Publications by authors named "Jaeyoung Lee"

112 Publications

Impacts of COVID-19 on individuals' mobility behavior in Pakistan based on self-reported responses.

J Transp Health 2021 Sep 7;22:101228. Epub 2021 Aug 7.

School of Traffic and Transportation Engineering, Central South University, Changsha, Hunan, 410075, PR China.

The COVID-19 pandemic has been extremely disturbing mobility behavior due to travel restrictions and perceived COVID-19 threats. Recently, researchers from developed countries have shown interest in quantifying the impacts of the COVID-19 on individuals' mobility; however, similar research themes in lower income developing countries like Pakistan have not been sufficiently explored. Therefore, the objectives of the study are; 1) to explore the changes in self-reported individual's mobility behavior-trip frequencies by mode and by purpose in three COVID-19 severity periods; 2) to quantify the effects of respondents' personal (i.e., age, gender, education, and living place), and perceived details (i.e., safety perceptions, the COVID-19 threat perceptions) on the change in mobility behavior in the COVID-19 severity change; 3) to analyze the willingness to use public transportation in the post-pandemic period.

Methods: A web-based questionnaire survey was conducted from September 2020 to November 2020, resulting in 565 responses. Descriptive analysis, random parameter bivariate probit modeling, and structural equation modeling are adopted to achieve the objectives.

Results: The results reflect the change in individuals' mobility behavior in three severity periods of COVID-19, including before outbreak, during the most serious period, and after the most serious period. A substantial reduction in individuals' mobility was observed during the most serious period, which is recovering back to normal. The results also indicate the relationship of individuals' personal and perceived characteristics with the change in mobility in COVID-19 severity changes from before-to-serious and from the serious-to-after most serious period.

Conclusion: The COVID-19 pandemic has been affecting individuals' mobility behavior in Pakistan. The study's findings provide insightful information for the transportation agencies to better prepare for sustainable transportation management in the post-pandemic era.
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http://dx.doi.org/10.1016/j.jth.2021.101228DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8426114PMC
September 2021

Exploring transition durations of rear-end collisions based on vehicle trajectory data: A survival modeling approach.

Accid Anal Prev 2021 Sep 1;159:106271. Epub 2021 Jul 1.

Hunan Key Laboratory of Smart Roadway and Cooperative Vehicle-Infrastructure Systems, Changsha University of Science & Technology, Changsha, Hunan 410004, PR China. Electronic address:

The time-to-collision (TTC) index and its extended variants have been widely utilized to assess rear-end collision risks, but the characteristics of the time-series data have not been fully explored, especially for the transition from safe to risky conditions. This study proposes a novel approach in rear-end collision risk analysis based on the concept of transition durations. The vehicle trajectory data were extracted and the TTC index was used to identify risky and safe conditions. Three important transition durations are defined and their rationalities for evaluating rear-end collision risks are examined by developing random-parameters accelerated failure time (AFT) survival models. Furthermore, a typical case from real trajectory data is taken to discuss the limitations of using TTC and its variants, and the advantage of the proposed transition durations. The results of random-parameters AFT models reveal contributing factors affecting the length of three durations and demonstrate the rationality of transition durations in rear-end collision risks analysis. It is indicated that the proposed method outperforms TTC and its variants in evaluating rear-end collision risks, because it could not only provide the information of time point but also the variation of time-series data.
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http://dx.doi.org/10.1016/j.aap.2021.106271DOI Listing
September 2021

Improvement of Biophysical Properties and Affinity of a Human Anti-L1CAM Therapeutic Antibody through Antibody Engineering Based on Computational Methods.

Int J Mol Sci 2021 Jun 22;22(13). Epub 2021 Jun 22.

Department of Systems Immunology, Kangwon National University, Chuncheon 24341, Korea.

The biophysical properties of therapeutic antibodies influence their manufacturability, efficacy, and safety. To develop an anti-cancer antibody, we previously generated a human monoclonal antibody (Ab417) that specifically binds to L1 cell adhesion molecule with a high affinity, and we validated its anti-tumor activity and mechanism of action in human cholangiocarcinoma xenograft models. In the present study, we aimed to improve the biophysical properties of Ab417. We designed 20 variants of Ab417 with reduced aggregation propensity, less potential post-translational modification (PTM) motifs, and the lowest predicted immunogenicity using computational methods. Next, we constructed these variants to analyze their expression levels and antigen-binding activities. One variant (Ab612)-which contains six substitutions for reduced surface hydrophobicity, removal of PTM, and change to the germline residue-exhibited an increased expression level and antigen-binding activity compared to Ab417. In further studies, compared to Ab417, Ab612 showed improved biophysical properties, including reduced aggregation propensity, increased stability, higher purification yield, lower pI, higher affinity, and greater in vivo anti-tumor efficacy. Additionally, we generated a highly productive and stable research cell bank (RCB) and scaled up the production process to 50 L, yielding 6.6 g/L of Ab612. The RCB will be used for preclinical development of Ab612.
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http://dx.doi.org/10.3390/ijms22136696DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8268072PMC
June 2021

Safety improvements by intelligent connected vehicle technologies: A meta-analysis considering market penetration rates.

Accid Anal Prev 2021 Sep 10;159:106234. Epub 2021 Jun 10.

Key Laboratory of Road and Traffic Engineering of the Ministry of Education, Tongji University, China.

