1
|
Park BJ, Yoon YB, Park SC, Shin GS, Kwak HJ, Lee DH, Choi MY, Kim JW, Cho SJ. Multiple toll-like receptors (TLRs) display differential bacterial and ligand specificity in the earthworm, Eisenia andrei. J Invertebr Pathol 2023; 201:108010. [PMID: 37865158 DOI: 10.1016/j.jip.2023.108010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Revised: 10/12/2023] [Accepted: 10/17/2023] [Indexed: 10/23/2023]
Abstract
Toll-like receptors (TLRs), an ancient and well-conserved group of pattern recognition receptors (PRRs), recognize conserved pathogen-associated molecular patterns. TLRs consist of three domains: the extracellular N-terminal domain, containing one or more leucine-rich repeats (LRRs), responsible for the recognizing and binding of antigens; the type-I transmembrane domain; and the intracellular domain known as the Toll/Interleukin-1 receptor (TIR) domain required for the downstream signaling pathway. We identified six new full-length complementary DNA (cDNA) sequences, Ean-TLR1/2/3/4/5/6. The deduced amino acid sequences indicate that Ean-TLRs consist of one signal peptide, one LRR N-terminal domain (Ean-TLR4/5), varying numbers of LRRs, one (Ean-TLR1/2/3/4/5) or two (Ean-TLR6) LRR C-terminal domains, one type-I transmembrane domain, and a TIR domain. In addition, a TIR domain alignment revealed that three conserved motifs, designated as Box 1, Box 2, and Box 3, contain essential amino acid residues for downstream signaling activity. Phylogenetic analysis of earthworm TLRs generated two separate evolutionary branches representing single (sccTLR) and multiple (mccTLR) cysteine cluster TLRs. Ean-TLR1/2/3/4 (sccTLR type) and Ean-TLR6 (mccTLR type) were clustered with corresponding types of previously reported earthworm TLRs as well as TLRs from Clitellata and Polychaete. As PRRs, earthworm TLRs should be capable of sensing a diverse range of pathogens. Except for Ean-TLR3, which was not responsive to any bacteria, earthworm TLR expression was significantly induced by Gram-positive but not Gram-negative bacteria. Moreover, it is likely that earthworms can differentiate between different species of Gram-positive bacteria via their TLR responses. The ligand specificity of earthworm TLRs suggests that their pathogenic ligand recognition is likely to be as specific and diverse as the mammalian TLR pathogen-sensing system.
Collapse
Affiliation(s)
- Beom Jun Park
- Department of Life Science, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Yoo Bin Yoon
- Department of Life Science, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Soon Cheol Park
- Department of Life Science, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Geun-Seup Shin
- Department of Life Science, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Hee-Jin Kwak
- Department of Ecology, Evolution and Behavior, Alexander Silberman Institute of Life Sciences, Faculty of Science, Hebrew University of Jerusalem, Jerusalem, 9190401, Israel
| | - Dong Ho Lee
- College of General Education, Chung-Ang University, Seoul, 06974, Republic of Korea
| | - Min Young Choi
- Department of Biological Sciences and Biotechnology, Chungbuk National University, Chungbuk 28644, Republic of Korea
| | - Jung-Woong Kim
- Department of Life Science, Chung-Ang University, Seoul 06974, Republic of Korea.
| | - Sung-Jin Cho
- Department of Biological Sciences and Biotechnology, Chungbuk National University, Chungbuk 28644, Republic of Korea.
