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Sungkyunkwan University is a private research university with campuses in Seoul and Suwon. Originally, it was founded in 1398 by the Joseon Dynasty located in the heart of central Seoul. It was authorized as Sungkyunkwan, the foremost educational institution of Joseon, by the great code of the state administration pertaining to the royal assent.Today, the university has two campuses: the Humanities and Social science Campus in Seoul, and the Natural science Campus in Suwon. Eighteen schools and three colleges offer degrees at the bachelor's level, and twelve graduate schools confer various degrees at both the masters and doctoral levels. SKKU offers Korea’s first fully English-taught Global MBA program, which has gained tremendous international recognition. SKKU also has one of the best medical schools in South Korea, which is affiliated with the world-famous Samsung Medical Center. Samsung partnered with SKKU in the period of 1965-1977 and took up its partnership in 1996. Recent years have seen a trend of SKKU rising in university rankings, consistently placing in the top 5 nationally. Wikipedia.

Kim S.G.,Sungkyunkwan University
Journal of the Korean Medical Association | Year: 2015

The outbreak of Middle East respiratory syndrome coronavirus(MERS-CoV) infection in South Korea has become a public health threat. There are many confirmed cases of MERS in healthcare workers. Understanding the nature of the infection and the mechanismof transmission will be a useful lesson. This paper gathers data from the press records in KCDC from May 20thto June 26th 2015to identify the age, sex, occupation and etiologic exposure of exposed healthcare workersin order to come up with a response plan. By June 26th, 2015, there were 181 confirmed cases of MERS-CoV infection in Korea. 36 (19.9%) of them were healthcare workers. These healthcare workers were exposed to MERS-CoV across 12 healthcare facilities, including Samsung Medical Center and Dae-Chung Hospital; threewere infected inside ambulances. Their occupational categories are as follows: 7 doctors (19.4%), 12 nurses (33.3%), 9 caregivers orgeriatric care assistants(25.0%), and 8 others (22.2%). These healthcare workers were infected by 12 super-spreaders. 30 of the workers(83.3%) were infected without being aware of their contact with MERS patients, while 6 (16.7%) were aware of this contact at the time of infection. The high number of confirmed cases of MERS-CoV in healthcare workers is direct proof of the failure of crisis communication in South Korea, and the delay in the diagnosis of the index case was due to the lack of risk communication regarding the threat of a MERS outbreak. Because the spread of MERS usually occurs via healthcare-associated transmission, infection control inealthcare facilities must be strengthened. © Korean Medical Association.

Kang J.-S.,Sungkyunkwan University | Krauss R.S.,Mount Sinai School of Medicine
Current Opinion in Clinical Nutrition and Metabolic Care | Year: 2010

Purpose of review: Skeletal muscle development serves as a paradigm for cell lineage specification and cell differentiation. Adult skeletal muscle has high regenerative capacity, with satellite cells the primary source of this capability. The present review describes Recent findings: on developmental and adult myogenesis with emphasis on emerging distinctions between various muscle groups and stages of myogenesis. Recent findings: Muscle progenitors of the body are derived from multipotent cells of the dermomyotome and express the transcription factors Pax3 and Pax7. These cells self-renew or induce expression of myogenic regulatory factors (MRFs) and differentiate. The roles of Pax3, Pax7 and specific myogenic regulatory factor+ progenitor populations in trunk and limb myogenesis have been identified through cell ablation in the mouse. Various head muscles and associated satellite cells have differing developmental origins, and rely on distinct combinations of transcriptional regulators, than trunk and limb muscles. Several genetic and sorting protocols demonstrate that satellite cells are heterogeneous with some possessing stem cell properties; the relative roles of lineage and niche in these properties are being explored. Although cellular mechanisms of developmental, postnatal and adult regenerative myogenesis are thought to be similar, recent studies reveal distinct genetic requirements for embryonic, fetal, postnatal and adult regenerative myogenesis. Summary: Genetic determinants of formation or repair of various muscles during different stages of myogenesis are unexpectedly diverse. Future studies should illuminate these differences, as well as mechanisms that underlie stem cell properties of satellite cells. © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins.

PURPOSE:: To investigate the anatomical and refractive outcomes in patients with Type 1 retinopathy of prematurity in Zone I. METHODS:: The medical records of 101 eyes of 51 consecutive infants with Type 1 retinopathy of prematurity in Zone I were analyzed. Infants were treated by conventional laser photocoagulation (Group I), combined intravitreal bevacizumab injection and Zone I sparing laser (Group II), or intravitreal bevacizumab with deferred laser treatment (Group III). The proportion of unfavorable anatomical outcomes including retinal fold, disc dragging, retrolental tissue obscuring the view of the posterior pole, retinal detachment, and early refractive errors were compared among the three groups. RESULTS:: The mean gestational age at birth and the birth weight of all 51 infants were 24.3 ± 1.1 weeks and 646 ± 143 g, respectively. In Group I, an unfavorable anatomical outcome was observed in 10 of 44 eyes (22.7%). In contrast, in Groups II and III, all eyes showed favorable anatomical outcomes without reactivation or retreatment. The refractive error was less myopic in Group III than in Groups I and II (spherical equivalent of −4.62 ± 4.00 D in Group I, −5.53 ± 2.21 D in Group II, and −1.40 ± 2.19 D in Group III; P < 0.001). CONCLUSION:: In Type 1 retinopathy of prematurity in Zone I, intravitreal bevacizumab with concomitant or deferred laser therapy yielded a better anatomical outcome than conventional laser therapy alone. Moreover, intravitreal bevacizumab with deferred laser treatment resulted in less myopic refractive error. © 2016 by Ophthalmic Communications Society, Inc.

Han C.-K.,Samsung | Choi H.-K.,Sungkyunkwan University
IEEE Transactions on Mobile Computing | Year: 2014

The goal of 3GPP Long Term Evolution/System Architecture Evolution (LTE/SAE) is to move mobile cellular wireless technology into its fourth generation. One of the unique challenges of fourth-generation technology is how to close a security gap through which a single compromised or malicious device can jeopardize an entire mobile network because of the open nature of these networks. To meet this challenge, handover key management in the 3GPP LTE/SAE has been designed to revoke any compromised key(s) and as a consequence isolate corrupted network devices. This paper, however, identifies and details the vulnerability of this handover key management to what are called desynchronization attacks; such attacks jeopardize secure communication between users and mobile networks. Although periodic updates of the root key are an integral part of handover key management, our work here emphasizes how essential these updates are to minimizing the effect of desynchronization attacks that, as of now, cannot be effectively prevented. Our main contribution, however, is to explore how network operators can determine for themselves an optimal interval for updates that minimizes the signaling load they impose while protecting the security of user traffic. Our analytical and simulation studies demonstrate the impact of the key update interval on such performance criteria as network topology and user mobility. © 2014 IEEE.

Abdelnasser A.,University of Manitoba | Hossain E.,University of Manitoba | Kim D.I.,Sungkyunkwan University
IEEE Transactions on Wireless Communications | Year: 2014

Small cells such as femtocells overlaying the macrocells can enhance the coverage and capacity of cellular wireless networks and increase the spectrum efficiency by reusing the frequency spectrum assigned to the macrocells in a universal frequency reuse fashion. However, management of both the cross-tier and co-tier interferences is one of the most critical issues for such a two-tier cellular network. Centralized solutions for interference management in a two-tier cellular network with orthogonal frequency-division multiple access (OFDMA), which yield optimal/near-optimal performance, are impractical due to the computational complexity. Distributed solutions, on the other hand, lack the superiority of centralized schemes. In this paper, we propose a semi-distributed (hierarchical) interference management scheme based on joint clustering and resource allocation for femtocells. The problem is formulated as a mixed integer non-linear program (MINLP). The solution is obtained by dividing the problem into two sub-problems, where the related tasks are shared between the femto gateway (FGW) and femtocells. The FGW is responsible for clustering, where correlation clustering is used as a method for femtocell grouping. In this context, a low-complexity approach for solving the clustering problem is used based on semi-definite programming (SDP). In addition, an algorithm is proposed to reduce the search range for the best cluster configuration. For a given cluster configuration, within each cluster, one femto access point (FAP) is elected as a cluster head (CH) that is responsible for resource allocation among the femtocells in that cluster. The CH performs sub-channel and power allocation in two steps iteratively, where a low-complexity heuristic is proposed for the sub-channel allocation phase. Numerical results show the performance gains due to clustering in comparison to other related schemes. Also, the proposed correlation clustering scheme offers performance, which is close to that of the optimal clustering, with a lower complexity. © 2014 IEEE.

Niyato D.,Nanyang Technological University | Wang P.,Nanyang Technological University | Kim D.I.,Sungkyunkwan University
IEEE Transactions on Wireless Communications | Year: 2014

With the pervasiveness of wireless devices, machine-to-machine (M2M) communications or machine-type-communications (MTC) is emerging to support data transfer among devices without human interaction. In this paper, we introduce a tractable queueing model for performance modeling and analysis for heterogeneous MTC. We then demonstrate versatile applications of the proposed queueing model. Firstly, we use the queueing model to study the coexistence between M2M communications of MTC devices and human-to-human (H2H) communications in the same networks. We also consider more sophisticated settings, where the MTC user equipments (UEs) are able to perform the transmission to the macro Evolved Node B (eNodeB) or small-cell eNodeB, or perform the relay transmission. In addition, we extend our study to analyze the eNodeB selection and coalition formation for relay transmission when MTC UEs coexist with H2H UEs. In this case, we formulate the non-transferable utility (NTU) coalitional game to model the eNodeB selection and coalition formation for relay transmission. The performance evaluation reveals some interesting results. For example, the throughput of MTC UEs can be improved when the MTC UEs spend more time inactive due to lower contention in the network, compared with the case when the MTC UEs are mostly active. © 2014 IEEE.

Uhm S.,Institute for Advanced Engineering | Kim Y.D.,Sungkyunkwan University
Current Applied Physics | Year: 2014

Carbon dioxide is one of the greatest concerns worldwide, since it is not only a major greenhouse gas but also expected to be an important, sustainable resource for fuels and chemicals. The electrochemical conversion of carbon dioxide, based on solid electrolyte membrane reactors, has the promise to overcome the limitations of the conventional catalytic reactors such as the limited conversion and kinetics, relatively low selectivity and high energy consumption. In this review, electrocatalysts and solid oxide electrolytes, both proton and oxide ion conductors as core materials in an electrochemical ceramic membrane reactor have been reviewed and particular emphasis is placed on their application to synthesize carbon monoxide and hydrogen. © 2014 Elsevier B.V. All rights reserved.

Hasan M.,University of Manitoba | Hossain E.,University of Manitoba | Kim D.I.,Sungkyunkwan University
IEEE Transactions on Wireless Communications | Year: 2014

Device-to-device (D2D) communication in cellular networks allows direct transmission between two cellular devices with local communication needs. Due to the increasing number of autonomous heterogeneous devices in future mobile networks, an efficient resource allocation scheme is required to maximize network throughput and achieve higher spectral efficiency. In this paper, performance of network-integrated D2D communication under channel uncertainties is investigated where D2D traffic is carried through relay nodes. Considering a multi-user and multi-relay network, we propose a robust distributed solution for resource allocation with a view to maximizing network sum-rate when the interference from other relay nodes and the link gains are uncertain. An optimization problem is formulated for allocating radio resources at the relays to maximize end-to-end rate as well as satisfy the quality-of-service (QoS) requirements for cellular and D2D user equipments under total power constraint. Each of the uncertain parameters is modeled by a bounded distance between its estimated and bounded values. We show that the robust problem is convex and a gradient-aided dual decomposition algorithm is applied to allocate radio resources in a distributed manner. Finally, to reduce the cost of robustness defined as the reduction of achievable sum-rate, we utilize the chance constraint approach to achieve a trade-off between robustness and optimality. The numerical results show that there is a distance threshold beyond which relay-aided D2D communication significantly improves network performance when compared to direct communication between D2D peers. © 2002-2012 IEEE.

Xu K.,Nanjing University of Aeronautics and Astronautics | Das K.C.,Sungkyunkwan University | Balachandran S.,SASTRA University
Match | Year: 2014

For a (molecular) graph, the first and second Zagreb indices (M1 and M2) are two well-known topological indices in chemical graph theory introduced in 1972 by Gutman and Trinajstić. Let Gn,m be the set of connected graphs of order n and with m edges. In this paper we characterize the extremal graphs from Gn,m with n + 2 ≥ m ≥ 2n-4 with maximal first Zagreb index and from Gn,m with m-n = (k 2)-k for k ≥ 4 with maximal second Zagreb index, respectively. Finally a related conjecture has been proposed to the extremal graphs with respect to second Zagreb index.

Kim K.J.,Sungkyunkwan University
Telematics and Informatics | Year: 2014

Based on the Computers Are Social Actors (CASA) paradigm, this study extends the expectations regarding the superiority of specialists over generalists to mobile technology by examining whether the specialization of a hardware agent (i.e., a smartphone) and a software agent (i.e., an application) has psychological effects on smartphone users who are exposed to mobile advertisements. Results from a between-subjects experiment (N = 80) show that specialist smartphones and applications induce greater trust in advertisements and an increased purchase intention toward the advertised products than generalist smartphones and applications. In addition, the effects of specialization on purchase intention are mediated by trust in advertisements. Theoretical and practical implications of these findings are discussed. © 2014 Elsevier Ltd. All rights reserved.

Park E.,Korea Advanced Institute of Science and Technology | Kim K.J.,Sungkyunkwan University
Telematics and Informatics | Year: 2014

This study identifies and investigates a number of cognitive factors that contribute to shaping user perceptions of and attitude toward mobile cloud computing services by integrating these factors with the technology acceptance model. A structural equation modeling analysis is employed on data collected from 1099 survey samples, and results reveal that user acceptance of mobile cloud services is largely affected by perceived mobility, connectedness, security, quality of service and system, and satisfaction. Both theoretical and practical implications of the study's findings are discussed. © 2013 Elsevier Ltd. All rights reserved.

Weiss L.A.,Yale University | Dahanukar A.,Yale University | Dahanukar A.,University of California at Riverside | Kwon J.Y.,Yale University | And 3 more authors.
Neuron | Year: 2011

The extent of diversity among bitter-sensing neurons is a fundamental issue in the field of taste. Data are limited and conflicting as to whether bitter neurons are broadly tuned and uniform, resulting in indiscriminate avoidance of bitter stimuli, or diverse, allowing a more discerning evaluation of food sources. We provide a systematic analysis of how bitter taste is encoded by the major taste organ of the Drosophila head, the labellum. Each of 16 bitter compounds is tested physiologically against all 31 taste hairs, revealing responses that are diverse in magnitude and dynamics. Four functional classes of bitter neurons are defined. Four corresponding classes are defined through expression analysis of all 68 gustatory taste receptors. A receptor-to-neuron-to-tastant map is constructed. Misexpression of one receptor confers bitter responses as predicted by the map. These results reveal a degree of complexity that greatly expands the capacity of the system to encode bitter taste. © 2011 Elsevier Inc.

Kang B.,Sungkyunkwan University
Journal of Pediatric Gastroenterology and Nutrition | Year: 2016

OBJECTIVES:: We aimed to quantitatively investigate the therapeutic response to combined immunosuppression treatment by magnetic resonance enterography (MRE) in active luminal Crohnʼs disease in the pediatric population. METHODS:: Pediatric patients with moderate-to-severe luminal Crohnʼs disease who received scheduled infliximab and azathioprine were included in this preliminary study. Ileocolonoscopy and MRE were performed at baseline and at 1 year, and Simple Endoscopic Score for Crohnʼs Disease (SES-CD) and Magnetic Resonance Index of Activity (MaRIA) scores were calculated. The correlation between SES-CD and MaRIA scores were investigated with analysis per-person and per-segment. RESULTS:: A total 167 segments from 17 patients were evaluated by both ileocolonoscopy and MRE. SES-CD and MaRIA scores showed significant correlations on both per-person analysis (ρ?=?0.699, P?

Kim K.M.,Sungkyunkwan University
The Korean journal of gastroenterology = Taehan Sohwagi Hakhoe chi | Year: 2010

It is widely accepted that endoscopic submucosal dissection (ESD) is an important treatment option for cases of early gastric carcinoma where the probability of lymph node metastasis is very low. The resected ESD specimens are carefully examined by serial sections at 2 mm intervals, and if pathology reveals submucosal invasion more than 500 μm and/or lymphovascular invasion, or if the resection margin is involved by the tumor, surgery is recommended. In this point of view, thorough pathologic examination and reporting the accurate pathologic diagnosis of ESD specimen is very important. The diagnostic approach and pitfalls in the diagnosis of ESD specimen are reviewed.

To evaluate the efficacy of vitrectomy combined with intravitreal injection of triamcinolone acetonide (IVTA) and macular laser photocoagulation for the treatment of nontractional diabetic macular edema (DME) refractory to anti-vascular endothelial growth factor (VEGF) therapy. Twenty-eight eyes from 28 subjects who were diagnosed with nontractional DME refractory to three or more sequential anti-VEGF injections underwent sequential vitrectomy, IVTA, and macular laser photocoagulation. Changes in best-corrected visual acuity (BCVA) and central subfield thickness (CST) during the six months following vitrectomy were evaluated. Additionally, the CST and BCVA outcomes were compared with those of 26 eyes treated with the same triple therapy for nontractional DME refractory to conventional treatment, such as IVTA or macular laser photocoagulation, or both. The mean logarithm of the minimum angle of resolution BCVAs before and one, three, and six months after vitrectomy were 0.44 ± 0.15, 0.36 ± 0.18, 0.31 ± 0.14, and 0.34 ± 0.22, respectively. The mean CSTs were 433.3 ± 77.9, 329.9 ± 59.4, 307.2 ± 60.2, and 310.1 ± 80.1 microns, respectively. The values of both BCVA and CST at one, three, and six months were significantly improved from baseline (p < 0.05). The extent of CST reduction during the first month after triple therapy was greater in eyes refractory to conventional treatment than in eyes refractory to anti-VEGF (p = 0.012). Vitrectomy combined with IVTA and macular laser photocoagulation had a beneficial effect on both anatomical and functional outcomes in eyes with nontractional DME refractory to anti-VEGF therapy.

Shin D.,Sungkyunkwan University
Telematics and Informatics | Year: 2014

This study presents a case application of a socio-technical framework to assess and predict the development of the Internet of Things (IoT) in Korea. Applying a socio-technical system approach to the IoT, this paper seeks a clear understanding of how the IoT will evolve and stabilize in a smart environment. It investigates the complex interaction between social and technical aspects of the IoT, by highlighting the co-evolution, interaction, and interface, which constitute the next generation network environment. It describes the challenges in designing, deploying, and sustaining the diverse components of the IoT, and provides a snapshot of Korea's current approach to meeting this challenge. Finally, the findings of this study provide insights into these challenges and opportunities, by offering a socio-technical analysis of IoT development. The insights help to conceptualize how the IoT can be designed and situated within human-centered contexts. © 2014 Elsevier Ltd. All rights reserved.

This study was performed to evaluate the impact of extended-spectrum β-lactamase (ESBL)-producing bacteremia on outcome in patients with hematologic malignancy. We collected and analyzed data on 156 hematologic malignancy patients with Escherichia coli or Klebsiella pneumoniae bacteremia from the database of nationwide surveillance studies for bacteremia. Thirty-seven of the 156 patients (23.7%) harbored ESBL-producing bacteremia. No significant differences in underlying diseases were found in either group. The multivariate analysis showed that significant factors associated with ESBL-producing bacteremia were ICU care (OR = 7.03, 95% CI = 1.79-27.6) and nosocomial acquisition (OR = 5.66, 95% CI = 1.60-20.23). There was an association between prior receipt of cephalosporins and ESBL-producing bacteremia, although this association was not statistically significant (OR = 2.27, 95% CI = 0.99-5.23). The overall 30-day mortality rate of the study population was 20.4% (29/142), and the 30-day mortality rate for the ESBL group was significantly higher than that for the non-ESBL group (44.8% vs. 14.2%, P < 0.001). Multivariate analysis showed that ESBL-producing bacteremia was the most important risk factor associated with 30-day mortality (OR, 5.64; 95% CI, 1.91-16.67), along with ICU care (OR = 4.35, 95% CI = 1.16-16.26) and higher Pitt bacteremia score (per 1-point increment) (OR = 1.50, 95% CI = 1.18-1.92). In conclusion, ESBL-producing bacteremia was the most important risk factor associated with 30-day mortality in patients with hematologic malignancy, along with ICU care and higher Pitt bacteremia score. Our data suggest that determining the optimal empiric antimicrobial therapy in patients with hematologic malignancy is now becoming a challenge for clinicians in the era of multidrug-resistant Gram-negative bacilli.

Lee M.-S.,Sungkyunkwan University
Journal of Korean Medical Science | Year: 2014

The importance of innate immunity in host defense is becoming clear after discovery of innate immune receptors such as Toll-like receptor or Nod-like receptor. Innate immune system plays an important role in diverse pathological situations such as autoimmune diseases. Role of innate immunity in the pathogenesis of metabolic disorders such as type 2 diabetes, metabolic syndrome or atherosclerosis that has not been previously considered as inflammatory disorders, is also being appreciated. Here, the role of innate immunity in the development of type 1 diabetes, a classical organ-specific autoimmune disease, and type 2 diabetes will be discussed, focusing on the role of specific innate immune receptors involved in these disease processes. © 2014 The Korean Academy of Medical Sciences.

Sung K.-C.,Sungkyunkwan University | Wild S.H.,University of Edinburgh | Byrne C.D.,Endocrinology and Metabolism Unit
Journal of Hepatology | Year: 2014

Background & Aims Approximately 50% of hypertensive patients have non-alcoholic fatty liver disease (NAFLD), but whether change in fatty liver status over time modifies risk of developing hypertension is uncertain. Our aim was to determine whether a change in fatty liver status (either development of new fatty liver, or resolution of existing fatty liver) over five years modified risk of incident hypertension at five year follow-up. Methods 11,448 patients without hypertension were examined at baseline and at five year follow-up, using a retrospective cohort study design. Fatty liver status (absent or present) was assessed at baseline and follow-up using standard ultrasound criteria. Adjusted odds ratios (aOR) and 95% confidence intervals (CIs) for incident hypertension at follow-up were estimated controlling for potential confounders, compared to the reference group (patients who did not have fatty liver at either baseline or follow-up). Results 911 patients developed incident hypertension. Incident fatty liver developed during follow-up in 1418 patients and fatty liver at baseline resolved during follow-up in 684 patients. Developing incident fatty liver was associated with incident hypertension, even after adjustment for multiple confounders (aOR = 1.60 (95% CI 1.30, 1.96; p <0.001). Further adjustment for change in body mass index between baseline and follow-up only slightly attenuated this association (aOR = 1.36 (95% CI 1.10, 1.67; p = 0.004). With resolution of fatty liver at follow-up, risk of incident hypertension was not different from the reference group (aOR = 1.21 (95% CI 0.90, 1.63; p = 0.21). Conclusions Development of incident fatty liver is associated with increased risk of hypertension. © 2014 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.

Lim J.H.,Sungkyunkwan University
Korean Journal of Radiology | Year: 2011

Liver fluke disease is a chronic parasitic inflammatory disease of the bile ducts. Infection occurs through ingestion of fluke-infested, fresh-water raw fish. The most well-known species that cause human infection are Clonorchis sinensis, Opisthorchis viverrini and Opisthorchis felineus. Adult flukes settle in the small intrahepatic bile ducts and then they live there for 20-30 years. The long-lived flukes cause long-lasting chronic inflammation of the bile ducts and this produces epithelial hyperplasia, periductal fibrosis and bile duct dilatation. The vast majority of patients are asymptomatic, but the patients with heavy infection suffer from lassitude and nonspecific abdominal complaints. The complications are stone formation, recurrent pyogenic cholangitis and cholangiocarcinoma. Approximately 35 million people are infected with liver flukes throughout the world and the exceptionally high incidence of cholangiocarcinoma in some endemic areas is closely related with a high prevalence of liver fluke infection. Considering the impact of this food-borne malady on public health and the severe possible clinical consequences, liver fluke infection should not be forgotten or neglected.

Park N.-G.,Sungkyunkwan University
Materials Today | Year: 2015

Perovskite solar cells based on organometal halides represent an emerging photovoltaic technology. Perovskite solar cells stem from dye-sensitized solar cells. In a liquid-based dye-sensitized solar cell structure, the adsorption of methylammonium lead halide perovskite on a nanocrystalline TiO2 surface produces a photocurrent with a power conversion efficiency (PCE) of around 3-4%, as first discovered in 2009. The PCE was doubled after 2 years by optimizing the perovskite coating conditions. However, the liquid-based perovskite solar cell receives little attention because of its stability issues, including instant dissolution of the perovskite in a liquid electrolyte. A long-term, stable, and high efficiency (∼10%) perovskite solar cell was developed in 2012 by substituting the solid hole conductor with a liquid electrolyte. Efficiencies have quickly risen to 18% in just 2 years. Since PCE values over 20% are realistically anticipated with the use of cheap organometal halide perovskite materials, perovskite solar cells are a promising photovoltaic technology. In this review, the opto-electronic properties of perovskite materials and recent progresses in perovskite solar cells are described. In addition, comments on the issues to current and future challenges are mentioned. © 2014 Elsevier Ltd. All rights reserved.

Park Y.I.,Korea Basic Science Institute | Park Y.I.,Seoul National University | Lee K.T.,Gwangju Institute of Science and Technology | Suh Y.D.,Korea Research Institute of Chemical Technology | And 3 more authors.
Chemical Society Reviews | Year: 2015

Lanthanide-doped upconverting nanoparticles (UCNPs) have recently attracted enormous attention in the field of biological imaging owing to their unique optical properties: (1) efficient upconversion photoluminescence, which is intense enough to be detected at the single-particle level with a (nonscanning) wide-field microscope setup equipped with a continuous wave (CW) near-infrared (NIR) laser (980 nm), and (2) resistance to photoblinking and photobleaching. Moreover, the use of NIR excitation minimizes adverse photoinduced effects such as cellular photodamage and the autofluorescence background. Finally, the cytotoxicity of UCNPs is much lower than that of other nanoparticle systems. All these advantages can be exploited simultaneously without any conflicts, which enables the establishment of a novel UCNP-based platform for wide-field two-photon microscopy. UCNPs are also useful for multimodal in vivo imaging because simple variations in the composition of the lattice atoms and dopant ions integrated into the particles can be easily implemented, yielding various distinct biomedical activities relevant to magnetic resonance imaging (MRI), computed tomography (CT), and positron emission tomography (PET). These multiple functions embedded in a single type of UCNPs play a crucial role in precise disease diagnosis. The application of UCNPs is extended to therapeutic fields such as photodynamic and photothermal cancer therapies through advanced surface conjugation schemes. This journal is © The Royal Society of Chemistry.

Chung J.-W.,Sungkyunkwan University
Stroke | Year: 2016

BACKGROUND AND PURPOSE—: The association between family history of stroke and stroke recurrence remains unclear. METHODS—: Using a web-based multicenter stroke registry database, information on history of stroke in first-degree relatives was collected prospectively for acute ischemic stroke patients who were hospitalized within 7 days of onset. The collected information was categorized as follows: type of the affected relative(s) with stroke (paternal, maternal, sibling, or 2 or more) and age of the relative’s stroke onset (<50, 50–59, 60–69, and ≥70 years). Stroke recurrence was captured prospectively using a predetermined protocol. Subgroup analyses were performed according to the patient’s age at the index stroke. RESULTS—: Among 7642 patients, 937 (12.3%) had a history of stroke in their first-degree relatives and 475 (6.2%: 201 within and 274 after 3 weeks from index stroke) experienced stroke recurrence (median follow-up, 365 days). In multivariable Cox proportional hazard models, overall family history was not associated with stroke recurrence (hazard ratio, 1.08; 95% confidence interval, 0.81–1.43). However, the details of their family histories, including relative’s age at stroke onset (<50 years: hazard ratio, 2.14; 95% confidence interval, 1.004–4.54) and stroke history in a sibling (hazard ratio, 1.67; 95% confidence interval, 1.09–2.58), were independently associated with stroke recurrence after adjusting for potential confounders. The associations appeared to be stronger in young adults with stroke (age, <55 years) than in older stroke patients. CONCLUSIONS—: This study suggests that elevated risks of recurrent stroke are associated with having relatives with early-onset stroke and siblings with stroke histories, implying that additional precautions may be needed in such populations. © 2016 American Heart Association, Inc.

Shin D.,Sungkyunkwan University
Telematics and Informatics | Year: 2014

With a value-sensitive approach in mind, a theoretical and empirical analysis was conducted and reported here to explain the factors that influence potential user adoption of cloud computing by integrating quality factors as well as cognitive motivations as primary determining factors. The factors are explored as human values and the methodology how designers should take these values into account is examined. The results show that user intentions and behaviors are largely influenced by the perceived values of cloud services, which include availability, access, security and reliability. These values were found to be the significant antecedents of usefulness and ease of use in cloud computing. Theoretically, the model proposed in this paper advances the existing technology acceptance models and can be used to predict the acceptance and diffusion of cloud computing. Practically, the findings should guide the government and industry promoting cloud services to increase user acceptance by enhancing user experience and ensuring security. © 2014 Elsevier Ltd.

Background: Serum gamma-glutamyltransferase (GGT) has been suggested as a predictor for development of the metabolic syndrome in non-Korean population, but studies in Korean population are scarce. Therefore, we examined the association between serum GGT levels and the incidence of the metabolic syndrome in Korean male offi ce workers. Methods: The study population consisted of 32,692 office workers who underwent health checkups in both 2005 and 2009. A total of 17,583 with elevated GGT levels, the presence of metabolic syndrome, medication history at baseline, and female offi ce workers were excluded. Finally, 15,109 subjects were included in the fi nal analysis. We measured serum GGT levels and individual metabolic components. Results: As a quartile of serum GGT increased, 4-year follow-up incidence of the metabolic syndrome increased. After adjustment for age, alcohol drinking status and smoking status in 2005, logistic regression analysis showed that the odds ratios (95% confi dence interval) for incident metabolic syndrome in 2009 compared to the lowest quartile and upper quartiles were 1.00 (reference), 1.57 (1.24-2.00), 2.73 (2.17-3.43), 3.78 (3.02-4.74), and statistically signifi cant (P < 0.001), respectively. Conclusion: These results showed that the higher serum GGT predicted the future development of metabolic syndrome. In Korean male offi ce workers without the metabolic syndrome, the serum GGT levels despite normal levels were associated with an increased risk of incident metabolic syndrome. © 2012 The Korean Academy of Family Medicine.

Jung Y.M.,Yonsei University | Yun S.,Sungkyunkwan University
IEEE Transactions on Medical Imaging | Year: 2015

EIT problem is a typical inverse problem with serious ill-posedness. In general, regularization techniques are necessary for such ill-posed inverse problems. To overcome ill-posedness, the total variation (TV) regularization is widely used and it is also successfully applied to EIT. For realtime monitoring, a fast and robust image reconstruction algorithm is required. By exploiting recent advances in optimization, we propose a first-order TV algorithm for EIT, which simply consists of matrix-vector multiplications and in which the sparse structure of the system can be easily exploited. Furthermore, a typical smoothing parameter to overcome nondifferentibility of the TV term is not needed and a closed form solution can be applied in part using soft thresholding. It shows a fast reconstruction in the beginning. Numerical experiments using simulated data and real experimental data support our claim. © 2014 IEEE.

Jung S.M.,Sungkyunkwan University
Nature communications | Year: 2013

Transforming growth factor (TGF)-β, a pivotal cytokine involved in a variety of cellular functions, transmits signals through Smad-dependent canonical and Smad-independent noncanonical pathways. In contrast to the canonical TGF-β pathway, it is unknown how noncanonical TGF-β pathways are negatively regulated. Here we demonstrate that the inhibitory Smad Smad6, but not Smad7, negatively regulates TGF-β1-induced activation of the TRAF6-TAK1-p38 MAPK/JNK pathway, a noncanonical TGF-β pathway. TGF-β1-induced Smad6 abolishes K63-linked polyubiquitination of TRAF6 by recruiting the A20 deubiquitinating enzyme in AML-12 mouse liver cells and primary hepatocytes. In addition, the knockdown of Smad6 or A20 in an animal model or cell culture system maintains TAK1 and p38 MAPK/JNK phosphorylation and increases apoptosis, emphasizing the crucial role of the Smad6-A20 axis in negative regulation of the TGF-β1-TRAF6-TAK1-p38 MAPK/JNK pathway. Therefore, our findings provide insight into the molecular mechanisms underlying negative regulation of noncanonical TGF-β pathways.

