Speeding is one of the principal causes of traffic accidents that harm not only the safety of pedestrians but also the driver himself and others. However, empirical studies on speeding behavior are mostly survey research and identification of cause-and-effect relationship is unclear. Also the reliability of the study results cannot be verified using retrospective methods. To complement this point, it is important to conduct an experimental study, but realworld field research using real vehicles is almost impossible to apply equally to all subjects by controlling surrounding vehicles and signal systems. Therefore, in this study, we compared the overspeed characteristics of high risk driver types using driving simulator. The high risk driver types were divided in to four types: elderly driver, commercial driver, driver with more than 10 years of driving experience, and driver within 2 years of license acquisition. The overspeed characteristics were identified by using an index called Accumulated Speeding (AS). Based on overspeed characteristics differences between driver types, it is expected that additional education by driver type will be possible in the safety education using Driving Simulator.

Demand Responsive Transport (DRT) for the disabled is a special transportation mode for people with disabilities who have difficulties in moving. DRT for the disabled is one of the most important means of transportation for people with disabilities using wheelchairs because it provides door-to-door service with vehicles equipped with wheelchair boarding facilities. The Seoul city operated DRT for the disabled for the first time in Korea in 2003 and currently operates 487 vehicles. This study compared DRT for the disabled with domestic and foreign cases and analyzed usage pattern of DRT for the disabled in Seoul for the frequency of service use and waiting time. The DRT for the disabled usage pattern in Seoul showed that the number of use of weekends was smaller than that of weekdays, and it was used most at noon by the time of day. In the case of waiting time, days except Saturday were similar. On Saturday, the traffic jam was more severe than other days, so waiting time was higher than other days. By the time of day, the waiting time was higher due to the reduction of the number of vehicles in the evening and the nighttime, not the noon which had the highest number of use. As a result of analyzing day by day in four-time zones, it was analyzed that there were spatial differences in waiting time by time zone. This study is expected to be used to reduce the waiting time of DRT for the disabled through DRT for the disabled usage pattern analysis.

Car-sharing is one of the most popular cases of a shared economy. It is a sustainable service that enhances mobility by renting shared vehicles to meet user's purpose in short-time. Car-sharing has known that it is effective in reducing ownership of passenger cars, reducing traffic congestion, and improving the environment. In Korea, a variety of car-sharing services have been launched, and since 2012, Korea Land & Housing Corporation (LH) has started to introduce HappyCar service for residents of public rental housing complexes nationwide. Public rental housing complexes have three types of complexes, one of which is complex for the low-income households. The purpose of this study is to find out the factors affecting the use of carsharing for low-income people using Poisson regression analysis with 2017 HappyCar usage data. Data including outliers was filtered and explanatory variables (age, sex, and accessibility of public transportation around rental housing complexes) were selected through correlation analysis. The results of this study are expected to be useful for analysis of carsharing low-income users' behavior, demand forecasting, and the establishment of shared transportation policies in the future.

Human umbilical cord is easy to obtain because it is discarded after birth, so that ethical issues can be avoided. Chondrogenesis studies using MSCs from bone marrow, cord blood, and adipose have indicated that TGFβ3 and BMP6 stimulate chondrogenesis. Therefore, we investigated chondrogenesis of hUC-MSCs on TGFβ3, BMP6, and combination of the two growth factors. We initiated chondrogenesis of cells by application of physical forces to form 3D cell clusters. After initiation, we designated four experimental groups for differentiation of cells, as follows: control, 10 ng/mL TGFβ3, 100 ng/mL BMP6, and the combination of 5 ng/mL TGFβ3 and 50 ng/mL BMP6. For analysis of chondrogenesis, GAG contents, mRNA expression, histological analysis and immunohistochemistry (IHC) were performed. For analysis of GAG contents, GAG assay was performed and RT-PCR was performed for determination of chondrogenic markers. Histological analysis was performed through safranin O, alcian blue, and IHC was performed using collagen type I and II. GAG contents were increased 184% by TGFβ3, 147% by BMP6, and 189% by the combination of TGFβ3 and BMP6, compared to control. The growth factors improved collagen II and aggrecan expression; in particular, TGFβ3 and BMP6 showed a synergistic effect, compared to only TGFβ3 or BMP6 treated. The results of histological and IHC analysis indicated that chondrogenic differentiation in TGFβ3 and the combination of TGFβ3 and BMP6 showed more cartilage deposition. In conclusion, TGFβ3 and BMP6 differentiated hUC-MSCs into chondrogenic clusters of the combination treatment of the two growth factors showed more efficient chondrogenic ability.