| |
Collapse
|
2
|
Barraclough ML, Diaz-Martinez JP, Knight A, Bingham K, Su J, Kakvan M, Grajales CM, Tartaglia MC, Ruttan L, Wither J, Choi MY, Bonilla D, Anderson N, Appenzeller S, Parker B, Katz P, Beaton D, Green R, Bruce IN, Touma Z. In-person versus virtual administration of the American College of Radiology gold standard cognitive battery in systemic lupus erythematosus: Are they interchangeable? Lupus 2023; 32:737-745. [PMID: 37036020 DOI: 10.1177/09612033231168477] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
Abstract
OBJECTIVE During the COVID-19 pandemic, many research studies were adapted, including our longitudinal study examining cognitive impairment (CI) in systemic lupus erythematosus (SLE). Cognitive testing was switched from in-person to virtual. This analysis aimed to determine if the administration method (in-person vs. virtual) of the ACR-neuropsychological battery (ACR-NB) affected participant cognitive performance and classification. METHODS Data from our multi-visit, SLE CI study included demographic, clinical, and psychiatric characteristics, and the modified ACR-NB. Three analyses were undertaken for cognitive performance: (1) all visits, (2) non-CI group visits only and (3) intra-individual comparisons. A retrospective preferences questionnaire was given to participants who completed the ACR-NB both in-person and virtually. RESULTS We analysed 328 SLE participants who had 801 visits (696 in-person and 105 virtual). Demographic, clinical, and psychiatric characteristics were comparable except for ethnicity, anxiety and disease-related damage. Across all three comparisons, six tests were consistently statistically significantly different. CI classification changed in 11/71 (15%) participants. 45% of participants preferred the virtual administration method and 33% preferred in-person. CONCLUSIONS Of the 19 tests in the ACR-NB, we identified one or more problems with eight (42%) tests when moving from in-person to virtual administration. As the use of virtual cognitive testing will likely increase, these issues need to be addressed - potentially by validating a virtual version of the ACR-NB. Until then, caution must be taken when directly comparing virtual to in-person test results. If future studies use a mixed administration approach, this should be accounted for during analysis.
Collapse
Affiliation(s)
- M L Barraclough
- Schroeder Arthritis Institute, Krembil Research Institute, 7989University Health Network, Toronto, ON, Canada
- Centre for Epidemiology Versus Arthritis, Division of Musculoskeletal and Dermatological Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, 5292The University of Manchester, Manchester, UK
- NIHR Manchester Biomedical Research Centre, Manchester Academic Health Science Centre, Manchester University NHS Foundation Trust, Manchester, UK
| | - J P Diaz-Martinez
- Schroeder Arthritis Institute, Krembil Research Institute, 7989University Health Network, Toronto, ON, Canada
- Centre for Prognosis Studies in Rheumatic Diseases, Toronto Western Hospital, 7938University of Toronto Lupus Clinic, Toronto, ON, Canada
| | - A Knight
- Division of Rheumatology, 7979Hospital for Sick Children, Toronto, ON, Canada
- Neurosciences and Mental Health Program, SickKids Research Institute, Toronto, ON, Canada
| | - K Bingham
- Centre for Mental Health, 7989University Health Network, Toronto, ON, Canada
- Department of Psychiatry, 7938University of Toronto, Toronto, ON, Canada
| | - J Su
- Schroeder Arthritis Institute, Krembil Research Institute, 7989University Health Network, Toronto, ON, Canada
- Division of Rheumatology, 7979Hospital for Sick Children, Toronto, ON, Canada
| | - M Kakvan
- Schroeder Arthritis Institute, Krembil Research Institute, 7989University Health Network, Toronto, ON, Canada
- Centre for Prognosis Studies in Rheumatic Diseases, Toronto Western Hospital, 7938University of Toronto Lupus Clinic, Toronto, ON, Canada
| | - C Muñoz Grajales
- Schroeder Arthritis Institute, Krembil Research Institute, 7989University Health Network, Toronto, ON, Canada
- Centre for Prognosis Studies in Rheumatic Diseases, Toronto Western Hospital, 7938University of Toronto Lupus Clinic, Toronto, ON, Canada
| | - M C Tartaglia
- Krembil Research Institute, 7989University Health Network Memory Clinic, Toronto, ON, Canada
| | - L Ruttan
- 7961University Health Network-Toronto Rehabilitation Institute, Toronto, ON, Canada
| | - J Wither
- Schroeder Arthritis Institute, Krembil Research Institute, 7989University Health Network, Toronto, ON, Canada
| | - M Y Choi
- Cumming School of Medicine, 70401University of Calgary, Calgary, AB, Canada
| | - D Bonilla
- Schroeder Arthritis Institute, Krembil Research Institute, 7989University Health Network, Toronto, ON, Canada
