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Search Results: 1 - 10 of 140740 matches for " Sungjoo K Yoon "
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Gene expression profile of the skin in the 'hairpoor' (HrHp) mice by microarray analysis
Bong-Kyu Kim, In-Cheol Baek, Hwa-Young Lee, Jeong-Ki Kim, Hae-Hiang Song, Sungjoo K Yoon
BMC Genomics , 2010, DOI: 10.1186/1471-2164-11-640
Abstract: From 45,282 mouse probes, differential expressions in 43 (>2-fold), 306 (>1.5-fold), and 1861 genes (>1.2-fold) in skin from HrHp/HrHp mice were discovered and compared with skin from wild-type mice. Among the 1861 genes with a > 1.2-fold increase in expression, further analysis showed that the expression of eight genes known to have a close relationship with hair follicle development, ascertained by conducting real-time PCR on skin RNA produced during hair follicle morphogenesis (P0-P14), indicated that four genes, Wif1, Casp14, Krt71, and Sfrp1, showed a consistent expression pattern with respect to HR overexpression in vivo.Wif1 and Casp14 were found to be upregulated, whereas Krt71 and Sfrp1 were downregulated in cells overexpressing HR in transient transfection experiments on keratinocytes, suggesting that HR may transcriptionally regulate these genes. Further studies are required to understand the mechanism of this regulation by the HR cofactor.With a complex and dynamic structure, hair is generated by hair-producing follicles and has a patterned cycle of growth and remodeling, which consists of growth (anagen), regression (catagen), and rest (telogen) stages. There are many genes involved in mature hair follicle (HF) regulation [1].One of these genes, hairless (Hr), is expressed in skin, specifically in the suprabasal cell layer of the interfollicular epidermis and in the lower portion of the HF epithelium; its expression is dependent on the hair cycle. Hr encodes a 130 kDa protein (HR), which contains a zinc finger domain and is localized in the nucleus [2], and acts as a transcriptional corepressor that regulates transcription through directly binding to the thyroid hormone receptor [3,4], vitamin D receptor [5], and retinoic acid-like orphan receptor α [6].Various Hr mutant mice have been studied to understand the function of HR, and most Hr mutant mice are created by causing the loss of HR function in their cells, giving them a typical phenotype with a re
Ge-Photodetectors for Si-Based Optoelectronic Integration
Jian Wang,Sungjoo Lee
Sensors , 2011, DOI: 10.3390/s110100696
Abstract: High speed photodetectors are a key building block, which allow a large wavelength range of detection from 850 nm to telecommunication standards at optical fiber band passes of 1.3–1.55 μm. Such devices are key components in several applications such as local area networks, board to board, chip to chip and intrachip interconnects. Recent technological achievements in growth of high quality SiGe/Ge films on Si wafers have opened up the possibility of low cost Ge-based photodetectors for near infrared communication bands and high resolution spectral imaging with high quantum efficiencies. In this review article, the recent progress in the development and integration of Ge-photodetectors on Si-based photonics will be comprehensively reviewed, along with remaining technological issues to be overcome and future research trends.
Optimal Stop Points for Data Gathering in Sensor Networks with Mobile Sinks  [PDF]
Junyoung Park, Kyoungjin Moon, Sungjoo Yoo, Sunggu Lee
Wireless Sensor Network (WSN) , 2012, DOI: 10.4236/wsn.2012.41002
Abstract: Given a wireless sensor network (WSN) in which a mobile sink is used to collect data from the sensor nodes, this paper addresses the problem of selecting a set of stop points that results in low energy usage by the sensor nodes. This paper assumes an approach in which a mobile sink travels along a fixed path and uses a stop-and-collect protocol since this has previously been shown to be an efficient WSN data collection method. The problem of selecting an optimal set of stop points is shown to be an NP-hard problem. Then, an Integer Linear Programming (ILP) formulation is used to derive an optimal algorithm that can be used for small problem instances. Next, a polynomial-time Tabu-search-based heuristic algorithm is proposed. Simulations are used to compare the energy consumption values, computation times and expected network lifetimes when using the optimal ILP algorithm, the proposed heuristic algorithm and several other possible heuristic algorithms. The results show that the proposed heuristic algorithm results in near-optimal energy usage values with low computation times, thereby making it suitable for large-sized WSNs.
