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Yonsei University ) is a private research university located in Seoul, South Korea. Yonsei was established in 1885 and is one of the oldest universities in South Korea.The student body consists of 38,725 students: 26,731 undergraduate students, 11,994 graduate students, 4,518 faculty members, 6,788 staff, and 257,931 alumni. Today, Yonsei operates its main campus in Seoul that have extensive programs in the Korean and English language.The university was formally established in January, 1957 through the union of Yonhi College and Severance Union Medical College . This was a result of a lasting bilateral cooperation between the two colleges that began in the 1920s. The institutions were new to Korea at the time of their inception — Yonhi College was one of the first modern colleges, founded originally as Chosun Christian College in March, 1915, and Severance has its roots in the first modern medical center in Korea, Gwanghyewon , founded in April, 1885. As a tribute, the name 'Yonsei' was derived from the first syllables of the names of its two parent institutions, 'Yon; 연; 延' from Yonhi College and 'Sei; 세; 世' from Severance Union Medical College. Wikipedia.

No data exist regarding the relationship between aspirin/clopidogrel resistance and intra-stent thrombi on follow-up optical coherence tomography (OCT) after drug-eluting stent (DES) implantation. The purpose of this study was to evaluate the relationship between aspirin/clopidogrel resistance and intra-stent thrombi on the follow-up OCT in DES-treated patients. A total of 308 DES-treated patients who underwent follow-up OCT and simultaneous measurement of aspirin reaction unit (ARU) and P2Y12 reaction unit (PRU) using the VerifyNow assay system were selected for the study. Aspirin and clopidogrel resistance were defined as ARU ≥550 and PRU ≥275, respectively. Intra-stent thrombi were detected in 29 patients (9.4%). The mean time interval from DES implantation to OCT was 195 ± 133 days (202.9 ± 103.0 days for patients with intra-stent thrombi vs. 194.7 ± 136.0 days for patients without intra-stent thrombi; P = 0.750). There were no significant differences between patients with and without intra-stent thrombi with regard to the incidence of aspirin resistance (13.8 vs. 11.1%, respectively; P = 0.630) or clopidogrel resistance (72.4 vs. 50.5%, respectively; P = 0.056). The percentage of uncovered struts was 17.9 ± 15.8% in patients with intra-stent thrombi and 12.7 ± 17.3% in patients without intra-stent thrombi (P = 0.098). Stent length was significantly longer in patients with intra-stent thrombi (22.9 ± 6.0 vs. 19.4 ± 5.0 mm, P = 0.006). Multivariate logistic regression analysis showed that stent length (odds ratio = 1.152, 95% confidential interval 1.025-1.295; P = 0.017) was the only independent risk factor for the presence of intra-stent thrombi on OCT. This OCT study suggested that the presence of intra-stent thrombi may not be associated with aspirin/clopidogrel resistance in DES-treated patients.

Lee Y.-K.,Yonsei University
Scripta Materialia | Year: 2012

The microstructural evolution characteristics, especially mechanical twinning during plastic deformation in twinning-induced plasticity (TWIP) steels, are briefly reviewed based on available results in the literature. The mechanical twinning behavior is presented and discussed in terms of various factors, such as the stacking fault energy, chemical composition, deformation conditions, the size and orientation of austenite grains, and precipitation, all of which cause some variation of the strain hardening of TWIP steels. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Chang C.-H.,Yonsei University
Korean Journal of Anesthesiology | Year: 2013

Many medical schools and hospitals throughout the world are equipped with a simulation center for the purpose of training anesthesiologists to perform both technical and non-technical skills. Because induction, maintenance, and emergence of general anesthesia are critical to patient welfare, various simulation mannequins and tools are utilized for the purpose of training anesthesiologists for safer patient care. Traditionally, anesthesia residency training mostly consisted of didactic lectures and observations. After completion of "traditional" training, anesthesia residents were allowed to perform procedures on patients under supervision. However, simulation would be a more effective training tool for which to teach anesthesiologists the skills necessary to perform invasive procedures, such as endotracheal intubation, central venous catheter insertion, and epidural catheter insertion. Recently, non-technical skills, such as the Anesthesia Non-Technical Skills developed by anesthesiologists from Aberdeen University, have been emphasized as an important training resource. Technical skills and non-technical skills can be learned by anesthesiology residents through a standardized and organized simulation program. Such programs would be beneficial in training anesthesia residents to work efficiently as a team in the operation room. © the Korean Society of Anesthesiologists, 2013.

The fluctuation of population size has not been well studied in the previous studies of theoretical linkage disequilibrium (LD) expectation. In this study, an improved theoretical prediction of LD decay was derived to account for the effects of changes in effective population sizes. The equation was used to estimate effective population size (Ne) assuming a constant Ne and LD at equilibrium, and these Ne estimates implied the past changes of Ne for a certain number of generations until equilibrium, which differed based on recombination rate. As the influence of recent population history on the Ne estimates is larger than old population history, recent changes in population size can be inferred more accurately than old changes. The theoretical predictions based on this improved expression showed accurate agreement with the simulated values. When applied to human genome data, the detailed recent history of human populations was obtained. The inferred past population history of each population showed good correspondence with historical studies. Specifically, four populations (three African ancestries and one Mexican ancestry) showed population growth that was significantly less than that of other populations, and two populations originated from China showed prominent exponential growth. During the examination of overall LD decay in the human genome, a selection pressure on chromosome 14, the gephyrin gene, was observed in all populations. © 2012 Leeyoung Park.

Song J.W.,Yonsei University
The International journal of oral & maxillofacial implants | Year: 2013

To determine the optimal dilation pixel size distance from the mini-implant interface needed to compensate for the metal artifact on micro-computed tomography (micro-CT) for bone morphometric analysis. A total of 72 self-drilling mini-implants were placed into the buccal alveolar bone of six male beagle dogs. After 12 weeks of orthodontic loading, specimens were harvested and scanned with micro-CT (Skyscan 1076) at a resolution of 9 μm. Using the reload plug-in and dilation procedure of CTAn, the percentage of bone-implant contact (BIC) and bone volume density (BV/TV, bone volume/total volume), respectively, were measured from one to seven pixels from the metal implant surface. Each pixel size of dilation (PSD) were compared with that of a ground histologic section, and the optimal PSD for bone morphometric analysis using micro-CT was determined. BIC values from micro-CT analysis decreased when the PSD increased (P < .05). BIC from micro-CT showed the highest correlation coefficient with BIC from histologic slides when the PSD was 5 to 7 (P < .05), whereas BV/TV from micro-CT showed a very high correlation with BV/TV from histologic slides in all ranges (P < .0001). To measure BIC and BV/TV using micro-CT, at least 5 PSD from the metal implant surface is needed.

Souri K.,Technical University of Delft | Chae Y.,Yonsei University | Makinwa K.A.A.,Technical University of Delft
IEEE Journal of Solid-State Circuits | Year: 2013

This paper describes the design of a low power, energy-efficient CMOS smart temperature sensor intended for RFID temperature sensing. The BJT-based sensor employs an energy-efficient 2nd-order zoom ADC, which combines a coarse 5-bit SAR conversion with a fine 10-bit ΔΣ conversion. Moreover, a new integration scheme is proposed that halves the conversion time, while requiring no extra supply current. To meet the stringent cost constraints on RFID tags, a fast voltage calibration technique is used, which can be carried out in only 200 msec. After batch calibration and an individual room-temperature calibration, the sensor achieves an inaccuracy of ±0.15°C 3σ from-55°C to 125°C. Over the same range, devices from a second lot achieved an inaccuracy of ± 0.25°C (3σ) in both ceramic and plastic packages. The sensor occupies 0.08 mm2 in a 0.16 μm CMOS process, draws 3.4 μA from a 1.5 V to 2 V supply, and achieves a resolution of 20 mK in a conversion time of 5.3 msec. This corresponds to a minimum energy dissipation of 27 nJ per conversion. © 1966-2012 IEEE.

A new technique, which can compensate for the lack of channel bandwidth in an optical wireless orthogonal frequency division multiplexing (OFDM) link based on a light emitting diode (LED), is proposed. It uses an adaptive sampling and an inverse discrete cosine transform in order to convert an OFDM signal into a sparse waveform so that not only is the important data obtained efficiently but the redundancy one is removed. In compressive sensing (CS), a sparse signal that is sampled below the Nyquist/Shannon limit can be reconstructed successively with enough measurement. This means that the CS technique can increase the data rate of visible light communication (VLC) systems based on LEDs. It is observed that the data rate of the proposed CS-based VLC-OFDM link can be made 1.7 times greater than a conventional VLCOFDM link (from 30.72 Mb/s to 51.2 Mb/s). We see that the error vector magnitude (EVM) of the quadrature phase shift keying (QPSK) symbol is 31% (FEC limit: EVM of 32%) at a compression ratio of 40%. © 2014 Optical Society of America.

Park H.-J.,Yonsei University | Friston K.,University College London
Science | Year: 2013

How rich functionality emerges from the invariant structural architecture of the brain remains a major mystery in neuroscience. Recent applications of network theory and theoretical neuroscience to large-scale brain networks have started to dissolve this mystery. Network analyses suggest that hierarchical modular brain networks are particularly suited to facilitate local (segregated) neuronal operations and the global integration of segregated functions. Although functional networks are constrained by structural connections, context-sensitive integration during cognition tasks necessarily entails a divergence between structural and functional networks. This degenerate (many-to-one) function-structure mapping is crucial for understanding the nature of brain networks. The emergence of dynamic functional networks from static structural connections calls for a formal (computational) approach to neuronal information processing that may resolve this dialectic between structure and function.

Park H.W.,Yonsei University
Cold Spring Harbor perspectives in medicine | Year: 2012

Many cystic fibrosis transmembrane conductance regulator (CFTR)-expressing epithelia secrete bicarbonate (HCO(3)(-))-containing fluids. Recent evidence suggests that defects in epithelial bicarbonate secretion are directly involved in the pathogenesis of cystic fibrosis, in particular by building up hyperviscous mucus in the ductal structures of the lung and pancreas. Pancreatic juice is one of the representative fluids that contain a very high concentration of bicarbonate among bodily fluids that are secreted from CFTR-expressing epithelia. We introduce up-to-date knowledge on the basic principles of transepithelial bicarbonate transport by showing the mechanisms involved in pancreatic bicarbonate secretion. The model of pancreatic bicarbonate secretion described herein may also apply to other exocrine epithelia. As a central regulator of bicarbonate transport at the apical membrane, CFTR plays an essential role in both direct and indirect bicarbonate secretion. The major role of CFTR in bicarbonate secretion would be variable depending on the tissue and cell type. For example, in epithelial cells that produce a low concentration of bicarbonate-containing fluid (up to 80 mm), either CFTR-dependent Cl(-)/HCO(3)(-) exchange or CFTR anion channel with low bicarbonate permeability would be sufficient to generate such fluid. However, in cells that secrete high-bicarbonate-containing fluids, a highly selective CFTR bicarbonate channel activity is required. Therefore, understanding the molecular mechanism of transepithelial bicarbonate transport and the role of CFTR in each specific epithelium will provide therapeutic strategies to recover from epithelial defects induced by hyposecretion of bicarbonate in cystic fibrosis.

Shim H.,Yonsei University | Lee S.,Kyung Hee University
Optics Express | Year: 2014

A time-of-flight(ToF) depth sensor produces noisy range data due to scene properties such as surface materials and reflectivity. Sensor measurement frequently includes either a saturated or severely noisy depth and effective depth accuracy is far below its ideal specification. In this paper, we propose a hybrid exposure technique for depth imaging in a ToF sensor so to improve the depth quality. Our method automatically determines an optimal depth for each pixel using two exposure conditions. To show that our algorithm is effective, we compare the proposed algorithm with two conventional methods in qualitative and quantitative manners showing the superior performance of proposed algorithm. © 2014 Optical Society of America.

Song C.Y.,Mokpo National University | Lee J.,Yonsei University
Probabilistic Engineering Mechanics | Year: 2011

This paper discusses reliability-based design optimization (RBDO) of an automotive knuckle component under bump and brake loading conditions. The probabilistic design problem is to minimize the weight of a knuckle component subject to stresses, deformations, and frequency constraints in order to meet the given target reliability. The initial design is generated based on an actual vehicle specification. The finite element analysis is conducted using ABAQUS, and the probabilistic optimal solutions are obtained via the moving least squares method (MLSM) in the context of approximate optimization. For the meta-modeling of inequality constraint functions, a constraint-feasible moving least squares method (CF-MLSM) is used in the present study. The method of CF-MLSM based RBDO has been shown to not only ensure constraint feasibility in a case where the meta-model-based RBDO process is employed, but also to require low expense, as compared with both conventional MLSM and non-approximate RBDO methods. © 2010 Elsevier Ltd. All rights reserved.

Yu S.M.,Samsung | Kim S.-L.,Yonsei University
IEEE Transactions on Wireless Communications | Year: 2014

In mobile communication services, users wish to subscribe to high-quality service at a low price level, which leads to competition between mobile network operators (MNOs). The MNOs compete with each other by service prices after deciding the extent of investment to improve quality of service. Unfortunately, the theoretic backgrounds of price dynamics are not known to us, and as a result, effective network planning and regulative actions are hard to make in the competitive market. To explain this competition in more detail, we formulate and solve an optimization problem applying the two-stage Cournot and Bertrand competition model. Consequently, we derive price dynamics that the MNOs increase and decrease their service prices periodically, which completely explains the subsidy dynamics in the real world. Moving forward, to avoid this instability and inefficiency, we suggest a simple regulation rule, which leads to a Pareto-optimal equilibrium point. Moreover, we suggest regulator's optimal actions corresponding to user welfare and the regulator's revenue. © 2014 IEEE.

Lee D.H.,Yonsei University | Joo Y.H.,Kunsan National University
IEEE Transactions on Fuzzy Systems | Year: 2014

In this paper, local stability and local stabilization problems are considered for discrete-time nonlinear systems represented by Takagi-Sugeno (T-S) fuzzy systems. Improved methods to assess the local stability, design locally stabilizing control laws, and estimate the domain of attraction are developed in terms of single-parameter minimization problems subject to linear matrix inequality (LMI) constraints. The improvement is achieved by applying a convergent LMI relaxation technique to prove positivity of homogeneous polynomial parameter-dependent matrices of arbitrary degree with variables in the simplex. We also take advantage of the recently developed parameter variation modeling technique to deal with the case that the variation rate of the membership functions of the T-S fuzzy systems is bounded and less than one. Finally, several illustrative examples demonstrate the validity and efficiency of the proposed method. © 1993-2012 IEEE.

Park S.,Korea Railroad Research Institute | Hong D.,Yonsei University
IEEE Transactions on Wireless Communications | Year: 2014

We consider energy harvesting cognitive radio networks to improve both energy efficiency and spectral efficiency. The goal of this paper is to analyze the theoretically achievable throughput of the secondary transmitter, which harvests energy from ambient sources or wireless power transfer systems while opportunistically accessing the spectrum licensed to the primary network. By modeling the temporal correlation of the primary traffic according to a time-homogeneous discrete Markov process, we derive the upper bound on the achievable throughput as a function of the energy arrival rate, the temporal correlation of the primary traffic, and the detection threshold for a spectrum sensor. The optimal detection threshold is then derived to maximize the upper bound on the achievable throughput under an energy causality constraint and a collision constraint. The energy causality constraint mandates that the total consumed energy should not exceed the total harvested energy, while the collision constraint is required to protect the primary network from secondary transmission. Analytical results show the temporal correlation of the primary traffic to enable efficient usage of the harvested energy by preventing the secondary transmitter from accessing the spectrum that may be occupied by the primary network. © 2002-2012 IEEE.

Yun S.,Xian University of Architecture and Technology | Lim S.,Yonsei University
Journal of Solid State Chemistry | Year: 2011

The application of electrospun nanofibers in electronic devices is limited due to their poor adhesion to conductive substrates. To improve this, a seed layer (SD) is introduced on the FTO substrate before the deposition of the electrospun composite nanofibers. This facilitates the release of interfacial tensile stress during calcination and enhances the interfacial adhesion of the AZO nanofiber films with the FTO substrate. Dye-sensitized solar cells (DSSC) based on these AZO nanofiber photoelectrodes have been fabricated and investigated. An energy conversion efficiency (η) of 0.540.55% has been obtained under irradiation of AM 1.5 simulated sunlight (100 mW/cm2), indicating a massive improvement of η in the AZO nanofiber film DSSCs after SD-treatment of the FTO substrate as compared to those with no treatment. The SD-treatment has been demonstrated to be a simple and facile method to solve the problem of poor adhesion between electrospun nanofibers and the conductive substrate. © 2010 Elsevier Inc. All rights reserved.

Postrenal transplantation diabetes mellitus (PTDM), or new-onset diabetes after organ transplantation, is an important chronic transplant-associated complication. Similar to type 2 diabetes, decreased insulin secretion and increased insulin resistance are important to the pathophysiologic mechanism behind the development of PTDM. However, β-cell dysfunction rather than insulin resistance seems to be a greater contributing factor in the development of PTDM. Increased age, family history of diabetes, ethnicity, genetic variation, obesity, and hepatitis C are partially accountable for an increased underlying risk of PTDM in renal allograft recipients. In addition, the use of and kinds of immunosuppressive agents are key transplant-associated risk factors. Recently, a number of genetic variants or polymorphisms susceptible to immunosuppressants have been reported to be associated with calcineurin inhibition-induced β-cell dysfunction. The identification of high risk factors of PTDM would help prevent PTDM and improve long-term patient outcomes by allowing for personalized immunosuppressant regimens and by managing cardiovascular risk factors.

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.

Kim H.-W.,Yonsei University | Gupta S.,Bhilai Institute of Technology | Koh J.,Chonnam National University
Information and Management | Year: 2011

Some social networking community service providers have earned revenue by selling digital items to their community members. We examined SNC member decisions to purchase digital items based on customer value theory. Six factors were extracted from three dimensions of customer value: functional, social, and emotional value. Our findings indicated that the effects of value on member purchase intentions were significant in terms of the emotional and social dimensions. Our results should help SNC providers by improving their sales of digital items. © 2011 Elsevier B.V. All rights reserved.

Recent political communication scholarship has examined whether social network sites (SNSs) contribute to political participation. Regarding SNSs' mobilization effect, however, mixed results have been reported. This study, relying on representative survey data from the 2012 South Korean general election, investigates interplay between three factors influencing electoral participation: (1) type of SNS use (i.e., political versus nonpolitical use), (2) user characteristics (i.e., past voters versus nonvoters), and (3) directionality of SNS messages (i.e., messages received from versus those sent to SNS friends). Results indicate SNSs' mobilization effect emerges when conditions are met. Voting intention is increased among past nonvoters who use SNSs through political messages received from their SNS friends. Theoretical and practical implications of SNSs' mobilization effect are discussed. © 2014 Elsevier Ltd. All rights reserved.

To investigate the role of focal adhesion kinase (FAK) in transforming growth factor (TGF)-β-induced myofibroblast transdifferentiation of human Tenon's fibroblasts. Primary cultured human Tenon's fibroblasts were exposed to TGF-β1 for up to 48 hours. The mRNA levels of FAK, α smooth muscle actin (αSMA), and β-actin were determined by quantitative real time reverse transcription polymerase chain reaction. The protein levels of collagen type I, FAK, phospho-FAK, αSMA, and β-actin were determined by Western immunoblots. After the small interfering RNA targeting FAK (siRNA(FAK)) molecules were delivered into the cells, the expressions of αSMA proteins were determined by Western immunoblots. In human Tenon's fibroblasts, TGF-β1 significantly increased the mRNA and protein expressions of αSMA. However, when the action of FAK was inhibited using siRNA(FAK), the TGF-β1-induced expression of αSMA was attenuated. Our data suggest that FAK may be associated with the TGF-β1-induced transdifferentiation of human Tenon's fibroblasts to myofibroblasts, which is the essential step of subconjunctival fibrosis.

PURPOSE:: The aim of this study was to report a lattice corneal dystrophy (LCD) family with a novel mutation of A620P in the TGFBI gene, its long-term treatment, follow-up data, and related pathologic findings.METHODS:: A total of 28 family members were clinically examined, and blood samples or buccal epithelial cells were taken for DNA analysis. All exons from the entire TGFBI gene coding region were analyzed for mutations in 3 affected members. Exon 14 was amplified in other family members and in 100 normal Korean persons as control. Corneal tissues from 1 affected family member were examined using light and electron microscopy.RESULTS:: Clinical examination revealed relatively late-onset LCD with asymmetric progression and recurrent corneal erosion. The affected family members have been treated with penetrating keratoplasty, deep lamellar keratoplasty, and phototherapeutic keratectomy for up to 19 years. Screening of the TGFBI gene revealed a novel A620P mutation, which was found in all affected members. The amyloid origin of deposits was confirmed by Congo red and was also partially stained with Masson trichrome. Although there were no electron-dense bodies as in granular dystrophy, transmission electron microscopy demonstrated that the stromal deposits were not homogenous and contained a variety of constituents with different electron densities.CONCLUSIONS:: We present the characteristics and surgical treatment of corneas with a novel A620P mutation in TGFBI showing LCD type IIIA with hyaline component. © 2014 by Lippincott Williams & Wilkins.

Gatta G.D.,University of Milan | Lee Y.,Yonsei University
Mineralogical Magazine | Year: 2014

This is a review of the elastic behaviour and pressure (P)-induced structural evolution of zeolites and presents a comparative analysis of the deformation mechanisms of the Si/Al-framework and the rearrangement of the extra-framework species in response to applied pressure. The interaction between P-transmitting fluids and zeolites, which can lead to phenomena such as P-induced over-hydration, is described. The comparative elastic analysis and the high-P structural data of zeolites reported so far allow us to make some generalizations: (1) The range of compressibility among this class of openframework silicates is large, with bulk moduli ranging between 15 and 70 GPa; (2) Microporosity does not necessarily imply high compressibility, as several zeolites are less compressible than other nonzeolitic rock-forming minerals; (3) Compressibilities of zeolites do not seem to be directly related to microporosity, at least if we model microporosity with the framework density; (4) The flexibility observed in zeolites under hydrostatic compression is mainly governed by tilting of rigid tetrahedra around O atoms that behave as hinges within the framework. Pressure-induced tilting commonly leads to continuous rearrangement of the framework without any phase transition. More rarely, tilting induces displacive phase transitions and isothermal P-induced reconstructive phase transitions (i.e. with change in framework topology), have not been reported in this class of materials; (5) Deformation mechanisms in response to applied pressure are generally dictated by the topological configuration of the framework rather than the Si/Al-distribution or the extra-framework content. The channel content governs the compressibility of the cavities, leading to different unit-cell-volume compressibilities in isotypic structures. © 2014 The Mineralogical Society.

Park J.,Yonsei University | Palmer M.H.,University of North Carolina at Chapel Hill
Journal of the American Geriatrics Society | Year: 2015

Objectives To identify factors associated with incomplete bladder emptying in older women with overactive bladder (OAB) symptoms. Design Retrospective medical records review. Setting Urodynamic laboratory at a large academic health care system in the southeast United States. Participants Medical records from women aged 65 and older who presented to clinic with OAB symptoms and who had completed outpatient urodynamic testing (N = 203). Measurements Three cutoff values of postvoid residual (PVR) volume (100, 150, 200 mL) were created a priori to classify incomplete bladder emptying. Age; vaginal parity; diabetes mellitus (DM); and a history of cerebrovascular accident, back surgery or injury, pelvic surgery, anti-urinary incontinence surgery, and pelvic organ prolapse were included in univariate and multivariate logistic regression models to determine factors associated with incomplete bladder emptying. Results When PVR volume of 200 mL or greater was used to define incomplete bladder emptying, history of back surgery or injury (odds ratio (OR) = 4.30, 95% confidence interval (CI) = 1.16-15.91) and pelvic surgery (OR = 4.42, 95% CI = 1.51-12.95) were significantly associated with incomplete bladder emptying in multivariate analysis. No factors were significantly associated with PVR volumes of 100 mL or greater or 150 mL or greater. Conclusion PVR volumes should be assessed in older women with OAB symptoms and a history of back surgery or injury or pelvic surgery, especially before the administration of antimuscarinic medications. Caution in interpreting these findings is needed because PVR volumes obtained from pressure-flow studies may differ from those obtained from natural voiding. Lack of data on medications that can contribute to incomplete bladder emptying and the small number of women with cerebrovascular accident, back surgery or injury, and DM may have influenced the results. © 2015 The American Geriatrics Society.

Qamar M.,King Fahd University of Petroleum and Minerals | Khan A.,Yonsei University
RSC Advances | Year: 2014

The synthesis of flower-like hierarchical bismuth tungstate (Bi 2WO6) consisting of a mesoporous surface was carried out by a hydrothermal method using the non-ionic surfactant Pluronic F127. The mesoporous and hierarchical surface of the bismuth tungstate was further modified with platinum nanoparticles and the photocatalytic activity was evaluated by studying the removal of rhodamine B under visible light (>420 nm). The effect of synthesis temperature and platinum amount on the photocatalytic activity was investigated and resulting photocatalytic activity of Pt/Bi2WO6 was compared with other visible-light- responsive photocatalysts, namely Pt/WO3, N-doped TiO2 and Pt/N-doped TiO2. Photoelectrochemical studies were performed to shed light on the involvement of excited charged carriers in the photooxidation of rhodamine B and a plausible mechanism was proposed based on the photocatalytic and photoelectrochemical behaviour of the catalysts. © 2014 The Royal Society of Chemistry.

Lee K.,Yonsei University
BMB reports | Year: 2012

Many malignant tumors become resistant to tumor necrosis factor-alpha (TNF-α)-induced cell death during carcinogenesis. In the present study, we examined whether parkin acts as a tumor suppressor in HeLa cells, a human cervical cancer cell line resistant to TNF-α-induced cell death. TNF-α-treatment alone did not affect HeLa cell viability. However, expression of parkin restored TNF-α-induced apoptosis in HeLa cells. Increased cell death was due to the activation of the apoptotic pathway. Expression of parkin in TNF-α-treated HeLa cells stimulated cleavage of the pro-apoptotic proteins caspase-8, -9, -3, -7 and poly ADP ribose polymerase (PARP). In addition, parkin expression resulted in decreased expression of the caspase inhibitory protein, survivin. These results suggest that parkin acts as a tumor suppressor in human cervical cancer cells by modulating survivin expression and caspase activity. We propose that this pathway is a novel molecular mechanism by which parkin functions as a tumor suppressor.

Kim H.-S.,Yonsei University
Asian Spine Journal | Year: 2014

Until now because there are many published journals with a variety of opinions so I will stratify these articles by giving weighted value on grade evaluation which depend on each institution (written author and co-authors) and external evaluate status (SCI, SCIE,impact factor) rather than the outcomes provided by each article. Consequently, before evaluating publicized papers, study quality assessment of each interesting paper should be performed by mean of gauging the quality of evidence. Reviewing these articles, a grade of medical literature was divided into the following 5 levels as level I (randomized controlled study), level II (non-randomized controlled study), level III (case-control study), level IV (case series), and level V (expert opinions). However, in present article I concluded only involved medical literatures with weighted value of level I and II evidence.

High mobility metal-oxide-semiconductor-field-effect-transistors (MOSFETs) are demonstrated on high quality epitaxial Si0.75Ge0.25 films selectively grown on Si (100) substrates. With a Si cap processed on Si0.75Ge0.25 channels, HfSiO2 high-k gate dielectrics exhibited low C-V hysteresis (<10 mV), interface trap density (7.5 × 1010), and gate leakage current (∼10-2A/cm2 at an EOT of 13.4 Å), which are comparable to gate stack on Si channels. The mobility enhancement afforded intrinsically by the Si0.75Ge0.25 channel (60%) is further increased by a Si cap (40%) process, resulting in a combined ∼100% enhancement over Si channels. The Si cap process also mitigates the low potential barrier issues of Si0.75Ge0.25 channels, which are major causes of the high off-state current of small band gap energy Si0.75Ge0.25 pMOSFETs, by improving gate control over the channel. © 2013 Elsevier B.V. All rights reserved.

Lee E.J.,Seoul National University | Kim T.-W.,Seoul National University | Kim M.,Konyang University | Kim H.,Yonsei University
Ophthalmology | Year: 2015

Objective To determine whether lamina cribrosa (LC) depth (LCD) and LC thickness (LCT) are associated with a faster rate of progressive retinal nerve fiber layer (RNFL) thinning in primary open-angle glaucoma (POAG). Design Prospective, observational study. Participants One hundred ten eyes diagnosed with POAG (n = 110 patients) in which RNFL thickness had been measured by serial spectral-domain (SD) optical coherence tomography (OCT) for at least 2.5 years. Methods The participants underwent enhanced depth imaging volume scanning of the optic nerve, and circumpapillary RNFL thickness measurements were obtained using SD OCT. The participants were followed up regularly with serial RNFL thickness measurements at 6-month or longer intervals. Lamina cribrosa depth was measured at 7 equidistant planes and LCT was measured at 3 locations (superior midperipheral, midhorizontal, and inferior midperipheral). The rate of RNFL thinning was determined by linear regression of serial OCT RNFL thickness measurements over time. Main Outcome Measures Factors associated with the rate of OCT RNFL thinning. Results A faster rate of RNFL thinning was associated with disc hemorrhage during follow-up (P < 0.001), wider β-zone parapapillary atrophy with Bruch's membrane (P = 0.037), larger global RNFL thickness (P = 0.026), larger LCD (P < 0.001), and smaller LCT (P = 0.002). The association between LCD and the rate of RNFL thinning was explained better using a fractional polynomial model (R2 = 0.223) than a linear model (R2 = 0.134; P = 0.010). Davies' test revealed a statistically significant breakpoint for LCD (489.7 μm), above which a faster rate of global RNFL thinning was associated with a larger LCD. Conclusions A thinner LC and a larger LC displacement had a significant influence on the rate of progressive RNFL thinning. © 2015 American Academy of Ophthalmology.

Yi S.-W.,Catholic Kwandong University | Ohrr H.,Yonsei University
Cancer | Year: 2014

CONCLUSIONS: Exposure to Agent Orange several decades earlier may increase the risk of cancers in all sites combined, as well as several specific cancers, among Korean veterans of the Vietnam War, including some cancers that were not found to be clearly associated with exposure to Agent Orange in previous cohort studies primarily based on Western populations.BACKGROUND: During the Vietnam War, US and allied military sprayed approximately 77 million liters of tactical herbicides including Agent Orange, contaminated with 2,3,7,8-tetrachlorodibenzo-p-dioxin. To the authors' knowledge, few studies to date have examined the association between Agent Orange exposure and cancer incidence among Korean veterans who were exposed to Agent Orange during the Vietnam War.METHODS: An Agent Orange exposure index, based on the proximity of the veteran's military unit to the area that was sprayed with Agent Orange, was developed using a geographic information system-based model. Cancer incidence was followed for 180,251 Vietnam veterans from 1992 through 2003.RESULTS: After adjustment for age and military rank, high exposure to Agent Orange was found to significantly increase the risk of all cancers combined (adjusted hazards ratio [aHR], 1.08). Risks for cancers of the mouth (aHR, 2.54), salivary glands (aHR, 6.96), stomach (aHR, 1.14), and small intestine (aHR, 2.30) were found to be significantly higher in the high-exposure group compared with the low-exposure group. Risks for cancers of all sites combined (aHR, 1.02) and for cancers of the salivary glands (aHR, 1.47), stomach (aHR, 1.03), small intestine (aHR, 1.24), and liver (aHR, 1.02) were elevated with a 1-unit increase in the exposure index. © 2014 American Cancer Society.

Kalab P.,U.S. National Cancer Institute | Soderholm J.,Yonsei University
Methods | Year: 2010

The application of FRET-based molecular biosensors provided confirmation of the central model of Ran GTPase function and led to important new insights into its physiological role. In many fields of cell biology, methods employing FRET are a standard approach that is becoming increasingly accessible due to advances in instrumentation and available fluorophores. However, the optimal design of a FRET sensor remains to be the cornerstone of any successful FRET application. Utilizing the recent literature on FRET applications and our studies on Ran, we outline the basic considerations involved in designing molecular FRET sensors. We point to several broadly applicable principles that were used in many different FRET sensors that can detect a wide range of molecular events. Using the FRET sensors for Ran that we created as examples, we then focus on the practical aspects of FRET assays. We describe the preparation of a bipartite FRET sensor consisting of ECFP-Ran and EYFP-importin β and its validation as a reporter for FRET-based high throughput screening in small molecule libraries. Finally, we review the design and optimization of monomolecular FRET sensors that monitor the RanGTP-RanBP1 interaction, and of sensors detecting the RanGTP-regulated importin β cargo release.

Jung H.,Yonsei University | Gkogkas C.G.,University of Edinburgh | Sonenberg N.,McGill University | Holt C.E.,University of Cambridge
Cell | Year: 2014

The subcellular position of a protein is a key determinant of its function. Mounting evidence indicates that RNA localization, where specific mRNAs are transported subcellularly and subsequently translated in response to localized signals, is an evolutionarily conserved mechanism to control protein localization. On-site synthesis confers novel signaling properties to a protein and helps to maintain local proteome homeostasis. Local translation plays particularly important roles in distal neuronal compartments, and dysregulated RNA localization and translation cause defects in neuronal wiring and survival. Here, we discuss key findings in this area and possible implications of this adaptable and swift mechanism for spatial control of gene function. © 2014 The Authors.

Kim H.,Yonsei University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011

There has been much work on explaining Hawking radiation as a quantum tunneling process through horizons. Basically, this intuitive picture requires the calculation of the imaginary part of the action for outgoing particle. And two ways are known for achieving this goal: the null-geodesic method and the Hamilton-Jacobi method. We apply these methods to the charged black holes in 2D dilaton gravity which is originated from the low energy effective theory of type 0A string theory. We derive the correct Hawking temperature of the black holes including the effect of the back reaction of the radiation, and obtain the entropy by using the 1st law of black hole thermodynamics. For fixed-charge ensemble, the 0A black holes are free of phase transition and thermodynamically stable regardless of mass-charge ratio. We show this by interpreting the back reaction term as the inverse of the heat capacity of the black holes. Finally, the possibility of the phase transition in the fixed-potential ensemble is discussed. © 2011 Elsevier B.V.