- Centre for Prognosis Studies in Rheumatic Diseases, Toronto Western Hospital, 7938University of Toronto Lupus Clinic, Toronto, ON, Canada
| | - N Anderson
- Schroeder Arthritis Institute, Krembil Research Institute, 7989University Health Network, Toronto, ON, Canada
- Centre for Prognosis Studies in Rheumatic Diseases, Toronto Western Hospital, 7938University of Toronto Lupus Clinic, Toronto, ON, Canada
| | - S Appenzeller
- Department of Orthopaedics, Rheumatology and Traumatology, 7938University of Campinas, São Paulo, Brazil
| | - B Parker
- Centre for Epidemiology Versus Arthritis, Division of Musculoskeletal and Dermatological Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, 5292The University of Manchester, Manchester, UK
- NIHR Manchester Biomedical Research Centre, Manchester Academic Health Science Centre, Manchester University NHS Foundation Trust, Manchester, UK
| | - P Katz
- 8785University of California, San Francisco, CA, USA
| | - D Beaton
- Institute for Work and Health, 7966University of Toronto, Toronto, ON, Canada
| | - R Green
- Krembil Research Institute, 7989University Health Network Memory Clinic, Toronto, ON, Canada
| | - I N Bruce
- Centre for Epidemiology Versus Arthritis, Division of Musculoskeletal and Dermatological Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, 5292The University of Manchester, Manchester, UK
- NIHR Manchester Biomedical Research Centre, Manchester Academic Health Science Centre, Manchester University NHS Foundation Trust, Manchester, UK
| | - Z Touma
- Schroeder Arthritis Institute, Krembil Research Institute, 7989University Health Network, Toronto, ON, Canada
- Centre for Prognosis Studies in Rheumatic Diseases, Toronto Western Hospital, 7938University of Toronto Lupus Clinic, Toronto, ON, Canada
| |
Collapse
|
3
|
Abstract
Autoantibodies (AA) and antinuclear antibodies (ANA) serve as key diagnostic and classification criteria for systemic lupus erythematosus (SLE). More than 200 different AA have been reported in SLE, although only a handful (<20) are considered "mainstream" because they are widely and routinely used in diagnostic, research and clinical medicine. Although the vast majority of AA have been relegated to the diminished status of "orphan" AA, some serve as predictors of SLE because they first appear in very early or subclinical SLE. Some AA are pathogenic, whereas others are thought to protect against or ameliorate disease progression and, hence, taken together can be used as predictive biomarkers of prognosis. Although studies have shown that specific AA are detected in the preclinical phase of SLE and are biomarkers of increased risk of developing the disease, AA are currently not widely used to predict very early SLE in individuals who have low pretest probability of disease. With the advent of multianalyte arrays with analytic algorithms, emerging evidence indicates that when certain combinations of biomarkers, such as the interferon signature and stem cell factor accompany AA and ANA, the predictive power for SLE is markedly increased.
Collapse
Affiliation(s)
- M Y Choi
- Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - M J Fritzler
- Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| |
Collapse
|
4
|
Choi MY, Barber MRW, Barber CEH, Clarke AE, Fritzler MJ. Preventing the development of SLE: identifying risk factors and proposing pathways for clinical care. Lupus 2017; 25:838-49. [PMID: 27252260 DOI: 10.1177/0961203316640367] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Although challenging, developing evidence-based approaches to an early and accurate diagnosis of systemic lupus erythematosus is a key approach to preventing disease and lupus-associated morbidity and mortality. Advances in our understanding of preclinical and incomplete lupus erythematosus have enabled the identification of risk factors that may predict disease and the development of potential strategies aimed at primary prevention. Emerging data support the notion that there is a temporal disease progression from initial asymptomatic autoimmunity (preclinical lupus) through early clinical features of the disease (incomplete lupus erythematosus) to finally becoming fully classifiable systemic lupus erythematosus (complete lupus erythematosus). Here, we review the demographic, clinical, biomarker as well as genetic and environmental features that are reported to increase the risk of disease progression. Based on these risk factors, we propose a clinical care pathway for patients with early disease. We envisage that such a pathway, through early identification of disease, may improve patient outcomes, while reducing health care costs.
