37 results
Monte Carlo Simulation of the Total Radial Distribution Function for Interlayer Water in Sodium and Potassium Montmorillonites
- Garrison Sposito, Sung-Ho Park, Rebecca Sutton
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- Journal:
- Clays and Clay Minerals / Volume 47 / Issue 2 / April 1999
- Published online by Cambridge University Press:
- 28 February 2024, pp. 192-200
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Monte Carlo simulations based on tested water-water, cation-water, and water-clay potential functions were applied to calculate radial distribution functions for O-O, O-H and H-H spatial correlations in the interlayer region of the two-layer hydrates of Na- and K-montmorillonite. The simulated radial distribution functions then were used to compute the total radial distribution function for interlayer water, a physical quantity that can be determined experimentally by H/D isotopic-difference neutron diffraction. The simulated total radial distribution functions were compared with that for bulk liquid water, and with a total radial distribution function determined experimentally for the two-layer hydrate of Na-montmorillonite by Powell et al. (1997). This comparison suggested that water molecules in the two-layer hydrate of montmorillonite have nearest-neighbor configurations which differ significantly from the tetrahedral ordering of nearest neighbors that characterizes bulk liquid water.
The Tax Models in Japan and Korea: Concepts and Evidence from a Comparative Perspective
- Sung Ho Park
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- Journal:
- Journal of East Asian Studies / Volume 22 / Issue 3 / November 2022
- Published online by Cambridge University Press:
- 11 August 2022, pp. 359-389
- Print publication:
- November 2022
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Existing studies have relied on the notion of developmentalism to explain key aspects of the tax policies in Japan and Korea. However, limited efforts have been made to explore these cases from a comparative perspective based on relevant evidence. Far fewer studies have been conducted for examining the contemporary evolution of the tax policies following major reforms since the 1990s. This article seeks to fill these gaps in the research. Employing an analytic framework of tax structure, it provides key definitions of the old and new tax models in Japan and Korea in a way that is comparable with other OECD cases. “Residualism” and “constrained activism,” two heuristic models drawn from low-tax OECD countries, provide useful references for this comparative task. To validate key assessments, the author utilizes and replicates extensive tax data that operationalize important aspects of the tax structure from the 1980s to 2018.
Association between serum vitamin D and depressive symptoms in apparently healthy male adults undergoing routine health check-ups at a single centre
- Sung Hoon Kim, Hae Jeong Lee, Chang Ho Chae, Seung Hyun Park, Jun Seok Son
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- Journal:
- Public Health Nutrition / Volume 23 / Issue 14 / October 2020
- Published online by Cambridge University Press:
- 02 June 2020, pp. 2530-2538
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Objective:
To determine the level of vitamin D and to identify the association between vitamin D and depressive symptoms in apparently healthy Korean male adults.
Design:A retrospective study design. Among 43 513 participants between 1 March and 30 November 2018, after eliminating participants with a history of depression or vitamin D deficiency, 9058 were included. To determine the level of vitamin D, serum 25-hydroxyvitamin D [25(OH)D] was measured. To assess the level of depression, the Korean version of the Center for Epidemiologic Studies Depression Scale (CES-D) was used.
Setting:South Korea.
Participants:Male adults who underwent routine health check-ups.
Results:The average vitamin D level was 22·31 ± 7·09 ng/ml as 25(OH)D, while the number of subjects in the vitamin D insufficiency group with a finding of <20 ng/ml was 3783 (41·8 %). The mean CES-D score in all subjects was 8·31 ± 5·97 points, and the proportion of the depressive symptoms group with a score of ≥16 was 8·71 %. The OR of patients in the depressive symptoms group also being in the insufficiency group was found to be 1·49 (95 % CI 1·12, 2·00).
Conclusions:A total of 41·8 % of apparently healthy male adults had vitamin D levels <20 ng/ml. We identified an association between vitamin D insufficiency and depressive symptoms in apparently healthy Korean male adults.
Between government unilateralism and corporatist bargaining: public sector pension reforms in the UK and Ireland, 2000s–2010s
- Sung Ho Park
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- Japanese Journal of Political Science / Volume 20 / Issue 2 / June 2019
- Published online by Cambridge University Press:
- 22 April 2019, pp. 107-124
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Studies on welfare reform in advanced European countries have identified two established paths to welfare retrenchment: government unilateralism and corporatist bargaining. This study explores a more complicated path to welfare reform, wherein governments pursue ‘non-corporatist’ bargaining by actively combining features of unilateralism and negotiation. Such a hybrid case is explained by employing an ‘insider-outsider’ framework for public policy reform. The key argument is that the presence of exclusive insiders complicates the reform process, disqualifying both unilateralism and corporatist bargaining as feasible options for benefit cuts. The author demonstrates the validity of this claim by examining three cases of public sector pension retrenchment in the UK and Ireland during the 2000s and 2010s. Defying the common expectation that benefit cuts in residual welfare states would be promoted with government unilateralism, the public sector pension reforms in the UK and Ireland exhibited more complicated features which combined governments' unilateral initiatives and ad hoc negotiations with public sector unions. Future studies may build on this finding to examine hybrid reform cases in a general European context.