Does anybody read "evidence-based" articles?
Yoon K Loke, Sheena Derry
BMC Medical Research Methodology , 2003, DOI: 10.1186/1471-2288-3-14
Abstract: Narrative reviews and editorials are accessed more frequently than primary research papers or systematic reviews in the first week after their publication. These findings may disappoint those who believe that it is important for readers to critically appraise the primary research data.Although the technical quality of journal articles may have been helped by recommendations on structured reporting, the readability of such articles has received little attention. Authors and journal editors must take steps to make research articles and systematic reviews more attractive to readers. This may involve using simpler language, as well as innovative use of web resources to produce shorter, snappier papers, with the methodological or technical details made available elsewhere.Primary research and "evidence-based" papers seem to be less attractive to readers than narrative reviews and editorials in the first week after publication. Authors and editors should try to improve the early appeal of primary research papers.One of the benefits of publishing on the Internet is that the numbers of visitors to a particular article can be easily recorded and displayed. The electronic British Medical Journal (eBMJ) website has a unique "Hit Parade" section, with web access statistics for every online article dating back to 1999.[1] This "Hit Parade" records the number of electronic visits ("hits") in the first week of the article's publication.We were disappointed to find, for instance, that the editorial accompanying a meta-analysis we published in 2000 had been viewed nearly 4000 times whereas the paper itself had received only 1236 visitors.[2,3] This prompted us to ask what people read when they visit the eBMJ. Do they prefer narrative-style articles to original research or evidence-based publications?We assessed the viewing figures in the Hit Parade for all issues, except the Christmas edition, of the eBMJ published in the year 2001. We divided the journal articles into the following
An overview of the benefits and drawbacks of inhaled corticosteroids in chronic obstructive pulmonary disease
Sonal Singh, Yoon K Loke
International Journal of Chronic Obstructive Pulmonary Disease , 2010, DOI: http://dx.doi.org/10.2147/COPD.S6942
Abstract: n overview of the benefits and drawbacks of inhaled corticosteroids in chronic obstructive pulmonary disease Review (11263) Total Article Views Authors: Sonal Singh, Yoon K Loke Published Date June 2010 Volume 2010:5 Pages 189 - 195 DOI: http://dx.doi.org/10.2147/COPD.S6942 Sonal Singh1, Yoon K Loke2 1Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA; 2School of Medicine, Health Policy and Practice, University of East Anglia, Norwich, England Background: The benefit harm profile of inhaled corticosteroids, and their effect on patient oriented outcomes and comorbid pneumonia, osteoporosis and cardiovascular disease in patients with chronic obstructive pulmonary disease remain uncertain. Methods: An overview of the evidence on the risks and benefits of inhaled corticosteroids (fluticasone and budesonide) in chronic obstructive pulmonary disease from recent randomized controlled trials and systematic reviews. Observational studies on adverse effects were also evaluated. Results: Evidence from recent meta-analysis suggests a modest benefit from inhaled corticosteroid long-acting beta-agonist combination inhalers on the frequency of exacerbations, (rate ratio [RR], 0.82; 95% confidence interval [CI]: 0.78 to 0.88), in improvements in quality of life measures, and forced expiratory volume in one second when compared to long-acting beta-agonists alone. On the outcome of pneumonia, our updated meta-analysis of trials (n = 24 trials; RR, 1.56; 95% CI: 1.40–1.74, P < 0.0001) and observational studies (n = 4 studies; RR, 1.44; 95% CI: 1.20–1.75, P = 0.0001) shows a significant increase in the risk of pneumonia with the inhaled corticosteroids currently available (fluticasone and budesonide). Evidence for any intraclass differences in the risk of pneumonia between currently available formulations is inconclusive due to the absence of head to head trials. Inhaled corticosteroids have no cardiovascular effects. Conclusions: Among patients with chronic obstructive pulmonary disease, clinicians should carefully balance these long-term risks of inhaled corticosteroid against their symptomatic benefits.
