72 research outputs found
An auxin-mediated ultradian rhythm positively influences root regeneration via EAR1/EUR1 in Arabidopsis
No full textUltradian rhythms have been proved to be critical for diverse biological processes. However, comprehensive understanding of the short-period rhythms remains limited. Here, we discover that leaf excision triggers a gene expression rhythm with ~3-h periodicity, named as the excision ultradian rhythm (UR), which is regulated by the plant hormone auxin. Promoter–luciferase analyses showed that the spatiotemporal patterns of the excision UR were positively associated with de novo root regeneration (DNRR), a post-embryonic developmental process. Transcriptomic analysis indicated more than 4,000 genes including DNRR-associated genes were reprogramed toward ultradian oscillation. Genetic studies showed that EXCISION ULTRADIAN RHYTHM 1 (EUR1) encoding ENHANCER OF ABSCISIC ACID CO-RECEPTOR1 (EAR1), an abscisic acid signaling regulator, was required to generate the excision ultradian rhythm and enhance root regeneration. The eur1 mutant exhibited the absence of auxin-induced excision UR generation and partial failure during rescuing root regeneration. Our results demonstrate a link between the excision UR and adventitious root formation via EAR1/EUR1, implying an additional regulatory layer in plant regeneration. Copyright © 2023 Vu, Song, Park, Xu, Nam and Hong.11Nsciescopu
Influential Factors on Level of Injury in Pedestrian Crashes: Applications of Ordered Probit Model with Robust Standard Errors
No full textPedestrian-involved crashes that occurred in the city of San Francisco over a six-year period, 2002–2007, were analyzed to examine various influential factors on the injury severity of pedestrian crashes. The crash data extracted from the Statewide Integrated Traffic Records System (SWITRS) include five categorical levels of injury severity in traffic crashes also in addition to detailed information about the features of each crash. This study applied an ordered probit model for injury severity analysis to specify the ordinal nature of injury categories. To draw unbiased implications from the estimated parameters, statistical tests were performed on the parameters based on robust standard errors. Then, the marginal effects of each variable on the likelihood of each injury level were computed. The variables that significantly increased the probability of severe injury and fatality were: i) age (under age 15 and over age 65), alcohol consumption and cell phone use among pedestrian characteristics; ii) nighttime, weekends and rainy weather among environmental characteristics; and iii) influence of alcohol, larger vehicles (pickups, buses and trucks) and vehicle proceeding straight when striking a pedestrian among crash characteristics. Crash characteristics were found to influence significantly on the level of pedestrian injury. Based on the findings of this analysis, policy implications and countermeasures are also discussed
Investigation of Attributes of Kinematic Waves Preceding Traffic Collisions
No full textThe present study examines attributes of backward-moving kinematic waves that preceded traffic collisions in the vicinity of a recurrent bottleneck and compares with the ones from collision free days. The speed of backward moving waves accompanying traffic collisions were faster than the ones observed from collision free days. Traffic states observed prior to collisions were closer to the semi-congested state. Duration and frequency of kinematic waves, and the speed difference in traffic states before and after the passage of waves are also examined. Attributes of kinematic waves accompanying the secondary traffic collisions are briefly discussed in the paper. The findings indicate different attributes of kinematic waves can be used as a safety surrogate measure
The trend in suicide methods in South Korea in 1997–2015
No full text© 2017 Taylor & Francis. South Korea exhibited the highest crude suicide rate in the world. To better understand this phenomenon, the author analyzed all suicides in South Korea from 1997 to 2015 and charted the trend in suicide methods by gender. Over time, both genders rapidly chose hanging for suicide at the expense of drug/pesticide poisoning. Gassing was hardly used in the beginning, but its recent gain in use is noteworthy. Including undetermined deaths did not change the main results. The author regressed hanging on demographics and found that hanging was particularly chosen by ever-married men of prime working age with a respectable level of education
도시철도 정거장의 설계와 운영을 위한 서비스 기능성 분석
No full text학위논문(박사) - 한국과학기술원 : 조천식모빌리티대학원, 2022.8,[vii, 195 p. :]Since subway network performs as a backbone in metropolitan transportation network, its stations function as transit hubs connecting with other modes. As passengers can use subway services only through visiting the stations, the most fundamental role of the stations is working as a medium for passengers’ boarding and alighting by managing vehicular departure and arrival. In spite of this importance, while the previous studies and policies focused on the vehicular operation in operators’ perspectives, there have been still inconvenience and danger for passengers inside and around subway stations during access for services.