Prediction of post-stroke dementia using NINDS-CSN 5-minute neuropsychology protocol in acute stroke
- Jae-Sung Lim, Mi Sun Oh, Ju-Hun Lee, San Jung, Chulho Kim, Min Uk Jang, Sang-Hwa Lee, Yeo Jin Kim, Yerim Kim, Jaeseol Park, Yeonwook Kang, Kyung-Ho Yu, Byung-Chul Lee
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- International Psychogeriatrics / Volume 29 / Issue 5 / May 2017
- Published online by Cambridge University Press:
- 25 January 2017, pp. 777-784
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Background:
The National Institute of Neurological Disease and Stroke-Canadian Stroke Network (NINDS-CSN) 5-minute neuropsychology protocol consists of only verbal tasks, and is proposed as a brief screening method for vascular cognitive impairment. We evaluated its feasibility within two weeks after stroke and ability to predict the development of post-stroke dementia (PSD) at 3 months after stroke.
Method:We prospectively enrolled subjects with ischemic stroke within seven days of symptom onset who were consecutively admitted to 12 university hospitals. Neuropsychological assessments using the NINDS-CSN 5-minute and 60-minute neuropsychology protocols were administered within two weeks and at 3 months after stroke onset, respectively. PSD was diagnosed with reference to the American Heart Association/American Stroke Association statement, requiring deficits in at least two cognitive domains.
Results:Of 620 patients, 512 (82.6%) were feasible for the NINDS-CSN 5-minute protocol within two weeks after stroke. The incidence of PSD was 16.2% in 308 subjects who had completed follow-up at 3 months after stroke onset. The total score of the NINDS-CSN 5-minute protocol differed significantly between those with and without PSD (4.0 ± 2.7, 7.4 ± 2.7, respectively; p < 0.01). A cut-off value of 6/7 showed reasonable discriminative power (sensitivity 0.82, specificity 0.67, AUC 0.74). The NINDS-CSN 5-minute protocol score was a significant predictor for PSD (adjusted odds ratio 6.32, 95% CI 2.65–15.05).
Discussion:The NINDS-CSN 5-minute protocol is feasible to evaluate cognitive functions in patients with acute ischemic stroke. It might be a useful screening method for early identification of high-risk groups for PSD.
Effect of bainite in microstructure on hydrogen diffusion and trapping behavior of ferritic steel used for sour service application
- Jin Ho Park, Min-suk Oh, Sung Jin Kim
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- Journal:
- Journal of Materials Research / Volume 32 / Issue 7 / 14 April 2017
- Published online by Cambridge University Press:
- 19 December 2016, pp. 1295-1303
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- 14 April 2017
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To clarify the effect of bainite in microstructure on hydrogen diffusion and trapping behavior and susceptibility to hydrogen assisted cracking of API grade linepipe steel, three specimens with different fraction of bainite in the microstructure are used. Firstly, hydrogen diffusion and trapping behaviors of the steels are studied by utilizing the electrochemical permeation technique. For fundamental analysis on the experimental data, a variety of diffusion parameters were determined by curve-fitting with a theoretical diffusion equation based on numerical finite difference method (FDM). It indicates that the steel with higher fraction of bainite exhibits much higher sub-surface hydrogen concentration and much lower apparent hydrogen diffusivity. This behavior can be understood by the fact that the steel containing higher fraction of bainite in the microstructure has higher concentration of reversible traps and consequent larger diffusible hydrogen, leading to much slower diffusion kinetics of hydrogen atoms. Consequently, the susceptibility to hydrogen induced cracking (HIC) and sulfide stress cracking (SSC) of the steel with higher fraction of bainite increases significantly.
In-line Monitoring of Grain Size Distribution of Channel Poly Si used in 3D NAND Flash Memory Devices using Multiwavelength Raman Spectroscopy
- Noh Yeal Kwak, Chul Young Ham, Min Sung Ko, Sung Chul Shin, Seung Jin Yeom, Chul Woo Park, Chun Ho Kang, Byung Seok Lee, Sung Gi Park, Noh Jung Kwak, Woo Sik Yoo
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- Journal:
- MRS Advances / Volume 1 / Issue 5 / 2016
- Published online by Cambridge University Press:
- 18 January 2016, pp. 339-348
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- 2016
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Feasibility of multiwavelength Raman spectroscopy was studied as a potential in-line monitoring technique for grain size distribution in channel poly-Si used in three dimensional stacked NAND (3D NAND) Flash memory devices. Various channel poly-Si materials in 3D-NAND Flash memory devices, converted from chemical vapor deposition (CVD) grown a-Si, were characterized using non-contact, multiwavelength Raman spectroscopy and high resolution cross-sectional transmission electron microscopy (HRXTEM). The Raman characterization results were compared with HRXTEM images. The correlation between the grain size distribution characterized by multiwavelength Raman spectroscopy and “on current” (ION) of 3D NAND Flash memory devices was investigated. Good correlation between these techniques was seen. Multiwavelength Raman spectroscopy is very promising as a non-destructive in-line monitoring technique for grain size distribution in channel poly-Si used in 3D NAND Flash memory devices.