BACKGROUND: It is generally stated that oral antiviral therapy in patients with chronic hepatitis B (CHB) decreases the risk of developing hepatocellular carcinoma (HCC). Although oral nucleos(t)ide analogues (NUCs) may induce a state similar to inactive stage CHB, the long-term risk for HCC in patients treated with NUCs compared with inactive CHB is unclear.METHODS: A total of 1378 patients who were treatment naïve and started NUC therapy and 1014 patients with inactive stage CHB who were HBeAg-negative and continuously had hepatitis B DNA <2000 IU/mL during follow-up were enrolled. The NUC group was divided into two groups by continuous viral suppression: NUC complete responder (CR) group and NUC incomplete responder (IR) group. Cumulative HCC incidence rates were compared between the groups.RESULTS: The risk of developing HCC was significantly higher in the NUC CR group compared with the inactive CHB group, regardless of the presence of baseline liver cirrhosis (p<0.001). Risk factors associated with the development of HCC were treatment groups (p<0.001), age (p<0.001), sex (p<0.001) and the presence of liver cirrhosis at baseline (p=0.005). Of the NUC group, the cumulative incidence of HCC in the NUC IR group was significantly higher compared with the NUC CR group (p=0.028).CONCLUSIONS: The use of potent oral antiviral therapy can effectively suppress HBV replication in patients with CHB. However, the risk of HCC development in patients treated with oral antiviral agent is still significantly higher than patients with inactive stage CHB. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Kim W.-S.,Sungkyunkwan University
Journal of Cosmetic and Laser Therapy | Year: 2013

Background: Facial skin pigmentary disorders can be resistant to conventional treatment. Superficial chemical peel is an effective and safe treatment in pigmentary problems including melasma, post-inflammatory hyperpigmentation and aging spots. Objective: To assess the efficacy and safety of new superficial chemical peel (Melasma peel, Theraderm®), this is composed of alpha-hydroxy acid (AHAs), vitamin C and oxygen for melasma. Methods: Twenty-five ethnic Korean patients (Fitzpatrick skin phototypes IV and V) with moderate to severe melasma were enrolled. The patients underwent four treatments at 1-2-week intervals for 8 weeks. Clinical improvement was evaluated on a 5-point scale by participants and by the same dermatologist, and adverse effects were checked during the study. Results: Improvement in the degree of pigmentation, pores, and evenness were noted. Significant clinical improvement of hyperpigmentation was evident. No adverse effects were reported. Conclusion: New superficial chemical peel using AHAs, vitamin C and oxygen is an effective and very safe treatment for melasma. © 2013 Informa UK, Ltd.

Yoon J.-H.,Sungkyunkwan University | Lee S.-Y.,Korea Research Institute of Bioscience and Biotechnology
Antonie van Leeuwenhoek, International Journal of General and Molecular Microbiology | Year: 2012

A novel bacterial strain, designated T-Y1 T, capable of degrading a variety of polysaccharides was isolated from seawater of an oyster farm in the South Sea, Korea. It was found to be aerobic, Gram-negative, non-flagellated, non-gliding and rodshaped. Strain T-Y1 T grew optimally at 25 °C, at pH 7.0-7.5 and in the presence of 2 % (w/v) NaCl. A neighbour-joining phylogenetic tree based on 16S rRNA gene sequences showed that strain T-Y1 T belonged to the genus Winogradskyella. Strain T-Y1 T exhibited 16S rRNA gene sequence similarity values of 95.0-96.8 % to the type strains of recognized Winogradskyella species and less than 94.5 %to other validly named species. The chemotaxonomic data concurred with the phylogenetic inference. Strain T-Y1 T contained MK-6 as the predominant menaquinone and anteiso-C 15:0, iso-C 15:0, iso-C 15:1 G and iso-C 16:0 3-OH as the major fatty acids. The major polar lipids of strain T-Y1 T were phosphatidylethanolamine and two unidentified lipids. The DNA G?C content was 36.2 mol%. Differential phenotypic properties, together with its phylogenetic distinctiveness, enabled strain T-Y1 T to be differentiated from the recognized Winogradskyella species. On the basis of the data presented here, strain T-Y1 T is considered to represent a novel species of the genus Winogradskyella, for which the name Winogradskyella multivorans sp. nov. is proposed. The type strain is T-Y1 T (=KCTC 23891T = CCUG 62216 T). © Springer Science+Business Media B.V. 2012.

Shin D.-H.,Sungkyunkwan University
International Journal of Mobile Communications | Year: 2014

The goal of this study was to propose a customer satisfaction index (CSI) model for smartphones and to measure the CSI to derive practical implications for providers and offer suggestions related to the improvement of service. Using user experience data, the CSI model and its hypotheses were tested through structural equation model analysis and index calculation. The findings indicate that perceived value and customer satisfaction are two significant variables that mediate the relationship between quality and customer loyalty. The proposed model has strong explanatory power with satisfactory reliability and validity. The results of the study provide heuristic information for the smart industry and policy-makers in forging effective policies and competitive strategies for smartphone services. The smartphone CSI model also establishes the foundation of a powerful tool for quality assessment of future smart service categories. Copyright © 2014 Inderscience Enterprises Ltd.

To evaluate the effects of various factors on the variability of retinal nerve fiber layer (RNFL) thickness measurements using the Stratus optical coherence tomography (OCT) in normal and glaucomatous eyes. Four hundred seventy-four subjects (103 normal eyes and 371 glaucomatous eyes) were scanned to determine the RNFL thickness measurements using the Stratus OCT. Measurements were obtained twice during the same day. The standard deviation (SD) was used to compare the variability in RNFL thickness measurements of the normal subjects to that of the glaucomatous patients. Multivariate regression analysis was used to evaluate which covariates were independent predictors of SD in overall mean RNFL thickness. The mean SD of all RNFL thickness measurements was larger in the glaucoma group except in one sector. In the multivariate regression analysis, the average signal strength (SS) and the relative SS change (difference in SS between initial and repeat scans, divided by initial SS) were independent predictors of the SD in the RNFL thickness measurements (partial R(2) = 0.018, 0.013; p = 0.016, 0.040, respectively). Glaucomatous eyes tend to be more variable than normal eyes in RNFL thickness measurement using the Straus OCT. The average SS and the relative SS changes appear to correlate with the variability in RNFL thickness measurement. Therefore, the results of the RNFL analysis should not be interpreted independently of these factors.

Yoon J.-H.,Sungkyunkwan University | Kang S.-J.,Korea Research Institute of Bioscience and Biotechnology | Lee S.-Y.,Korea Research Institute of Bioscience and Biotechnology
Antonie van Leeuwenhoek, International Journal of General and Molecular Microbiology | Year: 2012

A Gram-negative, non-motile, non-endospore-forming bacterial strain, designated DPSR-4 T, was isolated from a tidal flat sediment on the southern coast of Korea. Strain DPSR-4 T grew optimally at 25-30°C, at pH 7.0-7.5 and in the presence of 2% (w/v) NaCl. A Neighbour-Joining phylogenetic tree based on 16S rRNA gene sequences revealed that strain DPSR-4 T clustered with Salinimonas chungwhensis BH030046 T by a high bootstrap resampling value of 99.7%. Strain DPSR-4 T exhibited 96.2% 16S rRNA gene sequence similarity to that of S. chungwhensis BH030046 T and 93.7-96.6% sequence similarity to the sequences of type strains of Alteromonas species. Strain DPSR-4 T contained Q-8 as the predominant ubiquinone and iso-C 15:0 2-OH and/or C 16:1 ω7c, C 16:0 and C 18:1 ω7c as the major fatty acids. The major polar lipids detected in strain DPSR-4 T and S. chungwhensis KCTC 12239 T were phosphatidylglycerol, phosphatidylethanolamine and an unidentified phospholipid. The DNA G+C content was 53.4 mol%. Differential phenotypic properties and phylogenetic distinctiveness of strain DPSR-4 T demonstrated that this strain is distinguishable from the sole recognized species of the genus Salinimonas, S. chungwhensis. On the basis of phenotypic, chemotaxonomic and phylogenetic data, strain DPSR-4 T is considered to represent a novel species of the genus Salinimonas, for which the name Salinimonas lutimaris sp. nov. is proposed. The type strain is DPSR-4 T (KCTC 23464 T, CCUG 60743 T). © Springer Science+Business Media B.V. 2011.

Lee D.Y.,Sungkyunkwan University | Lehto M.R.,Purdue University
Computers and Education | Year: 2013

The present study was framed using the Technology Acceptance Model (TAM) to identify determinants affecting behavioral intention to use YouTube. Most importantly, this research emphasizes the motives for using YouTube, which is notable given its extrinsic task goal of being used for procedural learning tasks. Our conceptual framework included two proximal antecedents of behavioral intention as proposed by the TAM - perceived usefulness and perceived ease of use. Additionally, the four first-order constructs of user satisfaction, content richness, vividness, and YouTube self-efficacy, as well as one second-order construct of content richness, were additionally incorporated into the framework by elaborating the theoretical structure. Sample data was collected from 432 respondents who were given the opportunity to engage in procedural learning through YouTube in a lab setting. The results derived from fitting the structural equation model on the sample indicated that behavioral intention was significantly influenced by both perceived usefulness and user satisfaction. Moreover, task-technology fit, content richness, vividness, and YouTube self-efficacy emerged as significant predictors of perceived usefulness. However, perceived ease of use was not significantly predictive of either perceived usefulness or behavioral intention. Our proposed model explained 43.8% of the variance in behavioral intention. Overall findings suggest that YouTube may augment its function as a common channel for procedural learning and instruction. © 2012 Elsevier Ltd. All rights reserved.

The integration of photovoltaic (PV) generators in the envelope of a building by means of building-integrated photovoltaics (BIPV) offers an immense potential, both in market development and the production of renewable electric energy that is close to the point of electricity consumption. In Germany, for example, by integrating photovoltaics in buildings up to 50% of the electricity demand can be covered. The political support of BIPV would contribute to the development and installation of BIPV components and therefore also promote the development of new business areas for industries dealing with components used in building envelopes and photovoltaic generators. BIPV can be separated into three different integration types: "technical", "formal" and "technical & formal". Political instruments for the support of PV-installations, particularly BIPV are discussed in this paper using Germany and France as examples. Due to successful financial support policies, PV became the most powerful electricity production technology in Germany. In France, the unique financial support of BIPV is resulting in an exemplary development and growth of certified BIPV components available on the market and, from a technical, aesthetic architectural and legal certainty point of view, facilitating the easy and widespread integration of photovoltaic generators in buildings. © 2013 by the authors.

Li Y.,Northwestern University | Kroger M.,ETH Zurich | Liu W.K.,Northwestern University | Liu W.K.,Sungkyunkwan University
Physical Review Letters | Year: 2012

We explore the dynamics of entangled polymer chains embedded into nanocomposites. From primitive path analysis, highly entangled polymer chains are found to be significantly disentangled during increment of the volume fraction of spherical nonattractive nanoparticles (NPs) from 0 to 42%. A critical volume fraction, =31%, is found to control the crossover from polymer chain entanglements to "NP entanglements." While below , the polymer chain relaxation accelerates upon filling, above , the situation reverses: polymer dynamics becomes geometrically constrained upon adding NPs. Our findings provide a microscopic understanding of the dynamics of entangled polymer chains inside their composites, and offer an explanation for the unusual rheological properties of polymer composites. © 2012 American Physical Society.

Truong P.L.,Sungkyunkwan University | Ma X.,Korea University | Sim S.J.,Korea University
Nanoscale | Year: 2014

Scientific interest in nanotechnology is driven by the unique and novel properties of nanometer-sized metallic materials such as the strong interaction between the conductive electrons of the nanoparticles and the incident light, caused by localized surface plasmon resonances (LSPRs). In this article, we analysed the relationship of the Rayleigh scattering properties of a single Au nanoparticle with its size, shape, and local dielectric environment. We also provided a detailed study on the refractive index sensitivity of three types of differently shaped Au nanoparticles, which were nanospheres, oval-shaped nanoparticles and nanorods. This study helps one to differentiate the Rayleigh light scattering from individual nanoparticles of different sizes and/or shapes and precisely obtain quantitative data as well as the correlated optical spectra of single gold nanoparticles from the inherently inhomogeneous solution of nanoparticles. These results suggest that the shape, size and aspect ratio of Au nanoparticles are important structural factors in determining the resonant Rayleigh light scattering properties of a single Au nanoparticle such as its spectral peak position, scattering-cross-section and refractive index sensitivity, which gives a handle for the choice of gold nanoparticles for the design and fabrication of single nanosensors. © 2014 The Royal Society of Chemistry.

Kee C.,Sungkyunkwan University
American Journal of Ophthalmology | Year: 2015

Purpose To compare the lamina cribrosa thickness, measured by swept-source optical coherence tomography (SS OCT), between each eye of normal tension glaucoma (NTG) patients with unilateral visual field (VF) defect and to investigate the correlation between lamina cribrosa thickness and VF loss. Design Prospective, cross-sectional study. Methods Optic nerve heads were scanned using SS OCT, and laminar thickness was measured on mid-superior, central, and mid-inferior regions of vertical midline of the optic disc. The inter-eye differences of lamina cribrosa thickness in NTG patients with unilateral VF defect and the intra-eye difference of lamina cribrosa thickness in VF-affected eyes were analyzed using the paired t test. We evaluated the correlation between lamina cribrosa thickness and mean deviation, measured using standard automated perimetry, in NTG patients. Results This study included 102 eyes in 51 NTG patients with unilateral VF defect and 47 eyes in 47 normal subjects without glaucomatous change in either eye. The mean lamina cribrosa thickness of normal fellow eyes was thicker than VF-affected eyes in NTG patients (P <.001), but thinner than normal subject eyes (P <.001). Within VF-affected eyes, lamina cribrosa thickness of regions correlated with visual field defect was thinner than horizontally contralateral locations (P <.001). The mean deviation was statistically correlated with inter-eye difference of lamina cribrosa thickness in NTG patients (n = 51; r2 = 0.12; P =.01). Conclusions The lamina cribrosa was thinner in VF-unaffected eyes of NTG patients than in normal subject eyes, in VF-affected eyes than in normal fellow eyes of NTG patients, and in regions correlated with visual field loss than in horizontally contralateral ones in VF-affected eyes. © 2015 Elsevier Inc.

Jeon B.S.,Sungkyunkwan University
Fibers and Polymers | Year: 2012

Peirce's fabric model has been widely used to predict the structural behavior of various plain woven fabrics. The structure of plain woven fabric can be defined in terms of the warp yarn number, weft yarn number, warp fabric density, weft fabric density, warp crimp, and weft crimp. The warp and weft yarn diameters are calculated from the warp and weft yarn numbers, and the effective coefficient of the yarn diameter is defined by using this model. We have investigated structural properties, such as the effective coefficient of the yarn diameter, yarn crimp, and fabric thickness for two different fabrics in which the constituent yarns are assumed to be either incompressible or compressible. This model is also applied to various plain fabrics woven from cotton, rayon, wool, linen, nylon, acetate, polyester, and silk yarns. © 2012 The Korean Fiber Society and Springer Netherlands.

Koo M.,Sungkyunkwan University | Fishbach A.,University of Chicago
Journal of Personality and Social Psychology | Year: 2010

Pursuing a series of progressive (e.g., professional) goals that form a goal ladder often leads to a trade-off between moving up to a more advanced level and repeating the same goal level. This article investigates how monitoring one's current goal in terms of remaining actions versus completed actions influences the desire to move up the goal ladder. The authors propose that a focus on remaining (vs. completed) actions increases the motivation to move up to a more advanced level, whereas the focus on completed (vs. remaining) actions increases the satisfaction derived from the present level. They find support for these predictions across several goal ladders, ranging from academic and professional ladders to simple, experimental tasks. They further find that individuals strategically attend to information about remaining (vs. completed) actions to prepare to move up the goal ladder. © 2010 American Psychological Association.

Lee S.-I.,Sungkyunkwan University
Allergy, Asthma and Immunology Research | Year: 2010

Childhood asthma is a major concern because it leads to more hospital visits and a heavy economic burden. Proper management and prevention strategies for childhood asthma must be based on correct evaluation of prevalence and risk factors for its development. In Korea, nationwide studies were conducted in 1995 and 2000 on students from 68 elementary schools (age, 6-12 years) and junior high schools (age, 12-15 years) by the Korean Academy of Pediatric Allergy and Respiratory Diseases. We used the Korean version of the International Study of Asthma and Allergies in Childhood (ISAAC) written and video questionnaires at the same schools during the same period (October-November). The prevalence of asthma in junior high school children seemed to increase over 5 years. However, in elementary school children, the prevalence of asthma symptoms decreased, although the prevalence of 'diagnosis of asthma, ever' and 'treatment of asthma, last 12 months' increased. In addition, it was found that various factors, such as obesity, passive smoking, dietary habits, raising pets at home, and fever/antibiotic use during infancy were associated with childhood asthma. When prevalence of asthma in Korea was compared with that in different regions, the prevalence changes in the 6-7 years age group did not seem to be consistent between regions, whereas similar trends were observed among children aged 13-14 years. To conduct another epidemiological study to evaluate the time trend over time, a third nationwide survey is planned in 2010, and we anticipate ISAAC Phase 3 will explore recent changes in the prevalence of childhood asthma and assess its risk factors in Korean children. On the basis of accurate data on the current status of childhood asthma in 2010, we will be able to establish proper management strategies. © Copyright The Korean Academy of Asthma, Allergy and Clinical Immunology • The Korean Academy of Pediatric Allergy and Respiratory Disease.

Kim C.H.,Chonnam National University | Huh J.W.,Sungkyunkwan University | Kim H.R.,Chonnam National University | Kim Y.J.,Chonnam National University
Annals of Surgery | Year: 2015

Background: Chest computed tomographic (CT) scans frequently detect indeterminate pulmonary nodules (IPNs) in patients with colorectal cancer. The discovery of such nodules creates a clinical dilemma. Purpose: This study was performed to identify clinical characteristics of IPNs and develop a predictive model to predict the risk of progression to pulmonary metastases in patients with colorectal cancer. Methods: We analyzed data from a prospectively collected database involving 1195 patients with colorectal carcinoma who underwent curative surgery between January 2008 and June 2010. A predictive model was constructed on the basis of the probability risk score and validated in 115 patients collected from a separate treatment period. Results: Of the 1195 patients who underwent a baseline staging chest computed tomography, 326 (27.2%) had IPNs. During a median follow-up of 26.7 months (interquartile range: 18.0-37.2), 74 (28.1%) showed pulmonary metastases. Five variables maintained prognostic significance after multivariate analysis: metachronous nodule, bilateral involvement, positive perineural invasion, increased number of positive lymph nodes, and rectal location of cancer. The 2-year progression-free survival rates for the very low-, low-, intermediate-, and high-risk groups were 96%, 82%, 46%, and 16%, respectively (P < 0.001), with a concordance index of 0.81 (95% confidence interval, 0.75-0.86). This model was validated in a separate patient set (P < 0.001), with a C-index of 0.83 (95% confidence interval, 0.77-0.88). Conclusions: A predictive model for progression of IPNs may be clinically useful in discriminating patientswhomight benefit from an aggressive surveillance program and early pulmonary metastasectomies. Copyright © 2014 Wolters Kluwer Health, Inc. All rights reserved.

Qiu H.,Bigelow Laboratory for Ocean Sciences | Yang E.C.,Bigelow Laboratory for Ocean Sciences | Bhattacharya D.,Rutgers University | Yoon H.S.,Sungkyunkwan University
Molecular Biology and Evolution | Year: 2012

Because of its ancient origin more than 1 billion years ago, the highly reduced plastid genomes of Plantae (e.g., plant chloroplasts) provide limited insights into the initial stages of endosymbiont genome reduction. The photosynthetic amoeba Paulinella provides a more useful model to study this process because its alpha-cyanobacterium-derived plastid originated ∼60 Ma and the genome still contains ∼1,000 genes. Here, we compared and contrasted features associated with genome reduction due to primary endosymbiosis in Paulinella plastids and in marine, free-living strains of the picocyanobacterium, Prochlorococcus. Both types of genomes show gene inactivation, concerted evolution, and contraction of gene families that impact highly conserved single-copy phylogenetic markers in the plastid such as psbA, psbC, and psbD. Our data suggest that these photosystem II genes may provide misleading phylogenetic signal because each of the constituent Plantae lineages has likely undergone a different, independent series of events that led to their reduction to a single copy. This issue is most problematic for resolving basal Plantae relationships when differential plastid gene loss was presumably ongoing, as we observe in Paulinella species. Our work uncovers a key, previously unappreciated aspect of organelle genome reduction and demonstrates "work-in-progress" models such as Paulinella to be critical to gain a fuller understanding of algal and plant genome evolution. © 2012 The Author.

Sim W.S.,Sungkyunkwan University
Korean Journal of Pain | Year: 2011

botulinum toxin has been used for the treatment of many clinical disorders by producing temporary skeletal muscle relaxation. In pain management, botulinum toxin has demonstrated an analgesic effect by reducing muscular hyperactivity, but recent studies suggest this neurotoxin could have direct analgesic mechanisms different from its neuromuscular actions. At the moment, botulinum toxin is widely investigated and used in many painful diseases such as myofascial syndrome, headaches, arthritis, and neuropathic pain. Further studies are needed to understand the exact analgesic mechanisms, efficacy and complications of botulinum toxin in chronic pain disorders. © 2011 The Korean Pain Society.

Living donor liver transplantation (LDLT) has become an accepted therapeutic option for patients with end-stage liver disease. However, biliary complications remain the major causes of morbidity and mortality for LDLT recipients. Although there are currently no reports of a clear therapeutic algorithm, many approaches have been developed to treat biliary complications, including surgical, endoscopic, and percutaneous transhepatic techniques. Endoscopic treatment is currently the preferred initial treatment for patients that have previously undergone duct-to-duct biliary reconstruction. This article discusses aspects of endoscopic management of biliary complications that occur in adult LDLT.

Lee J.,Sungkyunkwan University | Ou S.-H.I.,University of California at Irvine
Discovery Medicine | Year: 2013

Gastric cancer is the second leading cancer cause of death globally. Apart from the successful targeting of HER2 over-expression in gastric cancer (GC) with trastuzumab, other targeted therapies in GC have fallen short or still in early clinical development. While HER2 over-expression accounts for up to 20% of GC, other potential actionable driver mutations occur a much lower frequency in GC. In this review we describe some of the more interesting genetic aberrations including driver mutations in gastric cancer that have very potent inhibitors against them already in clinical development. Part I of this review will focus on the receptor tyrosine kinase (RTK) gene amplification (HER2, FGFR2, MET, EGFR). Part II will devoted to gene mutations (HER2, KRAS, PIK3CA, BRAF) and gene rearrangement (ROS1, BRAF, HER2). Because of the low frequency of these potential driver mutations, perseverance in screening for these mutations will be needed in order to enroll enough of each uniquely molecularly defined subset of GC in order to demonstrate significant clinical benefit in a unique molecularly targeted therapy trial. This approach has been successfully employed in the clinical approval of crizotinib for the treatment of ALK-rearranged non-small cell lung cancer. © Discovery Medicine.

Akkarajitsakul K.,University of Manitoba | Hossain E.,University of Manitoba | Niyato D.,Nanyang Technological University | Kim D.I.,Sungkyunkwan University
IEEE Communications Surveys and Tutorials | Year: 2011

Multiple access methods in a wireless network allow multiple nodes to share a set of available channels for data transmission. The nodes can either compete or cooperate with each other to access the channel(s) so that either an individual or a group objective can be achieved. Game theory, which is a mathematical tool developed to understand the interaction among rational entities, can be applied to model and to analyze individual or group behaviour of nodes for multiple access in wireless networks. Game theory also enables us to model the selfish/malicious behaviour of nodes, and subsequently design the punishment or defense mechanisms for robust multiple access in wireless networks. In addition, game models can provide distributed solutions to the multiple access problems, which are based on solid theoretical foundations. In this survey, we provide a comprehensive review of the game models (e.g., noncooperative/cooperative, static/dynamic, and complete/incomplete information) developed for different multiple access schemes (i.e., contention-free and contention-based random channel access) in wireless networks. We consider time-division multiple access (TDMA), frequency-division multiple access (FDMA), and code-division multiple access (CDMA), ALOHA, and carrier sense multiple access (CSMA)-based wireless networks. In addition, game models for multiple access in dynamic spectrum access-based cognitive radio networks are reviewed. The major findings from the game models used for these different access schemes are highlighted. To this end, several of the key open research directions are outlined. © 2005 IEEE.

Choi Y.C.,Korea Research Institute of Chemical Technology | Lee D.U.,Hanyang University | Noh J.H.,Korea Research Institute of Chemical Technology | Kim E.K.,Hanyang University | And 2 more authors.
Advanced Functional Materials | Year: 2014

The light-harvesting Sb2S3 surface on mesoporous-TiO2 in inorganic-organic heterojunction solar cells is sulfurized with thioacetamide (TA). The photovoltaic performances are compared before and after TA treatment, and the state of the Sb2S3 is investigated by X-ray diffraction, X-ray photoelectron spectroscopy, and deep-level transient spectroscopy (DLTS). Although there are no differences in crystallinity and composition, the TA-treated solar cells exhibit significantly enhanced performance compared to pristine Sb2S3-sensitized solar cells. From DLTS analysis, the performance enhancement is mainly attributed to the extinction of trap sites, which are present at a density of (2-5) × 1014 cm-3 in Sb2S3, by TA treatment. Through such a simple treatment, the cell records an overall power conversion efficiency (PCE) of 7.5% through a metal mask under simulated illumination (AM 1.5G, 100 mW cm-2) with a very high open circuit voltage of 711.0 mV. This PCE is, thus far, the highest reported for fully solid-state chalcogenide-sensitized solar cells. The light-harvesting Sb 2S3 surface on mesoporous-TiO2 in inorganic-organic heterojunction solar cells is sulfurized with thioacetamide. Through such a simple treatment, the cell records an overall power conversion efficiency of 7.5% under simulated illumination (AM 1.5G, 100 mW cm -2) and the performance enhancement is mainly attributed to the extinction of trap sites by deep-level transient spectroscopy analysis. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Park K.,Sungkyunkwan University
Automatica | Year: 2015

A block decoupling problem in linear multivariable systems is treated for one-degree-of-freedom controller configuration with unity output feedback. The plant transfer matrix, which may be non-square, is assumed to have unstable simple poles and zeros that may coincide. A simple existence condition of a block decoupling controller is obtained by directional interpolation approaches. © 2014 Elsevier Ltd. All rights reserved.

Kim M.H.,Sungkyunkwan University
Investigative ophthalmology & visual science | Year: 2013

To estimate the heritabilities of myopia and ocular biometrics among different family types among a Korean population. We studied 1508 adults in the Healthy Twin Study. Spherical equivalent, axial length, anterior chamber depth, and corneal astigmatism were measured by refraction, corneal topography, and A-scan ultrasonography. To see the degree of resemblance among different types of family relationships, intraclass correlation coefficients (ICC) were calculated. Variance-component methods were applied to estimate the genetic contributions to eye phenotypes as heritability based on the maximum likelihood estimation. Narrow sense heritability was calculated as the proportion of the total phenotypic variance explained by additive genetic effects, and linear and nonlinear effects of age, sex, and interactions between age and sex were adjusted. A total of 240 monozygotic twin pairs, 45 dizygotic twin pairs, and 938 singleton adult family members who were first-degree relatives of twins in 345 families were included in the study. ICCs for spherical equivalent from monozygotic twins, pooled first-degree pairs, and spouse pairs were 0.83, 0.34, and 0.20, respectively. The ICCs of other ocular biometrics were also significantly higher in monozygotic twins compared with other relative pairs, with greater consistency and conformity. The estimated narrow sense heritability (95% confidence interval) was 0.78 (0.71-0.84) for spherical equivalent; 0.86 (0.82-0.90) for axial length; 0.83 (0.76-0.91) for anterior chamber depth; and 0.70 (0.63-0.77) for corneal astigmatism. The estimated heritability of spherical equivalent and ocular biometrics in the Korean population suggests the compelling evidence that all traits are highly heritable.

Jung H.S.,Seoul National University | Lee M.-S.,Sungkyunkwan University
Annals of the New York Academy of Sciences | Year: 2010

Type 2 diabetes mellitus is characterized by insulin resistance and failure of pancreatic β-cells producing insulin. Mitochondrial dysfunction may play a role in both processes of diabetes. Autophagy maintains cellular homeostasis through degradation and recycling of organelles such as mitochondria. As dysfunctional mitochondria are the main organelles removed by autophagy, we studied the role of autophagy in diabetes using mice with β-cell-specific deletion of the Atg7 gene. Atg7-mutant mice showed reduction in β-cell mass and pancreatic insulin content. Electron microscopy showed swollen mitochondria and other ultrastructural changes in autophagy-deficient β-cells. Insulin secretory function ex vivo was also impaired. As a result, Atg7-mutant mice showed hypoinsulinemia and hyperglycemia. These results suggest that autophagy is necessary to maintain structure, mass, and function of β-cells. Besides its effect on β-cells, autophagy may affect insulin sensitivity because mitochondrial dysfunction has been implicated in insulin resistance and autophagy is involved in the maintenance of the organelles. Furthermore, since aging is associated with impaired glucose tolerance, decline of autophagic activity may be involved in age-associated reduction of glucose tolerance. © 2010 New York Academy of Sciences.

Ryoo J.-H.,Kyung Hee University | Park S.K.,Sungkyunkwan University
Atherosclerosis | Year: 2013

Background and objective: There have been reports for the association between elevated serum apolipoprotein B (ApoB) and several cardiometabolic disorders. However, it remains unclear whether serum ApoB level predicts the development of metabolic syndrome (MetS). Accordingly, we carried out a prospective study to evaluate the longitudinal effects of baseline serum ApoB levels on the development of MetS. Patients and methods: A cohort of 25,193 healthy Korean men without MetS had been followed up prospectively. Baseline serum ApoB levels were categorized to following quintiles (quintile 1-5: <76.4, 76.4-88.4, 88.4-99.5, 99.5-113.0, ≥113.0). We evaluated the differences in the incidence of MetS according to quintiles of serum ApoB levels. Cox proportional hazards models were used to calculate the adjusted hazard ratios (HRs) for MetS. Results: During follow-up, 5407 (21.5%) cases developed MetS between 2006 and 2010. Incidence of MetS increased according to quintiles of serum ApoB levels [quintile 1-5: 9.1%, 16.4%, 22.1%, 27.3%, 36.4%, respectively (P for trend <0.001)]. Even after adjusting for various covariates including non-HDL-cholesterol, the hazard ratios (95% CI) for MetS increased in proportion to the quintiles of serum ApoB levels, compared to quintile 1 [quintile 2-5: 1.64 (1.43-1.89), 1.98 (1.71-2.31), 2.32 (1.96-2.75) and 2.92 (2.37-3.60), respectively (P for trend <0.001)]. These associations were apparent still in the clinically relevant subgroup analyses. Conclusions: Serum ApoB levels predict MetS, independent of baseline confounding variables including non-HDL-cholesterol. © 2012 Elsevier Ireland Ltd.

Kim J.-W.,Korea Electronics Technology Institute | Jung S.-B.,Sungkyunkwan University
Metals and Materials International | Year: 2010

The failure behaviors of ball grid array (BGA) solder ball joints under the various loading speeds of the high-speed shear test were investigated both experimentally and with non-linear, 3-dimensional finite element modeling. Conventional Sn-37Pb and Pb-free, Sn-3.5Ag solder alloys were used to compare the failure behaviors. Far greater shear forces were measured by the high-speed shear test than by the low-speed shear test. The shear force further increased with increasing shear speed, mainly due to the high strain-rate sensitivity of the solder alloys. Brittle interfacial fractures were more easily achieved by the high-speed shear test in the Sn-3.5Ag solder joints, especially at higher shear speed. This result was discussed in terms of the relationship between the strain-rate of the solder alloy, the work-hardening effect, and the resulting stress concentration in the interfacial regions. However, no transition of the failure mode was observed in the high-speed shear test of the Sn-37Pb solder joints. © KIM and Springer.

Flacke T.,Korea Advanced Institute of Science and Technology | Kong K.,University of Kansas | Park S.C.,Sungkyunkwan University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2014

The discovery of a Higgs boson and precise measurements of its properties open a new window to test physics beyond the standard model. Models with Universal Extra Dimensions are not an exception. Kaluza-Klein excitations of the standard model particles contribute to the production and decay of the Higgs boson. In particular, parameters associated with third generation quarks are constrained by Higgs data, which are relatively insensitive to other searches often involving light quarks and leptons. We investigate implications of the 126 GeV Higgs in next-to-minimal Universal Extra Dimensions, and show that boundary terms and bulk masses allow a lower compactification scale as compared to in minimal Universal Extra Dimensions. © 2013 The Authors.

Hong J.-W.,Kyung Hee University | Park K.W.,Sungkyunkwan University
Experimental and Molecular Medicine | Year: 2010

Obesity is a leading risk factor for insulin resistance, hypertension, hyperlipidemia, and cardiovascular complications, collectively referred to as metabolic diseases. Given the prevalence of obesity and its associated medical problems, new strategies are required to prevent or treat obesity and obesity-related metabolic effects. Here we summarize contributors of obesity, and molecular mechanisms controlling adipogenesis from studies in mammalian systems. We also discuss the possibilities of using Drosophila as a genetic model system to advance our understanding of players in fat biology.

Social network services (SNS) focus on building online communities of people who share interests and/or activities, or who are interested in exploring the interests and activities of others. This study examines security, trust, and privacy concerns with regard to social networking Websites among consumers using both reliable scales and measures. It proposes an SNS acceptance model by integrating cognitive as well as affective attitudes as primary influencing factors, which are driven by underlying beliefs, perceived security, perceived privacy, trust, attitude, and intention. Results from a survey of SNS users validate that the proposed theoretical model explains and predicts user acceptance of SNS substantially well. The model shows excellent measurement properties and establishes perceived privacy and perceived security of SNS as distinct constructs. The finding also reveals that perceived security moderates the effect of perceived privacy on trust. Based on the results of this study, practical implications for marketing strategies in SNS markets and theoretical implications are recommended accordingly. © 2010 Elsevier B.V.

