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Search Results: 1 - 10 of 40775 matches for " Yun Sang Lee "
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Intellectual Interchanges in the History of Massive Online Open-editing Encyclopedia, Wikipedia
Jinhyuk Yun,Sang Hoon Lee,Hawoong Jeong
Computer Science , 2015,
Abstract: Wikipedia is a free Internet encyclopedia with enormous amount of contents. This encyclopedia is written by volunteers with various backgrounds in a collective fashion; anyone can access and edit most of the articles. This open editing nature may give us prejudice that Wikipedia is unstable and unreliable sources; yet many studies suggest that Wikipedia is even more accurate and self-consistent than traditional encyclopedias. Scholars have attempted to understand such extraordinary credibility, but usually used the edit number without consideration of real-time. In this work, we probe the formation of such collective intelligence through the systematic analysis using the entire history of 34,534,110 English Wikipedia articles, between 2001 and 2014. From this massive data set, we observe the universality of both timewise and lengthwise editing scales, which suggests that it is essential to consider the real-time dynamics. By considering real-time, we find the existence of various growth patterns that are unobserved in terms of the number of edits as the time step. To account these results, we present a mechanistic model that adopts both the article editing dynamics based on editor-editor and editor-article interactions. The model successfully generates some key properties of the real Wikipedia articles such as distinct types of articles for the editing patterns characterized by the interrelationship between the numbers of edits and editors, and the article size. In addition, the model indicates that infrequently referred articles tend to grow faster than frequently referred one, and articles attracting high motivation of edit counterintuitively reduce the number of participants. We suggest that this decay of participants eventually brings inequality among the editors, which will be more severe with time.
The genome-scale metabolic network analysis of Zymomonas mobilis ZM4 explains physiological features and suggests ethanol and succinic acid production strategies
Kyung Lee, Jong Park, Tae Kim, Hongseok Yun, Sang Lee
Microbial Cell Factories , 2010, DOI: 10.1186/1475-2859-9-94
Abstract: The genome-scale metabolic model of Z. mobilis ZM4, ZmoMBEL601, was reconstructed based on its annotated genes, literature, physiological and biochemical databases. The metabolic model comprises 579 metabolites and 601 metabolic reactions (571 biochemical conversion and 30 transport reactions), built upon extensive search of existing knowledge. Physiological features of Z. mobilis were then examined using constraints-based flux analysis in detail as follows. First, the physiological changes of Z. mobilis as it shifts from anaerobic to aerobic environments (i.e. aerobic shift) were investigated. Then the intensities of flux-sum, which is the cluster of either all ingoing or outgoing fluxes through a metabolite, and the maximum in silico yields of ethanol for Z. mobilis and Escherichia coli were compared and analyzed. Furthermore, the substrate utilization range of Z. mobilis was expanded to include pentose sugar metabolism by introducing metabolic pathways to allow Z. mobilis to utilize pentose sugars. Finally, double gene knock-out simulations were performed to design a strategy for efficiently producing succinic acid as another example of application of the genome-scale metabolic model of Z. mobilis.The genome-scale metabolic model reconstructed in this study was able to successfully represent the metabolic characteristics of Z. mobilis under various conditions as validated by experiments and literature information. This reconstructed metabolic model will allow better understanding of Z. mobilis metabolism and consequently designing metabolic engineering strategies for various biotechnological applications.The impact of biotechnology on industry and society is dramatically gaining momentum, particularly in the field of agriculture-food, medicine and chemical production. For the chemical industry, which aims to producing value-added chemicals and fuels in a sustainable way, efforts have been put into strain improvement of microorganisms, utilizing many newly emergin
Prediction of novel synthetic pathways for the production of desired chemicals
Ayoun Cho, Hongseok Yun, Jin Park, Sang Lee, Sunwon Park
BMC Systems Biology , 2010, DOI: 10.1186/1752-0509-4-35
Abstract: In the present study, we propose a system framework employing a retrosynthesis model with a prioritization scoring algorithm. This new strategy allows deducing the novel promising pathways for the synthesis of a desired chemical together with information on enzymes involved based on structural changes and reaction mechanisms present in the system database. The prioritization scoring algorithm employing Tanimoto coefficient and group contribution method allows examination of structurally qualified pathways to recognize which pathway is more appropriate. In addition, new concepts of binding site covalence, estimation of pathway distance and organism specificity were taken into account to identify the best synthetic pathway. Parameters of these factors can be evolutionarily optimized when a newly proven synthetic pathway is registered. As the proofs of concept, the novel synthetic pathways for the