaging (MRI). Clinical factors examined included preoperative modified Japanese Orthopedic Association scores, disease classification, duration of symptoms, and the range of operation levels. Results : Mean preoperative sagittal alignment was $13.01^{\circ}$ lordotic; $6.94^{\circ}$ lordotic postoperatively. Percentage of postoperative kyphosis was 80%. Patients were subdivided into two groups according to postoperative Cobb angle change; a control group (n=22) and kyphotic group (n=27). The kyphotic group consisted of patients with more than $5^{\circ}$ kyphotic angle change postoperatively. There were no differences in age, sex, C2-C7 Cobb angle, T1 slope, C2-C7 SVA, ROM from C2-C7, segmental instability, or T2 signal change. Multiple regression analysis revealed T1 slope had a strong relationship with postoperative cervical kyphosis. Likewise, correlation analysis revealed there was a statistical significance between T1 slope and postoperative Cobb angle change (p=0.035), and that there was a statistically significant relationship between T1 slope and C2-C7 SVA (p=0.001). Patients with higher preoperative T1 slope demonstrated loss of lordotic curvature postoperatively. Conclusion : Laminoplasty has a high probability of aggravating sagittal balance of the cervical spine. T1 slope is a good predictor of postoperative kyphotic changes of the cervical spine. Similarly, T1 slope is strongly correlated with C2-C7 SVA.

• The Mathematical Education
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• v.58 no.1
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• pp.101-120
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• 2019

The goal of this study was to apply an expectancy-value model(Wigfield & Eccles, 2000) to explain changes in six multi-ethnic students' achievement motivation in mathematics during sixth (2012) to eighth (2014) grades. In order to achieve this goal, we used narrative research methods. Although individual students' achievement motivation and mathematics related life experiences differed, there are some common factors influencing their motivation development, especially (a) roles played by parents and teachers; (b) assessment of peers' competencies; (c) past learning experiences related to mathematics curriculum; (d) perception of the relationship between mathematics competency and other subjects; (e) home backgrounds; and (f) perceived task values. In this study, we achieved some insight into why some multi-ethnic students are willing to study hard to get good scores while others are uninterested in mathematics, and why some multi-ethnic students are likely to pursue new mathematical tasks and persist despite challenges, while others easily give up studying mathematics in the face of adversity. We argue that in order to increase and sustain multi-ethnic students' achievement motivation, educators and parents should recognize that motivation is contextually formulated in the intersection of current people, time, and space, not a personal entity formed in an individual's mind. The findings of this study shed light on the development of achievement motivation and can inform efforts to develop multi-ethnic students' positive motivation, which might influence their mathematics achievement and success in school.

• 한국노년학
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• v.36 no.4
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• pp.1125-1139
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• 2016

The current study examines whether retirement changes health behaviors and how the effect differs by reasons for retirement. This study conducts fixed-effects logistic regression analyses, using data from the Korean Longitudinal Study of Aging (KLoSA) over the period 2006 through 2014. Results indicates that retirees are more likely to participate in regular exercise compared to their employed counterparts. Retirement is positively associated with participation in regular exercise regardless of reasons for retirement. The odds of being engaged in smoking among retirees are 50% less relative to those for employees. However, analyses by reasons for retirement reveal that only participants who retired for health problems or reaching retirement age are less likely to smoke cigarettes compared to employed participants. Retirees show significantly lower odds in drinking compared to employees. Yet, further analyses present that only individuals who retired due to health problems are less likely to drink alcohol. Overall, these results suggest that retirement may provide opportunities for positive changes in health behaviors. The present study imply that individuals who retired due to health problems benefits most from retirement in terms of health behaviors compared to retirees who retired for other reasons.

• (The) Korean Journal of Educational Psychology
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• v.32 no.1
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• pp.183-205
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• 2018

This study aims to demonstrate the longitudinal structural relationship between learner-centered instruction, learning motivation, growth beliefs, and academic stress. In particular, this study was carried out to focus on the structural effect of the related variables using data from the 3rd to 5th year of the Gyeonggi Education Panel Study. Results showed that while learner-centered instruction positively predicted both intrinsic and extrinsic motivation of learners, it predicted the former better. In addition, learner-centered instruction influenced academic stress through motivation, both intrinsic and extrinsic motivation were found to increase stress. Further, growth beliefs mediated motivation with learner-centered instruction; specifically, learner-centered instruction influenced learners' positive beliefs about growth, and learners who had growth beliefs had intrinsic motivation. At the same time, external motivation tended to be lower for learners who believed in the possibility of growth. Finally, the perceptions of learner-centered instruction affected academic stress through changes in growth beliefs. However, the other 3 factors (learner-centered instruction, learning motivation, and academic stress) were not statistically significant. In conclusion, learner-centered instruction was able to mitigate academic stress, demonstrating that this relationship is influenced by changes in growth beliefs rather than learning motivation, as previously studied. These results suggest that learners' perceptions and beliefs contribute to not only intrinsic motivation but also academic stress. Furthermore, it is suggested that learners need to change their learning environments in positive ways.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.16 no.6
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• pp.145-155
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• 2021