Miao W.,Seoul National University | Shim G.,Seoul National University | Lee S.,Korea University | Lee S.,Seoul National University | And 2 more authors.
Biomaterials | Year: 2013

Here, we report the safety, tumor accumulation and potential of polyethylene glycol-grafted graphene oxide (pGO) as a multimodal nanocarrier of photosensitizers and synergistic anticancer agents. First, both graphene oxide (GO) and pGO were synthesized, and their in vitro and in vivo toxicities were tested. When 80 mg/kg was injected intravenously into mice, there was 100% fatality in the GO-treated group, but 100% survival among mice treated with pGO nanosheets. Treatment of cells with a photosensitizer chlorin e6 (Ce6) in pGO nanophysisorplexes significantly enhanced cellular delivery compared to that seen with Ce6 alone. The combination and dose reduction indexes revealed that combining doxorubicin (Dox) with Ce6 with at a molar ratio of 1:2 provided the highest synergism. The Ce6- and Dox-loaded pGO nanophysisorplexes (Ce6/Dox/pGO) were 148.0 ± 18.0 nm in size. Molecular imaging of mice showed that Ce6/Dox/pGO could accumulate in tumor tissues over 3 days. Moreover, in SCC tumor-bearing mice, the photodynamic anticancer effects of Ce6/Dox/pGO were higher than those of Ce6/pGO or Dox/pGO. Moreover, tumor sections from illuminated mice treated with Ce6/Dox/pGO showed substantial disruption of tumor nuclei, whereas the other groups did not. Our results suggest that pGO nanosheets have superior in vivo safety relative to GO, and that it is possible to enhance the tumor tissue distribution and photodynamic anticancer effects of systemically administered Ce6 by forming multimodal nanophysisorplexes with pGO and synergistic anticancer chemotherapeutics such as Dox. © 2013 Elsevier Ltd.

Chung K.Y.,Sungkyunkwan University
Toxicological Research | Year: 2013

G protein-coupled receptors (GPCRs) are membrane receptors; approximately 40% of drugs on the market target GPCRs. A precise understanding of the activation mechanism of GPCRs would facilitate the development of more effective and less toxic drugs. Heterotrimeric G proteins are important molecular switches in GPCR-mediated signal transduction. An agonist-activated receptor interacts with specific sites on G proteins and promotes the release of GDP from the Gα subunit. Because of the important biological role of the GPCR-G protein coupling, conformational changes in the G protein upon receptor coupling have been of great interest. One of the most important questions was the interface between the GPCR and G proteins and the structural mechanism of GPCR-induced G protein activation. A number of biochemical and biophysical studies have been performed since the late 80s to address these questions; there was a significant breakthrough in 2011 when the crystal structure of a GPCR-G protein complex was solved. This review discusses the structural aspects of GPCR-G protein coupling by comparing the results of previous biochemical and biophysical studies to the GPCR-G protein crystal structure.

Kim W.,Gachon University | Jeong O.-R.,Gachon University | Lee S.-W.,Sungkyunkwan University
Information Systems | Year: 2010

Today hundreds of millions of Internet users are using thousands of social Web sites to stay connected with their friends, discover new "friends," and to share user-created contents, such as photos, videos, social bookmarks, and blogs. There are so many social Web sites, and their features are evolving rapidly. There is controversy about the benefits of these sites, and there are social issues these sites have given rise to. There are lots of press articles, Wikipedia articles, and blogs-in varying degrees of authoritativeness, clarity and accuracy-about some of the social Web sites, uses of the sites, and some social problems, and business challenges faced by the sites. In this paper, we attempt to organize the status, uses, and issues of social Web sites into a comprehensive framework for discussing, understanding, using, building, and forecasting the future of social Web sites. © 2009 Elsevier B.V. All rights reserved.

Shin D.-H.,Sungkyunkwan University
International Journal of Human-Computer Interaction | Year: 2010

The growing interest in mobile commerce and the high penetration rate of mobile communication service are expected to provide mobile operators with a new and great business opportunity, the mobile payment. This study proposes a research model that examines the factors that determine consumer acceptance of mobile payment system. To achieve this goal, it employed the technology acceptance model (TAM), adding the concepts of security, trust, social influence, and computer-efficacy from Unified Theory of Acceptance and Use of Technology. The model is examined through an empirical study using structural equation modeling techniques. Although the model confirms the classical role of TAM factors, the results also show that users' attitudes and intentions are influenced by perceived risk and trust. Significant support for the model was found in the data collected from a survey of potential mobile payment system users. Based on the findings, this study proposes a conceptual framework of adoption enablers, drivers, and barriers with propositions to guide future research in mobile payment. Implications to practice and means to overcome the barriers are suggested. © Taylor & Francis Group, LLC.

Shin D.-H.,Sungkyunkwan University
Online Information Review | Year: 2010

Purpose The purpose of this study is to investigate users' underlying motivations for engaging in social networking through online social networking services (SNS) compared with their behaviour. It seeks to examine the differences between USA, and Korean users. Design/methodology/approach The study surveyed SNS users in the USA and Korea to determine the key differences between the two countries. Survey questions, developed in English and Korean, were presented in each country to explore the influences of various factors from the modified Technology Acceptance Model on SNS user dimensions. The analytic design methods were based on structural equation modelling and applied to the data gathered. The TAM factors of SNS were analysed, focusing on the differences in motives between the two countries. Findings The results of the online survey of SNS users validated the proposed theoretical model's ability to explain and predict user acceptance of SNS very well. While the results illustrate the importance of both extrinsic and intrinsic motivation, the two countries showed different sets of motivations, providing useful implications for theory and practice. Practical implications Based on the results of the study, practical applications for marketing strategies in online SNS markets and theoretical applications for cross-national studies are recommended. Originality/value Despite the burgeoning interest in SNS, only a few studies have explored the acceptance of SNS in a cross-national manner, leading to a paucity of information on how different cultures influence acceptance of online services. © 2010 Emerald Group Publishing Limited. All rights reserved.

Bae K.,Sungkyunkwan University
Korean journal of ophthalmology : KJO | Year: 2012

To compare the histopathologic and morphologic findings of encapsulated blebs following Ahmed glaucoma valve implantation and primary standard trabeculectomy with mitomycin-C. We reviewed the records of patients with otherwise uncontrollable glaucoma who had undergone Ahmed glaucoma valve implantation or trabeculectomy with mitomycin-C. Five eyes that underwent Ahmed valve implantation and three eyes that underwent trabeculectomy needed surgical revision of the initial surgery due to encapsulated bleb development with total loss of function. The surgically removed encapsulated blebs were analyzed macroscopically and microscopically. Removal of the encapsulated bleb was performed at a mean follow-up time of 26.6 ± 19.4 weeks in the Ahmed valve implantation group and 12.0 ± 11.4 weeks in the trabeculectomy group. The fibrotic wall of the encapsulated blebs had an overall thickness of 2.48 ± 0.42 mm in the Ahmed valve implantation group and 1.62 ± 0.37 mm in the trabeculectomy group. Macroscopically, the coconut flesh-like smooth surface was split into two layers, and the wall of the capsule was thicker in the Ahmed valve implantation group than in the trabeculectomy group. Histopathologically, the fibrotic capsule was composed of an inner fibrodegenerative layer and an outer fibrovascular layer, and there were no histopathological differences between the two groups. The fibrotic capsule wall was thicker in the Ahmed valve group, but there were no differences in histological findings between the two groups.

Preclinical and clinical studies have shown that the application of CD105(+) mesenchymal stem cells (MSCs) is feasible and may lead to recovery after stroke. In addition, circulating microparticles are reportedly functional in various disease conditions. We tested the levels of circulating CD105(+) microparticles in patients with acute ischemic stroke. The expression of CD105 (a surface marker of MSCs) and CXCR4 (a CXC chemokine receptor for MSC homing) on circulating microparticles was evaluated by flow cytometry of samples from 111 patients and 50 healthy subjects. The percentage of apoptotic CD105 microparticles was determined based on annexin V (AV) expression. The relationship between serum levels of CD105(+)/AV(-) microparticles, stromal cells derived factor-1α (SDF-1α), and the extensiveness of cerebral infarcts was also evaluated. CD105(+)/AV(-) microparticles were higher in stroke patients than control subjects. Correlation analysis showed that the levels of CD105(+)/AV(-) microparticles increased as the baseline stroke severity increased. Multivariate testing showed that the initial severity of stroke was independently associated with circulating CD105(+)/AV(-) microparticles (OR, 1.103 for 1 point increase in the NIHSS score on admission; 95% CI, 1.032-1.178) after adjusting for other variables. The levels of CD105(+)/CXCR4(+)/AV(-) microparticles were also increased in patients with severe disability (r = 0.192, p = 0.046 for NIHSS score on admission), but were decreased with time after stroke onset (r = -0.204, p = 0.036). Risk factor profiles were not associated with the levels of circulating microparticles or SDF-1α. In conclusion, our data showed that stroke triggers the mobilization of MSC-derived microparticles, especially in patients with extensive ischemic stroke.

Shin D.-H.,Sungkyunkwan University
International Journal of Human-Computer Interaction | Year: 2010

Massive multiplayer online role-playing games (MMORPGs) have been popular for several years and have spawned a whole subculture. Although studies on online games have received more attention in the literature, MMORPGs have seldom been addressed. This study applies the theory of reasoned action and modifies the technology acceptance model to propose a research model. An empirical study was conducted to test this model. The goal of this study is to examine what perceived factors contribute to an online game user's behaviors. The results of this study indicate that users' attitudes and intentions are influenced by perceived security and perceived enjoyment. Subjective norm and flow are key behavioral antecedents to users' loyalty. © Taylor & Francis Group, LLC.

Cho E.,Hanyang University | Choi M.,Sungkyunkwan University
Journal of Hydrology | Year: 2014

An understanding soil moisture spatio-temporal variability is essential for hydrological and meteorological research. This work aims at evaluating the spatio-temporal variability of near surface soil moisture and assessing dominant meteorological factors that influence spatial variability over the Korean peninsula from May 1 to September 29, 2011. The results of Kolmogorov-Smirnov tests for goodness of fit showed that all applied distributions (normal, log-normal and generalized extreme value: GEV) were appropriate for the datasets and the GEV distribution described best spatial soil moisture patterns. The relationship between the standard deviation and coefficient of variation (CV) of soil moisture with mean soil moisture contents showed an upper convex shape and an exponentially negative pattern, respectively. Skewness exhibited a decreasing pattern with increasing mean soil moisture contents and kurtosis exhibited the U-shaped relationship. In this regional scale (99,720 km2), we found that precipitation indicated temporally stable features through an ANOVA test considering the meteorological (i.e. precipitation, insolation, air temperature, ground temperature and wind speed) and physical (i.e. soil texture, elevation, topography, and land use) factors. Spatial variability of soil moisture affected by the meteorological forcing is shown as result of the relationship between the meteorological factors (precipitation, insolation, air temperature and ground temperature) and the standard deviation of relative difference of soil moisture contents (SDRDt ) which implied the spatial variability of soil moisture. The SDRDt showed a positive relationship with the daily mean precipitation, while a negative relationship with insolation, air temperature and ground temperature. The variation of spatial soil moisture pattern is more sensitive to change in ground temperature rather than air temperature changes. Therefore, spatial variability of soil moisture is greatly affected by meteorological factors and each of the meteorological factors has certain duration of effect on soil moisture spatial variability in regional scale. The results provide an insight into the soil moisture spatio-temporal patterns affected by meteorological and physical factors simultaneously, as well as the design criteria of regional soil moisture monitoring network at regional scale. © 2014 Elsevier B.V. All rights reserved.

Kim S.J.,Sungkyunkwan University | Won J.H.,Soonchunhyang University
Leukemia and Lymphoma | Year: 2012

Chronic graft-versus-host disease (GVHD) is a serious complication that develops frequently in survivors of allogeneic stem cell transplant. Since elucidation of the role of B cells in the pathogenesis of chronic GVHD, B cell-depleting therapy with rituximab has been associated with beneficial effects in clinical and laboratory studies in patients with chronic GVHD. Although the mechanism underlying the contribution of B cells to the development of chronic GVHD is poorly understood, recent studies have proposed that B cell reconstitution after allogeneic stem cell transplant is involved in the development of chronic GVHD. Inadequate reconstitution of naive B cells and the persistence of high levels of B cell-activating factor have been found in patients with chronic GVHD, and these changes might be associated with the expansion of activated CD27-positive B cells that produce autoantibody in chronic GVHD. In the light of this altered B cell homeostasis in chronic GVHD, the role of rituximab in controlling the clinical manifestations of chronic GVHD has been studied. In this review, we address the role of B cells in the pathogenesis of chronic GVHD and the response to B cell-depleting therapy based on B cell homeostasis. © 2011 Informa UK, Ltd.

Lee J.H.,National Police Hospital | Lee S.W.,Sungkyunkwan University
Journal of Sexual Medicine | Year: 2015

Introduction: Chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) is a common etiology of premature ejaculation (PE). However, the current data are insufficient to explain this relationship and to support routine screening of men with PE. Aims: This study aims to evaluate the relationship between PE and CP/CPPS. Methods: A cross-sectional study was conducted that included 8,261 men who had participated in a health examination. The Premature Ejaculation Diagnostic Tool (PEDT), the National Institutes of Health-Chronic Prostatitis Symptom Index (NIH-CPSI), and the International Index of Erectile Function-5 (IIEF) were used for assessment of symptoms. A full metabolic work-up and serum testosterone level checks were also performed. We then investigated the relationship using the Spearman correlation test, multiple linear regression, and logistic regression analyses. Main Outcome Measures: Associations of PEDT with NIH-CPSI. Results: The mean age was 50.4±5.5 years. In total, 2,205 (24.9%) men had prostatitis-like symptoms (NIH-CPSI pain score of ≥4 and perineal or ejaculatory pain), and 618 (7.0%) men had moderate to severe symptoms (NIH-CPSI pain score of ≥8). Additionally, 2,144 men (24.2%) were classified as demonstrating PE (PEDT>10). The PEDT score was found to have a significant positive correlation with the NIH-CPSI pain domain score (correlation coefficient=0.206; P<0.001). After adjusting for age, metabolic syndrome status, testosterone level, and IIEF score, there was no change in the positive correlation between the NIH-CPSI pain domain score and PEDT score (Beta=0.175; P<0.001). After adjusting for age, testosterone level, metabolic syndrome, and IIEF score, the odds ratio (OR) for PE significantly increased with the severity of pelvic pain (mild prostatitis-like symptoms, OR for PE: 1.269, 95% confidence interval: 1.113-1.447; moderate to severe symptoms, OR for PE: 2.134: 95% confidence interval: 1.782-2.557). Conclusions: Our data showed a significant correlation between the PEDT score and the NIH-CPSI score. We suggest routine screening for CP/CPPS in men with PE and PE in men with CP/CPPS. © 2014 International Society for Sexual Medicine.

Jeon H.J.,Sungkyunkwan University
Journal of the Korean Medical Association | Year: 2011

Suicide is the fourth leading cause of death in South Korea, which is the highest rate among the Organization for Economic Cooperation and Development member countries. The World Health Organization worldwide initiative for the prevention of suicide reported that there are at least 20 suicide attempts for every suicide committed. The lifetime prevalence of suicidal ideation, planning, and attempts in South Korea was 15.2%, 3.3%, and 3.2% (single 2.1% and multiple 1.1%), respectively. Suicide attempts showed a significant association with mental disorders, especially major depressive disorder in a Korea-based community study. Brain neuroimaging studies showed prefrontal localized hypofunction and impaired serotonergic responsivity in those attempting suicide, which are also typical findings in patients with depression. Postmortem studies have reported that approximately 60% of suicide victims suffered from major depressive disorder and other mood disorders. Family studies have suggested a genetic linkage between suicide and depression. In conclusion, suicide and suicidal behaviors are significantly associated with depression. Suicide is a medical condition which is treatable and preventable, and suicide rates can be reduced through early diagnosis and treatment for depression. Regular surveys for suicide and depression an essential tool for establishing a national policy for suicide prevention. © Korean Medical Association.

Jeon N.J.,Korea Research Institute of Chemical Technology | Lee J.,Korea Research Institute of Chemical Technology | Noh J.H.,Korea Research Institute of Chemical Technology | Nazeeruddin M.K.,Institute of Chemical science and Engineering | And 3 more authors.
Journal of the American Chemical Society | Year: 2013

A set of three N,N-di-p-methoxyphenylamine-substituted pyrene derivatives have successfully been synthesized and characterized by 1H/ 13C NMR spectroscopy, mass spectrometry, and elemental analysis. The optical and electronic structures of the pyrene derivatives were adjusted by controlling the ratio of N,N-di-p-methoxyphenylamine to pyrene, and investigated by UV/vis spectroscopy and cyclic voltammetry. The pyrene derivatives were employed as hole-transporting materials (HTMs) in fabricating mesoporous TiO2/CH3NH3PbI3/HTMs/Au solar cells. The pyrene-based derivative Py-C exhibited a short-circuit current density of 20.2 mA/cm2, an open-circuit voltage (Voc) of 0.886 V, and a fill factor of 69.4% under an illumination of 1 sun (100 mW/cm2), resulting in an overall power conversion efficiency of 12.4%. The performance is comparable to that of the well-studied spiro-OMeTAD, even though the V oc is slightly lower. Thus, this newly synthesized pyrene derivative holds promise as a HTM for highly efficient perovskite-based solar cells. © 2013 American Chemical Society.

Jeon N.J.,Korea Research Institute of Chemical Technology | Noh J.H.,Korea Research Institute of Chemical Technology | Kim Y.C.,Korea Research Institute of Chemical Technology | Yang W.S.,Korea Research Institute of Chemical Technology | And 3 more authors.
Nature Materials | Year: 2014

Organolead trihalide perovskite materials have been successfully used as light absorbers in efficient photovoltaic cells. Two different cell structures, based on mesoscopic metal oxides and planar heterojunctions have already demonstrated very impressive advances in performance. Here, we report a bilayer architecture comprising the key features of mesoscopic and planar structures obtained by a fully solution-based process. We used CH3 NH 3 Pb(I1-x Brx)3 (x=0.1-0.15) as the absorbing layer and poly(triarylamine) as a hole-transporting material. The use of a mixed solvent of 3-butyrolactone and dimethylsulphoxide (DMSO) followed by toluene drop-casting leads to extremely uniform and dense perovskite layers via a CH3 NH3 I-PbI2-DMSO intermediate phase, and enables the fabrication of remarkably improved solar cells with a certified power-conversion efficiency of 16.2% and no hysteresis. These results provide important progress towards the understanding of the role of solution-processing in the realization of low-cost and highly efficient perovskite solar cells. © 2014 Macmillan Publishers Limited.

Kyae B.,Pusan National University | Park J.-C.,Sungkyunkwan University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2014

Light fermionic/scalar dark matter (DM) (mDM ≈ 8GeV) neutral under the standard model can be responsible for the CDMS and CoGeNT signals, and the Fermi-LAT gamma-ray excesses. In order to explain them in a relatively simple framework, we have explored various DM annihilation and scattering processes, discussing important phenomenological constraints coming from particle physics. Assuming that the two independent observations have a common DM origin and the processes arise through a common mediator, DM should annihilate into tau/anti-tau lepton pairs through an s-channel, and scatter with nuclei through a t-channel process. To avoid the p-wave suppression, a new Higgs-like scalar field with a mass of O(1)TeV is necessary as a common mediator of both the processes. We propose a supersymmetric model realizing the scenario. © 2014 The Authors.

Kawai S.,Sungkyunkwan University | Okada N.,University of Alabama
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2014

We discuss the physics resulting from the supersymmetric Higgs-lepton inflation model and the recent CMB B-mode observation by the BICEP2 experiment. The tensor-to-scalar ratio r=0.20-0.05+0.07 of the primordial fluctuations indicated by the CMB B-mode polarization is consistent with the prediction of this inflationary model for natural parameter values. A salient feature of the model is that it predicts the seesaw mass scale M from the amplitude of the tensor mode fluctuations. It is found that the 68% (95%) confidence level (CL) constraints from the BICEP2 experiment give 927GeV. <. M<. 1.62TeV (751GeV. <. M<. 2.37TeV) for 50 e-foldings and 391GeV. <. M<. 795GeV (355GeV. <. M<. 1.10TeV) for 60 e-foldings. In the type I seesaw case, the right-handed neutrinos in this mass range are elusive in collider experiments due to the small mixing angle. In the type III seesaw, in contrast, the heavy leptons will be within the reach of future experiments. We point out that a significant portion of the parameter region corresponding to the 68% CL of the BICEP2 experiment will be covered by the Large Hadron Collider experiments at 14 TeV. © 2014 Elsevier B.V.

Lahaye R.J.W.E.,Sungkyunkwan University
Surface Science | Year: 2010

This is a study into the scattering dynamics of the alkaline ions Cs+, K+, Na+, and Li+ from an ice surface, and the process of abstracting water molecules by the scattered ions to form ion-water clusters as a result of the ion-dipole attraction. In a classical molecular dynamics computer simulation a semi-empirical ion-water interaction potential and a modified version of the TIP3P ice model are employed. The thickness of the ice structure at the surface greatly affects the abstraction efficiency. From a thin ice overlayer all alkaline ions exhibit similar scattering probabilities, but Cs+ abstracts water molecules most efficiently; its lower speed facilitates a mechanism where the Cs+ in its outgoing trajectory pulls water molecules out of the ice structure. From a thick ice structure the scattering probabilities decrease dramatically due to an effective energy transfer to the ice structure. A more grazing angle of incidence reduces the energy transfer and enhances the scattering probabilities for the lighter alkaline ions. The deprived formation of ion-water clusters in the simulations confirms that from thick ice the cluster formation probability is reduced by at least three orders of magnitude. © 2010 Elsevier B.V. All rights reserved.

Jeong J.H.,Sungkyunkwan University | Park T.G.,Korea Advanced Institute of Science and Technology | Kim S.H.,Yonsei University
Pharmaceutical Research | Year: 2011

A wide range of organic and inorganic materials have been used in the development of nano-scale selfassembling gene delivery systems to improve the therapeutic efficacy of nucleic acid drugs. Small interfering RNA (siRNA) has recently been recognized as a promising and potent nucleic acid medicine for the treatment of incurable genetic disorders including cancer; however, siRNA-based therapeutics suffer from the same delivery problems as conventional nucleic acid drugs such as plasmid DNA and antisense oligonucleotides. Many of the delivery strategies developed for nucleic acid drugs have been applied to siRNA therapeutics, but they have not produced satisfactory in vivo gene silencing efficiencies to warrant clinical trials. This review discusses recent progress in the development of self-assembled and nanostructured delivery systems for efficient siRNA-induced gene silencing and their potential application in clinical settings. © Springer Science+Business Media, LLC 2011.

Park S.,Ewha Womans University | Ko Y.H.,Sungkyunkwan University
Journal of Dermatology | Year: 2014

Primary infection with Epstein-Barr virus (EBV) is usually asymptomatic and, in a normal host, EBV remains latent in B cells after primary infection for the remainder of life. Uncommonly, EBV can infect T or natural killer (NK) cells in a person with a defect in innate immunity, and EBV infection can cause unique systemic lymphoproliferative diseases (LPD) of childhood. Primary infection in young children can be complicated by hemophagocytic lymphohistiocytosis or fulminant systemic T-cell LPD of childhood. Uncommonly, patients can develop chronic active EBV (CAEBV) disease-type T/NK LPD, which includes CAEBV infection of the systemic form, hydroa vacciniforme-like T-cell LPD, and mosquito-bite hypersensitivity. The clinical course of CAEBV disease-type T/NK LPD can be smoldering, persistent or progressive, depending on the balance between viral factors and host immunity. Aggressive NK-cell leukemia, hydroa vacciniforme-like T-cell lymphoma, or uncommonly extranodal NK/T-cell lymphoma can develop in children and young adults with CAEBV disease-type T/NK-cell LPD. Extranodal T/NK-cell lymphoma is a disease of adults, and its incidence begins to increase in the third decade and comprises the major subtype of T/NK LPD throughout life. Aggressive NK-cell leukemia and nodal T/NK-cell lymphoma of the elderly are fulminant diseases, and immune senescence may be an important pathogenetic factor. This review describes the current progress in identifying different types of EBV-associated T/NK-cell LPD and includes a brief presentation of data from Korea. © 2014 Japanese Dermatological Association.

Kong K.,University of Kansas | Park J.-C.,University of Kansas | Park J.-C.,Sungkyunkwan University
Nuclear Physics B | Year: 2014

Annihilation of light dark matter of mDM≈(10-40) GeV into the Standard Model fermions has been suggested as a possible origin of the gamma-ray excess at GeV energies in the Fermi-LAT data. In this paper, we examine possible model-independent signatures of such dark matter models in other experiments such as AMS-02, colliders, and cosmic microwave background (CMB) measurements. We point out that first generation of fermion final states is disfavored by the existing experimental data. Currently AMS-02 positron measurements provide stringent bounds on cross sections of dark matter annihilation into leptonic final states, and e+e- final state is in severe tension with this constraint, if not ruled out. The e+e- channel will be complementarily verified in an early stage of ILC and future CMB measurements. Light quark final states (qq-) are relatively strongly constrained by the LHC and dark matter direct detection experiments even though these bounds are model-dependent. Dark matter signals from annihilations into qq- channels would be constrained by AMS-02 antiproton data which will be released in very near future. In optimistic case, diffuse radio emission from nearby galaxy (clusters) and the galactic center might provide another hint or limit on dark matter annihilation. © 2014 The Authors.

Lee D.B.,Sungkyunkwan University
Corrosion Science | Year: 2013

Magnesium alloys of AZ31+0.3wt.%Ca and AZ31+0.3wt.%CaO were cast and oxidized between 450 and 650°C in atmospheric air. The initially added Ca and CaO enabled to cast the alloys in air without using environmentally hazardous SF6 gas, by forming a thin CaO-rich barrier layer at the surface during casting. A thin CaO-rich barrier layer was also formed at the surface during oxidation in air, thereby increasing the oxidation resistance of the AZ31 alloy considerably. The initially added Ca and CaO reacted with Al to become Al2Ca along the grain boundaries of the AZ31 alloy during casting. © 2013 Elsevier Ltd.

Weon B.M.,Sungkyunkwan University
Biogerontology | Year: 2015

As humans live longer, the precise modeling of mortality curves in very old age is becoming more important in aging research and public health. Here, we address a methodology that utilizes a modified stretched exponential survival function where a stretched exponent is relevant to heterogeneity in human populations. This function allows better estimation of the maximum human lifespan by providing a good description of the mortality curves in very old age. Demographic analysis of Swedish females over three recent decades revealed an important trend: the maximum human lifespan (existing around 125 years) gradually decreased at a constant rate of ~1.6 years per decade, while the characteristic life gradually increased at a constant rate of ~1.2 years per decade. This trend indicates that the number of aging people is increasingly concentrated at very old age, which is consistent with the definition of population aging. Importantly analyzing the stretched exponents would help in evaluating the heterogeneity trends in human populations. © 2015, Springer Science+Business Media Dordrecht.

Lee J.,Sungkyunkwan University
International Journal for Equity in Health | Year: 2015

Introduction: Disparities in the quality of health care and treatment among racial or ethnic groups can result from unequal access to medical care, disparate treatments for similar severities of symptoms, and wide divergence in general health status among individuals. Such disparities may be eliminated through better use of health information technology (IT). Investment in health IT could foster better coordinated care, improve guideline compliance, and reduce the likelihood of redundant testing, thereby encouraging more equitable treatment for underprivileged populations. However, there is little research exploring the impact of health IT investment on disparities of process of care. Methodology: This study examines the impact of health IT investment on waiting times - from admission to the date of first principle procedure - among different racial and ethnic groups, using patient and hospital data for the state of California collected from 2001 to 2007. The final sample includes 14,056,930 patients admitted with medical diseases to 316 unique, acute-care hospitals over a seven-year period. The linear random intercept and slope model was employed to examine the impacts of health IT investment on waiting time, while controlling for patient, disease, and hospital characteristics. Results: Greater health IT investment was associated with shorter waiting times, and the reduction in waiting times was greater for non-White than for White patients. This indicates that minority populations could benefit from health IT investment with regard to process of care. Conclusion: Investments in health IT may reduce disparities in process of care. © 2015 Lee; licensee BioMed Central.

Jeong S.Y.,Sungkyunkwan University | Lim S.M.,Korea Institute of Radiological and Medical Sciences
Nuclear Medicine and Biology | Year: 2012

Purpose: The purpose of this prospective study was to clarify the value of FLT PET and FET PET for the noninvasive grading and prognosis of newly diagnosed gliomas. Materials and methods: Twenty patients with newly diagnosed gliomas were investigated with FLT and FET PET before surgery. FLT and FET uptakes were assessed by the maximum standardized uptake (SUVmax) of tumor, and the ratio to uptake in the normal brain parenchyma (TNR). All tumors were graded by WHO system. Results: FLT PET detected all 17 high-grade gliomas (HGG) and did not detect all 3 low-grade gliomas (LGG). FET PET detected all 20 HGG and LGG regardless of grading. The average FLT SUVmax in HGG and LGG was 1.51 ± 0.72 and 0.30 ± 0.07, and the average FLT TNR in HGG and LGG was 5.52 ± 3.09 and 1.12 ± 0.14, respectively. The differences of FLT SUVmax and TNR between HGG and LGG were statistically significant (p= 0.0069, p= 0.0070). The average FET SUVmax in HGG and LGG was 2.68 ± 0.86 and 1.36 ± 0.15, and the average FET TNR in HGG and LGG was 2.31 ± 0.73 and 1.27 ± 0.12, respectively. The differences of FET SUVmax and TNR between HGG and LGG were statistically significant (p= 0.0129, p= 0.0095). Conclusions: FET PET has higher sensitivity in detection of gliomas rather than FLT PET, but it seems that FLT PET is better than FET PET for noninvasive grading and predicting prognosis of newly diagnosed gliomas, considering high contrast of FLT and overlap of FET uptakes between HGG and LGG. © 2012 Elsevier Inc.

Chung S.E.,Sungkyunkwan University
Korean journal of ophthalmology : KJO | Year: 2012

This retrospective observational case series on eyes from three patients was done to elucidate the developmental mechanism of spontaneous reattachment of rhegmatogenous retinal detachment (SRRRD). The study eyes of each patients showed evidence of retinal break and diffuse retinal pigmentary change. Ultrasound biomicroscopic examination revealed vitreous fibers attached to the area around the retinal break. Posterior vitreous attachment was confirmed in each eye. A thin fibrovascular membrane incompletely sealing the retinal break was noted in one case. We suggest that the vitreous attachment around the retinal break and the sealing of the break with adjacent vitreous fibers seem to be involved in the developmental mechanism of SRRRD.

To compare the diagnostic accuracy and sensitivity of combined gadoxetic acid-enhanced magnetic resonance imaging (MRI) and diffusion-weighted imaging (DWI) with each imaging approach alone for detecting small hepatic metastases (≤ 1.5 cm). Institutional review board approved this retrospective study and waived informed patient consent. Eighty-six patients with 179 liver metastases underwent liver MRI including unenhanced and gadoxetic acid-enhanced imaging and DWI at 3.0 T. Three image sets including unenhanced images-gadoxetic acid set (early dynamic and hepatocyte phase), DWI set, and the combined set-were analyzed independently and in consensus by 2 observers for detecting liver metastases using receiver operating characteristic analysis. There was a tendency toward an increased diagnostic accuracy for the combined set (mean, 0.965) compared with that for each image set alone (mean, 0.911 for gadoxetic acid set; 0.926 for DWI set). The combined set showed better sensitivity (mean, 97.47%/95.0%: values on per-lesion/per-patient basis) than each imaging set alone (mean, 90.7%/83.7% for gadoxetic acid set; 91.6%/83.0% for DWI set) (P < 0.05) on both per-lesion basis and per-patient basis. All image sets showed similar positive predictive values. The combination of gadoxetic acid-enhanced MRI and DWI yielded better diagnostic accuracy and sensitivity in the detection of small liver metastasis than each magnetic resonance scan sequence alone.

Rhee H.-C.,Sungkyunkwan University
Osong Public Health and Research Perspectives | Year: 2013

Objectives: As the prevalence of tsutsugamushi disease has tripled over the past decade to affect 8307 people in October 2012, this study is conducted to estimate the willingness to pay (WTP) to avoid infection of tsutsugamushi disease in order to analyze the loss of value caused by climate change diseases. Methods: The double-bounded dichotomous choice of contingent valuation method was used to estimate the WTP to avoid infection of tsutsugamushi disease, through surveys conducted in the patient group (. n = 120) and the control group (. n = 240). Results: More young people in the family, higher level of awareness of risks caused by climate change, more male members (as opposed to female), higher income, lower suggested bid, and greater WTP, is better positioned to avoid infection of disease. The mean of the amount of WTP has been estimated to be 3689 Kwon per month. Conclusion: As people have become increasingly aware of climate change diseases, WTP to avoid infection of tsutsugamushi disease has increased accordingly. The implicit loss of value due to climate change diseases is becoming increasingly higher. Therefore, there should be stronger and more aggressive promotional activities to prevent people from being infected with tsutsugamushi disease and to build a healthier society free from climate change diseases. © 2013 .

