39 results on '"Nah Y"'
Search Results
2. Decoration of TiO 2 nanotube layers with WO 3 nanocrystals for high-electrochromic activity
- Author
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Benoit, A., Paramasivam, I., Nah, Y.-C., Roy, P., and Schmuki, P.
- Published
- 2009
- Full Text
- View/download PDF
3. The role of gastrointestinal endoscopy in long-distance runners with gastrointestinal symptoms.
- Author
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Choi SC, Choi SJ, Kim JA, Kim TH, Nah Y, Yazaki E, Evans DF, Choi, S C, Choi, S J, Kim, J A, Kim, T H, Nah, Y H, Yazaki, E, and Evans, D F
- Published
- 2001
- Full Text
- View/download PDF
4. High-Skilled Inventor Emigration as a Moderator for Increased Innovativeness and Growth in Sending Countries
- Author
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Jisong Kim and Nah Youn Lee
- Subjects
High-skilled Inventor Emigration ,Technology Transfer ,Innovativeness ,Growth Rate ,Externalities ,Networks ,Economics as a science ,HB71-74 - Abstract
This study investigates the effect of high-skilled inventor emigration rate on growth rate of the country of origin (COO). Inventor emigrants represent the human capital that can generate highly innovative work. The social network they form spurs knowledge diffusion and technology transfer back to their COOs, which in turn affects innovation and growth in their home countries. We run dynamic panel estimation for 154 countries during 1990?2011, and empirically show that a positive and statistically significant effect exists for the interaction of inventor emigration and trade. The result indicates that the direct negative impact of the brain drain can be mitigated by the positive feedback effect generated by the high-skilled inventor emigrants abroad. When coupled with an active trade policy that reinforces growth, countries can partially recoup the direct effect of the human capital loss. We stress the importance of international trade for successful technology transfer to occur, and offer insights for policies that can utilize the benefits of the rich social network of their high-skilled emigrants.
- Published
- 2019
- Full Text
- View/download PDF
5. TMO-structured cluster-based real-time management of location data on massive volume of moving items.
- Author
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Nah, Y., Moon Hae Kim, Taehyung Wang, Kim, K.H., and Young Kyu Yang
- Published
- 2003
- Full Text
- View/download PDF
6. The Effect of High-Skilled Emigration, Foreign Direct Investment, and Policy on the Growth Rate of Source Countries: A Panel Analysis
- Author
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Jisong Kim and Nah Youn Lee
- Subjects
High-skilled Emigration ,Brain Drain ,FDI ,Democracy ,Growth Rate ,Economics as a science ,HB71-74 - Abstract
We study the effect of the high-skilled emigration rate on the growth rate of the source countries. We incorporate the foreign direct investment and the policy variables into the panel model and also their interactions with the high-skilled emigration rate, as they are related to the network externality that may be created by the high-skilled emigrants working abroad. We apply the static fixed-effects model and compare it with the results obtained in the dynamic panel model with system generalized methods of moments estimators. We find the negative effect of the high-skilled emigration rate by itself and in its interaction with the foreign direct investment only in the dynamic model. However, we find positive coefficient for the interaction of the high-skilled emigration rate and the civil liberties index, which holds across the static and dynamic specifications. This implies that the effect of the high-skilled emigration rate on the growth rate of the source countries can be positive, and the extent is larger for countries with 'poor' civil liberties. The developing countries with low levels of foreign direct investment inflows and 'poor' civil liberties can best benefit from the high levels of skilled emigration outward. Through finding significant interactions with other variables, we confirm that the high-skilled emigration should be considered along with other related variables in measuring its impact on growth. The implications offer suggestions for the international trade and aid policies.
- Published
- 2016
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7. PROTEIN KINASE C-DELTA (PKC-D) AS DONOR FACTOR DETERMINING ALLOGRAFT REJECTION.
- Author
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Cho, H R., Kwon, B, Nam, C W., and Nah, Y W.
- Published
- 2008
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8. Nitrogen removal in household wastewater treatment using an intermittently aerated membrane bioreactor
- Author
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Ahn, K. H., Nah, Y. M., and Yeom, I. T.
- Subjects
NITROGEN ,WASTEWATER treatment - Published
- 2000
9. Decoration of TiO2 nanotube layers with WO3 nanocrystals for high-electrochromic activity
- Author
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Benoit, A., Paramasivam, I., Nah, Y.-C., Roy, P., and Schmuki, P.
- Subjects
- *
TITANIUM dioxide , *NANOTUBES , *HYDROLYSIS , *TUNGSTEN oxides , *NANOCRYSTALS , *ELECTROCHEMISTRY - Abstract
Abstract: We report a simple approach to decorate ordered TiO2 nanotube (TiNT) layers with tungsten trioxide nanocrystallites by the controlled hydrolysis of a WCl6 precursor. These WO3 nanocrystallites, when formed, are amorphous, but can be annealed to a monoclinic crystal structure. The WO3 crystallites on the TiO2 nanotube skeleton are electrochemically active, and hence ion insertion reactions are possible. As a result, the decorated nanotube layers show remarkable enhancement of the electrochromic properties. In particular, a significantly lower threshold voltage and an increased electrochromic contrast can be achieved compared with unloaded (neat) TiO2 nanotube layers. [Copyright &y& Elsevier]
- Published
- 2009
- Full Text
- View/download PDF
10. I/O Efficient Algorithm for c-Approximate Furthest Neighbor Search in High-Dimensional Space
- Author
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Wenjie Zhang, Lu Qin, Ying Zhang, Wanqi Liu, Hanchen Wang, Nah, Y, Cui, B, Lee, S-W, Yu, JX, Moon, Y-S, and Whang, SE
- Subjects
050101 languages & linguistics ,Current (mathematics) ,Furthest Neighbor ,Computer science ,Nearest neighbor search ,05 social sciences ,02 engineering and technology ,Computer Science::Computational Geometry ,Recommender system ,Space (mathematics) ,Locality-sensitive hashing ,0202 electrical engineering, electronic engineering, information engineering ,020201 artificial intelligence & image processing ,0501 psychology and cognitive sciences ,Artificial Intelligence & Image Processing ,Algorithm ,Auxiliary memory ,Curse of dimensionality - Abstract
© 2020, Springer Nature Switzerland AG. Furthest Neighbor search in high-dimensional space has been widely used in many applications such as recommendation systems. Because of the “curse of dimensionality” problem, c-approximate furthest neighbor (C-AFN) is a substitute as a trade-off between result accuracy and efficiency. However, most of the current techniques for external memory are only suitable for low-dimensional space. In this paper, we propose a novel algorithm called reverse incremental LSH based on Indyk’s LSH scheme to solve the problem with theoretical guarantee. Unlike the previous methods using hashing scheme, reverse incremental LSH (RI-LSH) is designed for external memory and can achieve a good performance on I/O cost. We provide rigorous theoretical analysis to prove that RI-LSH can return a-AFN result with a constant possibility. Our comprehensive experiment results show that, compared with other-AFN methods with theoretical guarantee, our algorithm can achieve better I/O efficiency.