production of isobutanol, 3-hydroxypropionate, and butyryl-CoA were predicted. The prediction shows a high reliability, in which experimentally verified synthetic pathways were listed within the top 0.089% of the identified pathway candidates.It is expected that the system framework developed in this study would be useful for the in silico design of novel metabolic pathways to be employed for the efficient production of chemicals, fuels and materials.In the past few decades, various systematic methods have been developed for the prediction of synthetic metabolic pathways for the production of chemicals by employing microorganisms [1-15]. These methods can be classified by whether the approach is based on chemical structural changes, enzymatic information, and/or reaction mechanisms. The method based on chemical structural changes is applied to reconstruct the network which represents the relationship among the biochemical compounds using the structure-based homology analysis [1-4]. This method generates a variety of novel pathways, but prediction to specify the enzymes is dif
Mesh Simplification Using the Edge Attributes
Yun Il Dong,Choo Kyowoong,Lee Sang Uk
EURASIP Journal on Advances in Signal Processing , 2002,
Abstract: This paper presents a novel technique for simplifying a triangulated surface at different levels of resolution. While most existing algorithms, based on iterative vertex decimation, employ the distance for error metric, the proposed algorithm utilizes an edge criterion for removing a vertex. An interior angle of a vertex is defined as the maximum value of all possible angles formed by combinations of edges connected to a vertex. Since the surface curvature examined with the interior angle provides more information for decision of vertex removal than the conventional distance measure, the proposed algorithm can approximate the surface with less computation. The height of a triangle, which is formed by the pair of edges, is also used for an additional constraint. The computational complexity can thus be greatly alleviated to logarithmic scale from the exponential scale required for the conventional algorithms, while yielding the comparable error level.
Vector magnetometry based on S=3/2 electronic spins
Sang-Yun Lee,Matthias Niethammer,J?rg Wrachtrup
Physics , 2015, DOI: 10.1103/PhysRevB.92.115201
Abstract: Electronic spin systems with S>1/2 provide an efficient method for DC vector magnetometry, since the conventional electron spin resonance spectra at a given magnetic field reflect not only the field strength but also orientation in the presence of strong spin-spin interactions. S=1 spins, e.g. the nitrogen-vacancy centers in diamond, have been intensively investigated for such a purpose. In this report, we compare S=1 and S=3/2 spins, and discuss how one can apply general principles for the use of high spin systems as a vector magnetometer to the S=3/2 spin systems. We find analytical solutions which allow a reconstruction of the magnetic field strength and polar angle using the observed resonance transitions if an uniaxial symmetry exists for the spin-spin interaction as in S=1 systems. We also find that an ambiguity of determining the field parameters may arise due to the unique properties of S=3/2 systems, and present solutions for it utilizing additional transitions in the low-field region. The electronic spins of the silicon vacancy in silicon carbide will be introduced as a model for the S=3/2 DC vector magnetometer and the practical usage of it, including the magic-angle spinning type method, will be presented too.
Incidence and Clinical Characteristics of Deep Vein Thrombosis (DVT) after Total Knee Arthroplasty (TKA) with DVT Chemoprophylaxis  [PDF]
Yong Sung Won, Mihyeong Kim, Kang Woong Jun, Woo Seok Nam, Sanghyun Ahn, Jeong-Kye Hwang, Sang-Dong Kim, Sun-Cheol Park, Sang Seob Yun, Won-Chul Lee, Jang-Sang Park, Jang Yong Kim
World Journal of Cardiovascular Diseases (WJCD) , 2014, DOI: 10.4236/wjcd.2014.411064
Abstract: Objective: Deep vein thrombosis (DVT) after total knee arthroplasty (TKA) is very common and leading cause of death due to this procedure. The objective of this study was to investigate the incidence and clinical characteristics of DVT after TKA with DVT chemoprophylaxis. Methods: This is a prospective cohort study in single institution. The patients received postoperative DVT chemoprophylaxis (low molecular weight heparin (LMWH) or Fondaparinux), followed by duplex ultrasonography to check for DVT 1 - 2 weeks after TKA. The clinical characteristics were summarized and analysed by chi-square test and regression analysis. Results: Five hundred and thirty four patients were enrolled from January 2007 to December 2010. DVT chemoprophylaxis was administered in 524 (98.1%) of the 534 patients. DVT occurred in 9 subjects (1.69%); 8 subjects had DVT in the leg, and 1 subject had a pulmonary embolism. Among them, asymptomatic DVT was observed in 5 patients (0.94%). Univariate analysis showed that surgical methods (revision, P = 0.0007), body mass index (BMI) (>25, P = 0.0028), low platelet count (less than 150 × 103, P = 0.0219), time in the intensive care unit (ICU) (P < 0.0001), no administration of prophylactic LMWH (P = 0.0392), and a history of DVT (P < 0.0001) were significant risk factors of DVT. Conclusions: The incidence of DVT was 1.69% after TKA with prophylactic antithrombotic therapy. Revision surgery, BMI, low platelet count, time in ICU, absence of prophylactic LMWH and history of DVT were significant risk factors of DVT.