Effect of pain control in suspected acute appendicitis on the diagnostic accuracy of surgical residents
- KyeongWon Kang, Woo Jeong Kim, Kyuseok Kim, You Hwan Jo, Joong Eui Rhee, Jin Hee Lee, Yu-jin Kim, JaeHuk Lee, Sung-Bum Kang, Duck-Woo Kim, Kyung-Ho Lee, Young Hoon Kim, Hyun Mi Park
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- Journal:
- Canadian Journal of Emergency Medicine / Volume 17 / Issue 1 / January 2015
- Published online by Cambridge University Press:
- 11 February 2015, pp. 54-61
- Print publication:
- January 2015
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Objective
To determine the influence of early pain relief for patients with suspected appendicitis on the diagnostic performance of surgical residents.
MethodsA prospective randomized, double-blind, placebo-controlled trial was conducted for patients with suspected appendicitis. The patients were randomized to receive placebo (normal saline intravenous [IV]) infusions over 5 minutes or the study drug (morphine 5 mg IV). All of the clinical evaluations by surgical residents were performed 30 minutes after administration of the study drug or placebo. After obtaining the clinical probability of appendicitis, as determined by the surgical residents, abdominal computed tomography was performed. The primary objective was to compare the influence of IV morphine on the ability of surgical residents to diagnose appendicitis.
ResultsA total of 213 patients with suspected appendicitis were enrolled. Of these patients, 107 patients received morphine, and 106 patients received placebo saline. The negative appendectomy percentages in each group were similar (3.8% in the placebo group and 3.2% in the pain control group, p=0.62). The perforation rates in each group were also similar (18.9% in the placebo group and 14.3% in the pain control group, p=0.75). Receiver operating characteristic analysis revealed that the overall diagnostic accuracy in each group was similar (the area under the curve of the placebo group and the pain control group was 0.63 v. 0.61, respectively, p=0.81).
ConclusionsEarly pain control in patients with suspected appendicitis does not affect the diagnostic performance of surgical residents.
Serially Changing Metronidazole-Induced Encephalopathy
- Sung-Min Kim, Hyung-Woo Shin, Hyun Jeong Han, Jong-Ho Park
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- Canadian Journal of Neurological Sciences / Volume 38 / Issue 6 / November 2011
- Published online by Cambridge University Press:
- 02 December 2014, pp. 921-924
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Awareness of putative risk factors for Alzheimer’s disease among elderly Koreans
- Moon Ho Park, Sangmee Ahn Jo, Inho Jo, Eunkyung Kim, Eun Kyung Woo, Sung-Soo Kim, Su-Yong Eun, Changsu Han, Min Kyu Park
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- Acta Neuropsychiatrica / Volume 20 / Issue 1 / February 2008
- Published online by Cambridge University Press:
- 24 June 2014, pp. 20-24
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Objective:
Although there are rapidly growing concerns about the high rates of cognitive dysfunction in Korea, the knowledge of risk factors for Alzheimer’s disease (AD) among the general public in Korea remains to be elucidated.
Methods:A total of 2767 randomly selected subjects from the Ansan Geriatric Study were questioned on their knowledge of putative risk factors for AD. Their answers were compared with their sociodemographic data and other variables.
Results:The most common stated risk factor was being older (59.6%), followed by head trauma (33.6%) and cerebrovascular disease (30.4%). However, a substandard education, which is a known risk factor, was considered significant by only 9.5% of the subjects. Predictors for a worse knowledge of the risk factors for AD were being older, a lower level of education, lower economic status and the attitude that dementia is not curable.
Conclusion:This study revealed that misunderstanding about AD is more prevalent in older subjects and those with a lower level of education, and so public health education on the basic concepts of AD should be targeted at this population.