Collapse
Affiliation(s)
- M Y Choi
- University of Calgary, Cumming School of Medicine, Calgary, Canada
| | - M R W Barber
- University of Calgary, Cumming School of Medicine, Calgary, Canada
| | - C E H Barber
- University of Calgary, Cumming School of Medicine, Calgary, Canada
| | - A E Clarke
- University of Calgary, Cumming School of Medicine, Calgary, Canada
| | - M J Fritzler
- University of Calgary, Cumming School of Medicine, Calgary, Canada
| |
Collapse
|
5
|
Yu J, Chen L, Cui B, Wu C, Choi MY, Chen Y, Zhang L, Rassenti LZ, Widhopf Ii GF, Kipps TJ. Cirmtuzumab inhibits Wnt5a-induced Rac1 activation in chronic lymphocytic leukemia treated with ibrutinib. Leukemia 2016; 31:1333-1339. [PMID: 27904138 PMCID: PMC5462858 DOI: 10.1038/leu.2016.368] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Revised: 10/24/2016] [Accepted: 11/04/2016] [Indexed: 12/15/2022]
Abstract
Signaling via the B cell receptor (BCR) plays an important role in the pathogenesis and progression of chronic lymphocytic leukemia (CLL). This is underscored by the clinical effectiveness of ibrutinib, an inhibitor of Bruton's tyrosine kinase (BTK) that can block BCR-signaling. However, ibrutinib cannot induce complete responses (CR) or durable remissions without continued therapy, suggesting alternative pathways also contribute to CLL growth/survival that are independent of BCR-signaling. ROR1 is a receptor for Wnt5a, which can promote activation of Rac1 to enhance CLL-cell proliferation and survival. In this study, we found that CLL cells of patients treated with ibrutinib had activated Rac1. Moreover, Wnt5a could induce Rac1 activation and enhance proliferation of CLL cells treated with ibrutinib at concentrations that were effective in completely inhibiting BTK and BCR-signaling. Wnt5a-induced Rac1 activation could be blocked by cirmtuzumab (UC-961), an anti-ROR1 mAb. We found that treatment with cirmtuzumab and ibrutinib was significantly more effective than treatment with either agent alone in clearing leukemia cells in vivo. This study indicates that cirmtuzumab may enhance the activity of ibrutinib in the treatment of patients with CLL or other ROR1+ B-cell malignancies.
Collapse
Affiliation(s)
- J Yu
- Moores Cancer Center, University of California, San Diego, La Jolla, CA 92093, USA
| | - L Chen
- Moores Cancer Center, University of California, San Diego, La Jolla, CA 92093, USA
| | - B Cui
- Moores Cancer Center, University of California, San Diego, La Jolla, CA 92093, USA
| | - Christina Wu
- Moores Cancer Center, University of California, San Diego, La Jolla, CA 92093, USA
| | - M Y Choi
- Moores Cancer Center, University of California, San Diego, La Jolla, CA 92093, USA
| | - Y Chen
- Moores Cancer Center, University of California, San Diego, La Jolla, CA 92093, USA
| | - L Zhang
- Moores Cancer Center, University of California, San Diego, La Jolla, CA 92093, USA
| | - L Z Rassenti
- Moores Cancer Center, University of California, San Diego, La Jolla, CA 92093, USA
| | - G F Widhopf Ii
- Moores Cancer Center, University of California, San Diego, La Jolla, CA 92093, USA
| | - T J Kipps
- Moores Cancer Center, University of California, San Diego, La Jolla, CA 92093, USA
| |
Collapse
|
6
|
Abstract
Human beings develop the land and transform land use patterns, constructing artificial structures. Among them, the city is a representative system and its morphology has attracted much attention. While most existing studies have been devoted to individual dynamics and focused on the proximity of specific areas of a city, we here pay attention to the city as a complex system, where interactions between individuals give rise to emergent properties. Specifically, analyzing the big data on every building in Seoul City, we specify the relevant interactions among constituents and probe the emergence of complex land use patterns. In particular, based on the empirical observations, we illustrate that interactions between land uses are frustrated, which serves as a basic postulate of the theory of urban morphology. We examine this conjecture with the help of a layered Ising-type model and disclose that the actual land use pattern emerges at the criticality of the system in the presence of heterogeneously distributed fields. It is also remarked that our model, allowing quantitative predictions, can easily be applied to other cities around the world.