Jeon N.J.,Korea Research Institute of Chemical Technology | Lee H.G.,Korea Research Institute of Chemical Technology | Kim Y.C.,Korea Research Institute of Chemical Technology | Seo J.,Korea Research Institute of Chemical Technology | And 4 more authors.
Journal of the American Chemical Society | Year: 2014

Three spiro-OMeTAD derivatives have been synthesized and characterized by 1H/13C NMR spectroscopy and mass spectrometry. The optical and electronic properties of the derivatives were modified by changing the positions of the two methoxy substituents in each of the quadrants, as monitored by UV-vis spectroscopy and cyclic voltammetry measurements. The derivatives were employed as hole-transporting materials (HTMs), and their performances were compared for the fabrication of mesoporous TiO2/CH 3NH3PbI3/HTM/Au solar cells. Surprisingly, the cell performance was dependent on the positions of the OMe substituents. The derivative with o-OMe substituents showed highly improved performance by exhibiting a short-circuit current density of 21.2 mA/cm2, an open-circuit voltage of 1.02 V, and a fill factor of 77.6% under 1 sun illumination (100 mW/cm2), which resulted in an overall power conversion efficiency (PCE) of 16.7%, compared to ∼15% for conventional p-OMe substituents. The PCE of 16.7% is the highest value reported to date for perovskite-based solar cells with spiro-OMeTAD. © 2014 American Chemical Society.

Waist circumference (WC) is a risk factor for metabolic syndrome and is related to insulin resistance (IR) and nonalcoholic fatty liver disease (NAFLD). The purpose of this study was to determine the association between WC and IR and NAFLD in apparently healthy Korean adults. The volunteers included in this cross-sectional study comprised 9,159 adults (5,052 men, 4,107 women) who participated in a comprehensive health checkup program. IR was evaluated by the homeostasis model assessment of IR (HOMA-IR) and was considered to be present when the HOMA-IR score was >2. NAFLD was evaluated by ultrasound examination. Elevated alanine aminotransferase (ALT) was defined as >40 IU/L in men and >35 IU/L in women. Logistic regression was performed to determine the odds ratios (ORs) and 95% confidence intervals (95% CIs) for NAFLD, IR, and ALT according to categorized levels of WC. NAFLD was found in 2,553 (27.9%) of the participants (82.6% men, 17.4% women), while IR and elevated ALT were found in 17.2% (68.1% men, 31.9% women) and 10% (83% men, 17% women), respectively. After adjusting for confounding factors, the prevalence of NAFLD, IR, and elevated ALT was significantly associated with increases in WC quartile: highest quartile for NAFLD in men, OR=15.539, 95% CI=12.687-19.033; highest quartile for NAFLD in women, OR=48.732, 95% CI=23.918-99.288 (P<0.001); and highest quartile for IR in men, OR=17.576, 95% CI=13.283-23.255; highest quartile for IR in women, OR=11.078, 95% CI=7.813-15.708 (P<0.001); highest quartile for elevated ALT in men, OR=7.952, 95% CI=6.046-10.459; and highest quartile for elevated ALT in women, OR=8.487, 95% CI=4.679-15.395 (P<0.001). WC contributes to IR and NAFLD in apparently healthy Korean adults, and thus may be an important factor in the development of IR and NAFLD.

Chung S.E.,Sungkyunkwan University
Korean journal of ophthalmology : KJO | Year: 2010

To describe the clinical and optical coherence tomography (OCT) features of a macular hole (MH) or its precursor lesion in patients treated with systemic antiestrogen agents. We reviewed the medical history of the patient, ophthalmic examination, and both fundus and OCT findings. Three female patients receiving antiestrogen therapy sought treatment for visual disturbance. All of the patients showed foveal cystic changes with outer retinal defect upon OCT. Visual improvement was achieved through surgery for the treatment of MH in two patients. Antiestrogen therapy may result in MH or its precursor lesion, in addition to perifoveal refractile deposits. OCT examination would be helpful for early detection in such cases.

Nam S.-G.,Pohang University of Science and Technology | Hwang E.H.,Sungkyunkwan University | Lee H.-J.,Pohang University of Science and Technology
Physical Review Letters | Year: 2013

We report measurements of heat transport along the edge conducting channels in monolayer graphene in the integer quantum Hall regime. Hot charge carriers are injected to the edge channels, and the thermoelectric voltage is measured at a distance along the edge from the heat injection point. We confirm that heat transport in graphene in the quantum Hall regime is chiral and the thermoelectric signal is correlated with the charge conductance of ballistic transport, following the Mott relation. The thermoelectric signal decays with distance from the heater, indicating that carriers are partially thermalized during edge transmission. © 2013 American Physical Society.

Kim M.Y.,Yonsei University | Jeong W.K.,Sungkyunkwan University | Baik S.K.,Yonsei University
World Journal of Gastroenterology | Year: 2014

With advances in the management and treatment of advanced liver disease, including the use of antiviral therapy, a simple, one stage description for advanced fibrotic liver disease has become inadequate. Although refining the diagnosis of cirrhosis to reflect disease heterogeneity is essential, current diagnostic tests have not kept pace with the progression of this new paradigm. Liver biopsy and hepatic venous pressure gradient measurement are the gold standards for the estimation of hepatic fibrosis and portal hypertension (PHT), respectively, and they have diagnostic and prognostic value. However, they are invasive and, as such, cannot be used repeatedly in clinical practice. The ideal noninvasive test should be safe, easy to perform, inexpensive, reproducible as well as to give numerical and accurate results in real time. It should be predictive of long term outcomes related with fibrosis and PHT to allow prognostic stratification. Recently, many types of noninvasive alternative tests have been developed and are under investigation. In particular, imaging and ultrasound based tests, such as transient elastography, have shown promising results. Although most of these noninvasive tests effectively identify severe fibrosis and PHT, the methods available for diagnosing moderate disease status are still insufficient, and further investigation is essential to predict outcomes and individualize therapy in this field. © 2014 Baishideng Publishing Group Co., Limited. All rights reserved.

Kim S.M.,Sungkyunkwan University
Synlett | Year: 2014

(A) List and co-worker reported the first proline-catalyzed enantioselective Mannich reaction of N-Boc imines with acetaldehyde.2 This method is one of the simplest ways to synthesize enantiopure 3-amino acid derivatives. It is noteworthy that unwanted side reactions were successfully suppressed by using an excess of acetaldehyde (5-10 equiv). (B) The direct asymmetric crossed-aldol reaction of acetaldehyde was reported by the group of Hayashi.3 In particular, trifluoromethylsubstituted diarylprolinol 1 was found to be an effective organocatalyst and gave excellent enantioselectivities. Due to its instability, the aldehyde intermediate was transformed into the corresponding alcohol using NaBH4 in methanol. (C) Hayashi, Uchimaru, and co-workers reported that diarylprolinol silyl ether 2 catalyzed the asymmetric Mannich reaction between N-protected imines and acetaldehyde (5 equiv).4 A wide range of aromatic N-benzoyl , N-Boc , and N-Ts imines were investigated. The reaction proceeded smoothly to afford 3-aminoaldehydes with high enantioselectivity. The aldehydes were reduced to the corresponding alcohols using LiAlH4. (D) Maruoka and co-workers designed a new catalyst motif - axially chiral bifunctional amino sulfonamide catalyst 3 - and performed asymmetric Mannich reactions of N-Boc imines with acetaldehyde (36 equiv).5 As a result, the desired products were obtained in good yields and excellent enantioselectivities (up to 99% ee) in most cases. Undesired side reactions were suppressed with this less nucleophilic chiral amino sulfonamide. (E) List and co-workers reported the proline-catalyzed double Mannich reaction of N-Boc imines with acetaldehyde.6 This method provided pseudo-C2-symmetric ß,ß'-diaminoaldehydes with extremely high diastereo- and enantioselectivities (dr 99:1, er 300:1) by reacting one equivalent of acetaldehyde with three equivalents of both aromatic and aliphatic N-Boc imines via stepwise enamine catalytic activation. (F) Greck et al. investigated the one-pot, organocatalytic a,a-bifunctionalization of acetaldehyde with two different electrophiles (N-benzoyl imine and di-tert-butylazodicarboxylate) using diarylprolinol silyl ether catalyst 2.7 This reaction consists of a tandem Mannich reaction-electrophilic amination. syn-Selective 2,3-diaminoalcohols were obtained with moderate yields and high diastereoand enantioselectivities (dr up to 96:4, up to 98% ee). (G) In N-heterocyclic carbene (NHC) catalysis, the chemoselective intermolecular cross-acyloin condensation reaction of two different aldehydes is one of the biggest challenges. Yang and co-workers established an efficient chemoselective catalytic system using acetaldehyde as the acyl anion source.8 The most striking feature is the switch of chemoselectivity by changing the scaffold of the NHC catalyst. (H) Yang and co-workers reported the intermolecular Stetter reaction of various Michael acceptors, including trans-chalcone derivatives, with acetaldehyde as a biomimetic acyl anion source.9 The authors also extended their work to the enantioselective Stetter reaction which resulted in moderate to good enantioselectivities (up to 76% ee) for the corresponding products. © Georg Thieme Verlag Stuttgart · New York.

Sung K.-C.,Sungkyunkwan University | Wild S.H.,University of Edinburgh | Byrne C.D.,University of Southampton
Journal of Clinical Endocrinology and Metabolism | Year: 2013

Context: Fatty liver is associated with an increased risk of type 2 diabetes, but whether an increased risk remains in people in whom fatty liver resolves over time is not known. Objective: The objective of the study was to assess the risk of incident diabetes at a 5-year follow-up in people in whom: 1) new fatty liver developed; 2) existing fatty liver resolved, and 3) fatty liver severity worsened over 5 years. Design and Methods: A total of 13 218 people without diabetes at baseline from a Korean occupational cohort were examined at baseline and after 5 years, using a retrospective study design. Fatty liver status was assessed at baseline and follow-up as absent, mild, or moderate/severe using standard ultrasound criteria. Adjusted odds ratios (aORs) and 95% confidence intervals (CIs) for incident diabetes at follow-up were estimated after controlling for multiple potential confounders. Results: Two hundred thirty-four people developed incident diabetes. Over 5 years, fatty liver resolved in 828, developed in 1640, and progressed from mild to moderate/severe in 324 people. Resolution of fatty liver was not associated with a risk of incident diabetes [aOR 0.95 (95% CIs 0.46, 1.96), P .89]. Development of new fatty liver was associated with incident diabetes [aOR 2.49 (95% CI 1.49, 4.14), P .001]. In individuals in whom severity of fatty liver worsened over 5 years (from mild to moderate/severe), there was a marked increase in the risk of incident diabetes [aOR 6.13 (2.56, 95% CI 14.68) P.001 (compared with the risk in people with resolution of fatty liver)]. Conclusion: Change in fatty liver status over time is associated with markedly variable risks of incident diabetes. Copyright © 2013 by The Endocrine Society.

OBJECTIVE:: To evaluate the association between anesthetic management before and after graft reperfusion and early graft regeneration in living donor liver transplantation (LDLT). BACKGROUND:: Sufficient graft regeneration is essential for the success of LDLT. Diverse signals start to trigger liver regeneration immediately after graft reperfusion. METHODS:: : Graft volume at 14?±?2 days after LDLT was measured in 379 consecutive recipients using computed tomography images with 3-dimensional reconstruction. The association between anesthetic variables and the degree of graft regeneration for 2 weeks was analyzed using simple and multiple linear regressions. The anesthetic variables included hemodynamics, laboratory measurements, vasoactive drugs, and blood products transfusion. RESULTS:: The degree of graft regeneration for 2 weeks was 52% in median and ranged from 5% to 123%. Platelet transfusion was identified as the sole independent anesthetic factor contributing to graft regeneration. Platelet concentrate transfusion of 1 to 6 units vs none was correlated with a 6.5% increase in graft regeneration (P = 0.012). Platelet concentrate transfusion of more than 6 units vs none was further correlated with an 18.4% increase in regeneration (P < 0.001). In the subgroup of recipients without intraoperative platelet transfusion, mean platelet count measured during the intraoperative reperfusion phase was positively associated with graft regeneration (P = 0.033). CONCLUSIONS:: Graft regeneration after LDLT increased in relation to a graded increase in the amount of transfused platelets and higher postreperfusion platelet counts during surgery. These results offer additional evidence regarding the important role of platelets in initiating liver regeneration and, furthermore, the indications for and the benefits vs risks of platelet transfusion during LDLT. Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.

Guruacharya S.,Nanyang Technological University | Niyato D.,Nanyang Technological University | Kim D.I.,Sungkyunkwan University | Hossain E.,University of Manitoba
IEEE Transactions on Wireless Communications | Year: 2013

This paper considers the problem of downlink power allocation in an orthogonal frequency-division multiple access (OFDMA) cellular network with macrocells underlaid with femtocells. The femto-access points (FAPs) and the macro-base stations (MBSs) in the network are assumed to compete with each other to maximize their capacity under power constraints. This competition is captured in the framework of a Stackelberg game with the MBSs as the leaders and the FAPs as the followers. The leaders are assumed to have foresight enough to consider the responses of the followers while formulating their own strategies. The Stackelberg equilibrium is introduced as the solution of the Stackelberg game, and it is shown to exist under some mild assumptions. The game is expressed as a mathematical program with equilibrium constraints (MPEC), and the best response for a one leader-multiple follower game is derived. The best response is also obtained when a quality-of-service constraint is placed on the leader. Orthogonal power allocation between leader and followers is obtained as a special case of this solution under high interference. These results are used to build algorithms to iteratively calculate the Stackelberg equilibrium, and a sufficient condition is given for its convergence. The performance of the system at a Stackelberg equilibrium is found to be much better than that at a Nash equilibrium. © 2002-2012 IEEE.

Sakthivel R.,Sungkyunkwan University | Anandhi E.R.,Medical University of South Carolina
International Journal of Control | Year: 2010

In order to describe various real-world problems in physical and engineering sciences subject to abrupt changes at certain instants during the evolution process, impulsive differential equations have been used to describe the system model. In this article, the problem of approximate controllability for nonlinear impulsive differential equations with state-dependent delay is investigated. We study the approximate controllability for nonlinear impulsive differential system under the assumption that the corresponding linear control system is approximately controllable. Using methods of functional analysis and semigroup theory, sufficient conditions are formulated and proved. Finally, an example is provided to illustrate the proposed theory. © 2010 Taylor & Francis.

OBJECTIVE:: To determine whether autotransfusion of red blood cells (RBCs) salvaged during liver transplantation is associated with the recurrence of hepatocellular carcinoma (HCC). BACKGROUND:: Blood salvage is widely used during liver transplantation to reinfuse salvaged autologous RBCs and reduce allogeneic transfusion. However, the reintroduction of cancer cells via autotransfusion is a major concern in HCC patients. METHODS:: Among 397 patients who underwent living-donor liver transplantation for HCC, 97 of 114 recipients without intraoperative autotransfusion were matched with 222 of 283 recipients with intraoperative autotransfusion with unfixed matching ratio using the propensity score based on age, sex, allogeneic transfusion, immunosuppression, tumor biology, and others. Competing risks Cox regression was used to compare HCC recurrence risk of the 2 paired groups. RESULTS:: Recipients in autotransfusion group received 1177?±?1318 mL of salvaged RBCs during surgery. A leukocyte depletion filter was used for all autotransfused RBCs. Cumulative HCC recurrence rate at 1, 2, and 5 years after transplantation were 10.4% (5.3%–17.6%), 19.1% (11.6%–28.0%), and 24.1% (15.2%–34.0%) for nonautotransfusion group and 10.8% (7.2%–15.4%), 14.9% (10.5%–20.0%), and 20.3% (14.9%–26.4%) for autotransfusion group, respectively. Autotransfusion versus nonautotransfusion group was not significantly different in overall recurrence [hazard ratio (HR) 0.85, 95% confidence interval (CI) 0.47–1.53, P?=?0.579] and intrahepatic recurrence (HR 0.75, 95% CI 0.36–1.56) or extrahepatic recurrence (HR 1.00, 95% CI 0.49–2.04). CONCLUSIONS:: We found no evidence of a significant impact of autotransfusion on posttransplant HCC recurrence. Thus, salvaged and filtered RBCs could be used in HCC patients undergoing liver transplantation with potential benefits from avoiding allogeneic RBCs transfusion and its complications. Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.

Yi C.H.,Sungkyunkwan University
Korean journal of ophthalmology : KJO | Year: 2010

To compare clinical outcomes after deep lamellar endothelial keratoplasty (DLEK) with Descemet stripping endothelial keratoplasty (DSEK) performed as initial cases by a single surgeon. Sixteen patients with corneal endothelial were enrolled. Eight patients (8 eyes) underwent DLEK and 8 patients (8 eyes) DSEK. We measured uncorrected visual acuity, best corrected visual acuity (BCVA), manifest refraction, corneal endothelial count, interface opacity via Schiempflug imaging, and contrast sensitivity, as well as tracked postoperative complications over the first postoperative year. Primary graft failure occurred in two DLEK cases and one DSEK case, all of which were excluded for further analysis. The average 12-month postoperative BCVA was 20/70 in the DLEK group and 20/50 in the DSEK group, with the difference not statistically significant. No significant differences were identified between the 2 groups in terms of mean spherical equivalent and refractive astigmatism, although individuals in the DSEK group tended toward hyperopia. The average endothelial cell count at postoperative month 12 was 1849+/-494 in the DLEK group and 1643+/-417 cells/mm(2) in the DSEK group, representing cell losses of 26.2% and 31.9%, respectively. No significant differences in endothelial cell count or endothelial cell loss were observed between groups. Early postoperative donor disc dislocation occurred in two eyes after DLEK and one eye after DSEK. Interface opacities and contrast sensitivities were similarly not significantly different between groups. No significant differences in any assessed clinical outcome were observed between individuals undergoing DLEK and DSEK, when performed as initial cases by a single surgeon.

Shin D.-H.,Sungkyunkwan University
International Journal of Mobile Communications | Year: 2010

This study integrates cognitive and affective attitudes as the primary factors of influence to formulate a Ubiquitous Computing Acceptance Model (UCAM), which is intended to predict whether potential users will accept ubiquitous computing (u-computing). The goal of this study was to empirically assess the UCAM by identifying the factors that contribute to user attitudes and intentions in u-computing environments. This study is one of the first to empirically evaluate the relationships among trust, security, privacy, usefulness, ease of use and behavioural intention in the ubiquitous city context. Copyright © 2010 Inderscience Enterprises Ltd.

Yang J.,Queens University | Kim I.-M.,Queens University | Kim D.I.,Sungkyunkwan University
IEEE Transactions on Wireless Communications | Year: 2013

Cooperative jamming for multiuser multiple input multiple output (MIMO) broadcast channel is studied to enhance the physical layer security with the help of a friendly jammer. We assume the base station transmits multiple independent data streams to multiple legitimate users. During the transmission, however, there are multiple eavesdroppers with multiple antennas that have interests in the streams from the base station. In order to wiretap the desired streams, the eavesdroppers may collude or not, and maximize the signal-to-interference-plus-noise ratio (SINR) of the desired streams using receive beamforming. The optimal cooperative jammer is designed to keep the achieved SINR at eavesdroppers below a threshold to guarantee that the transmission from the base station to legitimate users is confidential. One main advantage of the proposed cooperative jamming scheme is that no modification is needed for the existing precoding schemes at the base station and decoding schemes at legitimate users. Thus, any existing practical precoding/decoding schemes for multiuser MIMO broadcast channel can be applied directly with the help of a friendly jammer using the proposed cooperative jamming. © 2002-2012 IEEE.

Yoo C.,Sungkyunkwan University
Journal of Geotechnical and Geoenvironmental Engineering | Year: 2010

This paper presents the results of a numerical investigation into the performance of geosynthetic-encased stone columns (GESCs) installed in soft ground for embankment construction. A three-dimensional finite-element model was employed to carry out a parametric study on a number of governing factors such as the consistency of soft ground, the geosynthetic encasement length and stiffness, the embankment fill height, and the area replacement ratio. The results indicate among other things that additional confinement provided by the geosynthetic encasement increases the stiffness of the stone column and reduces the degree of embankment load transferred to the soft ground, thereby decreasing the overall settlement. It is also shown that the geosynthetic encasement has a greater impact for cases with larger stone column spacing and/or weaker soil. Also revealed is that unlike isolated column loading conditions, full encasement may be necessary to ensure maximum settlement reduction when implementing GESCs under an embankment loading condition. Practical implications of the findings are discussed in detail. © 2010 ASCE.

Cross-sectional studies have documented that 2-10% of patients who are chronically infected with hepatitis C virus (HCV) are also positive for hepatitis B virus (HBV) surface antigen (HBsAg). Data related to HCV-HBV coinfection are lacking in Korea. This study evaluated the clinical characteristics, the treatment efficacy of peginterferon alfa plus ribavirin, and the changes induced by such treatment in HBV status in chronic hepatitis C (CHC) patients coinfected with HBV. Eighteen (2.37%) HBsAg-positive CHC patients were selected from among the 758 subjects from the K(G)yeonggi-Incheon Peginterferon alfa and ribavirin in chronic hepatitis C Treatment (KIPECT) study, which evaluated the treatment efficacy and safety of peginterferon alfa plus ribavirin in CHC patients. Data on changes in the status of HBV infections were obtained. HCV genotype 1b was the most common (44%). The overall sustained virologic response rate was 72% in all patients, and 60% and 87.5% in genotypes 1 and 2, respectively. Two of the 18 patients were positive for HBeAg, and 15 had baseline HBV DNA level of less than 2,000 IU/mL. Two of the three whose levels exceeded this threshold showed no detectable DNA after treatment. After the completion of treatment, serum HBV DNA levels were increased in the two patients whose baseline HBV DNA levels were less than 2,000 IU/mL. The prevalence of HBV coinfection in CHC patients was 2.37% and most of the patients were inactive carriers. The treatment efficacy was similar to that of HCV mono-infection. Reactivation of HBV replication was observed in some patients after CHC treatment.

Objective: The purpose of this study is to assess the prevalence of abnormal CT findings in patients with surgically proven ruptured endometriotic cysts, as compared with those abnormal CT findings of ruptured ovarian functional cysts. Materials and Methods: This study included 13 retrospectively identified patients with surgically confirmed ruptured ovarian endometriotic cysts and who had also undergone preoperative CT scanning during the previous seven years. As a comparative group, 25 cases of surgically confirmed ruptured ovarian functional cysts were included. We assessed the morphologic features of the cysts and the ancillary findings based on CT. Results: For the endometriotic cysts, the mean maximum cyst diameter was significantly larger than that of the functional cysts (70.1 mm versus 36.4 mm, respectively, p < 0.05). The endometriotic cysts frequently had a multilocular shape and a thicker cyst wall, as compared to that of functional cysts, and these differences were statistically significant. Among the ancillary findings, endometriotic cysts showed a significantly higher prevalence of loculated ascites, ascites confined to the pelvic cavity without extension to the upper abdomen, and peritoneal strandings and infiltrations (p < 0.05). Although 11 of the 25 cases of functional cysts showed active extravasation of contrast material at the ovarian bleeding site, only one of 13 cases of endometriotic cysts showed active extravasation. Conclusion: The diagnosis of ruptured endometriotic cyst should be suspected for a woman in whom CT reveals the presence of multilocular or bilateral ovarian cysts with a thick wall and loculated ascites confined to the pelvic cavity with pelvic fat infiltrations.

Huh J.W.,Sungkyunkwan University | Kim H.R.,Chonnam National University | Kim Y.J.,Chonnam National University
Diseases of the Colon and Rectum | Year: 2013

BACKGROUND: The clinical pretreatment factors that accurately predict response to chemoradiation in rectal cancer are not currently known. OBJECTIVE: The aim of this study is to evaluate the clinical factors associated with a pathological complete response after preoperative chemoradiotherapy for rectal cancer. DESIGN: This study is a retrospective review of prospectively collected data. SETTING: This study was conducted at a tertiary care hospital/referral center in South Korea. PATIENTS: From December 2000 to September 2011, a total of 391 consecutive patients with rectal cancer who underwent neoadjuvant chemoradiotherapy followed by radical surgery were identified. The treatment consisted of concurrent chemoradiation, which included preoperative 5-fluorouracil-based chemotherapy and pelvic radiation (median, 5040 cGy); this was followed 8 weeks later (median, 57 days) by surgery with curative intent. MAIN OUTCOME MEASURES: The primary outcome measured was the clinicopathological comparison between pathological complete response (n = 57, 14.6%) and non-pathological complete response (n = 334, 85.4%) groups. RESULTS: The pathological complete response groups had a higher percentage of noncircumferential tumors, nonmacroscopic ulceration, well differentiation, small tumor diameter, early clinical T stage, early clinical N stage, or low levels of pretreatment CEA than the non-pathological complete response group. In multivariate regression analysis, independent predictors of a higher pathological complete response rate were noncircumferentiality (p = 0.007; OR, 3.214), nonmacroscopic ulceration (p = 0.002; OR, 6.702), and low pretreatment CEA level (p = 0.004; OR, 2.656). Significant differences in the pathological complete response rate existed among the 4 risk stratification groups (p < 0.001). For the prediction of pathological complete response by the clinical risk score model, the sensitivity was 64.1% and the specificity was 73.7% (area under the curve, 0.706; p < 0.001). LIMITATIONS: This study was limited because it was a single-institution study with a small sample size. CONCLUSIONS: Pretreatment clinical variables, including tumor circumferentiality, macroscopic ulceration, and CEA level, may be important determinants in achieving a pathological complete response. © 2013 The ASCRS.

Lee S.,Inha University | Kwon O.C.,Sungkyunkwan University
International Journal of Hydrogen Energy | Year: 2011

The potential of partial ammonia substitution to improve the safety of hydrogen use was evaluated computationally, using counterflow nonpremixed ammonia/hydrogen/air flames at normal temperature and pressure. The ammonia-substituted hydrogen/air flames were considered using a recent kinetic mechanism and a statistical narrow-band radiation model for a wide range of flame strain rates and the extent of ammonia substitution. The effects of ammonia substitution on the extinction limits and structure, including nitrogen oxide (NOx) and nitrous oxide (N2O) emissions, of nonpremixed hydrogen/air flames were investigated. Results show reduction of the high-stretch extinction (i.e.; blow-off) limits, the maximum flame temperature and the concentration of light radicals (e.g.; H and OH) with ammonia substitution in hydrogen/air flames, supporting the potential of ammonia as a carbon-free, clean additive for improving the safety of hydrogen use in nonpremixed hydrogen/air flames. For high-stretched flames, however, NO x and N2O emissions substantially increase with ammonia substitution even though ammonia substitution reduces flame temperature, implying that chemical effects (rather than thermal effects) of ammonia substitution on flame structure are dominant. Radiation effects on the extinction limits and flame structure are not remarkable particularly for high-stretched flames. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Kang K.,Sungkyunkwan University
Biochimica et Biophysica Acta - Biomembranes | Year: 2016

Extraordinary infrared-sensing ability of snake pit organs closely correlates with rich expression of TRPA1 transcripts in pit-innervating sensory neurons, strongly suggesting that TRPA1 is the molecular basis of the infrared detection. Here, it is shown that temperature coefficient Q10 (the fold current increase over 10 °C increase) of rattlesnake TRPA1 heterologously expressed in Xenopus oocytes increases proportionally to current amplitudes when appraised with two independent methods, the canonical Arrhenius plot analysis and newly devised Q10 scanning that assigns Q10 to each recorded temperature point. Moreover, for larger TRPA1 currents, the rise of Q10 from elevation of current sizes was steeper, yielding maximal Q10s up to ~ 100,000. TRPA1 from boas with less sensitive infrared-sensing ability was also sharply activated by temperature increase in oocytes, while Q10 rise from escalating current amplitudes was moderate compared to rattlesnake TRPA1. In contrast, thermal sensitivity of Drosophila TRPA1 was little dependent on current sizes, indicating that the steeply proportional current amplitude/thermosensitivity relationship is unique to the snake TRPA1s. Taken together, rattlesnake and boa TRPA1s are regulated to generate sufficient thermal sensitivity for infrared detection, providing an interesting context to further study the temperature-dependent activation mechanism of thermo-TRPs. © 2015 Elsevier B.V. All rights reserved.

Woo K.I.,Sungkyunkwan University
Current Opinion in Ophthalmology | Year: 2016

PURPOSE OF REVIEW: Epiblepharon is prevalent in East-Asian children. As the population in Asia is increasing, so is the demand for epiblepharon surgery. Surgeons should be familiar with the standards of beauty and needs of Asian people for epiblepharon management. This review provides a comprehensive summary of the published studies on the clinical manifestations, pathophysiology, and management of epiblepharon. RECENT FINDINGS: Astigmatism is prevalent in epiblepharon patients, which can contribute to amblyopia. Early surgery and visual rehabilitation is important for epiblepharon patients with a high degree of astigmatism and amblyopia. Various etiologic factors play a role in the pathophysiology of epiblepharon. Surgical procedures focusing on creation of a lower eyelid crease have been popular for treating epiblepharon in Western textbooks; however, this is not appropriate for Asian patients in whom, a crease may be undesirable. In selecting surgical methods, it is important to resect a minimal amount of skin-muscle to avoid the adverse effects of ectropion and eyelid retraction. SUMMARY: Although epiblepharon may resolve with facial growth, surgical correction is needed for cases in which there is significant corneal injury from the lash touch. Surgical management should focus on techniques that are effective, with little chance of complication, and do not create a lower eyelid crease. Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved.

Koh W.-J.,Sungkyunkwan University | Stout J.E.,Duke University | Yew W.-W.,Chinese University of Hong Kong
International Journal of Tuberculosis and Lung Disease | Year: 2014

Mycobacterium abscessus complex is a group of rapidly growing mycobacteria, and an emerging cause of nontuberculous mycobacterial lung disease in patients with cystic fibrosis and chronic lung diseases, such as bronchiectasis. M. abscessus complex is the most drugresistant of the mycobacterial pathogens, resulting in limited therapeutic options and a high treatment failure rate. M. abscessus complex is comprised of three closely related subspecies: M. abscessus (sensu stricto), M. massiliense and M. bolletii. M. abscessus encodes a functional erythromycin ribosomal methylase gene, erm(41), which modifies the binding site for macrolide antibiotics, causing inducible macrolide resistance. However, this inducible macrolide resistance is not seen in M. massiliense, as the erm(41) gene of this subspecies is non-functional. Accordingly, treatment success rates with macrolide-based antibiotic treatment are much higher in patients with M. massiliense infections than in those infected with M. abscessus. Precise speciation of M. abscessus complex is important for predicting antibiotic susceptibilities and patient outcome. © 2014 The Union.

Zhang H.,Zhejiang University | Jin M.,Xian University of Science and Technology | Xiong Y.,Anhui University of Science and Technology | Lim B.,Sungkyunkwan University | Xia Y.,Georgia Institute of Technology
Accounts of Chemical Research | Year: 2013

Palladium is a marvelous catalyst for a rich variety of reactions in industrial processes and commercial devices. Most Pd-catalyzed reactions exhibit structure sensitivity, meaning that the activity or selectivity depends on the arrangement of atoms on the surface. Previously, such reactions could only be studied in ultrahigh vacuum using Pd single crystals cut with a specific crystallographic plane. However, these model catalysts are far different from real catalytic systems owing to the absence of atoms at corners and edges and the extremely small specific surface areas for the model systems. Indeed, enhancing the performance of a Pd-based catalyst, in part to reduce the amount needed of this precious and rare metal for a given reaction, requires the use of Pd with the highest possible specific surface area. Recent advances in nanocrystal synthesis are offering a great opportunity to investigate and quantify the structural sensitivity of catalysts based on Pd and other metals. For a structure-sensitive reaction, the catalytic properties of Pd nanocrystals are strongly dependent on both the size and shape. The shape plays a more significant role in controlling activity and selectivity, because the shape controls not only the facets but also the proportions of surface atoms at corners, edges, and planes, which affect the outcomes of possible reactions. We expect catalysts based on Pd nanocrystals with optimized shapes to meet the increasing demands of industrial applications at reduced loadings and costs.In this Account, we discuss recent advances in the synthesis of Pd nanocrystals with controlled shapes and their resulting performance as catalysts for a large number of reactions. First, we review various synthetic strategies based on oxidative etching, surface capping, and kinetic control that have been used to direct the shapes of nanocrystals. When crystal growth is under thermodynamic control, the capping agent plays a pivotal role in determining the shape of a product by altering the order of surface energies for different facets through selective adsorption; the resulting product has the lowest possible total surface energy. In contrast, the product of a kinetically controlled synthesis often deviates from the thermodynamically favored structure, with notable examples including nanocrystals enclosed by high-index facets or concave surfaces.We then discuss the key parameters that control the nucleation and growth of Pd nanocrystals to decipher potential growth mechanisms and build a connection between the experimental conditions and the pathways to different shapes. Finally, we present a number of examples to highlight the use of these Pd nanocrystals as catalysts or electrocatalysts for various applications with structure-sensitive properties. We believe that a deep understanding of the shape-dependent catalytic properties, together with an ability to experimentally maneuver the shape of metal nanocrystals, will eventually lead to rational design of advanced catalysts with substantially enhanced performance. © 2012 American Chemical Society.