Blood lead level modifies the association between dietary antioxidants and oxidative stress in an urban adult population
- Yun-Chul Hong, Se-Young Oh, Sung-Ok Kwon, Min-Seon Park, Ho Kim, Jong-Han Leem, Eun-Hee Ha
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- Journal:
- British Journal of Nutrition / Volume 109 / Issue 1 / 14 January 2013
- Published online by Cambridge University Press:
- 02 April 2012, pp. 148-154
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- 14 January 2013
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Oxidative stress may be affected by lead exposure as well as antioxidants, yet little is known about the interaction between dietary antioxidants and blood lead levels (BLL) on oxidative stress level. We investigated the interaction between dietary antioxidants and BLL on oxidative stress level. As part of the Biomarker Monitoring for Environmental Health conducted in Seoul and Incheon, Korea, between April and December 2005, we analysed data from 683 adults (female = 47·4 %, mean age 51·4 (sd 8·4) years) who had complete measures on BLL, dietary intakes and oxidative stress marker (urinary 8-hydroxy-2′-deoxyguanosine (8-OHdG)). Dietary intakes were assessed by a validated semi-quantitative FFQ, BLL was measured using atomic absorption spectrophotometry, and 8-OHdG by ELISA. Multivariate linear regression analyses were used to evaluate the influence of BLL on the association between dietary antioxidants and 8-OHdG. Geometric means of BLL and 8-OHdG concentrations were 4·1 (sd 1·5) μg/dl and 5·4 (sd 1·9) μg/g creatinine, respectively. Increases of vitamins C and E were significantly associated with the decrease of log10 8-OHdG in the adults from the lowest quartile of the BLL group ( ≤ 3·18 μg/dl, geometric mean = 2·36 μg/dl) than those of the highest quartile BLL group (>5·36 μg/dl, geometric mean = 6·78 μg/dl). Regarding antioxidant-related foods, vegetables excluding kimchi showed a higher inverse relationship with 8-OHdG in the lowest quartile BLL group than the highest group. These findings suggest a rationale for lowering the BLL and increasing the intake of dietary antioxidants in the urban population in Korea.
Healthy Twin: A Twin-Family Study of Korea — Protocols and Current Status
- Joohon Sung, Sung-Il Cho, Kayoung Lee, Mina Ha, Eun-Young Choi, Ji-Sook Choi, Ho Kim, Jihae Kim, Kyoung Sue Hong, Yeonju Kim, Keun-Young Yoo, Chan Park, Yun-Mi Song
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- Journal:
- Twin Research and Human Genetics / Volume 9 / Issue 6 / 01 December 2006
- Published online by Cambridge University Press:
- 21 February 2012, pp. 844-848
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‘Healthy Twin’ is a twin family study extension of the existing Korean Twin-Family Register. Healthy Twin recruits adult like-sex twins over the age of 30 and their adult family members. Healthy Twin protocols are primarily tailored to the study of the quantitative trait loci of complex traits as well as to the role of environment in the etiology of complex diseases. A full-length survey is underway, including questionnaires, health examinations and the collection of biological specimens. So far, 820 individuals (169 twin pairs and their families) have participated in the survey and 1068 individual twins (608 twin pairs) have replied to the mailed zygosity questionnaire as of July 2006. The first phase (2005–2006) of Healthy Twin will recruit 1550 individuals (including about 380 twin pairs), and the second phase a proposed 1500 to 2500 additional participants. We report study protocols and zygosity and the distribution of family size of the study participants.
The Korean Twin Registry — Methods, Current Stage, and Interim Results
- Joohon Sung, Soo-Hun Cho, Sung-Il Cho, David L. Duffy, Jin-Hee Kim, Ho Kim, Kyung Sook Park, Sue Kyung Park
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- Twin Research / Volume 5 / Issue 5 / 01 October 2002
- Published online by Cambridge University Press:
- 21 February 2012, pp. 394-400
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The Korean Twin Registry is the first nationwide twin study in Korea. We compiled 154,783 twin pairs from existing nationwide data sources, mainly from address and national health insurance data. The coverage of this registry was almost complete for the twins born since 1970, but less complete as age increased, so that there were only 990 pairs who were born before 1930. The twins' health examination (N = 54,390 persons) and questionnaire (N = 44,546 persons) results were incorporated into the registry, yielding 12,894 and 9074 concordantly informative pairs. Morbidity and mortality outcomes have been followed up since 1990, for most diseases. For preliminary analysis of complex diseases, we selected ventricular septal defects (VSD) in young twins, stomach and colorectal cancers in adult twins. We identified 353 VSDs, 284 stomach cancers, and 116 colorectal cancers among twins. The prevalence rates of cancers, but not that of VSD, were lower in twins than those in population. The difference in the cancer prevalence was marked for twins born before 1926, implying some degree of selection. Like-sex (LS) twins showed familial recurrence risks (λLS) of 41.2 for VSD and 22.4 for colorectal cancers, and 1.74 for stomach cancers. For opposite-sex (OS) twins, we could estimate λOS of 19.8 for VSD only. These results were compatible with previous studies for VSD and colorectal cancers, but not for stomach cancers. Despite the strength in size, availability of health outcomes, and some lifestyle and basic laboratory data, we need accurate zygosity information to improve the validity of the results.