Hyun D.C.,Georgia Institute of Technology | Levinson N.S.,Georgia Institute of Technology | Jeong U.,Yonsei University | Xia Y.,Georgia Institute of Technology
Angewandte Chemie - International Edition | Year: 2014

The nebulous term phase-change material (PCM) simply refers to any substance that has a large heat of fusion and a sharp melting point. PCMs have been used for many years in commercial applications, mainly for heat management purposes. However, these fascinating materials have recently been rediscovered and applied to a broad range of technologies, such as smart drug delivery, information storage, barcoding, and detection. With the hope of kindling interest in this incredibly versatile range of materials, this Review presents an array of aspects related to the compositions, preparations, and emerging applications of PCMs. PCMs on the rise: As a result of their sharp melting points and large heats of fusion during phase transition, phase-change materials (PCMs) have already found commercial use in thermal management. The vast potential of this class of fascinating materials has recently been tapped in a diverse array of high-tech applications such as controlled release, information storage, sensing/detection, and barcoding. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Son J.Y.,Pohang University of Science and Technology | Shin Y.-H.,University of Ulsan | Kim H.,Yonsei University | Jang H.M.,Pohang University of Science and Technology
ACS Nano | Year: 2010

In this study, a NiO RRAM nanocapacitor array was fabricated on a graphene sheet, which was on a Nb-doped SrTiO3 substrate containing terraces with a regular interval of about 100 nm and an atomically smooth surface. For the formation of the NiO RRAM nanocapacitor (Pt/NiO/graphene capacitor) array, an anodic aluminum oxide (AAO) nanotemplate with a pore diameter of about 30 nm and an interpore distance of about 100 nm was used. NiO and Pt were subsequently deposited on the graphene sheet. The NiO RRAM nanocapacitor had a diameter of about 30 ± 2 nm and a thickness of about 33 ± 3 nm. Typical unipolar switching characteristics of the NiO RRAM nanocapacitor array were confirmed. The NiO RRAM nanocapacitor array on graphene exhibited lower SET and RESET voltages than that on a bare surface of Nb-doped SrTiO3. © 2010 American Chemical Society.

The present study aimed to determine the effect of black soy peptide supplementation on glucose control in subjects with prediabetes (impaired fasting glucose or impaired glucose tolerance) and newly diagnosed type 2 diabetes mellitus (DM). In this double-blind, placebo-controlled study, subjects with prediabetes and type 2 DM were randomly assigned to the placebo control group or the black soy peptide intervention group. We determined fasting serum concentrations of glucose, hemoglobin A1c, insulin, and free fatty acids, performed a 2-hour postload glucose (2-hour PG) test, and compared serum lipid profiles before and after the 12-week supplementation. In particular, subjects with fasting glucose ≥ 110 mg/dL who consumed black soy peptides tended to have lower fasting glucose levels (two-tailed test, P =.098; one-tailed test, P =.049) and had a significant reduction in 2-hour PG level (two-tailed P =.012, one-tailed P =.006), compared with baseline levels. The changes in 2-hour PG levels were also statistically significant in the intervention group (-41.25 ± 13.67 mg/dL) compared with the placebo group (12.42 ± 9.80 mg/dL; two-tailed P =.015, one-tailed P =.008). In contrast, hemoglobin A1c levels were not significantly improved by the dietary intervention. In conclusion, black soy peptide supplementation may be beneficial for controlling fasting blood glucose levels and 2-hour PG levels.

Lee J.,Yonsei University
Seminars in Cell and Developmental Biology | Year: 2010

Under defined laboratory conditions, Naegleria gruberi undergo an amoeba-to-flagellate differentiation. During this differentiation, N. gruberi changes its shape from an amorphous amoeba to a regular shaped flagellate and forms de novo a flagellar apparatus, which is composed of two basal bodies, two flagella, a flagellar rootlet, and cytoplasmic microtubules. The entire process is accomplished within 2 h after initiation of differentiation and more than 95% of cells in the population undergo this differentiation. This rapid and synchronous differentiation of N. gruberi provides us with a unique system in which we can study the process of de novo basal body assembly. In this review, I summarize recent findings associated with de novo basal body assembly and propose a hypothesis to explain how N. gruberi assemble two basal bodies per cell, which is what happens in the majority of cells. © 2009 Elsevier Ltd. All rights reserved.

BACKGROUND:: This randomized trial evaluated the effect of intravenous patient-controlled analgesia (IV-PCA) based on fentanyl mixed with either propacetamol or an equivalent volume of normal saline on postoperative nausea and vomiting (PONV) in highly susceptible patients undergoing spinal surgery. MATERIALS AND METHODS:: One hundred eight nonsmoking female patients were randomly and evenly allocated to receive IV-PCA with either propacetamol (4 g) or normal saline mixed to fentanyl (20 μg/kg). Primary study outcome was PONV incidence at 24 hours postsurgery. Secondary outcomes were nausea severity, pain intensity (100-mm visual analog scale), use of rescue antiemetics and analgesics, patient satisfaction, and adverse events at 6, 12, and 24 hours postsurgery. RESULTS:: Postsurgery, the propacetamol versus normal saline group had lower PONV incidence at 24 hours (41% vs. 66%, P=0.011); pain intensity at rest and rescue analgesic requirements at 6 to 12 hours (30±15 vs. 41±19, P=0.008; and 25% vs. 49%, P=0.036, respectively) and at 12 to 24 hours (25±15 vs. 35±17, P=0.008; and 19% vs. 42%, P=0.044, respectively); and higher patient satisfaction score (6.4±1.4 vs. 5.7±1.8, P=0.028). CONCLUSIONS:: In patients undergoing spinal surgery and at risk of developing PONV, continuous IV-PCA based on propacetamol mixed to fentanyl, relative to fentanyl alone, effectively reduced the incidence of PONV, pain intensity at rest, and additional use of rescue analgesics with higher patient satisfaction. Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved

Emery C.R.,Yonsei University
Aggression and Violent Behavior | Year: 2011

This paper offers a critique of existing typologies of domestic violence and an alternative based upon fundamental sociological concepts. It argues that the etiology and trajectory of domestic violence is fundamentally different depending on contextual aspects of the intimate relationship. The three fundamental dimensions of context are relationship order, power structure and legitimacy. Four questions are used to classify violent acts: 1) Are there relationship norms? 2) Is power more or less shared or unequal? 3) If unequal, is the violent act by the subordinate or superordinate partner? 4) What is the relationship of the violent act to the relationship norms (Legitimacy)? Based on these four questions, acts of domestic violence are classified into Anarchic Acts, Acts of Violent Conflict, Acts of Insurrection, Acts of Retaliation, Acts of Inconsistent Control and Acts of Consistent Control. Knowledge of the classification of a particular violent act is a necessary but insufficient condition for classifying a type of domestic violence. Based on prevailing patterns of violent acts and which violent acts are present, five types of domestic violence are identified. The five types are: 1) Anarchic Type, 2) Violent Conflict, 3) Tolerant Dictatorship, 4) Despotic Dictatorship and 5) Totalitarian Dictatorship. © 2011 Elsevier Ltd.

Purpose - Social networking sites (SNSs) are gaining popularity in various areas. Library and information services also are attempting to utilize them for increasing the library user traffic. Considering the lack of SNS studies in academic library services and various SNS usage patterns according to user type, it is necessary to compare the usage patterns across different user groups. This paper thus aims to explore the usages of a SNS by different university users. Design/methodology/approach - Data were collected through semi-structured and open-ended interviews conducted with undergraduates, graduates, and faculty members at Yonsei University in Seoul, South Korea. Data were analyzed according to the three groups (undergraduates, graduates, and faculty members) and within each group SNS user perception and use were examined across the three different user activity groups (active users, semi-active users, and non-active users). Findings - The analyses indicated that the three groups of users demonstrated distinct patterns of SNS use. Although undergraduates used the profile service more than the community service, graduates used the community more than the profile service. Most faculty members were not active users. Six factors that affected these different usage patterns were identified: desire for expression, peer influences, familiarity with information technologies, sensitivity to privacy, nature of using the internet, and perception of the SNS. Practical implications - A differentiated approach is necessary for SNS-based academic library services. Originality/value - The paper makes useful and initial suggestions for implementing SNS-based library and information service in academic settings. © Emerald Group Publishing Limited 0264-0473.

Lee I.,Yonsei University
Progress in Biophysics and Molecular Biology | Year: 2011

A cellular system may be viewed as a social network of genes. Genes work together to conduct physiological processes in the cells. Thus if we have a view of the functional association among genes, we may also be able to unravel the association between genotypes and phenotypes; the emergent properties of interactive activities of genes. We could have various points of view for a gene network. Perhaps the most common standpoints are protein-protein interaction networks (PPIN) and transcriptional regulatory networks (TRN). Here I introduce another type of view for the gene network; the probabilistic functional gene network (PFGN). A 'functional view' of association between genes enables us to have a holistic model of the gene society. A 'probabilistic view' makes the model of gene associations derived from noisy high-throughput data more robust. In addition, the dynamics of gene association may be presented in a single static network model by the probabilistic view. By combining the two modeling views, the probabilistic functional gene networks have been constructed for various organisms and proved to be highly useful in generating novel biological hypotheses not only for simple unicellular microbes, but also for highly complex multicellular animals and plants. © 2011 Elsevier Ltd.

Lee T.,Yonsei University | Van De Meene S.,Transformative Frameworks Consulting
Journal of Cleaner Production | Year: 2013

This study examines the factors that explain cross-sectional variations in per capita emissions of one of the primary greenhouse gases (GHGs), carbon dioxide (CO2), in major Asian cities. Why do individuals in Bangkok, Thailand, produce an average of 6.1 tons of carbon dioxide annually, but individuals in Shanghai emit 9.7 tons of CO2? Why do CO2 emissions per capita vary across twenty-two major Asian cities? To what extent are relevant environmental indicators associated with CO2 emissions? To answer these questions, we begin by reviewing the climate co-benefits of existing environmental indicators (waste, green space, water, public transport and energy use) and climate change. Based on a literature review, we hypothesize that cities with higher resource use and wealth will have higher CO2 per capita emissions. To test the hypotheses, we analyze the relationship between tentative co-benefits of existing environmental indicators and CO 2 emissions per capita using regression analysis. We find that a city's energy inefficiency, waste generation per capita, and GDP per capita are positively associated with CO2 emissions per capita, while we control for a battery of variables such as population and industrial structure. Our findings suggest that enhancing energy efficiency and reducing waste generation are effective ways to mitigate climate change while also realizing climate co-benefits. © 2013 Elsevier Ltd. All rights reserved.

Min S.O.,Yonsei University
The Korean journal of hepatology | Year: 2011

Ischemic preconditioning (IP) decreases severity of liver necrosis and has anti-apoptotic effects in previous studies using liver regeneration in normal rats. This study assessed the effect of IP on liver regeneration after hepatic resection in cirrhotic rats. To induce liver cirrhosis, thioacetamide (300 mg/kg) was injected intraperitoneally into Sprague-Dawley rats twice per week for 16 weeks. Animals were divided into four groups: non-clamping (NC), total clamping (TC), IP, and intermittent clamping (IC). Ischemic injury was induced by clamping the left portal pedicle including the portal vein and hepatic artery. Liver enzymes alanine transaminase (ALT) and aspartate aminotransferase (AST) were measured to assess liver damage. Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) staining for apoptosis and proliferating cell nuclear antigen (PCNA) staining for cell replication were also performed. Day-1 ALT and AST were highest in IP, however, levels in NC and IC were comparably low on days 1-7. There was no significant correlation of AST or ALT with experimental groups (P=0.615 and P=0.186). On TUNEL, numbers of apoptotic cells at 100× magnification (cells/field) were 31.8±24.2 in NC, 69.0±72.3 in TC, 80.2±63.1 in IP, and 21.2±20.8 in IC (P<0.05). When regeneration capacity was assessed by PCNA staining, PCNA-positive cells (cells/field) at 400× were 3.4±6.0 in NC, 16.9±69 in TC, 17.0±7.8 in IP and 7.4±7.6 in IC (P<0.05). Although regeneration capacity in IP is higher than IC, the liver is vulnerable to ischemic damage in cirrhotic rats. Careful consideration is needed in applying IP in the clinical setting.

Baek J.,Yonsei University
Physics in medicine and biology | Year: 2013

We examine the noise advantages of having a computed tomography (CT) detector whose spatial resolution is significantly better (e.g. a factor of 2) than needed for a desired resolution in the reconstructed images. The effective resolution of detectors in x-ray CT is sometimes degraded by binning cells because the small cell size and fine sampling are not needed to achieve the desired resolution (e.g. with flat panel detectors). We studied the effect of the binning process on the noise in the reconstructed images and found that while the images in the absence of noise can be made identical for the native and the binned system, for the same system MTF in the presence of noise, the binned system always results in noisier reconstructed images. The effect of the increased noise in the reconstructed images on lesion detection is scale (frequency content) dependent with a larger difference between the high resolution and binned systems for imaging fine structure (small objects). We show simulated images reconstructed with both systems for representative objects and quantify the impact of the noise on the detection of the lesions based on mathematical observers. Through both subjective assessment of the reconstructed images and the quantification using mathematical observers, we show that for a CT system where the photon noise is dominant, higher resolution in the detectors leads to better noise performance in the reconstructed images at any resolution.

Lee S.-K.,Yonsei University
Neuroimaging Clinics of North America | Year: 2012

Diffusion tensor imaging (DTI) and perfusion-weighted imaging (PWI) are essential tools for diagnosing, differentiating, and monitoring brain tumors. High-field MRI provides higher signal-to-noise ratio, shorter scan time, and better image quality. One-stop multiparametric study, including DTI and PWI, is possible with high-field MRI in brain tumors. DTI can be used for assessing spatial relationship between major white matter tract and tumor, differentiating gliomas from nonglial tumors, and postoperative evaluation. PWI provides reliable biomarkers for glioma grading, therapeutic responses, and differential diagnosis of various brain tumors. With higher field strength, better-quality DTI and PWI can raise the diagnostic accuracy in brain tumors. © 2012 Elsevier Inc.

Lee D.H.,Yonsei University
Proceedings of the IEEE Conference on Decision and Control | Year: 2012

This paper proposes a strategy to estimate invariant subsets of the domain of attraction (DA) for continuous-time Takagi-Sugeno (T-S) fuzzy systems. The result is based on the so-called fuzzy Lyapunov function, which is used to characterize the subsets of the DA as sublevel sets of the Lyapunov function. The key idea relies on casting the Lyapunov inequality that includes the time-derivative of the membership functions into linear matrix inequalities (LMIs) by considering a bound on the nonlinear function dependent quadratically on the time-derivative of the membership functions. Finally, an example is given to demonstrate the effectiveness of the proposed approach. © 2012 IEEE.

Lee K.-S.,Yonsei University
Geospatial Health | Year: 2013

A methodology for evaluating and understanding how healthcare agencies are distributed within a city is provided. The study undertaken analysed the disparity in the spatial distribution of clinics within the metropolitan city of Daejeon, South Korea. Address and specialty of clinics in use were collected from five public health centres in 2010. Buffer analysis, hot-spot analysis, and generalized linear models were applied to the data collected. Multivariate analysis was also conducted on data collected in 2008 from the annual records of five ward offices (mid-level city administration units) taking the lowest administrative level of the city (the dong) into account. Buffer analysis showed that numerous clinics were located near major roads, while the hot-spot analysis identified three areas with concentrations of clinics and one area with hardly any clinics. The results of the generalized linear models showed variations depending on the specialty of the clinics suggesting that their distribution differed depending on specialty. There are no current regulations in force governing clinic location. Policy makers should consider improving the clinic distribution taking their speciality into account.

Lee S.K.,Yonsei University
The Korean journal of gastroenterology = Taehan Sohwagi Hakhoe chi | Year: 2012

Probiotics are live non-pathogenic organisms that belong to the resident microflora, and confer health benefits by multiple mechanisms. Lactobacillus rhamnosus GG (LGG) is one of the probiotic bacteria that ameliorates intestinal injury and inflammation caused by various stimuli. We aimed to evaluate the anti-inflammatory effect and mechanism of LGG in lipopolysaccharide (LPS)-stimulated HT-29 cells. HT-29 cells were stimulated with interleukin (IL)-1β (2 ng/mL), tumor necrosis factor (TNF)-α (20 ng/mL), and LPS (20 μg/mL) in the presence or absence of LGG (107-109 colony forming units/mL). Production of the pro-inflammatory chemokine IL-8 was measured by ELISA and semi-quantitative PCR. Transcriptional activity of NF-kB-responsive gene was evaluated by luciferase assay with reporter gene. Toll-like receptor 4 (TLR4) mRNA expression was assessed by semi-quantitative PCR. The IκBa degradation was evaluated by western blot and intranuclear translocation of NF-κB was determined by western blot and immunofluorescence. LGG did not affect the viability of HT-29 cells. Pretreatment of HT-29 cells with LGG significantly blocked TNF-α, and LPS induced IL-8 activation at both mRNA and protein level (p<0.05). Pretreatment of HT-29 cells with LGG attenuated LPS-induced NF-κB nuclear translocation and also blocked LPS-induced IκBα degradation. LGG also down-regulated TLR4 mRNA activated by LPS. LGG attenuates LPS induced inflammation, and this may be associated with TLR4/NF-κB down-regulation.

Targeted mRNA degradation by short interfering RNAs (siRNAs) offers a great potential to treat cancers. siRNA therapeutics for leukemias are, however, hindered by poor intracellular uptake, limited blood stability and nonspecific delivery. To solve these problems, we developed an anti-JL1 immunonanoplex (antibody-coupled nanocomplex) for siRNA delivery using anti-JL1 minibody (leukemia cell-specific minibody) conjugated to oligo-9-Arg peptide (9R) for effective siRNA delivery to leukemic cells. The anti-JL1 immunonanoplexes were able to deliver siRNA specifically to leukemic cells (CEM and Jurkat), but not to control cancer cells (H9). According to FACS and confocal microscopic analysis, siRNAs delivered by immunonanoplex particles were rapidly taken up by the JL1-positive cancer cells in 2 h. Furthermore, we showed that the anti-JL1 immunonanoplexes were effectively targeted to JL1-positive cells (CEM) inoculated in the mouse bone marrow. These results suggest that the anti-JL1 immunonanoplex is a powerful siRNA delivery system for human leukemia therapies.

Kim T.H.,Yonsei University
Molecules and cells | Year: 2010

The sulfation of tyrosine residues is an important post-translational modification involved in the regulation of protein function. We examined the activity of worm tyrosylprotein sulfotransferase (TPST-1) on a typical cuticle collagen, ROL-6, in C. elegans. We verified that TPST-1 sulfates three tyrosine residues of ROL-6 in vitro. We found that these tyrosine residues are important for the secretion of ROL-6::GFP. Mutant ROL-6::GFP proteins that contain more than two substitutions of the target tyrosine residues are severely deficient in cuticle localization. Consistently, knock down of tpst-1 blocked the cuticle localization of ROL-6::GFP. Therefore, the sulfation of ROL-6 by TPST-1 is critical for the proper localization of ROL-6. We also confirmed that worm TPST-1 is localized to the trans-Golgi network (TGN). Our results indicate that TPST-1 regulates cuticle organization by promoting the transport of ROL-6 from the TGN to the cuticle.

Spleen-preserving distal pancreatectomy can be performed safely and effectively by resecting both splenic vessels (Warshaw procedure). This simplified spleen-preserving technique might also be applied to minimally invasive distal pancreatectomy of benign and borderline malignant tumor. Although the conservation of both splenic vessels is paramount to preserving the spleen during laparoscopic distal pancreatectomy, preservation of the splenic vessels is not always possible, especially under the following conditions: (1) relatively large tumor, (2) associated with chronic pancreatitis, (3) tumor abutting splenic vascular structures, and (4) bleeding during the splenic vessel conserving procedure, which are potential indications of laparoscopic extended Warshaw procedure. Patient preparation and position was the same as that described in our previous study. During the study's time period, 38 consecutive patients underwent laparoscopic spleen-preserving distal pancreatectomy. Of those, five patients underwent a laparoscopic extended Warshaw procedure, which all included among 16 patients of extended distal pancreatectomy by dividing the pancreas at the pancreatic neck. All patients were women with a median age of 55 (range, 38-75) years. Median total operation time and blood loss were 215 (range, 200-386) minutes and 100 (range, 0-300) ml, respectively. The median length of hospital stay was 8 (range, 5-15) days. All of postoperative complications (two grade A and two grade B postoperative pancreatic fistula; one grade A bleeding) were able to be treated conservatively. During the median follow-up period of 11 (range, 7-42) months, one focal splenic infarction and one gastric varix were noted; however, no clinically significant complications were reported. Laparoscopic spleen-preserving extended distal pancreatectomy with resection of both the splenic vessels is feasible and safe. This surgical technique is thought to increase the chance of preservation of the spleen with minimally invasive distal pancreatectomy in well-selected benign or borderline malignant tumor of the distal pancreas.

Roh H.S.,Yonsei University
Korean journal of ophthalmology : KJO | Year: 2011

To compare the clinical manifestations between patients with ocular myasthenia gravis and those with generalized myasthenia gravis (MG). The medical records of 71 patients diagnosed with MG between January 1995 and December 2007 were reviewed. Demographics, sensitivities of diagnostic methods, the presence of systemic autoimmune diseases, ophthalmic complications caused by MG, and treatments were evaluated and compared. Fourteen patients (20%) were diagnosed with ocular MG and 57 patients (80%) with generalized MG. Sensitivities of anti-acetylcholine receptor antibody and repetitive nerve stimulation tests were significantly higher in the generalized MG group (84%, 89%) compared to those in the ocular MG group (50%, 54%) (p = 0.011, p = 0.008). The sensitivity of the neostigmine test was the highest in both groups (98% of generalized MG, 79% of ocular MG), and the difference between the two groups was borderline significant (p = 0.058). The most common symptoms were ptosis and diplopia, and both groups presented with pain, blurred vision, and tearing. Systemic autoimmune disease was more prominent in the generalized MG group (21%) than in the ocular MG group (14%), and steroid therapy was used more frequently in the generalized MG group (82%) than in the ocular MG group (57%). Ophthalmic complications associated with long-term steroid treatment were more profound in the generalized MG (30%) compared to those of the ocular MG (21%). The generalized MG group was associated with higher sensitivities to diagnostic tests, more systemic steroid use, higher ophthalmic complications caused by systemic autoimmune disease, and long-term steroid treatment compared to those of the ocular MG group.

Moon M.H.,Yonsei University
Mass Spectrometry Letters | Year: 2014

Lipids play important roles in biological systems; they store energy, play a structural role in the cell membrane, and are involved in cell growth, signal transduction, and apoptosis. Phospholipids (PLs) in particular have received attention in the medical and lipidomics research fields because of their involvement in human diseases such as diabetes, obesity, atherosclerosis, and many cancers associated with lipid metabolic disorders. Here I review experimental strategies for PL analysis based on nanoflow liquid chromatography- electrospray ionization-tandem mass spectrometry (nLC-ESI-MSn). In particular, discussed are lipid extraction methods, nanoflow LC separation of PLs, effect of ionization modifiers on the ESI of PLs, influence of chain lengths and unsaturation degree of acyl chains of PLs on MS intensity, structural determination of the molecular structure of PLs and their oxidized products, and quantitative profiling of PLs from biological samples such as tissue, urine, and plasma in relation to cancer and coronary artery disease.

Kim W.,Yonsei University
Materials Research Innovations | Year: 2011

Extensive research efforts have been devoted to nanowires because of their novel electronic, optical and thermoelectric properties due to spatial confinement in two dimensions. Among various fields, nanowires have been of interest in the thermoelectric community not only for their novel thermoelectric properties but also for their ease of use in fundamental scientific studies as the physics learned using nanowires can be applied in bulk thermoelectric nanocomposites. In this paper, we limit our discussion to experimental thermal transport in thermoelectric nanowires such as Bi-Te, Pb-Te and Si-Ge nanowires. After reviewing the reasons why nanowires are of interest in the thermoelectric community, we discuss various synthesis methods and thermal transport measurements. Next, we evaluated how thermal transport in nanowires is affected by various scattering mechanisms such as phonon boundary scattering, alloy scattering, etc. We also discuss a recent study concerning how the surface roughness affects phonon transport. This article is useful to gain insight into how to manage thermal transport in various applications. © 2011 W. S. Maney & Son Ltd.

Background: A short columella is one of the most severe problems in bilateral cleft lip and nose deformity. In particular, with tissue insufficiency or scar contracture on the upper lip, it is very hard to achieve a good nasal profile with conventional methods. Methods: One hundred thirty-seven patients with a short columella were operated on from February of 1987 to December of 2008. The average age at operation was 7.3 years. The conchal cartilage was harvested. The preauricular or postauricular skin-subcutaneous fat composite tissue was harvested. Through a transcolumellar incision, the conchal cartilage was inset and the defect was covered with skin-fat composite tissue. The serial nasal profiles were evaluated before and after surgery. Also, the postoperative nasal profiles were compared with normal profiles. The postoperative color difference with surrounding skin was measured by the L*a*b* photographic analysis method. Results: The mean height and width of skin-subcutaneous fat composite tissue were 9.81 and 22.14 mm, respectively. The preoperative and postoperative measuring for columella height was 5.1 ± 1.1 mm and 14.2 ± 1.5 mm. The columella-lip angle was 120.30 ± 12.97 preoperatively degrees and 98.76 ± 10.98 degrees postoperatively, whereas the angle of columellar-alar triangle was 111.56 ± 11.39 degrees and 97.91 ± 11.49 degrees, respectively. None of the postoperative profiles were different from those of normal Korean people of the same age except in the 0- to 6-year-old group (p < 0.05). The color match was best with preauricular composite tissue. Complications included total necrosis in three cases and partial necrosis in 12 cases that were treated conservatively. Conclusion: Elongating columella using a composite graft can be a satisfying alternative, especially for a severe short columella with upper lip tissue deficiency. Copyright © 2010 by the American Society of Plastic Surgeons.

Lee J.H.,Yonsei University
Korean journal of ophthalmology : KJO | Year: 2010

The purpose of this study is to identify risk factors for severe thyroid-associated orbitopathy (TAO) and compressive optic neuropathy in Korean patients. This study was a retrospective comparative case series. All TAO patients who were first seen at our institution between 2005 and 2009 and who had follow-up periods of at least 6 months were included. Patients were divided into mild or moderate and severe TAO groups. Cases were also segregated based on the presence or absence of optic neuropathy. Demographics, smoking status, comorbidities, thyroid hormonal status, thyroid autoantibody levels, and clinical presentations were assessed. A total of 99 patients (83 with mild to moderate courses and 16 with severe courses; 90 without optic neuropathy and 9 with optic neuropathy) were included in this study. On multiple logistic regression analysis, smoking status was a predictive risk factor for a severe course of TAO and the development of optic neuropathy (odds ratios = 6.57 and 10.00, respectively). Other factors such as age, gender, free T4 level, thyroid binding-inhibiting immunoglobulin, and a history of diabetes were not predictive of severe TAO or optic neuropathy. Although various factors may influence the severity of TAO and the development of optic neuropathy, this study showed that smoking was a risk factor for severe TAO and the development of optic neuropathy. Therefore, it is important for patients with Graves' disease to refrain from smoking. Frequent and careful observation should also be performed in current smokers, as TAO patients who smoke are susceptible to a severe course and/or optic neuropathy.

Kim S.H.,Yonsei University | Saver J.L.,University of California at Los Angeles
Stroke | Year: 2015

Results-Among 595 patients (297 placebo and 298 tPA treated) with documented initial BT, 77.1% had initial BT <37.0°C and 22.9% 37.0°C. Patients with higher initial BT had lower baseline stroke severity in both tPA-treated patients (the National Institute of Health Stroke Scale median, 11 versus 15; P=0.05) and placebo-treated patients (median, 13 versus 16; P<0.01). Patients with higher initial BT also had lower infarction volume on computed tomography at 3 months in both tPA-treated patients (median, 9.6 versus 16.7 cm; P=0.08) and placebo-treated patients (median, 13.1 versus 28.1 cm; P=0.02), but no clinical outcome differences. Analysis of lytic treatment effect found no heterogeneity in the degree of tPA benefit in both higher and lower BT groups (37.0°C: odds ratio for the modified Rankin Scale 0-1 outcome, 2.55; 95% confidence interval, 1.05-6.21 and <37.0°C: odds ratio, 2.30; 95% confidence interval, 1.38-3.84; heterogeneity P=0.83).Conclusions-In patients with hyperacute stroke, higher presenting temperatures are associated with less severe neurological deficits and reduced final infarct volumes. Presenting temperature does not modify the benefit of tPA on 3-month favorable outcome.Background and Purpose-Body temperature (BT) is an important physiological factor in acute ischemic stroke. However, the relationship of initial BT to stroke severity and degree of benefit from thrombolytic therapy has been delineated incompletely.Methods-We analyzed the public data set of the 2 National Institute of Neurological Disorders and Stroke Tissue-Type Plasminogen Activator (tPA) stroke trials, comparing patients with lower (<37.0°C) and higher (37.0°C) presenting BT. © 2014 American Heart Association, Inc.

Kim M.Y.,Yonsei University
Clinical and molecular hepatology | Year: 2013

While gastric variceal bleeding (GVB) is not as prevalent as esophageal variceal bleeding, it is reportedly more serious, with high failure rates of the initial hemostasis (>30%), and has a worse prognosis than esophageal variceal bleeding. However, there is limited information regarding hemostasis and the prognosis for GVB. The aim of this study was to determine retrospectively the clinical outcomes of GVB in a multicenter study in Korea. The data of 1,308 episodes of GVB (males:females=1062:246, age=55.0±11.0 years, mean±SD) were collected from 24 referral hospital centers in South Korea between March 2003 and December 2008. The rates of initial hemostasis failure, rebleeding, and mortality within 5 days and 6 weeks of the index bleed were evaluated. The initial hemostasis failed in 6.1% of the patients, and this was associated with the Child-Pugh score [odds ratio (OR)=1.619; P<0.001] and the treatment modality: endoscopic variceal ligation, endoscopic variceal obturation, and balloon-occluded retrograde transvenous obliteration vs. endoscopic sclerotherapy, transjugular intrahepatic portosystemic shunt, and balloon tamponade (OR=0.221, P<0.001). Rebleeding developed in 11.5% of the patients, and was significantly associated with Child-Pugh score (OR=1.159, P<0.001) and treatment modality (OR=0.619, P=0.026). The GVB-associated mortality was 10.3%; mortality in these cases was associated with Child-Pugh score (OR=1.795, P<0.001) and the treatment modality for the initial hemostasis (OR=0.467, P=0.001). The clinical outcome for GVB was better for the present cohort than in previous reports. Initial hemostasis failure, rebleeding, and mortality due to GVB were universally associated with the severity of liver cirrhosis.

Riechelmann T.,Leibniz University of Hanover | Noh Y.,Yonsei University | Raasch S.,Leibniz University of Hanover
New Journal of Physics | Year: 2012

In this paper, a new Lagrangian cloud model (LCM) is introduced in which the flow field is simulated by large-eddy simulation, and the droplets are treated as Lagrangian particles responding to the simulated flow field. In order to handle the extremely large number of droplets within a cloud, the concept of a super-droplet, which represents a large number of real droplets of the same size, is introduced, and the number of contributing real droplets is called the weighting factor. A novel method is developed to realize the collision/coalescence of droplets, in which the consequent variation of the droplet spectrum is represented in terms of the modification of the radius and weighting factor of super-droplets, while keeping the number of super-droplets unchanged. Using an idealized single cloud and trade wind cumuli, the LCM is shown to reproduce the general features of shallow cumulus clouds in agreement with traditional bulk models. The droplet spectrum simulated by the LCM, using collision kernels with and without the effects of turbulence, also shows a pattern consistent with the spectral bin model. Furthermore, the sensitivity of the LCM to two model parameters, the time step and the number of super-droplets, is examined. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Kim E.,Yonsei University
Nucleic acids research | Year: 2013

Revolutionary DNA sequencing technology has enabled affordable genome sequencing for numerous species. Thousands of species already have completely decoded genomes, and tens of thousands more are in progress. Naturally, parallel expansion of the functional parts list library is anticipated, yet genome-level understanding of function also requires maps of functional relationships, such as functional protein networks. Such networks have been constructed for many sequenced species including common model organisms. Nevertheless, the majority of species with sequenced genomes still have no protein network models available. Moreover, biologists might want to obtain protein networks for their species of interest on completion of the genome projects. Therefore, there is high demand for accessible means to automatically construct genome-scale protein networks based on sequence information from genome projects only. Here, we present a public web server, JiffyNet, specifically designed to instantly construct genome-scale protein networks based on associalogs (functional associations transferred from a template network by orthology) for a query species with only protein sequences provided. Assessment of the networks by JiffyNet demonstrated generally high predictive ability for pathway annotations. Furthermore, JiffyNet provides network visualization and analysis pages for wide variety of molecular concepts to facilitate network-guided hypothesis generation. JiffyNet is freely accessible at http://www.jiffynet.org.