This paper presents the results of a numerical investigation into the settlement behavior of embankment constructed on geosynthetic-encased stone column installed in soft ground. A three-dimensional finite element model was employed to carry out a parametric study on a number of governing factors such as the thickness and consistency of soft ground, the geosynthetic encasement length and stiffness, the embankment fill height, and the area replacement ratio. It is shown among other things that unlike an isolated geosynthetic-encased stone column, full encasement of stone column is necessary to minimize the settlement for the embankment loading condition. Also revealed is that the efficiency of increasing encasement stiffness is construction condition dependent and is maximized for cases with which the stress intensity in the soft ground is larger. Based on the results of this investigation, design charts for use in estimating the maximum settlement and the stress concentration ratio during preliminary design are presented. © 2015 Elsevier Ltd.

Ansari S.A.,Bhabha Atomic Research Center | Pathak P.,Bhabha Atomic Research Center | Mohapatra P.K.,Bhabha Atomic Research Center | Manchanda V.K.,Bhabha Atomic Research Center | Manchanda V.K.,Sungkyunkwan University
Chemical Reviews | Year: 2012

The historical perspective and recent advances on the fascinating chemistry of diglycolamides, with special emphasis on their proposed applications in radioactive waste management, is presented. Stephan et al. studied the extraction of various metal ions with multidentate amido podands. The open-chain ether dicarboxylic acid diamides (diglycolamides) exhibited very high D values for rare earth ions, viz. La(III) and Yb(III) from picrate and nitrate media at pH 5. Elsewhere, tripodal chelates bearing three DGA units precisely arranged on a triphenoxymethane platform were synthesized to mimic the preferred TTP geometry favored by lanthanides coordinating through oxygen donor atoms. Yaita et al. and Nave et al. reported the presence of N, N,N',N'-tetraoctyl diglycolamide (TODGA) aggregates dispersed in nonpolar diluents. Wilden et al. proposed a 1-cycle SANEX process for the direct selective extraction of trivalent actinides from a simulated PUREX raffinate using a mixture of CyMe4BTBP and TODGA.

Choi K.W.,Seoul National University of Science and Technology | Hossain E.,University of Manitoba | Kim D.I.,Sungkyunkwan University
IEEE Transactions on Wireless Communications | Year: 2011

We propose a novel cooperative spectrum sensing algorithm for a cognitive radio (CR) network to detect a primary user (PU) network that exhibits some degree of randomness in topology (e.g., due to mobility). We model the PU network as a random geometric network that can better describe small-scale mobile PUs. Based on this model, we formulate the random PU network detection problem in which the CR network detects the presence of a PU receiver within a given detection area. To address this problem, we propose a location-aware cooperative sensing algorithm that linearly combines multiple sensing results from secondary users (SUs) according to their geographical locations. In particular, we invoke the Fisher linear discriminant analysis to determine the linear coefficients for combining the sensing results. The simulation results show that the proposed sensing algorithm yields comparable performance to the optimal maximum likelihood (ML) detector and outperforms the existing ones, such as equal coefficient combining, OR-rule-based and AND-rule-based cooperative sensing algorithms, by a very wide margin. © 2011 IEEE.

Lee S.-K.,Sungkyunkwan University | Lee S.-K.,Yonsei University | Rana K.,Yonsei University | Ahn J.-H.,Yonsei University
Journal of Physical Chemistry Letters | Year: 2013

Graphene and its derivatives have been the subject of extensive research in fundamental science and have viable applications in current and future technology. The exceptionally high electronic and thermal conductivity, optical transparency, and high specific surface area, combined with excellent mechanical flexibility and environmental stability leave graphene poised to be a material of the future. This perspective introduces the importance of graphene electrodes, discusses the synthesis of graphene and transfer onto desired substrates and the role of graphene in electrodes for a broad range of flexible devices such as photovoltaic, electronic, and electrochemical energy storage. © 2013 American Chemical Society.

Lee J.,Pusan National University | Jo D.-G.,Sungkyunkwan University | Park D.,Pusan National University | Chung H.Y.,Pusan National University | And 2 more authors.
Pharmacological Reviews | Year: 2014

During the past 5 decades, it has been widely promulgated that the chemicals in plants that are good for health act as direct scavengers of free radicals. Here we review evidence that favors a different hypothesis for the health benefits of plant consumption, namely, that some phytochemicals exert disease-preventive and therapeutic actions by engaging one or more adaptive cellular response pathways in cells. The evolutionary basis for the latter mechanism is grounded in the fact that plants produce natural antifeedant/noxious chemicals that discourage insects and other organisms from eating them. However, in the amounts typically consumed by humans, the phyto-chemicals activate one or more conserved adaptive cellular stress response pathways and thereby enhance the ability of cells to resist injury and disease. Examples of such pathways include those involving the transcription factors nuclear factor erythroid 2-related factor 2, nuclear factor-kB, hypoxia-inducible factor 1a, peroxisome proliferator-activated receptor g, and forkhead box subgroup O, as well as the production and action of trophic factors and hormones. Trans-lational research to develop interventions that target these pathways may lead to new classes of therapeutic agents that act by stimulating adaptive stress response pathways to bolster endogenous defenses against tissue injury and disease. Because neurons are particularly sensitive to potentially noxious phytochemicals, we focus on the nervous system but also include findings from other cell types in which actions of phytochemicals on specific signal transduction pathways have been more thoroughly studied.

Lee J.-H.,Telecom Bretagne | Bonnin J.-M.,Telecom Bretagne | You I.,Korean Bible University | Chung T.-M.,Sungkyunkwan University
IEEE Transactions on Industrial Electronics | Year: 2013

IPv6 mobility management is one of the most challenging research topics for enabling mobility service in the forthcoming mobile wireless ecosystems. The Internet Engineering Task Force has been working for developing efficient IPv6 mobility management protocols. As a result, Mobile IPv6 and its extensions such as Fast Mobile IPv6 and Hierarchical Mobile IPv6 have been developed as host-based mobility management protocols. While the host-based mobility management protocols were being enhanced, the network-based mobility management protocols such as Proxy Mobile IPv6 (PMIPv6) and Fast Proxy Mobile IPv6 (FPMIPv6) have been standardized. In this paper, we analyze and compare existing IPv6 mobility management protocols including the recently standardized PMIPv6 and FPMIPv6. We identify each IPv6 mobility management protocol's characteristics and performance indicators by examining handover operations. Then, we analyze the performance of the IPv6 mobility management protocols in terms of handover latency, handover blocking probability, and packet loss. Through the conducted numerical results, we summarize considerations for handover performance. © 2012 IEEE.

Shin D.-H.,Sungkyunkwan University
International Journal of Mobile Communications | Year: 2010

This study presents a case analysis of a socio-technical framework used to assess the development of 4th generation mobile technology in Korea. Using Actor Network Theory (ANT), this study develops a rich understanding of how 4G will evolve and stabilise in next-generation network environments. ANT provides a framework of ideas for describing the process of technology adoption and for developing stories that explain it. An interpretive case study investigates the complex interaction between the social and technical aspects of 4G by highlighting the co-evolving nature, diversity, and interface that constitute the next-generation network environment. It provides insight into the Korean mobile environment by offering a socio-technical analysis of 4G development and how it involves the dynamics of industry, regulation, and technology. The use of ANT as a framework of analysis reveals a unique set of socio-technical problems, challenges, and opportunities in 4G technology. Copyright © 2010 Inderscience Enterprises Ltd.

Bae S.Y.,Sungkyunkwan University
Clinical and molecular hepatology | Year: 2012

We compared the accuracy and usefulness of clinical diagnostic criteria for hepatocellular carcinoma in a hepatitis B virus (HBV)-endemic area. We reviewed the medical records of 355 patients who had undergone liver resection or biopsy at our institution between January 2008 and December 2009. These patients were reevaluated using four noninvasive diagnostic criteria for hepatocellular carcinoma proposed by the European Association for the Study of the Liver (EASL), the American Association for the Study of Liver Diseases (AASLD), the Korean Liver Cancer Study Group and the National Cancer Center (KLCSG/NCC), and National Comprehensive Cancer Network (NCCN) guidelines. The overall sensitivity was highest using the KLCSG/NCC criteria (79.8%), followed by the AASLD (51.5%), EASL (38.4%), and NCCN (10.1%; P<0.001) criteria, whereas the specificity (84.5-98.3%) and positive predictive value (96.2-98.3%) were similar for all of the criteria. The KLCSG/NCC criteria had an acceptable false-positive rate and the highest sensitivity among all of the patients, including those positive for HBsAg, those without liver cancer, and those with a tumor of at least 2 cm. The KLCSG/NCC and AASLD criteria exhibited the highest sensitivity, and all four guidelines had a high specificity among all of the patients. Based on the sensitivity and false-positive rate, the KLCSG/NCC criteria was the most useful in the majority of patients. Inclusion of HBV infection in the clinical diagnostic criteria for hepatocellular carcinoma would be reasonable and may lead to an improvement in the sensitivity, with acceptable false-positive rates, in HBV-endemic areas.

Yoon J.H.,Sungkyunkwan University
International psychogeriatrics / IPA | Year: 2011

Agraphia in Korean patients may be different from agraphia in other patients who use alphabetical writing systems due to the "visuoconstructional script" characteristics of the Korean writing system, Hangul. Patients with early onset Alzheimer's disease (EOAD) have a severe degree of hypometabolism in the parietal area, which is known to be involved in processing visuospatial function. Thus, we explored the diverse error patterns manifested in writing single syllables in Korean patients with EOAD. A study sample of 35 patients with EOAD and 18 healthy controls (HC) performed a Hangul writing task. We analyzed the erroneous responses of the subjects according to visuoconstructional and linguistic characteristics. In addition, we evaluated the relationship between Hangul writing and the neuropsychological variables as well as the severity of dementia. When comparing the total number of erroneous responses between EOAD and HC groups, the performances of EOAD patients were significantly worse than those of HC. EOAD patients demonstrated visuoconstructional errors even in the early stages of the disease. Severity of dementia and multiple cognitive domains such as attention, language, immediate memory, and frontal executive functions significantly correlated with the performance of Hangul writing. Our findings suggest that patients with EOAD exhibit not only linguistic errors but also visuoconstructional manifestations of agraphia, which are associated with cognitive impairments in the multiple domains.

Kim J.H.,Sungkyunkwan University
Tumour biology : the journal of the International Society for Oncodevelopmental Biology and Medicine | Year: 2010

Lymph node (LN) metastasis is one of the most important adverse prognostic factors for pancreatic cancer. The aim of this study was to identify novel lymphatic metastasis-associated markers for pancreatic cancer. DNA microarray analysis was used to determine and compare the expression profiles of 17 pancreatic cancer tissues with LN metastasis and 17 pancreatic cancer tissues without LN metastasis. The microarray results were validated by real-time reverse transcription-polymerase chain reaction and immunohistochemistry. Only 58 genes were differentially expressed between the two groups with a difference in signal intensity ratio greater than a 1.5-fold change. Of these genes, 30 were significantly down-regulated in the LN metastasis group. Among five selected down-regulated genes for validation using real-time PCR, the expression of DST, FosB, RGS16, and CXCL12 was significantly lower in the LN metastasis group. Immunohistochemical analysis confirmed RGS16 and FosB underexpression in pancreatic cancer tissues with LN metastasis. RGS16 and FosB underexpression was associated with poor patient survival. Our findings show that RGS16 and FosB are underexpressed in pancreatic cancer with lymph node metastasis and associated with reduced survival, suggesting that RGS16 and FosB might be prognostic markers for pancreatic cancer.

Revision surgery in patients showing polyethylene wear and acetabular osteolysis without visible acetabular cup loosening involves the difficult decision of whether to revise only the liner or both the cup and the liner. The purpose of this study is to compare the outcomes of complete acetabular revision and isolated liner exchange in patients showing wear and osteolysis without loosening. We evaluated 80 cases of revision surgery for polyethylene wear and osteolysis without cup loosening performed between October 1997 and December 2008. The cup revision group consisted of 45 patients who underwent a complete acetabular cup replacement, and the cup retention group consisted of 35 patients who underwent either an isolated liner exchange or a liner cementing procedure. Comparisons between the two groups were performed. There were differences in femoral stem revision, estimated blood loss, and hospital stay. Other variables including complications, osteolysis progression, re-revision rate, clinical score, and satisfaction showed no differences between the two groups. There was one case of early loosening and subsequent re-revision surgery in the cup revision group, as well as one case of wear progression and liner dislodgement leading to complete re-revision of the acetabular component and femoral stem in the cup retention group. We found no differences in acetabular osteolysis progression, fixation failure, or complication between the cup revision and retention groups. Therefore, isolated liner exchange without cup extraction in cases of osteolysis that includes a well-fixed and well-positioned shell could be considered as a viable treatment option.

Sochichiu C.,Sungkyunkwan University
Journal of Physics A: Mathematical and Theoretical | Year: 2013

We study the emergence of a Dirac fermionic field in the low energy description of non-relativistic dynamical models on graphs admitting a continuum limit. The Dirac fermionic field appears as the effective field describing the excitations above a point-like Fermi surface. Together with the Dirac fermionic field an effective space-time metric also emerges. We analyze the conditions for such Fermi points to appear in general, paying special attention to the cases of two and three spatial dimensions. © 2013 IOP Publishing Ltd.

Chang Y.B.,Sungkyunkwan University | Gurbaxani V.,University of California at Irvine
Information Systems Research | Year: 2013

We analyze the impact of information technology (IT) on the technical efficiency of firms in the context of their observed competitive settings. Because competition can be a driver of efficiency and industries display varying degrees of competitiveness, firm-level efficiency is likely to display considerable heterogeneity. To shed light on these questions, we analyze the economic impact of IT on technical efficiency, a key component of efficiency, in heterogeneous competitive settings. Our study employs a number of econometric techniques, including a stochastic frontier and a generalized method of moments approach, on data from firms in a wide cross-section of industries. We find, after controlling for firm-level heterogeneity and potential endogeneity, that IT is positively associated with gains in technical efficiency but its impact is moderated by the degree of competition. Firms display large variation in their levels of technical efficiency partly because of the heterogeneous market competitiveness conditions they face. In more competitive industries, firms tend to deploy IT more intensively and use it more efficiently. Our study makes a distinct contribution relative to prior studies that have focused on the productivity impacts of IT while assuming perfect competition and not allowing for potential heterogeneity in firm-level efficiency. Overall, our results demonstrate that IT and competition are significant determinants of gains in technical efficiency and provide insight into how competition affects the returns to IT investment. © 2013 Informs.

Choi H.,Samsung | Kim J.,Sungkyunkwan University
Magazine of Concrete Research | Year: 2011

Experiments were carried out to investigate the progressive collapse-resisting capacity of reinforced concrete beam-column sub-assemblages designed with and without seismic load. The two-span sub-assemblages were designed as part of five- and eight-storey reinforced concrete moment-resisting frames. The exterior columns of the right-hand girders were designed to be 1.5 times larger in size than the middle columns to take into account continuation of the girder. A monotonically increasing load was applied at the middle column of the specimens and force-displacement relationships were plotted. It was observed that the non-seismically designed specimen failed by crushing of concrete at the exterior column-girder joint of the left-hand girder before catenary action was activated. However, the force-displacement relationship of the specimen designed for seismic load kept increasing after fracture of the girder lower rebars near the middle column due to the catenary force of the upper rebars. Based on the test results it was concluded that significant catenary action of girders could be induced in reinforced concrete moment-resisting buildings designed as per current seismic design codes against progressive collapse initiated by sudden loss of a column.

Oh S.-Y.,Sungkyunkwan University
Journal of the Korean Medical Association | Year: 2016

Despite low childbirth rate in Korea, the number of women with high-risk pregnancies is steadily increasing, mostly due to increased maternal age, multiple pregnancies, and obesity. In fact, one out of five Korean women is above 35 years old at childbirth. It is well known that high risk pregnancy is closely related with increased maternal mortality, either by direct or indirect causes. Despite such problems, however, Korea's health care infrastructure for childbirth has deteriorated, leaving approximately 20% of the geographic area of the country medically underserved with regard to optimal maternity care. Such a collapse has been caused by the decrease in the number of maternity hospitals and their financial difficulties due to medical fee reimbursement for childbirth being too low. The problem is aggravated by a lack of obstetricians who can provide skilled attendance at childbirth. In addition, extensive legal pressure has dissuaded talented medical students from pursuing obstetrics and gynecology, thereby resulting in aging and severe gender imbalance in such professions. The direct consequence of the collapse in infrastructure for childbirth is an increased maternal mortality ratio, especially in underserved areas. Moreover, increased maternal death caused by postpartum bleeding reflects an obvious sign of danger in the maternal health care system. Furthermore, the number of tertiary hospitals that can provide optimal care to high risk pregnant women has decreased to two-thirds of what it once was, and the training of competent obstetricians for the mothers of the future continues to be a difficulty. © 2016 Korean Medical Association.

Lee W.J.,Sungkyunkwan University
The Korean journal of hepatology | Year: 2011

Hepatic hydrothorax in patients with decompensated liver cirrhosis is a challenging problem. Treatment with diuretics and intermittent thoracentesis can be effective in selected patients. However, there are few effective therapeutic options in patients who are intolerant of these therapies. This study investigated the clinical usefulness of chemical pleurodesis with or without video-assisted thoracoscopic surgery (VATS) for patients with refractory hepatic hydrothorax. Eleven consecutive patients with refractory hepatic hydrothorax who underwent chemical pleurodesis with or without VATS between July 2007 and February 2011 were enrolled in this study. The medical records and radiologic imagings of these patients were thoroughly reviewed. The median number of chemical pleurodesis sessions performed was 3 (range: 2-10). Successful pleurodesis was achieved in 8 of the 11 patients (72.7%), 5 (62.5%) of whom remained asymptomatic and hydrothorax free for a median follow-up of 16 weeks (range: 2-52 weeks). Complications were low-grade fever/leukocytosis (n=11, 100%), pneumonia (n=1, 9.1%), pneumothorax (n=4, 36.4%), azotemia/acute renal failure (n=6, 54.6%), and hepatic encephalopathy (n=4, 36.4%). Five patients were suspected as having procedure-related mortality (45.5%) due to the occurrence of acute renal failure with hepatic failure. The overall survival was significantly longer in the success group than in the non-success group. Although chemical pleurodesis may improve the clinical symptoms and the radiologic findings in as many as 72.7% of patients with refractory hepatic hydrothorax, a significantly high prevalence of procedure-related morbidity and mortality hinders the routine application of this procedure for such patients.

Cho D.H.,Sungkyunkwan University
The Korean journal of gastroenterology = Taehan Sohwagi Hakhoe chi | Year: 2011

As the population ages, endoscopic retrograde cholangiopancreaticography (ERCP) is being used increasingly as a diagnostic and therapeutic tool for elderly patients with pancreatobiliary disease. The aim of this study was to assess the outcomes, safety and complications associated with ERCP performed in the elderly patients. We retrospectively reviewed the medical record of 596 patients who were 50 years of age or older and underwent ERCP from January 2005 to September 2010. The patients were classified into two groups according to the age: non-elderly, 50-74 years old and elderly, ≥75 years old. Comparisons were made between two groups. Five hundred and ninety-six patients (132 elderly and 464 non-elderly patients) were enrolled. The success rate of ERCP was 89.4% in the elderly and 91.9% in the non-elderly. The major complications were occurred in 11 patients of the elderly and 16 of the non-elderly, and the complication rate was significantly higher in the elderly compared to the non-elderly (8.3% vs. 3.4%, p=0.011). Pancreatitis occurred in 2 elderly patients and 10 non-elderly patients (1.5% vs. 2.1%, p=1.0). There was a higher rate of bleeding in the elderly patients (4.5% vs. 1.3%, p=0.01). ERCP is effective and safe even in elderly patients. Outcomes of diagnostic and therapeutic ERCP in the elderly patients were similar to those in non-elderly patients. Elderly patients undergoing ERCP carried similar risk of pancreatitis but a higher risk of bleeding and perforation compared to non-elderly patients.

Lee J.,Sungkyunkwan University
International Journal of Healthcare Information Systems and Informatics | Year: 2015

This paper investigates the factors affecting health information technology (IT) investment. Different from previous studies, health IT was measured as the dollar amount of hardware, software and labor related health IT. This study employed Hospital and Patient level data of the Office of Statewide Health Planning and Development (OSHPD) from 2000 to 2006. The generalized linear model (GLM) was employed with log link and normal distribution and controlled for clustering error. This study found that not-for-profit and government hospital, teaching hospitals, competition, health IT expenditure of neighborhood hospitals were positively associated with health IT expenditure. However, rural hospitals were negatively associated with health IT expenditure. Moreover, this study found a significant increase in health IT investment over seven years re sulted from increased clinical IT adoption. Copyright © 2015, IGI Global.

Sun H.,Sungkyunkwan University
Bulletin of the Korean Chemical Society | Year: 2011

Based on the exact quantization rule for the nonrelativistic Schrödinger equation, the exact quantization rule for the relativistic one-dimensional Klein-Gordon equation is suggested. Using the new quantization rule, the exact relativistic energies for exactly solvable potentials, e.g. harmonic oscillator, Morse, and Rosen-Morse II type potentials, are obtained. Consequently the new quantization rule is found to be exact for one-dimensional spinless relativistic quantum systems. Though the physical meanings of the new quantization rule have not been fully understood yet, the present formal derivation scheme may shed light on understanding relativistic quantum systems more deeply.

Lee K.-T.,Sungkyunkwan University
Plastic and Reconstructive Surgery | Year: 2016

BACKGROUND: The present study evaluated donor morbidities following the free TDAP flap harvest comprehensively and investigated patient- and operation-related factors that might contribute to adverse outcomes. METHODS: A retrospective analysis was performed for all cases of free TDAP flap reconstructions between January 2002 and December 2014. Donor morbidity was evaluated in three aspects; postoperative complications, scar-related problems, and functional impairment. The Quick-Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire was conducted postoperatively to assess donor site function. RESULTS: A total of 293 patients were analyzed. Median follow-up period was 19.0 months. Donor site complications developed in 33 patients (11.3%). Wound dehiscence (7.4%) and seroma (3.0%) were the two most common complications. Harvesting TDAP flaps on multiple perforators or segmental latissimus dorsi muscle-chimeric flaps increased the rate of seroma formation, however did not affect other donor morbidities significantly. Patient American Society of Anesthesiologist classification was a significant predictor for wound dehiscence and overall donor complications. Thirty-one patients (10.6%) had scar-related problems, including 18 hypertrophic and 13 widened scars. A transverse skin paddle design had a significant protective effect on developing scar-related problems, compared to the non-transverse design. The mean Quick-DASH score was 2.68 (range, 0–18.2) and 90 percent of patients scored less than 10. Flap dimensions were positively correlated with the Quick-DASH score. CONCLUSIONS: The present study suggests that the free TDAP flap is associated with low donor morbidity and minimal dysfunction. Careful consideration of patient condition and thoughtful planning could further minimize donor morbidity. ©2016American Society of Plastic Surgeons

Hamada Y.,Kyoto University | Kawai H.,Kyoto University | Oda K.-Y.,Osaka University | Park S.C.,Sungkyunkwan University
Physical Review Letters | Year: 2014

The observed value of the Higgs boson mass indicates that the Higgs potential becomes small and flat at the scale around 1017GeV. Having this fact in mind, we reconsider the Higgs inflation scenario proposed by Bezrukov and Shaposhnikov. It turns out that the nonminimal coupling ξ of the Higgs squared to the Ricci scalar can be smaller than 10. For example, ξ=7 corresponds to the tensor-to-scalar ratio r≃0.2, which is consistent with the recent observation by BICEP2. © 2014 American Physical Society.

Song D.,Sungkyunkwan University | Choi Y.-J.,University of Tokyo
Renewable and Sustainable Energy Reviews | Year: 2012

According to the International Energy Agency (IEA), the energy demand for the building sector constituted about 25.3% of the final energy use in South Korea. The energy demand for residential buildings counts for 50.3% of the building sector and has also increased by 2.9 percent every year. The Korean government has shifted focus and is now promoting energy efficiency within the building sector and has set long-term energy conservation goals. Despite these efforts to minimize building energy, the Korean government has changed the building regulation to allow remodeling of the balcony space as a living space. Remodeling the balcony space to become an indoor space means that a buffer space for the outdoor environment is lost, causing thermal discomfort and discomfort glare and moreover, increasing the heating and cooling energy demand in residential buildings. Also, it results in an increase in building energy demand in South Korea. In this study, the effect of the alteration of balcony space on the indoor thermal environment and the heating and cooling energy demand of residential buildings in Korea were investigated by field measurement and simulation. From the measurement results, the indoor temperature of the condition without a balcony was 0.8 °C lower than that with a balcony. The heating and cooling load of the unit without the balcony space was 39% and 22% higher, respectively, than that of the unit with the balcony space. This increase results in considerable energy loss in the national scale and the ratio will be 0.3% of the final energy use in Korea. Also, it represents about 1.3% of the final energy use within the building sector of Korea. © 2011 Elsevier Ltd. All rights reserved.

Neta B.,Naval Postgraduate School, Monterey | Chun C.,Sungkyunkwan University
Mathematics and Computers in Simulation | Year: 2014

There are very few optimal fourth order methods for solving nonlinear algebraic equations having roots of multiplicity m. Here we compare five such methods, two of which require the evaluation of the (m - 1)st root. The methods are usually compared by evaluating the computational efficiency and the efficiency index. In this paper all the methods have the same efficiency, since they are of the same order and use the same information. Frequently, comparisons of the various schemes are based on the number of iterations required for convergence, number of function evaluations, and/or amount of CPU time. If a particular algorithm does not converge or if it converges to a different solution, then that particular algorithm is thought to be inferior to the others. The primary flaw in this type of comparison is that the starting point represents only one of an infinite number of other choices. Here we use the basin of attraction idea to recommend the best fourth order method. The basin of attraction is a method to visually comprehend how an algorithm behaves as a function of the various starting points.

Kim M.-Y.,Soongsil University | Cho J.Y.,Sungkyunkwan University
Journal of Ginseng Research | Year: 2013

20S-dihydroprotopanaxadiol (2H-PPD) is a derivative of protopanaxadiol, a glycone of ginsenosides prepared from Panax ginseng. Although ginsenosides and acidic polysaccharides are known to be major active ingredients in ginseng, the immunopharmacological activities of their metabolites and derivatives have not been fully explored. In this study, we aimed to elucidate the regulatory action of 2H-PPD on the function of monocytes and macrophages in innate immune responses. 2H-PPD was able to boost the phagocytic uptake of fluorescein isothiocyanate-dextran in macrophages and enhance the generation of radicals (reactive oxygen species) in sodium nitroprusside-treated RAW264.7 cells. The surface levels of the costimulatory molecules such as CD80 and CD86 were also increased during 2H-PPD treatment. In addition, this compound boosted U937 cell-cell aggregation induced by CD29 and CD43 antibodies, but not by cell-extracellular matrix (fbronectin) adhesion. Similarly, the surface levels of CD29 and CD43 were increased by 2H-PPD exposure. Therefore, our results strongly suggest that 2H-PPD has the pharmacological capability to upregulate the functional role of macrophages/monocytes in innate immunity. © The Korean Society of Ginseng.

Kim M.-Y.,Soongsil University | Cho J.Y.,Sungkyunkwan University
Journal of Ginseng Research | Year: 2013

20S-dihydroprotopanaxatriol (2H-PPT) is a derivative of protopanaxatrol from ginseng. Unlike other components from Panax ginseng, the pharmacological activity of this compound has not been fully elucidated. In this study, we investigated the modulatory activity of 2H-PPT on the cellular responses of monocytes and macrophages to understand its immunoregulatory actions. 2H-PPT strongly upregulated the release of radicals in sodium nitroprusside-treated RAW264.7 cells and the surface levels of costimulatory molecule CD86. More importantly, this compound remarkably suppressed nitric oxide production, morphological changes, phagocytic uptake, cell-cell aggregation, and cell-matrix adhesion in RAW264.7 and U937 cells in the presence or absence of lipopolysaccharide, anti-CD43 antibody, fibronectin, and phorbal 12-myristate 13-acetate. Therefore, our results suggest that 2H-PPT can be applied as a novel functional immunoregulator of macrophages and monocytes. © The Korean Society of Ginseng.

Kang H.,Sungkyunkwan University
Molecules and cells | Year: 2013

Cdc25B is an essential regulator for meiotic resumption in mouse oocytes. However, the role of this phosphatase during the later stage of the meiotic cell cycle is not known. In this study, we investigated the role of Cdc25B during metaphase II (MII) arrest in mouse oocytes. Cdc25B was extensively phosphorylated during MII arrest with an increase in the phosphatase activity toward Cdk1. Downregulation of Cdc25B by antibody injection induced the formation of a pronucleus-like structure. Conversely, overexpression of Cdc25B inhibited Ca(2+)-mediated release from MII arrest. Moreover, Cdc25B was immediately dephosphorylated and hence inactivated during MII exit, suggesting that Cdk1 phosphorylation is required to exit from MII arrest. Interestingly, this inactivation occurred prior to cyclin B degradation. Taken together, our data demonstrate that MII arrest in mouse oocytes is tightly regulated not only by the proteolytic degradation of cyclin B but also by dynamic phosphorylation of Cdk1.

Park N.-G.,Sungkyunkwan University
Journal of Physical Chemistry Letters | Year: 2013

Recently, perovskite CH3NH3PbI3 sensitizer has attracted great attention due to its superb light-harvesting characteristics. Organometallic or organic materials were mostly used as sensitizers for solid-state dye-sensitized solar cells at early stages. Inorganic nanocrystals have lately received attention as light harvesters due to their high light-absorbing properties. Metal chalcogenides have been investigated with solid-state dye-sensitized solar cells; however, the best power conversion efficiency was reported to be around 6%. CH3NH 3PbX3 (X = Cl, Br, or I) perovskite sensitizer made a breakthrough in solid-state mescoscopic solar cells, where the first record efficiency of around 10% was reported in 2012 using submicrometer-thick TiO 2 film sensitized with CH3NH3PbI3. A rapid increase in efficiency approaching 14% followed shortly. In this Perspective, recent progress in perovskite-sensitized solid-state mesoscopic solar cells is reviewed. On the basis of the recent achievements, a power conversion efficiency as high as 20% is expected based on optimized perovskite-based solid-state solar cells. © 2013 American Chemical Society.

Kim Y.S.,Sungkyunkwan University
Energy Economics | Year: 2015

This paper studies the dynamic behavior of electricity consumption with special emphasis on their convergence patterns. Individual electricity indicators are modeled by allowing for apparent heterogeneous transitions. Log t convergence test results indicate that all 109 countries converge to a common stochastic trend for electricity intensity while per capita electricity consumption is better explained by a multiple-component model. In the case of 24 advanced economies, there is a strong tendency towards a common component for both indicators. The application of clustering algorithm confirms the presence of club convergence for per capita electricity consumption. In terms of clustering pattern, per capita electricity consumption appears to be remarkably similar to per capita income, widely used measure of economic development. © 2015 Elsevier B.V.

Ju S.,Malgeun Child Counseling Center | Lee Y.,Sungkyunkwan University
Child Abuse and Neglect | Year: 2010

Objective: The objective of this study is twofold. The first objective is to explore the extent of family maltreatment experiences of children in protective care in South Korea. The second objective is to analyze the circumstances around the maltreatment and to obtain a better understanding of how maltreated children deal with the experience. Methods: Quantitative data were collected from face-to-face interviews with 357 children aged between 9 and 12, living in protective care as a result of maltreatment. Among these children, qualitative data were collected from 14 children who experienced serious maltreatment using in-depth interviews. Results: The results showed that, to a large extent, physical abuse very often occurred alongside emotional abuse. Most offenders were biological parents, who tended to be poor and have problems with alcohol. The majority of children in protective care were preschoolers. While in care, 40% of the children did not have any contact with their family for over a year. The results of the qualitative analysis of this study demonstrated that the abuse had multiple and long-term effects. Conclusions: This study confirms that many children living in Child Protective Services (CPS) have been abandoned by their families; moreover, they tend to lead highly unstable lives characterized by a vicious circle of being referred to protective care, returning to their families, experiencing a second round of abuse, then being readmitted to care. Practical implications: This study emphasizes the need for communities to provide safe social support networks that can assist children who are victims of maltreatment to recover and readjust positively. It further suggests the need for a comprehensive holistic approach which takes the best interest of the child into primary consideration. © 2009 Elsevier Ltd. All rights reserved.

Lee J.H.,Sungkyunkwan University
Korean journal of ophthalmology : KJO | Year: 2012

A 43-year-old man developed decreased vision in the right eye that had persisted for seven years. Under slit lamp examination, corneal clouding was noted with normal endothelium and ocular structure. From the clinical evidence, we suspected that the patient had congenital hereditary stromal dystrophy (CHSD). He and his family underwent a genetic analysis. Penetrating keratoplasty was conducted, and the corneal button was investigated for histopathologic confirmation via both light and electron microscopy. The histopathologic results revealed mildly loosened stromal structures, which exhibited an almost normal arrangement and differed slightly from the previous findings of CHSD cases. With regard to the genetic aspects, the patient and his mother harbored a novel point mutation of the decorin gene. This genetic mutation is also distinct from previously described deletion mutations of the decorin gene. This case involved delayed penetration of mild clinical symptoms with the histological feature of a loosened fiber arrangement in the corneal stroma. We concluded that this condition was a mild form of CHSD. However, from another perspective, this case could be considered as "decorin gene-associated corneal dystrophy," which is distinct from CHSD. Further evaluation will be required for appropriate clinical, histopathologic and genetic approaches for such cases.

