Chungwon Lee

Thrombospondin-1, vascular endothelial growth factor expression and their relationship with p53 status in prostate cancer and benign prostatic hyperplasia

Objective To evaluate the expression of thrombospondin‐1 (TSP‐1, a potent inhibitor of angiogenesis) and vascular endothelial growth factor (VEGF, an important angiogenic factor in solid tumours) in prostate cancer, and their relationship with p53 status.

Progress in sample preparation system for the Seoul National University AMS facility

Abstract The Seoul National University AMS Laboratory has developed a sample preparation system for AMS measurement. Graphite targets are prepared via the reduction of carbon dioxide over a Fe catalyst. The carbon dioxide gases are produced by combusting pretreated organic samples with CuO and silver wire in a sealed quartz tube. Each combustion produces ca. 2 mg of graphite that is loaded into the target. So far we have been successful in extracting and analyzing 12C− current up to 10 mA in stable condition by Cs sputtering onto the targets.

Intermediate-risk grouping of cervical cancer patients treated with radical hysterectomy: a Korean Gynecologic Oncology Group study

Background:In this study, we sought to identify a criterion for the intermediate-risk grouping of patients with cervical cancer who exhibit any intermediate-risk factor after radical hysterectomy.Methods:In total, 2158 patients with pathologically proven stage IB–IIA cervical cancer with any intermediate-risk factor after radical hysterectomy were randomly assigned to two groups, a development group and a validation group, at a ratio of 3 : 1 (1620 patients:538 patients). To predict recurrence, multivariate models were developed using the development group. The ability of the models to discriminate between groups was validated using the log-rank test and receiver operating characteristic (ROC) analysis.Results:Four factors (histology, tumour size, deep stromal invasion (DSI), and lymphovascular space involvement (LVSI)) were significantly associated with disease recurrence and included in the models. Among the nine possible combinations of the four variables, models consisting of any two of the four intermediate-risk factors (tumour size ⩾3 cm, DSI of the outer third of the cervix, LVSI, and adenocarcinoma or adenosquamous carcinoma histology) demonstrated the best performance for predicting recurrence.Conclusion:This study identified a ‘four-factor model’ in which the presence of any two factors may be useful for predicting recurrence in patients with cervical cancer treated with radical hysterectomy.

Finite mixture modeling for vehicle crash data with application to hotspot identification

The application of finite mixture regression models has recently gained an interest from highway safety researchers because of its considerable potential for addressing unobserved heterogeneity. Finite mixture models assume that the observations of a sample arise from two or more unobserved components with unknown proportions. Both fixed and varying weight parameter models have been shown to be useful for explaining the heterogeneity and the nature of the dispersion in crash data. Given the superior performance of the finite mixture model, this study, using observed and simulated data, investigated the relative performance of the finite mixture model and the traditional negative binomial (NB) model in terms of hotspot identification. For the observed data, rural multilane segment crash data for divided highways in California and Texas were used. The results showed that the difference measured by the percentage deviation in ranking orders was relatively small for this dataset. Nevertheless, the ranking results from the finite mixture model were considered more reliable than the NB model because of the better model specification. This finding was also supported by the simulation study which produced a high number of false positives and negatives when a mis-specified model was used for hotspot identification. Regarding an optimal threshold value for identifying hotspots, another simulation analysis indicated that there is a discrepancy between false discovery (increasing) and false negative rates (decreasing). Since the costs associated with false positives and false negatives are different, it is suggested that the selected optimal threshold value should be decided by considering the trade-offs between these two costs so that unnecessary expenses are minimized.

Establishment and characterization of seven human renal cell carcinoma cell lines

Objective To establish human renal cell carcinoma (RCC) cell lines, and to investigate the cell phenotypes and molecular characteristics of human RCC cell lines and their corresponding tumour tissues.

User Equilibrium-Based Location Model of Rapid Charging Stations for Electric Vehicles with Batteries That Have Different States of Charge

A model was developed for the location of rapid charging stations for electric vehicles (EVs) in urban areas, taking into account the batteries’ state of charge and users’ charging and traveling behaviors. EVs are one means of preparing for the energy crisis and of reducing greenhouse gas emissions. To help relieve range anxiety, an adequate number of EV charging stations must be constructed. Rapid charging stations are needed in urban areas because there is inadequate space for slow-charging equipment. The objective function of the model is to minimize EVs’ travel fail distance and the total travel time of the entire network when the link flow is determined by a user equilibrium assignment. The remaining fuel range (RFR) at the origin node is assumed to follow a probabilistic distribution to reflect users’ charging behavior or technical development. The results indicate that the model described in this paper can identify locations for charging stations by using a probabilistic distribution function for the RFR. The location model, which was developed on the basis of user equilibrium assignment, is likely to consider the congested traffic conditions of urban areas, to avoid locating charging stations where they could cause additional traffic congestion. The proposed model can assist decision makers in developing policies that encourage the use of EVs, and it will be useful in developing an appropriate budget for implementing the plan.