- Published
- 2020
11. Depression, stress, coping, and electrogastrography of the functional dyspepsia
- Author
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Choi, S-C, Seo, G-S, Nah, Y-H, Lee, S-Y, and Park, M-C
- Published
- 1998
- Full Text
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12. Treatment of abnormal rectal sensation in cerebrosinal disease with biofeedback
- Author
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Nah, Y-H, Choi, SC, and Jin, KM
- Published
- 1995
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13. Tailored small molecule for inflammation treatment: Dual scavenger targeting nitric oxide and reactive oxygen species.
- Author
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Nah Y, Kim J, Lee S, Koh WG, and Kim WJ
- Subjects
- Animals, Mice, RAW 264.7 Cells, Phenylenediamines pharmacology, Phenylenediamines chemistry, Gallic Acid pharmacology, Gallic Acid chemistry, Gallic Acid therapeutic use, Peritonitis drug therapy, Peritonitis chemically induced, Male, Cytokines metabolism, Reactive Oxygen Species metabolism, Nitric Oxide metabolism, Lipopolysaccharides, Anti-Inflammatory Agents pharmacology, Anti-Inflammatory Agents administration & dosage, Anti-Inflammatory Agents therapeutic use, Anti-Inflammatory Agents chemistry, Inflammation drug therapy, Inflammation metabolism, Free Radical Scavengers pharmacology, Free Radical Scavengers administration & dosage, Free Radical Scavengers therapeutic use
- Abstract
Inflammation-related diseases are often marked by elevated levels of nitric oxide (NO) and reactive oxygen species (ROS), which play important roles in the modulation of inflammation. However, the development of organic materials effective in managing NO/ROS levels has remained a challenge. This study introduces a novel organic compound, NmeGA, engineered to scavenge both NO and ROS. NmeGA ingeniously integrates N-methyl-1,2,-phenylenediamine (Nme), a NO scavenger, with gallic acid (GA), a ROS scavenger, through an amide bond, endowing it with enhanced scavenging capabilities over its individual component. This compound exhibits reduced toxicity and increased lipophilicity value, underlining its increased biological applicability and highlighting its potential as an inflammation management tool. Through in vitro studies on lipopolysaccharide (LPS)-stimulated RAW 264.7 cells, NmeGA displayed remarkable scavenging efficiency for NO and ROS, coupled with significant anti-inflammatory effects. In an LPS-induced peritonitis model, administration of NmeGA substantially decreased mortality rates, NO and ROS levels, and inflammatory cytokine concentrations. These findings highlight NmeGA's versatility as a therapeutic agent against various inflammatory diseases., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2024 Elsevier B.V. All rights reserved.)
- Published
- 2024
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14. Nitric oxide-scavenging hyaluronic acid nanoparticles for osteoarthritis treatment.
- Author
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Nah Y, Sobha S, Saravanakumar G, Kang BY, Yoon JB, and Kim WJ
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- Mice, Animals, Hyaluronic Acid chemistry, Nitric Oxide, Inflammation drug therapy, Pain drug therapy, Nanoparticles, Osteoarthritis drug therapy, Cartilage, Articular
- Abstract
Osteoarthritis (OA) is a degenerative arthritis disease marked by inflammation, pain, and cartilage deterioration. Elevated nitric oxide (NO) levels play a pivotal role in mediating OA-related inflammation and are found in abundance within OA joints. This study introduces a NO-scavenging hyaluronic acid conjugate (HA-NSc) bearing both lubrication and anti-inflammatory properties for the treatment of osteoarthritis. For this, a derivative of o -phenylenediamine ( o -PD) with good NO-scavenging capability (NSc) is designed, synthesized and chemically conjugated to HA. Owing to the amphiphilicity, this as-synthesized HA-NSc conjugate formed self-assembled nanoparticles (HA-NSc NPs) under aqueous conditions. When treated with activated murine macrophage RAW 264.7 cells that produce high levels of NO, these nanoparticles effectively reduced intracellular NO concentrations and inflammatory cytokines. In an OA animal model, the HA-NSc NPs significantly alleviated pain and diminished the cartilage damage due to the combined lubricating property of HA and NO-scavenging ability of NSc. Overall, the results from the study suggest HA-NSc NPs as a dual-action therapeutic agent for the treatment of OA by alleviating pain, inflammation, and joint damage, and also positioning the HA-NSc NPs as a promising candidate for innovative treatment of OA.
- Published
- 2024
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15. Transformation of nanoparticles via the transition of functional DNAs responsive to pH and vascular endothelial growth factor for photothermal anti-tumor therapy.