As the era of intelligent connected vehicles (ICVs) is approaching, a number of studies have investigated the potential benefits of ICVs, including the safety effects. Although previous studies agree that ICVs would significantly improve traffic safety, its quantified safety effects at different stages are still being debated. This study aims to estimate the ICVs' safety effects by market penetration rate (MPR) adopting a meta-analysis approach. The results from the meta-analysis indicate that the number of conflicts is exponentially reduced as the MPR goes up. For example, compared to the environment without ICVs, 4.2% and 17.4% of conflicts would decrease at the MPR of 10% and 50%, respectively. The effects are more obvious at higher MPR-43.4% of conflicts are expected to decrease at the MPR of 90%. From the case study in the United States based on the meta-analysis, it is expected that the MPR would reach 17-20% in the near future (2025) and 40-48% in 2035. The anticipated reduction in the number of fatal crashes would be 5% and 13%, in 2025 and 2035, respectively. The findings from this study will be useful for both public and private sectors to establish strategic plans to promote ICVs and identify their benefits at different MPRs.
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http://dx.doi.org/10.1016/j.aap.2021.106234DOI Listing
September 2021

Wnt/β-catenin Signaling Inhibitors suppress the Tumor-initiating properties of a CD44CD133 subpopulation of Caco-2 cells.

Int J Biol Sci 2021 12;17(7):1644-1659. Epub 2021 Apr 12.

Laboratory of Molecular and Cellular Biology, Department of Life Science, Sogang University, Seoul 04107, Korea.

Tumor-initiating cells or cancer stem cells are a subset of cancer cells that have tumorigenic potential in human cancer. Although several markers have been proposed to distinguish tumor-initiating cells from colorectal cancer cells, little is known about how this subpopulation contributes to tumorigenesis. Here, we characterized a tumor-initiating cell subpopulation from Caco-2 colorectal cancer cells. Based on the findings that Caco-2 cell subpopulations express different cell surface markers, we were able to discriminate three main fractions, CD44CD133, CD44CD133, and CD44CD133 subsets, and characterized their biochemical and tumorigenic properties. Our results show that CD44CD133 cells possessed an unusual capacity to proliferate and could form tumors when transplanted into NSG mice. Additionally, primary tumors grown from CD44CD133 Caco-2 cells contained mixed populations of CD44CD133 and non-CD44CD133 Caco-2 cells, indicating that the full phenotypic heterogeneity of the parental Caco-2 cells was re-created. Notably, only the CD44CD133 subset of Caco-2-derived primary tumors had tumorigenic potential in NSG mice, and the tumor growth of CD44CD133 cells was faster in secondary xenografts than in primary transplants. Gene expression analysis revealed that the Wnt/β-catenin pathway was over-activated in CD44CD133 cells, and the growth and tumorigenic potential of this subpopulation were significantly suppressed by small-molecule Wnt/β-catenin signaling inhibitors. Our findings suggest that the CD44CD133 subpopulation from Caco-2 cells was highly enriched in tumorigenic cells and will be useful for investigating the mechanisms leading to human colorectal cancer development.
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http://dx.doi.org/10.7150/ijbs.58612DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8120464PMC
April 2021

Carbon-Based Capacitive Deionization Electrodes: Development Techniques and its Influence on Electrode Properties.

Chem Rec 2021 Apr 1;21(4):820-840. Epub 2021 Mar 1.

Electrochemical Reaction and Technology Laboratory (ERTL), School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju, 61005, South Korea.

Capacitive deionization (CDI) is a potential technology to provide cost efficient desalinated and/or softened water. Several efforts have been invested in the fabrication of CDI electrodes that not only has outstanding performance but also high chance of large scalability. In this personal account, the different techniques in developing carbon-based materials are presented together with its actual effect on the surface and electrochemical properties of carbon. The categories presented are based on the studies done by the Electrochemical Reaction and Technology Laboratory, the Ertl Center, different research groups in South Korea, and selected papers from the past three years. Our perspective about research gaps and prospects are also included with the aim to increase interest for CDI research.
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http://dx.doi.org/10.1002/tcr.202000182DOI Listing
April 2021

The dynamic tradeoff between safety and efficiency in discretionary lane-changing behavior: A random parameters logit approach with heterogeneity in means and variances.

Accid Anal Prev 2021 Apr 16;153:106036. Epub 2021 Feb 16.

School of Traffic and Transportation Engineering, Central South University, Changsha, Hunan, 410075, PR China. Electronic address:

The discretionary lane-changing behavior is highly associated with crash occurrence. This paper investigates the dynamic tradeoff between safety and efficiency and influencing factors of the decision-making process for the discretionary lane-change. A random parameters logit approach with heterogeneity in means and variances is employed on a microscopic vehicle trajectory dataset. Four vehicles are analyzed as a discretionary lane-changing group, and both the distance-related and speed-related factors are taken into account to examine their dynamic effects. The modeling results indicate that (1) two distance-related variables produce significant random parameters with heterogeneity in means and variances, while there is only one speed-related variable having significant result for heterogeneity in means and variances; (2) the relationship between the speed of lane-changing vehicle and the heterogeneity in mean of vehicle clearance distance between leading vehicle in current lane and lane-changing vehicle quantitatively demonstrates that when the driver decides whether to change lanes, the driver considers the tradeoff between distance (i.e., safety) and speed (i.e., efficiency) at the same time; and (3) the number of significant variables is gradually decreased during the lane-changing decision-making process. It demonstrates that the lane-changing decision is a dynamic process where drivers gradually select more critical factors and pay more attention to them.
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http://dx.doi.org/10.1016/j.aap.2021.106036DOI Listing
April 2021

Improved Redox Reaction of Lithium Polysulfides on the Interfacial Boundary of Polar CoC O as a Polysulfide Catenator for a High-Capacity Lithium-Sulfur Battery.