Bae J.M.,Cutaneous Biology Research Institute | Choi Y.Y.,Severance Hospital | Park C.O.,Cutaneous Biology Research Institute | Chung K.Y.,Cutaneous Biology Research Institute | And 2 more authors.
Journal of Allergy and Clinical Immunology | Year: 2013

Background: Allergen-specific immunotherapy (allergen-SIT) is the only treatment directed at the cause of IgE-mediated allergic diseases. However, there is controversy over the use of SIT for patients with atopic dermatitis. Objective: We performed a systematic review and meta-analysis to assess the efficacy of SIT for patients with atopic dermatitis. Methods: We performed manual searches of reference lists and computerized searches of the MEDLINE, EMBASE, CINAHL, Web of Science, and Cochrane databases (through December 10, 2012) for randomized controlled trials that compared SIT with placebo for patients with atopic dermatitis. The outcome of interest was a dichotomous variable, in terms of treatment success; a meta-analysis was performed by using a randomeffects analysis. Subgroup analyses were carried out to evaluate the effects of long-term treatment (more than 1 year), SIT for severe atopic dermatitis, SIT for children, and subcutaneous and sublingual administration of immunotherapy. Results: We analyzed 8 randomized controlled trials that comprised a total of 385 subjects. We found that SIT has a significant positive effect on atopic dermatitis (odds ratio [OR], 5.35; 95% CI, 1.61-17.77; number needed to treat, 3; 95% CI, 2-9). SIT also showed significant efficacy in long-term treatment (OR, 6.42; 95% CI, 1.50-27.52) for patients with severe atopic dermatitis (OR, 3.13; 95% CI, 1.31-7.48), and when administered subcutaneously (OR, 4.27; 95% CI, 1.36-13.39). Conclusions: A meta-analysis provides moderate-level evidence for the efficacy of SIT against atopic dermatitis. However, these findings are based on an analysis of a small number of randomized controlled trials, with considerable heterogeneity among trials. © 2013 American Academy of Allergy, Asthma &Immunology.

Hong T.-K.,Yonsei University
Journal of Seismology | Year: 2013

Seismic discrimination of an underground nuclear explosion (UNE) based on regional waveforms in continental margins is challenging due to large variations among waveforms. The 2009 North Korean UNE test was conducted in the far eastern Eurasian plate. The UNE was recorded by densely-located regional seismic stations, and regional waveforms exhibit highly path-dependent amplitude and arrival time features due to complex crustal structures. Regional source spectra are calculated by correcting for the path effects on the waveforms. A two-step approach is proposed for stable inversion of source-spectral parameters and path parameters. Characteristic overshoot features are observed in the source spectra, particularly strong in Pn. The path parameter, Q, is determined uniquely regardless of the source-spectral model implemented, which suggests stable separation of path effects from waveform records. The estimated source spectra fit well to a theoretical UNE source-spectral model. The fitness between the estimated and theoretical source-spectral models allows us to discriminate UNEs from natural earthquakes. Also, the P/S source-spectral ratio is observed to be an effective discriminant of UNE. © 2012 Springer Science+Business Media Dordrecht.

Sagong S.,Agency for Defense Development | Lee J.,Massachusetts Institute of Technology | Hong D.,Yonsei University
IEEE Transactions on Wireless Communications | Year: 2011

This paper evaluates the capacity of the reactive decode-and-forward (R-DF) scheme, which considers the reduced relay candidates based on the signal-to-noise ratio (SNR) of the source-relay link for relay selection in underlay cognitive relay networks. The performance of R-DF scheme is compared with that of the proactive DF (P-DF) scheme. It has been proven that R-DF scheme achieves the similar capacity of P-DF scheme as the primary receiver is located further from the secondary source. Since the transmission power of a secondary user is constrained by the location of the primary receiver, the performance of a cognitive relay network varies depending on the considered link for determining the relay candidates, between the source-relay and the relay-destination links. Hence, we also analyze the performance of the backward R-DF (BR-DF) scheme which the relay candidates are determined based on the relay-destination link. It is also verified that the performance of BR-DF scheme is better than that of R-DF scheme when the primary receiver is located close to the secondary source. © 2011 IEEE.

Huang K.,Yonsei University | Zhang R.,Institute for Infocomm Research | Zhang R.,National University of Singapore
IEEE Transactions on Signal Processing | Year: 2011

Cognitive beamforming (CB) is a multiantenna technique for efficient spectrum sharing between primary users (PUs) and secondary users (SUs) in a cognitive radio network. Specifically, a multiantenna SU transmitter applies CB to suppress the interference to the PU receivers as well as enhance the corresponding SU-link performance. In this paper, for a multiple-input-single- output (MISO) SU channel coexisting with a single-input-single-output (SISO) PU channel, we propose a new and practical paradigm for designing CB based on the finite-rate cooperative feedback from the PU receiver to the SU transmitter. Specifically, the PU receiver communicates to the SU transmitter the quantized SU-to-PU channel direction information (CDI) for computing the SU transmit beamformer, and the interference power control (IPC) signal that regulates the SU transmission power according to the tolerable interference margin at the PU receiver. Two CB algorithms based on the PU's cooperative feedback are proposed: one restricts the SU transmit beamformer to be orthogonal to the quantized SU-to-PU channel direction and the other relaxes such a constraint. In addition, cooperative feedforward of the SU CDI from the SU transmitter to the PU receiver is exploited to allow more efficient cooperative feedback from the PU receiver. The outage probabilities of the SU link for different cooperative feedback/feedforward algorithms are analyzed, from which the optimal bit-allocation tradeoff between the CDI and IPC feedback is characterized. © 2006 IEEE.

Lee G.,Yonsei University
Journal of Computing in Civil Engineering | Year: 2011

What information can or cannot be exchanged between different systems? Since the dawn of the computer-aided design and engineering era, interoperability has been an issue. The exchangeable set of information between different systems has been loosely defined as the intersection of information. Yet, as information flow has directionality, a general definition of "intersection" is inadequate to define an exchangeable set of information. This paper proposes a new directive set operation, semantic intersection, and discusses which information can or cannot be exchanged between different systems using the concept of semantic intersection. This opens up the possibility of predetermining or calculating the exchangeable set of information between two or more systems or the possibility of automated generation of a standard product model between different systems. This paper focuses on data exchange between systems, but the proposed theory is also applicable to data exchange between human beings. © 2011 ASCE.

Park M.C.,Yonsei University
Rheumatology (Oxford, England) | Year: 2010

Liver X receptors (LXRs) have been characterized as regulators of macrophage inflammatory pathways. Synthetic LXR agonists inhibit the macrophage response to bacterial pathogens and antagonize the induction of a number of pro-inflammatory genes. The aim of this study was to investigate the preventive effects of synthetic LXR agonist, GW3965, treatment on the evolution of arthritis and inflammatory response in a murine CIA model. Intradermal injection of bovine type II CIA in DBA/1 mice. Along with the induction of CIA, mice were treated with oral GW3965 (0.1, 0.3 or 1.0 mg/kg/day) or vehicle from Day 1 to Day 40. Clinical assessment for arthritis scores and histopathological assessment of joint sections were performed. The expression of inflammatory mediators was evaluated by immunohistochemical staining. Serum pro-inflammatory cytokine levels were determined using ELISA. The CIA incidence was 100% on Day 27 and the severity progressed until Day 35 with histological features of cartilage erosion in vehicle-treated mice. GW3965 treatment significantly reduced the arthritis incidence and attenuated the clinical and histological severity, compared with vehicle-treated mice. GW3965 treatment also significantly reduced inflammatory mediator production in joint sections and serum pro-inflammatory cytokine levels in a dose-dependent manner. These results indicate that activation of LXRs suppresses the onset of CIA and reduces inflammation and joint destruction in CIA mice. The data could suggest that LXR treatment is an effective prophylactic approach to suppress the evolution of synovitis and resultant joint destruction observed in RA.

Lee E.-Y.,Yonsei University
Medicine and Science in Sports and Exercise | Year: 2016

INTRODUCTION/PURPOSE: To examine whether body fatness (i.e., body mass index and % body fat) and psychosocial correlates of physical activity (PA) mediate the relationships between pubertal status and PA and sedentary behaviour (SB) among South Korean adolescent girls. METHODS: Pubertal status, body fatness, sport competence, perceived barriers to PA, self-efficacy, parental support for PA, self-reported and step-determined PA, and self-reported SB were assessed among 236 South Korean adolescent girls (mean age = 13.56 ± 1.2 years). RESULTS: A direct association was identified between pubertal status and PA in all models; more advanced pubertal status predicted lower PA among South Korean adolescents (b = -.51 ~ -.57; p < .001). Indirect effects on the pubertal status-PA relationship were also found: body fatness, perceived barriers to PA, and self-efficacy mediated the relationship between pubertal status and PA. Parental support for PA did not moderate the relationship between maturation and PA. SB was not associated with pubertal status. CONCLUSION: This study found mediated effects of body fatness, and psychosocial correlates (i.e., perceived barriers to PA, self-efficacy) on the relationship between maturity and PA among South Korean adolescent girls. Efforts to promote PA among South Korean adolescent girls should focus on reducing perceived barriers to PA, and increasing self-efficacy by providing more opportunities to have positive, and enjoyable experiences in PA among early-maturing girls. © 2016 American College of Sports Medicine

Hwang J.W.,Yonsei University
Journal of biomedical materials research. Part B, Applied biomaterials | Year: 2012

Various synthetic materials were developed to be used for implant dentistry and periodontal treatments. Among the various synthetic bone substitutes, calcium phosphate ceramics have been extensively investigated because their mineral chemistry resembles that of human bone. We evaluated the regeneration of three calcium phosphate synthetic block bone grafts in rabbit calvarial noncritical size defects. Four 8-mm-diameter defects were created in each rabbit (N = 10). Three defects, hydroxyapatite (HA), beta-tricalcium phosphate (β-TCP), and biphasic calcium phosphate (BCP), were randomly filled with one of three fabricated synthetic block bone graft materials. The fourth defect was filled with blood clots. Specimens were harvested at 4 and 8 weeks postsurgery. Histological and histometrical findings indicated that all three calcium phosphate block bone graft materials were able to maintain space significantly better than the control group at both 4 and 8 weeks. In the BCP group, the amount of newly formed bone was increased more than for the other groups. Additionally, β-TCP showed a large resorption of graft materials after 4 weeks postsurgery, while there were only small resorption for HA and BCP. Copyright © 2012 Wiley Periodicals, Inc.

Lee J.,Massachusetts Institute of Technology | Andrews J.G.,University of Texas at Austin | Hong D.,Yonsei University
IEEE Transactions on Wireless Communications | Year: 2011

This paper analyzes spectrum sharing between multiple systems. The efficiency of spectrum sharing is determined primarily by interference, which is a function of the spatial densities of the transmitters in systems dependent on the chosen spectrum sharing method. One method is underlay, which allows all systems to concurrently use the whole spectrum, and the other is overlay, in which a system only utilizes its own assigned spectrum. We define the spectrum-sharing transmission capacity (S-TC) as the number of successful transmissions per unit area subject to outage probability constraints for each system. To prevent some systems from monopolizing access to the spectrum, we also propose a fair coexistence constraint and derive the optimal spatial densities and relative transmission powers both with and without this constraint in terms of the sum S-TC. Through analytical results, the overlay and underlay methods are compared, verifying that the overlay method is generally preferred, and the underlay method is equally good only for optimal transmission power ratios under a fair coexistence constraint. © 2006 IEEE.

Portal vein thrombosis (PVT) is an uncommon cause of presinusoidal portal hypertension. Among various hepatoportal disorders, noncirrhotic portal hypertension conditions such as idiopathic portal hypertension (IPH) are considered to have a close relation with PVT. PVT is known to have several predisposing conditions, including infection, malignancies, and coagulation disorders. There is growing interest and recognition that deficiencies in proteins C and S are associated with a hypercoagulable state. These deficiencies are regarded as key factors of systemic hypercoagulability and recurrent venous thromboembolism. We report the case of a 19-year-old male diagnosed as IPH with PVT and combined deficiencies in proteins C and S.

Ko J.,Yonsei University
Molecules and Cells | Year: 2012

Synapses are asymmetric intercellular junctions connected by multiple synaptic cell adhesion molecules (CAMs). Synaptic CAMs function in various stages of synaptogenesis - the process of synapse creation - encompassing synapse formation, maturation, refinement, plasticity, and elimination. The list of synaptic CAMs has rapidly grown, although their precise functions of most CAMs at synapses remain incomplete. Members of an emerging class of transmembrane proteins containing leucine-rich repeat (LRR) domains have received considerable recent research attention. In this minireview, I discuss recent findings on LRR-containing synaptic CAMs that impact synapse development and circuit formation, focusing on two families of LRR synaptic CAMs: leucine-rich transmembrane proteins (LRRTMs) and Slit and Trk-like family (Slitrks). Their basic biochemical properties, proposed functions at synapses, physiological significances, and open questions are summarized. © The Korean Society for Molecular and Cellular Biology.

Lai W.-F.,Yonsei University
Biomaterials | Year: 2014

Cyclodextrins (CDs) are naturally occurring cyclic oligosaccharides. They consist of (α-1,4)-linked glucose units, and possess a basket-shaped topology with an "inner-outer" amphiphilic character. Over the years, substantial efforts have been undertaken to investigate the possible use of CDs in drug delivery and controlled drug release, yet the potential of CDs in gene delivery has received comparatively less discussion in the literature. In this article, we will first discuss the properties of CDs for gene delivery, followed by a synopsis of the use of CDs in development and modification of non-viral gene carriers. Finally, areas that are noteworthy in CD-based gene delivery will be highlighted for future research. Due to the application prospects of CDs, it is anticipated that CDs will continue to emerge as an important tool for vector development, and will play significant roles in facilitating non-viral gene delivery in the forthcoming decades. © 2013 Elsevier Ltd.

Kim H.O.,Yonsei University
Yonsei Medical Journal | Year: 2014

To date, the use of red blood cells (RBCs) produced from stem cells in vitro has not proved practical for routine transfusion. However, the perpetual and wide-spread shortage of blood products, problems related to transfusion-transmitted infections, and new emerging pathogens elicit an increasing demand for artificial blood. Worldwide efforts to achieve the goal of RBC production through stem cell research have received vast attention; however, problems with large-scale production and cost effectiveness have yet to prove practical usefulness. Some progress has been made, though, as cord blood stem cells and embryonic stem cells have shown an ability to differentiate and proliferate, and induced pluripotent stem cells have been shown to be an unlimited source for RBC production. However, transfusion of stem cell-derived RBCs still presents a number of challenges to overcome. This paper will summarize an up to date account of research and advances in stem cell-derived RBCs, delineate our laboratory protocol in producing RBCs from cord blood, and introduce the technological developments and limitations to current RBC production practices. © Yonsei University College of Medicine 2014.

Jang H.K.,Yonsei University
The International journal of oral & maxillofacial implants | Year: 2011

The aim of this study was to determine the accuracies of implant-level impressions for internal-connection dental implants with various angles of divergence. Five groups were created according to the angles of divergence (0, 5, 10, 15, and 20 degrees) between two implant analogs in a master model. A master stone model for each group was fabricated. The divergent angle in each master model was verified with a profilometer. Study models (n = 10) from each master model were constructed through the implant-level impression technique. The divergent angle in each study model was verified with the profilometer. The splinted metal framework with passive fit was cast with base metal and cast-on abutments in each master model. The metal framework was tried in the study models and the fit of each framework was evaluated. One-way analysis of variance and the Tukey Honestly Significant Difference test were used for statistical analysis. Statistically significant deformations of the impressions were found in the study models with divergently placed implant analogs. A larger divergence angle resulted in a larger gap between the framework and the implant analogs. The gap in the 20-degree divergence group differed significantly from that measured in the master model (P < .01). Internal-connection implants were accurate when the divergence angle was less than 15 degrees. Inaccuracy of impressions increased as the divergence angle increased. The inaccuracy was significantly greater for the 20-degree-divergent implants than the other groups.

Wilmer C.E.,Northwestern University | Farha O.K.,Northwestern University | Bae Y.-S.,Yonsei University | Hupp J.T.,Northwestern University | Snurr R.Q.,Northwestern University
Energy and Environmental Science | Year: 2012

There is an urgent need to identify porous materials that can efficiently separate CO2 from mixtures of gases, such as the exhaust of fossil-fuel-based power plants and from impure sources of CH4 (e.g., natural gas and landfill gas). Recently, researchers have investigated collections of porous metal-organic frameworks (MOFs) with the intent of finding correlations between CO2 separation ability and various material properties. However, due to the limited size of the collections, no clear correlations were found for material properties such as pore size, surface area, and pore volume, leaving researchers with little guidance in the design of new materials. In this work we drastically expand the scope of previous studies to include over 130 000 hypothetical MOFs, using molecular simulation to generate the adsorption properties. The resulting data exhibit sharply defined structure-property relationships that were not apparent when smaller collections of MOFs were considered. We show clear correlations between purely structural characteristics (e.g., pore size, surface area, and pore volume), as well as chemical characteristics (i.e., functional groups), with five adsorbent evaluation criteria taken from the engineering literature. These reported structure-property relationships can serve as a map for experimental synthesis going forward. © The Royal Society of Chemistry 2013.

Kim G.,Yonsei University
Clinical and molecular hepatology | Year: 2014

A systematic review (SR) is a research methodology that involves a comprehensive search for and analysis of relevant studies on a specific topic. A strict and objective research process is conducted that comprises a systematic and comprehensive literature search in accordance with predetermined inclusion/exclusion criteria, and an assessment of the risk of bias of the selected literature. SRs require a multidisciplinary approach that necessitates cooperation with clinical experts, methodologists, other experts, and statisticians. A meta-analysis (MA) is a statistical method of quantitatively synthesizing data, where possible, from the primary literature selected for the SR. Review articles differ from SRs in that they lack a systematic methodology such as a literature search, selection of studies according to strict criteria, assessment of risk bias, and synthesis of the study results. The importance of evidence-based medicine (EBM) in the decision-making for public policy has recently been increasing thanks to the realization that it should be based on scientific research data. SRs and MAs are essential for EBM strategy and evidence-based clinical practice guidelines. This review addresses the current trends in SRs and MAs in the field of hepatology via a search of recently published articles in the Cochrane Library and Ovid-MEDLINE.

Jang Y.H.,Yonsei University | Barber J.R.,University of Michigan
Journal of the Mechanics and Physics of Solids | Year: 2011

Kachanov's simplified model of microcrack interaction is applied to an investigation of the behaviour of a cracked body under predominantly compressive periodic loading, so that the cracks experience periods of closure and slip, with frictional dissipation. The model is shown to be equivalent to a discrete elastic frictional system with each crack representing one node. Theorems and algorithms from such systems are applied to determine the conditions under which the system shakes down to a state with no slip and hence no energy dissipation in friction. For conditions not too far beyond the shakedown state, the dissipation is significantly affected by the initial conditions, but with larger oscillating loads, it becomes a unique and increasing function of load amplitude. The effect of crack interaction is assessed by comparison with an uncoupled model, for which the dissipation is obtained as a summation of closed form expressions over the crack population. For small numbers of cracks, the results are significantly dependent on the randomly chosen crack locations and sizes, but with larger populations, a statistically significant decrease in dissipation is observed with increasing interaction terms. © 2010 Elsevier Ltd. All rights reserved.

Choi J.Y.,Yonsei University
Infection and Chemotherapy | Year: 2013

HIV-infected patients are known to have severe psychosocial problems; however, clinicians tend to overlook these psychosocial issues. Song et al. identified depression and anxiety as the most common mental illnesses among HIV-infected patients. Psychosocial issues are important factors and are associated with poor adherence, which leads to treatment failure and resistance. Clinicians who tend to HIV patients should be attentive to the patients' psychosocial problems and regularly conduct screening for depressive disorders. Mental health must be addressed to improve the quality of life of patients with HIV/AIDS. © 2013 by The Korean Society of Infectious Diseases | Korean Society for Chemotherapy.

Lim S.,Yonsei University | Reeves B.,Stanford University
International Journal of Human Computer Studies | Year: 2010

Computer and videogames often require that users interact with other characters on the screen that represent other real people or characters that are controlled by computer code running within the game. The difference between game play with other avatars (player-controlled characters) or agents (characters controlled by the computer) may influence the engagement a game player experiences. This study investigated the effects of agency (avatar versus agent) and the type of gaming activity (competition versus cooperation) on physiological arousal and subjective evaluation of play. A 2 (avatar, agent)×2 (competition, cooperation) within-subject experiment was conducted (N=32). Players exhibited greater physiological arousal to otherwise identical interactions when other characters were introduced as an avatar rather than an agent. Furthermore, the co-player's source of agency interacted with the type of gaming activity. The results have implications for understanding how different forms of representation in virtual worlds and games will affect psychological responses in the contexts of entertainment, learning and the conduct of serious work. © 2009 Elsevier Ltd. All rights reserved.

An S.-I.,Yonsei University
Journal of Climate | Year: 2011

The equatorial Pacific atmosphere responds differently to global warming in the Gill-type and Lindzen-Nigam models. Under an assumption of no change in the zonal sea surface temperature (SST) gradient in the Gill-type model, the Walker circulation is intensified in a warmer climate relative to current climatic conditions, while slightly weakened in the Lindzen-Nigam model. Furthermore, for more accurate derivation of the surface wind, the free atmosphere in the Gill-type model is combined with the atmospheric boundary layer. This modified Gill-type model actually produces weaker surface wind than the Gill-type model would, but the sensitivity of the Walker circulation to the warmer climate is similar to that obtained from the Gilltype model. These results may explain why the zonal gradient of equatorial Pacific SST during the twentieth century is observed to strengthen while the Walker circulation is not, even though they are dynamically linked. © 2011 American Meteorological Society.

Kim T.G.,Yonsei University | Shin H.,Hanyang University | Lim D.W.,Hanyang University
Advanced Functional Materials | Year: 2012

Biomimetic scaffolds mimic important features of the extracellular matrix (ECM) architecture and can be finely controlled at the nano- or microscale for tissue engineering. Rational design of biomimetic scaffolds is based on consideration of the ECM as a natural scaffold; the ECM provides cells with a variety of physical, chemical, and biological cues that affect cell growth and function. There are a number of approaches available to create 3D biomimetic scaffolds with control over their physical and mechanical properties, cell adhesion, and the temporal and spatial release of growth factors. Here, an overview of some biological features of the natural ECM is presented and a variety of original engineering methods that are currently used to produce synthetic polymer-based scaffolds in pre-fabricated form before implantation, to modify their surfaces with biochemical ligands, to incorporate growth factors, and to control their nano- and microscale geometry to create biomimetic scaffolds are discussed. Finally, in contrast to pre-fabricated scaffolds composed of synthetic polymers, injectable biomimetic scaffolds based on either genetically engineered- or chemically synthesized-peptides of which sequences are derived from the natural ECM are discussed. The presence of defined peptide sequences can trigger in situ hydrogelation via molecular self-assembly and chemical crosslinking. A basic understanding of the entire spectrum of biomimetic scaffolds provides insight into how they can potentially be used in diverse tissue engineering, regenerative medicine, and drug delivery applications. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Choi J.H.,Dong - A University | Shin M.W.,Yonsei University
Microelectronics Reliability | Year: 2012

This paper reports on the thermal analysis and improvement of the light emitting diode (LED) module as a lighting source. The analysis was made by transient thermal measurement and thermal simulation using the Finite Volume Method. Two basic thermal schemes were applied for the decrease of the junction temperature of the LED module. Thermal resistance was analytically defined for the LED module with multi LED packages and was confirmed by the experimental data obtained from the thermal transient method. It was found that the thermal improvement of the LED module led to the enhancement of the light output power and radiant intensity. The thermally designed LED module exhibited about 20% decrease in junction temperature compared with a basic structure before thermal design. The temperature calibrating factor, 0.046 nm/°C, was calculated from the peak wavelengths of the LED modules. © 2011 Elsevier Ltd. All rights reserved.

Shin M.W.,Yonsei University | Jang S.H.,Korea University
Solid-State Electronics | Year: 2012

In this paper we describe a novel thermal characterization method of GaN-based Light Emitting Diode (LED) package driven under the Alternating Current (AC) mode. The result was compared with the results from the thermal analysis for LED package operated under the Direct Current (DC) condition. Different from the DC condition, the junction temperature rise with the operation time of LED package was exhibited in a band formation. Finite Volume Method (FVM) was utilized to calculate the thermal performance of LED package under the AC condition using the input power extracted from the output current and voltage from the AC power supply. The experimental result was in a good agreement with the simulation data. © 2011 Elsevier Ltd. All rights reserved.

Kim H.,Seoul National University | Park Y.N.,Yonsei University
Digestive Diseases | Year: 2014

Hepatocellular carcinoma (HCC) is heterogeneous in histopathology, pathogenesis and biological behavior. There is accumulating evidence that the expression of 'stemness'-related markers such as K19, EpCAM and CD133 in HCC is associated with an aggressive biological behavior and poor clinical outcome compared to conventional HCCs that do not express stemness-related markers. Compared to conventional HCCs, these tumors more frequently demonstrate infiltrative growth patterns, vascular invasion and more intratumoral fibrous stroma, and there is a spectrum of morphological and immunophenotypic features between HCCs with stemness-related marker expression, scirrhous HCCs and combined hepatocellular-cholangiocarcinoma with stem cell features. Clinically, HCCs with stemness-related marker expression are associated with increased serum a-fetoprotein levels and a poor prognosis, and are also beginning to be noticed radiologically. These tumors have also been recognized as a specific subtype in recent molecular classifications, and increasing interest in the molecular pathogenesis of HCCs with stemness-related marker expression will shed light on the development of targeted therapy for these tumors. Therefore, it is important that pathologists identify HCCs expressing stemness-related markers such as K19 during routine pathological evaluation of surgically resected or biopsied HCC tissue, as it will help to identify a high-risk subgroup of HCCs characterized by increased chemoresistance, earlier recurrence after surgical and/or locoregional treatment, increased invasiveness/metastasis and poor overall survival. We will discuss the clinicopathological characteristics of a HCC subtype expressing stemness-related markers and its future perspectives. © 2014 S. Karger AG, Basel.

Yoo S.J.,Yonsei University
IET Control Theory and Applications | Year: 2010

This study presents an adaptive tracking control approach for trajectory tracking of wheeled mobile robots with torque saturation in the presence of unknown skidding and slipping. The robot kinematics and dynamics are induced from the perturbed non-holonomic constraints. The adaptive control system using the kinematics transformed in polar coordinates is developed to compensate unknown skidding and slipping at the dynamic level of mobile robots with the input saturation. All signals of the controlled closed-loop system are uniformly bounded and the point tracking errors converge to an adjustable neighbourhood of the origin regardless of large initial tracking errors, input saturation and unknown skidding and slipping. Simulation results are provided to demonstrate the performance and stability of the proposed control scheme. © 2010 The Institution of Engineering and Technology.

Jeong H.-S.,Yonsei University
Health Affairs | Year: 2011

This study presents data on health care spending in South Korea in the three decades since 1977, the year its national health insurance - enacted in 1963 - was enforced. National health insurance in South Korea is currently a single-payer program (that is both publicly and privately financed) that pays for privately provided health care. Universal coverage was achieved in 1989. As a result, the household share of total national health spending fell from 87.8 percent to 54.6 percent during the three decades, and the out-of-pocket share dropped from 87.2 percent to 38.0 percent. Although covered services have gradually expanded, benefits remain relatively low, and public funding is limited, leaving beneficiaries with relatively high copayments. Coupled with the fact that the government manages the schedule of fees paid to providers, the health care share of gross domestic product was a low 6.3 percent in 2007. An analysis such as this may be of particular interest in middle- or low-income countries contemplating expansions of coverage or undertaking insurance reforms. ©2011 Project HOPE - The People-to-People Health Foundation, Inc.

Kim K.J.,Yonsei University
Journal of atherosclerosis and thrombosis | Year: 2011

Type 2 diabetes mellitus (T2DM) is a risk factor for increased arterial stiffness. We evaluated associations between the cardio-ankle vascular index (CAVI) and carotid plaque, intima media thickness (IMT), and diabetic microvascular complications in Korean T2DM patients. We conducted a retrospective, cross-sectional study of 320 Korean T2DM patients without a history of macrovascular disease or macroalbuminuria. We measured 24-hour urinary albumin excretion (UAE) levels and performed funduscopic and neuropathy examinations to assess the extent of diabetic microvascular complications. Arterial stiffness was assessed using CAVI. We also measured the ankle-brachial index (ABI), common carotid artery IMT, and carotid beta stiffness index. Among the 320 patients enrolled in this study, 64 (20%) had increased CAVI (≥ 9). We found that CAVI was correlated with systolic blood pressure, pulse pressure, IMT, carotid beta stiffness index, log-transformed UAE, and total cholesterol. In multiple logistic regression analysis, mean IMT and the presence of carotid plaque were independently associated with increased CAVI (≥ 9) (OR=5.77, P < 0.01; OR=5.36, P < 0.001, respectively). Furthermore, an increased CAVI was associated with peripheral neuropathy (OR=2.03, P = 0.03) and microalbuminuria (OR=2.47, P < 0.01) after adjusting for possible confounding variables. The results of this study suggest that increased CAVI is associated with the presence of arterial plaque, increased IMT, and microvascular complications, such as nephropathy and neuropathy, in T2DM patients.

This review examines the challenges in the chemical synthesis of average sized proteins. Recent progress on sequential and convergent ligation methods, two approaches to the synthesis of proteins, is outlined. An examination of these challenges could aid in the process of finding new methodologies for the efficient chemical synthesis of average sized protein molecules. Copyright (c) 2010 Wiley Periodicals, Inc.

Kim S.K.,University of Texas at Austin | Sessler J.L.,University of Texas at Austin | Sessler J.L.,Yonsei University
Chemical Society Reviews | Year: 2010

Compared with simple ion receptors, which are able to bind either a cation or an anion, ion pair receptors bearing both a cation and an anion recognition site offer the promise of binding ion pairs or pairs of ions strongly as the result of direct or indirect cooperative interactions between co-bound ions. This critical review focuses on the recent progress in the design of ion pair receptors and summarizes the various binding modes that have been used to accommodate ion pairs (110 references). © 2010 The Royal Society of Chemistry.

Son D.I.,Korea Institute of Science and Technology | Kwon B.W.,Korea Institute of Science and Technology | Park D.H.,Korea Institute of Science and Technology | Seo W.-S.,Korea Institute of Ceramic Engineering And Technology | And 4 more authors.
Nature Nanotechnology | Year: 2012

Hybrid nanostructures combining inorganic materials and graphene are being developed for applications such as fuel cells, batteries, photovoltaics and sensors. However, the absence of a bandgap in graphene has restricted the electrical and optical characteristics of these hybrids, particularly their emissive properties. Here, we use a simple solution method to prepare emissive hybrid quantum dots consisting of a ZnO core wrapped in a shell of single-layer graphene. We then use these quantum dots to make a white-light-emitting diode with a brightness of 798 cd m ĝ̂'2. The strain introduced by curvature opens an electronic bandgap of 250 meV in the graphene, and two additional blue emission peaks are observed in the luminescent spectrum of the quantum dot. Density functional theory calculations reveal that these additional peaks result from a splitting of the lowest unoccupied orbitals of the graphene into three orbitals with distinct energy levels. White emission is achieved by combining the quantum dots with other emissive materials in a multilayer light-emitting diode. © 2012 Macmillan Publishers Limited.

Nadeem S.,Quaid-i-Azam University | Lee C.,Yonsei University
Nanoscale Research Letters | Year: 2012

The steady boundary layer flow of nanofluid over an exponential stretching surface is investigated analytically. The transport equations include the effects of Brownian motion parameter and thermophoresis parameter. The highly nonlinear coupled partial differential equations are simplified with the help of suitable similarity transformations. The reduced equations are then solved analytically with the help of homotopy analysis method (HAM). The convergence of HAM solutions are obtained by plotting h-curve. The expressions for velocity, temperature and nanoparticle volume fraction are computed for some values of the parameters namely, suction injection parameter α Lewis number Le, the Brownian motion parameter Nb and thermophoresis parameter Nt. © 2012 Nadeem and Lee.

Lee J.-S.,Yonsei University
IEEE Transactions on Multimedia | Year: 2014

This paper investigates the issue of designing paired comparison-based subjective quality assessment experiments for reliable results. In particular, the convergence behavior of the quality scores estimated from paired comparison results is considered. Via an extensive computer simulation experiment, the estimation performance in terms of the root mean squared error, the rank order correlation coefficient, and the change of the estimated scores with respect to the number of subjects are mathematically modeled. Furthermore, it is confirmed that the models coincide with the theoretical convergence behavior. Issues such as the effect of human errors and the underlying distribution of the true quality scores are also examined. © 1999-2012 IEEE.

BACKGROUND: Neutrophil-lymphocyte ratio (NLR) reflects the balance between pro- and anti-tumor immune activities. We evaluated whether NLR is associated with pathologic tumor response and prognosis in rectal cancer patients that underwent preoperative chemoradiaton therapy (CRT) with surgery.METHODS: One hundred two patients with rectal cancer that were treated by preoperative CRT followed by surgery were enrolled. A total of 50.4 GY of radiation and 5-FU-based chemotherapy were delivered. An NLR ≥ 3 was considered to be elevated. Pathologic tumor response based on ypTNM stage was categorized into two groups, good response (n = 35, pathologic complete response and ypTNM I) and poor response groups (n = 67, ypTNM II, III, and IV).RESULTS: Twenty-five patients (24.5%) had elevated NLR. Multivariate analysis showed that an elevated CEA level (p = 0.001), larger tumor (p = 0.03), and elevated NLR (p = 0.04) were significant predictors for a poor response. Poor pathological tumor response and elevated NLR were risk factors for cancer-specific and recurrence-free survivals.CONCLUSION: An elevated NLR before CRT can be used as predictors for poor tumor response and unfavorable prognostic factors. Dominant pro-tumor activities of neutrophils or reduced anti-tumor immune response by lymphocytes, as determined by NLR, may have a impact on poor tumor response and unfavorable prognosis.