- Author
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Kim J, Nah Y, Kim S, and Kim WJ
- Subjects
- Humans, Vascular Endothelial Growth Factor A, Gold chemistry, DNA, Hydrogen-Ion Concentration, Tumor Microenvironment, Metal Nanoparticles chemistry, Neoplasms drug therapy
- Abstract
This study presents a novel approach for the development of DNA-functionalized gold nanoparticles (AuNPs) capable of responding to disease-specific factors and microenvironmental changes, resulting in an effective anti-tumor effect via photothermal therapy. The AuNPs are decorated with two types of DNAs, an i-motif duplex and a VEGF split aptamer, enabling recognition of changes in pH and VEGF, respectively. The formation of VEGF aptamers on the AuNPs induces their aggregation, further enhanced by VEGF ligands. The resulting changes in the optical properties of the AuNPs are detected by monitoring the absorbance. Upon irradiation with a near-infrared laser, the aggregated AuNPs generate heat due to their thermoplasmonic characteristic, leading to an anti-tumor effect. This study demonstrates the enhanced anti-tumor effect of DNA-functionalized AuNPs via photothermal therapy in both in vitro and in vivo tumor models. These findings suggest the potential utilization of such functional AuNPs for precise disease diagnosis and treatment by detecting disease-related factors in the microenvironment.
- Published
- 2024
- Full Text
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16. IDO-triggered swellable polymeric micelles for IDO inhibition and targeted cancer immunotherapy.
- Author
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Park J, Nah Y, and Kim WJ
- Subjects
- Humans, Kynurenine, Micelles, Drug Delivery Systems, Immunotherapy, Tumor Microenvironment, Tryptophan chemistry, Tryptophan pharmacology, Neoplasms drug therapy
- Abstract
Indoleamine 2,3-dioxygenase (IDO) has been studied as a promising target for cancer immunotherapy. IDO catalyzes the oxidation of tryptophan into kynurenine, which subsequently activates regulatory T cells, thereby promoting an immunosuppressive microenvironment in the tumor tissue. Due to its overexpression in tumor cells, IDO itself could be a tumor-specific stimulus for targeted cancer therapy. Toward this objective, we developed IDO-triggered swellable micelles for targeted cancer immunotherapy. The micelles are prepared by the self-assembly of amphiphilic polymers containing polymerized tryptophan as a hydrophobic block. The micelles exhibited IDO-responsive behavior via solubility conversion of the hydrophobic core triggered by the oxidation of tryptophan residues into kynurenine. The micelles were internalized into tumor cells and disassembled by overexpressed IDO. Loaded with IDO inhibitor, the micelle presented enhanced therapeutic antitumor effect, and effector T-cells were recruited into the tumor tissue. We demonstrated that overexpressed IDO in cancer cells could be utilized as a tumor-specific stimulus, and utilizing an IDO-responsive drug delivery system holds great promise for targeted cancer therapy and immunomodulation., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)
- Published
- 2023
- Full Text
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17. A Case of Abnormal Liver Function Tests in a Patient Receiving Total Parenteral Nutrition.
- Author
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Tran T, Rim DS, Nolen-Doerr E, Lopez M, Nah Y, Sharma K, Shin JH, and Kim DW
- Subjects
- Female, Humans, Middle Aged, Liver Function Tests, Parenteral Nutrition, Total adverse effects, Liver Diseases diagnosis, Liver Diseases etiology, Cholestasis diagnosis, Cholestasis etiology
- Abstract
Hepatic dysfunction is prevalent in patients receiving total parenteral nutrition (TPN), resulting from steatosis, cholestasis, and cholecystitis. Regular assessments and monitoring of TPN patients are essential, even for clinically stable patients on long-term TPN. Furthermore, it is crucial to establish a differential diagnosis for hepatic dysfunction and investigate for other possible causes of elevated liver enzymes and underlying liver conditions. We present the case of a 56-year-old female patient with severe protein-calorie malnutrition on TPN, who exhibited significantly elevated liver enzymes during the routine periodic assessment. Subsequent investigation revealed that the patient had been taking traditional Chinese herbal medications concurrently with TPN. After discontinuing the herbal medications, the patient's liver enzymes returned to normal levels within 3 weeks.
- Published
- 2023
- Full Text
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18. Nitric-Oxide-Modulatory Materials for Biomedical Applications.
- Author
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Kim T, Nah Y, Kim J, Lee S, and Kim WJ
- Subjects
- Nitric Oxide metabolism, Polymers
- Abstract
Nitric oxide (NO) is an endogenous signaling molecule that participates in various physiological and biological pathways associated with vasodilation, immune response, and cell apoptosis. Interestingly, NO has versatile and distinct functions in vivo depending on its concentration and the duration of exposure; it aids cellular proliferation at nanomolar concentrations but causes cellular death at micromolar concentrations. Therefore, achieving the precise and on-demand modulation of microenvironmental NO concentrations has become a major research target in biomedical fields. To this end, many studies have investigated feasible means for developing functional moieties that can either exogenously donate or selectively scavenge NO. However, these advances are limited by poor stability and a lack of target specificity, which represent two significant obstacles regarding the spatiotemporal adjustment of NO in vivo . Our group has addressed this issue by contributing to the development of next-generation NO-modulatory materials over the past decade. Over this period, we utilized various polymeric, inorganic, and hybrid systems to enhance the bioavailability of traditional NO donors or scavengers in an attempt to maximize their clinical usage while also minimizing their unwanted side effects. In this Account, strategies regarding the rational design of NO-modulatory materials are first summarized and discussed, depending on their specific purposes. These strategies include chemical approaches for encapsulating traditional NO donors inside specific vehicles; this prevents spontaneous NO release and allows said donors to be exposed on-demand, under a certain stimulus. The current status of these approaches and the recent contributions of other groups are also comprehensively discussed here to ensure an objective understanding of the topic. Moreover, in this paper, we discuss strategies for the selective depletion of NO from local inflammatory sites, where the overproduction of NO is problematic. Finally, the major challenges for current NO-modulatory systems are discussed, and requirements are outlined that need to be tackled to achieve their future therapeutic development. Starting from this current, relatively early stage of development, we propose that, through continuous efforts to surmount existing challenges, it will be possible in the future to achieve clinical translations regarding NO-modulatory systems. This Account provides insightful guidelines regarding the rational design of NO-modulatory systems for various biomedical applications. Moreover, it can facilitate the achievement of previously unattainable goals while revolutionizing future therapeutics.