Interactive influences of demographics on the Mini-Mental State Examination (MMSE) and the demographics-adjusted norms for MMSE in elderly Koreans
- Jeong Lan Kim, Joon Hyuk Park, Bong Jo Kim, Moon Doo Kim, Shin-Kyum Kim, Yeon Kyung Chi, Tae Hui Kim, Seok Woo Moon, Moon Ho Park, Jae Nam Bae, Jong Inn Woo, Seung-Ho Ryu, Jong Chul Yoon, Nam-Jin Lee, Dong Young Lee, Dong Woo Lee, Seok Bum Lee, Jung Jae Lee, Chang-Uk Lee, Sung Man Chang, Ji Won Han, Jin Hyeong Jhoo, Changsu Han, Maeng Je Cho, Ki Woong Kim
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- International Psychogeriatrics / Volume 24 / Issue 4 / April 2012
- Published online by Cambridge University Press:
- 14 December 2011, pp. 642-650
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Background: The influences of demographics, culture, language, and environmental changes on Mini-Mental State Examination (MMSE) scores are considerable.
Methods: Using a sample of 7452 healthy, community-dwelling elderly Koreans, aged 55 to 94 years, who participated in the four ongoing geriatric cohorts in Korea, we investigated demographic influences on MMSE scores and derived normative data for this population. Geropsychiatrists strictly excluded subjects with cognitive disorders according to the protocol of the Korean version of the Consortium to Establish a Registry for Alzheimer's Disease Assessment Packet (CERAD-K) Clinical Assessment Battery (CERAD-K-C).
Results: Education (standardized β = 0.463), age (standardized β = −0.303), and gender (standardized β = −0.057) had significant effects on MMSE scores (p < 0.001). The score of MMSE increase 0.379 point per 1-year education, decrease 0.188 per 1-year older, and decrease 0.491 in women compared to men. Education explained 30.4% of the scores’ total variance, which was much larger than the variances explained by age (8.4%) or gender (0.3%). Accordingly, we present normative data for the MMSE stratified by education (0, 1–3, 4–6, 7–9, 10–12, and ≥ 13 years), age (60–69, 70–79, and 80–89 years), and gender.
Conclusions: We provide contemporary education-, age-, and gender-stratified norms for the MMSE, derived from a large, community-dwelling elderly Korean population sample, which could be useful in evaluating individual MMSE scores.
Distribution of benthic diatoms in Korean rivers and streams in relation to environmental variables
- Soon-Jin Hwang, Nan-Young Kim, Sung Ae Yoon, Baik-Ho Kim, Myung Hwan Park, Kyung-A You, Hak Young Lee, Han Soon Kim, Yong Jae Kim, Jungho Lee, Ok Min Lee, Jae Ki Shin, Eun Joo Lee, Sook Lye Jeon, Huyn Soo Joo
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- Journal:
- Annales de Limnologie - International Journal of Limnology / Volume 47 / Issue S1 / 2011
- Published online by Cambridge University Press:
- 08 July 2011, pp. S15-S33
- Print publication:
- 2011
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The diatoms are an ecologically important group of algae that have been extensively studied by ecologists and taxonomists. However, the large-scale patterns of diatom distribution and the factors underlying this distribution are largely unknown. The aims of this study were to identify the large-scale spatial patterns of benthic diatom assemblages in Korean streams and rivers, and to assess the importance of numerous environmental factors on diatom distribution. We classified 720 study sites based on diatom flora. Benthic diatoms, water chemistry, altitude, and riparian land cover and use were characterized by multivariate analyses, Monte Carlo permutation tests, and indicator species analysis. In total, we identified 531 diatom taxa. Diatom assemblages were mostly dominated by species of the genera Achnanthes, Navicula, Nitzschia, Cocconeis, Fragilaria (Synedra included), Cymbella, Gomphonema, and Melosira. Cluster analysis partitioned all 720 sites into eight groups based on diatom species composition. Canonical correspondence analysis indicated that altitude, land cover and use, current velocity, electrical conductivity, and nutrient levels explained a significant amount of the variation in the composition of assemblages of benthic diatoms. At the national scale, a downstream ecological gradient was apparent, from fast-flowing, mostly oligotrophic highland streams to slow-flowing, mostly eutrophic lowland rivers. Our data suggest that spatial factors explain some of the variation in diatom distribution. The present investigation of the spatial patterns of benthic diatoms, the ecological determinants of diatom occurrence, and the identification of diatom indicator species contributes to development of a program for assessing the biological integrity of lotic ecosystems in Korea.
Vascular risk factors and the effect of white matter lesions on extrapyramidal signs in Alzheimer's disease
- Moon Ho Park, Joo Young Min, Do-Young Kwon, Seung Hwan Lee, Hae Ri Na, Sung Tae Cho, Duk L. Na
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- Journal:
- International Psychogeriatrics / Volume 23 / Issue 5 / June 2011
- Published online by Cambridge University Press:
- 29 November 2010, pp. 780-787
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Background: Extrapyramidal signs (EPSs), which are important characteristics of Parkinson's disease (PD), occur frequently in Alzheimer's disease (AD). Although AD and PD share common clinical features such as EPSs, these diseases vary with respect to vascular risk factors. The presence of vascular risk factors increases the risk of AD; however, these factors have been known to be inversely associated with PD. We aimed to assess the effect of vascular risk factors and white matter lesions (WMLs) on EPSs in AD.