To investigate the change of vasculature in the sentinel lymph node (SLN) of patients with oral squamous cell carcinoma. Immunohistochemical staining of SLNs in 58 patients was performed with two monoclonal antibodies (MAb): anti-D2-40 MAb for lymphatic endothelial cells, and anti-MECA-79 MAb for high endothelial venules (HEV). Twelve metastatically involved (m(+)) SLNs, 120 uninvolved (m(-)) SLNs, and 35 non-SLNs (control) were available for analyses. Vessel densities were measured by computer-assisted analyses in the entire region of SLN. Correlations were assessed between vessel density and clinicopathologic variables, including vascular endothelial growth factor C of primary tumor. Lymphatic vessel density (LVD) in SLNs was higher than that in control LNs [2361.8 μm(2)/high-power field (HPF) (624.3-4758.5) vs. 1621.9 μm(2)/HPF (465.3-3453.5), P = 0.005]. LVD of m(-) SLNs [2662.4 μm(2)/HPF (624.3-4758.5)] and m(±) SLNs [4946.6 μm(2)/HPF (2009.3-8698.8)] were both statistically significantly higher compared to control. HEV densities in m(-) SLNs [14029.7 μm(2)/HPF (10465.7-17927.1)] as well as m(±) SLNs [18258.5 μm(2)/HPF (8408.9-27706.0)] were also significantly higher than those in control [10350.5 μm(2)/HPF (7807.8-12541.1)]. By multivariate analysis, the degree of vascular endothelial growth factor C expression of primary tumor showed significant correlation with LVD of SLNs (odds ratio 9.46, 95% confidence interval 1.73-51.5, P = 0.009), which was not the case in HEV. Lymphatic vessels and HEVs were increased in SLNs, regardless of metastatic status of SLNs. Vascular endothelial growth factor C expression of primary tumor may contribute to the premetastatic change within SLNs of oral squamous cell carcinoma.

Yoo E.-H.,Kyung Hee University | Kim D.,Sungkyunkwan University
International Urogynecology Journal and Pelvic Floor Dysfunction | Year: 2013

Introduction and hypothesis: The study sought to identify the risk factors of postoperative use of antimuscarinics after transobturator surgery in women with mixed urinary incontinence (MUI) displaying both urodynamic stress urinary incontinence (SUI) and involuntary detrusor contraction (IDC) with leakage in urodynamic study. Methods: The clinical data of 103 patients with MUI who underwent transobturator tape (TOT) sling surgery were retrospectively reviewed. The patients were followed at least a year. To determine risk factors for postoperative use of antimuscarinics, variables of only those with P values < 0.05 on univariate analysis were included in the multivariate logistic regression analysis with forward stepwise building. Results: Eight-four (81.6 %) of 103 patients were included in this study. The cure rate of urge urinary incontinence (UUI) was 69.0 % (58/84). Antimuscarinics were prescribed postoperatively in 22 (26.2 %) of 84 patients. Variables affecting postoperative use of antimuscarinics were age, parity, episode of any UUI, preoperative use of antimuscarinics, predominant urgency incontinence type, detrusor pressure at maximum flow, and Urogenital Distress Inventory 6. Increasing age and preoperative use of antimuscarinics increased the odds of postoperative use of antimuscarinics following TOT surgery. Conclusion: Patients who were older and had taken antimuscarinics preoperatively were significantly associated with postoperative use of antimuscarinics. © 2012 The International Urogynecological Association.

Kim Y.-S.,Sungkyunkwan University
International Journal of Hyperthermia | Year: 2015

The clinical role of magnetic resonance image-guided high-intensity focused ultrasound (MR-HIFU) is rapidly expanding due to its merit of non-invasiveness. MR thermometry based on a proton resonance frequency shift technique is able to accurately measure HIFU-induced temperature changes, which provides considerable advantages over ultrasonography-guided HIFU in terms of safety and therapeutic efficacy. Recent studies and the resulting technological advances in MR-HIFU such as MR thermometry for moving organs, MR-acoustic radiation force imaging, and a volumetric mild hyperthermia technique further will expand its clinical roles from mere ablation therapy to targeted drug delivery and chemo-or radio-sensitisation for cancer treatment. In this article, MR-HIFU therapy is comprehensively reviewed with an emphasis on the roles of MR imaging in HIFU therapy, techniques of MR monitoring, recent advances in clinical MR-HIFU systems, and potential future applications of MR-HIFU therapy. In addition, the pros and cons of MR-HIFU when compared with ultrasonography-guided HIFU are discussed. © 2014 Informa UK Ltd. All rights reserved.

Kwon Y.-J.,Sungkyunkwan University
Journal of Korean Neurosurgical Society | Year: 2014

Objective: To report long-term clinical and radiological outcomes of minimally invasive posterior cervical foraminotomy (MI-PCF) performed in patients with unilateral single-level cervical radiculopathy.Methods: Of forty-six patients who underwent MI-PCF for unilateral single-level radiculopathy between 2005 and 2013, 33 patients were included in the study, with a mean follow-up of 32.7 months. Patients were regularly followed for clinical and radiological assessment. Clinical outcome was measured by visual analogue scale (VAS) for the neck/shoulder and arm, and the neck disability index (NDI). Radiological outcome was measured by focal/global angulation and disc height index (DHI). Outcomes after MI-PCF were evaluated as changes of clinical and radiological parameters from the baseline. Mixed effect model with random patients’ effect was used to test for differences in the clinical and radiological parameters repeat measures.Results: There were no complications and all patients had an uneventful recovery during the early postoperative period. VAS scores for neck/shoulder and arm improved significantly in the early postoperative period (3 months) and were maintained with time (p<0.001). NDI improved significantly post-operatively and tended to decrease gradually during the follow-up period (p<0.001). There were no statistically significant changes in focal and global angulation at follow-up. Percent DHIs of the upper adjacent or operated disc were maintained without significant changes with time. During the follow-up, same site recurrence was not noted and adjacent segment disease requiring additional surgery occurred in two patients (6%) on the contra-lateral side.Conclusion: MI-PCF provides long-term pain relief and functional restoration, accompanied by good long-term radiological outcome. © 2014 The Korean Neurosurgical Society.

The primary purpose of our study was to evaluate whether maintenance chemotherapy with paclitaxel/gemcitabine (PG) was superior to observation in improving progression-free survival (PFS) in patients with metastatic breast cancer (MBC) who achieved disease control with an initial six cycles of PG as their first-line treatment. The study was a prospective, randomized, multicenter, phase III trial. Patients MBC with who achieved disease control after six cycles of PG chemotherapy were randomly assigned to maintenance chemotherapy or observation until progression. Of 324 patients from 10 centers enrolled, 231 patients with MBC exhibited disease control (complete response + partial response + stable disease) with first-line PG and were randomly assigned to maintenance chemotherapy (n = 116) or observation (n = 115). The median age was 48 years (range, 28 to 76 years), median follow-up was 33 months, and median number of chemotherapy cycles in the maintenance group after random assignment was six. The median PFS time after random assignment was longer in the maintenance group than in the observation group (7.5 v 3.8 months, respectively; P = .026). The median overall survival (OS) time was longer in the maintenance group than in the observation group (32.3 v 23.5 months, respectively; P = .047). The rate of grade 3 or higher neutropenia after random assignment was higher in the maintenance group than in the observation group (61% v 0.9%, respectively; P < .001). In patients with MBC who achieved disease control with an initial six cycles of PG chemotherapy, maintenance PG chemotherapy resulted in better PFS and OS compared with observation.

This study investigated skin temperature, the nocturnal secretion of urinary 6-sulfatoxymelatonin (aMT-6s), and self-estimated sleep propensity in subjects living in a thermally neutral environment but wearing two types of clothing which provided different thermal insulation to the extremities. The experiment was conducted from 21:30 h on day 0 to 06:30 h on day 2 in an environmental chamber controlled at 24 ± 0.2 °C and a relative humidity of 50 ± 5%. Seven healthy female volunteers participated twice, while wearing "covering" or "exposing" types of clothing. The "covering" type of experimental clothing consisted of long-sleeved shirts, full-length trousers and socks (Type L, weighing 1042 g); the "exposing" type of clothing consisted of half-sleeved shirts and knee-length trousers (Type H, weighing 747 g). During nocturnal sleep (from 22:30 h to 06:30 h), all subjects were covered by two thin sheets made of 100% cotton. When wearing Type H clothing, the nocturnal fall of forehead skin temperature tended to be greater (p = 0.07) and hand skin temperature was significantly lower during time awake (p < 0.05) with a greater nocturnal increase (p < 0.05). The distal-to-proximal skin temperature gradient, DPG, (a measure of the process of thermal regulation) was significantly lower with Type H clothing during times awake and asleep (p < 0.01 and p < 0.05, respectively), but the increase of DPG during the sleep period was greater with Type H clothing (p < 0.01). Type H clothing was also associated with a significantly greater secretion of nocturnal urinary aMT-6s during the first half of sleep (p < 0.05). Sleeping Inventory tests indicated that the subjects with Type H clothing had better subjective scores for sleepiness, sleep initiation, and sleep maintenance (all p < 0.05), and slightly less worries (0.05 < p < 0.10). These results suggest that clothing type uncovering the extremities in a thermally neutral environment of 24 °C might induce a greater day-night variation in heat loss and a larger nocturnal increase in skin temperature in the distal regions and promote more sleepiness and a more rapid sleep onset via increased urinary aMT-6s secretion in the first half of sleep period. It is suggested that these changes might be related to the role of the sympathetic nervous system in thermoregulation and melatonin secretion. © 2013 Copyright Taylor and Francis Group, LLC.

We propose a possible way to simulate a hump structure in the optical scattering rate. The optical scattering rate of correlated charge carriers can be defined within an extended Drude model formalism. When some electron- and hole-doped copper oxide systems are in spin density or charge density wave phases they show hump structures in their optical scattering rates. The hump structures have not yet been simulated or clearly understood. We are able to simulate the hump structure by using a peak followed by a dip feature in the normalized density of states within a generalized Allen formalism. We observe that reversing the order of the dip and peak gives completely different features in the optical scattering rate; a peak-dip (dip-peak) results in a hump (a valley) in the scattering rate. We also obtain the real parts of the optical conductivity and reflectance spectra from the simulated optical scattering rate and compare them with published experimental spectra. From these comparisons we conclude that the peak-dip order can give the hump structure that is observed experimentally in copper oxide systems. Finally we fit two published optical spectra with our new model and discuss our results and the possible origin of the dip or peak features in the normalized density of states. © 2013 IOP Publishing Ltd.

Hong K.-S.,Pusan National University | Naseer N.,Pusan National University | Kim Y.-H.,Sungkyunkwan University
Neuroscience Letters | Year: 2015

Functional near-infrared spectroscopy (fNIRS) is an optical imaging method that can be used for a brain-computer interface (BCI). In the present study, we concurrently measure and discriminate fNIRS signals evoked by three different mental activities, that is, mental arithmetic (MA), right-hand motor imagery (RI), and left-hand motor imagery (LI). Ten healthy subjects were asked to perform the MA, RI, and LI during a 10. s task period. Using a continuous-wave NIRS system, signals were acquired concurrently from the prefrontal and the primary motor cortices. Multiclass linear discriminant analysis was utilized to classify MA vs. RI vs. LI with an average classification accuracy of 75.6% across the ten subjects, for a 2-7. s time window during the a 10. s task period. These results demonstrate the feasibility of implementing a three-class fNIRS-BCI using three different intentionally-generated cognitive tasks as inputs. © 2014 Elsevier Ireland Ltd.

Ryu C.,Sungkyunkwan University
Journal of the Air and Waste Management Association | Year: 2010

Energy from waste (EfW) for nonrecyclable wastes is a suitable method of waste management and is important for renewable energy production. South Korea currently recycles 57% of household waste and landfills 26%. The remaining 17% is incinerated, mainly for heat production. In this study, the potential for energy production and reduction of corresponding greenhouse gas (GHG) emissions from municipal solid waste (MSW) in Korea was estimated without accounting for the lifecycle impact of waste management. The properties of the MSW were established from data available in national-scale waste surveys and reports. The potential of EfW for GHG emission reduction was calculated considering (1) the direct release of anthropogenic carbon, nitrous oxide (N2O), and methane (CH4); and (2) the reduction in indirect GHG emissions by fossil fuel displacement. CH4 emissions from landfilling were also estimated from biogenic carbon in waste. Applying the resulting emission factors to various EfW cases suggests that the current level of GHG emissions is significant but can be substantially reduced by increased use of EfW. A net reduction in GHG emissions can be achieved only by EfW with combined heat and power (CHP). Copyright 2010 Air & Waste Management Association.

Hasan S.F.,Sungkyunkwan University
IEEE Potentials | Year: 2013

Ubiquitous and pervasive communication services have rapidly gained popularity over the last few years. The main objective of these services is to allow information exchange in all environments. While this information exchange conventionally takes place between hand-held devices carried by the end users, a similar information exchange between vehicles is being envisaged. Vehicular communication is becoming increasingly popular in both the research and development arenas due to its far-reaching benefits. In a nutshell, it is concerned with giving vehicles the ability to detect and convey information regarding different traffic incidents. Vehicles can send information messages either to other vehicles within close range or to the roadside base stations (BSs). This idea is not entirely new because it previously existed in the form of ?telematics.? Telematics deals with the use of telecommunications for the information exchange between remote objects. The term became known in the late 1970s but did not gain popularity because the enoromous size of communication devices was a serious limitation to their widespread use. However, with the recent developments in chip design and integrated systems, housing low-power, small-sized devices inside vehicles has become possible. Vehicular communication has now become a distinct possibility and is being looked at from research and development perspectives. © 1988-2012 IEEE.

Shih E.,Sungkyunkwan University
Journal of Product Innovation Management | Year: 2013

This study proposes a model of dynamic use diffusion that serves as a basis for investigating post-adoption technology-usage behavior. Dynamic use diffusion measures the extent to which technology usage has evolved since the time of adoption. Herein, antecedents and consequences of dynamic use diffusion are investigated. A large-scale, random sample survey was conducted in the United States, Sweden, and India on the use of Internet and computing technology. The survey results suggest that while the antecedents of dynamic use diffusion are similar across the three countries, the consequences are somewhat different for India. These differences can be attributed to the national cultural differences of India compared with the United States and Sweden with regard to power distance beliefs. © 2012 Product Development & Management Association.

Sacanna S.,New York University | Pine D.J.,New York University | Yi G.-R.,Sungkyunkwan University
Soft Matter | Year: 2013

This article investigates the role of shape in colloidal self-assembly and argues for the importance of a tight synergy between particle design and assembly strategies. To this end, we review synthetic methodologies developed to impart colloidal building blocks with anisotropic shapes and self-assembly mechanisms that exploit geometry to direct and control the particles' organization. This paper, which deliberately focuses on micron-scale colloids, is divided into two main sections. Firstly, we discuss the impact of shape on particles' interactions and how this has been exploited to develop heuristic rules for the creation of self-assembling architectures. Secondly, we examine state-of-the-art advances in colloidal synthesis with a clear emphasis on design rules and bulk methods, which are aimed at producing shape-anisotropic particles. © 2013 The Royal Society of Chemistry.

Oh T.H.,Sungkyunkwan University
Korean Journal of Urology | Year: 2012

Since the introduction of laparoscopic surgery, the promise of lower postoperative morbidity and improved cosmesis has been achieved. Laparoendoscopic single-site surgery (LESS) potentially takes this further. Following the first human urological LESS report in 2007, numerous case series have emerged, as well as comparative studies comparing LESS with standard laparoscopy. However, comparative series between conventional laparoscopy and LESS for different procedures suggest a non-inferiority of LESS over standard laparoscopy, but the only objective benefit remains an improved cosmetic outcome. Challenging ergonomics, instrument clashing, lack of true triangulation, and in-line vision are the main concerns with LESS surgery. Various new instruments have been designed, but only experienced laparoscopists and well-selected patients are pivotal for a successful LESS procedure. Robotic-assisted LESS procedures have been performed. The available robotic platform remains bulky, but development of instrumentation and application of robotic technology are expected to define the actual role of these techniques in minimally invasive urologic surgery. © The Korean Urological Association, 2012.

Hamer H.M.,Friedrich - Alexander - University, Erlangen - Nuremberg | Hong S.B.,Sungkyunkwan University
Epilepsia | Year: 2013

Patients with epilepsy caused by mid-grade and high-grade tumors do not usually undergo formal presurgical epilepsy evaluations before tumor resection. However, a minority of these patients may benefit significantly from just such a structured presurgical evaluation especially when seizure freedom or seizure reduction is a surgical aim in addition to total tumor resection. Typical cases comprise patients with multifocal tumors, tumors with bilateral extension, tumors over eloquent cortex, and the need for differentiation of spells of an uncertain nature, for example, epileptic versus psychogenic nonepileptic seizures. If they are epileptic, the definition of the epileptic lesion versus the epileptogenic zone and eloquent cortex can be another reason for monitoring. In addition to noninvasive recordings, invasive studies that use subdural or depths electrodes can be of special importance in these patients, leading to an exact delineation of the epileptogenic zone, usually extending beyond the epileptic lesion, and allow safe differentiation of epileptic from eloquent cortex. © 2013 International League Against Epilepsy.

Jang H.R.,Sungkyunkwan University | Rabb H.,Johns Hopkins University
Nature Reviews Nephrology | Year: 2015

Acute kidney injury (AKI) prolongs hospital stay and increases mortality in various clinical settings. Ischaemia-reperfusion injury (IRI), nephrotoxic agents and infection leading to sepsis are among the major causes of AKI. Inflammatory responses substantially contribute to the overall renal damage in AKI. Both innate and adaptive immune systems are involved in the inflammatory process occurring in post-ischaemic AKI. Proinflammatory damage-associated molecular patterns, hypoxia-inducible factors, adhesion molecules, dysfunction of the renal vascular endothelium, chemokines, cytokines and Toll-like receptors are involved in the activation and recruitment of immune cells into injured kidneys. Immune cells of both the innate and adaptive immune systems, such as neutrophils, dendritic cells, macrophages and lymphocytes contribute to the pathogenesis of renal injury after IRI, and some of their subpopulations also participate in the repair process. These immune cells are also involved in the pathogenesis of nephrotoxic AKI. Experimental studies of immune cells in AKI have resulted in improved understanding of the immune mechanisms underlying AKI and will be the foundation for development of novel diagnostic and therapeutic targets. This Review describes what is currently known about the function of the immune system in the pathogenesis and repair of ischaemic and nephrotoxic AKI. © 2015 Macmillan Publishers Limited. All rights reserved.

Kim H.M.,Sungkyunkwan University
Clinical and molecular hepatology | Year: 2013

The red-blood-cell distribution width (RDW) is a newly recognized risk marker in patients with cardiovascular disease, but its role in nonalcoholic fatty liver disease (NAFLD) has not been well defined. The aim of the present study was to determine the association between RDW values and the level of fibrosis in NAFLD according to BARD and FIB-4 scores. This study included 24,547 subjects who had been diagnosed with NAFLD based on abdominal ultrasonography and questionnaires about alcohol consumption. The degree of liver fibrosis was determined according to BARD and FIB-4 scores. The association between RDW values and the degree of fibrosis in NAFLD was analyzed retrospectively. After adjusting for age, hemoglobin level, mean corpuscular volume, history of hypertension, history of diabetes, and high-sensitivity C-reactive protein, the RDW values were 12.61±0.41% (mean±SD), 12.70±0.70%, 12.77±0.62%, 12.87±0.82%, and 13.25±0.90% for those with BARD scores of 0, 1, 2, 3, and 4, respectively, and 12.71±0.72%, 12.79±0.66%, and 13.23±1.52% for those with FIB-4 scores of <1.30, 1.31-2.66, and ≥2.67, respectively (P<0.05). The prevalence of advanced fibrosis (BARD score of 24 and FIB-4 score of ≥1.3) increased with the RDW [BARD score: 51.1% in quartile 1 (Q1) vs. 63.6% in Q4; FIB-4 score: 6.9% in Q1 vs. 10.5% in Q4; P<0.001]. After adjustments, the odds ratio of having advanced fibrosis for those in Q4 compared to Q1 were 1.76 (95%CI=1.55-2.00, P<0.001) relative to BARD score and 1.69 (95%CI=1.52-1.98, P<0.001) relative to FIB-4 score. Elevated RDW is independently associated with advanced fibrosis in NAFLD.

Lee J.,University of Wollongong | Sakthivel R.,Sungkyunkwan University
Pramana - Journal of Physics | Year: 2013

The two-dimensional nonlinear physical models and coupled nonlinear systems such as Maccari equations, Higgs equations and Schrödinger-KdV equations have been widely applied in many branches of physics. So, finding exact travelling wave solutions of such equations are very helpful in the theories and numerical studies. In this paper, the Kudryashov method is used to seek exact travelling wave solutions of such physical models. Further, three-dimensional plots of some of the solutions are also given to visualize the dynamics of the equations. The results reveal that the method is a very effective and powerful tool for solving nonlinear partial differential equations arising in mathematical physics. © Indian Academy of Sciences.

Brand S.,Korea Institute of Science and Technology | Kim J.,Sungkyunkwan University | Kim J.,Sungkyun Advanced Institute of Nano Technology SAINT
Energy | Year: 2015

Herein, α-cellulose, d-xylose, and lignin, which are major lignocellulosic biomass constituents, are subject to being liquefied in scEtOH (supercritical ethanol). Biomass conversion, biocrude yield, gas composition and energy content resulting from the liquefaction are analyzed. When cellulose is used, the biocrude yield increased significantly from 1.6 to 48.4wt% with an increase in temperature from 265 to 350°C, while the yields of biocrudes obtained from lignin (25.2-28.8wt%) and xylose (32.1-42.0wt%) do not change significantly with varying temperature. The chemical composition of the biocrudes obtained from the cellulose and xylose liquefaction in scEtOH significantly differ when compared to those of the biocrudes obtained from fast pyrolysis and hydrothermal liquefaction. The unique chemical species in the scEtOH-liquefied biocrude include long-chain esters/ethers (C5-C10), long-chain acids (C4-C9), and tetrahydrofurans, which could be due to the enhanced esterification and hydrogenation reactions in the scEtOH medium. Plausible reaction pathways of xylose liquefaction in scEtOH are proposed. © 2014.

The role of Wharton’s jelly-derived human mesenchymal stem cells (WJ-MSCs) in inhibiting muscle cell death has been elucidated in this study. Apoptosis induced by serum deprivation in mouse skeletal myoblast cell lines (C2C12) was significantly reduced when the cell lines were cocultured with WJ-MSCs. Antibody arrays indicated high levels of chemokine (C motif) ligand (XCL1) secretion by cocultured WJ-MSCs and XCL1 protein treatment resulted in complete inhibition of apoptosis in serum-starved C2C12 cells. Apoptosis of C2C12 cells and loss of differentiated C2C12 myotubes induced by lovastatin, another muscle cell death inducer, was also inhibited by XCL1 treatment. However, XCL1 treatment did not inhibit apoptosis of cell lines other than C2C12. When XCL1-siRNA pretreated WJ-MSCs were cocultured with serum-starved C2C12 cells, apoptosis was not inhibited, thus confirming that XCL1 is a key factor in preventing C2C12 cell apoptosis. We demonstrated the therapeutic effect of XCL1 on the zebrafish myopathy model, generated by knock down of a causative gene ADSSL1. Furthermore, the treatment of XCL1 resulted in significant recovery of the zebrafish skeletal muscle defects. These results suggest that human WJ-MSCs and XCL1 protein may act as promising and novel therapeutic agents for treatment of myopathies and other skeletal muscle diseases.Molecular Therapy (2016); doi:10.1038/mt.2016.125. © 2016 American Society of Gene & Cell Therapy

Kong M.,Sungkyunkwan University
Korean journal of ophthalmology : KJO | Year: 2012

To investigate the advantages of ultrawide-field fluorescein angiography (FA) over the standard fundus examination in the evaluation of diabetic retinopathy (DR). Ultrawide-field FAs were obtained in 118 eyes of 59 diabetic patients; 11 eyes with no DR, 71 eyes with nonproliferative diabetic retinopathy (NPDR), and 36 eyes with proliferative diabetic retinopathy (PDR), diagnosed by the standard method. The presence of peripheral abnormal lesions beyond the standard seven fields was examined. Ultrawide-field FA images demonstrated peripheral microaneurysms in six (54.5%) of 11 eyes with no DR and all eyes with moderate to severe NPDR and PDR. Peripheral retinal neovascularizations were detected in three (4.2%) of 71 eyes with NPDR and in 13 (36.1%) of 36 eyes with PDR. Peripheral vascular nonperfusion and vascular leakage were found in two-thirds of eyes with severe NPDR and PDR. Ultrawide-field FA demonstrates peripheral lesions beyond standard fields, which can allow early detection and a close evaluation of DR.

Lee M.Y.,Chung - Ang University | Ham D.-I.,Sungkyunkwan University
Retina | Year: 2014

Purpose: To characterize a variant type of drusenoid deposit with different imaging features in comparison to reticular pseudodrusen. Methods: Retrospective observational consecutive case series. Eyes showing atypical drusenoid lesions were sorted out from 257 eyes of 133 patients previously diagnosed as reticular pseudodrusen. Eyes were evaluated using color fundus photography, confocal scanning laser ophthalmoscopy, and spectral domain optical coherence tomography. Results: A variant type of drusenoid deposits showing different imaging features from reticular pseudodrusen was found in 17 eyes of 12 patients (6.6%). The mean age of patients was 62.7 ± 11.6 years, and all patients were women. These deposits were observed as yellowish white, round to oval lesions on color photographs, located under the sensory retina and above the retinal pigment epithelium on spectral domain optical coherence tomography similar to reticular pseudodrusen. However, they were present in a smaller number as discrete lesions and showed increased autofluorescence. None of them were accompanied by late age-related macular degeneration. Conclusion: Subretinal drusenoid deposits are not homogeneous and can be classified into two types according to the fundus autofluorescence. Multimodal imaging tests are needed for the differential diagnosis of subretinal drusenoid deposits. Copyright © 2014 by Ophthalmic Communications Society, Inc.

Gastric cancer is the second leading cancer cause of death globally. Apart from the successful targeting of HER2 over-expression in gastric cancer (GC) with trastuzumab, other targeted therapies in GC have fallen short or still in early clinical development. While HER2 over-expression accounts for up to 20% of GC, other potential actionable driver mutations occur at a much lower frequency in GC. In this review we describe some of the more interesting genetic aberrations including driver mutations in gastric cancer that have very potent inhibitors against them already in clinical development. Part I of this review will concentrate on the receptor tyrosine kinase (RTK) gene amplification (HER2, FGFR2, MET, EGFR). Part II will concentrate on gene mutations (HER2, KRAS, PIK3CA, BRAF) and gene rearrangement (ROS1, BRAF, HER2). Because of the low frequency of these potential driver mutations, perseverance in screening for these mutations will be needed in order to enroll enough of each uniquely molecularly defined subset of GC in order to demonstrate significant clinical benefit in a unique molecularly targeted therapy trial. This approach has been successfully employed in the clinical approval of crizotinib for the treatment of ALK-rearranged non-small cell lung cancer. Finally, we discuss a paradigm shift in the personalized treatment of GC patients where multiplex comprehensive screening of all GC patients for all these potential driver mutations simultaneously is performed to achieve efficiencies and timeliness in diagnosis and allowing enrollment into different molecularly targeted therapy trials and the prospective discovery of novel yet unknown actionable driver mutations. © Discovery Medicine.

Park J.-C.,Korea Institute for Advanced Study | Park S.C.,Sungkyunkwan University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2013

In light of the recent observation of the Fermi-LAT 130 GeV gamma-ray line, we suggest a model of scalar dark matter in a hidden sector, which can decay into two (hidden) photons. The process is radiatively induced by a GUT scale fermion in the loop, which is charged under a hidden sector U(1), and the kinetic mixing (~εFμνF'μν) enables us to fit the required decay width for the Fermi-LAT peak. The model does not allow any dangerous decay channels into light standard model particles. © 2012 Elsevier B.V.

Prader-Willi syndrome (PWS) is a complex multisystem genetic disorder characterized by hypothalamic-pituitary dysfunction. The main clinical features include neonatal hypotonia, distinctive facial features, overall developmental delay, and poor growth in infancy, followed by overeating with severe obesity, short stature, and hypogonadism later in development. This paper reviews recent updates regarding the genetic aspects of this disorder. Three mechanisms (paternal deletion, maternal disomy, and deficient imprinting) are recognized. Maternal disomy can arise because of 4 possible mechanisms: trisomy rescue (TR), gamete complementation (GC), monosomy rescue (MR), and postfertilization mitotic nondisjunction (Mit). Recently, TR/GC caused by nondisjunction at maternal meiosis 1 has been identified increasingly, as a result of advanced maternal childbearing age in Korea. We verified that the d3 allele increases the responsiveness of the growth hormone (GH) receptor to endogenous GH. This paper also provides an overview of endocrine dysfunctions in children with PWS, including GH deficiency, obesity, sexual development, hypothyroidism, and adrenal insufficiency, as well as the effects of GH treatment. GH treatment coupled with a strictly controlled diet during early childhood may help to reduce obesity, improve neurodevelopment, and increase muscle mass. A more active approach to correct these hormone deficiencies would benefit patients with PWS. © 2012 by The Korean Pediatric Society.

Yun S.,Sungkyunkwan University
SIAM Journal on Optimization | Year: 2014

The cyclic (block) coordinate gradient descent method is an optimization method that has attracted much interest in applications of applied mathematics, statistics, and engineering. Reasons for this include its simplicity, speed, and stability, as well as its competitive performance on separable nonsmooth convex minimization problems, whose objective function is the sum of a smooth function and a separable (and possibly nonsmooth) convex function, such as the l1-regularized linear least squares problem and the l1-regularized logistic regression problem. But very little is known about the worst case iteration complexity of the method for solving the separable nonsmooth convex minimization problem. We prove that the method terminates in O(1/∈) iterations with an ∈-optimal solution, or equivalently, the convergence rate for it is O(1/k), where k is the iteration counter, when the smooth function of the objective has a Lipschitz gradient. Also, the linear rate convergence of the method is proved when the objective is a strongly convex function having a Lipschitz gradient or when the smooth function of the objective is a composition of a strong convex function having a Lipschitz gradient with a linear function, the convex function of the objective is polyhedral, and there is a real number whose corresponding level set of the convex function contains the set of optimal solutions and is bounded. © 2014 Society for Industrial and Applied Mathematics.

Zhu X.,West Chester University | Mukhopadhyay S.K.,Sungkyunkwan University | Kurata H.,International School of Management
Journal of Engineering and Technology Management - JET-M | Year: 2012

Radio frequency identification (RFID) is an emerging technology that is increasingly being used in supply chain management. RFID technology plays an important role in supporting logistics and supply chain processes because of their ability to identify, trace and track information throughout the supply chain. The technology can provide suppliers, manufacturers, distributors and retailers precise real time information about the products. This accurate knowledge of the inventory would result in lower labor cost, simplified business processes and improved supply chain efficiency. If properly used, it has the potential to cut ordering lead time and cost on inventory control, increase the accuracy of inventory information, help avoid stockouts and boost the number of inventory turns. In this paper, we provide an overview of the current state of RFID applications in different industries and its impact on business operations. We provide extensive literature survey and develop a framework for future research areas in this field. © 2011 Elsevier B.V. All rights reserved.

Kim S.J.,Sungkyunkwan University
Korean journal of ophthalmology : KJO | Year: 2013

A pair of 19-year-old female identical twins was referred to our hospital with progressive visual loss. They exhibited bilateral chorioretinal atrophy involving the midperiphery on fundoscopy and fluorescein angiography. Bilateral visual field constriction was noted on dynamic Goldmann perimetry, and a markedly impaired response was observed on both photopic and scotopic electroretinograms. Cystoid macular edema was identified in both eyes on optical coherence tomography. Plasma levels of ornithine were elevated. Based on these observations, the patients were diagnosed with gyrate atrophy of the choroid and retina. The clinical diagnosis was confirmed by mutation analysis of the ornithine-δ-aminotransferase (OAT) gene. Patients were treated with a pyridoxine supplement (300 mg/day) and an arginine-restricted diet to lower plasma levels of ornithine, which were successfully reduced without progression of chorioretinal atrophy for 15 months. Our report describes the first case of gyrate atrophy in the Korean population diagnosed by OAT gene analysis and treated with vitamin B6 dietary supplementation.

Lee J.-S.,Sungkyunkwan University | Olafsson S.,Iowa State University
Information Sciences | Year: 2013

An important and challenging problem in data clustering is the determination of the best number of clusters. A variety of estimation methods has been proposed over the years to address this problem. Most of these methods depend on several nontrivial assumptions about the data structure; and such methods may thus fail to discover the true clusters in a dataset that does not satisfy those assumptions. We develop a new approach that takes as a starting point the simple and intuitive observation that close objects should fall within the same cluster, whereas distant ones should not. Based on this simple notion we utilize a new measurement of good clustering called disconnectivity as well as existing goodness measurements; and we embed these measures into a meta-learning approach for estimating the number of clusters. A simulation experiment based on 13 representative models and an application to real world datasets are conducted to show the effectiveness of the proposed method. © 2013 Elsevier Inc. All rights reserved.