ChemSusChem 2021 Feb 26;14(3):757. Epub 2021 Jan 26.

School of Earth Science and Environmental Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju, 61005, Republic of Korea.

Invited for this month's cover is the group of Jaeyoung Lee at the Gwangju Institute of Science and Technology. The cover shows how the cobalt oxalates faced on the conductive carbon can act as an electrocatalyst to facilitate the redox reaction of lithium polysulfide at the cathode interface in lithium-sulfur batteries. The facilitated electrochemical redox reaction of lithium polysulfides was proved by a series of catenation reactions formed on the interfacial boundary area. The electrochemical performance was enhanced in terms of the specific capacity and long-term cycle performance from the facilitated electrochemical activity. The Full Paper itself is available at 10.1002/cssc.202002140.
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http://dx.doi.org/10.1002/cssc.202100018DOI Listing
February 2021

Dual Ion Releasing Nanoparticles for Modulating Osteogenic Cellular Microenvironment of Human Mesenchymal Stem Cells.

Materials (Basel) 2021 Jan 15;14(2). Epub 2021 Jan 15.

School of Chemical Engineering, Sungkyunkwan University, Suwon 16419, Korea.

In this study we developed a dual therapeutic metal ion-releasing nanoparticle for advanced osteogenic differentiation of stem cells. In order to enhance the osteogenic differentiation of human mesenchymal stem cells (hMSCs) and induce angiogenesis, zinc (Zn) and iron (Fe) were synthesized together into a nanoparticle with a pH-sensitive degradation property. Zn and Fe were loaded within the nanoparticles to promote early osteogenic gene expression and to induce angiogenic paracrine factor secretion for hMSCs. In vitro studies revealed that treating an optimized concentration of our zinc-based iron oxide nanoparticles to hMSCs delivered Zn and Fe ion in a controlled release manner and supported osteogenic gene expression (RUNX2 and alkaline phosphatase) with improved vascular endothelial growth factor secretion. Simultaneous intracellular release of Zn and Fe ions through the endocytosis of the nanoparticles further modulated the mild reactive oxygen species generation level in hMSCs without cytotoxicity and thus improved the osteogenic capacity of the stem cells. Current results suggest that our dual ion releasing nanoparticles might provide a promising platform for future biomedical applications.
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http://dx.doi.org/10.3390/ma14020412DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7830414PMC
January 2021

Using vehicular trajectory data to explore risky factors and unobserved heterogeneity during lane-changing.

Accid Anal Prev 2021 Mar 21;151:105871. Epub 2020 Dec 21.

School of Traffic and Transportation Engineering, Central South University, Changsha, Hunan 410075, PR China. Electronic address:

This study aims to investigate contributing factors to potential collision risks during lane-changing processes from the perspective of vehicle groups and explore the unobserved heterogeneity of individual lane-changing maneuvers. Vehicular trajectory data, extracted from the Federal Highway Administration's Next Generation Simulation dataset, are utilized and 579 lane-changing vehicle groups are examined. Stopping distance indexes are developed to evaluate the potential collision risks of lane-changing vehicle groups. Three mixed binary logit models and three mixed logit models with heterogeneity in means and variances are established based on different perception reaction time. Model estimation results show that several variables significantly affect the risk status of lane-changing vehicle groups, including the mean values of clearance distance and speed differences between the leading vehicle in the current lane and the subject vehicle, standard deviations of clearance distance, and speed differences between these two vehicles, as well as standard deviations of the speed difference between the subject vehicle and the following vehicle in the target lane. Interestingly, the influences of the last three variables differ considerably across the observations and the mean of the random parameter for standard deviations of clearance distance between CLV and SV is associated with the mean speed difference between CLV and SV. Since one of the explanations is individual heterogeneity, personalized designs for advanced driver assistance system would be an effective measure to reduce the risk.
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http://dx.doi.org/10.1016/j.aap.2020.105871DOI Listing
March 2021

Immobilization of Radioiodine via an Interzeolite Transformation to Iodosodalite.

Nanomaterials (Basel) 2020 Oct 29;10(11). Epub 2020 Oct 29.

Innovation Center for Chemical Engineering, Department of Energy and Chemical Engineering, Incheon National University, Incheon 22012, Korea.

We described a technology for immobilizing radioiodine in the -cages by the interzeolite transformation of iodine-containing LTA (zeolite A) and FAU (zeolites X and Y) into a sodalite (SOD) structure. The immobilization of iodine in the -cage was confirmed using diverse characterization methods including powder XRD, elemental analysis, SEM-EDS, I MAS NMR, and I 3d XPS. Although both zeolites A (Na-A) and X (Na-X) were well converted into SOD structure in the presence of NaI and AgI, the iodide anions were fixed in the -cages only when NaI was used. The ability to adsorb methyl iodide (CHI) was evaluated for zeolites A and X in which Na and/or Ag ions were exchanged, and Ag and zeolite X showed better adsorption properties than Na and zeolite A, respectively. However, when both CHI adsorption ability and the successive immobilization of iodine by interzeolite transformation were considered, Na-X was determined to be the best candidate of adsorbent among the studied zeolites. More than 98% of the iodine was successfully immobilized in the -cage in the SOD structure by the interconversion of Na-X following CHI adsorption, although the Na-X zeolite exhibited half the CHI adsorption capacity of Ag-X.
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http://dx.doi.org/10.3390/nano10112157DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7693607PMC
October 2020

Spatial heterogeneity analysis of macro-level crashes using geographically weighted Poisson quantile regression.