Cho J.,Samsung | Kim B.S.,Yonsei University
Energy and Buildings | Year: 2011

In a typical data center, large numbers of IT sever racks are arranged in multiple rows. In IT environments, in which extensive electronic hardware is air-cooled, cooling system inefficiencies result when heated exhaust air from equipment prematurely mixes with chilled coolant air before it is used for cooling. Mixing of chilled air before it is used with heated exhaust air results in significant cooling inefficiencies in many systems. Over-temperatures may not only harm expensive electronic equipment but also interrupt critical and revenue generating services. The cool shield is a cost effective aisle partition system used to contain the air in cold aisles and hot aisles of an IT server room. This paper focuses on the use of performance metrics for analyzing a vertical aisle partition system in high-density data centers. Performance metrics provide a great opportunity for the data center industry at large. They could form the foundation for a standardized way of specifying and reporting various cooling solutions. The Rack Cooling Index (RCI) is a measure of how well the system cools the IT servers within the manufacturers' specifications, and the Return Temperature Index (RTI) is a measure of the energy performance of the air-management system. Combined, they provide an opportunity to judge the performance of the aisle partition system in an objective way subsequent to comprehensive CFD modeling. © 2011 Elsevier B.V. All rights reserved.

Kim J.Y.,Yonsei University | Muallem S.,U.S. National Institutes of Health
EMBO Journal | Year: 2011

A crucial component of the receptor-evoked Ca2+ signal is Ca2+ influx mediated by the store-operated Ca2+ channels (SOCs). The molecular makeup of one SOC is the endoplasmic reticulum (ER) Ca2+ sensor STIM1 and the pore-forming Orai1. Ca2+ release from the ER leads to co-clustering of STIM1 and Orai1 to activate Orai1. The short STIM1 SOAR/CAD domain (STIM1 Orai1-activating region/CRAC-activating domain), which has two coiledcoil (C-C) domains, interacts with the Orai1 C terminus C-C domain to activate the channel. How the function of SOAR is regulated is not known. Korzeniowski et al (2010) and Muik et al (2011; this issue) now identified an autoinhibitory domain in STIM1 that occludes SOAR. Release of SOAR involves a conformational transition that is aided by the Orai1 C-C domain. © 2011 European Molecular Biology Organization.

Shin S.,Yonsei University
Environmental Politics | Year: 2013

Sulphur dioxide (SO2) emissions and acid rain have been one of the most serious environmental problems in China. In order to address these problems, the Chinese government has shown much interest in SO2 emission trading scheme. In spite of the government's enthusiasm, full support from US government and international organisations, and overall success of the pilot projects in several local areas in China, SO2 emission trading has never been institutionalised in any of the Chinese provinces, and therefore, became virtually unavailable. Why did China fail to adopt and institutionalise the SO2 emission trading scheme? What are the factors that affect a country's policy innovation process? Based on the diffusion and innovation literature, it is argued that policy innovation is constrained by domestic institutional factors and that lack of domestic preconditions for effective diffusion and innovation makes policy adoption costly, and therefore, leads local governments to decide not to adopt the policy. © 2013 Copyright Taylor and Francis Group, LLC.

Kim H.,Yonsei University
Thin Solid Films | Year: 2011

Atomic layer deposition (ALD) is expected to play an important role in future device fabrication due to various benefits, such as atomic level thickness control and excellent conformality. Plasma enhanced ALD (PE-ALD) allows deposition at significantly lower temperatures with better film properties compared to that of conventional thermal ALD. In addition, since ALD is a surface-sensitive deposition technique, surface modification through plasma exposure can be used to alter nucleation and adhesion. In this paper, characteristics of PE-ALD for various applications in semiconductor fabrication are presented through comparison to thermal ALD. The results indicate that the PE-ALD processes are versatile methods to enable nanoscale manufacturing in emerging applications. © 2011 Elsevier B.V.

Park J.-H.,Yonsei University
Information Processing and Management | Year: 2014

Social networking sites (SNSs) enable user to personalize their contents and functions. This feature has been assumed as causing positive effects on the use of online information services through enhancing user satisfaction. However, unlike other online information services (non-participatory information services), due to the results of personalization in a certain situation, SNS users cannot help using the SNS even though they feel dissatisfaction on using it. SNSs are different from other information services in the sense that they create and sustain their own value based on the number of participating members. In SNSs, personalization, reflected by updates and maintenance of profile pages, results in such participation. This study hypothesizes that personalization influences on the continued use of SNSs through two factors: switching cost (extrinsic factor) and satisfaction (intrinsic factor). Web-based survey was conducted with the samples of 677 SNS users from six universities in the US. In-person interviews were conducted with 25 university students to elicit their thoughts on the SNSs. Quantitative analysis employed by testing the proposed model with five hypotheses through a structural equation modeling (SEM) technique. The transcribed interview data was analyzed following the constant comparative technique. The main findings indicate that, as expected, the personalization increases its switching cost as well as satisfaction, which results in further use of SNSs. These findings suggest that it is necessary to consider both extrinsic and intrinsic factors of user perceptions when adding personalization features on SNSs. © 2014 Elsevier Ltd. All rights reserved.

Lee D.H.,Yonsei University | Joo Y.H.,Kunsan National University | Tak M.H.,Kunsan National University
Information Sciences | Year: 2014

This paper proposes a strategy to estimate invariant subsets of the domain of attraction (DA) for asymptotically stable zero equilibrium points of continuous-time Takagi-Sugeno (T-S) fuzzy systems. Specifically, by using Lyapunov's stability theory and the linear matrix inequality (LMI) technique, sufficient conditions for proving the local stability are provided in terms of single-parameter minimization problems subject to LMI constraints or eigenvalue problems, which are solvable via convex optimizations. The fuzzy Lyapunov functions (FLFs), expressed by the so-called multi-dimensional fuzzy summations, are employed to characterize invariant subsets of the DA as sublevel sets of the FLFs. To compute a larger inner estimate of the DA, an iterative LMI algorithm is also developed. Finally, illustrative examples show the efficacy of the approach. © 2013 Elsevier Inc. All rights reserved.

Choi J.-I.,Yonsei University | Edwards J.R.,North Carolina State University
Indoor Air | Year: 2012

A large-eddy simulation is used to investigate contaminant transport owing to complex human and door motions and vent-system activity in room compartments where a contaminated and clean room are connected by a vestibule. Human and door motions are simulated with an immersed boundary procedure. We demonstrate the details of contaminant transport owing to human- and door-motion-induced wake development during a short-duration event involving the movement of a person (or persons) from a contaminated room, through a vestibule, into a clean room. Parametric studies that capture the effects of human walking pattern, door operation, over-pressure level, and vestibule size are systematically conducted. A faster walking speed results in less mass transport from the contaminated room into the clean room. The net effect of increasing the volume of the vestibule is to reduce the contaminant transport. The results show that swinging-door motion is the dominant transport mechanism and that human-induced wake motion enhances compartment-to-compartment transport. © 2011 John Wiley & Sons A/S.

FLICE-like inhibitory protein (FLIP) is a critical regulator of death receptor-mediated apoptosis. Here, we found ubiquitin-specific peptidase 8 (USP8) to be a novel deubiquitylase of the long isoform of FLIP (FLIPL). USP8 directly deubiquitylates and stabilizes FLIPL, but not the short isoform. USP8 depletion induces FLIPL destabilization, promoting anti-Fas-, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)- and tumor necrosis factor alpha-induced extrinsic apoptosis by facilitating death-inducing signaling complex or TNFR1 complex II formation, which results in the activation of caspase-8 and caspase-3. USP8 mRNA levels are elevated in melanoma and cervical cancers, and the protein levels of USP8 and FLIPL are positively correlated in these cancer cell lines. Xenograft analyses using ME-180 cervical cancer cells showed that USP8 depletion attenuated tumor growth upon TRAIL injection. Taken together, our data indicate that USP8 functions as a novel deubiquitylase of FLIPL and inhibits extrinsic apoptosis by stabilizing FLIPL.Oncogene advance online publication, 20 June 2016; doi:10.1038/onc.2016.215. © 2016 Macmillan Publishers Limited

Park S.,Yonsei University
Electronics Letters | Year: 2014

A new hybrid automatic repeat request (HARQ) scheme is proposed for multiple-input multiple-output (MIMO) systems when the acknowledgment (ACK) bundling is applied for packet retransmissions. In the proposed HARQ scheme, both Chase combining (CC) and incremental redundancy (IR) are utilised for a retransmission request, and the proposed HARQ scheme is called a multiple retransmission strategy-based HARQ (MRS-HARQ). During the reception process of the MRS-HARQ, IR packets obtain signal-to-noise ratio gains using the extended detection with CC packets and the improved IR packets are utilised to eliminate the interference from the CC packets. This sequential reliability improvement allows the MRSHARQ to decrease the occurrence of the deficient transmissions, and the proposed MRS-HARQ can achieve an improved error performance and throughput over the conventional CC-based and IR-based HARQ schemes with the ACK bundling. © The Institution of Engineering and Technology 2014.

An S.-I.,Yonsei University | Choi J.,Seoul National University
Climate Dynamics | Year: 2014

Using the Paleoclimate Modeling Inter-comparison Project Phase 2 and 3 (PMIP2 and PMIP3), we investigated the tropical Pacific climate state, annual cycle, and El Niño-Southern Oscillation (ENSO) during the mid-Holocene period (6,000 years before present; 6 ka run). When the 6 ka run was compared to the control run (0 ka run), the reduced sea surface temperature (SST) and the reduced precipitation due to the basin-wide cooling, and the intensified cross-equatorial surface winds due to the hemispheric discrepancy of the surface cooling over the tropical Pacific were commonly observed in both the PMIP2 and PMIP3, but changes were more dominant in the PMIP3. The annual cycle of SST was weaker over the equatorial eastern Pacific, because of the orbital forcing change and the deepening mixed layer, while it was stronger over the equatorial western pacific in both the PMIP2 and PMIP3. The stronger annual cycle of the equatorial western Pacific SST was accompanied by the intensified annual cycle of the zonal surface wind, which dominated in the PMIP3 in particular. The ENSO activity in the 6 ka run was significantly suppressed in the PMIP2, but marginally reduced in the PMIP3. In general, the weakened air-sea coupling associated with basin-wide cooling, reduced precipitation, and a hemispheric contrast in the climate state led to the suppression of ENSO activity, and the weakening of the annual cycle over the tropical eastern Pacific might lead to the intensification of ENSO through the frequency entrainment. Therefore, the two opposite effects are slightly compensated for by each other, which results in a small reduction in the ENSO activity during the 6 ka in the PMIP3. On the whole, in PMIP2/PMIP3, the variability of canonical (or conventional) El Niño tends to be reduced during 6 ka, while that of CP/Modoki El Niño tends to be intensified. © 2013 Springer-Verlag Berlin Heidelberg.

Objective: To evaluate the effect of posterior vitreomacular adhesion (VMA), documented by optical coherence tomography (OCT), on the outcome of anti-vascular endothelial growth factor (VEGF) treatment for exudative age-related macular degeneration (AMD). Design: Retrospective comparative series. Participants: A total of 148 patients (148 eyes) who were newly diagnosed with exudative AMD and were treated by anti-VEGF in 1 eye from 2005 to 2008 with a minimum of 12 months follow-up. Methods: We retrospectively reviewed OCT and medical records of 148 patients with exudative AMD and categorized them according to the presence of posterior VMA into 2 subgroups: VMA (+) group (38 eyes) and VMA (-) group (110 eyes). Best-corrected visual acuity (BCVA) and central retinal thickness (CRT) after anti-VEGF treatment were compared between the 2 groups at baseline; at 1, 3, 6, and 12 months; and at the last visit (mean = 21 months). Main Outcome Measures: Mean changes in BCVA, which was converted to logarithm of the minimum angle of resolution (logMAR) values and CRT after anti-VEGF treatment. Results: Mean BCVA significantly decreased over time in the VMA (+) group compared with the VMA (-) group (P = 0.039). At the last follow-up, mean BCVA had deteriorated from 0.87 logMAR (20/149 Snellen equivalent; baseline) to 0.98 logMAR (20/189 Snellen equivalent) in the VMA (+) group, but improved from 0.82 logMAR (20/132 Snellen equivalent, baseline) to 0.72 logMAR (20/104, Snellen equivalent) in the VMA (-) group (P = 0.028). In paired comparisons of BCVA between baseline and each follow-up visit, the VMA (-) group showed significant improvement of BCVA at every follow-up visit (P<0.05); however, the VMA (+) group did not show significant visual improvement at any follow-up visit despite anti-VEGF treatment (P>0.05). Comparison of mean CRT between baseline and each follow-up visit showed a statistically significant decrease at every follow-up in both groups (P<0.05). Conclusions: Posterior VMA was associated with an inferior visual outcome after intravitreal anti-VEGF treatment for exudative AMD. Our results suggest that chronic tractional forces may antagonize the effect of anti-VEGF treatment, resulting in poor response to anti-VEGF treatment with patients with VMA. Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article. © 2011 American Academy of Ophthalmology.

Kim J.,Yonsei University | Lee J.,Yonsei University | Kim J.,Korea Electronics Technology Institute | Yun J.,Korea Electronics Technology Institute
IEEE Communications Surveys and Tutorials | Year: 2014

Machine-to-Machine (M2M) refers to technologies with various applications. In order to provide the vision and goals of M2M, an M2M ecosystem with a service platform must be established by the key players in industrial domains so as to substantially reduce development costs and improve time to market of M2M devices and services. The service platform must be supported by M2M enabling technologies and standardization. In this paper, we present a survey of existing M2M service platforms and explore the various research issues and challenges involved in enabling an M2M service platform. We first classify M2M nodes according to their characteristics and required functions, and we then highlight the features of M2M traffic. With these in mind, we discuss the necessity of M2M platforms. By comparing and analyzing the existing approaches and solutions of M2M platforms, we identify the requirements and functionalities of the ideal M2M service platform. Based on these, we propose an M2M service platform (M2SP) architecture and its functionalities, and present the M2M ecosystem with this platform. Different application scenarios are given to illustrate the interaction between the components of the proposed platform. In addition, we discuss the issues and challenges of enabling technologies and standardization activities, and outline future research directions for the M2M network. © 2014 IEEE.

Hargrove A.E.,University of Texas at Austin | Nieto S.,University of Zaragoza | Zhang T.,Henkel AG | Sessler J.L.,University of Texas at Austin | And 2 more authors.
Chemical Reviews | Year: 2011

The investigation of synthetic (abiotic) phosphate receptors seeks to provide improved methodologies for the detection, extraction, and transport of biologically, chemically, and environmentally important phosphates. The design of phosphate receptors is complicated by the acid-base properties of phosphate anions. In addition to the more common anion-hydrogen bond donor interactions, protonated phosphate anions can also interact with hydrogen bond acceptors. A variety of recognition interactions, such as hydrogen bonding, electrostatic interactions, van der Waals forces, π-surface interactions, shape complementarity, and metal coordination, have been employed alone or in concert to generate phosphate receptors. Many noncolored receptors have been functionalized with chromophores to produce covalent frameworks that undergo a pronounced color change when treated with an appropriate guest. Indicator displacement assay (IDA) is a competition method for the sensing of analytes.

Staurosporine, a non-specific protein kinase inhibitor, has been shown to induce neurite outgrowth in PC12 cells, but the mechanism by which staurosporine induces neurite outgrowth is still obscure. In the present study, we investigated whether the activation of Rac1 was responsible for the neurite outgrowth triggered by staurosporine. Staurosporine caused rapid neurite outgrowth independent of the ERK signaling pathways. In contrast, neurite outgrowth in response to staurosporine was accompanied by activation of Rac1, and the Rac1 inhibitor NSC23766 attenuated the staurosporine-induced neurite outgrowth in a concentration-dependent manner. In addition, suppression of Rac1 activity by expression of the dominant negative mutant Rac1N17 also blocked the staurosporine-induced morphological differentiation of PC12 cells. Staurosporine caused an activation of NADPH oxidase and increased the production of reactive oxygen species (ROS), which was prevented by NSC23766 and diphenyleneiodonium (DPI), an NADPH oxidase inhibitor. Staurosporine-induced neurite outgrowth was attenuated by pretreatment with DPI and exogenous addition of sublethal concentration of H2O2 accelerated neurite outgrowth triggered by staurosporine. These results indicate that activation of Rac1, which leads to ROS generation, is required for neurite outgrowth induced by staurosporine in PC12 cells.

Jung H.H.,Yonsei University
Journal of neurosurgery | Year: 2010

The purpose of this study was to assess the efficacy of Gamma Knife surgery (GKS) for treating cavernous sinus dural arteriovenous fistulas (CSDAVFs). Of the 4123 GKSs performed between May 1992 and March 2009, 890 procedures were undertaken to treat vascular lesions. In 24 cases, the vascular lesion that was treated was a dural arteriovenous fistula, and in 6 of these cases, the lesion involved the cavernous sinus. One of these 6 cases was lost to follow-up, leaving the other 5 cases (4 women and 1 man) to comprise the subjects of this study. All 5 patients had more than 1 ocular symptom, such as ptosis, chemosis, proptosis, and extraocular movement palsy. In all patients, CSDAVF was confirmed by conventional angiography. Three patients were treated by GKS alone and 2 patients were treated by GKS combined with transarterial embolization. The median follow-up period after GKS in these 5 cases was 30 months (range 9-59 months). All patients experienced clinical improvement, and their improvement in ocular symptoms was noticed at a mean of 17.6 weeks after GKS (range 4-24 weeks). Two patients received embolization prior to GKS but did not display improvement in ocular symptoms. An average of 20 weeks (range 12-24 weeks) was needed for complete improvement in clinical symptoms. There were no treatment-related complications during the follow-up period. Gamma Knife surgery should be considered as a primary, combined, or additional treatment option for CSDAVF in selected cases, such as when the lesion is a low-flow shunt without cortical venous drainage. For those selected cases, GKS alone may suffice as the primary treatment method when combined with close monitoring of ocular symptoms and intraocular pressure.

To evaluate whether the overgrowth of costal cartilage may cause pectus carinatum using three-dimensional (3D) computed tomography (CT). Twenty-two patients with asymmetric pectus carinatum were included. The fourth, fifth and sixth ribs and costal cartilages were semi-automatically traced, and their full lengths were measured on three-dimensional CT images using curved multi-planar reformatted (MPR) techniques. The rib length and costal cartilage length, the total combined length of the rib and costal cartilage and the ratio of the cartilage and rib lengths (C/R ratio) in each patient were compared between the protruding side and the opposite side at the levels of the fourth, fifth and sixth ribs. The length of the costal cartilage was not different between the more protruded side and the contralateral side (55.8 ± 9.8 mm vs 55.9 ± 9.3 mm at the fourth, 70 ± 10.8 mm vs 71.6 ± 10.8 mm at the fifth and 97.8 ± 13.2 mm vs 99.8 ± 15.5 mm at the sixth; P > 0.05). There were also no significant differences between the lengths of ribs. (265.8 ± 34.9 mm vs 266.3 ± 32.9 mm at the fourth, 279.7 ± 32.7 mm vs 280.6 ± 32.4 mm at the fifth and 283.8 ± 33.9 mm vs 283.9 ± 32.3 mm at the sixth; P > 0.05). There was no statistically significant difference in either the total length of rib and costal cartilage or the C/R ratio according to side of the chest (P > 0.05). In patients with asymmetric pectus carinatum, the lengths of the fourth, fifth and sixth costal cartilage on the more protruded side were not different from those on the contralateral side. These findings suggest that overgrowth of costal cartilage cannot explain the asymmetric protrusion of anterior chest wall and may not be the main cause of pectus carinatum.

Moon J.H.,Yonsei University
The spine journal : official journal of the North American Spine Society | Year: 2012

Local anesthetics combined with corticosteroids are commonly used for management of back pain in interventional spinal procedures. Several recent studies suggest cytotoxicity of bupivacaine, whereas others report protective and cytotoxic effects of corticosteroids on chondrocytes and intervertebral disc cells. Considering the frequent use of these agents in spinal interventions, it is meaningful to know how they affect intervertebral disc cells. This study was conducted to assess the effects of bupivacaine and triamcinolone, both alone and in combination, on viability of intervertebral disc cells in vitro. Controlled laboratory study. Nucleus pulposus cells were isolated from human disc specimens from patients undergoing surgery because of disc herniation or degenerative disc disease. They were grown in three-dimensional alginate beads for 1 week to maintain their differentiated phenotypes and to allow for matrix formation before analysis. After 1 week of culture, the cells were exposed to bupivacaine (0.1%, 0.25%, 0.5%, and 1%) or bupivacaine (0.1%, 0.25%, 0.5%, and 1%) with 1 mg of triamcinolone for 1, 3, or 6 hours. Cell viability was measured using trypan blue exclusion assay and flow cytometry. Live cell/dead cell fluorescent imaging was assessed using confocal microscopy. Trypan blue exclusion assays demonstrated dose- and time-dependent cytotoxic effects of bupivacaine on human nucleus pulposus cells. Similar but reduced cytotoxicity was observed after exposure to the combination of bupivacaine and 1 mg of triamcinolone. Flow cytometry showed a dose-dependent cytotoxic effect of bupivacaine on nucleus pulposus cells after 3 hours of exposure. The reduced cytotoxicity of bupivacaine combined with 1 mg of triamcinolone was also confirmed in flow cytometry. Confocal images showed that the increase in dead cells correlated with the concentration of bupivacaine. Nevertheless, fewer cells died after exposure to several different concentrations of bupivacaine combined with 1 mg of triamcinolone than did after exposure to bupivacaine alone. The combination of bupivacaine and triamcinolone induced dose- and time-dependent cytotoxicity on human intervertebral disc cells in vitro, but the cytotoxicity was much weaker than that of bupivacaine alone. This study shows a potential protective influence of triamcinolone on intervertebral disc cells. Copyright © 2012 Elsevier Inc. All rights reserved.

The objectives of this study were to evaluate the diagnostic value of delayed-enhancement cardiovascular magnetic resonance (DE-CMR) imaging in differentiating cardiac tumors from thrombi in patients with suspected cardio-embolic stroke. Two radiologists blinded to the study protocol retrospectively evaluated MR images of 22 patients (12 men and 10 women; mean age 59.2 years) that had recently experienced a stroke and undergone CMR. Six cardiac tumors and 16 thrombi were confirmed on surgery or follow-up examinations. On DE-CMR, a tumor was defined as an intracardiac mass showing post-contrast enhancement, and a thrombus was defined as an intracardiac mass showing black signal intensity (SI) without post-contrast enhancement. The mean SI in regions of interest in the normal myocardium and cardiac mass were measured using cine-CMR and DE-CMR. Visual assessment of enhancement characteristics of cardiac masses on DE-CMR could accurately differentiate cardiac tumors from thrombi in all cases. On cine-CMR, the mean SI ratios for tumors and thrombi were 1.45 ± 0.45 (range, 1.12-2.16) and 1.39 ± 0.33 (range, 0.87-2.09), respectively (P = 0.745). On DE-CMR, the mean SI ratios for tumors and thrombi were 5.65 ± 2.96 (range, 2.98-9.92) and 1.06 ± 0.43 (range, 0.67-1.95), respectively (P < 0.001). DE-CMR is a non-invasive modality for detecting intra-cardiac mass can differentiate tumors from thrombi in cardio-embolic stroke patients.

Lee J.-H.,Yonsei University | Kim W.T.,Yale University
Molecules and Cells | Year: 2011

Ubiquitination is a unique protein degradation system utilized by eukaryotes to efficiently degrade detrimental cellular proteins and control the entire pool of regulatory components. In plants, adaptation in response to various abiotic stresses can be achieved through ubiquitination and the resulting degradation of components specific to these stress signalings. Arabidopsis has more than 1,400 E3 enzymes, indicating E3 ligase acts as a main determinant of substrate specificity. However, as only a minority of E3 ligases related to abiotic stress signaling have been studied in Arabidopsis, the further elucidation of the biological roles and related substrates of newly identified E3 ligases is essential in order to clarify the functional relationship between abiotic stress and E3 ligases. Here, we review the current knowledge and future prospects of the regulatory mechanism and role of several E3 ligases involved in abiotic stress signal transduction in Arabidopsis. As another potential approach to understand how ubiquitination is involved in such signaling, we also briefly introduce factors that regulate the activity of cullin in multisubunit E3 ligase complexes.

Park S.,Korea Railroad Research Institute | Hong D.,Yonsei University
IEEE Transactions on Wireless Communications | Year: 2013

We consider energy harvesting cognitive radio networks in which a secondary transmitter harvests energy from ambient sources or wireless power transfer systems while opportunistically accessing the spectrum licensed to the primary network. The primary traffic is modeled as a time-homogeneous discrete Markov process, and the secondary transmitter may not be able to operate continuously due to sporadic and unstable energy sources. At the beginning of each time slot, the secondary transmitter thus needs to determine whether to remain idle so as to conserve energy, or to execute spectrum sensing to acquire knowledge of the current spectrum occupancy state. It also needs to configure the spectrum sensor detection threshold to achieve an effective tradeoff between false alarms and misdetections. This sequential decision-making, done to maximize the expected total throughput, requires the joint design of a spectrum sensing policy and a detection threshold under the energy causality and collision constraints. We formulate this stochastic optimization problem as a constrained partially observable Markov decision process (POMDP), and then convert it to a computationally tractable unconstrained POMDP. Numerical results show that the proposed approach enables efficient usage of the harvested energy by exploiting the temporal correlation of the primary traffic. © 2002-2012 IEEE.

Park H.,Yonsei University
Journal of Gastroenterology and Hepatology (Australia) | Year: 2011

Functional gastrointestinal disorders (FGIDs) are common in clinical practice and in communities around the world, including Korea. In a recent point prevalence study on functional dyspepsia (FD) in Korea using the Rome III criteria, 13.4% of community respondents reported dyspepsia. Forty-seven percent of these FD cases were classified as postprandial distress syndrome, 26% as epigastric pain syndrome, and 27% as overlap syndrome. Upper and lower GI symptoms commonly overlap and FGIDs are related to psychological disorders. In our recent study of subjects recruited from a health-screening program, the point prevalence of FD, irritable bowel syndrome (IBS), and reflux esophagitis (RE) was 13.2%, 3.9%, and 8.2%, respectively. The odds ratio of having FD and IBS together was estimated to be 4.4 (95% CI: 1.21-15.71). We found a positive relationship between FD and IBS. Recently, several genetic studies have suggested that serotonin transporter (SERT) gene polymorphisms and the G-protein β3 (GNβ3) C825T gene polymorphism are associated with FD and IBS. However, we did not find an association between SERT and GNβ3 C825T genetic polymorphisms and overlap syndrome, including FD and IBS, in our previous study in a Korean population. We therefore undertook a validation study of the Rome III criteria for FGIDs by factor analysis of symptoms. The sensitivity and specificity of Rome III criteria in discriminating FGIDs from organic diseases of the upper GI tract was 60% and 53%, respectively, while the sensitivity and specificity of these criteria for the lower GI tract was 80% and 50%, respectively, partially supporting the use of the Rome III criteria in Korea. © 2011 Journal of Gastroenterology and Hepatology Foundation and Blackwell Publishing Asia Pty Ltd.

Choi J.K.,Yonsei University
The Tohoku journal of experimental medicine | Year: 2011

Chronic sleep deprivation is increasingly common in industrialized societies. Short sleep duration has been associated with a number of negative health outcomes. The objectives of this study were to investigate the association between self-reported sleep duration and the presence of metabolic syndrome (combination of central obesity, triglyceride, high density lipoprotein, blood pressure, fasting plasma glucose) in adults during midlife. The Korean Genomic Rural Cohort (KGRC) is a cohort study of aged 40 to 70 years in rural Korea. This study focuses on the prevalence, incidence, and risk factors for chronic degenerative disorders, such as hypertension, diabetes, osteoporosis, respiratory diseases, and metabolic syndrome. The baseline sample of participants in the KGRC study was recruited in 2005-2006 (phase 1). Respondents were followed until 2008-2009 (phase 2). The final sample included 1,107 subjects: 386 males (34.9%) and 721 females (65.1%). The incidence rate of metabolic syndrome in our sample was 18.4% (21.2% for males and 16.9% for females). Subjects sleeping < 6 hours a day (HR: 1.798; 95% CI: 1.06-3.05) were significantly more likely to experience metabolic syndrome than participants sleeping 6 to 7.9 hours a day after controlling for potential covariates (age, body mass index, menopause, smoking, alcohol and physical activity). Shorter sleep duration was associated with the high incidence of metabolic syndrome among females only. In conclusion, shorter sleep duration may be a significant risk factor for the development of metabolic syndrome in women.

The precipitation behavior of j-carbide during isothermal aging was investigated in the Fe-9Mn-6Al- 0.15C (wt.%) lightweight steel through thermodynamic calculations and microstructural analyses using various microscopes and an X-ray diffractometer. No precipitates of j-carbide were observed in both hot-rolled and annealed specimens. The j-carbide started to precipitate at the grain boundaries of d-ferrite and at interphase boundaries between δ-ferrite and γ-austenite and between α-ferrite and a0-martensite after isothermal aging at 550 °C for 1 h. While the precipitation and growth of κ-carbide at the boundaries continued, new κ-carbide precipitated alongside α-ferrite by the eutectoid reaction to form a lamellar structure in austenite during 6-h aging. This result confirmed that the precipitation of κ-carbide at the boundaries preceded the precipitation of the lamellar κ-carbide due to the pre-segregation of solute atoms to the boundaries. The α'-martensite was not transformed to γ-austenite and just tempered during isothermal aging at 550 °C. © 2013 Elsevier B.V. All rights reserved.

Lee W.-S.,Yonsei University
Journal of Dermatological Science | Year: 2011

Integral hair lipid (IHL) is bound to the keratinized cell surface to make an environmentally resistant lipid envelope. It is mainly positioned on the hair cuticle and inner root sheath. IHL in the hair follicle may regard as hair barrier to be similar to the epidermal lipid layer functioning as skin barrier. Major constituents of IHL are fatty acid, phytosphingosine, ceramide in decreasing order. Minor constituents of IHL are cholesterol, cholesterol sulfate and cholesterol oleate. Cuticle or cortical cell surface in hair are abundant in fatty acids unlike the keratinized area of epidermis or sebaceous gland, and about 30-40% of such fatty acids are composed of 18-methyl-eicosanoic acid which is known to be bound to proteins by ester or thioester bond. Various factors including moisture, solvent, oxidative damage during bleaching or permanent waving affect IHL. Photochemical changes also can occur in IHL as well as in hair protein and hair pigment. Lipid metabolism is thought to play an essential role in lipid envelope of hair, but also involvement in hair development and function. © 2011 Japanese Society for Investigative Dermatology.

Shin D.H.,Yonsei University
Expert review of cardiovascular therapy | Year: 2012

Percutaneous coronary intervention is evolving rapidly. Among the developments in various aspects, dual antiplatelet therapy (DAPT) has played a pivotal role to reduce thrombotic events after stent implantation. After the introduction of the drug-eluting stent, prolonged DAPT has been recommended due to concerns regarding late and very late stent thrombosis. However, there are controversies regarding the benefit of long-term DAPT. In addition, prolonged DAPT accompanies increased bleeding risk as well as additional cost. To balance the benefit and risk, optimizing DAPT duration is crucial. In this article, clinical guidelines and studies regarding optimal duration of DAPT are discussed.

Im I.,Yonsei University | Hong S.,Sangmyung University | Kang M.S.,Hansung University
Information and Management | Year: 2011

We examined the relationships of the constructs in the UTAUT model to determine how they are affected by culture. In our study, we used data from Korea and the U.S. to examine two technologies: the MP3 player and Internet banking. Results showed that the UTAUT model fits our data well. The comparison of Korea and the U.S. revealed that the effects of effort expectancy on behavioral intention and the effects of behavioral intention on use behavior were greater in the U.S. sample. The implications of this are discussed. © 2010 Elsevier B.V.

Animesh A.,McGill University | Pinsonneault A.,McGill University | Yang S.-B.,Hansung University | Oh W.,Yonsei University
MIS Quarterly: Management Information Systems | Year: 2011

Although research on three-dimensional virtual environments abounds, little is known about the social and business aspects of virtual worlds. Given the emergence of large-scale social virtual worlds, such as Second Life, and the dramatic growth in sales of virtual goods, it is important to understand the dynamics that govern the purchase of virtual goods in virtual worlds. Employing the stimulus-organism-response (S-O-R) framework, we investigate how technological (interactivity and sociability) and spatial (density and stability) environments in virtual worlds influence the participants' virtual experiences (telepresence, social presence, and flow), and how experiences subsequently affect their response (intention to purchase virtual goods). The results of our survey of 354 Second Life residents indicate that interactivity, which enhances the interaction with objects, has a significant positive impact on telepresence and flow. Also, sociability, which fosters interactions with participants, is significantly associated with social presence, although no such significant impact was observed on flow. Furthermore, both density and stability are found to significantly influence participants' virtual experiences; stability helps users to develop strong social bonds, thereby increasing both social presence and flow. However, contrary to our prediction of curvilinear patterns, density is linearly associated with flow and social presence. Interestingly, the results exhibit two opposing effects of density: while it reduces the extent of flow, density increases the amount of social presence. Since social presence is found to increase flow, the net impact of density on flow depends heavily on the relative strength of the associations involving these three constructs. Finally, we find that flow mediates the impacts of technological and spatial environments on intention to purchase virtual products. We conclude the paper with a discussion of the theoretical and practical contributions of our findings.

Kim E.H.,Yonsei University
Clinical and molecular hepatology | Year: 2013

Telbivudine is an L-nucleoside analogue with potent antiviral activity against hepatitis B virus (HBV). Clinical trials have shown that telbivudine has a more potent and sustained antiviral activity with a lower frequency of viral resistance than lamivudine. Although there are several reports concerning the safety profile of telbivudine, most adverse events are described as mild and transient in nature. Here we report two cases of telbivudine-induced myopathy in patients with chronic hepatitis B who were siblings.