Methods: We recruited 1,187 AD patients and 333 controls with neither cognitive impairment nor EPSs. All participants underwent detailed clinical evaluations which included assessments of vascular risk factors, cognitive function, and EPSs, as well as WMLs on brain MRIs. EPS subtypes were classified into tremor-dominant, postural instability gait difficulty, or indeterminate; WMLs subtypes were classified into periventricular WML (pvWML) or deep WML (dWML).
Results: EPSs were present in 17.9% of subjects with AD and were significantly associated with vascular risk factors such as age, male gender, diabetes mellitus, and WMLs. Additionally, a multivariate logistic regression analysis showed that EPSs in AD were associated with pvWML (odds ratio (OR), 1.61–2.52), not with dWML. With respect to EPS subtypes, the majority (78.4%) of EPSs in AD were postural instability gait difficulty, which was also associated with WMLs (OR 1.84–2.41), pvWML (OR 2.09–3.14), and dWML (OR 1.83–3.42).
Conclusions: EPSs in AD are associated with selected vascular risk factors as well as WMLs.
Contributors
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- By Rose Teteki Abbey, K. C. Abraham, David Tuesday Adamo, LeRoy H. Aden, Efrain Agosto, Victor Aguilan, Gillian T. W. Ahlgren, Charanjit Kaur AjitSingh, Dorothy B E A Akoto, Giuseppe Alberigo, Daniel E. Albrecht, Ruth Albrecht, Daniel O. Aleshire, Urs Altermatt, Anand Amaladass, Michael Amaladoss, James N. Amanze, Lesley G. Anderson, Thomas C. Anderson, Victor Anderson, Hope S. Antone, María Pilar Aquino, Paula Arai, Victorio Araya Guillén, S. Wesley Ariarajah, Ellen T. Armour, Brett Gregory Armstrong, Atsuhiro Asano, Naim Stifan Ateek, Mahmoud Ayoub, John Alembillah Azumah, Mercedes L. García Bachmann, Irena Backus, J. Wayne Baker, Mieke Bal, Lewis V. Baldwin, William Barbieri, António Barbosa da Silva, David Basinger, Bolaji Olukemi Bateye, Oswald Bayer, Daniel H. Bays, Rosalie Beck, Nancy Elizabeth Bedford, Guy-Thomas Bedouelle, Chorbishop Seely Beggiani, Wolfgang Behringer, Christopher M. Bellitto, Byard Bennett, Harold V. Bennett, Teresa Berger, Miguel A. Bernad, Henley Bernard, Alan E. Bernstein, Jon L. Berquist, Johannes Beutler, Ana María Bidegain, Matthew P. Binkewicz, Jennifer Bird, Joseph Blenkinsopp, Dmytro Bondarenko, Paulo Bonfatti, Riet en Pim Bons-Storm, Jessica A. Boon, Marcus J. Borg, Mark Bosco, Peter C. Bouteneff, François Bovon, William D. Bowman, Paul S. Boyer, David Brakke, Richard E. Brantley, Marcus Braybrooke, Ian Breward, Ênio José da Costa Brito, Jewel Spears Brooker, Johannes Brosseder, Nicholas Canfield Read Brown, Robert F. Brown, Pamela K. Brubaker, Walter Brueggemann, Bishop Colin O. Buchanan, Stanley M. Burgess, Amy Nelson Burnett, J. Patout Burns, David B. Burrell, David Buttrick, James P. Byrd, Lavinia Byrne, Gerado Caetano, Marcos Caldas, Alkiviadis Calivas, William J. Callahan, Salvatore Calomino, Euan K. Cameron, William S. Campbell, Marcelo Ayres Camurça, Daniel F. Caner, Paul E. Capetz, Carlos F. Cardoza-Orlandi, Patrick W. Carey, Barbara Carvill, Hal Cauthron, Subhadra Mitra Channa, Mark D. Chapman, James H. Charlesworth, Kenneth R. Chase, Chen Zemin, Luciano Chianeque, Philip Chia Phin Yin, Francisca H. Chimhanda, Daniel Chiquete, John T. Chirban, Soobin Choi, Robert Choquette, Mita Choudhury, Gerald Christianson, John Chryssavgis, Sejong Chun, Esther Chung-Kim, Charles M. A. Clark, Elizabeth A. Clark, Sathianathan Clarke, Fred Cloud, John B. Cobb, W. Owen Cole, John A Coleman, John J. Collins, Sylvia Collins-Mayo, Paul K. Conkin, Beth A. Conklin, Sean Connolly, Demetrios J. Constantelos, Michael A. Conway, Paula M. Cooey, Austin Cooper, Michael L. Cooper-White, Pamela Cooper-White, L. William Countryman, Sérgio Coutinho, Pamela Couture, Shannon Craigo-Snell, James L. Crenshaw, David Crowner, Humberto Horacio Cucchetti, Lawrence S. Cunningham, Elizabeth Mason Currier, Emmanuel Cutrone, Mary L. Daniel, David D. Daniels, Robert Darden, Rolf Darge, Isaiah Dau, Jeffry C. Davis, Jane Dawson, Valentin Dedji, John W. de Gruchy, Paul DeHart, Wendy J. Deichmann Edwards, Miguel A. De La Torre, George E. Demacopoulos, Thomas de Mayo, Leah DeVun, Beatriz de Vasconcellos Dias, Dennis C. Dickerson, John M. Dillon, Luis Miguel Donatello, Igor Dorfmann-Lazarev, Susanna Drake, Jonathan A. Draper, N. Dreher Martin, Otto Dreydoppel, Angelyn Dries, A. J. Droge, Francis X. D'Sa, Marilyn Dunn, Nicole Wilkinson Duran, Rifaat Ebied, Mark J. Edwards, William H. Edwards, Leonard H. Ehrlich, Nancy L. Eiesland, Martin Elbel, J. Harold Ellens, Stephen Ellingson, Marvin M. Ellison, Robert Ellsberg, Jean Bethke Elshtain, Eldon Jay Epp, Peter C. Erb, Tassilo Erhardt, Maria Erling, Noel Leo Erskine, Gillian R. Evans, Virginia Fabella, Michael A. Fahey, Edward Farley, Margaret A. Farley, Wendy Farley, Robert Fastiggi, Seena Fazel, Duncan S. Ferguson, Helwar Figueroa, Paul Corby Finney, Kyriaki Karidoyanes FitzGerald, Thomas E. FitzGerald, John R. Fitzmier, Marie Therese Flanagan, Sabina Flanagan, Claude Flipo, Ronald B. 