Accid Anal Prev 2020 Dec 22;148:105833. Epub 2020 Oct 22.

Smart Transportation Key Laboratory of Hunan Province, School of Traffic and Transportation Engineering, Central South University, Changsha, 410075, China.

In recent years, globally quantile-based model (e.g. quantile regression) and spatially conditional mean models (e.g. geographically weighted regression) have been widely and commonly employed in macro-level safety analysis. The former ones assume that the model coefficients are fixed over space, while the latter ones only represent the entire distribution of variable effects by a single concentrated trend. However, the influence of crash related factors on the distribution of crash frequency is observed to vary over space and across different quantiles. Therefore, a geographically weighted Poisson quantile regression (GWPQR) model is employed to investigate the spatial heterogeneity of variable effects crossing different quantiles. Five categories, including exposure, socio-economic, transportation, network and land use were selected to estimate the spatial effects on crash frequency. In the case study, vehicle related crashes collected in New York City were used to validate the predicted performance of the proposed models. The results show that the GWPQR outperforms the NB, QR and GWNBR for modeling the skewed distribution, reconstructing the crash distribution and capturing the unobserved spatial heterogeneity. Additionally, the significant coefficients are further used to classify all 21 variables into key, important and general parts. Then we discuss how these factors affects the regional crashes over space and distribution of crash frequency. This study confirms that the influencing factors have varying effects on different quantiles of distribution and on different regions, which could be helpful to provide support for making safety countermeasures and policies at urban regional level.
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http://dx.doi.org/10.1016/j.aap.2020.105833DOI Listing
December 2020

Improved Redox Reaction of Lithium Polysulfides on the Interfacial Boundary of Polar CoC O as a Polysulfide Catenator for a High-Capacity Lithium-Sulfur Battery.

ChemSusChem 2021 Feb 2;14(3):876-883. Epub 2020 Nov 2.

School of Earth Science and Environmental Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju, 61005, Republic of Korea.

The performance of cobalt oxalate as an electrocatalyst in a lithium-sulfur battery (LSB) is improved owing to the suitable adsorbent properties of sulfur. The adsorption mechanism is elucidated by UV/Vis spectroscopy and surface analysis through X-ray photoelectron spectroscopy. Li S is converted into thiosulfate and polythionate by a catenation reaction on the interfacial boundary of CoC O contacted with carbon. Following this, the active polythionate and short-chained liquid lithium polysulfides (LiPS) bound to the cobalt surface are further reduced as CoC O reduces the overpotential to facilitate the LiPS redox reaction, leading to high specific capacity, lower self-discharge rate, and stable long-term cycling performance.
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http://dx.doi.org/10.1002/cssc.202002140DOI Listing
February 2021

Peer mentoring experiences of nursing students based on the caring perspective: A qualitative study.

Nurse Educ Today 2020 Nov 29;94:104586. Epub 2020 Aug 29.

Department of Nursing, Semyung University, Jecheon, Republic of Korea.

Background: Care competency is a critical aspect required of nursing students who want to become nurses. Peer mentoring is a useful way to experience the natural care process.

Objectives: This study aimed to explore from the caring perspective the experiences of nursing students who have participated in peer mentoring as mentors and mentees.

Design: This was a qualitative study; individual interviews were conducted and content analysis was performed to explore and describe peer mentoring experiences.

Settings: This study was conducted in the department of nursing at a university in the Republic of Korea.

Participants: The participants were nine students in their second to fourth year who participated as mentors and mentees in the peer mentoring program organized by the department of nursing.

Methods: Data on participants' experiences of mentoring were collected through individual interviews. The transcribed content was analyzed using content analysis, and the categorized content was reorganized through the framework of the theory of caring.

Results: The results of the content analysis revealed five categories that formed a sequential process of caring, which became the cycle of another process of care.

Conclusions: This study's findings regarding peer mentoring experiences of nursing college students indicate that the program can be effective in improving care competencies related to nursing. Peer mentoring in nursing education could be a useful method to develop students' professional competencies.
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http://dx.doi.org/10.1016/j.nedt.2020.104586DOI Listing
November 2020

Review on big data applications in safety research of intelligent transportation systems and connected/automated vehicles.

Accid Anal Prev 2020 Oct 4;146:105711. Epub 2020 Sep 4.

School of Traffic & Transportation Engineering, Central South University, Changsha, Hunan, People's Republic of China.

The era of Big Data has arrived. Recently, under the environment of intelligent transportation systems (ITS) and connected/automated vehicles (CAV), Big Data has been applied in various fields in transportation including traffic safety. In this study, we review recent research studies that employed Big Data to analyze traffic safety under the environment of ITS and CAV. The particular topics include crash detection or prediction, discovery of contributing factors to crashes, driving behavior analysis, crash hotspot identification, etc. From the reviewed studies, employing advanced analytics for Big Data has a great potential for understanding and enhancing traffic safety. Big Data application in traffic safety integrates and processes massive multi-source data, breaks through the limitations of the traditional data analytics, and discovers and solves the problems, which cannot be solved by the traditional safety analytics. Lastly, suggestions are provided for future Big Data safety analytics under the environment of ITS and CAV.
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http://dx.doi.org/10.1016/j.aap.2020.105711DOI Listing
October 2020

Incidence of intussusception before and after the introduction of rotavirus vaccine in Korea.

PLoS One 2020 28;15(8):e0238185. Epub 2020 Aug 28.

Division of Vaccine-Preventable Disease Control and National Immunization Program, Korea Centers for Disease Control and Prevention, Cheongju, Republic of Korea.