Seo J.-Y.,Howard Hughes Medical Institute | Seo J.-Y.,Yonsei University | Cresswell P.,Howard Hughes Medical Institute
PLoS Pathogens | Year: 2013

Human cytomegalovirus (HCMV) has been shown to induce increased lipogenesis in infected cells, and this is believed to be required for proper virion envelopment. We show here that this increase is a consequence of the virus-induced redistribution of the host protein viperin to mitochondria and its capacity to interact with and block the function of the mitochondrial trifunctional protein (TFP), the enzyme that mediates fatty acid-β-oxidation. The resulting decrease in cellular ATP levels activates the enzyme AMP-activated protein kinase (AMPK), which induces expression of the glucose transporter GLUT4, resulting in increased glucose import and translocation to the nucleus of the glucose-regulated transcription factor ChREBP. This induces increased transcription of genes encoding lipogenic enzymes, increased lipid synthesis and lipid droplet accumulation, and generation of the viral envelope. Viperin-dependent lipogenesis is required for optimal production of infectious virus. We show that all of these metabolic outcomes can be replicated by direct targeting of viperin to mitochondria in the absence of HCMV infection, and that the motif responsible for Fe-S cluster binding by viperin is essential. The data indicate that viperin is the major effector underlying the ability of HCMV to regulate cellular lipid metabolism. © 2013 Seo, Cresswell.

Lee H.-J.,Medical Corps of Sangmudae Army Service Support Group | Lee S.-H.,Yonsei University
Allergy, Asthma and Immunology Research | Year: 2014

Atopic dermatitis (AD) is a multifactorial inflammatory skin disease perpetuated by gene-environmental interactions and which is characterized by genetic barrier defects and allergic inflammation. Recent studies demonstrate an important role for the epidermal permeability barrier in AD that is closely related to chronic immune activation in the skin during systemic allergic reactions. Moreover, acquired stressors (e.g., Staphylococcus aureus infection) to the skin barrier may also initiate inflammation in AD. Many studies involving patients with AD revealed that defective skin barriers combined with abnormal immune responses might contribute to the pathophysiology of AD, supporting the outside-inside hypothesis. In this review, we discuss the recent advances in human and animal models, focusing on the defects of the epidermal permeability barrier, its immunologic role and barrier repair therapy in AD.

Kim H.,Seoul National University | Um E.,CHA Medical University | Cho S.-R.,Yonsei University | Jung C.,Hanyang University | And 2 more authors.
Nature Methods | Year: 2011

Zinc-finger nucleases (ZFNs) and TAL-effector nucleases (TALENs) are powerful tools for creating genetic modifications in eukaryotic cells and organisms. But wild-type and mutant cells that contain genetic modifications induced by these programmable nucleases are often phenotypically indistinguishable, hampering isolation of mutant cells. Here we show that transiently transfected episomal reporters encoding fluorescent proteins can be used as surrogate genes for the efficient enrichment of endogenous gene-modified cells by flow cytometry. © 2011 Nature America, Inc. All rights reserved.

Kim S.,Yonsei University
The International journal of oral & maxillofacial implants | Year: 2011

Resolution of defects surrounding dental implants can be achieved through the placement of rough-surfaced implants with bone substitutes. The aim of this study was to evaluate the effect of biphasic calcium phosphates (BCP) on the healing of circumferential bone defects surrounding dental implants. The premolars were removed in four mongrel dogs, and three different types of experimental sites were created: BCP, control, and ungrafted sites. In all groups, implants were placed in the edentulous area. In the BCP group, gap defects with 2-mm diameters were surgically created around each implant and the defects were filled with BCP bone substitute. In the control group, gap defects were not made around the implants. In the sham surgery group, gap defects were prepared but were not filled with BCP bone substitute. The defects were evaluated histologically and histometrically after 8 and 16 weeks. One-way analysis of variance and the independent t test were used for statistical analysis (α = .01). Histometric measurements in the groups after 8 weeks showed the smallest remaining defect depths (RDDs) in the control group (17%). The RDD in the BCP group (39%) was greater than in the control group, and the ungrafted sites group had the greatest RDD (62%). There was no difference in bone-to-implant contact among the groups. Histometric measurements at 16 weeks showed that the RDD in the ungrated sites group (57%) was greater than in both the control (12%) and the BCP (31%) groups. Within the limitations of this study, BCP bone substitute contributed to defect resolution and maintained space for new bone ingrowth before 8 weeks. No additional contribution to defect resolution by BCP was found after 8 weeks.

Kim H.,Yonsei University
Annals of the New York Academy of Sciences | Year: 2011

Reactive oxygen species (ROS) are important mediators to induce pancreatitis. Serum levels of antioxidant enzymes and carotenoids including lycopene are lower in patients with pancreatitis than those of healthy subjects. The cholecystokinin (CCK) analog cerulein induces similar pathologic events as shown in human pancreatitis. Recent studies show that high doses of cerulein activate NF-κB and induce the expression of inflammatory cytokines, in pancreatic acinar cells, which is mediated by the activation of NADPH oxidase. Lycopene functions as a very potent antioxidant to suppress the induction of inflammatory cytokines, in pancreatic acinar cells stimulated with cerulein. In this review, the possible beneficial effect of lycopene on experimental pancreatitis shall be discussed based on its antioxidant activity. © 2011 New York Academy of Sciences..

Choi H.S.,Yonsei University
Numerical Heat Transfer; Part A: Applications | Year: 2015

In the present study, heat transfer through the wall of a blunt body immersed in a fluidized bed was investigated. A Eulerian approach based on the kinetic theory was used to simulate the multiphase thermal flow, and the determined heat transfer coefficients indicated the existence of different heat transfer patterns in the different walls of the blunt body. It was observed that, with increasing inlet gas velocity, the time-area-averaged heat transfer coefficients of the walls of the bodies HC1-HC3 rapidly increased and then gradually decreased. However, the heat transfer patterns in the walls of the bodies HC4 and HC5, which were initially located outside the bed, were different. The peculiar heat transport phenomena were further investigated by statistical methods. Copyright © 2015 Taylor & Francis Group, LLC.

Lee S.,University of Michigan | Lee Y.,Yonsei University
IEEE Microwave and Wireless Components Letters | Year: 2012

Wideband branch-line couplers with arbitrary coupling levels are demonstrated. By integrating single-section quarter-wave transformers at each port, wideband characteristic with excellent coupling flatness is achieved. Also, a method is demonstrated that introduces intentional mismatch for a further enhancement in bandwidth. Superior structural and design simplicity outperform previous wideband couplers. Branch-line couplers at 3 GHz are demonstrated experimentally that maintain the coupling level within 0.5 dB from the specified 10 dB in as much as a 50.9% bandwidth, with minimum return loss and isolation of 16.3 and 18.7 dB, respectively. © 2006 IEEE.

Lee B.-K.,Yonsei University
Korean Circulation Journal | Year: 2011

Computational fluid dynamics (CFD) is a mechanical engineering field for analyzing fluid flow, heat transfer, and associated phenomena, using computer-based simulation. CFD is a widely adopted methodology for solving complex problems in many modern engineering fields. The merit of CFD is developing new and improved devices and system designs, and optimization is conducted on existing equipment through computational simulations, resulting in enhanced efficiency and lower operating costs. However, in the biomedical field, CFD is still emerging. The main reason why CFD in the biomedical field has lagged behind is the tremendous complexity of human body fluid behavior. Recently, CFD biomedical research is more accessible, because high performance hardware and software are easily available with advances in computer science. All CFD processes contain three main components to provide useful information, such as pre-processing, solving mathematical equations, and post-processing. Initial accurate geometric modeling and boundary conditions are essential to achieve adequate results. Medical imaging, such as ultrasound imaging, computed tomography, and magnetic resonance imaging can be used for modeling, and Doppler ultrasound, pressure wire, and non-invasive pressure measurements are used for flow velocity and pressure as a boundary condition. Many simulations and clinical results have been used to study congenital heart disease, heart failure, ventricle function, aortic disease, and carotid and intra-cranial cerebrovascular diseases. With decreasing hardware costs and rapid computing times, researchers and medical scientists may increasingly use this reliable CFD tool to deliver accurate results. A realistic, multidisciplinary approach is essential to accomplish these tasks. Indefinite collaborations between mechanical engineers and clinical and medical scientists are essential. CFD may be an important methodology to understand the pathophysiology of the development and progression of disease and for establishing and creating treatment modalities in the cardiovascular field. Copyright © 2011 The Korean Society of Cardiology.

Roznyatovskiy V.V.,University of Texas at Austin | Lee C.-H.,Kangwon National University | Sessler J.L.,University of Texas at Austin | Sessler J.L.,Yonsei University
Chemical Society Reviews | Year: 2013

The phenomenon of π-extension has been widely applied to, and exploited within, the field porphyrin chemistry. The development of reliable synthetic routes to various useful starting materials has facilitated the underlying preparative work. The chemical resemblance between porphyrins and expanded and isomeric porphyrins, as well as the increasing accessibility of the requisite starting materials is giving birth to the hybrid field of π-extended expanded and isomeric porphyrins. This tutorial review is intended to provide an overview of up-to-date published synthetic efforts and to summarize the effect of annulation on the properties of expanded and isomeric porphyrins. This journal is © The Royal Society of Chemistry.

Park J.,Korea Institute of Construction Technology | Hong T.,Yonsei University
Renewable and Sustainable Energy Reviews | Year: 2013

Recently, many countries have been making an effort to reduce their carbon dioxide (CO2) emission, and as part of such effort, the United Nations Framework Convention on Climate Change (UNFCCC) adopted the Kyoto Protocol in 1997. South Korea is very likely to be included in the second batch of countries that must reduce their greenhouse gas emission after the end of the implementation of the Kyoto Protocol in 2012. Reducing the country's CO 2 emission, however, can have an impact on the economy. Therefore, in this study, the correlations between South Korea's economic growth, CO 2 emission, and energy consumption were analyzed. The analysis period was from Q1 1991 to Q4 2011, and the analysis methods that were used were regression analysis for the relational analysis among the various overall indices, and the Markov switching model for a more detailed analysis. The results of the analyses showed that South Korea's economic growth and CO 2 emission were coincidental. The correlation analysis of the country's economic growth and energy consumption showed a significant correlation between economic growth and fossil fuels, which emit CO2, such as coal in the industrial sector, petroleum products in the industrial and transportation sectors, and liquefied natural gas (LNG) in the residential/ commercial and industrial sectors. It is expected that the results of this study will pave the way for the conduct of various researches on controlling the country's CO2 emission management, and for suggestions for such to be given, such as policies for reducing the energy consumption in each sector, using the methodology proposed in this study. © 2012 Elsevier Ltd. All rights reserved.

Suresh B.,Yonsei University
Cell Death and Differentiation | Year: 2016

Post-translational modifications (PTMs) of stemness-related proteins are essential for stem cell maintenance and differentiation. In stem cell self-renewal and differentiation, PTM of stemness-related proteins is tightly regulated because the modified proteins execute various stem cell fate choices. Ubiquitination and deubiquitination, which regulate protein turnover of several stemness-related proteins, must be carefully coordinated to ensure optimal embryonic stem cell maintenance and differentiation. Deubiquitinating enzymes (DUBs), which specifically disassemble ubiquitin chains, are a central component in the ubiquitin-proteasome pathway. These enzymes often control the balance between ubiquitination and deubiquitination. To maintain stemness and achieve efficient differentiation, the ubiquitination and deubiquitination molecular switches must operate in a balanced manner. Here we summarize the current information on DUBs, with a focus on their regulation of stem cell fate determination and deubiquitinase inhibition as a therapeutic strategy. Furthermore, we discuss the possibility of using DUBs with defined stem cell transcription factors to enhance cellular reprogramming efficiency and cell fate conversion. Our review provides new insight into DUB activity by emphasizing their cellular role in regulating stem cell fate. This role paves the way for future research focused on specific DUBs or deubiquitinated substrates as key regulators of pluripotency and stem cell differentiation.Cell Death and Differentiation advance online publication, 10 June 2016; doi:10.1038/cdd.2016.53. © 2016 Macmillan Publishers Limited

Banerjee P.S.,Johns Hopkins University | Hart G.W.,Johns Hopkins University | Cho J.W.,Yonsei University
Chemical Society Reviews | Year: 2013

The enzymatic addition of a single β-D-N-acetylglucosamine sugar molecule on serine and/or threonine residues of protein chains is referred to as O-GlcNAcylation. This novel form of post-translational modification, first reported in 1984, is extremely abundant on nuclear and cytoplasmic proteins and has site specific cycling dynamics comparable to that of protein- phosphorylation. A nutrient and stress sensor, O-GlcNAc abnormalities underlie insulin resistance and glucose toxicity in diabetes, neurodegenerative disorders and dysregulation of tumor suppressors and oncogenic proteins in cancer. Recent advances have helped understand the biochemical mechanisms of GlcNAc addition and removal and have opened the door to developing key inhibitors towards this type of protein modification. Advanced methods in detecting and measuring O-GlcNAcylation have assisted in delineating its biological roles in a variety of cellular processes and diseased states. Availability of facile glycomic techniques are allowing for the exponential growth in the study of protein O-GlcNAcylation and are helping to elucidate key biological roles of this novel PTM. © 2013 The Royal Society of Chemistry.

Kim Y.K.,Yonsei University
Telemedicine journal and e-health : the official journal of the American Telemedicine Association | Year: 2011

With the development of information technology, real-time telemetry has been invented for checking patients' physiologic parameters during their transport, via an Emergency Medical Service (EMS) system. We developed a Real-Time Telemetry System (RTS), which sends physiologic parameters including electrocardiogram (ECG), vital signs, and pulse asymmetry in real-time from the ambulance to a hospital through the Emergency Medical Information Center, a kind of central control unit. Therefore, we asked whether the RTS monitoring affects the use of medical direction in EMS system. Of six ambulance stations covering EMS transport with RTS monitor, 941 patients who were classified as emergency patients by an Emergency Medical Technician were retrospectively enrolled in this study. We divided them into two groups: group 1 (the patients using RTS monitoring) and group 2 (control group). The mean age was 53.5±22.8 years, and 494 patients were men. RTS monitoring was used in 118 (20%) patients. Medical direction for treatments in group 1 was much more than that of group 2 (8.0% vs. 0.3%; p <0.001). Ambulance diversion to proper hospitals in group 1 was much more than that of group 2 (14.4% vs. 0.1%; p <0.001). The mean treatment time at the scene in group 1 also decreased more significantly than that of group 2 (4.4±3.5 min vs. 6.3±5.9 min; p <0.001). The results showed that intermediate medical direction in the cases using the RTS was conducted more than in the conventional method-ambulance to the hospital. These results suggest that the RTS monitoring enhances the quality in developing EMS system.

Hong T.-K.,Yonsei University
Bulletin of the Seismological Society of America | Year: 2010

The crustally-guided shear wave, Lg, is typically the strongest phase at regional distances. Lg phases are analyzed often for estimation of magnitudes of regional events. The variation of Lg in regions with both continental and oceanic environments has been rarely investigated. We investigate Lg attenuation in a plate-margin area around Korea and Japan that is encompassed by seas and oceans. The mean quality factor of Lg at 1 Hz (Q0) is 498. The geometrical-spreading exponent term is estimated as 0.75. These observations characterize the study region as a high attenuation region compared to typical intraplate continental regions. Low-Q regions are widely developed over the Japanese islands, with some spotted high-Q regions. Relatively high Q is observed in most regions of the Korean Peninsula except a south-eastern part where a Cretaceous volcanic-sediment basin exists. The high-Q values are close to the typical Q value in continental crust. Significantly low Q of 100 or less is observed in most oceanic regions including the East Sea (Sea of Japan), the Pacific Ocean, and the South China Sea. The high attenuation of Lg in oceanic regions suggests possible underestimation of magnitudes of oceanic events. Thus, it appears that proper correction of Lg amplitude is highly desired for accurate estimation of magnitudes of regional oceanic events.

Hong T.-K.,Yonsei University
Journal of Geophysical Research: Solid Earth | Year: 2010

Regional and teleseismic waveforms of underground nuclear explosions (UNEs) at the Balapan and the Nevada test sites are analyzed to understand the nature of shear waves excited from UNEs. The phase composition of wavefields in the source and receiver regions is examined using a source array frequency-wave-number analysis and polarization analyses. It is observed that regional mantle-lid shear waves, Sn, often develop strongly. On the other hand, observed teleseismic shear waves from UNEs are much weaker than those from earthquakes. Source array analyses of the shear waves from UNEs display coherent energy that is polarized in a certain azimuthal direction. The observation of coherent shear energy in different UNEs suggests that the shear energy is excited in a consistent manner at every UNE. We constrain the dominant shear wave excitation mechanism from the observed shear wave features. The observations appear to be consistent with the tectonic release model with conical rock cracking. Copyright © 2010 by the American Geophysical Union.

Hong S.-Y.,Yonsei University
Quarterly Journal of the Royal Meteorological Society | Year: 2010

This paper investigates the impact of stable boundary-layer (SBL)mixing in a vertical diffusion package on the simulated climatology in a regional model. In contrast to previous studies, we focus on the sensitivity of the simulated climatology to the representation of SBL processes in the modelled atmosphere, paying particular attention to precipitation and associated large-scale patterns. The new SBL scheme, based on the bulk Richardson number between the surface layer and the top of the boundary layer and implemented in the Yonsei University (YSU) boundary-layer scheme, was evaluated against the local scheme in which the mixing coefficient is a function of the local Richardson number at a given model level. A statistical evaluation of a series of short-range forecast confirms that the boundary-layer structure is closer to the radiosonde observation when the new SBL scheme is used. In a regional climate framework, the results with the new SBL scheme in July 2006 demonstrate that modulating the subcloud structure with enhanced vertical mixing improves the simulated monsoon climatology by displacing the monsoonal precipitation southwards. Together with the local effects of the enhanced SBL mixing that warms and dries the boundary layer, the dynamical feedbacks accompanying strengthened moisture convergence results in enhanced precipitation towards what was observed. A ten-member ensemble of three-month June-July-August simulations for 1999-2008 shows that the revised SBL scheme improves the temperature and moisture profiles in the lower troposphere as well as the precipitation climatology. The interannual variation of seasonal precipitation is more realistic over both land and oceans. © 2010 Royal Meteorological Society.

Kim E.-J.,Numerical Prediction Office | Hong S.-Y.,Yonsei University
Journal of Geophysical Research: Atmospheres | Year: 2010

This study investigates the effects of air-sea interaction on the simulated East Asian summer monsoon (EASM) climate in a regional climate model. An ocean mixed layer model with a revised surface roughness length formulation that was originally designed for tropical cyclone simulation and a prognostic sea surface skin temperature scheme that considers the heat budget at the water surface are systematically evaluated on the monsoonal climate over East Asia for July 2006 in the regional Weather Research and Forecasting (WRF) model. Also, 9-year (2000-2008) June-August simulations are performed to evaluate the overall impacts of these three components on the simulated EASM climatology. The 1 month simulation for July 2006 reveals that the inclusion of the ocean mixed layer model cools the water surface due to enhanced mixing, in particular, when winds are strong. Such cooling is largely compensated by the inclusion of prognostic skin temperature since solar heating in daytime overwhelms the cooling in nighttime. The revised surface roughness length effectively reduces the surface heat flux by reducing the exchange coefficients, against the conventional Charnock formula. Consideration of the three components together results in the reduction of systemic biases of excessive precipitation and weakening of the North Pacific high in the summer climate from 2000 to 2008. It is concluded that the methodology designed in this study can be an efficient way to represent the air-sea interaction in regional atmospheric models for numerical weather prediction and climate simulation. Copyright 2010 by the American Geophysical Union.

Park S.,Yonsei University | Lakatta E.G.,U.S. National Institute on Aging
Yonsei Medical Journal | Year: 2012

Increased arterial stiffness is an independent predictor of cardiovascular disease independent from blood pressure. Recent studies have shed new light on the importance of inflammation on the pathogenesis of arterial stiffness. Arterial stiffness is associated with the increased activity of angiotensin II, which results in increased NADPH oxidase activity, reduced NO bioavailability and increased production of reactive oxygen species. Angiotensin II signaling activates matrix metalloproteinases (MMPs) which degrade TGFβ precursors to produce active TGFβ, which then results in increased arterial fibrosis. Angiotensin II signaling also activates cytokines, including monocyte chemoattractant protein-1, TNF-α, interleukin-1, interleukin-17 and inter-leukin-6. There is also ample clinical evidence that demonstrates the association of inflammation with increased arterial stiffness. Recent studies have shown that reductions in inflammation can reduce arterial stiffness. In patients with rheumatoid arthritis, increased aortic pulse wave velocity in patients was significantly reduced by anti tumor necrosis factor-α therapy. Among the major classes of anti hypertensive drugs, drugs that block the activation of the RAS system may be more effective in reducing the progression of arterial stiffness. Thus, there is rationale for targeting specifc inflammatory pathways involved in arterial stiffness in the development of future drugs. Understanding the role of inflammation in the pathogenesis of arterial stiffness is important to understanding the complex puzzle that is the pathophysiology of arterial stiffening and may be important for future development of novel treatments. © Yonsei University College of Medicine 2012.

Innovation has become a key concept in recent decades. Truly innovative products can create value for consumers, extend the product category, generate higher margins, and strengthen the brand. Simply speaking, relationships may form between product innovation and each driver of customer equity. However, for different product categories and nationalities, this relationship may differ. This paper not only identifies the relationships between innovation and customer equity, but also examines the moderating effects of product category and nationality. In total, 409 consumers from Korea (n = 200) and China (n = 209) were surveyed by questionnaire in this study. The stimuli of the degree of innovation (i.e., radical or incremental) included Nike+Ipod and Adidas 1, and Nike Air Max and Adidas Team Series from the shoe industry, while H&M designer label and Nano material, and H&M seasonal collection and cycle material from the clothing industry. Structural equation modeling was used to test the hypotheses. The results show that the degree of innovation exerts positive influences on value equity and brand equity, which can be drivers of customer equity. Thus, the reason firms launch innovative products is not only to boost sales by increasing customer value, but also to improve brand image, which can influence the customers' purchase decision. The relationship between innovation and customer equity can be moderated by product category and nationality. Managers should develop different innovation strategies based on different product categories and customer nationalities. © 2012 Product Development & Management Association.

Park S.-B.,Yonsei University
Journal of Product Innovation Management | Year: 2013

This research investigates how brand strategy and technological uncertainty influence the order-of-entry effects for a previous generation pioneer in the successive generation. The findings of our longitudinal experiment reemphasize the importance of continuous pioneering, demonstrating that consumers exhibit a strong preference for a previous generation pioneer's product when it continues to pioneer the successive generation. More importantly, the findings indicate that continuous pioneering with a new brand leads to greater brand preferences when technological uncertainty is high. This is because in that condition, consumers perceive greater innovativeness with a new brand than with the extant one. On the other hand, an extant brand increases consumer brand preferences for a previous generation pioneer's product in the successive generation when technological uncertainty is low. The theoretical and practical implications of the results for understanding and managing pioneering advantage and brand strategy in the multigenerational product markets are discussed. © 2012 Product Development & Management Association.

Park H.J.,Yonsei University
BMC medical education | Year: 2013

Successful cecal intubation (SCI) is not only a quality indicator but also an important marker in a colonoscopy trainee's progress. We conducted this study to determine factors predicting SCI in colonoscopy trainees, and to compare these factors before and after trainees achieve technical competence. Design of this study was a cross-sectional studies of two time series design for one year at a single center. From March 2011 to February 2012, a total 2,050 subjects who underwent colonoscopy by four first-year gastrointestinal fellows were enrolled at Christian hospital, Wonju, Republic of Korea. Four gastrointestinal fellows have filled out the colonoscopic documentation. Main outcome measurement was predictive factors affecting cecal intubation failure and learning curves. Colonoscopy was successfully completed to the cecum in 1,720 patients (83.9%). Success rates gradually increased as trainees performed more colonoscopies: the rate of SCI was 62% in the first 50 cases, and grew to 93% by the 250th case. Logistic regression analysis of factors affecting cecal intubation failure showed that female gender, low BMI (BMI < 18.5 kg/m2), poor bowel preparation, and past history of stomach surgery were more often associated with cecal intubation failure, particularly before the trainees achieved technical competence. Several patient characteristics were identified that may predict difficulty of cecal intubation in colonoscopy trainees. Particularly, low BMI, inadequate bowel cleansing, and previous stomach operation were predictors of cecal intubation failure before the trainees have reached technical competency. The results could be informative so that trainees enhance the success rate regarding better colonoscopy training programs.

Kim J.H.,Yonsei University
Korean journal of ophthalmology : KJO | Year: 2011

The purpose of this study was to investigate the prevalence and characteristics of glaucoma in the population of the rural Korean town, Sangju. Residents of Sangju aged greater than 50 years old were included in this study. Participants completed an interview examining their medical and ophthalmic history Information was collected on the participants' uncorrected and best corrected vision scores, slit lamp examination results, angle width measurements using the Van Herick technique, gonioscopy if the angle width was less than 1 / 4 angle, intraocular pressure (IOP) assessed with the Goldmann applanation tonometry, optic disc examination results, and a visual field test results using frequency-doubling perimetry in cases in which glaucoma was suspected. Glaucoma was diagnosed according to the criteria described by the International Society for Geographic and Epidemiological Ophthalmology. 1,118 residents aged greater than 50 years were examined initially from a population of 2,984 people. Of these, 671 subjects (60%) participated in this study. The prevalence of glaucoma was determined to be 3.4% (95% confidence interval [CI], 2.1-4.8). Open-angle glaucoma with low IOP was determined to be the most common form with a prevalence rate as high as 2.5% (95% CI, 1.8-3.7). Additionally, primary angle closure glaucoma was determined to have a prevalence rate of 0.3% (95% CI, 0.1-0.9). Open-angle glaucoma with low IOP accounted for 94.4% of the open-angle glaucoma cases. The prevalence of glaucoma among the population of rural Sangju was 3.4%, and open-angle glaucoma with low IOP was the most common form accounting for 94.4% of the total number of cases. © 2011 The Korean Ophthalmological Society

Hypoxia-inducible factor-1α (HIF-1α) is a central transcriptional factor involved in the cellular responses related to various aspects of cancer biology, including proliferation, survival, and angiogenesis, and the metabolism of the extracellular matrix in hypoxia. This study evaluated whether adenovirus-mediated small hairpin RNA (shRNA) against HIF-1α (shHIF-1α) inhibits cell proliferation and angiogenesis in hepatocellular carcinoma (HCC) cell lines. Knockdown of HIF-1α expression was constructed by adenovirus-mediated RNA interference tools, and HCC cell lines infected with shHIF-1α coding virus were cultured under a hypoxia condition (1% O2) for 24 hours. Following infection, the expression levels of HIF-1α, angiogenesis factors, and matrix metalloproteinase (MMP) were examined using Western blotting. Cell proliferation and angiogenesis were measured by a cell proliferation assay (MTT assay) and an angiogenesis-related assay (invasion and tube-formation assay), respectively. Adenovirus mediated inhibition of HIF-1α induced suppression of tumor growth in HCC cell lines. It also down-regulated the expression of angiogenesis factor and MMP proteins. Angiogenesis as well as mobility of vascular cells to tumor was suppressed by adenovirus-mediated shHIF-1α-infected groups in human umbilical vein endothelial cells (HUVECs). These data suggest that adenovirus-mediated inhibition of HIF-1α inhibits the invasion, tube formation, and cell growth in HUVECs and HCC cells.

Barnes S.A.,Lowell Observatory | Kim Y.-C.,Lowell Observatory | Kim Y.-C.,Yonsei University
Astrophysical Journal | Year: 2010

We show here that the rotation period data in open clusters allow the empirical determination of an expression for the rate of loss of angular momentum from cool stars on the main sequence. One significant component of the expression, the dependence on rotation rate, persists from prior work; others do not. The expression has a bifurcation, as before, that corresponds to an observed bifurcation in the rotation periods of coeval open cluster stars. The dual dependencies of this loss rate on stellarmass are captured by two functions, f (B-V ) and T (B-V ), that can be determined from the rotation period observations. Equivalent masses and other [UBVRIJHK] colors are provided in Table 1. Dimensional considerations and a comparison with appropriate calculated quantities suggest interpretations for f and T, both of which appear to be related closely (but differently) to the calculated convective turnover timescale, tc, in cool stars. This identification enables us to write down symmetrical expressions for the angular momentum loss rate and the deceleration of cool stars and also to revive the convective turnover timescale as a vital connection between stellar rotation and stellar activity physics. © 2010. The American Astronomical Society. All rights reserved.

Yun S.,Yonsei University
IEEE Transactions on Computers | Year: 2012

This paper proposes a state encoding scheme called a covered state encoding for the efficient TCAM-based implementation of the Aho-Corasick multipattern matching algorithm, which is widely used in network intrusion detection systems. Since the information of failure transitions of the Aho-Corasick Nondeterministic Finite Automata (NFA) is implicitly captured in the covered state encoding and the failure transition entries can be completely eliminated, the Aho-Corasick NFA can be implemented on a TCAM with smaller number of entries than other schemes. We also propose constructing the modified Aho-Corasick NFA for multicharacter processing, which can be implemented on a TCAM using the covered state encoding. The implementation of modified Aho-Corasick NFA using the covered state encoding is also superior to other schemes in both TCAM memory requirement and lookup speed. © 2006 IEEE.

Recently, Gadoxetic acid (Gd-EOB-DTPA; Primovist®; Bayer Schering Pharma), a tissue-specific contrast material, has been used for clinical MR imaging. This agent is a biphasic hepatobiliary contrast agent because it behaves as both an extracellular and a hepatocyte-specific agent as it undergoes both renal and biliary excretion. Up to 50% of the injected dose is taken up into normal hepatocytes due to the presence of the lipophilic ethoxybenzyl group in its chemical structure. As such, dynamic imaging can be performed using this agent for the evaluation of hemodynamic perfusion or status and for hepatobiliary phase imaging (10 to 20 minutes after injection) for the evaluation of functional status. Compared to extracellular contrast materials, Gadoxetic acid-enhanced magnetic resonance imaging (MRI) provides comparable arterial enhancement and prominent venous washout of hepatocellular carcinoma (HCC) during dynamic imaging. Additional hepatobiliary phase images are useful for the detection of small lesions that are not readily visible during dynamic imaging. Current evidence and experience suggest that Gadoxetic acid-enhanced MRI will improve the accuracy of HCC imaging diagnosis by allowing better characterization of hypovascular lesions and better differentiation of small arterial enhancing lesions as well as by providing improved preoperative staging accuracy. Therefore, with the aid of Gadoxetic acid-enhanced MRI, very early HCC will be more commonly diagnosed, with patient treatment occurring in earlier stages of the disease.

A 63-year-old man with a history of hepatitis-B-related hepatocellular carcinoma (HCC) in the left lateral portion of the liver received repeated transcatheter arterial chemoembolization (TACE) and salvage radiotherapy. Two months after completing radiotherapy, he presented with dysphagia, epigastric pain, and a protruding abdominal mass. Computed tomography showed that the bulging mass was directly invading the adjacent stomach. Endoscopy revealed a fistula from the HCC invading the stomach. Although the size of the mass had decreased with the drainage through the fistula, and his symptoms had gradually improved, he died of cancer-related bleeding and hepatic failure. This represents a case in which an HCC invaded the stomach and caused a hepatogastric fistula after repeated TACE and salvage radiotherapy.

Given the significant role of people in the management of security, attention has recently been paid to the issue of how to motivate employees to improve security performance of organizations. However, past work has been dependent on deterrence theory rooted in an extrinsic motivation model to help understand why employees do or do not follow security rules in their organization. We postulated that we could better explain employees' security-related rule-following behavior with an approach rooted in an intrinsic motivation model. We therefore developed a model of employees' motivation to comply with IS security policies which incorporated both extrinsic and intrinsic models of human behavior. It was tested with data collected through a survey of 602 employees in the United States. We found that variables rooted in the intrinsic motivation model contributed significantly more to the explained variance of employees' compliance than did those rooted in the extrinsic motivation model. © 2011 Elsevier B.V. All rights reserved.

Ahn S.,Yonsei University
Korean journal of radiology : official journal of the Korean Radiological Society | Year: 2011

With the advances in diffusion magnetic resonance (MR) imaging techniques, diffusion tensor imaging (DTI) has been applied to a number of neurological conditions because DTI can demonstrate microstructures of the brain that are not assessable with conventional MR imaging. Tractography based on DTI offers gross visualization of the white matter fiber architecture in the human brain in vivo. Degradation of restrictive barriers and disruption of the cytoarchitecture result in changes in the diffusion of water molecules in various pathological conditions, and these conditions can also be assessed with DTI. Yet many factors may influence the ability to apply DTI clinically, so these techniques have to be used with a cautious hand.

Kim S.G.,Yonsei University
The Korean journal of gastroenterology = Taehan Sohwagi Hakhoe chi | Year: 2013

Since the Korean College of Helicobacter and Upper Gastrointestinal Research has first developed the guideline for the diagnosis and treatment of Helicobacter pylori infection in 1998, the revised guideline was proposed in 2009 by the same group. Although the revised guideline was made by comprehensive review of previous articles and consensus of authoritative expert opinions, the evidence-based developmental process was not applied in the revision of the guideline. This new guideline has been revised especially in terms of changes in the indication and treatment of H. pylori infection in Korea, and developed by the adaptation process as evidence-based method; 6 guidelines were retrieved by systematic review and the Appraisal of Guidelines for Research and Evaluation (AGREE) II process, 21 statements were made with grading system and revised by modified Delphi method. After revision, 11 statements for the indication of test and treatment, 4 statements for the diagnosis and 4 statements for the treatment have been developed, respectively. The revised guideline has been reviewed by external experts before the official endorsement, and will be disseminated for usual clinical practice in Korea. Also, the scheduled update and revision of the guideline will be made periodically.