- Published
- 2022
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19. Narrowing the Phase Distribution of Quasi-2D Perovskites for Stable Deep-Blue Electroluminescence.
- Author
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Nah Y, Solanki D, Dong Y, Röhr JA, Taylor AD, Hu S, Sargent EH, and Kim DH
- Abstract
Solution-processed quasi-2D perovskites contain multiple quantum wells with a broad width distribution. Inhomogeneity results in the charge funneling into the smallest bandgap components, which hinders deep-blue emission and accelerates Auger recombination. Here, a synthetic strategy applied to a range of quasi-2D perovskite systems is reported, that significantly narrows the quantum well dispersity. It is shown that the phase distribution in the perovskite film is significantly narrowed with controlled, simultaneous evaporation of solvent and antisolvent. Modulation of film formation kinetics of quasi-2D perovskite enables stable deep-blue electroluminescence with a peak emission wavelength of 466 nm and a narrow linewidth of 14 nm. Light emitting diodes using the perovskite film show a maximum luminance of 280 cd m
-2 at an external quantum efficiency of 0.1%. This synthetic approach will serve in producing new materials widening the color gamut of next-generation displays., (© 2022 The Authors. Advanced Science published by Wiley-VCH GmbH.)- Published
- 2022
- Full Text
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20. Prefrontal cortical activation in Internet Gaming Disorder Scale high scorers during actual real-time internet gaming: A preliminary study using fNIRS.
- Author
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Cho TH, Nah Y, Park SH, and Han S
- Abstract
Background: Observation of real-time neural characteristics during gameplay would provide distinct evidence for discriminating the currently controversial diagnosis of internet gaming disorder (IGD), and elucidate neural mechanisms that may be involved in addiction. We aimed to provide preliminary findings on possible neural features of IGD during real-time internet gaming using functional near-infrared spectroscopy (fNIRS)., Methods: Prefrontal cortical activations accompanying positive and negative in-game events were investigated. Positive events: (1) participant's champion slays or assists in slaying an opponent without being slain. (2) the opposing team's nexus is destroyed. Negative events: (1) participant's champion is slain without slaying or assisting in slaying any opponent. (2) the team's nexus is destroyed. Collected data were compared between the IGD group and control group, each with 15 participants., Results: The IGD group scored significantly higher than the CTRL group on the craving scale. Following positive events, the IGD group displayed significantly stronger activation in the DLPFC. Following negative events, the IGD group displayed significantly weaker activation in the lateral OFC., Discussion and Conclusions: Individuals scoring high on the IGD scale may crave for more internet gaming after encountering desired events during the game. Such observations are supported by the correlation between the craving scale and DLPFC activation. The IGD group may also show diminished punishment sensitivity to negative in-game experiences rendering them to continue playing the game. The present study provides preliminary evidence that IGD may demonstrate neural characteristics observed in other addictive disorders and suggests the use of fNIRS in behavioral addiction studies.
- Published
- 2022
- Full Text
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21. Neural correlates of empathy for babies in postpartum women: A longitudinal study.
- Author
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Bak Y, Nah Y, Han S, Lee SK, Kim J, and Shin NY
- Subjects
- Adult, Brain Mapping, Female, Gyrus Cinguli diagnostic imaging, Humans, Longitudinal Studies, Magnetic Resonance Imaging, Pattern Recognition, Visual physiology, Prefrontal Cortex diagnostic imaging, Young Adult, Empathy physiology, Gyrus Cinguli physiology, Mentalization physiology, Postpartum Period physiology, Prefrontal Cortex physiology
- Abstract
This study investigated the empathic response of postpartum women to babies in pain and the underlying neural mechanism. Postpartum women responded with more empathy and speed to babies over other stimuli compared to controls. Brain scans taken 3 months after birth showed more elevated activation in the Middle cingulate cortex/middle frontal gyrus (MCC/MFG) than the controls regardless of the task condition. When compared to the adult and neutral conditions, the posterior cingulate cortex (PCC) region was consistently more activated when postpartum women saw babies than controls. In addition, higher activation levels in the PCC region for the baby condition significantly correlated with faster and more empathic responses to babies. Considering that PCC is a core region for the theory of mind or mentalizing which requires cognitive reasoning to understand others, these results suggest that PCC might be a pivotal neural locus facilitating cognitive efforts to empathize with babies during the postpartum period. In a follow-up experiment at 12 months after birth, we were still able to observe higher activity in the MCC/MFG of postpartum women. However, previously observed PCC activation patterns disappeared 12 months after birth, despite the women's response patterns to babies still being maintained. These results suggest that the mentalizing process activated to empathize with babies in the early postpartum period becomes less cognitively demanding over time., (© 2021 The Authors. Human Brain Mapping published by Wiley Periodicals LLC.)
- Published
- 2021
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22. Block copolymer micelles enable facile synthesis of organic-inorganic perovskite nanostructures with tailored architecture.
- Author
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Nah Y, Jang D, and Kim DH
- Abstract
We report a distinct method for the production of organic-inorganic hybrid perovskite (OIHP) nanostructures using block copolymer micelles as scaffolds. We reveal that various nanostructures can be obtained by controlling the parameters related to micelle disassembly. The strategy reported herein can be generalized for the fabrication of diverse nanostructures toward target-oriented potential applications.
- Published
- 2021
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23. Spectral Instability of Layered Mixed Halide Perovskites Results from Anion Phase Redistribution and Selective Hole Injection.