Local and Iterative Searches for Combined Signal Control and Assignment Problem: Implementation and Numerical Examples

Traffic signal-setting policies and traffic assignment procedures are mutually dependent. The combined signal control and traffic assignment problem deals with this interaction. With the total travel time minimization objective, gradient-based local search methods are implemented. Deterministic user equilibrium is the selected user route choice rule, Webster’s delay curve is the link performance function, and green-time-per-cycle ratios are decision variables. Three solution codes are implemented, resulting in six variations including intersections with multiphase operation and overlapping traffic movements. For reference, the iterative approach is also coded, and all codes are tested in four example networks at five demand levels. The results show the numerical gradient estimation procedure performs best, although the simplified local searches reduce the large network computational burden. Demand level as well as network size affects the relative performance of the local and iterative approaches. As demand level becomes higher, (a) in the small network, the local search tends to outperform the iterative search, and (b) in the large network, the opposite result is obtained.

Safety Performance Functions Reflecting Categorical Impact of Exposure Variables for Freeways

The aim of this study is to develop safety performance functions reflecting the categorical impact of exposure variables that may vary with freeway segments. A four-step procedure is constructed. It includes clustering analysis, distribution selection, model specification, and model integration. First, clustering analysis is employed to classify freeway segments into three similar groups. A goodness-of-fit test is performed to select suitable distributions for the safety performance functions of each of the three groups. Three forms of relationships are compared between crash frequency and exposure variables, and the best one is selected by using statistical indexes. Two final models, based on the evaluations performed by a test for taste variations and a paired asymptotic t-test, are proposed: one for fatal injury crashes and one for total crashes. All coefficients and constants in the proposed models are statistically significant. In addition, both models show higher statistical significance than the models reflecting constant relationships between crash frequency and exposure variables. The proposed four-step procedure for safety performance functions makes it possible to predict crash frequency more accurately, and the procedure can be easily applied to predict the number of crashes without additional data or complex simulation procedures. If additional explanatory variables are available for criteria on the difference and similarity, the ability to explain the data may be enhanced. It would be necessary to select an appropriate tool for characteristics of targeted roads; this process is a subject for further research.

Traffic Information and Some Business Models

In the era of ITS (intelligent transport systems), traffic information plays an important role in both urban location and travel choices. The e-business such as cyber shopping mall, location commerce, and mobile commerce will eventually make the traffic information more and more important and will be a good item to be treated as an object of business. This paper aims at an understanding the needs of traffic information and the emerging market opportunities for traditional transportation activities along with presentation of some business models. Worldwide, many ITS development and deployment programs deal with real-time traffic information that shows travel conditions on major freeways and arterials. These information services are viewed as key elements, necessary to the efficient management of urban traffic congestion. Although much emphasis has been placed on the improvement of traffic management systems with real-time traveler information, the effect of this on travelers and/or business is not well understood. These recent evolutions indicate that there are a growing number of private firms interested in traffic information technologies; a variety of dissemination methods have been explored, including radio and television broadcasts, changeable message signs and in-car devices. This suggests that the development of traffic information will provide business opportunities for new products and services in the traffic, information provision, traffic management and operations arenas. This paper focuses on some aspects of these emerging business opportunities: the technology trends having to do with the architecture of traffic management centers and the possibilities of integrating and disseminating traffic information to the end-user, and the activity of the industrial sector in designing, developing and deploying traveler information system with some business models initiated. Although this paper presents a comparative analysis of the current state of the art in advanced traveler information technology and its market potential, some issues including the traveler’s willingness to use traffic information services pre-trip and en-route should be addressed for further discussion.

Proactive Caching and Forwarding Schemes for Seamless Handover in IEEE WAVE Networks

The IEEE Wireless Access for Vehicular Environment (WAVE) standard consists of the IEEE 802.11p and the IEEE 1609 specifications supporting fast link establishment as well as broadband data communication in vehicular environment. Although the standard has been widely accepted by industry as well as highway authorities in many countries to be used for the radio communication infrastructure of the next-generation Intelligent Transport System (ITS), it remains open for further enhancements such as seamless handover support. This paper presents two proactive caching and forwarding schemes for seamless handover in IEEE WAVE networks: one for straight highway sections and the other for crossroads and junctions. Practical and efficient handover procedures, based on the proposed schemes, are also presented. Specifically, an on-board unit (OBU) informs the old road-side unit (RSU) about its departure from the coverage area such that the old RSU can forward the buffered packets to candidate RSUs for proactive caching. In handover scenarios around crossroads and junctions, the IEEE 802.11f Move-notify message is used by the new RSU to request the rest of candidate RSUs to purge the cached packets in order to prevent the waste of radio resource. Simulation results show that the proposed schemes outperform conventional schemes.