Mak K.F.,Columbia University | He K.,Case Western Reserve University | Lee C.,Sungkyunkwan University | Lee G.H.,Columbia University | And 3 more authors.
Nature Materials | Year: 2013

Two-dimensional (2D) atomic crystals, such as graphene and transition-metal dichalcogenides, have emerged as a new class of materials with remarkable physical properties. In contrast to graphene, monolayer MoS 2 is a non-centrosymmetric material with a direct energy gap. Strong photoluminescence, a current on/off ratio exceeding 10 8 in field-effect transistors, and efficient valley and spin control by optical helicity have recently been demonstrated in this material. Here we report the spectroscopic identification in a monolayer MoS 2 field-effect transistor of tightly bound negative trions, a quasiparticle composed of two electrons and a hole. These quasiparticles, which can be optically created with valley and spin polarized holes, have no analogue in conventional semiconductors. They also possess a large binding energy (∼ 20 meV), rendering them significant even at room temperature. Our results open up possibilities both for fundamental studies of many-body interactions and for optoelectronic and valleytronic applications in 2D atomic crystals. © 2013 Macmillan Publishers Limited. All rights reserved.

Park S.-W.,Sungkyunkwan University
Diabetes and Metabolism Journal | Year: 2013

Polytopic transmembrane protein, Niemann-Pick C1-Like 1 (NPC1L1) is localized at the apical membrane of enterocytes and the canalicular membrane of hepatocytes. It mediates intestinal cholesterol absorption and prevents extensive loss of cholesterol by transporting biliary cholesterol into hepatocytes. NPC1L1 is a molecular target of ezetimibe, an agent for hypercholesterolemia. Recently, NPC1L1 inhibition has been shown to prevent metabolic disorders such as fatty liver disease, obesity, diabetes, and atherosclerosis. In this review, the identification and characterization of NPC1L1, NPC1L1-dependent cholesterol transport, the relationship with pathogenesis of metabolic disease and its newly introduced function for virus entry are discussed. © 2013 Korean Diabetes Association.

Kim H.Y.,KAIST | Lee H.M.,KAIST | Park J.-N.,Sungkyunkwan University
Journal of Physical Chemistry C | Year: 2010

We scrutinized the reaction mechanism of CO2 methanation catalyzed by a Pd-MgO/SiO2 catalyst. Density functional theory studies showed that MgO and Pd nanoparticles play completely different roles. We found that MgO initiates the reaction by binding a CO2 molecule, forming a magnesium carbonate species on the surface, and that a supply of atomic H is essential for further hydrogenation of magnesium carbonate to methane. A CO2temperature-programmed desorption study gives credence to our findings on the role of MgO. Our results confirm the bifunctional mechanism of CO2 methanation by a Pd-MgO/SiO2 catalyst. © 2010 American Chemical Society.

Han D.M.,Sungkyunkwan University
IEEE Transactions on Consumer Electronics | Year: 2011

Flash memory can be classified into NOR type and NAND type. The NOR type memories enables fast reading with byte level I/O is developed into memory for code storage such as ROM BIOS. The NAND type memories cheaper than NOR type and therefore more widely used to larger scale systems. This paper proposed the new file translation system by making a new file structure which can decrease write operations. This file structure reduced write operation frequency of flash memory in file system layer. We can reduced write operation rate because of a write operation rate can be improved the efficiency of file translation operations. Flash Translation Layer (FTL) is to mapping a logical data address to a physical data address in flash memory, its designed to realize erase policy of data in order to perform write operation. The FTL suggests fast erase algorithm reduced write operation through a new file system structure and FTL programming. In addition, we have made the oldest data clean algorithm and then, the most recent data maintained longest as a result of experiment that the recent applied program. In this result, Data tend to be implemented again through the concept of regional and time space which appears automatically when applied program is implemented. This work proves the efficiency of the file system of NAND type flash memories through experiments. Through experiment and realization of the Flash file system, this scheme proved the efficiency of NAND-type flash file system which is required in an embedded system. © 2006 IEEE.

Lee C.,Sungkyunkwan University | Frechette L.G.,Universite de Sherbrooke
Journal of Microelectromechanical Systems | Year: 2011

This paper presents the design approach for a microturbopump, which is the core component of a micro steam turbine power plant-on-a-chip that implements the Rankine thermodynamic cycle for micro power generation. The turbopump integrates components that are demonstrated for the first time at microscale, such as a four-stage radial planar type microturbine and a one-sided hydrostatic thrust bearing (TB) system, along with a spiral groove viscous pump, a partially grooved seal, and a hydrostatic journal bearing. This paper presents the analytical models developed for each component, including a flow resistance model for the TB and models based on lubrication theory for the pump and seal. They are integrated to enable the microsystem design by satisfying force and power balance conditions on the rotor. Considering our previous thermodynamic cycle analysis on the Rankine micro power generation system, which is aimed at generating a few watts of electric power for applications in portable electronics or waste energy harvesting, we have designed a centimeter-scale demo turbopump device delivering 4.7 W of turbine mechanical power and 71% of turbopump efficiency in order to demonstrate the effectiveness of the component design models and system design principles. Fabrication and testing of the microturbopump are presented in the second part of this two-part paper. © 2011 IEEE.

Jin G.,Chosun University | Kim G.,Sungkyunkwan University
Journal of Materials Chemistry B | Year: 2013

Various physical stimulations have been widely applied to tissue regenerative applications. In particular, for bone tissue regeneration, several experimental studies have reported that electric stimulation can enhance the mineral formation in cultured osteoblasts and even alter the pattern of gene expression, promoting bone tissue formation. However, to date, for rapid-prototyped polycaprolactone (PCL)-based composites of pure PCL and dispersed materials including carbon nanotubes and β-tricalcium phosphate (TCP), the effect of electric stimulation on various cellular activities has not been analyzed. Here, a sinusoidal AC electric field (55 ± 8 mV cm -1 and 60 Hz) between parallel electrodes was applied to three-dimensional scaffolds (pure PCL, PCL/CNT-0.2 wt%, and PCL/β-TCP-20 wt%) cultured with osteoblast-like cells (MG63) 30 min per day for 14 days. When exposed to electric stimulation, alkaline phosphatase and calcium mineralization were enhanced in all scaffolds, and the PCL/β-TCP scaffold in particular showed the highest improvement in bone mineralization compared with other scaffolds. In this work, we surmised that the improvement may have been due to chemical precipitation of the calcium ions from the PCL/β-TCP scaffolds. To evaluate the effect of the released calcium ions from the composite scaffold, we observed the cellular behavior (cellular contraction) of proliferated cells under electric stimulation. The results indicate that in addition to the applied electric field conditions, the scaffold materials are also an important parameter for successful electric stimulation. © 2013 The Royal Society of Chemistry.

Sivasankaran S.,University of Kuala Lumpur | Bhuvaneswari M.,Sungkyunkwan University
Numerical Heat Transfer; Part A: Applications | Year: 2013

A numerical study has been performed on buoyancy-induced convection in a square porous cavity. The vertical sidewalls of the cavity are maintained with sinusoidal temperature distribution. The finite volume method is used to numerically solve the nondimensional governing equations. The Brinkman Forchheimer extended Darcy model is used in the present study. The results are analyzed over a range of the amplitude ratio, phase deviation, porosity, and Grashof and Darcy numbers. It is found that the heat transfer rate is increased when increasing the amplitude ratio, porosity, and Darcy number. The nonuniform heating on both sidewalls provides higher heat transfer rate than the nonuniform heating of one wall. © 2013 Copyright Taylor and Francis Group, LLC.

Koh S.D.,University of Nevada, Reno | Rhee P.-L.,Sungkyunkwan University
Journal of Neurogastroenterology and Motility | Year: 2013

The gastrointestinal motility is regulated by extrinsic and intrinsic neural regulation. Intrinsic neural pathways are controlled by sensory input, inter-neuronal relay and motor output. Enteric motor neurons release many transmitters which affect post-junctional responses. Post-junctional responses can be excitatory and inhibitory depending on neurotransmitters. Excitatory neurotransmitters induce depolarization and contraction. In contrast, inhibitory neurotransmitters hyperpolarize and relaxe the gastrointestinal smooth muscle. Smooth muscle syncytium is composed of smooth muscle cells, interstitial cells of Cajal and platelet- derived growth factor receptor α-positive (PDGFRα+) cells (SIP syncytium). Specific expression of receptors and ion channels in these cells can be affected by neurotransmitters. In recent years, molecular reporter expression techniques are able to study the properties of ion channels and receptors in isolated specialized cells. In this review, we will discuss the mechanisms of ion channels to interpret the post-junctional responses in the gastrointestinal smooth muscles. © 2013 The Korean Society of Neurogastroenterology and Motility.

Kim E.G.,Sungkyunkwan University
Clinical and experimental medicine | Year: 2010

STAT6 transcription factor, which has been implicated in commitment to Th2, is known to be activated by IL-4 and IL-13. Accordingly, STAT6 is primarily responsible for the transcriptional effects of IL-4 and IL-13. STAT6-deficient mice are known to have defective IL-4-mediated functions, such as B cell proliferation, Th2 cell development and IgE secretion; therefore, they primarily contain the Th1 phenotype. However, the mechanism responsible for regulation of STAT6 expression transcriptionally and post-transcriptionally has yet to be elucidated. Here, we characterized the human STAT6 promoter gene and found that the transcriptional regulatory elements CCAAT and ATF were important for the STAT6 promoter activity. Direct sequencing analysis revealed that the 13 GT repeat allelic variation in noncoding exon 1 of the STAT6 gene appeared more frequently in 91 patients with asthma or rheumatoid arthritis than the 15 GT repeat variation, which is the dominant phenotype in healthy controls. However, it appears that this allelic variation did not affect the STAT6 transcriptional activity. Interestingly, treatment with a DNA methyltransferase inhibitor markedly increased the expression of STAT6 mRNA and protein in human primary T cells. In contrast, IFN-gamma treatment significantly repressed the STAT6 transcriptional activity. Therefore, the present study provides insight into the molecular basis of STAT6 expression, and in particular, demonstrates that STAT6 expression is associated with DNA hypermethylation rather than promoter polymorphisms or allelic variations.

Li Y.,Northwestern University | Kroger M.,ETH Zurich | Liu W.K.,Northwestern University | Liu W.K.,Sungkyunkwan University
Macromolecules | Year: 2012

Addition of nanoparticles into a polymer matrix can significantly alter its structure, dynamics as well as viscosity. In this paper, we study the structural, dynamical and viscous behaviors of polyethylene (PE) matrices under the influence of five differently shaped nanoparticles: buckyball, graphene, nanodiamond (ND), X-shaped and Y-shaped junctions, at fixed volume fraction (4 vol %). These nanoparticles have different surface-area-to-volume ratios, arranged as graphene, X-shaped junction, Y-shaped junction, buckyball, and ND, from the largest to the smallest. In turn, different interaction energies between nanoparticles and PE matrices are enabled according to their surface-area-to-volume ratios. The graphene sheet is expected to have the strongest interaction with the PE matrix in accord with its largest surface-area-to-volume ratio. The interaction between NDs and their PE matrix is the smallest, due to their truncated octahedron shapes and the smallest surface-area-to-volume ratio. However, the graphene sheets tend to aggregate at the PE melting temperature (450 K), lowering their interactions with the PE matrix. Because of this interplay, the interactions between nanoparticles and polymer matrices can be tailored through the shapes (also surface-area-to-volume ratios) of nanoparticles as well as their dispersions. The polymer chains are found to be densely packed around these nanoparticles in the range of 2 nm, except NDs, due to their strong interactions with PE matrices. Thus, these nanoparticles are found to be able to nucleate polymer entanglements around their surfaces and to increase the underlying entanglement densities of PE matrices. Both the polymer chain relaxation and anisotropic viscosity of PE nanocomposites are shown to be greatly affected by oriented nanoparticles. Our simulation results indicate that the surface-area-to-volume ratio of nanoparticles plays the dominated role in the structural, dynamical and viscous properties of PE nanocomposites. © 2012 American Chemical Society.

Kim N.-I.,Sungkyunkwan University
European Journal of Mechanics, A/Solids | Year: 2012

The thin-walled composite beams with channel-sections considering the effects of shear deformation and two-parameter elastic foundation are developed. The current composite beam element includes the transverse shear and the restrained warping induced shear deformation by using the first-order shear deformation beam theory. The governing equations and the force-displacement relations are derived from the principle of stationary value of total potential energy. By applying the power series expansions of displacement components to the simultaneous ordinary differential equations, the explicit expressions for displacement parameters are derived. Finally, the element stiffness matrix is determined using the force-displacement relations. To verify accuracy and superiority of the beam element developed herein, the numerical solutions are presented and compared with the results obtained from the isoparametric beam element based on the Lagrangian interpolation polynomials, the three-dimensional analysis results using shell elements of ABAQUS, and the solutions by other researchers. © 2012 Elsevier Masson SAS. All rights reserved.

Kwon Y.-J.,Sungkyunkwan University
Journal of Korean Medical Science | Year: 2013

This study was done to evaluate whether injections of resveratrol, a natural compound found in the skin of grapes, had anabolic effects on degenerated intervertebral discs in a rabbit model. Two non-continuous lumbar discs were punctured in rabbits to induce disc degeneration. Four weeks and 6 weeks after puncture, the rabbits were treated by injections with dimethylsulfoxide (DMSO) or resveratrol. At 4, 8, and 16 weeks after initial injection, rabbits were sacrificed and the spine was extracted for magnetic resonance image (MRI), mRNA expression, and histological staining. Resveratrol treatment resulted in stronger signal intensity in T2-weighted images. MRI grade showed significantly lower in the resveratrol group than the DMSO group (P = 0.039). In the resveratrol group, aggrecan gene expression was significantly increased than that in the DMSO group at 16 weeks after injection (P = 0.027). MMP-13 mRNA levels in the resveratrol group were significantly decreased than those in the DMSO group at 8 and 16 weeks (P = 0.006 and P = 0.048, respectively). In hematoxylin and eosin stain, resveratrol-treated discs showed the features of regeneration. Histologic grade revealed improvement in resveratrol-treated discs, compared with DMSO-treated discs (P = 0.024). These anabolic effects on degenerated discs indicate that resveratrol is a promising candidate for treatment of degenerative disc disease. © 2013 The Korean Academy of Medical Sciences.

Before endoscopic resection (ER), a considerable number of undifferentiated early gastric cancer (UD-EGC) cases were initially diagnosed as atypical glands, dysplasia, or differentiated EGC (D-EGC) based on forceps biopsy specimens. As UD-EGC carries a high risk of resection margin involvement, identifying the predictive factors for UD-EGC cases with histologic discrepancy (HD) is of clinical importance. To investigate the outcomes of ER for UD-EGC and to identify the predictive factors for UD-EGC with HD. Among 2,194 EGC lesions treated by ER, 59 lesions were finally diagnosed as UD-EGC and 50 UD-EGC cases showed HD. The demographic and endoscopic characteristics were compared between D-EGC and UD-EGC with HD, and the predictive factors for the latter were investigated among cases of forceps biopsy-based diagnosis of atypical glands, dysplasia, or D-EGC. UD-EGC showed significantly higher rate of lateral margin involvement compared to D-EGC (18.6 vs. 3.4%). Among the UD-EGC cases meeting the expanded criteria and not involving additional surgery, no local or extragastric tumor recurrence was observed during the median follow-up of 27.5 months. Multivariate analysis demonstrated that age (≤60 years), female gender, gastric body, flat or depressed type, and tumor size (>2 cm) were independent predictive factors for UD-EGC with HD among cases of forceps biopsy-based diagnosis of atypical glands, dysplasia, or D-EGC. For lesions with predictive factors for UD-EGC with HD, a circumferential mapping biopsy before ER or wide marking during ER could be considered to avoid the potential risk of incomplete resection.

Eom J.-B.,Samsung | Lee T.-J.,Sungkyunkwan University
IEEE Communications Letters | Year: 2010

Dynamic Framed-Slotted ALOHA (DFSA) is one of the most popular algorithms to resolve tag collision in RFID systems. In DFSA, it is widely known that the optimal performance is achieved when the frame size is equal to the number of tags. So, a reader dynamically adjusts the next frame size according to the current number of tags. Thus it is important to estimate the number of tags accurately. In this paper, we propose a novel tag estimation method for DFSA. We compare the performance of the proposed method with those of other existing methods. And, simulation results show that our scheme improves the accuracy of tag estimation and the speed of tag identification. © 2010 IEEE.

Tchoe Y.,Seoul National University | Han J.H.,Sungkyunkwan University | Han J.H.,Pohang University of Science and Technology
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

Skyrmions, once a hypothesized field-theoretical object believed to describe the nature of elementary particles, became common sightings in recent years among several noncentrosymmetric metallic ferromagnets. For more practical applications of Skyrmionic matter as a carrier of information, thus realizing the prospect of "Skyrmionics," it is necessary to have the means to create and manipulate Skyrmions individually. We show through extensive simulation of the Landau-Lifshitz-Gilbert equation that a circulating current imparted to the metallic chiral ferromagnetic system can create isolated Skyrmionic spin texture without the aid of external magnetic field. © 2012 American Physical Society.

Kwon Y.,Sungkyunkwan University | Kwon Y.,Kyoto University
Journal of Rheology | Year: 2012

In the finite element framework, we employ decoupled time integration scheme for viscoelastic fluid (the Leonov model) flow and then investigate highly nonlinear behavior in 2D creeping contraction flow. In the analysis of steady solutions as a preliminary study, the results are shown to be free from frustrating mesh dependence when we incorporate the tensor-logarithmic formulation [Fattal and Kupferman, J. Non-Newtonian Fluid Mech. 123, 281-285 (2004)]. Two kinds of elastic fluid have been chosen, that is, highly shear thinning and Boger-type liquids. According to each liquid property, the transient computational modeling has revealed qualitatively distinct dynamics of instability. With pressure difference imposed slightly below the steady convergence limit, the numerical scheme demonstrates fluctuating solution without approaching steady state for the shear thinning fluid. When the pressure fairly higher than the limit is enforced, severe fluctuation of flowrate, oscillation of corner vortices, and also asymmetric irregular stress wave propagation along the downstream channel wall are expressed. In addition, flow dynamics seems quite stochastic with scanty temporal correlation. For the Boger-type fluid, under the traction higher than steady limit, the flowrate and corner vortices exhibit periodic variation with asymmetry added to the dynamics. These express elastic flow instability in this inertialess flow approximation. © 2012 The Society of Rheology.

Won S.H.,Sungkyunkwan University | Sim S.J.,Korea University
Analyst | Year: 2012

Polydiacetylene (PDA) liposomes possess unique properties that allow liposomes to change color and emit fluorescence in response to stimuli such as temperature, antibody-antigen interaction, pH, mechanical stress, and organic solvent. They have been studied extensively as signal transducers in biosensor applications. Here, we describe an antibody-based biosensor using PDA liposomes for detection of human immunoglobulin E (hIgE). Target hIgE chemically bound to hIgE monoclonal antibodies immobilized on PDA liposomes and the fluorescent signals were slightly increased depending on the target protein concentration. As the primary response, the hIgE could be detected to below 10 ng mL -1. However, fluorescent signals were dramatically increased depending on the target protein concentration when gold nanoparticle-conjugated polyclonal antibody probes were added on the PDA liposomes after the primary immune reaction. A PDA liposome biosensor could detect the hIgE as low as 0.1 ng mL -1 and the sensitivity was increased up to one hundred times higher than the primary response. As a result, we confirmed that gold nanoparticle-conjugated polyclonal antibody probes efficiently enhanced the fluorescent signal of the PDA liposome biosensor chip. This strategy can be useful to detect proteins of ultra-low concentration. This journal is © The Royal Society of Chemistry 1212.

Yoo C.,Sungkyunkwan University
Computers and Geotechnics | Year: 2013

This paper presents the results of a three-dimensional numerical investigation into the interaction between conventional tunneling and a pile supported bridge. Hypothetical tunneling conditions under an existing pile supported bridge were first developed in consideration of an actual urban tunneling situation. Various components of the bridge, including piers, piles, and pile caps have been replicated from the areas in question within this model. Also included in the model is the pile-ground interface to allow for possible slip between the piles and the ground during tunneling. The results of the analysis indicate that during tunnel driving, piles directly above the tunnel can experience significant losses in their shaft loads due to downward settlements of piles relative to surrounding soils. Piles within the same system, but farther away from the tunnel tend to experience slight increases in the pile loads. Practical implications of the findings are discussed. © 2012 Elsevier Ltd.

Shin D.-H.,Sungkyunkwan University
International Journal of Mobile Communications | Year: 2011

This study uses the Technology Acceptance Model (TAM) and Innovation Diffusion Theory (IDT) in attempt to further understand consumers' behavioural intentions towards using 4G mobile services. These new factors are found to be 4G-specific factors that directly shape consumer attitudes and intentions. The results of this study provide a valuable reference for service providers in developing 4G mobile services. The findings overall imply the new dimensions and factors for the adoption of new mobile services. Copyright © 2011 Inderscience Enterprises Ltd.

Kang J.G.,Hallym University | Park C.-Y.,Sungkyunkwan University
Diabetes and Metabolism Journal | Year: 2012

The current recommendations for the treatment of obese people include increased physical activity and reduced calories intake. When the behavioral approach is not sufficient, a pharmacologic treatment is recommended. In past years, numerous drugs have been approved for the treatment of obesity; however, most of them have been withdrawn from the market because of their adverse effects. In fact, amphetamine, rimonabant and sibutramine licenses have been withdrawn due to an increased risk of psychiatric disorders and non-fatal myocardial infarction or stroke. Even if orlistat is not as effective as other drugs in reducing body weight, orlistat is presently the only available choice for the treatment of obesity because of its safety for cardiovascular events and positive effects on diabetic control. Hopefully, more effective and better tolerated anti-obesity drugs will be developed through an improved understanding of the multiple mechanisms and complex physiological systems targeting appetite. © 2012 Korean Diabetes Association.

Kim H.K.,Sungkyunkwan University
Journal of Korean medical science | Year: 2010

Resistance to thyroid hormone (RTH) is an autosomal dominant hereditary disorder that is difficult to diagnose because of its rarity and variable clinical features. The magnitude of RTH is caused by mutations in the thyroid hormone receptor beta (TR beta) gene. We recently treated a 38-yr-old woman with RTH who had incidental papillary thyroid carcinoma. She presented with goiter and displayed elevated thyroid hormone levels with an unsuppressed TSH. She was determined to harbor a missense mutation of M310T in exon 9 of the TR beta gene, and diagnosed with generalized RTH. This mutation has not yet been reported in Korea. RTH is very rare and easily overlooked, but should be considered in patients who present with goiter and elevated thyroid hormone levels with an unsuppressed TSH. The association between thyroid cancer and RTH needs further study.

Jung H.S.,Sungkyunkwan University | Lee J.-K.,University of Pittsburgh
Journal of Physical Chemistry Letters | Year: 2013

TiO2 nanoparticle-based dye sensitized solar cells (DSSCs) have attracted a significant level of scientific and technological interest for their potential as economically viable photovoltaic devices. While DSSCs have multiple benefits such as material abundance, a short energy payback period, constant power output, and compatibility with flexible applications, there are still several challenges that hold back large scale commercialization. Critical factors determining the future of DSSCs involve energy conversion efficiency, long-term stability, and production cost. Continuous advancement of their long-term stability suggests that state-of-the-art DSSCs will operate for over 20 years without a significant decrease in performance. Nevertheless, key questions remain in regards to energy conversion efficiency improvements and material cost reduction. In this Perspective, the present state of the field and the ongoing efforts to address the requirements of DSSCs are summarized with views on the future of DSSCs. © 2013 American Chemical Society.

Kim M.S.,Sungkyunkwan University
Journal of Instrumentation | Year: 2013

The contribution of Resistive Plate Chamber (RPC) to muon reconstruction in CMS has been studied on a sample of muons collected in proton-proton collisions at s = 7 TeV at the LHC in 2011. Muon reconstruction is performed using the all-silicon inner tracker and with up to four stations of gas-ionization muon detectors. Drift Tubes and Cathode Strip Chambers detect muons in the barrel and endcap regions, respectively, and are complemented by the RPC system. Measured distributions of reconstructed hits in the RPCs crossed by muons from Z 0 decays with a transverse momentum pT above 20 GeV/c are well reproduced by the Monte Carlo simulation. From the samples of J/ψ and Z0 events, the efficiencies for muons with and without the inclusion of the RPC hits in the muon track reconstruction are measured and compared with the simulation. Using RPC information in track reconstruction improves up to about 3% of offline reconstruction efficiency for the muons in the region of pT above 7 GeV/c, in good agreement with simulation. © 2013 CERN.

Chang D.K.,Sungkyunkwan University
Clinical Endoscopy | Year: 2012

Colorectal endoscopic submucosal dissection (ESD) is not yet fully popularized in Korea, but is increasing steadily. The outcomes of colorectal ESD in Korea are comparable to those in Japan and other countries. ESD-related complication rates are decreasing as experiences accumulate. Particularly for rectal laterally spreading tumors, ESD is becoming more prevalent than transanal endoscopic microsurgery. Standard indication, qualified training system, and full medical insurance coverage should be established for the procedure to become popular in the long run.

Park S.H.,Sungkyunkwan University
Korean journal of ophthalmology : KJO | Year: 2010

We report a rare case of multicentric Castleman's disease that presented with ophthalmic involvement, along with a review of the literature. A 63-year-old male presented with decreased visual acuity in both eyes. Both eyes had serous elevations of the retinas with shifting subretinal fluid and annular choroidal detachment. No retinal breaks were found. Laboratory tests revealed pancytopenia, hypergammaglobulinemia, and an increased erythrocyte sedimentation rate. Chest and abdominal computed tomographies showed multiple lymphadenopathies in the mediastinum, abdomen, and in both inguinal areas. Histological examination of the inguinal lymph node biopsy was consistent with Castleman's disease. After combination chemotherapy, the serous elevations of both retinas and the annular choroidal detachments of both eyes disappeared. Ophthalmic involvement in Castleman's disease is very rare, and to the authors' knowledge, this is the first report of ophthalmic involvement of Castleman's disease in Korea.

The need for evidence-based decision making in immunization programs has increased due to the presence of multiple health priorities, limited human resources, expensive vaccines, and limited funds. Countries should establish a group of national experts to advise their Ministries of Health. So far, many nations have formed their own National Immunization Technical Advisory Groups (NITAGs). In the Republic of Korea, the Korea Expert Committee on Immunization Practices (KECIP), established by law in the early 1990s, has made many important technical recommendations to contribute to the decline in vaccine preventable diseases and currently functions as a NITAG. It includes 13 core members and 2 non-core members, including a chairperson. Core members usually come from affiliated organizations in internal medicine, pediatrics, obstetrics, microbiology, preventive medicine, nursing and a representative from a consumer group, all of whom serve two year terms. Non-core members comprise two government officials belonging to the Korea Centers for Disease Control and Prevention (KCDC) and the Korea Food and Drug Administration. Meetings are held as needed, but at least twice a year, and sub-committees are formed as a resource for gathering, analyzing, and preparing information for the KECIP meetings. Once the sub-committees or the KCDC review the available data, the KECIP members discuss each issue in depth and develop recommendations, usually by a consensus in the meeting. The KECIP publishes national guidelines and immunization schedules that are updated regularly. KECIP's role is essentially consultative and the implementation of their recommendations may depend on the budget or current laws. © 2012 by The Korean Pediatric Society.

Chae D.,Sungkyunkwan University | Constantin P.,University of Chicago | Wu J.,Oklahoma State University
Archive for Rational Mechanics and Analysis | Year: 2011

Any classical solution of the two-dimensional incompressible Euler equation is global in time. However, it remains an outstanding open problem whether classical solutions of the surface quasi-geostrophic (SQG) equation preserve their regularity for all time. This paper studies solutions of a family of active scalar equations in which each component uj of the velocity field u is determined by the scalar θ through uj = RΛ-1 P(Λ)θ, where R is a Riesz transform and Λ = (-Δ)1/2. The two-dimensional Euler vorticity equation corresponds to the special case P(Λ) = I while the SQG equation corresponds to the case P(Λ) = Λ. We develop tools to bound {double pipe}▽u{double pipe}L∞ for a general class of operators P and establish the global regularity for the Loglog-Euler equation for which P(Λ) = (log(I + log(I - Δ)))γ with 0 ≦ γ ≦ 1. In addition, a regularity criterion for the model corresponding to P(Λ) = Λβ with 0 ≦ β ≦ 1 is also obtained. © 2011 Springer-Verlag.

Sakthivel R.,Sungkyunkwan University | Suganya S.,Anna University | Anthoni S.M.,Anna University
Computers and Mathematics with Applications | Year: 2012

A class of dynamic control systems described by nonlinear fractional stochastic differential equations in Hilbert spaces is considered. Using fixed point technique, fractional calculations, stochastic analysis technique and methods adopted directly from deterministic control problems, a new set of sufficient conditions for approximate controllability of fractional stochastic differential equations is formulated and proved. In particular, we discuss the approximate controllability of nonlinear fractional stochastic control system under the assumptions that the corresponding linear system is approximately controllable. The results in this paper are generalization and continuation of the recent results on this issue. An example is provided to show the application of our result. Finally as a remark, the compactness of semigroup is not assumed and subsequently the conditions are obtained for exact controllability result. © 2011 Elsevier Ltd. All rights reserved.

Ahn C.W.,Sungkyunkwan University
Electronics Letters | Year: 2011

Presented is a fast and adaptive evolutionary algorithm that minimises the resource consumption of network coding while achieving the target multicast rate. To this end, infeasible individuals adaptively participate as well in searching for better solutions, and all individuals are evaluated in an opportunistic manner. The empirical results have adduced grounds for the effectiveness of the approach. © 2011 The Institution of Engineering and Technology.

Kim J.P.,Dankook University | Lee J.S.,Chung - Ang University | Park M.J.,Sungkyunkwan University
Arthroscopy - Journal of Arthroscopic and Related Surgery | Year: 2012

Purpose: The purpose of this study was to review clinical and radiographic outcomes of perilunate dislocations and fracture-dislocations treated with arthroscopic reduction and percutaneous fixation. Methods: Twenty patients who had an acute dorsal perilunate dislocation or fracture-dislocation were treated with an arthroscopic technique at a median interval of 3.9 days from the time of injury. They were retrospectively reviewed at a mean follow-up of 31.2 months (range, 18 to 61 months). Range of motion and grip strength were measured. Radiographic evaluations included time to scaphoid union, measurement of radiologic parameters, and any development of arthritis. Functional outcomes were determined by the modified Mayo wrist score; Disabilities of the Arm, Shoulder and Hand questionnaire; and Patient-Rated Wrist Evaluation score. Results: The flexion-extension motion arc and grip strength of the injured wrist averaged 79% and 78%, respectively, of the corresponding values for the contralateral wrists. The mean Disabilities of the Arm, Shoulder and Hand score was 18, and the mean Patient-Rated Wrist Evaluation score was 30. According to modified Mayo wrist scores, overall functional outcomes were rated as excellent in 3 patients, good in 8, fair in 7, and poor in 2. Nonunion developed in 2 patients with a trans-scaphoid perilunate injury; 1 of the 2 underwent scaphoid excision and midcarpal fusion. On the basis of radiographic parameters, reduction obtained during the operation was maintained within normal ranges in 15 patients. Arthritis had not developed in any patient by the last follow-up. Conclusions: This study suggests that arthroscopic reduction with percutaneous fixation is a reliable minimally invasive surgical method for acute perilunate injuries in that it provides proper restoration and stable fixation of carpal alignment and results in satisfactory functional and radiologic outcomes on a midterm basis. Level of Evidence: Level IV, therapeutic case series. © 2012 Arthroscopy Association of North America.

Chun C.,Sungkyunkwan University
Computers and Mathematics with Applications | Year: 2011

A new application of the Exp-function method in combination with the dependent variable transformation from singularity analysis is proposed for constructing new generalized solitary wave solutions and periodic wave solutions for nonlinear evolution equations. The Kortewegde Vries equation is chosen to illustrate the validity and applicability of the suggested approach. © 2010 Elsevier Ltd. All rights reserved.

Park S.H.,Chung - Ang University | Choi H.-Y.,Gachon University | Hahn S.Y.,Sungkyunkwan University
Journal of Magnetic Resonance Imaging | Year: 2015

Purpose: To investigate correlations between apparent diffusion coefficient (ADC) values of invasive ductal carcinoma (IDC) and pathologic factors on diffusion-weighted MRI. We measured the ADC values of IDC of the breast and analyzed correlations between ADC values and factors such as tumor size, axillary lymph node status, histologic grade, estrogen receptor, progesterone receptor, and human epithelial growth factor 2 (HER2) using diffusion-weighted MRI at 3.0 Tesla (T).Materials and Methods: We examined 110 patients with pathologically confirmed IDC using diffusion-weighted MRI at 3.0T. The ADC values of breast cancer were calculated using two b factors (0 and 1000 s/mm2). The relationship between ADC values and tumor size, histologic grade, axillary lymph node status, hormonal receptors, and HER2 were analyzed.Results: The mean ADC value of IDC (n=110) was 0.88±0.15 × 10-2 mm2/s. Tumors were subgrouped according to size (<2 cm, 2-5 cm, and ≥5 cm). Multiple comparisons within subgroups according to size showed that the ADC values for the three tumor size groups were significantly different (correlation coefficient=-0.007). The mean apparent diffusion coefficient of HER2-positive IDC was significantly higher than that of HER2-negative invasive ductal carcinoma (correlation coefficient=0.218).Conclusion: ADC values of IDC were significantly correlated with tumor size and HER2 status. © 2013 Wiley Periodicals, Inc. 125.