- Author
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Nah Y, Allam O, Kim HS, Choi JI, Kim IS, Byun J, Kim SO, Jang SS, and Kim DH
- Abstract
Despite the ability to precisely tune their bandgap energies, mixed halide perovskites (MHPs) suffer from significant spectral instability, which obstructs their utilization for the rational design of light-emitting diodes. Here, we investigate the origin of the electroluminescence peak shifts in layered MHPs containing bromide and iodide. X-ray diffraction and steady-state absorption measurements prove effective integration of iodide into the cubic lattice and the spatially uniform distribution of halides in the ambient environment. However, the applied electric field during the device operation is found to drive the systematic halide migration. Quantum mechanical density functional theory calculations reveal that the different activation energies required for directional ion hopping lead to the redistribution of anions. In-depth analyses of the electroluminescence spectra indicate that the spectral shifting rate is dependent on the drift velocity of halides. Finally, it is suggested from our study that the dominant red emission is ascribed to the thermodynamically favorable selective hole injection. Our mechanistic study provides insights into the fundamental reason for the spectral instability of devices based on MHPs.
- Published
- 2021
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24. Altered neural substrates within cognitive networks of postpartum women during working memory process and resting-state.
- Author
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Bak Y, Nah Y, Han S, Lee SK, and Shin NY
- Subjects
- Adult, Brain diagnostic imaging, Female, Humans, Magnetic Resonance Imaging, Memory Disorders etiology, Nerve Net diagnostic imaging, Neuropsychological Tests, Young Adult, Brain physiology, Brain physiopathology, Cognition physiology, Memory Disorders diagnosis, Memory, Short-Term, Nerve Net physiology, Postpartum Period physiology, Postpartum Period psychology, Rest physiology
- Abstract
Postpartum working memory decline has been investigated mostly with neuropsychological tests, but neural evidence is almost unknown. Here we investigated task-related neural alterations during working memory task (n-back) and intrinsic alterations during resting-state (rs) in postpartum women using functional MRI (fMRI). Behaviorally, postpartum women showed comparable working memory performances to the controls although there was a tendency of prolonged response time. fMRI analysis results showed hyper-activation in regions belong to the task positive network (TPN) during the task and hypo-rsfMRI values in the default mode network (DMN) regions during rest in postpartum women. Based on these results, we performed network connectivity analysis using nodes of the TPN and DMN. As a result, the DMN showed a tendency of decreased connectivity in postpartum women during the working memory process compared to the controls. Our results suggest that postpartum women might have functional alterations in the DMN, and that hyper-activation in the TPN during a task might be a compensatory mechanism to maintain working memory performance in postpartum women.
- Published
- 2020
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25. Universal perpendicular orientation of block copolymer microdomains using a filtered plasma.
- Author
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Oh J, Suh HS, Ko Y, Nah Y, Lee JC, Yeom B, Char K, Ross CA, and Son JG
- Abstract
Sub-10 nm patterns prepared by directed self-assembly (DSA) of block copolymer (BCP) thin films offer a breakthrough method to overcome the limitations of photolithography. Perpendicular orientation of the BCP nanostructures is essential for lithographic applications, but dissimilar surface/interfacial energies of two blocks generally favour parallel orientations, so that the perpendicular orientation could only be obtained under very limited conditions. Here, we introduce a generalized method for creating perpendicular orientations by filtered plasma treatment of the BCP films. By cross-linking the surface of disordered BCP films using only physical collisions of neutral species without ion bombardment or UV irradiation, neutral layers consistent with the BCP volume fraction are produced that promote the perpendicular orientations. This method works with BCPs of various types, volume fractions, and molecular weights individually at the top and bottom interfaces, so it was applied to orientation-controlled 3D multilayer structures and DSA processes for sub-10 nm line-spacing patterns.
- Published
- 2019
- Full Text
- View/download PDF
26. Monocycloplatinated Solvento Complex Displays Turn-on Ratiometric Phosphorescence Responses to Histamine.
- Author
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Park G, Yu S, Kim S, Nah Y, Son A, and You Y
- Abstract
The study of biological histamine (HA) requires probes capable of ratiometric photoluminescence detection of HA. We discovered that a monocycloplatinated complex having two solvento ligands ([Pt(2-(2-naphthyl)quinolinate)(NCCH
3 )2 ]ClO4 ) could produce ratiometric phosphorescence responses to HA in aerated aqueous solutions buffered to pH 7.4. The HA response was characterized with a hypsochromic shift of an emission peak wavelength from 635 to 567 nm. The corresponding phosphorescence intensity ratio (i.e., I567 nm / I635 nm ) increased from 0.26 to 1.90. Spectroscopic and spectrometric investigations indicated an occurrence of spontaneous displacement of the labile CH3 CN ligands with HA. An independently prepared HA adduct supported this notion. The ratiometric phosphorescence responses to HA were highly tolerant to other biological stimuli, including changes in pH and the presence of biometals and biological Lewis bases such as amino acids, nucleosides, biothiols, neurotransmitters, and small molecular metabolites. Of note was the high selectivity toward HA over common biological ligands, including histidine, cysteine, and homocysteine, which was ascribed to tighter HA binding. Our phosphorescence measurements employing Boc-protected derivatives of HA suggested that the bis-chelate motif involving imidazolyl and terminal amino groups was crucial for eliciting the ratiometric phosphorescence signaling. Finally, the bioimaging utility of the HA probe was validated using RAW 264.7 macrophages that were exogenously supplemented with HA or stimulated with thapsigargin to enrich intracellular HA. Ratiometric phosphorescence imaging microscopy experiments demonstrated the ability of the probe for monitoring intracellular HA uptake. In addition, photoluminescence lifetime imaging microscopy techniques could be applied for visualization of HA within the RAW 264.7 cells, because the HA binding elongated the photoluminescence lifetime. Our study demonstrated the promising utility of inner-sphere interactions of phosphorescent Pt(II) complexes for detection of biological HA.- Published
- 2018
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- View/download PDF
27. Author Correction: Disturbed retrieval network and prospective memory decline in postpartum women.
- Author
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Shin NY, Bak Y, Nah Y, Han S, Kim DJ, Kim SJ, Lee JE, Lee SG, and Lee SK
- Abstract
A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.