Guo Z.,Ewha Womans University | Guo Z.,East China University of Science and Technology | Shin I.,Yonsei University | Yoon J.,Ewha Womans University
Chemical Communications | Year: 2012

A boronic acid moiety can bind to nucleophilic species, such as fluoride ions and 1,2-diols, and arylboronates are converted to the corresponding phenols by treatment with hydrogen peroxide. Based on these reactivity profiles of boron compounds, a variety of boronic acid and boronate-based fluorescent chemosensors have been developed for detecting biologically relevant species. This feature article highlights recent advances that have been made in the development of chemosensors of these types for monitoring carbohydrates, dopamine, fluorides, metal ions and hydrogen peroxide. © 2012 The Royal Society of Chemistry.

Yoon S.S.,Yonsei University | Kim E.-K.,Seoul National University | Lee W.-J.,Seoul National University
Current Opinion in Microbiology | Year: 2015

Accumulating data sets of gut microbiome by next-generation sequencing allow us to gain a comprehensive view of the functional diversity of the gut-associated metagenome. However, many microbiome functions are unknown and/or have only been predicted, and may not necessarily reflect the in vivo function within a gut niche. Functional genomic and metagenomic approaches have been successfully applied to broaden the understanding of invertebrate and vertebrate gut microbiome involved in diverse functions, including colonization ability, nutritional processing, antibiotic resistance, microbial physiology and metabolism, and the modulation of the host physiology. In this review, we discuss the recent knowledge obtained from the study of functional genomics and metagenomics of the animal intestine and its potential values for understanding gut microbiota-animal mutualism. © 2015 Elsevier Ltd.

Kim J.-H.,Yonsei University
Obstetrics and Gynecology | Year: 2010

Objective: To estimate the prevalence and seroprevalence of high-risk human papillomavirus (HPV) in Korean girls and women. Methods: We estimated the seroprevalence of HPV subtypes 16 and 18 among 1,094 girls and women aged 9-59 years and the prevalence of genital high-risk HPV among 902 women aged 20-59 years who visited our institution for a medical checkup. Genital high-risk HPV DNA was measured using liquid hybridization and polymerase chain reaction assays. Serum antibodies to HPV subtypes 16 and 18 were measured using a multiplexed competitive luminex technique. Results: The prevalence of genital high-risk HPV was 12.6% among Korean women aged 20-59 years. It reached a peak of 23.2% at 20-29 years of age, decreasing thereafter but increasing again to 12.4% at 50-59 years of age. Human papillomavirus 56 was the most common subtype followed by HPV 18, HPV 52, and HPV 16. The seroprevalence of HPV subtypes 16 and 18 was 8.7% among Korean girls and women aged 9-59 years. It reached its highest peak of 13.4% at 25-29 years of age and decreased thereafter. It then reached a second peak of 10.9% at 40-49 years of age and plateaued thereafter. The seroprevalences of HPV subtypes 16 and 18 were 7.4% and 2.7%, respectively. In multivariable analysis, the prevalence and seroprevalence of high-risk HPV were correlated only with the number of lifetime sexual partners. Conclusion: High-risk HPV infection is common among Korean women. Our epidemiological data on high-risk HPV infection will help to assess vaccine policy and to establish a baseline for estimating vaccine efficacy. © 2010 by The American College of Obstetricians and Gynecologists. Published by Lippincott Williams and Wilkins.

Kwon S.-J.,University of California at Irvine | Song H.-W.,Yonsei University
Cement and Concrete Research | Year: 2010

Carbonation on concrete structures in underground sites or metropolitan cities is one of the major causes of steel corrosion in RC (Reinforced Concrete) structures. For quantitative evaluation of carbonation, physico-chemo modeling for reaction with dissolved CO 2 and hydrates is necessary. Amount of hydrates and CO 2 diffusion coefficient play an important role in evaluation of carbonation behavior, however, it is difficult to obtain a various CO 2 diffusion coefficient from experiments due to limited time and cost. In this paper, a numerical technique for carbonation behavior using neural network algorithm and carbonation modeling is developed. To obtain the comparable data set of CO 2 diffusion coefficient, experimental results which were performed previously are analyzed. Mix design components such as cement content, water to cement ratio, and volume of aggregate including exposure condition of relative humidity are selected as neurons. Training of learning for neural network is carried out using back propagation algorithm. The diffusion coefficient of CO 2 from neural network are in good agreement with experimental data considering various conditions such as water to cement ratios (w/c: 0.42, 0.50, and 0.58) and relative humidities (R.H.: 10%, 45%, 75%, and 90%). Furthermore, mercury intrusion porosimetry (MIP) test is also performed to evaluate the change in porosity under carbonation. Finally, the numerical technique which is based on behavior in early-aged concrete such as hydration and pore structure is developed considering CO 2 diffusion coefficient from neural network and changing effect on porosity under carbonation.

Kwon-Chung K.J.,University of Queensland | Kwon-Chung K.J.,Institute Pasteur Paris | Kwon-Chung K.J.,Yonsei University
Cold Spring Harbor perspectives in medicine | Year: 2014

Cryptococcus neoformans and Cryptococcus gattii are the two etiologic agents of cryptococcosis. They belong to the phylum Basidiomycota and can be readily distinguished from other pathogenic yeasts such as Candida by the presence of a polysaccharide capsule, formation of melanin, and urease activity, which all function as virulence determinants. Infection proceeds via inhalation and subsequent dissemination to the central nervous system to cause meningoencephalitis. The most common risk for cryptococcosis caused by C. neoformans is AIDS, whereas infections caused by C. gattii are more often reported in immunocompetent patients with undefined risk than in the immunocompromised. There have been many chapters, reviews, and books written on C. neoformans. The topics we focus on in this article include species description, pathogenesis, life cycle, capsule, and stress response, which serve to highlight the specializations in virulence that have occurred in this unique encapsulated melanin-forming yeast that causes global deaths estimated at more than 600,000 annually. Copyright © 2014 Cold Spring Harbor Laboratory Press; all rights reserved.

Cho J.Y.,Yonsei University
Journal of Gastric Cancer | Year: 2013

Gastric cancer is the second leading cause of cancer-related deaths worldwide. In advanced and metastatic gastric cancer, the conventional chemotherapy with limited efficacy shows an overall survival period of about 10 months. Patient specific and effective treatments known as personalized cancer therapy is of significant importance. Advances in high-throughput technologies such as microarray and next generation sequencing for genes, protein expression profiles and oncogenic signaling pathways have reinforced the discovery of treatment targets and personalized treatments. However, there are numerous challenges from cancer target discoveries to practical clinical benefits. Although there is a flood of biomarkers and target agents, only a minority of patients are tested and treated accordingly. Numerous molecular target agents have been under investigation for gastric cancer. Currently, targets for gastric cancer include the epidermal growth factor receptor family, mesenchymal-epithelial transition factor axis, and the phosphatidylinositol 3-kinase-AKT-mammalian target of rapamycin pathways. Deeper insights of molecular characteristics for gastric cancer has enabled the molecular classification of gastric cancer, the diagnosis of gastric cancer, the prediction of prognosis, the recognition of gastric cancer driver genes, and the discovery of potential therapeutic targets. Not only have we deeper insights for the molecular diversity of gastric cancer, but we have also prospected both affirmative potentials and hurdles to molecular diagnostics. New paradigm of transdisciplinary team science, which is composed of innovative explorations and clinical investigations of oncologists, geneticists, pathologists, biologists, and bio-informaticians, is mandatory to recognize personalized target therapy. © 2013 by The Korean Gastric Cancer Association.

Choi S.J.,Yonsei University
Biomacromolecules | Year: 2012

Here we ask the fundamental questions about the effect of peptide topology on self-assembly. The study revealed that the self-assembling behaviors of cyclic and linear peptides are significantly different in several respects, in addition to sharing several similarities. Their clear differences included the morphological dissimilarities of the self-assembled nanostructures and their thermal stability. The similarities include their analogous critical aggregation concentration values and cytotoxicity profiles, which are in fact closely related. We believe that understanding topology-dependent self-assembly behavior of peptides is important for developing tailor-made self-assembled peptide nanostructures.

We have derived an analytic model describing the interior temperature difference as a function of the load current of a thermoelectric generator (TEG); we have also proposed a method to extract the intrinsic and extrinsic Seebeck coefficients and resistances of TEG using experimental current-voltage curves. The decrement of internal temperature difference is almost linearly depending on load current of the TEG. From the experimental results, using a thermoelectric (TE) module with a thermal conductance of 3.52. W/K and a parasitic thermal conductance of 50. W/K, the effective internal electrical resistance was increased by approximately 5%, but the effective Seebeck coefficient was attenuated by approximately 13%, as compared to the intrinsic parameters. The relationship between the output power reduction factor and limited thermal conductance of TEG packaging was also derived. Approximately 25% of the maximum output power is lost because of the parasitic thermal resistance of the TE module used in the experiment. © 2012 Elsevier Ltd.

Lee I.,Yonsei University
Animal Cells and Systems | Year: 2013

Various genome-wide approaches to identifying the genetic components that underlie phenotypes in animals and humans have been developed during the last several decades. The relationship between gene and phenotype, however, cannot be represented by a simple one-to-one correspondence. Rather, many genes are typically related to a single phenotype and many phenotypes can be associated with a single gene, a major theme within the study of complex phenotypes. Therefore, to dissect the genetics of complex phenotypes, one must not only identify the genetic components involved but also the relationships between genes. To fulfill this new goal in modern genetics, the field of network science has recently tackled the complexity of phenotypes. There are various types of gene networks, which are defined by their differential representation of network edges (i.e., relationships). Different networks map physical, genetic, functional, and regulatory interactions between genes. Gene networks can be constructed using a wide variety of experimental and computational methods, which provide complimentary information about the genetic organization of phenotypes. The predictive power of a gene network is further augmented via integration with functional genomics or genetics data, including expression, loss-of-function, or chromosomal interval or nucleotide position data associated with a phenotype. Although the field of network-based genetics has made phenomenal progress during the last decade, many limitations, such as the completeness and dynamicity of gene networks, must still be overcome. © 2013 Copyright Korean Society for Integrative Biology.

We aimed to prospectively assess the optimal cutoff value for a minimum lumen cross-sectional area (CSA) on a 64-slice multidetector computed tomography (MDCT) compared with an intravascular ultrasound (IVUS). In 39 patients with 43 stents, the minimum lumen diameter, stent diameter, diameter stenosis, minimum lumen CSA, stent CSA, and area stenosis at the narrowest point were measured independently on 64-slice MDCT and IVUS images. For the assessment of diameter and CSA, 64-slice MDCT showed good correlations with IVUS (r = 0.82 for minimum lumen diameter, r = 0.66 for stent diameter, r = 0.79 for minimum lumen CSA, and r = 0.75 for stent CSA, respectively, P < 0.0001). For the assessment of diameter and area stenoses, a 64-slice MDCT showed good correlations with IVUS (r = 0.89 and 0.91, respectively, P < 0.0001). The overall sensitivity, specificity, positive predictive value, and negative predictive value to detect in-stent area restenosis (≥ 50 % area stenosis) of a 64-slice MDCT were 77, 100, 100, and 91 %, respectively. The cutoff value of a 64-slice MDCT, determined by receiver operator characteristic (ROC) analysis, was 5.0 mm(2) with 76.5 % sensitivity and 92.3 % specificity for significant in-stent area restenosis; the area under the ROC curve was 0.902 (P < 0.0001). A good correlation was found between a 64-slice MDCT and the IVUS, regarding the assessment of diameter and area stenoses of coronary stents in selected patients implanted with stents of more than 3 mm in diameter. Optimal cutoff value for the minimum lumen CSA of coronary stents on the 64-slice MDCT is 5 mm(2) to predict a CSA of 4 mm(2) on IVUS.

Jang J.Y.,Yonsei University
The Korean journal of gastroenterology = Taehan Sohwagi Hakhoe chi | Year: 2012

Portal annular pancreas is one of the pancreatic fusion anomalies in which the uncinate process of the pancreas extends to fuse with the dorsal pancreas by encircling the portal vein or superior mesenteric vein. We report two consecutive patients with portal annular pancreas. The first case is a 71-year-old male patient who underwent a pancreaticoduodenectomy for intraductal papillary mucinous neoplasm in the head of pancreas. His preoperative computed tomography scan showed the suprasplenic type portal annular pancreas. The second case is a 74-year-old female patient who underwent a laparoscopic anterior radical antegrade modular pancreatosplenectomy (RAMPS) for pancreatic body cancer. In operative finding, portal confluence (superior mesenteric vein-splenic vein-portal vein) was encased with the uncinate process of pancreas in both cases. Therefore, they required pancreatic division at the pancreatic neck portion twice. During the postoperative period, grade B and A, respectively, postoperative pancreatic fistulas occurred and were controlled by conservative management. Surgeons need to know about this rare pancreatic condition prior to surgical intervention to avoid complications, and to provide patients with well-designed, case-specific pancreatic surgery.

Kim Y.S.,Yale University | Kim Y.S.,Nathan Kline Institute for Psychiatric Research | Kim Y.S.,Yonsei University | State M.W.,University of California at San Francisco
International Journal of Epidemiology | Year: 2014

Recent advances in the genetics of neurodevelopmental disorder (NDD) have demonstrated that rare mutations play a role not only in Mendelian syndromes, but in complex, common forms of NDDs as well. Strikingly, both common polymorphisms and rare variations in a single gene or genetic locus have been found to carry risk for conditions previously considered to be clinically and aetiologically distinct. Recent developments in the methods and tools available for studying complex NDDs have led to systematic and reliable genome-wide variant discovery. Both common as well as rare, and structural as well as sequence, genetic variations have been identified as contributing to NDDs. There are multiple examples in which the identical variant had been found to contribute to a wide range of formerly distinct diagnoses, including autism, schizophrenia, epilepsy, intellectual disability and language disorders. These include variations in chromosomal structure at 16p11.2, rare de novo point mutations at the gene SCN2A, and common single nucleotide polymorphisms (SNPs) mapping near loci encoding the genes ITIH3, AS3MT, CACNA1C and CACNB2. These selected examples point to the challenges to current diagnostic approaches. Widely used categorical schema have been adequate to provide an entré into molecular mechanisms of NDDs, but there is a need to develop an alternative, more biologically-relevant nosology.Thus recent advances in gene discovery in the area of NDDs are leading to a re-conceptualization of diagnostic boundaries. Findings suggest that epidemiological samples may provide important new insights into the genetics and diagnosis of NDDs and that other areas of medicine may provide useful models for developing a new diagnostic nosology, one that simultaneously integrates categorical diagnoses, biomarkers and dimensional variables. © The Author 2014; all rights reserved.

The mortality rate from cardiovascular disease (CVD) among young adults has declined less than that in the older population, raising concerns about the increasing prevalence of obesity-related conditions including hypercholesterolemia in the younger population. We investigated the age-standardized mean levels of serum cholesterols and the prevalence, awareness, treatment and control rates of hyper-low-density lipoprotein (LDL)-cholesterolemia based on age. Nationally representative samples of 19 489 subjects aged ≥20 years were analyzed from the Korea National Health and Nutrition Examination Surveys 2008-2010. Hyper-LDL-cholesterolemia was individually evaluated by the 2004 National Cholesterol Education Program Adult Treatment Panel III guidelines. Age-standardized mean levels of total cholesterol, high-density lipoprotein-cholesterol, LDL-cholesterol, and triglycerides were 186.8, 48.0, 112.9, and 136.0 mg/dL, respectively. Age-standardized prevalence of hyper-LDL-cholesterolemia was 23.2% (men, 25.5%; women, 21.8%). Among subjects with hyper-LDL-cholesterolemia, awareness and treatment rates were significantly lower in younger adults (<50 years) compared to older adults ≥50 years (awareness, 8.0% versus 21.5%; treatment, 5.1% versus 18.5%, all Ps<0.001), indicating significant discrepancies in awareness and treatment rates of hypercholesterolemia between younger and older adults. Among subjects aware of their hyper-LDL-cholesterolemia, younger adults were more likely to have controlled LDL-cholesterol than the elderly (82.1% versus 67.5%, P<0.001). Compared to the elderly, significant proportions of young and middle-aged adults are unaware of their hypercholesterolemia and are not treated with proper lipid-lowering medications. Early screening, education, and proper management should be stressed in national public healthcare policies to reduce the increasing burden of CVD in the younger population with undiagnosed hypercholesterolemia.

Chu Y.H.,Sangji University | Shul Y.G.,Yonsei University
International Journal of Hydrogen Energy | Year: 2010

Low-temperature direct alcohol fuel cells fed with different kinds of alcohol (methanol, ethanol and 2-propanol) have been investigated by employing ternary electrocatalysts (Pt-Ru-Sn) as anode catalysts. Combinatorial chemistry has been applied to screen the 66-PtRuSn-anode arrays at the same time to reduce cost, time, and effort when we select the optimum composition of electrocatalysts for DAFCs (Direct Alcohol Fuel Cells). PtRuSn (80:20:0) showed the lowest onset potential for methanol electro-oxidation, PtRuSn (50:0:50) for ethanol, and PtRuSn (20:70:10) for 2-propanol in CV results respectively, and single cell performance test indicated that Ru is more suitable for direct methanol fuel cell system, Sn for direct ethanol fuel cell system, and 2-propanol could be applied as fuel with low platinum composition anode electrocatalyst. The single cell performance results and electrochemical results (CV) were well matched with the combinatorial electrochemical results. As a result, we could verify the availability of combinatorial chemistry by comparing the results of each extreme electrocatalysts compositions as follows: PtRuSn (80:20:0) for methanol, PtRuSn (50:0:50) for ethanol and PtRuSn (20:70:10) for 2-propanol. © 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.

Espinoza S.E.,University of Texas Health Science Center at San Antonio | Jung I.,Yonsei University | Hazuda H.,University of Texas Health Science Center at San Antonio
Journal of the American Geriatrics Society | Year: 2012

OBJECTIVES: To examine frailty transitions in Mexican American (MA) and European American (EA) older adults. DESIGN: Longitudinal, observational cohort study. SETTING: Socioeconomically diverse neighborhoods in San Antonio, Texas. PARTICIPANTS: Three hundred twelve MA and 285 EA community-dwelling older adults (≥65) with frailty information at baseline (1992-1996) and transition information at follow-up (2000/01) in the San Antonio Longitudinal Study of Aging. MEASUREMENTS: Five frailty characteristics (weight loss, exhaustion, weakness, slowness, and low physical activity), frailty score (0-5), and overall frailty state (non-frail = 0 characteristics, prefrail = 1 or 2, frail = ≥3) were assessed at baseline. Transitions (progressed, regressed, or no change) were assessed for frailty score and state. Odds ratios (ORs) of progression and regression in individual characteristics were estimated using generalized estimating equations adjusted for age, sex, ethnic group, socio-economic status, comorbidity, diabetes, and follow-up interval. RESULTS: Diabetes mellitus with macrovascular complications (OR = 1.84, 95% confidence interval (CI) = 1.02-3.33), fewer years of education (OR = 0.96, 95% CI = 0.93-1.0) and follow-up interval (OR = 1.3, 95% CI = 1.17-1.46) were significant predictors of progression in any frailty characteristic. Mortality increased with greater frailty state, and prefrail individuals were more likely than frail individuals to regress. CONCLUSION: Diabetes mellitus with macrovascular complications and fewer years of education are important predictors of progression in any frailty characteristic. Because of greater risk of death than for the nonfrail state and greater likelihood of regression than for the frail state, the prefrail state may be an optimal target for intervention. © 2012, Copyright the Authors Journal compilation © 2012, The American Geriatrics Society.

Lee J.J.,Yonsei University
Energy Conversion and Management | Year: 2010

An aircraft is composed of systems that convert fuel energy to mechanical energy in order to perform work-the movement of people and cargo. Today, the fast-growing demand for air travel has outpaced the rate of improvement in the energy efficiency of aircraft systems. The increase in the total energy consumption and environmental impact of aviation necessitates a strategy to induce further technological and operational innovations to mitigate the increase in aircraft energy use and environmental effects. However, the uncertainty associated with the climate effects of jet engine emissions hinders further improvement to the energy efficiency of aircraft systems. Also the unique characteristics (e.g., trade-off between emissions species) of aircraft systems make it difficult to focus on abatement efforts. Based on a short review of how aircraft technology and operations relate to energy use and the future outlook for aircraft performance, energy use, and environmental impact, the key technology and policy issues related to improving the energy efficiency of aircraft systems are presented. Then, the drivers of technological change in aircraft systems are examined. Government regulation effects and industry characteristics as they relate to improvement of energy use are also presented. Based on these discussions, this paper provides insights on how to accelerate the induction of energy efficient, environmentally friendly innovations. © 2009 Elsevier Ltd. All rights reserved.

Kim T.I.,Yonsei University
World Journal of Gastroenterology | Year: 2014

Recent epidemiological studies, basic research and clinical trials on colorectal cancer (CRC) prevention have helped identify candidates for effective chemopreventive drugs. However, because of the conflicting results of clinical trials or side effects, the effective use of chemopreventive drugs has not been generalized, except for patients with a high-risk for developing hereditary CRC. Advances in genetic and molecular technologies have highlighted the greater complexity of carcinogenesis, especially the heterogeneity of tumors. We need to target cells and processes that are critical to carcinogenesis for chemoprevention and treatment of advanced cancer. Recent research has shown that intestinal stem cells may serve an important role in tumor initiation and formation of cancer stem cells. Moreover, studies have shown that the tumor microenvironment may play additional roles in dedifferentiation, to enable tumor cells to take on stem cell features and promote the formation of tumorigenic stem cells. Therefore, early tumorigenic changes of stem cells and signals for dedifferentiation may be good targets for chemoprevention. In this review, I focus on cancer stem cells in colorectal carcinogenesis and the effect of major chemopreventive drugs on stem cell-related pathways. © 2014 Baishideng Publishing Group Co., Limited. All rights reserved.

Hypoxia is known to be important in the generation and maintenance of stemness; however, its clinical significance is yet to be determined in human hepatocellular carcinoma. The expression of stemness (K19, EpCAM) and hypoxia (carbonic anhydrase-IX (CAIX))-related markers were investigated by immunohistochemistry in three hepatocellular carcinoma cohorts. The clinicopathologic features, response to transarterial chemoembolization, and outcomes were compared. In cohort 1 (n=14, biopsy-transarterial chemoembolization-resection-matched hepatocellular carcinoma), all K19-, EpCAM-, or CAIX-positive hepatocellular carcinomas on initial biopsy (6/6, 100%) showed residual tumors after transarterial chemoembolization, whereas 75% (6/8) of all-negative hepatocellular carcinomas on biopsy showed complete necrosis in the post-transarterial chemoembolization-resected specimens. In cohort 2 (n=85, explanted hepatocellular carcinomas with/without transarterial chemoembolization; totally necrotic hepatocellular carcinoma after transarterial chemoembolization was not included), the expression of K19, EpCAM, and CAIX, and their coexpression, was more frequently observed with a greater number of transarterial chemoembolization sessions, and the expression of these markers was also correlated to each other. CAIX expression was shown to be an independent factor for recurrence and survival, and combination of CAIX with Milan criteria significantly increased the time-dependent integrative area under the curve values for recurrence and survival. In cohort 3 (n=339, resected hepatocellular carcinomas without transarterial chemoembolization), CAIX(+) hepatocellular carcinomas exhibited higher K19 and EpCAM expression, and more invasive pathological features. CAIX expression and TNM stage were independent predictors of extrahepatic recurrence, and the addition of CAIX to the TNM stage significantly increased time-dependent integrative area under the curve values. In conclusion, the expression of stemness (K19, EpCAM) and hypoxia (CAIX)-related markers were correlated each other, and hepatocellular carcinoma expressing these markers showed resistance to transarterial chemoembolization and poorer outcome. Evaluation for both markers of stemness and hypoxia may have an additional value in predicting hepatocellular carcinoma outcome, especially for transarterial chemoembolization-treated hepatocellular carcinomas.Modern Pathology advance online publication, 17 June 2016; doi:10.1038/modpathol.2016.111. © 2016 United States & Canadian Academy of Pathology

Lee J.,Yonsei University | Randolph M.,University of Western Australia
Journal of Geotechnical and Geoenvironmental Engineering | Year: 2011

Estimation of spudcan penetration resistance is an important design step to guarantee the stability and functionality of offshore mobile jack-up units. Dependence on in situ penetrometer test data to evaluate the stratigraphy and resulting spudcan capacity profile has been increased. However, this becomes difficult in intermediate soil types in which the degree of consolidation during penetration falls between the extremes of fully drained or fully undrained. In this study, a penetrometer-based methodology utilizing results from cone and T-bar penetration tests is developed. Three main steps are involved, comprising estimation of the relative penetration resistance of spudcan and cone or T-bar penetrometer under fully drained and fully undrained conditions, and then quantifying the effect of the different normalized penetration rates for spudcan and penetrometer. Values of the various correlation parameters for the proposed model are evaluated. The validity and accuracy of the proposed methodology are evaluated through case studies from centrifuge tests in clay and a field example of spudcan installation in interbedded carbonate silts and sands. The comparisons confirm the potential of the proposed methodology for interpretation of penetrometer tests and application to the prediction of foundation performance. © 2011 American Society of Civil Engineers.

Moore K.S.,Elmhurst College | Yi D.-J.,Yonsei University | Chun M.,Yale University
Journal of Cognitive Neuroscience | Year: 2013

Fundamental to our understanding of learning is the role of attention. We investigated how attention affects two fMRI measures of stimulus-specific memory: repetition suppression (RS) and pattern similarity (PS). RS refers to the decreased fMRI signal when a stimulus is repeated, and it is sensitive to manipulations of attention and task demands. In PS, region-wide voxel-level patterns of responses are evaluated for their similarity across repeated presentations of a stimulus. More similarity across presentations is related to better learning, but the role of attention on PS is not known. Here, we directly compared these measures during the visual repetition of scenes while manipulating attention. Consistent with previous findings, we observed RS in the scene-sensitive parahippocampal place area only when a scene was attended both at initial presentation and upon repetition in subsequent trials, indicating that attention is important for RS. Likewise, we observed greater PS in response to repeated pairs of scenes when both instances of the scene were attended than when either or both were ignored. However, RS and PS did not correlate on either a scene-by-scene or subject-by-subject basis, and PS measures revealed above-chance similarity even when stimuli were ignored. Thus, attention has different effects on RS and PS measures of perceptual repetition. © 2013 Massachusetts Institute of Technology.

This study is intended to examine the role of bridges in sexually transmitted infection (STI) transmission dynamics as an emerging property that is an unintended and aggregate result of individual behaviours or preferences. It also provides an empirical illustration using a newly customised measure of bridging activities--namely, 'walk-betweenness'. Participants in the Chicago Sexual Acquisition and Transmission of HIV Cooperative Agreement Program (SATHCAP) recruited from August 2005 through October 2006 were used in the analysis. They were recruited through respondent-driven bias-adjusted snowball sampling, beginning with six 'seed' recruiters who were given seven coded coupons to distribute to eligible peers for inclusion in the study: three coupons for drug users or men who have sex with men (MSM) regardless of drug use; three coupons for sexual partners; and one coupon for either a non-drug-using sex partner or, if the seed participant was an MSM, for a female sex partner. A walk-betweenness score was created for each of the 77 community areas in Chicago. The SATHCAP questionnaire was used to ask respondents for the neighbourhood locations in which they had had sex in the previous 6 months. The total number of respondents was 1068. The results of the study confirm the existence of hidden bridging communities in the Chicago area. Although these communities were essential to AIDS transmission, they might have been largely ignored because of their low prevalence rates. The role of bridging positions in STI transmission dynamics can be considered as an emerging property that is an aggregate result from individual sexual behaviours or preferences. A newly customised measure of bridging positions is needed to identify this property adequately.

Jung K.S.,Yonsei University
Clinical and molecular hepatology | Year: 2012

Chronic liver disease represents a major public health problem, accounting for significant morbidity and mortality worldwide. As prognosis and management depend mainly on the amount and progression of liver fibrosis, accurate quantification of liver fibrosis is essential for therapeutic decision-making and follow-up of chronic liver diseases. Even though liver biopsy is the gold standard for evaluation of liver fibrosis, non-invasive methods that could substitute for invasive procedures have been investigated during past decades. Transient elastography (TE, FibroScan®) is a novel non-invasive method for assessment of liver fibrosis with chronic liver disease. TE can be performed in the outpatient clinic with immediate results and excellent reproducibility. Its diagnostic accuracy for assessment of liver fibrosis has been demonstrated in patients with chronic viral hepatitis; as a result, unnecessary liver biopsy could be avoided in some patients. Moreover, due to its excellent patient acceptance, TE could be used for monitoring disease progression or predicting development of liver-related complications. This review aims at discussing the usefulness of TE in clinical practice.

Jang J.-H.,Yonsei University | Schaffer D.V.,University of California at Berkeley | Shea L.D.,Northwestern University
Molecular Therapy | Year: 2011

Integrating viral gene delivery with engineered biomaterials is a promising strategy to overcome a number of challenges associated with virus-mediated gene delivery, including inefficient delivery to specific cell types, limited tropism, spread of vectors to distant sites, and immune responses. Viral vectors can be combined with biomaterials either through encapsulation within the material or immobilization onto a material surface. Subsequent biomaterial-based delivery can increase the vector's residence time within the target site, thereby potentially providing localized delivery, enhancing transduction, and extending the duration of gene expression. Alternatively, physical or chemical modification of viral vectors with biomaterials can be employed to modulate the tropism of viruses or reduce inflammatory and immune responses, both of which may benefit transduction. This review describes strategies to promote viral gene delivery technologies using biomaterials, potentially providing opportunities for numerous applications of gene therapy to inherited or acquired disorders, infectious disease, and regenerative medicine. © The American Society of Gene & Cell Therapy.

Roth J.,Yonsei University
Histochemistry and Cell Biology | Year: 2011

Lectins have been proven to be invaluable reagents for the histochemical detection of glycans in cells and tissues by light and electron microscopy. This technical review deals with the conditions of tissue fixation and embedding for lectin labeling, as well as various markers and related labeling techniques. Furthermore, protocols for lectin labeling of sections from paraffin and resin-embedded tissues are detailed together with various controls to demonstrate the specificity of the labeling by lectins. © 2011 Springer-Verlag.

Min Nam Y.,Seoul National University | Huh J.,Yonsei University | Ho Jo W.,Seoul National University
Solar Energy Materials and Solar Cells | Year: 2010

A two-dimensional model accounting for the effect of both the morphology of active layer and the layer configuration of multilayer-structured device on the device performance, is developed to optimize the device parameter for high performance of the bulk-heterojunction organic solar cells. When the photovoltaic properties of poly(3-hexylthiophene)/[6,6]-phenyl C61-butyric acid methyl ester solar cells are calculated as functions of device parameters by using the model, it is found that the optimum thickness of active layer is 80 nm and that the domain size in active layer is about 6 nm. Comparison of simulation with experiment reveals that the simulated short-circuit current as a function of active layer thickness is very consistent with experimental one. © 2010 Elsevier B.V. All rights reserved.

Shin M.W.,Yonsei University | Jang S.H.,Dong - A University
Organic Electronics: physics, materials, applications | Year: 2012

This paper reports on the direct thermal observation of the pentacene - based organic thin-film transistors (OTFTs) under the real operating conditions. Liquid crystal (LC) spreading method was utilized for the thermal investigation of an active layer of the OTFT package. Temperature variation in the OTFT package was recorded for the different input power and significant heat generation was observed in the confined active layer. Detailed thermal performance of the OTFT package was projected using a Computational Fluid Dynamics (CFD) method as well. It was shown that the driving of the OTFT package with the drain voltage of -15 V resulted in the active layer temperature of about 53.2 °C. The result indicates that the device design with effective thermal dissipation is imperative for reliable operation of the OTFT package. © 2012 Elsevier B.V. All rights reserved.

Lee J.,Eulji University | Chung W.Y.,Yonsei University
Cancer Journal (United States) | Year: 2013

The advantages of endoscopic thyroidectomy and neck dissection include reduced hyperesthesia or paresthesia in the neck and favorable cosmetic outcomes. However, endoscopic thyroidectomy with neck dissection has a long learning curve, as well as technical limitations associated with a 2-dimensional view and a reduced dexterity of movement, particularly when operating in deep and narrow spaces such as the neck area. A robotic approach has been developed to overcome these limitations, facilitating manipulation and shortening the learning curve. This system enables the surgeon to control the 3-dimensional high-definition camera, reducing physiological tremors and enabling free dexterity of movement using articulated instruments. Therefore, robotic surgery has been found to eliminate many problems encountered with conventional endoscopic techniques.Recently, robotic thyroidectomy with neck dissection via a gasless transaxillary approach was shown to yield similar oncologic outcomes as conventional open procedures, as determined by postoperative radioactive iodine scans, serum thyroglobulin concentrations, and number of retrieved cervical lymph nodes. We also found that the robotic technique was safe and feasible in thyroid cancer patients, yielding excellent cosmetic results, reduced pain, improved sensory changes and decreased postoperative voice changes and swallowing discomfort. For surgeons, the use of a robot offers a shorter operation time and the need for a shorter learning curve than conventional endoscopic thyroidectomy. Robotic thyroidectomy also causes less musculoskeletal discomfort to surgeons than open or endoscopic thyroidectomy. The advantages of robotic surgery over open or endoscopic surgery suggest that robotic thyroidectomy with neck dissection may become the preferred surgical option for patients with thyroid cancer. Further analyses of surgeons' experience, assessments of long-term outcomes, and randomized controlled trials remain important. Copyright © 2013 by Lippincott Williams & Wilkins.

