233 research outputs found
Analysis of the issues that emerged in the revision of the national social studies curriculum in South Korea: Text mining and semantic network analysis of the comments at the public hearing on YouTube
In South Korea, curriculum is revised, made public and implemented under a system known as a nation led curriculum. The South Korean national curriculum was completely revised 10 times between 1946 and 2015. At present, a complete revision is underway to replace the current 2015 national curriculum which is called the 2022 revised national curriculum. This study aims to analyze stakeholdersâ responses to the YouTube public hearing on social studies curriculum according to the 2022 revised national curriculum in South Korea in order to understand the context and causes of the issues that emerged. Text mining, semantic network analysis and word cloud techniques were employed to identify issues. As a result, three issues were identified in the social studies curriculum: the balanced development of general elective subjects in high school; the separation of social sciences and geography and division of textbooks in middle school social studies and the separate listing of four subjects, specifically geography, social sciences, history and morals. The issues revealed in this study provide beneficial implications for future social studies curriculum development, revision as well as the development of future research
Numerical Study of Compressible Magnetohydrodynamic Turbulence in Two Dimensions
We have studied forced turbulence of compressible magnetohydrodynamic (MHD)
flows through two-dimensional simulations with different numerical resolutions.
First, hydrodynamic turbulence with Mach number and density compression was generated by enforcing a random force. Then, initial,
uniform magnetic fields of various strengths were added with Alfv\'enic Mach
number . An
isothermal equation of state was employed, and no explicit dissipation was
included. After the MHD turbulence is saturated, the resulting flows are
categorized as very weak field (VWF), weak field (WF), and strong field (SF)
classes, which have ,
, and , respectively. Not only in the SF regime but
also in the WF regime, turbulent transport is suppressed by the magnetic field.
In the SF cases, the energy power spectra in the inertial range, although no
longer power-law, exhibit a range with slopes close to , hinting the
Iroshnikov-Kraichnan spectrum. Our simulations were able to produce the SF
class behaviors only with high resolution of at least grid cells. The
specific requirements for the simulation of the SF class should depend on the
code (and the numerical scheme) as well as the initial setup, but our results
do indicate that very high resolution would be required for converged results
in simulation studies of MHD turbulence.Comment: 20 pages, 6 figures. To appear in ApJ. Postscript file with full
resolution in ftp://canopus.chungnam.ac.kr/ryu/mhdturb2d.p
Relationship between Work Hours and Smoking Behaviors in Korean Male Wage Workers
OBJECTIVES: The purposes of this study are 1) to measure the prevalence of smoking according to weekly work hours by using data from the Korean Labor and Income Panel Study (KLIPS), and 2) to explain the cause of high smoking prevalence among those with short or long work hours by relative explanatory fraction. METHODS: Data from a total of 2,044 male subjects who responded to the questionnaire in the 10th year (2007) and 11th year (2008) of the Korean Labor and Income Panel Study were used for analysis. Current smoking, smoking cessation, continuous smoking, start of smoking, weekly work hours, occupational characteristics, sociodemographic and work-related factors, and health behavior-related variables were analyzed. Log-binomial regression analysis was used to study the relationship between weekly work hours and smoking behaviors in terms of the prevalence ratio. RESULTS: The 2008 age-adjusted smoking prevalence was 64.9% in the short work hours group, 54.7% in the reference work hours group, and 60.6% in the long work hours group. The smoking prevalence of the short work hours group was 1.39 times higher than that of the reference work hours group (95% confidence interval of 1.17-1.65), and this was explained by demographic variables and occupational characteristics. The smoking prevalence of the long work hours group was 1.11 times higher than that of the reference work hours group when the age was standardized (95% confidence interval of 1.03-1.19). This was explained by demographic variables. No independent effects of short or long work hours were found when the variables were adjusted. CONCLUSION: Any intervention program to decrease the smoking prevalence in the short work hours group must take into account employment type, job satisfaction, and work-related factors
Satellite-based In-situ Monitoring of Space Weather:
Many recent satellites have mission periods longer than 10 years; thus, satellite-based local space weather monitoring
is becoming more important than ever. This article describes the instruments and data applications of the Korea Space
wEather Monitor (KSEM), which is a space weather payload of the GeoKompsat-2A (GK-2A) geostationary satellite. The
KSEM payload consists of energetic particle detectors, magnetometers, and a satellite charging monitor. KSEM will provide
accurate measurements of the energetic particle flux and three-axis magnetic field, which are the most essential elements of
space weather events, and use sensors and external data such as GOES and DSCOVR to provide five essential space weather
products. The longitude of GK-2A is 128.2° E, while those of the GOES satellite series are 75° W and 135° W. Multi-satellite
measurements of a wide distribution of geostationary equatorial orbits by KSEM/GK-2A and other satellites will enable the
development, improvement, and verification of new space weather forecasting models. KSEM employs a service-oriented
magnetometer designed by ESA to reduce magnetic noise from the satellite in real time with a very short boom (1 m), which
demonstrates that a satellite-based magnetometer can be made simpler and more convenient without losing any performance
Multiple assessment methods of prenatal exposure to radio frequency radiation from telecommunication in the Mothers and Childrenâs Environmental Health (MOCEH) study