- Published
- 2018
- Full Text
- View/download PDF
28. Data on subjective recollection effects reflected in large-scale functional connectivity patterns in postpartum women.
- Author
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Nah Y, Shin NY, Yi S, Lee SK, and Han S
- Abstract
Functional neuroimaging data was collected while postpartum women and age-matched control women performed the Remember/Know judgment task in the functional magnetic resonance imaging scanner. This data provides information about functional connectivity patterns across the subjective recollection networks that were informative in differentiating the postpartum women from control women. Classification performances based on machine learning algorithms and descriptions of functional connectivity patterns that derived the peak classification accuracy are reported in this article. All other results from our study have been reported in Nah et al. (2018) [1].
- Published
- 2018
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29. Disturbed retrieval network and prospective memory decline in postpartum women.
- Author
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Shin NY, Bak Y, Nah Y, Han S, Kim DJ, Kim SJ, Lee JE, Lee SG, and Lee SK
- Subjects
- Adult, Estradiol blood, Female, Humans, Magnetic Resonance Imaging, Nerve Net diagnostic imaging, Surveys and Questionnaires, Young Adult, Memory, Episodic, Nerve Net physiology, Postpartum Period physiology
- Abstract
Prospective memory (PM) refers to the ability to remember to execute an intended action in the future. For successful PM performance, both top-down strategic monitoring and bottom-up spontaneous retrieval processes need to be appropriately recruited. We assessed PM performance and used fMRI to discover relevant neural correlates and possible predictors for PM performance in 25 postpartum and 26 nulliparous age- and education-matched women. Postpartum women showed decreased PM performance, a higher number of nocturnal awakenings, and lower estradiol level. The postpartum women had decreased functional connectivity (FC) in the right hippocampus and ventral frontoparietal networks (FPN) during retrieval-dominant PM trials relative to maintenance-dominant ongoing trials in the PM block. On multivariate analyses, decreased FC between the right hippocampus and ventral FPN and a higher number of nocturnal awakenings were independent predictors for poor PM performance after adjusting for age, education, estradiol level, and depressive symptoms. On mediation analyses, the estradiol level was found to have an indirect effect on PM accuracy via altered FC as a mediator. This suggests that decreased FC within the spontaneous retrieval-related regions including the right hippocampus and ventral FPN, disrupted sleep rhythms, and decreased estradiol level may contribute to poor PM performance in postpartum women.
- Published
- 2018
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30. Altered task-dependent functional connectivity patterns during subjective recollection experiences of episodic retrieval in postpartum women.
- Author
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Nah Y, Shin NY, Yi S, Lee SK, and Han S
- Subjects
- Adult, Brain physiology, Brain Mapping, Female, Humans, Magnetic Resonance Imaging, Nerve Net physiology, Neuropsychological Tests, Postpartum Period psychology, Brain diagnostic imaging, Memory, Episodic, Nerve Net diagnostic imaging, Postpartum Period physiology
- Abstract
Numerous studies have suggested that postpartum women show a decline in cognitive abilities. However, to date, no study has investigated the presence of qualitative alterations in recognition memory processes in postpartum women that may lead to a decline in cognitive ability. To address this issue, we employed the Remember/Know procedure and functional magnetic resonance imaging (fMRI). Behavioral results demonstrated that compared with the matched control (CTRL) group, the postpartum (PP) group endorsed "Remember" less and "Know" more to old items. A univariate analysis of fMRI data indicated lower neural activity of the subjective recollection network in the PP group than in the CTRL group. We also performed a large-scale functional connectivity multivariate pattern analysis (fcMVPA) using task-dependent time-series to detect differences in functional connectivity patterns and neural interactivity between the PP and CTRL groups. The fcMVPA results revealed that the PP group exhibited altered functional connectivity patterns from which machine learning algorithms could discriminate group membership with 94% accuracy. Collectively, these findings demonstrated that altered subjective recollection processes in the PP group during episodic memory decisions are associated with diminished neural activity and abnormal interactivity across the subjective recollection network. We believe that this is one of the first studies demonstrating qualitative alterations in recognition memory processes in postpartum women., (Copyright © 2018 Elsevier Inc. All rights reserved.)
- Published
- 2018
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31. Transparent TiO2 nanotube electrodes via thin layer anodization: fabrication and use in electrochromic devices.
- Author
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Berger S, Ghicov A, Nah YC, and Schmuki P
- Abstract
In the present work, we describe an anodization process that is able to fully transform a thin Ti metal layer on a conductive glass into a TiO(2) nanotubular array. Under optimized conditions, nanotube electrodes can be obtained that are completely transparent and defect-free and allow electrochromic switching. These electrochromic electrodes show remarkable properties and can be directly integrated into devices.
- Published
- 2009
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- View/download PDF
32. Isolated acute cellular rejection of the liver after simultaneous liver and kidney transplantation: a case report.
- Author
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Nah YW, Nam CW, Suh JH, Cha HJ, Kim GY, Park SJ, Oh Y, and Cho HR
- Subjects
- Acute Disease, Biopsy, Humans, Inflammation, Kidney Transplantation pathology, Liver Circulation, Male, Middle Aged, Treatment Outcome, Graft Rejection diagnosis, Immunosuppressive Agents therapeutic use, Kidney Transplantation immunology, Liver Transplantation immunology, Methylprednisolone Hemisuccinate therapeutic use
- Abstract
Simultaneous liver and kidney transplantation (SLKT) is now considered the treatment of choice for patients with concurrent end-stage liver and kidney diseases. Even though the early postoperative mortality rate following SLKT is reported to be high compared to that of liver transplantation alone, the liver graft from the same donor has been argued to induce better kidney graft acceptance as evidenced by a low rate of acute renal rejection episodes. There have been many reports of a low incidence of acute renal rejection following SLKT; however, only a few cases were proven by simultaneous biopsies. The authors experienced a case of biopsy-proven isolated acute cellular rejection of the liver graft following SLKT.