To solve these problems, this study defined the serviceability constituents of subway stations in the point of view by passengers’ trip inside and around them. From the definition, author conducted the duration modeling (accelerated failure time modeling) and count – data modeling (negative binomial regression) – based quantitative analysis on the causality between representative measurement indices and their influential factors for each serviceability element. Using the results by these statistical estimations the research suggested the infrastructural implications targeting each design, construction, operation and maintenance phase of subway stations. In conclusion, this study found that moving inside subway stations, safety derived from the process, access by walk or bike, and intermodal connection from buses, are all explainable mainly by the elapsed time or injury event occurrences. In addition, these measurement indices are dependent to the related human or built environmental factors inside and around the stations. Intermodal or mechanical means to narrow this spatiotemporal gap between visiting passengers and the stations due to the fixed architecture determines the promptness and safety level consequently. Based on the findings, author proposed the concrete implications corresponding to each design and construction procedure, with considering various exterior constraints against construction authorities and operators. This study also proposed the foundational framework to check the financial feasibility of infrastructural improvement alternatives and action planning in detail.한국과학기술원 :조천식모빌리티대학원
A new insight into the gender gap in math
No full textIn the Early Childhood Longitudinal Study Kindergarten Cohort, I find that the gender gap is not uniform across the distribution of math skills and that these quantile-specific gaps vary with age. Specifically, girls at the top of the distribution initially fall behind boys but manage to catch up later. At the same time, girls in the lower parts of the distribution lose ground. In fifth grade, a gender gap of 0.2 standard deviation, about 2.5 months of schooling, is observed across the entire distribution. Overall, these patterns indicate the possibility that low performing girls become worse and vice versa. These results demonstrate important dynamics of the gap that are relevant for policy, but that the mean gap fails to show. © 2010 The Author. Bulletin of Economic Research © 2010 Blackwell Publishing Ltd and the Board of Trustees of the Bulletin of Economic Research
Impairment of Multi-Finger Force Control in Adult Patients with Dyskinetic Cerebral Palsy
No full textPURPOSE This study aimed to investigate the impact of cerebral palsy (CP) on motor control strategies, with a focus on understanding the altered capability of multi-finger force control in adult patients with dyskinetic CP. METHODS Eight adults with dyskinetic CP and ten age- and sex-matched healthy controls participated in this study. The participants performed three force production tasks using four fingers of the dominant hand under isometric conditions: maximum voluntary contraction (MVC) to assess maximum force production, a ramp task to evaluate finger interdependency (enslaving), and a pulse task to examine the ability to rapidly and precisely adjust force. The co-contraction index (CCI) of finger flexor and extensor was also determined during steady state and pulse force production. RESULTS Patients with dyskinetic CP demonstrated significant impairments in finger force control compared to healthy controls. Specifically, the accuracy and consistency of force production were reduced in the CP group, and they exhibited a longer time to peak pulse force. The CP group also showed increased finger interdependency and elevated CCI during pulse force production, suggesting a greater reliance on co-contraction and less efficient motor control strategies. CONCLUSIONS This study highlights the distinct motor control deficits in individuals with dyskinetic CP, particularly in tasks requiring rapid and precise finger force adjustment. These results have important implications for the functional rehabilitation of patients with CP. Therapies aimed at reducing excessive co-contraction and decreasing finger interdependency may be beneficial for improving muscle coordination and overall motor function
거시적 교통기본도 기반의 개인 맞춤형 경로 생성 전략