Dlx3 and Dlx5 are homeobox domain proteins and are well-known regulators of osteoblastic differentiation. Since possible reciprocal relationships between osteogenic and adipogenic differentiation in mesenchymal stem cells exist, we examined the regulatory role of Dlx3 and Dlx5 on adipogenic differentiation using human dental pulp stem cells. Over-expression of Dlx3 and Dlx5 stimulated osteogenic differentiation but inhibited adipogenic differentiation of human dental pulp stem cells. Dlx3 and Dlx5 suppressed the expression of adipogenic marker genes such as C/EBPα, PPARγ, aP2 and lipoprotein lipase. Adipogenic stimuli suppressed the mRNA levels of Dlx3 and Dlx5, whereas osteogenic stimuli enhanced the expression of Dlx3 and Dlx5 in 3T3-L1 preadipocytes. These results suggest that Dlx3 and Dlx5 exert a stimulatory effect on osteogenic differentiation of stem cells through the inhibition of adipogenic differ¬entiation as well as direct stimulation.

Endothelial cells are a vital constituent of most mammalian organs and are required to maintain the integrity of these tissues. These cells also play a major role in angiogenesis, inflammatory reactions, and in the regulation of thrombosis. Angiogenesis facilitates pulp formation and produces the vessels which are essential for the maintenance of tooth homeostasis. These vessels can also be used in bone and tissue regeneration, and in surgical procedures to place implants or to remove cancerous tissue. Furthermore, endothelial cell regeneration is the most critical component of the tooth generation process. The aim of the present study was to stimulate endothelial regeneration at a site of acute cyclophosphamide (CP)-induced endothelial injury by treatment with human umbilical cord-derived endothelial/mesenchymal stem cells (hEPCs). We randomly assigned 16 to 20-week-old female NOD/SCID mice into three separate groups, a hEPC (1 × 105 cells) transplanted, 300mg/kg CP treated and saline (control) group. The mice were sacrificed on days 5 and 10 and blood was collected via the abdominal aorta for analysis. The alanine transaminase (ALT), aspartate aminotransferase (AST), serum alkaline phosphatase (s-ALP), and albumin (ALB) levels were then evaluated. Tissue sections from the livers and kidneys were stained with hematoxylin and eosin (HE) for microscopic analysis and were subjected to immunohistochemistry to evaluate any changes in the endothelial layer. CP treatment caused a weight reduction after one day. The kidney/body weight ratio increased in the hEPC treated animals compared with the CP only group at 10 days. Moreover, hEPC treatment resulted in reduced s-ALP, AST, ALT levels compared with the CP only group at 10 days. The CP only animals further showed endothelial injuries at five days which were recovered by hEPC treatment at 10 days. The number of CD31-positive cells was increased by hEPC treatment at both 5 and 10 days. In conclusion, the CP-induced disruption of endothelial cells is recovered by hEPC treatment, indicating that hEPC transplantation has potential benefits in the treatment of endothelial damage.

The stem cell research is emerging as a cutting edge topic for a new treatment for many chronic diseases. Recently, dental stem cell would be possible for regeneration of tooth itself as well as periodontal tissue. However, the study of the cell characterization is scarce. Therefore, we performed the genetic profiling and the characterization of mouse fetus/neonate derived dental tissue and cell to find the identification during dental development. We separated dental arch from mandibles of 14.5 d fetal mice and neonate 0 d under the stereoscope, and isolated dental cells primarily from the tissues. Then, we examined morphology and the gene expression profiles of the primary cells and dental tissues from fetus/neonate and adult with RT-PCR. Primary dental cells showed heterogeneous but the majority was shown as fibroblast-like morphology. The change of population doubling time levels (PDLs) showed that the primary dental cells have growth potential and could be expanded under our culture conditions without reduction of growth rate. Immunocytochemical and flow cytometric analyses were performed to characterize the primary dental cell populations from both of fetus (E14.5) and neonate. Alpha smooth muscle actin (α-SMA), vimentin, and von Willebrand factor showed strong expression, but desmin positive cells were not detected in the primary dental cells. Most of the markers were not uniformly expressed, but found in subsets of cells, indicating that the primary dental cell population is heterogeneous, and characteristics of the populations were changed during culture period. And mesenchymal stem cell markers were highly expressed. Gene expression profile showed Wnt family and its related signaling molecules, growth factors, transcription factors and tooth specific molecules were expressed both fetal and neonatal tissue. The tooth specific genes (enamelin, amelogenin, and DSPP) only expressed in neonate and adult stage. These expression patterns appeared same as primary fetal and neonatal cells. In this study we isolated primary cells from whole mandible of fetal and neonatal mice. And we investigated the characteristics of the primary cells and the profile of gene expressions, which are involved in epithelial-mesenchymal interactions during tooth development. Taken together, the primary dental cells in early passages or fetal and neonatal mandibles could be useful stem cell resources.