Yun M.,Yonsei University
Journal of Gastric Cancer | Year: 2014

Aerobic glycolysis has been the most important hypothesis in cancer metabolism. It seems to be related to increased bioenergetic and biosynthetic needs in rapidly proliferating cancer cells. To this end, F-18 fluorodeoxyglucose (FDG), a glucose analog, became widely popular for the detection of malignancies combined with positron emission tomography/computed tomography (PET/CT). Although the potential roles of FDG PET/CT in primary tumor detection are not fully established, it seems to have a limited sensitivity in detecting early gastric cancer and mainly signet ring or non-solid types of advanced gastric cancer. In evaluating lymph node metastases, the location of lymph nodes and the degree of FDG uptake in primary tumors appear to be important factors affecting the diagnostic accuracy of PET/ CT. In spite of the limited sensitivity, the high specificity of PET/CT for lymph node metastases may play an important role in changing the extent of lymphadenectomy or reducing futile laparotomies. For peritoneal metastases, PET/CT seems to have a poorer sensitivity but a better specificity than CT. The roles of PET/CT in the evaluation of other distant metastases are yet to be known. Studies including primary tumors with low FDG uptake or peritoneal recurrence seem suffer from poorer diagnostic performance for the detection of recurrent gastric cancer. There are only a few reports using FDG PET/CT to predict response to neoadjuvant or adjuvant chemotherapy. A complete metabolic response seems to be predictive of more favorable prognosis. © 2014 by The Korean Gastric Cancer Association.

Glassman M.,Ohio State University | Kang M.J.,Yonsei University
Computers in Human Behavior | Year: 2012

This paper introduces the concept of Open Source Intelligence (OSINT) as an important component for understanding human problem solving in the 21st century. OSINT is in many ways the result of changing human-information relationships resulting from the emergence and growing dominance of the Internet and the World Wide Web in everyday life. This paper suggests that the Internet/Web changes the dynamic relationship between what Cattell and Horn have identified as the two general factors of human intelligence: crystallized intelligence and fluid intelligence. The Internet/Web open up new possibilities for accessing information and transcending over-determined cultural intelligence in problem solving. This offers fluid intelligence, which often trails off in adulthood, a new vitality across the lifespan. But the diminishment of crystallized intelligence, and especially cultural intelligence, also presents a number of important problems in maintenance of cohesive, social cooperatives. The development of OSINT (using tools and ethos created by the Open Source movement of the last few decades) offers both a framework for reaching beyond the boundaries of traditional cultural intelligence and ways to create cooperative, open, problem solving communities. The Internet/Web will continue to create confusion and fear as we move deeper into this new age, but also presents extraordinary possibilities for augmenting human intellect if we can understand it and learn to harness its potential. © 2011 Elsevier Ltd. All rights reserved.

Ha S.K.,Yonsei University
Electrolyte and Blood Pressure | Year: 2014

Over the past century, salt has been the subject of intense scientific research related to blood pressure elevation and cardiovascular mortalities. Moderate reduction of dietary salt intake is generally an effective measure to reduce blood pressure. However, recently some in the academic society and lay media dispute the benefits of salt restriction, pointing to inconsistent outcomes noted in some observational studies. A reduction in dietary salt from the current intake of 9-12 g/day to the recommended level of less than 5-6 g/day will have major beneficial effects on cardiovascular health along with major healthcare cost savings around the world. The World Health Organization (WHO) strongly recommended to reduce dietary salt intake as one of the top priority actions to tackle the global non-communicable disease crisis and has urged member nations to take action to reduce population wide dietary salt intake to decrease the number of deaths from hypertension, cardiovascular disease and stroke. However, some scientists still advocate the possibility of increased risk of CVD morbidity and mortality at extremes of low salt intake. Future research may inform the optimal sodium reduction strategies and intake targets for general populations. Until then, we have to continue to build consensus around the greatest benefits of salt reduction for CVD prevention, and dietary salt intake reduction strategies must remain at the top of the public health agenda. Copyright © 2014 The Korean Society of Electrolyte Metabolism.

Park H.S.,Yonsei University
Sensors (Basel, Switzerland) | Year: 2013

This study describes a wireless laser displacement sensor node that measures displacement as a representative damage index for structural health monitoring (SHM). The proposed measurement system consists of a laser displacement sensor (LDS) and a customized wireless sensor node. Wireless communication is enabled by a sensor node that consists of a sensor module, a code division multiple access (CDMA) communication module, a processor, and a power module. An LDS with a long measurement distance is chosen to increase field applicability. For a wireless sensor node driven by a battery, we use a power control module with a low-power processor, which facilitates switching between the sleep and active modes, thus maximizing the power consumption efficiency during non-measurement and non-transfer periods. The CDMA mode is also used to overcome the limitation of communication distance, which is a challenge for wireless sensor networks and wireless communication. To evaluate the reliability and field applicability of the proposed wireless displacement measurement system, the system is tested onsite to obtain the required vertical displacement measurements during the construction of mega-trusses and an edge truss, which are the primary structural members in a large-scale irregular building currently under construction. The measurement values confirm the validity of the proposed wireless displacement measurement system and its potential for use in safety evaluations of structural elements.

Park S.J.,Yonsei University
Library Hi Tech | Year: 2012

Purpose: The purpose of this study is to provide a full understanding of library use patterns in their full temporal and spatial environment. By analyzing individuals' daily travel activity, this study seeks to measure the travel distance and travel time of library users in multi-destination trip settings. Design/methodology/approach: The data set for analysis was collected from the Metropolitan Travel Survey Archive, which stores 79 household daily travel data sets. Daily activities of 409 people who visited public libraries were extracted from the Puget Sound Region data set. Findings: Through the analysis, four library access patterns were identified: single-destination, en route, base camp, and trip-chaining trips. Only 20 percent of library users made single-destination trips, while 80 percent of users made trips of a multi-destination nature; these are depicted by the latter three listed patterns. In particular, 62.2 percent of the activities fell into the trip-chaining travel pattern. Such a pattern is defined as "discretionary activities which include a library visit." Findings indicate that although travel distance is still a constraint to library access, travel time is a more informative factor than travel distance for gaining a richer understanding of the nature of library visits. Originality/value: This study develops new measurements of travel distance and time, D library and T library respectively, enabling more accurate measures of travel distance and time, and further supporting precise measurements of the portions of multi-destination trips most relevant to library visits. © Emerald Group Publishing Limited.

Choi E.K.,Yonsei University
Spinal Cord | Year: 2014

Study design:Experimental, prospective study.Objectives:We evaluated the long-term clinical efficacy of transanal irrigation (TAI) and its effect on the quality of life of spina bifida children and their caregivers.Setting:Republic of Korea.Method:Forty-four spina bifida pediatric patients with constipation, fecal incontinence or both, underwent a TAI program at our spina bifida clinic between December 2010 and October 2013. The children and their caregivers were evaluated using a self-administered questionnaire before TAI and at 3 months and 3 years after initiation of the program.Results:Successful treatment outcome was achieved in 38 (86.4%) children after a mean follow-up duration of 33 months (range, 30–36). The mean number of fecal incontinence episodes per week, the number of diaper changes and the total time for bowel care per day before the program decreased at the latest follow-up examination from 7.3 to 0.4 (P<0.001), 1.6 to 0.2 (P<0.001) and 29.2 to 19.4 min (P=0.038), respectively. These results remained constant from short-term follow-up at 3 months to 3 years. Caregivers and children could go out more often (P=0.002), and the emotional impact of bowel care on caregivers decreased (P<0.001). The reported mean overall satisfaction with TAI was 8/10. The common adverse effect during TAI was abdominal discomfort (60.5%).Conclusion:We observed a sustained significant improvement in defecation symptoms and quality of life for 3 years in spina bifida children who underwent continuous TAI.Spinal Cord advance online publication, 23 December 2014; doi:10.1038/sc.2014.234. © 2014 International Spinal Cord Society

Kim H.-W.,Yonsei University | Chan H.C.,National University of Singapore | Kankanhalli A.,National University of Singapore
Information Systems Research | Year: 2012

The sale of digital items, such as avatars and decorative objects, is becoming an important source of revenue for virtual community (VC) websites. However, some websites are unable to leverage this source of revenue, and there is a corresponding lack of understanding about what motivates people to purchase digital items in VCs. To explain the phenomenon, we develop a model based on the theory of self-presentation. The model proposes that the desire for online self-presentation is a key driver for such purchases. We also hypothesize that the social influence factors of online self-presentation norms and VC involvement as well as personal control in the form of online presentation self-efficacy are antecedents of the desire for online self-presentation. The model was validated by using survey data collected from Cyworld (N D217) and Habbo (N D197), two online social network communities that have been pioneers in the sale of digital items. This work contributes to our understanding of the purchase of digital items by extending the theory of self-presentation and adds to the broader line of research on online identity. It also lends insights into how VC providers can tap this source of revenue. © 2012 INFORMS.

Lee H.,Yonsei University
Korean journal of ophthalmology : KJO | Year: 2010

PURPOSE: To assess quality of life and depressive status in Korean patients with Graves' ophthalmopathy. METHODS: A cross-sectional study of 49 patients (mean age, 41 years; sex ratio, M:F=11:38) with Graves' ophthalmopathy (referred to as the Graves' group) and 48 age-matched and sex-matched controls (mean age, 40.2 years; sex ratio, M:F=11:37) was performed using the Korean version of the 36-item Short-Form General Health Survey (SF-36) questionnaire and the Beck Depression Inventory (BDI). Survey data was compared among patients with mild, moderately severe, and sight-threatening Graves' ophthalmopathy and between patients with low (0 or 1) or high (2 or 3) Gorman scores. RESULTS: Those in the Graves' group scored significantly lower on all categories of the SF-36, as compared to the control group (p<0.05). The 4 patients with sight-threatening Graves' had significantly lower scores for physical functioning, role limitations due to physical health, and the physical component summary of the SF-36, when compared with the 28 patients with mild Graves' and the 17 patients with moderately severe Graves' (p<0.05). The 17 patients in the high Gorman score group had lower physical component summary scores than the 32 patients in the low Gorman score group (p=0.03). The 16 patients with BDI scores > or = 16 had significantly lower scores on the SF-36 and higher clinical activity scores, as compared to the 33 patients with BDI scores <16 (p<0.05). CONCLUSIONS: Patients with Graves' ophthalmopathy had reduced health-related quality of life and were more likely to be depressed, especially those with a sight threatening condition or significant diplopia. It is important to identify these patients to provide the necessary psychological support.

Lee K.H.,Yonsei University
Journal of the Korean Medical Association | Year: 2015

After the 15 days from the first confirmed case of Middle East respiratory syndrome (MERS) in South Korea on May 20, 2015, the MERS infected case from emergency room (ER) was recognized. I provide the review of characteristics and prevention plan of re-outbreak of a MERS coronavirus at the ER in South Korea. Emergency medical services-related infections with MERS coronavirus have been reported 91 cases (49%) of total 186 cases in South Korea. The first patient was diagnosed with the ER and spent at least 3 days in a busy ER until he was admitted to an isolated room. The causes of MERS's spreading in ER are mainly due to emergency department (ED) overcrowding, long ED stay time, improper infection control system in ED, and a failure of emergency medical service coordination system in South Korea. Early and rapid detection of suspected infected patients with communicable diseases along with appropriate infection control system in ED, reducing the ED overcrowding and ER stay time would help to prevent the disease transmission in ED. © Korean Medical Association.

Kim D.H.,Yonsei University | Kim W.T.,Cheongju University | Park E.S.,Seoul National University | Mattern N.,Leibniz Institute for Solid State and Materials Research | And 2 more authors.
Progress in Materials Science | Year: 2013

Phase separation phenomena in metallic glass systems are reviewed. First, a brief introduction to the enhanced glass forming ability and the phase separation in metallic glass systems is given. Nano-scale phase separation observed in frozen-in glass is discussed in marginal glass formers such as Pd-, Fe, Al-base metallic glass systems as well as in bulk glass formers in Cu-, Zr- and Mg-base metallic glass systems. Since retention of glass forming ability is essential in phase separating glasses, thermodynamic and kinetic conditions for enhanced glass forming ability is introduced. Several thermodynamic aspects for decomposition by liquid-liquid phase separation which include stability conditions, decomposition in the multicomponent system, types of miscibility gap, calculation of bimodal and spinodal curves are introduced as a background for design of metallic glasses phase separating in the liquid state. The main mechanisms for phase separation are nucleation and growth mechanism and spinodal decomposition mechanism. The metallic glass systems which include an atom pair with large positive enthalpy of mixing decompose by liquid-liquid phase separation separate in the liquid state, forming two typical types of microstructure: droplet or interconnected type microstructures depending on the mechanism of phase separation. By calculation of the tile line, it is possible to design phase separating metallic glasses with high glass forming ability. Eventually, bulk-type phase separating metallic glasses with mm scale can be synthesized. Moreover, if there is a group of three atoms with large positive enthalpy of mixing in the liquid state in the multicomponent system, occurrence of three phase separation in the liquid state is possible. There are several parameters affecting the microstructure evolution during phase separation, which includes glass transition and critical temperatures, shape of bimodal and spinodal curves and quenching conditions. Phase separation in the solid state of the frozen-in glasses can give a clue on the phase separation prior to crystallization or direct nanocrystallization from the amorphous matrix. The amplitude of the composition fluctuation with a fixed wavelength can grow by heating in the solid state, if the spinodal decomposition. Finally, some advantages of phase separation phenomena in metallic glass systems are highlighted. © 2013 Elsevier Ltd. All rights reserved.

BACKGROUND AND AIM: Social factors may be of importance causally and act as maintenance factors in patients with anorexia nervosa. Oxytocin is a neuromodulatory hormone involved in social emotional processing associated with attentional processes. This study aimed to examine the impact of oxytocin on attentional processes to social faces representing anger, disgust, and happiness in patients with anorexia nervosa.METHOD: A double-blind, placebo-controlled within-subject crossover design was used. Intranasal oxytocin or placebo followed by a visual probe detection task with faces depicting anger, disgust, and happiness was administered to 64 female subjects: 31 patients with anorexia nervosa and 33 control students.RESULTS: Attentional bias to the disgust stimuli was observed in both groups under the placebo condition. The attentional bias to disgust was reduced under the oxytocin condition (a moderate effect in the patient group). Avoidance of angry faces was observed in the patient group under the placebo condition and vigilance was observed in the healthy comparison group; both of these information processing responses were moderated by oxytocin producing an increase in vigilance in the patients. Happy/smiling faces did not elicit an attentional response in controls or the patients under either the placebo or oxytocin conditions.CONCLUSION: Oxytocin attenuated attentional vigilance to disgust in patients with anorexia nervosa and healthy controls. On the other hand, oxytocin changed the response to angry faces from avoidance to vigilance in patients but reduced vigilance to anger in healthy controls. We conclude that patients with anorexia nervosa appear to use different strategies/circuits to emotionally process anger from their healthy counterparts.

Hong T.-K.,Yonsei University
Tectonophysics | Year: 2014

Regional seismic analysis is an only way to investigate the source properties of small or moderate-sized seismic events that occur in physically unaccessible regions such as oceanic regions and politically-prohibited regions. The ground motions by earthquakes need to be understood for better mitigation of seismic hazards particularly in continental margins that often incorporate high seismicity. It has not been fully understood how seismic waves interact with complex crustal structures in continental margins. Responses of regional waves to complex crustal structures need to be quantified. Analysis of regional waveforms from controlled sources is desirable for investigation of influence of crustal structures. The influence of continental margin around the Korean Peninsula is investigated in terms of spectral contents, horizontal-to-vertical (H/V) spectral ratios and quality factors using regional waveforms for the 2009 North Korean underground nuclear explosion test that was well recorded by stations in the southern Korean Peninsula. Regional waveforms and spectral amplitudes vary significantly by path. Spectral contents of regional phases are different among stations in common great-circle directions. All regional phases modulate highly in continental margins. Path-dependent seismic attenuation is strong in low frequencies (≤. 3. Hz), and weak in high frequencies (>. 3. Hz). Continental margins cause directional energy partition of regional waves depending on the path. Regional waves attenuate highly in passage across continental margin, and then regrow on continental paths. The growth rate is stronger than inherent attenuation rate, causing seismic amplification. The shapes of H/V ratios are similar among various regional phases at common stations. On the other hand, the H/V ratios for common phases vary by station in the same azimuths. Characteristic differences in H/V ratios between two horizontal components suggest directional partition of seismic energy by crustal structures in the paths. © 2013 Elsevier B.V.

Jung K.S.,Yonsei University
The Korean journal of hepatology | Year: 2012

Reports of metastatic hepatocellular carcinoma (HCC) without a primary liver tumor are rare. Here we present a case of isolated HCC that had metastasized to the pelvic bone without a primary focus. A 73-year-old man presented with severe back and right-leg pain. Radiological examinations, including computed tomography (CT) and magnetic resonance imaging (MRI), revealed a huge mass on the pelvic bone (13×10 cm). He underwent an incisional biopsy, and the results of the subsequent histological examination were consistent with metastatic hepatocellular carcinoma. The tumor cells were positive for cytokeratin (AE1/AE3), hepatocyte paraffin 1, and glypican-3, and negative for CD56, chromogranin A, and synaptophysin on immunohistochemical staining. Examination of the liver by CT, MRI, positron-emission tomography scan, and angiography produced no evidence of a primary tumor. Radiotherapy and transarterial chemoembolization were performed on the pelvic bone, followed by systemic chemotherapy. These combination treatments resulted in tumor regression with necrotic changes. However, multiple lung metastases developed 1 year after the treatment, and the patient was treated with additional systemic chemotherapy.

Kim B.G.,Pusan National University | Choi H.J.,Yonsei University
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

We study α, β, and γ graphyne, a class of graphene allotropes with carbon triple bonds, using a first-principles density-functional method and tight-binding calculation. We find that graphyne has versatile Dirac cones and it is due to remarkable roles of the carbon triple bonds in electronic and atomic structures. The carbon triple bonds modulate effective hopping matrix elements and reverse their signs, resulting in Dirac cones with reversed chirality in α graphyne, momentum shift of the Dirac point in β graphyne, and switch of the energy gap in γ graphyne. Furthermore, the triple bonds provide chemisorption sites of adatoms which can break sublattice symmetry while preserving planar sp2-bonding networks. These features of graphyne open new possibilities for electronic applications of carbon-based two-dimensional materials and derived nanostructures. © 2012 American Physical Society.

Coloanal anastomosis (CAA)/intersphincteric resection (ISR) is a promising method of sphincter-preserving surgery for very low rectal cancer. Recently, a robotic system has been attempted in CAA/ISR. By means of a robotic system, an excellent stereoscopic view may be obtained with high illumination, and adequate traction and countertraction can be easily performed in a narrow pelvis using the Endowrist function. During robotic CAA/ISR, although the robotic system is necessary to perform pelvic dissection that comes before the perianal approach, the huge robotic arms located in the low abdominal region could interfere with comfortable perianal dissection for the surgeon. Therefore, the robotic system has to be withdrawn and then set up again above the patient's abdomen, which is time-consuming. Moreover, this process also makes it difficult to maintain the aseptic circumstance of the robotic system. To address this problem, it is necessary to change the sequence of the procedure. Patients with low rectal adenocarcinoma located within 6 cm above the anal verge were recruited and underwent robotic CAA/ISR. We performed the perianal approach first before docking the robotic system. In the transanal approach, manual dissection started at the level of the dentate line (for cases of CAA) or intersphincteric groove (for cases of ISR). The mucosa was stripped from the starting point to just above the levators. Robotic dissection was followed while maintaining pneumoperitoneum via packed gauzes in the anus. The surgical principles included high ligation of inferior mesenteric vessels and total mesorectal excision. Splenic flexure mobilization was selectively performed when the end of the remaining sigmoid colon could not reach the anal canal after the routine mobilization of the left colon side. After completion of total mesorectal excision, further dissection continued to the pelvic floor (Fig. 1). The puborectalis muscle sling was laterally exposed, and the anococcygeal ligament was noted on the posterior side of the anal canal. Intersphincteric dissection through the puborectalis ended at the intra-anal canal. Finally, the dissection plane could meet the perianal dissection plane. At this point, we could identify the gauze, which was packed via the perianal approach before beginning robotic dissection. The muscular rectal wall was divided by a cautery at the level of the puborectalis muscle by robotic arms. While performing the CAA/ISR, secure and meticulous dissection through the pelvic floor is important for oncological safety, which could be easily performed with the aid of robotic ergonomic Endowrist function and a magnified three-dimensional view even in a narrow pelvic cavity. Specimen extraction was done through the anus or additional minilaparotomy skin incision. In some cases, a planned ileostomy site was used as the minilaparotomy incision. For patients with bulky and heavy mesorectum, it is difficult and even dangerous to extract the specimen via the anus, which could induce traction injuries to the marginal vessels. Hand-sewn coloanal anastomosis was performed after removing the robotic cart from the operation field. The entire operative procedure is shown in the video. Early surgical outcomes, morbidity, and short-term follow-up data were extracted from a prospectively collected database. Robotic CAA/ISR for low rectal cancer was performed on 47 patients between August 2007 and December 2010. Forty-one patients underwent robotic CAA, and six patients underwent robotic ISR. There were 28 male and 19 female patients. The median age was 58 (range 32-86) years. The median body mass index was 23.3 (range 14.6-28.0) kg/m(2). Five patients (10.6%) had a history of abdominal surgery. According to American Society of Anesthesiology disease classification, 35 patients (74.5%) were class I, and 12 (25.5%) patients class II. The median distance between adenocarcinoma and the anal verge was 4 (range 1-6) cm. Preoperative chemoradiotherapy was provided to 19 patients (40.4%). There was no conversion to laparoscopic or open procedure. Operation time for robotic CAA/ISR was 360.9 ± 128.5 (mean ± standard deviation) min. For specimen retrieval, transanal extraction was performed in 23 cases (49%) and minilaparotomy was created for 24 cases (51%), including three cases of planned ileostomy site. Protective ileostomy was performed for 37 patients (78.7%). Blood loss was 158.0 ± 236.5 ml.

The purpose of this study was to observe the pharmacokinetic behavior of newly synthesized biocompatible polymers based on polyhydroxyethylaspartamide (PHEA) to be used to coat an iron oxide core to make superparamagnetic iron oxide nanoparticles (SPION). The isotopes [(14)C] and [(59)Fe] were used to label the polymer backbone (CLS) and iron oxide core (FLS), respectively. In addition, unradiolabeled cold superparamagnetic iron oxide nanoparticles (SPION/ULS) were synthesized to characterize particle size by dynamic light scattering, morphology by transmission electron microscopy, and in vivo magnetic resonance imaging (MRI). CLS and FLS were used separately to investigate the behavior of both the synthesized polymer and [Fe] in Sprague Dawley (SD) rats, respectively. Because radioactivity of the isotopes was different by β for CLS and γ for FLS, synthesis of the samples had to be separately prepared. The mean particle size of the ULS was 66.1 nm, and the biodistribution of CLS concentrations in various organs, in rank order of magnitude, was liver > kidney > small intestine > other. The biodistribution of FLS concentrations was liver > spleen > lung > other. These rank orders show that synthesized SPION mainly accumulates in the liver. The differences in the distribution were caused by the SPION metabolism. Radiolabeled polymer was metabolized by the kidney and excreted mainly in the urine; [(59)Fe] was recycled for erythrocyte production in the spleen and excreted mainly in the feces. The MR image of the liver after intravenous injection demonstrated that [Fe] effectively accumulated in the liver and exhibited high-contrast enhancement on T2-weighted images. This newly synthesized, polymer-coated SPION appears to be a promising candidate for use as a liver-targeted, biocompatible iron oxide MR imaging agent.

Park H.,Yonsei University
Gut and Liver | Year: 2014

Eosinophilic esophagitis (EoE) is a chronic, immune/antigenmediated esophageal disease affecting both children and adults. The condition is characterized by an eosinophilic infiltration of the esophageal epithelium. Symptoms of esophageal dysfunction include dysphagia, food impaction and symptoms mimicking gastroesophageal reflux disease. Endoscopic examination typically reveals mucosal fragility, ring or corrugated mucosa, longitudinal furrows, whitish plaques or a small caliber esophagus. Histologic findings of >15 eosinophils per high-power field is the diagnostic hallmark of EoE. An elimination diet, topical corticosteroids or endoscopic dilation for fibrostenotic disease serve as effective therapeutic option.

Park M.S.,Yonsei University
Clinical and molecular hepatology | Year: 2013

The incidence of multidrug-resistant (MDR) chronic hepatitis B (CHB) during sequential lamivudine (LAM) and adefovir dipivoxil (ADV) treatment is increasing. We investigated the antiviral efficacies of various rescue regimens in patients who failed sequential LAM-ADV treatment. Forty-eight patients (83.3% of whom were HBeAg-positive) who failed sequential LAM-ADV treatment were treated with one of the following regimens: entecavir (ETV) (1 mg) monotherapy (n=16), LAM+ADV combination therapy (n=20), or ETV (1 mg)+ADV combination therapy (n=12). All patients had confirmed genotypic resistance to both LAM and ADV and were evaluated every 12 weeks. The baseline characteristics and treatment duration did not differ significantly among the study groups. During the treatment period (median duration: 100 weeks), the decline of serum HBV DNA from baseline tended to be greatest in the ETV+ADV group at all-time points (week 48: -2.55 log(10) IU/mL, week 96: -4.27 log(10) IU/mL), but the difference was not statistically significant. The ETV+ADV group also tended to have higher virologic response rates at 96 weeks compared to the ETV monotherapy or LAM+ADV groups (40.0% vs. 20.0% or 20.0%, P=0.656), and less virologic breakthrough was observed compared to the ETV monotherapy or LAM+ADV groups (8.3% vs. 37.5% or 30.0%; P=0.219), but again, the differences were not statistically significant. HBeAg loss occurred in one patient in the ETV+ADV group, in two in the ETV monotherapy group, and in none of the LAM+ADV group. The safety profiles were similar in each arm. There was a nonsignificant tendency toward better antiviral efficacy with ETV+ADV combination therapy compared to LAM+ADV combination therapy and ETV monotherapy for MDR CHB in Korea, where tenofovir is not yet available.

Baek J.,Yonsei University
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2010

In this Letter, we propose an adaptive fuzzy bilinear feedback control (FBFC) design for synchronization of Takagi-Sugeno (TS) fuzzy bilinear generalized Lorenz system (FBGLS) with uncertain parameters. The generalized Lorenz system (GLS) can be described to TS FBGLS. We design an adaptive synchronization scheme of the response system based on TS FBGLS, feedback control scheme and Lyapunov theory. Lyapunov theory is employed to guarantee the stability of error dynamic system and to derive the adaptive laws to estimate unknown parameters. Numerical example is given to demonstrate the validity of our proposed adaptive FBFC approach with comparative results for synchronization. © 2010 Elsevier B.V. All rights reserved.

Dib C.,Federico Santa Maria Technical University | Kim C.S.,Yonsei University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

We review the detection of the ΔL=2 semileptonic meson decays of the form M+→M′-++ that we studied in a previous work, mediated by a Majorana neutrino with a mass in the range between the masses of the initial and final mesons. For such a range of masses, the Majorana neutrino will go on its mass shell, and the two charged leptons will appear at displaced vertices or, if the lifetime is long enough, most secondary vertices will fall outside the detector. We study the consequences of this effect on the experimental searches and limits that can be extracted. © 2014 American Physical Society.

Shin S.,Yonsei University
Environmental Politics | Year: 2010

The clean development mechanism (CDM) has been widely considered a win-win scenario from which both developed and developing countries could benefit. However, in spite of its growing popularity and the increasing number of issued certified emission reductions, CDM has not been effective in reducing greenhouse gas emissions and helping developing countries to achieve sustainable development. By considering the case of China, it appears that, although there are fundamental weaknesses in the institutional design of CDM, it is the host country's domestic conditions that have the biggest impact on CDM's effectiveness. The Chinese government has implemented its own rules and regulations, and addressed the problems in CDM processes in ways that maximise its national interest, whilst preventing non-governmental actors from participating in the policy process. The combination of governmental intervention and weak non-governmental participation has shaped the outcomes of CDM projects in China. The balance between these two domestic factors may be critical in influencing the effectiveness of CDM governance. © 2010 Taylor & Francis.

Kang S.-H.,Yonsei University | Chow S.-C.,Duke University
Statistics in Medicine | Year: 2013

In this paper, we propose a new three-arm parallel design to investigate biosimilarity between a biosimilar product and an innovator biological product by using relative distance based on the absolute mean differences. In the proposed design, one arm is for the biosimilar product and the other two arms are for the innovator biological product. The distance between the biosimilar product and the innovator biological product is defined by the absolute mean different between two products. Similarly, the distance between the innovator biological products from two difference batches is defined. The relative distance is defined as the ratio of the two distances whose denominator is the distance between the innovator biological products from two different batches. In the proposed design, if the relative distance is less than a prespecified margin, we claim that the two products are claimed to be biosimilar. The statistical test based on the ratio estimator and the linearization method are developed to assess biosimilarity. The power functions of two tests are derived in large sample and compared numerically. Because the statistical test based on the ratio estimator is more powerful than the linearization method, we recommend the statistical test based on the ratio estimator. © 2012 John Wiley & Sons, Ltd.

Baek Y.M.,Yonsei University
Computers in Human Behavior | Year: 2014

This study investigates why ordinary online users highly concerned about the misuse of personal information do not adopt privacy-protective behaviors, or even engage in risky behaviors, on the Internet. Given that people have few chances to directly experience privacy infringement and tend to be unfamiliar with technical terms, their opinions as reflected in conventional polls tend to be instantaneous reactions to survey questionnaires, lacking thoughtfulness. By adopting a counterargument experimental technique, this study produced three important findings: (1) people's opinions about online privacy are swayed after being presented with a message containing a counterargument; (2) this persuasion effect is pronounced among people with a low level of online knowledge or who assess the presented message's argument as strong; and (3) the privacy paradox is found in conventional polls but disappears in counterargument conditions. These findings imply that opinions concerning online privacy should not be estimated through conventional polling. Rather, alternative polls (e.g., deliberative polls) should be adopted for online privacy policy-making. © 2014 Elsevier Ltd. All rights reserved.

Yoo G.,Kyung Hee University | Kang H.,Yonsei University
Journal of Environmental Quality | Year: 2012

Biochar application to soil has drawn much attention as a strategy to sequester atmospheric carbon in soil ecosystems. The applicability of this strategy as a climate change mitigation option is limited by our understanding of the mechanisms responsible for the observed changes in greenhouse gas emissions from soils, microbial responses, and soil fertility changes. We conducted an 8-wk laboratory incubation using soils from PASTURE (silt loam) and RICE PADDY (silt loam) sites with and without two types of biochar (biochar from swine manure [CHAR-M] and from barley stover [CHAR-B]). Responses to addition of the diff erent biochars varied with the soil source. Addition of CHAR-B did not change CO2 and CH4 evolution from the PASTURE or the RICE PADDY soils, but there was a decrease in N2O emissions from the PASTURE soil. Th e eff ects of CHAR-M addition on greenhouse gas emissions were diff erent for the soils. Th e most substantial change was an increase in N2O emissions from the RICE PADDY soil. Th is result was attributed to a combination of abundant denitrifi ers in this soil and increased net nitrogen mineralization. Soil phosphatase and N-acetylglucosaminidase activity in the CHAR-B-treated soils was enhanced compared with the controls for both soils. Fungal biomass was higher in the CHAR-B-treated RICE PADDY soil. From our results, we suggest CHAR-B to be an appropriate amendment for the PASTURE and RICE PADDY soils because it provides increased nitrogen availability and microbial activity with no net increase in greenhouse gas emissions. Application of CHAR-M to RICE PADDY soils could result in excess nitrogen availability, which may increase N2O emissions and possible NO3 leaching problems. Th us, this study confi rms that the ability of environmentally sound biochar additions to sequester carbon in soils depends on the characteristics of the receiving soil as well as the nature of the biochar. © 2012 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.

Ozaki S.,Yonsei University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

We derive the analytic expression for the one-loop SU(Nc) QCD effective potential including Nf flavor quarks which nonlinearly interact with the chromomagnetic background field and the external U(1)em magnetic field. After the renormalization of couplings and fields, we obtain the correct one-loop β functions of both QCD and QED, and the resulting effective potential satisfies the renormalization group equation. We investigate the effect of the magnetic field on the QCD vacuum by using the effective potential, in particular for the color SU(3) case with the three flavors (u,d,s). Our result shows that the chromomagnetic field prefers to be parallel to the external magnetic field. Furthermore, quark loop contributions to the effective potential with the magnetic field enhance gluonic contributions, and then the chromomagnetic condensate increases with an increasing magnetic field. This result supports the recent observed gluonic magnetic catalysis at zero-temperature in lattice QCD. © 2014 American Physical Society.

A 5-year-old girl was diagnosed with neurofibromatosis type 2 (NF-2) due to multiple neurofibromas, cafe-au-lait spots, and schwannomas of the brain. During ophthalmologic evaluation, a posterior subcapsular cataract and a gray-green colored subretinal lesion were found in right eye. Fluorescein angiography (FA) revealed a combined hamartoma of the retina and retinal pigment epithelium (CHRRPE). At age 9, she underwent cataract surgery. At this time FA and spectral-domain optical coherence tomography (SD-OCT) were taken. The SD-OCT showed an elevated hyperreflective mass in the retina with prominent attenuation of the inner and outer retina, but minimal attenuation in the photoreceptor layers. The underlying retina appeared to be disorganized and thick (791 μm). This is the first case report of SD-OCT imaging of a CHRRPE associated with NF-2 in a pediatric patient. By using SD-OCT in this patient, we could obtain detailed tumor characteristics, and SD-OCT may be helpful in the diagnosis and management of CHRRPE.