- Published
- 2008
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33. Modified right liver graft from a living donor to prevent congestion.
- Author
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Gyu Lee S, Min Park K, Hwang S, Hun Kim K, Nak Choi D, Hyung Joo S, Soo Anh C, Won Nah Y, Yeong Jeon J, Hoon Park S, Suck Koh K, Hoon Han S, Taek Choi K, Sam Hwang K, Sugawara Y, Makuuchi M, and Chul Min P
- Subjects
- Adolescent, Adult, Female, Hepatectomy methods, Hepatic Veins diagnostic imaging, Humans, Liver Transplantation mortality, Male, Middle Aged, Portal Vein diagnostic imaging, Portal Vein surgery, Postoperative Complications prevention & control, Ultrasonography, Vascular Patency, Hepatic Veins surgery, Liver Circulation, Liver Transplantation methods, Living Donors
- Abstract
Background: Right liver grafts without middle hepatic vein (MHV) drainage reconstruction resulted in severe congestion of the anterior segment (AS) in our early experience of adult-to-adult living donor liver transplantation (LDLT). However, a detailed strategy for preventing such congestion or the necessity of MHV reconstruction has not been discussed in LDLT using a right lobe graft., Methods: From July 1997 to February 1998, two of five right lobe grafts without MHV drainage reconstruction were complicated with severe congestion of the AS. Thereafter, 42 adult recipients who received right liver grafts with sizable MHV tributaries underwent the reconstruction of MHV drainage. All sizable (>5 mm in diameter) MHV tributaries were preserved during donor hepatectomy and were reconstructed with the recipient's autogenous interposition vein grafts at the bench surgery. The reconstructed vein grafts of this modified right lobe graft were anastomosed to the stump of the MHV and/or left hepatic vein of the recipient after graft revascularization., Results: Serial Doppler ultrasonography, which was regularly checked until 30 days posttransplant, revealed the patent interposition vein graft in 38 of 42 recipients (patency rate 90.5%). In these 38 recipients, no evidence of congestion in the AS was recognized on enhanced computed tomography, while providing enough functioning liver mass comparable to an extended right lobe graft. Also, congestion-related graft injury, such as an infarct of the AS, was not observed in these recipients., Conclusions: Our early experience indicated the necessity of MHV drainage reconstruction in right lobe grafts, which do not have MHV trunk in certain instances. However, preoperatively, it is difficult to predict the degree of AS congestion of the right liver graft without MHV drainage reconstruction. We suggest aggressive reconstruction of MHV drainage tributaries of the AS, under the circumstances that sizable MHV tributaries are encountered, to prevent possible congestion-related complications.
- Published
- 2002
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34. An adult-to-adult living donor liver transplant using dual left lobe grafts.
- Author
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Lee S, Hwang S, Park K, Lee Y, Choi D, Ahn C, Nah Y, Koh K, Han S, Park S, and Min P
- Subjects
- Hepatitis B surgery, Humans, Liver Regeneration, Male, Middle Aged, Liver Cirrhosis surgery, Liver Transplantation methods, Living Donors
- Published
- 2001
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35. Effect of graded running on esophageal motility and gastroesophageal reflux in fed volunteers.
- Author
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Choi SC, Yoo KH, Kim TH, Kim SH, Choi SJ, and Nah YH
- Subjects
- Adult, Esophageal Motility Disorders etiology, Gastroesophageal Reflux etiology, Humans, Male, Postprandial Period, Eating, Esophageal Motility Disorders physiopathology, Gastroesophageal Reflux physiopathology, Running
- Abstract
The effects of different grades of running on esophageal motility and gastroesophageal reflux in the fed state were evaluated. We studied healthy volunteers (male: 12, age: 27 +/- 5 yr) using ambulatory esophageal manometry, pH catheter and portable digital data recorder. Each exercise was performed 30 min after meal, with 20 min of rest between exercises. Subjects exercised on a treadmill at 40% and 70% maximal heart rate. The number of gastroesophageal reflux episodes, the duration of esophageal acid exposure and percent time pH below 4 were significantly (p < 0.01) increased during exercise at 70% maximal heart rate. The frequency of contraction (contraction/min) (p < 0.05), frequency of repetition (p < 0.01), percent of simultaneous contraction (p < 0.01), percent of above 100 mmHg amplitude (p < 0.05), and frequency of 2-peak contraction (p < 0.01) were significantly increased during exercise at 70% maximal heart rate. However, median amplitude and median duration showed no significant changes between each exercise session. Postprandial running exercises induce gastroesophageal reflux, which correlates with exercise intensity. These effects are mediated by disorganized esophageal motility.
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- 2001
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36. Stress, coping, and depression in non-ulcer dyspepsia patients.
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Lee S, Park M, Choi S, Nah Y, Abbey SE, and Rodin G
- Subjects
- Adolescent, Adult, Aged, Anxiety diagnosis, Anxiety psychology, Depression diagnosis, Female, Humans, Male, Middle Aged, Personality Inventory, Adaptation, Psychological, Depression psychology, Dyspepsia psychology, Psychophysiologic Disorders psychology, Stress, Psychological complications
- Abstract
Thirty adults with upper gastrointestinal symptoms in the absence of structural organic disease diagnosed with non-ulcer dyspepsia (NUD) were compared to 30 healthy adults who had visited the hepatobiliary clinic for medical evaluation of non-organic complaints without NUD. Medical investigation in both groups were negative. Before independent gastrointestinal physicians conducted diagnostic evaluations, all subjects were evaluated for anxiety and depressive symptoms, stressful life events, coping style, and social support. The measures included Symptom Checklist 90-Revised (SCL-90-R), Beck Depression Inventory (BDI), Spielberger State-Trait Anxiety Inventory (STAI), Ways of Coping Checklist, and Interpersonal Support Evaluation List, and a self-report questionnaire, which measured the quantity of perceived stressful life events. The NUD patients reported significantly more symptoms of depression, more perceived stressful life events, less problem-focused coping, and less social support than the control subjects. Depressive symptoms were negatively correlated with interpersonal support, whereas, problem-focused coping was positively correlated with interpersonal support in the NUD patients. The two groups did not differ significantly in terms of anxiety and emotion-focused coping. The implications of these findings for the diagnosis and treatment of NUD are discussed.