Background: Recent studies have reported that after the introduction of rotavirus vaccine the incidence of intussusception did not change among infants, or slightly increased at the age immediately after the first dose. The rotavirus vaccines were introduced in Korea for private market use in 2007-2008. We investigated the incidence of intussusception before (2002-2006) and after (2009-2015) the vaccine introduction in Korea.

Methods: We conducted an interrupted time series study that used data from the Korean National Health Insurance database to identify infants (<12 months of age) who were diagnosed with intussusception and underwent non-invasive or invasive reduction from 2002 to 2015. According to the recommended ages for immunization, the annual intussusception incidence and the incidence rate ratios were calculated among three age groups, 6-14, 15-24, and 25-34 weeks.

Results: The annual incidences in infants have decreased over time from 241.7 per 100,000 infants (pre-vaccine period) to 160.1-205.2 per 100,000 infants (post-vaccine period). The incidence rate ratio during the post-vaccine period ranged from 0.66 to 0.85. The incidences of intussusception in all three infant age groups have decreased in post-vaccine period compared to pre-vaccine period (incidence rate ratio range: 0.31-0.65, 0.47-0.75, and 0.68-0.94 in 6-14, 15-24, and 25-34 weeks, respectively).

Conclusions: The incidence of intussusception in infants did not increase after the rotavirus vaccine introduction in Korea, but rather decreased over the past decades. Since the incidence of intussusception varies according to country or region, continuous monitoring the incidence of intussusception in infants is necessary in each county or region.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0238185PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7454960PMC
October 2020

Analysis of the transition condition of rear-end collisions using time-to-collision index and vehicle trajectory data.

Accid Anal Prev 2020 Sep 9;144:105676. Epub 2020 Jul 9.

School of Traffic and Transportation Engineering, Central South University, Changsha, Hunan, 410075, PR China. Electronic address:

Time-to-collision (TTC) index has been extensively utilized to evaluate rear-end collision risks, but few studies have focused on the special transition process that vehicles change from a safe to a dangerous situation. This study conducts an in-depth analysis of the transition condition of rear-end collisions. Realistic vehicle trajectory data were extracted from the Federal Highway Administration's Next Generation Simulation (NGSIM) datasets. The TTC index was utilized to pinpoint dangerous and transition conditions. A total of 13 types of transition conditions were categorized and a novel indicator, the derivative of TTC (TTCD), is proposed to evaluate changing rate of TTCs. Three types of TTCDs, corresponding to different time point or interval, were further analyzed based on developed regression models. The results indicate that: (1) although theoretically there are a total of 13 types of transition conditions, three types are dominant in practice; (2) the TTCD(t) values at transition start points are significantly smaller than the TTCD(t) at end points and the average TTCD(t,t), which indicates the quickest change of TTC values, while the TTCD(t) has the slowest changes of TTC values; and (3) the following vehicle's speed and acceleration rate, and speed difference and acceleration difference between two vehicles have significant effects on TTCDs. The influences are more remarkable of TTCD(t) than those of TTCD(t), and the TTCD(t,t) always shows the average characteristic. Lastly, corresponding countermeasures are discussed based on findings above.
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http://dx.doi.org/10.1016/j.aap.2020.105676DOI Listing
September 2020

Enhanced osteogenic differentiation of human mesenchymal stem cells by direct delivery of Cbfβ protein.

Biotechnol Bioeng 2020 09 20;117(9):2897-2910. Epub 2020 Jun 20.

Department of Medical Biomaterials Engineering, Kangwon National University, Chuncheon-si, Gangwon-do, Republic of Korea.

Core binding factor β (Cbfβ) is a non-DNA binding cofactor of Runx2 that potentiates DNA binding. Previously, it has been reported that Cbfβ plays an essential role in osteogenic differentiation and skeletal development by inhibition adipogenesis. Here, we delivered the recombinant Cbfβ protein into human mesenchymal stem cells (MSCs) and triggered osteogenic lineage commitment. The efficient delivery of Cbfβ was achieved by fusing 30Kc19 protein, which is a cell-penetrating protein derived from the silkworm. After the production of the recombinant Cbfβ-30Kc19 protein in the Escherichia coli expression system, and confirmation of its intracellular delivery, MSCs were treated with the Cbfβ-30Kc19 once or twice up to 300 µg/ml. By investigating the upregulation of osteoblast-specific genes and phenotypical changes, such as calcium mineralization, we demonstrated that Cbfβ-30Kc19 efficiently induced osteogenic differentiation in MSCs. At the same time, Cbfβ-30Kc19 suppressed adipocyte formation and downregulated the expression of adipocyte-specific genes. Our results demonstrate that the intracellularly delivered Cbfβ-30Kc19 enhances osteogenesis in MSCs, whereas it suppresses adipogenesis by altering the transcriptional regulatory network involved in osteoblast-adipocyte lineage commitment. Cbfβ-30Kc19 holds great potential for the treatment of bone-related diseases, such as osteoporosis, by allowing transcriptional regulation in MSCs, and overcoming the limitations of current therapies.
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http://dx.doi.org/10.1002/bit.27453DOI Listing
September 2020

Investigating the Impacts of Real-Time Weather Conditions on Freeway Crash Severity: A Bayesian Spatial Analysis.

Int J Environ Res Public Health 2020 04 17;17(8). Epub 2020 Apr 17.

Key Laboratory of Road & Traffic Engineering of the Ministry of Education, Tongji University, Shanghai 201804, China.