Objectives: To evaluate prenatal exposure to radiofrequency radiation (RFR) from telecommunication using a mobile phone questionnaire, operator data logs of mobile phone use and a personal exposure meter (PEM). Material and Methods: The study included 1228 motherâinfants pairs from the Mothers and Childrenâs Environmental Health (MOCEH) study â a multicenter prospective cohort study ongoing since 2006, in which participants were enrolled at †20 weeks of pregnancy, with a follow-up of a child birth and growth to assess the association between prenatal environmental exposure and childrenâs health. The questionnaire included the average calling frequency per day and the average calling time per day. An EME Spy 100 PEM was used to measure RFR among 269 pregnant women from November 2007 to August 2010. The operatorsâ log data were obtained from 21 participants. The Spearmanâs correlation test was performed to evaluate correlation coefficient and 95% confidence intervals between the mobile phone use information from the questionnaire, operatorsâ log data, and data recorded by the PEM. Results: The operatorsâ log data and information from the self-reported questionnaire showed significantly high correlations in the average calling frequency per day (Ï = 0.6, p = 0.004) and average calling time per day (Ï = 0.5, p = 0.02). The correlation between information on the mobile phone use in the self-reported questionnaire and exposure index recorded by the PEM was poor. But correlation between the information of the operatorsâ log data and exposure index for transmission of mobile communication was significantly high: correlation coefficient (p-value) was 0.44 (0.07) for calling frequency per day, and it was 0.49 (0.04) for calling time per day. Conclusions: The questionnaire information on the mobile phone use showed moderate to high quality. Using multiple methods for exposure assessment might be better than using only one method. Int J Occup Med Environ Health 2016;29(6):959â97
Telomere maintenance through recruitment of internal genomic regions
Cells surviving crisis are often tumorigenic and their telomeres are commonly maintained through the reactivation of telomerase. However, surviving cells occasionally activate a recombination-based mechanism called alternative lengthening of telomeres (ALT). Here we establish stably maintained survivors in telomerase-deleted Caenorhabditis elegans that escape from sterility by activating ALT. ALT survivors trans-duplicate an internal genomic region, which is already cis-duplicated to chromosome ends, across the telomeres of all chromosomes. These 'Template for ALT' (TALT) regions consist of a block of genomic DNA flanked by telomere-like sequences, and are different between two genetic background. We establish a model that an ancestral duplication of a donor TALT region to a proximal telomere region forms a genomic reservoir ready to be incorporated into telomeres on ALT activation.
Updates on the genetic variations of Norovirus in sporadic gastroenteritis in Chungnam Korea, 2009-2010
Previously, we explored the epidemic pattern and molecular characterization of noroviruses (NoVs) isolated in Chungnam, Korea in 2008, and the present study extended these observations to 2009 and 2010. In Korea, NoVs showed the seasonal prevalence from late fall to spring, and widely detected in preschool children and peoples over 60 years of age. Epidemiological pattern of NoV was similar in 2008 and in 2010, but pattern in 2009 was affected by pandemic influenza A/H1N1 2009 virus. NoV-positive samples were subjected to sequence determination of the capsid gene region, which resolved the isolated NoVs into five GI (2, 6, 7, 9 and 10) and eleven GII genotypes (1, 2, 3, 4, 6, 7, 8, 12, 13, 16 and 17). The most prevalent genotype was GII.4 and occupied 130 out of 211 NoV isolates (61.6%). Comparison of NoV GII.4 of prevalent genotype in these periods with reference strains of the same genotype was conducted to genetic analysis by a phylogenetic tree. The NoV GII.4 strains were segregated into seven distinct genetic groups, which are supported by high bootstrap values and previously reported clusters. All Korean NoV GII.4 strains belonged to either VI cluster or VII cluster. The divergence of nucleotide sequences within VI and VII intra-clusters was > 3.9% and > 3.5%, respectively. The "Chungnam(06-117)/2010" strain which was isolated in June 2010 was a variant that did not belong to cluster VI or VII and showed 5.8-8.2%, 6.2-8.1% nucleotide divergence with cluster VI and VII, respectively
Cytoprotective effects of fermented oyster extracts against oxidative stress-induced DNA damage and apoptosis through activation of the Nrf2/HO-1 signaling pathway in MC3T3-E1 osteoblasts
Osteoblast damage by oxidative stress has been recognized as a cause of bone-related disease, including osteoporosis. Recently, we reported that fermented Pacific oyster (Crassostrea gigas) extracts (FO) inhibited osteoclastogenesis and osteoporosis, while promoting osteogenesis. However, since the beneficial potential of FO on osteoblasts is not well known, in the present study, we investigated the cytoprotective effect of FO against oxidative stress in MC3T3-E1 osteoblasts. Our results demonstrated that FO inhibited hydrogen peroxide (H2O2)-induced DNA damage and cytotoxicity through the rescue of mitochondrial function by blocking abnormal ROS accumulation. FO also prevented apoptosis by suppressing loss of mitochondrial membrane potential and cytosolic release of cytochrome c, decreasing the rate of Bax/Bcl-2 expression and reducing the activity of caspase-9 and caspase-3 in H2O2-stimulated MC3T3-E1 osteoblasts, suggesting that FO protected MC3T3-E1 osteoblasts from the induction of caspase dependent- and mitochondria-mediated apoptosis by oxidative stress. In addition, FO markedly promoted the activation of nuclear factor-erythroid-2-related factor 2 (Nrf2), which was associated with the enhanced expression of heme oxygenase-1 (HO-1). However, inhibiting the expression of HO-1 by artificially blocking the expression of Nrf2 using siRNA significantly eliminated the protective effect of FO, indicating that FO activates the Nrf2/HO-1 signaling pathway in MC3T3-E1 osteoblasts to protect against oxidative stress. Based on the present data, FO is thought to be useful as a potential therapeutic agent for the inhibition of oxidative stress in osteoblasts
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