- Published
- 2000
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37. Effects of galvanic stimulation of the mastoid process on the gastric motility induced by caloric stimulation.
- Author
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Park BR, Kim MS, Lee MY, Kim YK, Choi SC, and Nah YH
- Subjects
- Adult, Electric Stimulation, Electrodiagnosis instrumentation, Female, Fourier Analysis, Humans, Male, Signal Processing, Computer-Assisted instrumentation, Stomach innervation, Autonomic Nervous System physiology, Caloric Tests, Gastric Emptying physiology, Mastoid physiology, Vestibular Nerve physiology
- Abstract
The effects of galvanic stimulation to the mastoid portion on the vestibuloautonomic symptoms induced by caloric stimulation, such as nausea, vomiting, and vertigo, were evaluated in this study. Gastric motility was measured by electrogastrography (EGG) in 20 healthy volunteers (11 male and nine female) aged 20-30 (average: 25.4) years. Electrical stimulation of the mastoid process with 1.0-3.0 mA, 1.0 ms, 100 Hz was applied using a bipolar-biaural method during caloric stimulation of the external auditory canal. The dominant frequency and power of EGG were determined using running spectral frequency analysis and the time-course of EGG was evaluated in a pseudo three dimensional graphic. Frequency of EGG was classified into normogastria with 3 cpm, bradygastria with lower than 3 cpm, and tachygastria with higher than 3 cpm. At quiescent period, normogastria was 78.7 +/- 3.7%, bradygastria 5.0 +/- 1.1%, and tachygastria 16.4 +/- 3.7%. Caloric stimulation with warm water in the unilateral ear and cold water in the contralateral ear elicited vestibuloautonomic symptoms, with accompanied decreases in normogastria (57.7 +/-4.6%, P < 0.01) and increases in tachygastria (34.8 +/- 4.8%, P < 0.01). Cathodal stimulation to the mastoid process ipsilateral to cold water irrigation during caloric stimulation restored normal pattern of gastric motility: normogastria in 77.1 + 5.3% and tachygastria in 19.3 +/- 4.7%, and relieved vestibuloautonomic symptoms. Cathodal stimulation to the inhibited vestibular system ameliorates the vestibular symptoms induced by caloric stimulation.
- Published
- 1999
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38. Inflammatory pseudotumor of the liver in patients with recurrent pyogenic cholangitis: CT-histopathologic correlation.
- Author
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Yoon KH, Ha HK, Lee JS, Suh JH, Kim MH, Kim PN, Lee MG, Yun KJ, Choi SC, Nah YH, Kim CG, Won JJ, and Auh YH
- Subjects
- Adult, Aged, Cholangitis complications, Female, Granuloma, Plasma Cell complications, Humans, Liver Diseases complications, Male, Middle Aged, Recurrence, Suppuration, Cholangitis diagnostic imaging, Cholangitis pathology, Granuloma, Plasma Cell diagnostic imaging, Granuloma, Plasma Cell pathology, Liver Diseases diagnostic imaging, Liver Diseases pathology, Tomography, X-Ray Computed
- Abstract
Purpose: To correlate computed tomographic (CT) features of inflammatory pseudotumors of the liver with histopathologic results in patients with recurrent pyogenic cholangitis., Materials and Methods: CT features of 13 cases of inflammatory hepatic pseudotumor in 10 patients with recurrent pyogenic cholangitis were reviewed. Diagnosis was made by means of surgical resection in all patients. CT scans were analyzed for the appearance of masses and ancillary findings in correlation with the histopathologic findings in each resected specimen., Results: The masses were 2.0-7.0 cm (mean, 3.5 cm). At nonenhanced CT, the masses appeared as ill-defined, hypoattenuating lesions. At contrast material-enhanced CT, the masses exhibited central hypoattenuating areas with an iso- or hyperattenuating thickened periphery in four cases and a multiseptate appearance with hyperattenuating internal septa and periphery in nine cases. CT-histopathologic correlation showed that the central hypoattenuating area indicated the presence of chronic inflammatory infiltrates with foamy histiocytes, plasmacytes, and lymphocytes, while iso- or hyperattenuating areas in the periphery and internal septa of the mass represented fibroblastic proliferation. All patients had CT features of recurrent pyogenic cholangitis, such as hepatolithiasis, intrahepatic duct stricture and dilatation, common bile duct calculi, pneumobilia, or parenchymal atrophy., Conclusion: Although CT features are not specific, inflammatory pseudotumor should be included in the differential diagnosis in patients with recurrent pyogenic cholangitis and a hepatic mass detected at CT.
- Published
- 1999
- Full Text
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39. Percutaneous endoscopic gastrostomy for enteral nutrition.
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Nah YH, Chae SI, Song JH, Choi IT, Kim HJ, Park S, and Cho WS
- Subjects
- Adolescent, Adult, Aged, Enteral Nutrition adverse effects, Enteral Nutrition instrumentation, Evaluation Studies as Topic, Gastrostomy adverse effects, Gastrostomy instrumentation, Humans, Middle Aged, Enteral Nutrition methods, Gastrostomy methods
- Published
- 1987
- Full Text
- View/download PDF
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