This study presents an empirical investigation of the impacts of real-time weather conditions on the freeway crash severity. A Bayesian spatial generalized ordered logit model was developed for modeling the crash severity using the hourly wind speed, air temperature, precipitation, visibility, and humidity, as well as other observed factors. A total of 1424 crash records from Kaiyang Freeway, China in 2014 and 2015 were collected for the investigation. The proposed model can simultaneously accommodate the ordered nature in severity levels and spatial correlation across adjacent crashes. Its strength is demonstrated by the existence of significant spatial correlation and its better model fit and more reasonable estimation results than the counterparts of a generalized ordered logit model. The estimation results show that an increase in the precipitation is associated with decreases in the probabilities of light and severe crashes, and an increase in the probability of medium crashes. Additionally, driver type, vehicle type, vehicle registered province, crash time, crash type, response time of emergency medical service, and horizontal curvature and vertical grade of the crash location, were also found to have significant effects on the crash severity. To alleviate the severity levels of crashes on rainy days, some engineering countermeasures are suggested, in addition to the implemented strategies.
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http://dx.doi.org/10.3390/ijerph17082768DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7215785PMC
April 2020

Systemic approach to improve safety of urban unsignalized intersections: Development and validation of a Safety Index.

Accid Anal Prev 2020 Apr 3;141:105523. Epub 2020 Apr 3.

University of Central Florida, Department of Civil, Environmental and Construction Engineering, 4000 University Blvd, Orlando, FL, United States. Electronic address:

Methods based on crash data analysis are effective in identifying intersections with a potential for safety improvement. However, it is well recognized that crash data suffer from several shortcomings and that there are clues to safety other than crash occurrence. The systemic approach is an alternative method to address safety issues. In this approach, a transportation agency is able to identify priority locations based on the presence of risk factors rather than actual crashes. To promote wider use of the systemic safety approach, this paper aims at developing and validating a procedure to rank unsignalised urban intersections for safety improvement based on the evaluation of risk factors by road safety inspections. The procedure assesses a Safety Index (SI) that measures the safety performance of unsignalised urban intersections. The SI is formulated by combining two components of risk: the exposure of road users to road hazards (Exposure) and the risk factors, which increase the probability of involvement in crashes (Risk Index). The SI is made of two elements, one related to vehicles and one to pedestrians. Twenty-three detailed safety issues and ten general safety issues are assessed to compute the vehicle Risk Index and the pedestrian Risk Index. Safety issues were selected considering that they are common issues and that effective remedial measures exist and have already proven their effectiveness. Finally, criteria for identifying and ranking safety issues were defined. The SI has two main practical applications. High risk intersections, where safety measures that can reduce crash frequency exist, can be identified and ranked by the SI. Specific safety issues, that give more contribution to unsafety, are pointed out in order to give indication about more appropriate safety measures according to the systemic safety approach. The procedure was validated with a sample of eighty-nine urban intersections located in Orange County (Florida, U.S.). For these intersections, the SI scores, the Empirical Bayes (EB) safety estimates, and the potential for improvement (PFI) were compared. The correlation between the SI scores and the EB estimates was highly significant both for vehicles (R = 0.66) and pedestrians (R = 0.58) as well as for the total crashes (R = 0.68). The results from the Spearman's rank-correlation analysis provided further validation for the SI indicating that ranking from the SI and the EB estimates agree at the 99.9% confidence level for vehicles (ρ = 0.78), pedestrians (ρ = 0.93), and total (ρ = 0.93).
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http://dx.doi.org/10.1016/j.aap.2020.105523DOI Listing
April 2020

The Role of Lone-Pair Electrons in Pt-N Interactions for the Oxygen Reduction Reaction in Polymer Exchange Membrane Fuel Cells.

ChemSusChem 2020 Apr;13(7):1660

School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology (GIST), 123 Cheomdangwagi-Ro, Gwangju, 61005, South Korea.

Invited for this month's cover is the group of Jaeyoung Lee at the Gwangju Institute of Science and Technology (GIST). The cover image shows how the lone-pair electrons on N atoms could play a role in both uniform nucleation of Pt nanoparticles and facile oxygen reduction reaction (ORR). Strong Pt-N interaction based on π-backdonation improves not only the activity of the ORR but also the durability in the polymer exchange membrane fuel cells. The Full Paper itself is available at 10.1002/cssc.201903403.
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http://dx.doi.org/10.1002/cssc.202000527DOI Listing
April 2020

Transferability of safety performance functions and hotspot identification for freeways of the United States and China.

Accid Anal Prev 2020 May 13;139:105493. Epub 2020 Mar 13.

School of Traffic and Transportation Engineering, Central South University, Changsha, 410075, China.

Safety performance function (SPF) has been a vital tool in traffic safety evaluation including finding contributing factors to crashes, identifying hotspots, and assessing safety effects of countermeasures. In the United States (U.S.), the Highway Safety Manual provides a number of SPFs for a variety of road facilities. Due to the limited availability of traffic data in many regions, the transferability of SPFs has been an important topic in traffic safety analysis and has been evaluated by several studies. Nevertheless, the international transferability of freeway SPFs and the applicability of transferred SPFs on hotspot identification has been rarely investigated. Based on data from two Chinese cities, Shanghai and Suzhou, and three U.S. states, Texas, New York and Florida, this study analyzes the transferability of freeway SPFs between Chinese and U.S. regions. These SPFs are then transferred to the other country and their performance on hotspot identification is investigated. SPFs were developed in the frameworks of Poisson, Poisson-lognormal and negative binomial regressions for the five localities separately, and were calibrated using the calibration functions before being transferred. Without calibration, the poor model transferability was found between the two countries, while after calibration, the transferred SPFs between Shanghai/Suzhou and Texas/New York showed satisfactory performance on both model fitting and hotspot identification. However, the transferability of SPFs between Florida and the Chinese cities turned out to be unsatisfactory regardless of whether being calibrated or not, which was attributable to the considerable difference in traffic flow. The findings of this study are expected to be a good reference for researchers and practitioners who want to understand the transferability and applicability of SPFs in the international context.
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http://dx.doi.org/10.1016/j.aap.2020.105493DOI Listing
May 2020

Proactive crash risk prediction modeling for merging assistance system at interchange merging areas.