Anonymous Authorship Control for User-Generated Content
Suk-Bong LEE,Sang-Gyoo SIM,Yeo-Jin KIM,Yun-Sang OH
Journal of Systemics, Cybernetics and Informatics , 2007,
Abstract: User-Generated Content (UGC) is opening up new large market in content services, and more and more people are visiting web sites to share and enjoy UGCs. These trends make many authors to move into online. Authors want to conserve their authorship and expect to publish their UGC anonymously in cases. To meet the requirements, we propose a new authorship control model based on watermarking and metadata. Authors can embed their authorship into their UGC with identities or with anonym. Even though an author publishes his UGC anonymously, he can prove his authorship without unveiling his identity via 5 methods utilizing the proposed authorship model. The proposed model and methods need no TTP and are robust even based on fragile underlying watermarking scheme.
Growth mechanisms of vapor-born polymer films
I. J. Lee,Mira Yun,Sang-Min Lee,Ja-Yeon Kim
Physics , 2008, DOI: 10.1103/PhysRevB.78.115427
Abstract: The surface morphologies of poly(chloro-p-xylylene) films were measured using atomic force microscopy and analyzed within the frame work of the dynamic scaling theory. The evolution of polymer films grown with fixed experimental parameters showed drastic changes of dynamic roughening behavior, which involve unusually high growth exponent (beta = 0.65+-0.03) in the initial growth regime, followed by a regime characterized by beta~0, and finally a crossover to beta = 0.18+-0.02 in a steady growth regime. Detailed scaling analysis of the surface fluctuation in Fourier space in terms of power spectral density revealed a gradual crossover in the global roughness exponent, analogous to a phase transition between two equilibrium states, from a morphology defined by alpha=1.36+-0.13 to the other morphology characterized by alpha=0.93+-0.04 as the film thickness increases. Our experimental results which significant deviate from the well established descriptions of film growth clearly exhibit that the dynamic roughening of polymer film is deeply affected by strong molecular interactions and relaxations of polymer chains.
Do Really Close Stomata by Soil Drying ABA Produced in the Roots and Transported in Transpiration Stream?  [PDF]
Joon Sang Lee
American Journal of Plant Sciences (AJPS) , 2013, DOI: 10.4236/ajps.2013.41022
Abstract: Stomatal aperture responses of Commelina communis L. between well watered plants and water stressed plants were investigated. To see the very rapid response to water stress, the plants were directly rooted out from the soil and exposed to the air immediately. Stomata, rooted out from the soil, were totally closed within 10 minutes without any detention time while the stomata of the plants in the soil had been kept opening. These results suggest that stomatal response to the abrupt water stress is very rapid indicating that guard cell itself or leaves could sense water status in the plants.
In Vivo Transcription Dynamics of the Galactose Operon: A Study on the Promoter Transition from P1 to P2 at Onset of Stationary Phase
Sang Chun Ji,Xun Wang,Sang Hoon Yun,Heung Jin Jeon,Hee Jung Lee,Hackjin Kim,Heon M. Lim
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0017646
Abstract: Quantitative analyses of the 5′ end of gal transcripts indicate that transcription from the galactose operon P1 promoter is higher during cell division. When cells are no longer dividing, however, transcription is initiated more often from the P2 promoter. Escherichia coli cells divide six times before the onset of the stationary phase when grown in LB containing 0.5% galactose at 37°C. Transcription from the two promoters increases, although at different rates, during early exponential phase (until the third cell division, OD600 0.4), and then reaches a plateau. The steady-state transcription from P1 continues in late exponential phase (the next three cell divisions, OD600 3.0), after which transcription from this promoter decreases. However, steady-state transcription from P2 continues 1 h longer into the stationary phase, before decreasing. This longer steady-state P2 transcription constitutes the promoter transition from P1 to P2 at the onset of the stationary phase. The intracellular cAMP concentration dictates P1 transcription dynamics; therefore, promoter transition may result from a lack of cAMP-CRP complex binding to the gal operon. The decay rate of gal-specific transcripts is constant through the six consecutive cell divisions that comprise the exponential growth phase, increases at the onset of the stationary phase, and is too low to be measured during the stationary phase. These data suggest that a regulatory mechanism coordinates the synthesis and decay of gal mRNAs to maintain the observed gal transcription. Our analysis indicates that the increase in P1 transcription is the result of cAMP-CRP binding to increasing numbers of galactose operons in the cell population.
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