This study aims to examine the results of start-up policies of the previous government (2013-2017) and the current government (2017-2022). We would like to compare the perceptions of founders on the domestic start-up environment in 2016 and 2021. Based on the data (GETR) that surveyed the perception of the startup environment in 2016, a trend survey was conducted to compare the perception of the start-up environment of founders in 2021. As a result of the study, the founder's perception of the domestic start-up environment changed positively overall, but there was no significant change in the perception of 'tax adequacy', 'easy to recover investment', and 'easy to transfer technology'. In addition, the perception of the start-up environment of livelihood founders was negative compared to opportunity-type start-ups. As such, different results were found for each type of start-up. This study analyzed the difference in perception of the past and present start-up environment from the perspective of founders. In particular, I would like to propose a plan to improve the quality of the domestic start-up environment by seeking support measures for livelihood-type start-ups that have collapsed due to COVID-19.

• Korean Journal of Radiology
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• v.23 no.12
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• pp.1269-1280
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• 2022

Objective: This study aimed to evaluate the usefulness of quantitative indices obtained from deep learning analysis of gadoxetic acid-enhanced hepatobiliary phase (HBP) MRI and their longitudinal changes in predicting decompensation and death in patients with advanced chronic liver disease (ACLD). Materials and Methods: We included patients who underwent baseline and 1-year follow-up MRI from a prospective cohort that underwent gadoxetic acid-enhanced MRI for hepatocellular carcinoma surveillance between November 2011 and August 2012 at a tertiary medical center. Baseline liver condition was categorized as non-ACLD, compensated ACLD, and decompensated ACLD. The liver-to-spleen signal intensity ratio (LS-SIR) and liver-to-spleen volume ratio (LS-VR) were automatically measured on the HBP images using a deep learning algorithm, and their percentage changes at the 1-year follow-up (ΔLS-SIR and ΔLS-VR) were calculated. The associations of the MRI indices with hepatic decompensation and a composite endpoint of liver-related death or transplantation were evaluated using a competing risk analysis with multivariable Fine and Gray regression models, including baseline parameters alone and both baseline and follow-up parameters. Results: Our study included 280 patients (153 male; mean age ± standard deviation, 57 ± 7.95 years) with non-ACLD, compensated ACLD, and decompensated ACLD in 32, 186, and 62 patients, respectively. Patients were followed for 11-117 months (median, 104 months). In patients with compensated ACLD, baseline LS-SIR (sub-distribution hazard ratio [sHR], 0.81; p = 0.034) and LS-VR (sHR, 0.71; p = 0.01) were independently associated with hepatic decompensation. The ΔLS-VR (sHR, 0.54; p = 0.002) was predictive of hepatic decompensation after adjusting for baseline variables. ΔLS-VR was an independent predictor of liver-related death or transplantation in patients with compensated ACLD (sHR, 0.46; p = 0.026) and decompensated ACLD (sHR, 0.61; p = 0.023). Conclusion: MRI indices automatically derived from the deep learning analysis of gadoxetic acid-enhanced HBP MRI can be used as prognostic markers in patients with ACLD.

• Biomedical Science Letters
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• v.2 no.1
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• pp.91-108
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• 1996

The present study was designed to examine effect of short term treadmill and weight-training on aging arophy in the rat skeletal muscle. Male rats of 24 months old were used. Each groups included control, treadmill and weight-training for 4 weeks by using treadmill apparatus and body press apparatus. The histo and cytochemical, ultrastructural and stereological changes in senile skeletal muscles of the rat were observed in the present study. During the training period the body weight and muscular weight in all groups remained constant. The volume density of muscle fiber type IIC and IIB were increased, that of type IIA was decreased, but type I remained constant in treadmill-training group. In weight-training rat, the density of type IIA and IIB were increased, both those of type IIC was decreased. But, all changes of muscle fiber type is not significant. Senile control group some usual formation of mild contraction band, liposuscin pigment and muscular splitting were observed. After treadmill-training, histological and ultrastructural changes occurred in the muscle fiber, such as irregularity of the sarcolemma, interfibrillar vacuolization, longitudinal splitting, and widened I-bond. After weight-training, the changes occurred in the trained muscle fiber, such as appearances of many lysosomes and autophagic vacuoles, severe contraction band, and breakup of myofibrils. Histo and cytochemical studies showed that the activities of succinic dehydrogenase and acid phosphatase remained constant, activities of $Mg^{++}$-ATPase decrease with training. Stereological changes were not observed in the volume and numerical density of all subject component, but the surface density of mitochondrial inner membrane was increased with treadmill-training. These experimental results suggested that endurance training during short-term may result in the adaptible response in senile skeletal muscles. On the other side, weight-training is bad for senile skeletal muscle.