Drug safety assessment in clinical trials: methodological challenges and opportunities
Singh Sonal,Loke Yoon K
Trials , 2012, DOI: 10.1186/1745-6215-13-138
Abstract: Randomized controlled trials are the principal means of establishing the efficacy of drugs. However pre-marketing trials are limited in size and duration and exclude high-risk populations. They have limited statistical power to detect rare but potentially serious adverse events in real-world patients. We summarize the principal methodological challenges in the reporting, analysis and interpretation of safety data in clinical trials using recent examples from systematic reviews. These challenges include the lack of an evidentiary gold standard, the limited statistical power of randomized controlled trials and resulting type 2 error, the lack of adequate ascertainment of adverse events and limited generalizability of trials that exclude high risk patients. We discuss potential solutions to these challenges. Evaluation of drug safety requires careful examination of data from heterogeneous sources. Meta-analyses of drug safety should include appropriate statistical methods and assess the optimal information size to avoid type 2 errors. They should evaluate outcome reporting biases and missing data to ensure reliable and accurate interpretation of findings. Regulatory and academic partnerships should be fostered to provide an independent and transparent evaluation of drug safety.
An overview of the benefits and drawbacks of inhaled corticosteroids in chronic obstructive pulmonary disease
Sonal Singh,Yoon K Loke
International Journal of COPD , 2010,
Abstract: Sonal Singh1, Yoon K Loke21Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA; 2School of Medicine, Health Policy and Practice, University of East Anglia, Norwich, EnglandBackground: The benefit harm profile of inhaled corticosteroids, and their effect on patient oriented outcomes and comorbid pneumonia, osteoporosis and cardiovascular disease in patients with chronic obstructive pulmonary disease remain uncertain.Methods: An overview of the evidence on the risks and benefits of inhaled corticosteroids (fluticasone and budesonide) in chronic obstructive pulmonary disease from recent randomized controlled trials and systematic reviews. Observational studies on adverse effects were also evaluated.Results: Evidence from recent meta-analysis suggests a modest benefit from inhaled corticosteroid long-acting beta-agonist combination inhalers on the frequency of exacerbations, (rate ratio [RR], 0.82; 95% confidence interval [CI]: 0.78 to 0.88), in improvements in quality of life measures, and forced expiratory volume in one second when compared to long-acting beta-agonists alone. On the outcome of pneumonia, our updated meta-analysis of trials (n = 24 trials; RR, 1.56; 95% CI: 1.40–1.74, P < 0.0001) and observational studies (n = 4 studies; RR, 1.44; 95% CI: 1.20–1.75, P = 0.0001) shows a significant increase in the risk of pneumonia with the inhaled corticosteroids currently available (fluticasone and budesonide). Evidence for any intraclass differences in the risk of pneumonia between currently available formulations is inconclusive due to the absence of head to head trials. Inhaled corticosteroids have no cardiovascular effects.Conclusions: Among patients with chronic obstructive pulmonary disease, clinicians should carefully balance these long-term risks of inhaled corticosteroid against their symptomatic benefits.Keywords: inhaled corticosteroids, chronic obstructive pulmonary disease, pneumonia, cardiovascular events
Binomial Schedule for an M/G/1 Type Queueing System with an Unreliable Server under -Policy
Lotfi Tadj,K. Paul Yoon
Advances in Decision Sciences , 2014, DOI: 10.1155/2014/819718
Abstract: We consider in this paper an M/G/1 type queueing system with the following extensions. First, the server is unreliable and is subject to random breakdowns. Second, the server also implements the well-known -policy. Third, instead of a Bernoulli vacation schedule, the more general notion of binomial schedule with vacations is applied. A cost function with two decision variables is developed. A numerical example shows the effect of the system parameters on the optimal management policy. 