Traffic Inj Prev 2020 10;21(3):234-240. Epub 2020 Mar 10.

Jiangsu Key Laboratory of Urban ITS, Jiangsu Collaborative Innovation Center of Modern Urban Traffic Technologies, School of Transportation, Southeast University, Nanjing, China.

Ramp drivers have to merge into the through traffic in a limited time and space at interchange merging areas. Different merging decisions are made due to drivers' various perception abilities of potential danger, which might significantly increase the crash risk. Driving assistance technology (DA) is expected to be an effective way of mitigating the crash risk. Hence, this paper aims to contribute to the literature by designing a model strategy to predict the crash risk of merging drivers in order to enhance the merging assistance system for crash avoidance. Unmanned aerial vehicle (UAV) was used to collect individual vehicle data to conduct traffic analysis at the microscopic level. A model strategy was proposed to predict the crash risk of merging vehicles which could make sure that ramp drivers are aware of potential risks in advance. Three models (i.e., binary logistic regression, multinomial logistic regression, and nested logit models) were developed and compared. Target-lane-related and merging-vehicle-related variables were found significant with crash risk, including the speed of the merging vehicle, the speed of lead/lag vehicle in the target lane, the type of lead/lag vehicle in the target lane. Different variables were found to be significant in the proposed models. The results suggest that the nested logit model has the highest prediction accuracy. It is concluded that the merging speed, driving ability (i.e., lane-keeping instability), and the vehicle type in the target lane affect the crash risk. Finally, the implementation of the proposed prediction model for merging assistance system is designed. The findings from this study can have implications for the design of the merging assistance system for helping drivers make safe merging decisions and thus enhancing the safety of the interchange merging area.
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http://dx.doi.org/10.1080/15389588.2020.1734581DOI Listing
October 2020

The Role of Lone-Pair Electrons in Pt-N Interactions for the Oxygen Reduction Reaction in Polymer Exchange Membrane Fuel Cells.

ChemSusChem 2020 Apr 19;13(7):1751-1758. Epub 2020 Feb 19.

School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology (GIST), 123 Cheomdangwagi-Ro, Gwangju, 61005, South Korea.

An N-doped carbon with various N concentrations was prepared by using a scalable ball-milling method. The importance of the lone pair of electrons on the N species for the stability of Pt nanoparticles and their activity toward the oxygen reduction reaction was investigated. X-ray spectroscopic analysis was used to investigate the interaction between Pt and the pyridinic N. The pyridinic N modified the Pt oxidation state and helped achieve size homogeneity and high catalytic activity by facilitating the rate-determining step.
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http://dx.doi.org/10.1002/cssc.201903403DOI Listing
April 2020

The Impact of Sexual Initiation Timing and Sexual Experience on Depressive Symptoms in South Korean Adolescents: Gender Differences in a Nationwide Cross-Sectional Study.

Authors:
Jaeyoung Lee

J Pediatr Nurs 2020 May - Jun;52:e15-e20. Epub 2019 Nov 28.

Department of Nursing Science, College of Science, Kyungsung University, Busan, Republic of Korea. Electronic address:

Purpose: This study utilized data from the Korea Youth Risk Behavior Survey to examine gender differences in the impact of sexual initiation, and age at sexual initiation, on depressive symptoms among Korean adolescents.

Design And Methods: This study performed a secondary analysis of cross-sectional data from the 14th Korea Youth Risk Behavior Survey (2018). Data from 60,040 adolescents aged 12-18 were included in this study. The relationship between sexual experience, age at initiation, and depressive symptoms was analyzed with complex sample multiple logistic regression.

Results: Overall, 5.7% of participants declared having had sexual experience. Sexual initiation tended to occur from grade 7 and above. In addition, 33.6% of girls and 21.1% of boys reported having depressive symptoms. Depressive symptoms were associated with sexual initiation experience, but depression symptoms were not associated with the timing of sexual initiation.

Conclusions: This study provides preliminary evidence of a relationship between sexual experience and depressive symptoms among adolescents; however, this relationship appeared independent of the timing of sexual initiation. These findings suggest that sexually active adolescents should be screened for depressive symptoms, regardless of gender.

Practice Implications: This is the first study to examine the impact of sexual initiation and its timing on depressive symptoms among Korean adolescents. Sexual behaviors of Korean adolescents should be accounted for during the development of mental health policies aimed at young people. In addition, sexually active adolescents should be screened and monitored for depressive symptoms.
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http://dx.doi.org/10.1016/j.pedn.2019.11.009DOI Listing
April 2021

Looking Back and Looking Ahead in Electrochemical Reduction of CO.

Chem Rec 2020 Feb 6;20(2):89-101. Epub 2019 Sep 6.

Ertl Center for Electrochemistry and Catalysis, GIST, Gwangju, 61005, South Korea.