Choi J.Y.,Inje University | Oh K.J.,Yonsei University
Child Abuse and Neglect | Year: 2014

The purpose of the present study was to identify the mediating effects of emotion regulation on the association between cumulative childhood trauma and behavior problems in sexually abused children in Korea, using structural equation modeling (SEM). Data were collected on 171 children (ages 6-13 years) referred to a public counseling center for sexual abuse in Seoul, Korea. Cumulative childhood traumas were defined on the basis of number of traumas (physical abuse, witnessing domestic violence, neglect, traumatic separation from parent, and sexual abuse) and the severity and duration of traumas. Children were evaluated by their parents on emotion regulation using the Emotion Regulation Checklist and internalizing and externalizing behavior problems using the Korean-Child Behavior Checklist. SEM analyses confirmed the complete mediation model, in which emotion dysregulation fully mediates the relationship between cumulative childhood traumas and internalizing/externalizing behavior problems. These findings indicate that emotion regulation is an important mechanism that can explain the negative effects of cumulative childhood traumas and that there is a need to focus on emotion regulation in sexually abused children exposed to cumulative trauma. © 2013 Elsevier Ltd.

Choi H.S.,Yonsei University | Meier D.,Thunen Institute of Wood Research
Journal of Analytical and Applied Pyrolysis | Year: 2013

Screening of pyrolysis reactions has been carried out with Kraft lignin and various catalysts applying the TI-mini fast pyrolyzer. Zeolite HZSM-5, FCC and Olivine in a small fixed bed were used as catalyst to investigate their influences on the pyrolysis reaction. The characteristics of catalytic pyrolysis reactions and final products were studied by varying reaction temperature and catalyst type. The TI-mini fast pyrolyzer is especially suitable to obtain quick mass balances of main products such as char, non-condensable gases and biocrude-oil. Their yields were evaluated and the collected biocrude-oil was further analyzed using GC-MS/FID. Depending on the various catalysts as well as different pyrolysis temperatures, the overall distribution of the three main product categories and the portions of certain chemical compounds were increased or decreased. To scrutinize the catalytic effect and to highlight the severity of lignin degradation, size exclusion chromatography (SEC) was performed from extracts of the solid residue. © 2013 Elsevier B.V.

Jin B.,Yonsei University
Computers in Human Behavior | Year: 2013

This study examined the relationship between loneliness and various aspects of Facebook use including use activity, self-disclosure, attitudes, and satisfaction. Data were collected through an online survey among adult Facebook users (N = 536). Results revealed that loneliness was associated with a fewer number of Facebook friends and a less overlapping between Facebook and offline friends. Loneliness was inversely related to communicating activities but not significantly to presenting activities. Also, lonely people tended to engage in positive self-disclosure less but negative self-disclosure more. Although lonely people viewed Facebook as more useful for self-disclosure and social connection, their satisfaction of Facebook use was lower than their counterparts. © 2013 Elsevier B.V.

Moon B.S.,Yonsei University
Journal of the National Cancer Institute | Year: 2014

Adenomatous polyposis coli (APC) loss-of-function mutations and K-Ras gain-of-function mutations are common abnormalities that occur during the initiation and intermediate adenoma stages of colorectal tumorigenesis, respectively. However, little is known about the role these mutations play in cancer stem cells (CSCs) associated with colorectal cancer (CRC) tumorigenesis. We analyzed tissue from CRC patients (n = 49) to determine whether K-Ras mutations contributed to CSC activation during colorectal tumorigenesis. DLD-1-K-Ras-WT and DLD-1-K-Ras-MT cells were cultured and evaluated for their ability to differentiate, form spheroids in vitro, and form tumors in vivo. Interaction between APC and K-Ras mutations in colorectal tumorigenesis was evaluated using APC (Min/+)/K-Ras (LA2) mice and DLD-1-K-Ras-WT and DLD-1-K-Ras-MT cell xenografts. (n = 4) Group differences were determined by Student t test. All statistical tests were two-sided. The sphere-forming capability of DLD-1-K-Ras-MT cells was statistically significantly higher than that of DLD-1-K-Ras-WT cells (DLD-1-K-Ras-MT mean = 86.661 pixel, 95% confidence interval [CI] = 81.701 to 91.621 pixel; DLD-1-K-Ras-WT mean = 42.367 pixel, 95% CI = 36.467 to 48.267 pixel; P = .003). Moreover, both the size and weight of tumors from DLD-1-K-Ras-MT xenografts were markedly increased compared with tumors from DLD-1-K-Ras-WT cells. Expression of the CSC markers CD44, CD133, and CD166 was induced in intestinal tumors from APC (Min/+)/K-Ras (LA2)mice, but not K-Ras (LA2) mice, indicating that APC mutation is required for CSC activation by oncogenic K-Ras mutation. K-Ras mutation activates CSCs, contributing to colorectal tumorigenesis and metastasis in CRC cells harboring APC mutations. Initial activation of β-catenin by APC loss and further enhancement through K-Ras mutation induces CD44, CD133, and CD166 expression.

The objective of this study was to analyze orthotropic bone formation and remodeling of three different dental implant surfaces with and without recombinant human bone morphogenetic protein 2 derived from Escherichia coli (ErhBMP-2) in a rabbit model. Resorbable blasting media (RBM); sandblasted, large-grit, acid-etched (SLA); and magnesium-incorporated oxidized (MgO) implant surfaces were coated with ErhBMP-2 (1.5 mg/mL). The implants were placed into the proximal tibia in six New Zealand White rabbits. Each rabbit received six different implants (three coated with ErhBMP-2 in one tibia and three uncoated implants in the other tibia), and the sites were closed, submerging the implants. The animals received alizarin (at 2 weeks), calcein (at 4 weeks), and tetracycline (at 6 weeks) fluorescent bone markers, and were euthanized at 8 weeks for histomorphometric analysis. The amount of ErhBMP-2 coating was 9.6 ± 0.4 μg per MgO implant, 14.5 ± 0.6 μg per RBM implant, and 29.9 ± 3.8 μg per SLA implant. Clinical healing was uneventful. Mean bone-to-implant contact (± standard deviation) for the ErhBMP-2/RBM (35.4% ± 5.1%) and ErhBMP-2/MgO (33.4 % ± 13.2%) implants was significantly greater compared with RBM (23.6% ± 6.2%) and MgO (24.9% ± 2.7%) implants (P < .05). Considering the mean bone-to-implant contact in cortical bone, ErhBMP-2/SLA implants (32.9% ± 7.8%) showed lower bone-to-implant contact in cortical bone than all other implant variations (range, 39.9% ± 18.1% to 51.3% ± 9.2%; P < .05). There were no remarkable differences in new bone area, with minor differences between implants. Within the limits of study, it was found that the absorbed ErhBMP-2 dose varied with implant surface characteristics, influencing local bone formation and remodeling.

Kim G.,Yonsei University
Library and Information Science Research | Year: 2011

A selective review of valuation studies evaluated various characteristics, including methods, subjects, and reporting media, in order to identify theoretical frameworks to aid in understanding trends in library services. Two distinct frameworks were identified: the marketing framework with revealed preference method, and the evaluation framework with contingent valuation method. The marketing framework studies aim to promote communication between libraries and their stakeholders to affect the future state of a library, whereas the evaluation framework studies aim to describe the current state of a library and predict its future state. This two-framework approach supports further theoretical and practical exploration of library valuation and library services. © 2011 Elsevier Inc.

Bae H.W.,Yonsei University
Optometry and Vision Science | Year: 2014

PURPOSE: To evaluate the clinical performance of visual field (VF) tests and optical coherence tomography (OCT) in diagnosing glaucoma.METHODS: One hundred sets of disc photographs, red-free fundus photographs, VF tests, and OCT images were presented progressively to seven ophthalmologists. Each set was provided in three steps: (1) the disc and red-free fundus photographs were shown first; (2) then, VF tests were also provided; and (3) finally, the OCT results were provided. The same process was repeated on another day. Kappa statistics were used to assess the intraobserver and interobserver agreement, as well as the agreement with the reference standard.RESULTS: The intraobserver agreement was almost perfect in this study and did not change markedly with the addition of diagnostic tools. The interobserver agreement increased from 0.54 to 0.61 when VF was added and increased slightly to 0.63 with OCT. The agreement with the reference standard also increased significantly from 0.48 to 0.61 after adding VF and increased slightly with additional OCT.CONCLUSIONS: An optic disc evaluation and VF test are sufficient to diagnose glaucoma in most cases. However, OCT can play an important role in detecting glaucoma in cases in which it cannot be identified by optic disc examination and VF. © 2014 American Academy of Optometry

Doppler ultrasonography (US) has an advantage of being non-invasive; therefore, several attempts have been made to investigate the haemodynamic alterations in cirrhosis and the response to medical treatment of portal hypertension. Doppler indices, which have been commonly used for the evaluation of portal hypertension, include the measurement of portal and splenic venous blood velocity and flows, and the resistive and pulsatility index at hepatic, splenic, renal, superior mesenteric artery. Although many positive evidences have been suggested, its clinical usefulness in portal hypertension remains unsettled because of being plagued by lack of reproducibility and accuracy characterized by intra- and interobserver variation. However, recently, Doppler's usefulness in assessment of severity of portal hypertension in terms of reproducibility, technical ease and accuracy and response to drugs that reduce the portal pressure has been proposed. In addition, because most of the patients with cirrhosis and portal hypertension have intrahepatic shunts, they show a decrease in intrahepatic circulatory time (IHCT). Doppler US using microbubble contrast agents allows measurement of IHCT. Therefore, application of contrast-enhanced Doppler US can be prospective for the assessment of the severity of portal hypertension. Several reports have demonstrated that colour Doppler endoscopic US enable haemodynamic study to assess the portal hypertension and has a role of guidance to measure the imaging-based variceal pressure. We have reviewed briefly the clinical usefulness of Doppler US in assessing the severity of portal hypertension and its response to treatment. © 2010 John Wiley & Sons A/S.

Mok Y.,Yonsei University
Nephrology, dialysis, transplantation : official publication of the European Dialysis and Transplant Association - European Renal Association | Year: 2012

Both serum uric acid (SUA) and chronic kidney disease (CKD) are associated with the risk of cardiovascular disease; however, it is unclear whether SUA independently increases the risk of CKD based on longitudinal data. To investigate the relationship between SUA levels and CKD development, we initiated a 10.2-year prospective cohort study. Data from 14 939 Koreans, 20-84 years of age, who completed a questionnaire and medical examination at the Severance Health Promotion Center were evaluated. The outcome of interest, CKD, was defined as an estimated glomerular filtration rate (GFR) of <60 mL/min/1.73m(2) via the simplified Modification of Diet in Renal Disease equation. A multivariate Cox proportional hazard model, controlling for age, life style and other cardiovascular risk factors, showed an increased risk of developing CKD for men [hazard ratio (HR) 2.1; 95% confidence interval (CI) 1.6-2.9] and women (HR = 1.3; 95% CI = 1.0-1.8) in the highest quartiles of SUA compared to their counterparts in the lowest quartiles. The relationship between SUA and CKD was linear and stepwise in men. The HRs for renal function Grade 2 (75-89.9 mL/min/1.73m(2)), Grade 3 (60-74.9 mL/min/1.73m(2)) and Grade 4 (<60 mL/min/1.73m(2)) increased with an increase in SUA quartiles as compared to the baseline GFR group (Grade 1, ≥90 mL/min/1.73m(2)). Higher SUA levels increased the risk of CKD, suggesting that at least part of the reported association between SUA and cardiovascular disease may be connected to CKD.

Yim S.M.,Yonsei University
Digestive diseases and sciences | Year: 2014

Mucosal healing (MH) has emerged as a therapeutic goal in the treatment of inflammatory bowel disease; however, little is known about the impact of MH on the prognosis of intestinal Behçet's disease (BD). We investigated whether MH could predict the prognosis of intestinal BD. We retrospectively reviewed the medical records of 80 patients with intestinal BD who underwent colonoscopy within 3 months after clinical remission. The clinical recurrence rate according to the presence or absence of MH was evaluated using the Kaplan-Meier method and the log-rank test. In order to evaluate MH as an independent prognostic factor, a multivariate analysis using Cox proportional hazards regression model was performed including other potential factors for the relapse of intestinal BD. The number of patients with active ulcers at the time of clinical remission was 57 (71.3%), while 23 patients (28.7%) were experiencing MH. In the active ulcer group, 39 patients (68.4%) experienced recurrence during the follow-up period, whereas 7 patients (30.4%) recurred in the MH group. The cumulative recurrence rate was significantly higher in the active ulcer group than in the MH group (P < 0.001). A multivariate analysis identified active ulcers at the time of clinical remission as an independent predictive factor for relapse. Our study demonstrates that MH is an independent factor predictive of long-term prognosis of intestinal BD. MH might be the ultimate therapeutic goal in the treatment of intestinal BD.

Kim M.Y.,Yonsei University
The Korean journal of hepatology | Year: 2010

The blunted ventricular systolic and diastolic contractile responses to physical and pharmacological stress in cirrhosis are termed cirrhotic cardiomyopathy (CCM). CCM has been known to involve multiple defects in the β-adrenergic signaling pathway. The aim of this study was to determine whether cirrhotic patients have blunted cardiac responses to catecholamine stimulation through dobutamine stress echocardiography (DSE). Seventy-one cirrhotic patients with normal left ventricular (LV) chamber size and ejection fraction were enrolled. The LV systolic and diastolic functions were evaluated by two-dimensional and Doppler echocardiography at rest and during peak dobutamine infusion (40 μg/kg/min). An abnormal response was defined as a decrease of less than 10% in LV end-diastolic volume, a decrease of less than 20% in end-systolic volume, and an increase of less than 10% in LV ejection fraction (EF) at peak dobutamine infusion, based on previously used criteria. The early/late diastolic flow (E/A) ratio and diastolic parameters were also measured. A blunted LV response to dobutamine was observed in 18 of 71 cirrhotic patients (25.4%). The baseline EF was significantly higher in 18 patients with a blunted DSE response than that of those with a normal DSE response (P<0.05). The baseline and peak E/A ratios, which are common diastolic dysfunction markers, were higher in the cirrhosis group than in the control group (P<0.001). No adverse events associated with DSE were observed. Blunted cardiac responses to dobutamine stimulation, which are implicated in defects in the β-adrenergic signaling pathway, might contribute to the pathogenesis of CCM in patients with cirrhosis.

Lee S.-H.,Yonsei University
Journal of Pragmatics | Year: 2011

In a set of calls to an airline service in which agents ask for customers' identifying information, some customers respond by providing different, unrequested information. This paper examines these non-direct, nonconforming responses and shows that those customers anticipate hierarchical institution-specific stages in the activity and respond to the higher-level purpose for which the question was produced. Customers thereby promote the progress of the larger activity in an institutionally relevant way. This suggests that participants can depart from type-conformity with an orientation to activity progressivity. © 2010 Elsevier B.V.

Nam E.J.,Yonsei University
International journal of gynecological cancer : official journal of the International Gynecological Cancer Society | Year: 2010

The purpose of this study was to compare surgical outcomes of robotic radical hysterectomy (RRH) using 3 robotic arms with those of abdominal radical hysterectomy (ARH) in the treatment of early-stage cervical cancer. Thirty-two patients with stage IA2-IIB cervical carcinoma according to the International Federation of Gynecology and Obstetrics underwent RRH between June 2006 and February 2009. Patient outcomes were compared with those of a historic cohort of 32 patients who underwent ARH, who were matched for age, stage according to the International Federation of Gynecology and Obstetrics, and type of radical surgery. All RRHs were completed robotically with no conversions to laparotomy. Robotic radical hysterectomy showed favorable outcomes over ARH in terms of the mean length of hospital stay (11.6 vs 16.9 days, P < 0.001) and the mean estimated blood loss (220 vs 531 mL, P = 0.002). The mean operating time and the number of lymph node retrievals were comparable. There were no significant differences in the incidence of postoperative complications between the 2 groups. The mean follow-up time was 15.3 months, and 2 patients in the RRH group had recurrences. Robotic radical hysterectomy and pelvic lymphadenectomy using 3 robotic arms is feasible and preferable over ARH for the treatment of cervical cancer patients. Prospective randomized trials should be completed to confirm the potential benefits associated with RRH.

Lee I.,Yonsei University | Lee I.,University of Texas at Austin | Ambaru B.,Carnegie Institution for Science | Thakkar P.,Carnegie Institution for Science | And 2 more authors.
Nature Biotechnology | Year: 2010

We introduce a rational approach for associating genes with plant traits by combined use of a genome-scale functional network and targeted reverse genetic screening. We present a probabilistic network (AraNet) of functional associations among 19,647 (73%) genes of the reference flowering plant Arabidopsis thaliana. AraNet associations are predictive for diverse biological pathways, and outperform predictions derived only from literature-based protein interactions, achieving 21% precision for 55% of genes. AraNet prioritizes genes for limited-scale functional screening, resulting in a hit-rate tenfold greater than screens of random insertional mutants, when applied to early seedling development as a test case. By interrogating network neighborhoods, we identify AT1G80710 (now DROUGHT SENSITIVE 1; DRS1) and AT3G05090 (now LATERAL ROOT STIMULATOR 1; LRS1) as regulators of drought sensitivity and lateral root development, respectively. AraNet (http://www.functionalnet.org/aranet/) provides a resource for plant gene function identification and genetic dissection of plant traits.

Lee D.J.,Yonsei University
The Korean journal of gastroenterology = Taehan Sohwagi Hakhoe chi | Year: 2012

Metformin is known to lower the risk of cancer and cancer mortality. However, the effect of metformin in stage IV colorectal cancer (CRC) patients with diabetes mellitus (DM) remains unknown. The aim of this study was to evaluate the effect of metformin on tumor response and survival in stage IV CRC patients with DM. We identified 106 patients who were diagnosed with both stage IV CRC and DM (81 patients who underwent palliative chemotherapy and 25 patients who underwent curative resection). Retrospective data of each patient's clinical characteristics, tumor response, and survival rate were compared between two groups of patients who either were or were not administered metformin. For the palliative chemotherapy group, tumor response, change in target lesion size, progression free survival rate, and overall survival rate were not significantly different between the metformin group and the non-metformin group on univariate and multivariate analysis. For the curative resection patient group, metformin use was associated with increased disease free survival on univariate analysis (p=0.012) and multivariate analysis (hazard ratio, 0.024; 95% CI 0.001-0.435; p=0.010), but not with overall survival. Metformin use in stage IV CRC patients with diabetes was shown to be associated with a lower risk of tumor recurrence after curative resection.

Glassman M.,Ohio State University | Kang M.J.,Yonsei University
International Journal of Computer-Supported Collaborative Learning | Year: 2011

The emergence of Web 2.0 and some of its ascendant tools such as blogs and wikis have the potential to dramatically change education, both in how we conceptualize and operationalize processes and strategies. We argue in this paper that it is a change that has been over a century in coming. The promise of the Web 2. 0 is similar to ideas proposed by Pragmatists such as Charles Peirce and John Dewey. Peirce proposed the logic of abduction as critical for the types of unique/progressive thinking that leads to creative problem solving and/or discovery. While logic based in deduction offers outcomes with certainty, logic based in abduction offers potentially valuable insights. Dewey tried to implement progressive education in the classrooms. Dewey's ideas, while influential, were often misunderstood, or considered too idealistic and/or unworkable in the traditional classrooms. Logics based in abduction required that different major premises and hypotheses for problem solving be held simultaneously and over time. This type of scenario is often times difficult if not impossible in education based on direct interactions. Hypertext, especially as capture through emerging tools of Web 2.0, may offer the technologies that enable the type of information based networks within the education process that promote abduction and the democratic classroom as Dewey envisioned. © 2011 International Society of the Learning Sciences, Inc.; Springer Science + Business Media, LLC.

The aim of study was to determine the prevalence of metabolic syndrome (MetS) in people with type 2 diabetes mellitus (T2DM). National Cholesterol Education Program (NCEP) ATPIII Criteria, International Diabetes Federation and the World Health Organization (WHO) definitions were used in quantifying the metabolic syndrome and also the concordance between these three criteria's used for identifying metabolic syndrome. This cross-sectional study involved 700 type 2 diabetic subjects from the urban areas of Gwalior Chambal region (Central India). Subjects in the age group of 28- 87 yrs were included in the study. Type I diabetics, pregnant ladies and those with chronic viral and bacterial infections and serious metabolic disorders were excluded from the study. Fasting blood glucose, Blood lipids (T-cholesterol, triglyceride, HDL-cholesterol) were assessed and anthropometry blood pressure were measured from all the subjects. The Prevalence of metabolic syndrome was found to be 45.8%, 57.7% and 28% following NCEP-ATPIII Criteria, IDF and WHO definitions, respectively. Using all the three definitions the prevalence was higher in women in all age groups. ATP III and IDF criteria showed good agreement (k 0.68) compared to ATP III with WHO (k 0.54) and IDF with WHO (k 0.34) criteria. Highest prevalence was observed following IDF definition. A good agreement was observed between ATPIII and IDF criteria. Maximum prevalence of Metabolic syndrome was recorded when IDF criteria was followed. NCEP-ATPIII criteria for the diagnosis of MetS and this criterion reflected equal importance to the every variable and showed a good agreement between the different criteria used.

Cheon J.H.,Yonsei University
Journal of Gastroenterology and Hepatology (Australia) | Year: 2013

Inflammatory bowel disease (IBD) is a chronic relapsing intestinal inflammatory disorder with unidentified causes. Currently, studies indicate that IBD results from a complex interplay between various genetic and environmental factors that produce intestinal inflammation. However, these factors may differ for Asians and Caucasians. Thus, differences in epidemiology, genetic variants, and clinical phenotypes of IBD have been observed between the two populations. Understanding the discrepancies between data from populations with different genetic backgrounds and environmental factors may reveal fundamental aspects of IBD pathogenesis. Accordingly, this review will summarize the current knowledge of IBD genetics studied in Asian countries and compare it with that from Western countries, with special focus on innate bacterial sensing, autophagy, and the interleukin-23 receptor-T helper cell 17 pathway. The epigenetic nature of IBD pathogenesis as well as the pharmacogenetics related to the use of immunomodulators will also be briefly covered. © 2012 Journal of Gastroenterology and Hepatology Foundation and Wiley Publishing Asia Pty Ltd.

Ku N.-O.,University of Michigan | Ku N.-O.,Yonsei University | Toivola D.M.,Abo Akademi University | Strnad P.,University of Ulm | Omary M.B.,University of Michigan
Nature Cell Biology | Year: 2010

Keratins 8 and 18 (K8 and K18) are heteropolymeric intermediate filament phosphoglycoproteins of simple-type epithelia. Mutations in K8 and K18 predispose the affected individual to liver disease as they protect hepatocytes from apoptosis. K18 undergoes dynamic O-linked N-acetylglucosamine glycosylation at Ser 30, 31 and 49. We investigated the function of K18 glycosylation by generating mice that overexpress human K18 S30/31/49A substitution mutants that cannot be glycosylated (K18-Gly g-), and compared the susceptibility of these mice to injury with wild-type and other keratin-mutant mice. K18-Gly g- mice are more susceptible to liver and pancreatic injury and apoptosis induced by streptozotocin or to liver injury by combined N-acetyl-D-glucosaminidase inhibition and Fas administration. The enhanced apoptosis in the livers of mice that express K18-Gly- involves the inactivation of Akt1 and protein kinase Cø as a result of their site-specific hypophosphorylation. Akt1 binds to K8, which probably contributes to the reciprocal hyperglycosylation and hypophosphorylation of Akt1 that occurs on K18 hypoglycosylation, and leads to decreased Akt1 kinase activity. Therefore, K18 glycosylation provides a unique protective role in epithelial injury by promoting the phosphorylation and activation of cell-survival kinases.

Han S.H.,Yonsei University
Nephrology, dialysis, transplantation : official publication of the European Dialysis and Transplant Association - European Renal Association | Year: 2012

Many studies have suggested clinical benefits of icodextrin in peritoneal dialysis (PD) patients regarding fluid management, glycaemic control and metabolic improvement. However, reports on whether icodextrin can improve patient and technique survival is sparse. A total of 2163 patients from 54 centres in Korea who initiated PD from July 2003 to December 2006 were enrolled. Outcomes data were retrieved retrospectively from the Baxter Korea database. Among these patients, 641 patients who had been prescribed icodextrin for >50% of their PD duration were defined as the 'icodextrin' group and the remaining 1522 patients as the 'non-icodextrin' group. Propensity score matching yielded 640 matched pairs of patients. We compared all-cause mortality and technique failure rates between the two groups. There were no significant differences in age, gender, diabetes, cardiovascular comorbidity, socioeconomic status, biocompatible solution use in short dwells or centre experience between the two groups. Death occurred in 92 (14.4%) patients in the icodextrin group compared with 128 (20.0%) in the non-icodextrin group [hazard ratio (HR), 0.69; 95% confidence interval (CI), 0.53-0.90; P = 0.006]. In addition, icodextrin use was associated with a significantly lower risk of technique failure (HR, 0.60; 95% CI, 0.40-0.92; P = 0.018). The icodextrin group had fewer technique failures due to non-compliance compared with the non-icodextrin group whereas peritonitis- or ultrafiltration failure-related technique failure was not different between the two groups. This study further supports previous findings of long-term utilization of icodextrin solution improving patient and technique survival in PD patients. To confirm these results, a large randomized prospective study is warranted.

Kim C.-S.,Chungnam National University | Seong G.J.,Yonsei University | Lee N.-H.,Chungnam National University | Song K.-C.,Province of Chungcheongnamdo
Ophthalmology | Year: 2011

Purpose To assess the prevalence of primary open-angle glaucoma (POAG) in the Namil-myon area in central South Korea. Design A cross-sectional, epidemiologic study in a defined population. Participants Residents aged ≥40 years in Namil-myon, a rural agricultural area in central South Korea. Methods Each subject underwent a screening that consisted of an interview and ophthalmic examinations, including visual acuity measurement, autorefraction, anterior segment evaluation by optical biometry, slit-lamp examination, Goldmann applanation tonometry, binocular optic disc evaluation, fundus photography, pachymetry, gonioscopy, and screening visual field test using frequency doubling technology. Subjects with suspected glaucoma were referred for definitive examinations. Standard automated field tests and retinal nerve fiber layer analysis using optical coherence tomography (Stratus OCT) or scanning laser polarimetry (GDx VCC) were performed. A diagnosis of glaucoma was made based on the optic disc shape, retinal nerve fiber layer appearance, perimetric results, and other ocular findings. Main Outcome Measures Prevalence of POAG, mean intraocular pressure (IOP), and mean central corneal thickness (CCT). Results Of 1928 eligible residents in the area, 1532 (79.5%) participated in this study. The estimated prevalence of POAG in the population aged ≥40 years was 3.5% (95% confidence interval [CI], 2.7%-4.3%). The prevalence of POAG with an IOP of ≤21 mmHg was 2.7% (95% CI, 2.1%-3.3%), and the prevalence of POAG with an IOP of ≥22 mmHg was 0.8% (95% CI, 0.4%-1.2%). The mean IOP for POAG eyes (16.3±4.6 mmHg) was significantly higher than nonglaucomatous eyes (13.3±2.7 mmHg; P = .001). The mean CCT of POAG eyes with an IOP of ≤21 mmHg was 528±26 μm, and that of POAG eyes with an IOP ≥22 mmHg was 531±37 μm; these values were not significantly different from that of nonglaucomatous eyes (530±31 μm; P = .943 and .996, respectively). Conclusions The prevalences of POAG and POAG with an IOP ≤21 mmHg in the Namil-myon region of central South Korea were higher than that in most previous reports worldwide, but were similar to the reported rates in black and Japanese populations. The mean IOP of POAG eyes was higher than nonglaucomatous eyes, but the mean CCTs were not different. Financial Disclosure(s) The authors have no proprietary or commercial interest in any of the materials discussed in this article. © 2011 American Academy of Ophthalmology.

Whole-brain radiation therapy (WBRT), open resection, and stereotactic radiosurgery (SRS) are widely used for treatment of metastatic brain lesions, and many physicians recommend WBRT for multiple brain metastases. However, WBRT can be performed only once per patient, with rare exceptions. Some patients may require SRS for multiple metastatic brain lesions, particularly those patients harboring more than 10 lesions. In this paper, treatment results of SRS for brain metastasis were analyzed, and an attempt was made to determine whether SRS is effective, even in cases involving multiple metastatic brain lesions. The authors evaluated the cases of 323 patients who underwent SRS between October 2005 and October 2008 for the treatment of metastatic brain lesions. Treatment was performed using the Gamma Knife model C or Perfexion. The patients were divided into 4 groups according to the number of lesions visible on MR images: Group 1, 1-5 lesions; Group 2, 6-10 lesions: Group 3, 11-15 lesions; and Group 4, > 15 lesions. Patient survival and progression-free survival times, taking into account both local and distant tumor recurrences, were analyzed. The patients consisted of 172 men and 151 women with a mean age at SRS of 59 years (range 30-89 years). The overall median survival time after SRS was 10 months (range 8.7-11.4 months). The median survival time of each group was as follows: Group 1, 10 months; Group 2, 10 months; Group 3, 13 months; and Group 4, 8 months. There was no statistical difference between survival times after SRS (log-rank test, p = 0.554), although the probability of development of new lesions in the brain was greater in Group 4 (p = 0.014). Local tumor control rates were not statistically different among the groups (log-rank test, p = 0.989); however, remote disease progression was more frequent in Group 4 (log-rank test, p = 0.014). In this study, patients harboring more than 15 metastatic brain lesions were found to have faster development of new lesions in the brain. This may be due to the biological properties of the patients' primary lesions, for example, having a greater tendency to disseminate hematogenously, especially to the brain, or a higher probability of missed or invisible lesions (microscopic metastases) to treat on stereotactic MR images at the time of radiosurgery. However, the mean survival times after SRS were not statistically different between groups. According to the aforementioned results, SRS may be a good treatment option for local control of metastatic lesions and for improved survival in patients with multiple metastatic brain lesions, even those patients who harbor more than 15 metastatic brain lesions, who, after SRS, may have early and easily detectable new metastatic lesions.

Lee D.H.,Yonsei University
Proceedings of the American Control Conference | Year: 2013

This paper deals with the problem of estimating invariant subsets of the domain of attraction (DA) for continuous-time Takagi-Sugeno (T-S) fuzzy systems. By employing the fuzzy Lyapunov function, a new sufficient condition is formulated in the form of linear matrix inequalitys (LMI) or eigenvalue problems (EVPs). For better solutions, an iterative LMI algorithm is also provided. Finally, examples are given to demonstrate the effectiveness of the proposed approach in comparison with existing methods in the literature. © 2013 AACC American Automatic Control Council.

Kim D.H.,Yonsei University
Digestive diseases and sciences | Year: 2014

Little is known about the role of follow-up endoscopy in patients with inflammatory bowel disease (IBD). The present study aimed to evaluate whether repeated endoscopies would be beneficial in improving outcomes of patients with IBD. Patients who had been initially confirmed to have IBD at two tertiary hospitals in Korea were regularly followed and included in this study. The clinical impact as assessed by the presence or absence of a change in management after endoscopy and cumulative hospitalization rate was compared between two groups classified according to the presence or absence of indications. A total of 188 patients with IBD were enrolled [69 patients with Crohn's disease (CD) and 119 with ulcerative colitis (UC)]. Of these patients, 130 underwent follow-up endoscopy (48 with CD and 82 with UC). The rate of management change was significantly higher in the group with indications for follow-up endoscopy (p = 0.001 in CD and <0.001 in UC). The presence of any indications for follow-up endoscopy was found to be a significant predictor of hospitalization risk in patients with UC (p = 0.015), but not in those with CD. However, there was no significant difference in cumulative hospitalization hazard with respect to treatment change in patients without any endoscopic indications (p = 0.561 in CD and 0.423 in UC). Follow-up endoscopy might not have a significant impact on the overall clinical course and outcomes in patients with IBD. However, the presence of endoscopic indications predicts a poor clinical outcome in UC.

Kang W.J.,Yonsei University
Korean Journal of Radiology | Year: 2015

A large number of major cardiovascular events occur in patients due to minimal or some lumen narrowing of the coronary artery. Recent biological studies have shown that the biological composition or vulnerability of the plaque is more critical for plaque rupture compared to the degree of stenosis. To overcome the limitations of anatomical images, molecular imaging techniques have been suggested as promising imaging tools in various fields. F-18 fluorodeoxyglucose (FDG), which is widely used in the field of oncology, is an example of molecular probes used in atherosclerotic plaque evaluation. FDG is a marker of plaque macrophage glucose utilization and inflammation, which is a prominent characteristic of vulnerable plaque. Recently, F-18 fluoride has been used to visualize vulnerable plaque in clinical studies. F-18 fluoride accumulates in regions of active microcalcification, which is normally observed during the early stages of plaque formation. More studies are warranted on the accumulation of F-18 fluoride and plaque formation/vulnerability; however, due to high specific accumulation, low background activity, and easy accessibility, F-18 fluoride is emerging as a promising non-invasive imaging probe to detect vulnerable plaque. © 2015 The Korean Society of Radiology.

The present invention relates to a method for selective cell attachment/detachment, cell patternization and cell harvesting by means of near infrared rays. More particularly, conducting polymers or metal oxides having exothermic characteristics upon irradiation of near infrared light is used as a cell culture scaffold, thus selectively attaching/detaching cells without an enzyme treatment. The scaffold has an effect of promoting proliferation or differentiation of stem cells, and therefore, can be used as a stem cell culture scaffold. The scaffold enables cell attachment/detachment without temporal or spatial restrictions, thus enabling cell patternization.

Samsung and Yonsei University | Date: 2014-07-03

Disclosed is a computed tomography (CT) system which includes a rotatable collimator. The CT system includes a gantry. The gantry includes an X-ray source that generates X-rays, a collimator that is provided inside the X-ray source to be rotatable and that limits an irradiation area of the X-rays generated by the X-ray source, and an X-ray detector that is provided at a side portion of the X-ray source.

Yonsei University and Samsung | Date: 2013-11-13

A method of patterning a block copolymer layer, the method including: providing a substrate with a guide pattern formed on a surface thereof; forming a block copolymer layer on the substrate with the guide pattern, the block copolymer layer including a block copolymer; and directing self-assembly of the block copolymer on the substrate according to the guide pattern to form n/2 discrete domains, wherein the guide pattern includes a block copolymer patter