Park S.E.,Sungkyunkwan University
European journal of endocrinology / European Federation of Endocrine Societies | Year: 2013

Angiotensin-converting enzyme 2 (ACE2) plays an important role in glucose metabolism and renal function. However, the relationship between ACE2 and hyperglycemia or microalbuminuria has not been established in humans. We investigated whether urinary ACE2 levels are associated with abnormal glucose homeostasis and urinary albumin excretion. We developed an ELISA for quantifying ACE2 in urine. The ELISA was used to measure urinary ACE2 levels in 621 subjects with: normal glucose tolerance (NGT; n=77); impaired fasting glucose (IFG) or impaired glucose tolerance (IGT) (n=132); and type 2 diabetes mellitus (T2DM, n=412). Insulin resistance was assessed by homeostasis model assessment for insulin resistance (HOMA-IR) index and urinary albumin excretion by urine albumin-to-creatinine ratio (ACR). Other biochemical and anthropometric parameters were measured. Urinary ACE2 levels were significantly higher in insulin-resistant subjects with IFG, IGT, and T2DM than in the NGT group (P<0.001). Urinary ACE2 concentrations appeared to correlate with HOMA-IR, fasting blood glucose, triglyceride, high-sensitivity C-reactive protein, serum creatinine, urinary ACR, and systolic blood pressure (all P<0.05). After adjustment for impaired renal function and other metabolic parameters, urinary ACE2 concentration was still associated with a higher risk for T2DM (OR 1.80, 95% CI 1.05-3.08, P=0.02). In addition, urinary ACE2 levels were highly predictive of microalbuminuria after adjusting for clinical risk factors (OR 2.68, 95% CI 1.55-4.64, P<0.001). Our data suggest that the urinary ACE2 level is closely associated with T2DM and is an independent risk factor for microalbuminuria.

Yoo J.,Korea Institute of Energy Research | Yu G.,Korea Institute of Energy Research | Yi J.,Sungkyunkwan University
Solar Energy Materials and Solar Cells | Year: 2011

Surface texturing of crystalline silicon wafer improves the conversion efficiency of solar cells by the enhancement in antireflection property and light trapping. Compared to antireflection coating, it is a more permanent and effective scheme. Wet texturing with the chemicals such as alkali (NaOH, KOH) or acid (HF, HNO3, CH3COOH) is too difficult for thinner wafer to apply due to a large amount of silicon loss. However, Plasma surface texturing using Reactive Ion Etching (RIE) can be effective in reducing the surface reflectance with low silicon loss. In this study, we have fabricated a large-area (156×156 mm) multicrystalline silicon (mc-Si) solar cell by mask less surface texturing using a SF6/O2 reactive ion etching. We have accomplished texturing with RIE by reducing silicon loss by almost half of that in wet texturing process. By optimizing the processing steps, we achieved conversion efficiency, open circuit voltage, short circuit current density, and fill factor as high as 16.1%, 619 mV, 33.5 mA/cm 2, and 77.7%, respectively. This study establishes that it is possible to fabricate the thin multicrystalline silicon solar cells of low cost and high efficiency using surface texturing by RIE. © 2010 Elsevier B.V. All rights reserved.

Park C.Y.,Dongguk University | Oh S.Y.,Sungkyunkwan University | Chuck R.S.,Yeshiva University
Current Opinion in Ophthalmology | Year: 2012

PURPOSE OF REVIEW: Consideration of angle kappa is important for correct centration of refractive treatments. Decentered refractive treatment can cause photic phenomena including glare, halo, and deterioration of vision. This review highlights the concept of angle kappa, its measurement and distribution in normal populations, and the methods to compensate for large angle kappa in refractive surgery using laser or intraocular lenses (IOLs). RECENT FINDINGS: Determination of the treatment center is very important in refractive surgery. Moving the ablation center from the center of the entrance pupil to points near visual axis, such as the corneal light reflex (line of sight) or corneal vertex normal, results in less induction of higher order aberrations (including coma aberration) and either the same or better visual outcomes both in hyperopic and myopic eyes when compared to laser ablation centered on the entrance pupil. Decentration of multifocal IOLs can result in deterioration of postoperative visual function with induction of higher order aberrations. The occurrence of photic phenomena positively correlated with preoperative values of angle kappa. SUMMARY: There is a growing body of evidence that emphasizes the consideration of angle kappa in refractive surgery. Ignoring angle kappa may sometimes result in decentered treatment and aggravation of visual symptoms. Compensation for angle kappa is important for optimal correction of refractive error by either laser ablation or IOLs, especially for hyperopes and any eyes with large angle kappa. Copyright © Lippincott Williams & Wilkins.

Ahn K.,Sungkyunkwan University | Ahn K.,Samsung
Journal of Allergy and Clinical Immunology | Year: 2014

Atopic dermatitis (AD) is a chronic relapsing inflammatory skin disease and a growing health concern, especially in children, because of its high prevalence and associated low quality of life. Genetic predisposition, environmental triggers, or interactions between them contribute to the pathophysiology of AD. Therefore, it is very important to identify and control risk factors from the environment in susceptible subjects for successful treatment and prevention. Both indoor and outdoor air pollution, which are of increasing concern with urbanization, are well-known environmental risk factors for asthma, whereas there is relatively little evidence in AD. This review highlights epidemiologic and experimental data on the role of air pollution in patients with AD. Recent evidence suggests that a variety of air pollutants, such as environmental tobacco smoke, volatile organic compounds, formaldehyde, toluene, nitrogen dioxide, and particulate matter, act as risk factors for the development or aggravation of AD. These air pollutants probably induce oxidative stress in the skin, leading to skin barrier dysfunction or immune dysregulation. However, these results are still controversial because of the low number of studies, limitations in study design, inaccurate assessment of exposure and absorption, and many other issues. Further research about the adverse effects of air pollution on AD will help to expand our understanding and to establish a better strategy for the prevention and management of AD. © 2014 American Academy of Allergy, Asthma & Immunology.

Lee G.,Sungkyunkwan University
Cyberpsychology, behavior and social networking | Year: 2011

Social-networking sites (SNSs) provide users with a unique computer-mediated environment where individuals are able to disclose their thoughts, feelings, and experiences within their circle of personal ties. From a positive psychological perspective, this research investigated the use of SNSs and users' subjective well-being. The results show that although the time spent using a SNS is not related to well-being, the amount of self-disclosure on SNSs is positively related to subjective well-being. In addition, an individual's socioeconomic status is negatively related to self-disclosing behavior.

Kim B.S.,Dankook University | Lee J.Y.,Sungkyunkwan University
Organic Electronics: physics, materials, applications | Year: 2015

Two different hybrid white organic light-emitting diodes (WOLEDs) with red/blue phosphorescent emitters and a green thermally activated delayed fluorescent (TADF) emitter were designed to develop high efficiency hybrid WOLEDs. One hybrid WOLED (type I) had a device structure with a hybrid emitting layer of green TADF and red phosphorescent emitters stacked on a blue phosphorescent emitting layer and the other hybrid WOLED (type II) had a device architecture with the green TADF emitting layer stacked on a red and blue phosphorescent emitting layer. Efficient energy transfer from the green TADF emitter to the red phosphorescent emitter was observed and balanced white emission could be obtained by optimizing the device structure of the hybrid WOLEDs. A quantum efficiency of 16.2% with a color coordinate of (0.45,0.47) and a quantum efficiency of 18.0% with a color coordinate of (0.37,0.47) were achieved in the type I and type II hybrid WOLEDs, respectively. © 2015 Elsevier B.V. All rights reserved.

Kim H.,Kyung Hee University | Sakthivel R.,Sungkyunkwan University
Reports on Mathematical Physics | Year: 2012

In this paper, some new traveling wave solutions of the (4 + 1)-dimensional Fokas equation, (3 + 1)-dimensional Jumbo. --Miwa equation and (2 + 1)-dimensional Boiti. --Leon. --Pempinelli equation are obtained through the (G′?G)-expansion technique. The key idea of this technique is to take full advantage of a Riccati equation involving two parameters and use its solutions in obtaining the traveling wave solutions. The results reveal that this technique is very effective and powerful for solving higher-dimensional nonlinear problems arising in mathematical physics. © 2012 Polish Scientific Publishers.

Kim T.W.,Sungkyunkwan University
Clinical and molecular hepatology | Year: 2012

Nonselective β-blockers (NSBBs), such as propranolol, reportedly exert a pleiotropic effect in liver cirrhosis. A previous report suggested that survival was higher in patients receiving adjusted doses of NSBBs than in ligation patients. This study investigated whether low-dose NSBB medication has beneficial effects in patients with liver cirrhosis, especially in terms of overall survival. We retrospectively studied 273 cirrhotic patients (199 males; age 53.6±10.2 years, mean±SD) who visited our institution between March 2003 and December 2007; follow-up data were collected until June 2011. Among them, 138 patients were given a low-dose NSBB (BB group: propranolol, 20-60 mg/day), and the remaining 135 patients were not given an NSBB (NBB group). Both groups were stratified randomly according to Child-Turcotte-Pugh (CTP) classification and age. The causes of liver cirrhosis were alcohol (n=109, 39.9%), hepatitis B virus (n=125, 45.8%), hepatitis C virus (n=20, 7.3%), and cryptogenic (n=19, 7.0%). The CTP classes were distributed as follows: A, n=116, 42.5%; B, n=126, 46.2%; and C, n=31, 11.4%. Neither the overall survival (P=0.133) nor the hepatocellular carcinoma (HCC)-free survival (P=0.910) differed significantly between the BB and NBB groups [probability of overall survival at 4 years: 75.1% (95% CI=67.7-82.5%) and 81.2% (95% CI=74.4-88.0%), respectively; P=0.236]. In addition, the delta CTP score did not differ significantly between the two groups. Use of low-dose NSBB medication in patients with liver cirrhosis is not indicated in terms of overall and HCC-free survival.

Lee J.-H.,Catholic University of Korea | Park N.-G.,Sungkyunkwan University | Shin Y.-J.,Catholic University of Korea
Solar Energy Materials and Solar Cells | Year: 2011

The nano-grain ZnO/SnO2 composite electrode was prepared by adding 5 w% of the 200250 nm ZnO particles to the 5 nm SnO2 colloid in the presence of hydroxypropylcellulose (M.W.=80,000). The nano-grain SnO 2 electrode was obtained by removing the ZnO particles from the composite electrode using acetic acid. The FE-SEM micrographs revealed that both electrodes consisted of interconnected nano-grains that were ca. 800 nm in size, and the large pores between the grains furnished the wide electrolyte diffusion channels within the electrodes. The photovoltaic properties of the nano-grain electrodes were investigated by measuring the IV behaviors, the IPCE spectra and the ac-impedance spectra. The nano-grain electrodes exhibited remarkably improved conversion efficiencies of 3.96% for the composite and 2.98% for the SnO2 electrode compared to the value of 1.66% for the usual nano-particle SnO2 electrode. The improvement conversion efficiencies were mainly attributed to the formation of nano-grains, which facilitated the electron diffusion within the grains. The improved electrolyte diffusion as well as the light-scattering effects enhanced the photovoltaic performance of the SnO2 electrode. © 2010 Elsevier B.V. All rights reserved.

Jun Y.,Ulsan National Institute of Science and Technology | Park J.H.,Sungkyunkwan University | Kang M.G.,Electronics and Telecommunications Research Institute
Chemical Communications | Year: 2012

The tubular-shaped nanostructure of TiO 2 is very interesting, and highly ordered arrays of TiO 2 nanotubes (TNTs) can be easily fabricated by anodization of the Ti substrate in specific electrolytes. Here in this feature article, we review synthesis methods for various TNTs including normal, alloy, and architectural forms such as bamboos, lace, and flowers. Specific nanosize architectures such as bamboo and lace types can be regulated by alternating voltage and further anodizing. In order to extend light response of TNTs to visible solar spectra, various dopings of specific elements have been discussed. The normal and modified TNTs are suggested for applications such as dye sensitized solar cells, water splitting, photocatalytic degradation of pollutants, CO 2 reduction, sensors, energy storage devices including Li ion batteries and supercapacitors, and other applications such as flexible substrate and biomaterials. © 2012 The Royal Society of Chemistry.

Kim T.H.,Sungkyunkwan University
Korean journal of ophthalmology : KJO | Year: 2012

A 32-year-old man with blurred vision in the right eye and headache presented with anterior uveitis, an intraocular pressure (IOP) of 60 mmHg, an open angle, no visual field defects, and normal optic nerve. He had a history of five previous similar attacks. In each of the previous instances, his anterior uveitis and high IOP were controlled with antiglaucoma medications and topical steroids. However, at the fifth attack, his optic disc was pale and a superior paracentral visual field defect was shown. Brain magnetic resonance image studies were normal. This case represents that a recurrent Posner-Schlossman syndrome (PSS)-induced optic disc atrophy likely due to ocular ischemia caused by a recurrent, high IOP. Although PSS is a self-limiting syndrome, we should manage high IOP and prevent ischemia of the optic nerve head by treating with ocular antihypertensive medications.

Das K.C.,Sungkyunkwan University | Trinajstic N.,Ruder Boskovic Institute
Chemical Physics Letters | Year: 2010

The first geometric-arithmetic index (GA) [1] and atom-bond connectivity index (ABC) [2] that are recently introduced, are found to be useful tools in QSPR and QSAR studies. In this letter we compare the GA and ABC indices for chemical trees and molecular graphs. Moreover, we also compare these two indices for general graphs. © 2010 Elsevier B.V.

Na S.R.,University of Texas at Austin | Suk J.W.,Sungkyunkwan University | Ruoff R.S.,University of Texas at Austin | Huang R.,University of Texas at Austin | Liechti K.M.,University of Texas at Austin
ACS Nano | Year: 2014

The wet-transfer of graphene grown by chemical vapor deposition (CVD) has been the standard procedure for transferring graphene to any substrate. However, the nature of the interactions between large area graphene and target substrates is unknown. Here, we report on measurements of the traction - separation relations, which represent the strength and range of adhesive interactions, and the adhesion energy between wet-transferred, CVD grown graphene and the native oxide surface of silicon substrates. These were determined by coupling interferometry measurements of the separation between the graphene and silicon with fracture mechanics concepts and analyses. The measured adhesion energy was 357 ± 16 mJ/m2, which is commensurate with van der Waals interactions. However, the deduced traction - separation relation for graphene-silicon interactions exhibited a much longer range interaction than those normally associated with van der Waals forces, suggesting that other mechanisms are present. (Graph Presented). © 2014 American Chemical Society.

Mathiyalagan K.,Anna University | Sakthivel R.,Sungkyunkwan University
Canadian Journal of Physics | Year: 2012

This paper presents some novel results on robust stabilization and H ∞ control design for a class of uncertain discrete-time stochastic genetic regulatory networks (GRNs) with time-varying delays. The GRNs under consideration are subject to stochastic noise, time-varying, and norm bounded parameter uncertainties. By constructing a new Lyapunov-Krasovskii functional that contains some novel triple summation terms, we propose a state feedback gene controller to guarantee that the considered GRN is mean-square asymptotically stable about its equilibrium point for all admissible uncertainties. The other issue is to design a H ∞ feedback gene controller so that the GRN is robustly stable with a prescribed H ∞ disturbance attenuation level for all admissible uncertainties and for all delays to satisfy both the lower bound and upper bound of the interval time-varying delay. The obtained conditions are derived in terms of linear matrix inequalities (LMIs), which can be easily verified via the LMI toolbox. Finally, the control scheme has been implemented in a gene network model to illustrate the applicability and usefulness of the obtained results. © 2012 Published by NRC Research Press.

Kim T.H.,Sungkyunkwan University
Molecular medicine (Cambridge, Mass.) | Year: 2012

The pathogenesis of sepsis is characterized by overwhelming inflammatory responses that lead to tissue damage and organ failure. Toll-like receptor (TLR) signaling is crucial for induction of hyperinflammatory responses and tissue injury during sepsis. Genipin, an aglycon of geniposide, has antiinflammatory and antimicrobial activities. The purpose of this study was to test the hypothesis that genipin reduces multiple organ dysfunction and mortality during sepsis through inhibition of TLR signaling. Male ICR were subjected to sepsis by cecal ligation and puncture (CLP) or endotoxemia by lipopolysaccharide (LPS). Various doses of genipin (1, 2.5 and 5 mg/kg) or a vehicle were administered intravenously immediately after CLP or intraperitoneally after LPS treatment. In another set of survival tests, mice were treated with 2.5 mg/kg of genipin 0 and 24 h after CLP. Genipin was found to improve survival and to attenuate multiple organ dysfunction. Genipin attenuated production of proinflammatory cytokines and release of high-mobility group box 1 (HMGB1). Genipin prevented TLR2 and TLR4, myeloid differentiation factor 88 and the Toll/interleukin-1 receptor domain-containing adaptor protein, inducing interferon-β overexpression. Phosphorylation of mitogen-activated protein kinases and interferon regulatory factor 3 and translocation of nuclear factor (NF)-κB were prevented by genipin. Moreover, genipin attenuated increases in serum tumor necrosis factor-α and HMGB1 in LPS-induced endotoxemia. Pam3CSK4- and LPS-mediated production of nitrites and proinflammatory cytokines was suppressed by genipin in RAW264.7 cells. Genipin attenuated mortality and organ injuries during sepsis through interference with TLR signaling. Therefore, genipin might be useful as a potential therapeutic agent for treatment of sepsis.

Lim D.H.,Sungkyunkwan University
Korean journal of ophthalmology : KJO | Year: 2013

To assess the refractive change and prediction error after temporary intraocular lens (IOL) removal in temporary polypseudophakic eyes using IOL power calculation formulas and Gills' formula. Four consecutive patients (7 eyes) who underwent temporary IOL explantation were enrolled. Postoperative refractions calculated using IOL power calculation formulas (SRK-II, SRK-T, Hoffer-Q, Holladay, and the modified Gills' formula for residual myopia and residual hyperopia) were compared to the manifest spherical equivalents checked at 1 month postoperatively. The mean ages of temporary piggyback IOL implantation and IOL removal were 6.71 ± 3.68 months (range, 3 to 12 months) and 51.14 ± 18.38 months (range, 29 to 74 months), respectively. The average refractive error was -13.11 ± 3.10 diopters (D) just before IOL removal, and improved to -1.99 ± 1.04 D after surgery. SRK-T showed the best prediction error of 1.17 ± 1.00 D. The modified Gills' formula for myopia yielded a relatively good result of 1.47 ± 1.27 D, with only the variable being axial length. Formulas to predict refractive change after temporary IOL removal in pediatric polypseudophakia were not as accurate as those used for single IOL implantation in adult eyes. Nonetheless, this study will be helpful in predicting postoperative refraction after temporary IOL removal.

Sakthivel R.,Sungkyunkwan University | Ren Y.,Anhui Normal University | Mahmudov N.I.,Eastern Mediterranean University
Computers and Mathematics with Applications | Year: 2011

Fractional differential equations have wide applications in science and engineering. In this paper, we consider a class of control systems governed by the semilinear fractional differential equations in Hilbert spaces. By using the semigroup theory, the fractional power theory and fixed point strategy, a new set of sufficient conditions are formulated which guarantees the approximate controllability of semilinear fractional differential systems. The results are established under the assumption that the associated linear system is approximately controllable. Further, we extend the result to study the approximate controllability of fractional systems with nonlocal conditions. An example is provided to illustrate the application of the obtained theory. © 2011 Elsevier Ltd. All rights reserved.

Jang H.W.,Sungkyunkwan University | Kim K.-J.,Dongguk University
BMC Medical Education | Year: 2014

Background: Multimedia learning has been shown effective in clinical skills training. Yet, use of technology presents both opportunities and challenges to learners. The present study investigated student use and perceptions of online clinical videos for learning clinical skills and in preparing for OSCE (Objective Structured Clinical Examination). This study aims to inform us how to make more effective us of these resources. Methods. A mixed-methods study was conducted for this study. A 30-items questionnaire was administered to investigate student use and perceptions of OSCE videos. Year 3 and 4 students from 34 Korean medical schools who had access to OSCE videos participated in the online survey. Additionally, a semi-structured interview of a group of Year 3 medical students was conducted for an in-depth understanding of student experience with OSCE videos. Results: 411 students from 31 medical schools returned the questionnaires; a majority of them found OSCE videos effective for their learning of clinical skills and in preparing for OSCE. The number of OSCE videos that the students viewed was moderately associated with their self-efficacy and preparedness for OSCE (p < 0.05). One-thirds of those surveyed accessed the video clips using mobile devices; they agreed more with the statement that it was convenient to access the video clips than their peers who accessed the videos using computers (p < 0.05). Still, students reported lack of integration into the curriculum and lack of interaction as barriers to more effective use of OSCE videos. Conclusions: The present study confirms the overall positive impact of OSCE videos on student learning of clinical skills. Having faculty integrate these learning resources into their teaching, integrating interactive tools into this e-learning environment to foster interactions, and using mobile devices for convenient access are recommended to help students make more effective use of these resources. © 2014 Jang and Kim; licensee BioMed Central Ltd.

Kim H.,Sungkyunkwan University
Journal of Modern Optics | Year: 2012

Generalized Doppler shift for light is derived by considering both velocity and acceleration, and is used to calculate time dilation ratio. A circular mirror used to measure time is transformed to the elliptical mirror in a reference frame when it is in motion. The special relativistic Doppler shift is calculated in any propagation direction of light for a constant velocity of motion. Furthermore, the generalized Doppler shift is derived by considering both the velocity and the acceleration effect. The ratio of the frequency shifts are shown as a function of velocity, acceleration, and detection angle. © 2012 Copyright Taylor and Francis Group, LLC.

FGFR2 gene amplification, and resulting FGFR2 protein overexpression, is rare in gastric cancer patients, and development of an accurate and widely available method for mass screening to identify patients who may respond to treatment with fibroblast growth factor receptor (FGFR) inhibitors is important. We first screened 312 gastric cancer patients with known copy number variations by FGFR2b immunohistochemistry using FPR2-D, an isoform-specific antibody. Next, we performed immunohistochemistry on tissue microarrays from 1574 gastric cancer patients. Selected cases were analyzed for FGFR2 amplification by FISH. In addition, FGFR2b overexpression was studied in 88 matched primary and metastatic gastric cancers. In the first cohort, FGFR2b immunohistochemistry results correlated very well with those of copy number variation (r=0.79) and FISH (r=1.0). In total, FGFR2b overexpression was identified in 73 of 1974 gastric cancers (4%). The concordance between immunohistochemistry and FISH was extremely high; all 2+ and 3+ cases identified by immunohistochemistry were FGFR2 amplified. In the matched primary and metastatic gastric cancer pairs, the positivity and percentage of positive tumor cells were significantly higher in metastatic gastric cancers than in primary gastric cancers (8% vs 3% and 75% vs 47%, respectively; P<0.001). FGFR2b overexpression was significantly more frequent in gastric cancers with diffuse subtype (P=0.01) and higher N stage (P=0.006). FGFR2b overexpression with H-score ≥150 were independent prognostic factors for overall survival with hazard ratio of 1.836 (95% confidence interval, 1.034–3.261; P=0.038). FGFR2b positivity in immunohistochemistry was strongly correlated with FGFR2 amplification. Given the low frequency of FGFR2 amplification in gastric cancers, FGFRb2 immunohistochemistry is an accurate screening tool to detect FGFR2 amplification, and both primary and metastatic gastric cancer tissues should be tested to select gastric cancer patients for treatment with FGFR2 inhibitors.Modern Pathology advance online publication, 27 May 2016; doi:10.1038/modpathol.2016.96. © 2016 United States & Canadian Academy of Pathology

Oh H.-G.,Soonchunhyang University | Rhee E.-J.,Sungkyunkwan University
Stroke | Year: 2015

Background and Purpose-Intracranial arterial stenosis (ICAS) is considered an important cause of stroke in Asians. Coronary artery calcification (CAC) is a surrogate marker for subclinical atherosclerosis. We aimed to analyze the association of ICAS assessed by transcranial Doppler ultrasonography and CAC in middle-aged Korean population.Methods-This study included 10 550 participants (81.3% men, mean age 43 years) from a health screening program, in whom transcranial Doppler ultrasonography was used to detect >50% intracranial stenosis based on criteria modified from the stroke outcomes and neuroimaging of intracranial atherosclerosis trial. Multidetector computed tomography was used to assess coronary artery calcium score (CACS). CAC grade (0, 1-100, and >100) was defined by CACS.Results-The subjects with CAC showed significantly higher proportion of subjects with ICAS compared with those without CAC (4.4% versus 2.8%; P<0.01). Conversely, the subjects with ICAS showed significantly higher proportion of subjects with CAC (24.8% versus 17.1%; P<0.01). When logistic regression analysis was performed with ICAS as the dependent variable, the presence of CAC showed significantly increased risk for ICAS after adjustment for confounding variables (odds ratio, 1.439; 95% confidence interval, 1.095-1.891). When CACS grade was included in the model, the odds ratio for ICAS was the highest in subjects with CACS >400 compared with those with CACS=0 (odds ratio, 2.754; 95% confidence interval, 1.205-2.936).Conclusions-The risk for ICAS was significantly increased in middle-aged Korean subjects with CAC compared with that in those without CAC. These findings suggest the possibility of a separate undetected atherosclerotic focus in subjects with 1 atherosclerotic event. © 2014 American Heart Association, Inc.

Shin D.-H.,Sungkyunkwan University
Information Technology and People | Year: 2012

Purpose: The purpose of this paper is to present a predictive model of attitudes toward 3DTV. Design/methodology/approach: Structural equation modeling is used to construct a predictive model of attitudes toward 3DTV. Individuals' responses to questions about attitude and intention to use 3DTV were collected and analyzed. Findings: The model shows significant roles for social presence and flow, both of which affect attitude as well as perceived usefulness and perceived enjoyment. This set of factors is a key to users' expectations of 3DTV. Given the significant role of social presence, the study attempts to conceptualize social presence in the 3DTV context. Research limitations/implications: The findings imply that social presence may be enhanced by illusions of advanced technical manipulation, but it can be more effectively enhanced by a sense of belonging or emotional connection. Practical implications: Specific design features and characteristics of 3DTV services can be utilized to achieve meaningful social presence. Originality/value: The proposed model brings together extant research on 3DTV and supports eventual 3D acceptance. © Emerald Group Publishing Limited.

Yun J.,Sungkyunkwan University
Asian Journal of Organic Chemistry | Year: 2013

The development of catalytic Cu-B additions to carbon-carbon unsaturated bonds (borylcupration) with high regio- and stereoselectivity has enabled facile and direct syntheses of alkenylboronic esters, which are versatile synthetic intermediates in organic synthesis. An increasing number of relevant reactions have been reported over the past several years, which can be categorized based on the electrophilic reagent that reacts with the common alkenylcopper intermediates that are generated insitu by Cu-B addition to alkynes. In this Focus Review, recent advances in copper-catalyzed boron addition reactions for the synthesis of alkenylboronic esters with diboron reagents are summarized. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Kwon Y.,Sungkyunkwan University
Journal of Computational Physics | Year: 2014

Investigating highly nonlinear viscoelastic flow in 2D domain, we explore problem as well as property possibly inherent in the streamline upwinding technique (SUPG) and then present various results of elastic instability. The mathematically stable Leonov model written in tensor-logarithmic formulation is employed in the framework of finite element method for spatial discretization of several representative problem domains. For enhancement of computation speed, decoupled integration scheme is applied for shear thinning and Boger-type fluids. From the analysis of 4:1 contraction flow at low and moderate values of the Deborah number (De) the solution with SUPG method does not show noticeable difference from the one by the computation without upwinding. On the other hand, in the flow regime of high De, especially in the state of elastic instability the SUPG significantly distorts the flow field and the result differs considerably from the solution acquired straightforwardly. When the strength of elastic flow and thus the nonlinearity further increase, the computational scheme with upwinding fails to converge and evolutionary solution does not become available any more. All this result suggests that extreme care has to be taken on occasions where upwinding is applied, and one has to first of all prove validity of this algorithm in the case of high nonlinearity. On the contrary, the straightforward computation with no upwinding can efficiently model representative phenomena of elastic instability in such benchmark problems as 4:1 contraction flow, flow over a circular cylinder and flow over asymmetric array of cylinders. Asymmetry of the flow field occurring in the symmetric domain, enhanced spatial and temporal fluctuation of dynamic variables and flow effects caused by extension hardening are properly described in this study. © 2014 Elsevier Inc.

Lee M.-S.,Sungkyunkwan University
Trends in Endocrinology and Metabolism | Year: 2014

While the role of autophagy in the physiology of endocrine organs and the development of metabolic disorders or diabetes has been investigated, the relationship between the pancreatic islet and autophagy has not been explored extensively. In this review, studies on the possible involvement of dysregulated autophagy in the pathogenesis of metabolic syndrome and diabetes will be summarized with an emphasis on the autophagic process in pancreatic islet β cells. Novel findings regarding the role of autophagy in human β cell pathology and the development of type 2 diabetes (T2D) characterized by islet amyloid deposition will be discussed. Careful design of agents enhancing autophagic activity in β cells might serve as a novel approach towards therapeutics for the treatment of diabetes. © 2014 Elsevier Ltd.

Paik Y.H.,Sungkyunkwan University
The Korean journal of hepatology | Year: 2011

NADPH oxidase (NOX) is a multicomponent enzyme complex that generates reactive oxygen species (ROS) in response to a wide range of stimuli. ROS is involved as key secondary messengers in numerous signaling pathways, and NADPH oxidases complex has been increasingly recognized as key elements of intracellular signaling of hepatic fibrogenesis. In the liver, NADPH oxidase is functionally expressed both in the phagocytic form and in the non-phagocytic form. The non-phagocytic NADPH oxidase complex is structurally and functionally similar to the phagocytic NADPH, resulting in reduction of molecular oxygen to generate superoxide. There are six homologous NOX proteins in the non-phagocytic forms of NADPH oxidase. An emerging concept is that both phagocytic and nonphagocytic NADPH oxidase components in hepatic stellate cells (HSCs) mediate hepatic fibrosis, suggesting its potential role as a pharmacological target for anti-fibrotic therapy. The molecular components and signaling pathways of various NADPH oxidase homologues that are critical for the fibrotic activity in HSCs need to be more clearly identified.

Cho J.,Sungkyunkwan University
Medicine and Science in Sports and Exercise | Year: 2014

RESULTS: Chronic exposure to a HFD resulted in hepatic steatosis in conjunction with an obese and impaired glucose tolerance condition characterized by dyslipidemia, hyperinsulinemia elevated markers for the liver damage, and hypoadiponectinemia. While VIT and MIT alleviated the NAFLD conditions, the former was more effective at alleviating hepatic steatosis than the latter. The intensity-dependent benefit of exercise training against hepatic steatosis was associated with a greater activation of VIT on hepatic AMPK in conjunction with a greater suppressive effect of VIT on hypoadiponectinemia, downregulation of the AdipoR2 signaling pathway, and upregulation of the NF-kB signaling pathway in the liver.CONCLUSIONS: The current findings suggest that VIT is an alternative way of exercise training to combat hepatic steatosis associated with an obese and impaired glucose tolerance phenotype.PURPOSE: To test the hypothesis that vigorous-intensity and interval training is as effective as moderate-intensity and continuous exercise training on NAFLD in a high fat diet (HFD)-induced obese mice.METHODS: C57BL/6 mice (N=40) were fed a standard chow diet (n=10) or HFD (n=30) for 16 weeks. After the initial 8-week dietary treatments, HFD mice were further divided into HFD only (n=10), HFD plus vigorous-intensity and interval treadmill running (VIT) (n=10) and HFD plus moderate-intensity and continuous treadmill running (MIT) (n=10) for the remaining 8-week period.BACKGROUD: Training intensity may play a key role in magnifying the protective effect of physical exercise against non-alcoholic fatty liver disease (NAFLD). © 2014 American College of Sports Medicine

Park J.,Sungkyunkwan University | Sloman S.A.,Brown University
Cognitive Psychology | Year: 2013

What kind of information do people use to make predictions? Causal Bayes nets theory implies that people should follow structural constraints like the Markov property in the form of the screening-off rule, but previous work shows little evidence that people do. We tested six hypotheses that attempt to explain violations of screening off, some by asserting that people use mechanistic knowledge to infer additional latent structure. In three experiments, we manipulated whether the causal relations among variables within a causal structure were supported by the same or different mechanisms. The experiments differed in the type of causal structures (common cause vs. chain), the way that causal structures were presented (verbal description vs. observational learning), how the mechanisms were presented (explicit description vs. implicit description vs. visual hint), and the number of predictions requested (2 vs. 24). The results revealed that the screening-off rule was violated more often when the mechanisms were the same than when they were different. The findings suggest that people use knowledge about underlying mechanisms to infer latent structure for prediction. © 2013 Elsevier Inc.