Publications by authors named "Namhoon Lee"

Understanding the behavior of organic carbon in municipal solid waste landfills is a major challenge for estimating methane (CH) emissions using the Intergovernmental Panel on Climate Change (IPCC) first-order decay (FOD) model. According to the IPCC guidelines, the default values of CH correction factor (MCF) and fraction of CH (F) for active aeration landfills are set as 0.4 and 0.

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The molecular radicals, systems with unpaired electrons of open-shell electronic structures, set the stage for a multidisciplinary science frontier relevant to the cooperative magnetic exchange interaction and magnetoelectric effect. Here ferroelectricity together with magnetic spin exchange coupling in molecular radical hydrocarbon solids is reported, representing a new class of magnetoelectrics. Electronic correlation through radical-radical interactions plays a decisive role in the coupling between magnetic and charge orders.

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Background: Using analysis of air samples from the workplace, we report on one case of pneumoconiosis in an individual who has been working in a polytetrafluoroethylene (PTFE) spraying process for 28 years.

Case Presentation: The patient was diagnosed with granulomatous lung disease caused by PTFE using computed tomography (CT), lung biopsy and electron microscopy. To assess the qualitative and quantitative exposure to PTFE in workplace, Fourier transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDX) and thermogravimetric analysis (TGA) were performed on air samples from the workplace.

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Background: Achieving neutral limb alignment during total knee arthroplasty (TKA) has been considered an important determinant in the long-term prosthesis survival. The purpose of this study was to evaluate the association between the immediate postoperative mechanical alignment of the lower limb and the rate of revision TKA by comparing an acceptable mechanical axis group (within ± 3° from neutral alignment) and an outlier group (> 3° deviation from neutral alignment).

Methods: Between 2000 and 2006, clinical and radiographic data of 334 primary TKAs were retrospectively reviewed to determine the 10-year Kaplan-Meier survival rate.

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In the first order decay (FOD) model of landfill methane generation, the methane generation potential ( L) and methane generation rate constant ( k) for both bulk municipal solid waste (MSW) and individual waste components have been determined by a variety of approaches throughout various literature. Differences in the determination methods for L and k are related to differences in our understanding of the waste decomposition dynamics. A thorough understanding of the various available methods for determining L and k values is critical for comparative study and the drawing of valid conclusions.

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Background: Arsenic is known as an endocrine disruptor that people are exposed to through various sources such as drinking water and indigestion of marine products. Although some epidemiological and animal studies have reported a correlation between arsenic exposure and diabetes development, there are limited studies regarding the toxic effects of organic arsenic including arsenobetaine on the human body. Here, we analyzed the association between urine arsenobetaine and the homeostasis model assessment of β-cell function (HOMA-β), which is an index for predicting diabetes development and reflecting the function of pancreatic β-cells.

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The aim of this study was to investigate the possibility of measuring methane emission fluxes, using surface methane concentration and gauge pressure, by analyzing the influence of gauge pressure on the methane emission flux and the surface methane concentration, as well as the correlation between the methane emission flux and surface methane concentrations. The surface methane concentration was measured using a laser methane detector. Our results show a positive linear relationship between the surface methane concentration and the methane emission flux.

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Leachate recirculation for rapid landfill stabilization can result in the accumulation of high-strength ammonium. An on-site sequencing batch reactor (SBR) was therefore, applied to oxidize the ammonium to nitrite, which was then recirculated to the landfill for denitrification to nitrogen gas. At relatively higher ammonium levels, nitrite accumulated well in the SBR; the nitrite was denitrified stably in the landfill, despite an insufficient biodegradable carbon source in the leachate.

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Due to the increase in energy cost by constantly high oil prices and the obligation to reduce greenhouse effect gases, landfill gas is frequently used as an alternative energy source for producing heat and electricity. Most of landfill gas utility facilities, however, are experiencing problems controlling siloxanes from landfill gas as their catalytic oxidizers are becoming fouled by silicon dioxide dust. To evaluate adsorption characteristics of siloxanes, an adsorption equilibrium test was conducted and parameters in the Freundlich and Langmuir isotherms were analyzed.

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We developed a new method of fabricating a divalent copper ion (Cu(2+)) modified DNA thin film on a glass substrate and studied its magnetic properties. We evaluated the coercive field (Hc), remanent magnetization (Mr), susceptibility (χ), and thermal variation of magnetization with varying Cu(2+) concentrations [Cu(2+)] resulting in DNA thin films. Although thickness of the two dimensional DNA thin film with Cu(2+) in dry state was extremely thin (0.

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Objective: Microsatellite alterations, especially those that cause loss of heterozygosity (LOH), have recently been postulated as a novel mechanism of carcinogenesis and a useful prognostic factor in many kinds of malignant tumors. However, few studies have focused on a specific site, hypopharynx. The aim of this study was to evaluate the relationship between LOH and hypopharyngeal squamous cell carcinoma (HPSCC).

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Background: MHC CLASS I TRANSCRIPTION IS REGULATED BY TWO DISTINCT TYPES OF REGULATORY PATHWAYS: 1) tissue-specific pathways that establish constitutive levels of expression within a given tissue and 2) dynamically modulated pathways that increase or decrease expression within that tissue in response to hormonal or cytokine mediated stimuli. These sets of pathways target distinct upstream regulatory elements, have distinct basal transcription factor requirements, and utilize discrete sets of transcription start sites within an extended core promoter.

Methodology/principal Findings: We studied regulatory elements within the MHC class I promoter by cellular transfection and in vitro transcription assays in HeLa, HeLa/CIITA, and tsBN462 of various promoter constructs.

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Here, we report on a new zeolite-based silicalite nanoparticle that can enhance the transfection efficiencies generated by poly ethylene imine-plasmid DNA (PEI-pDNA) complexes via a sedimentation mechanism and can enhance the transfection efficiencies of pDNA alone when surface functionalized with amine groups. The silicalite nanoparticles have a mean size of 55 nm. Functionalizing the silicalite nanoparticles with amine groups results in a clear transition in zeta potential from -25.

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