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Yee, Viktor Yelensky, Yeo Khiok-Khng, Gustav K. K. Yeung, Angela Yiu, Amos Yong, Yong Ting Jin, You Bin, Youhanna Nessim Youssef, Eliana Yunes, Robert Michael Zaller, Valarie H. Ziegler, Barbara Brown Zikmund, Joyce Ann Zimmerman, Aurora Zlotnik, Zhuo Xinping
- Edited by Daniel Patte, Vanderbilt University, Tennessee
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- The Cambridge Dictionary of Christianity
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- 05 August 2012
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- 20 September 2010, pp xi-xliv
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Source/Drain Overlap Length Dependence of VT in Thin Film Transistor on a-IGZO Channel Deposited by RF and DC Sputtering
- Dong Ho Nam, Kwang-Il Choi, Sung Soo Park, Jae Kyeong Jeong, Ga Won Lee
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- MRS Online Proceedings Library Archive / Volume 1108 / 2008
- Published online by Cambridge University Press:
- 01 February 2011, 1108-A09-13
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- 2008
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The ZnO TFTs have attracted much attention as key component for flexible displays because they can be fabricated on plastic substrates at low temperature and exhibit good electrical performance. However, the ZnO films are polycrystalline with grain boundaries even if formed at room temperature, which deteriorate the uniformity of TFT characteristics. A few research groups have reported high performance amorphous indium-gallium-zinc oxide TFTs to solve the native problem of nonuniformity of ZnO TFTs. However, there are few researches on the process parameter effects on the variation of a-IGZO TFT characteristics. In this study, we focus on the effect of the source/drain overlap length on threshold voltage(VT) of a-IZO TFTs with differentiating channel deposition method. The experimental structures for this work are bottom-gated TFTs with a-IGZO channel that were deposited by RF and DC magnetron sputtering on glass. RF and DC sputtering were carried out by magnetron power density of (1.4 W/cm2)/ (2.0 W/cm2) in Ar/O2 gas ratio of (65/35)/(72/28), and the entire gas pressure were 5.0 mTorr and 3.4 mTorr. The width/length(um/um) of device was split to 10/7,10/10,10/30,10/50. Each of the patterns has seven source/drain overlap length: -3um,-2um,-1um,0um,1um,2um,3um. We extracted VT of RF and DC through the VG-ID curve. There are significant VT difference in both RF and DC according to the overlap length: VT of DC(RF) is 1.31(0.74)V at W/L=10/50 and 10.21(5.74)V at W/L=10/30. VT increases definitely where less than 1um overlap length and short channel TFT is more influenced by overlap length, which is more severe in RF group. We calculated total channel resistance (RT) from VD-ID curve. RT of devices with the positive overlap can be expressed by RT, Postive=Rch+Rc. Here, Rch is net channel resistance which becomes smaller when channel length decreases and Rc is contact resistance. RT with negative overlap, is RT, Negative=Rch+Rc+Roffset. Roffset is offset resistance formed by negative overlap and can be extracted by subtracting RT, Postive from total RT, Negative. The RT of DC(RF) at offset channel length of-1um,-2um,and-3um is 4.43105(2.7 106)cm, 1.17 106(3.48 106)cm, and 1.46 106(4.73 106)cm, respectively(W/L=10/10um) RF group which shows inferior electrical characteristics such as lower mobility and larger subthreshold slope to DC, have larger Roffset than the DC. This implies that the devices require a bit of positive source/drain overlap length for uniform VT especially when the channel resistance is high. But Overlap region causes difficulties in the device area to be miniaturized. In summary, as the source/drain overlap length decreases to negative value, the threshold voltage of a-IGZO TFTs increases sharply and these tendency strongly depends on a-IZO film quality, which means the overlap length is very important control parameter of a-IGZO TFTs for the uniform threshold voltage especially when the channel resistance is high