1. Introduction Queueing systems where the server uses her/his idle time to perform some secondary job such as maintenance are called systems with server vacations. These systems have received a lot of attention due to their wide applications in different domains such as telecommunications, computer systems, service systems, and production and quality control problems. Survey papers have been written on this subject; the most recent one being that of Ke et al. [1]. Keilson and Servi [2] introduced a class of vacation models called the Bernoulli vacation schedule. When a customer has just been served and other customers are present, the server serves the next customer in line with probability or takes a vacation of random duration with probability . The Bernoulli vacation schedule has been extensively considered. Among the most recent references we cite Kumar et al. [3], Choudhury and Ke [4], Gao and Liu [5], Tao et al. [6, 7], and Wu and Lian [8]. Kella [9] generalized the Bernoulli vacation schedule to a more general scheme according to which the server goes on consecutive vacations with probability if the queue upon her/his return is empty. Ba-Rukab et al. [10] propose another generalization. They argued that since the server may attend different activities while idle, a binomial vacation schedule may be more appropriate than a Bernoulli vacation schedule. In that case, instead of taking just one vacation, the server may take many vacations, for a maximum number of, say, vacations. Yadin and Naor introduced the -policy in which, following an idle period, the server resumes his service only when the number of waiting customers reaches the level . This policy is efficient in that it reduces setup costs. The -policy too has been extensively studied by researches. We refer the reader to the following recent references: Kumar and Jain [11], Lee and Yang [12], Lim et al. [13], and Wei et al. [14]. Another characteristic of servers in a queueing system is that they may break down while providing service. White and Christie [15] were the first to study a queueing system with an
Impurities, Quantum Interference and Quantum Phase Transitions in s-wave superconductors
Dirk K. Morr,Jaesung Yoon
Physics , 2006, DOI: 10.1103/PhysRevB.73.224511
Abstract: We study the effects of quantum interference in impurity structures consisting of two or three magnetic impurities that are located on the surface of an s-wave superconductor. By using a self-consistent Bogoliubov-de Gennes formalism, we show that quantum interference leads to characteristic signatures not only in the local density of states (LDOS), but also in the spatial form of the superconducting order parameter. We demonstrate that the signatures of quantum interference in the LDOS are qualitatively, and to a large extent quantitatively unaffected by the suppression of the superconducting order parameter near impurities, which illustrates the robustness of quantum interference phenomena. Moreover, we show that by changing the interimpurity distance, or the impurities' scattering strength, the s-wave superconductor can be tuned through a series of first order quantum phase transitions in which the spin polarization of its ground state changes. In contrast to the single impurity case, this transition is not necessarily accompanied by a $\pi$-phase shift of the order parameter, and can in certain cases even lead to its enhancement. Our results demonstrate that the superconductor's LDOS, its spin state, and the spatial form of the superconducting order parameter are determined by a subtle interplay between the relative positions of the impurities and their scattering strength.
A Complete and Simple Solution to a Discrete-Time Finite-Capacity BMAP/D/c Queue  [PDF]
Nam K. Kim, Mohan L. Chaudhry, Bong K. Yoon, Kilhwan Kim
Applied Mathematics (AM) , 2012, DOI: 10.4236/am.2012.312A297
Abstract: We consider a discrete-time multi-server finite-capacity queueing system with correlated batch arrivals and deterministic service times (of single slot), which has a variety of potential applications in slotted digital telecommunication systems and other related areas. For this queueing system, we present, based on Markov chain analysis, not only the steady-state distributions but also the transient distributions of the system length and of the system waiting time in a simple and unified manner. From these distributions, important performance measures of practical interest can be easily obtained. Numerical examples concerning the superposition of certain video traffics are presented at the end.

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