No full text학위논문(박사) - 한국과학기술원 : 조천식녹색교통대학원, 2020.8,[v, 118 p. :]To understand traffic phenomena and further to solve congestion problems, various traffic flow models have been developed. Recently, there have been many attempts to manage congestion at the network level using macroscopic fundamental diagrams (MFD), because these have the advantage of enabling effective management of the network traffic while reducing the complexity of the model. In this study, the author proposes a method to utilize large-scale data collected at the micro level of individual vehicles for a macroscopic traffic management strategy at the city level. First, this study investigates how to process and modify the transportation big data, and use it to estimate the empirical MFDs for a real metropolitan city. This study analyzes the bifurcation phenomenon in empirically estimated MFDs to find causal factors, and create a method to improve network performance based on the findings. To this end, this study proposes a utility-maximized route guidance strategy considering individual route choice preferences. Applying the proposed strategy through Model Predictive Control (MPC)-based simulation yielded positive effects on both network performance and drivers’ utility. Accordingly, it can be expected that the proposed strategy will increase drivers’ route compliance rate. The simulation also showed that the higher the compliance rate, the better the effectiveness of the proposed strategy.한국과학기술원 :조천식녹색교통대학원
도시활력: 대중교통중심 이동 및 활동에 대한 토지이용과 도시형태의 영향
No full text학위논문(박사) - 한국과학기술원 : 조천식녹색교통대학원, 2020.8,[vi, 150 p. :]This dissertation aimed to understand the environmental factors enhancing urban vitality. The city of Seoul in South Korea was tested to explore the relationships between transit-oriented urban mobility, urban activity, land use, and urban form through a data-driven approach. The analyses in this dissertation were conducted over three steps. The first analysis validated the interactive relationship between transit-oriented urban mobility and urban activity, from the geographical and temporal perspectives. The second analysis grouped the subway stations based on the similarity in temporal profiles of ridership using clustering analysis and evaluated the effects of land use and urban form on temporally different trajectories and volumes of ridership using trajectory modeling. In the last analysis, the author defined the reasonable areal unit to analyze urban activity from the urban vitality perspective, and examined the influential attributes of land use and urban form for vibrant activity using spatial regression modeling. The outcomes of these analyses offer a chance to understand the current urban structure and the requirements for creating vibrant environments in cities. The results show that the city has a severed structure by regional functions, but the dense, widespread transit network supports to sustain vibrant citizens’ mobilities and activities at the city level as it reduces the auto-dependency of citizens. At the neighborhood level, the results verify that transit- and walking-friendly environments encourage a vibrant community, which involves the well-connected streets, small block size, and small plot size. In addition, the analysis result of activity indicates that the residential use should be placed in balance with the neighborhood commercial, education, and welfare uses. The findings of this dissertation can provide the fields of urban and transportation planning with a comprehensive insight into creating a vibrant and sustainable city and also improving the quality of citizens’ daily lives.한국과학기술원 :조천식녹색교통대학원
Now, the Taller Die Earlier: The Curse of Cancer
No full text© 2015 The Author 2015. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved.This study estimates the relationship between height and mortality. Individuals in the National Health Interview Survey 1986, a nationally representative U.S. sample, are linked to death certificate data until December 31, 2006. We analyze this relationship in 14,440 men and 16,390 women aged 25+. We employ the Cox proportional hazards model, controlling for birthday and education. An additional inch increase in height is related to a hazard ratio of death from all causes that is 2.2% higher for men and 2.5% higher for women. The findings are robust to changing survival distributions, and further analyses indicate that the figures are lower bounds. This relationship is mainly driven by the positive relationship between height and development of cancer. An additional inch increase in height is related to a hazard ratio of death from malignant neoplasms that is 7.1% higher for men and 5.7% higher for women. In contrast to the negative relationship between height and mortality in the past, this relationship is now positive. This demonstrates the success and accessibility of medical technology in treating patients with many acute and chronic diseases other than cancer
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