Electrochemical reduction of carbon dioxide (CO ) to valuable organic compounds is promising as to recycling of carbon source of CO and technical compatibility with systems using renewable energy resources. In recent years, considerable efforts have been devoted to the research field of CO conversion using electrocatalysis. This personal account particularly focuses on the recent progress that has been achieved by the Ertl Center and a number of groups in South Korea that becomes one of the larger CO emitters. The research trends of catalyst development divided into different categories according to the primary products are presented first. Afterwards, several studies on theoretical calculations and electrolytic reactors are reviewed taking into account the fundamental understanding and feasibility of the CO electroreduction. Finally, a perspective on the challenges and needs in achieving the advanced level of research and development is presented.
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http://dx.doi.org/10.1002/tcr.201900048DOI Listing
February 2020

A new etching process for zinc oxide with etching rate and crystal plane control: experiment, calculation, and membrane application.

Nanoscale 2019 Jul 19;11(25):12337-12346. Epub 2019 Jun 19.

Department of Chemical Engineering, College of Engineering, Kyung Hee University, Yongin 17140, Korea.

The etching process can be a useful method for the morphology control of nanostructures. Using precise experiments and theoretical calculations, we report a new ZnO etching process triggered by the reaction of ZnO with transition metal cations and demonstrate that the etching rate and direction could be controlled by varying the kind of transition metal cation. In addition, the developed etching process was introduced to form a thin and uniform ZnO layer, which was utilized for the fabrication of an improved propylene-selective ZIF-8 membrane via conversion seeding and secondary growth.
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http://dx.doi.org/10.1039/c9nr02248aDOI Listing
July 2019

Experimental and Density Functional Theory Corroborated Optimization of Durable Metal Embedded Carbon Nanofiber for Oxygen Electrocatalysis.

J Phys Chem Lett 2019 Jun 24;10(11):3109-3114. Epub 2019 May 24.

Department of Chemistry , Korea Advanced Institute of Science and Technology (KAIST) , 291 Daehak-Ro , Daejeon 34141 , Republic of Korea.

There is a growing need for widespread deployment of hydrogen and fuel cell technology for the realization of a sustainable energy landscape. However, due to the high price of platinum (Pt) catalysts, it is necessary to develop highly active and stable non-Pt oxygen reduction reaction (ORR) catalysts. Here, we describe a rational design of nonnoble metal-embedding and nitrogen-containing carbon nanofiber (M-CNF) catalysts. Using a combined experimental and computational approach, we establish an ORR activity volcano of M-CNF using the work function of the embedded metal as the descriptor. Near the top of the activity volcano, the embedded metal is further optimized by tuning the FeCo alloy composition to simultaneously achieve high catalytic activity and durability. This work identifies the mechanistic importance of controlling the charge transfer between the metal and carbon layers, providing guidance for the design of non-Pt ORR catalysts using stable carbon-layer-protected metals.
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http://dx.doi.org/10.1021/acs.jpclett.9b00927DOI Listing
June 2019

Enhancement of nanofluid stability and critical heat flux in pool boiling with nanocellulose.

Carbohydr Polym 2019 Jun 7;213:393-402. Epub 2019 Mar 7.

Handong Global University, 558, Handong-ro, Heunghae-eup, Buk-gu, Pohang, Gyeongbuk, 37554, Republic of Korea. Electronic address:

A nanofluid, which is an aqueous fluid with nanoparticles, is an attractive medium for enhancing critical heat flux (CHF); however, its instability over a long period of time due to sedimentation and aggregation has impeded its successful application in industry. In this study, lightweight negatively charged TEMPO-oxidized cellulose nanofibers (CNFs) were utilized as a nano-sized substance in water and examined to enhance both the CHF performance and thermal stability of nanofluids. Owing to low density of the CNFs and long range repulsion between negatively charged CNFs, there were no aggregation and sedimentation of CNFs with multiple boiling/cooling cycles. In addition, with CNF concentrations of 0.01, 0.03, 0.05, and 0.10 wt%, CHF enhancement increases of 40.7%, 45.1%, 54.9%, and 69.4%, respectively, were achieved over that of pure water. The present results demonstrated the great potential of CNFs as eco-friendly and cost-effective nano-substances that can overcome the instability of nanofluids.
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http://dx.doi.org/10.1016/j.carbpol.2019.03.023DOI Listing
June 2019

Effect of a Social Support Program for Mothers of Children with Precocious Puberty: A Preliminary Quasi-Experimental Study.

J Pediatr Nurs 2019 May - Jun;46:e2-e9. Epub 2019 Feb 12.

Department of Nursing, Dong-A University, Busan, Republic of Korea. Electronic address:

Purpose: The purpose of this study was to evaluate the effects of a social support program on the stress, anxiety, guilt, and life satisfaction levels among Korean mothers of children with precocious puberty.

Design And Methods: A non-equivalent control group and a non-synchronized design were used in this quasi-experiment study. Thirty-four mothers (divided into equal-sized experimental and control groups), 32-47 years of age, with children aged 6-11 years old, were recruited from a pediatric outpatient department at a national university hospital. The experimental group was involved in four sessions of a 4-week social support program. Descriptive statistics were used for demographic characteristics. Chi-square tests and t-tests were used to evaluate group differences.

Results: The program significantly reduced mothers' stress and guilt and significantly increased their life satisfaction. No significant differences in changes in anxiety were reported between the groups.

Conclusions: This study confirms that the social support program was a useful nursing intervention for Korean mothers of children with precocious puberty, which can be extensively applied to help mothers in similar situations.

Practice Implications: The preliminary study findings may inform healthcare professionals to develop effective interventions to promote psychosocial well-being of mothers of children with precocious puberty through strengthening their social support and to further improve the quality of life of children with precocious puberty and their families.
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http://dx.doi.org/10.1016/j.pedn.2019.01.012DOI Listing
December 2019
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