Device Performance and Reliability Characterization of Interface and Bulk Effect in Amorphous Indium Gallium Zinc Oxide (a-IGZO) Thin Film Transistor
- Kwang-Il Choi, Dong Ho Nam, Sung Soo Park, Jae Kyeong Jeong, Ga Won Lee
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- Journal:
- MRS Online Proceedings Library Archive / Volume 1108 / 2008
- Published online by Cambridge University Press:
- 01 February 2011, 1108-A09-12
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- 2008
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a-IGZO TFT is a promising candidate device for an alternative to poly-Si TFTs or a-Si TFTs, because they provide better uniformity in terms of their important device parameters, including the threshold voltage and mobility due to their amorphous phase, and a high mobility (>10 cm2/Vs) is attainable with these devices even in the amorphous phase. Recently, a-IGZO TFTs have been extensively studied by various groups. However, there is little report on interface and bulk effect on device performances and reliability as separately. For investigating the interface and bulk effect, we fabricated two a-IGZO thin film transistors with different channel deposition conditions, RF and DC magnetron sputtering. Specific conditions of RF and DC sputtering are described as follows; magnetron power density of 1.4 W/cm2/2.0 W/cm2 in Ar/O2 gas ratio of (65/35)/(72/28), and the entire gas pressure was 5.0 mTorr and 3.4 mTorr, respectively.In order to characterize the channel quality, C-V curve was measured with various frequencies of (10KHz˜1MHz). RF sputtered channel has higher frequency dependency compared to DC sputtered channel. It means that RF sputtered channel has higher bulk traps in channel compared to DC sputtered channel.
Device performance was characterized through the ID-VG measurement. Electrical parameters of RF and DC sputtered devices are VT=3.5/2.7V, on-off ratio=105/08, SS=2/0.4 V/decade, and uFE= 5/11 cm2/V-s, respectively. It is thus clear that the device performance of DC sputtered device is more superior to RF sputtered device. Therefore, it can be said that the poor device performance of RF device is ascribed to insufficient channel quality, as mentioned in C-V curve.
For reliability study, we measured PBTI and ID-VG hysteresis with normalized gate stress bias and high temperature hot chuck system. Through the unchanged field effect mobility during the stress and relaxation time, and nearly recovered VT and subthreshold slope (SS) after long relaxation time, we were able to know that pre-existed trap was main factor of reliability degradation. Moreover, SS degradation during stress time is more severe in RF device than DC device. It is also proving that RF channel characteristic is worse than DC channel. In high temperature, leakage current increments of RF device were more severe than DC device. This also indicates that bulk traps of RF device in channel region are larger than that of DC device. VT shift of DC sputtered device for PBT stress and hysteresis was higher than that of RF sputtered device. As well known, PBTI is closely related to insulator bulk traps, which shows that channel deposition conditions affect insulator trap characteristics. In summary, device performance of a-IGZO deposited by DC sputtering is better than RF sputtering, which is because DC sputtering improves channel quality of a-IGZO. However, VT shift of DC sputtered device are worse than RF sputtering, which may be related with high magnetron power density.
Process Optimization of Ni Nanocrystals Formation Using O2 Plasma Oxidation to Fabricate Low-molecular Organic Nonvolatile Memory
- Woo Sik Nam, Gon-Sub Lee, Sung Ho Seo, Jea Gun Park
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- MRS Online Proceedings Library Archive / Volume 1071 / 2008
- Published online by Cambridge University Press:
- 01 February 2011, 1071-F05-21
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- 2008
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We fabricated organic nonvolatile memory with a device structure of Al/Alq3 (aluminum tris (8-hydroxyquinoline))/Ni nanocrystals surrounded by NiO/Alq3/Al. We obtained the best bistable switching characteristics at a 30-nm Alq3 thickness, 0.1-Å/sec evaporation rate, and 10-nm Ni nanocrystal layer thickness. The electrical behavior of the bistable switching devices was obtained by sweeping the voltage from 0 to 10 V. Our devices showed excellent bistable memory characteristics, such as a Vth of 2 V, Vp of 3 V, Ve of 5 V, and Ion/Ioff ratio of greater than 104. We found that a region of negative differential resistance exists between Vp and Ve.