Collapse
Affiliation(s)
- Segun Goh
- Department of Physics and Astronomy and Center for Theoretical Physics, Seoul National University, Seoul 151-747, Korea
| | - M Y Choi
- Department of Physics and Astronomy and Center for Theoretical Physics, Seoul National University, Seoul 151-747, Korea
| | - Keumsook Lee
- Department of Geography, Sungshin Women's University, Seoul 136-742, Korea
| | - Kyung-Min Kim
- Graduate School of Environmental Studies, Seoul National University, Seoul 151-742, Korea
| |
Collapse
|
7
|
Kim CL, Cha SY, Chun MY, Kim B, Choi MY, Cheon YP. Positive Effects of Diphlorethohydroxycarmalol (DPHC) on the Stability of the Integument Structure in Diet-Induced Obese Female Mice. Dev Reprod 2016; 19:145-52. [PMID: 27004271 PMCID: PMC4801041 DOI: 10.12717/dr.2015.19.3.145] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Diphlorethohydroxycarmalol (DPHC) is a known to modulate the expression of extracellular matrix (ECM) components in 3T3-L1. However, the possible role of DPHC in integument stability during obesity induction is not clear yet. We evaluated the effects of DPHC on collagen or elastic fiber quantity in integument during obesity induction with high-fat diet. The dorsal back integument sections were stained with hematoxylin–eosin, Masson trichrome, and Verhoff-Van Gieson. The intensities of collagen fibers and elastin fibers were analyzed with ImageJ. The number of fibroblasts was counted at ×1,000 fields. The number of fibroblast was increased by obesity induction, but DPHC suppressed it in a concentrationdependent manner both in lean and obese mice. On the other hand, the intensities of collagen fibers were increased by DPHC treatment in obese mice groups but not in lean mice groups. The intensities of collagen fibers of obese mice were lower than that of the lean mice in 0% group. However, the number became similar between lean and obese mice by the treatment of DPHC. The intensity of elastic fibers was increased in the lean mice with the concentration of DPHC. In the obese mice group, there were increasing patterns but only significant at 10% DPHC group. The intensity of elastic fibers of obese mice was higher than lean mice in 0%, 1%, and 10% groups. Histologically epithelial cells and follicle cells which were diffused nuclear staining forms were increased by DPHC treatment. The results suggest that the activity of integument cells during obesity induction can be modulated by DPHC.
Collapse
Affiliation(s)
- Chae-Lim Kim
- Division of Developmental Biology and Physiology, School of Biosciences and Chemistry, Institute for Basic Sciences, Sungshin Women's University, Seoul 142-742, Korea
| | - Sun-Yeong Cha
- Division of Developmental Biology and Physiology, School of Biosciences and Chemistry, Institute for Basic Sciences, Sungshin Women's University, Seoul 142-742, Korea
| | - Min Young Chun
- Global Medical Science, Sungshin Women's University, Seoul 142-742, Korea
| | - Bumsoo Kim
- Exercise Rehabilitation and Welfare, Sungshin Women's University, Seoul 142-742, Korea
| | - Min Young Choi
- Industrial Design, Sungshin Women's University, Seoul 142-742, Korea
| | - Yong-Pil Cheon
- Division of Developmental Biology and Physiology, School of Biosciences and Chemistry, Institute for Basic Sciences, Sungshin Women's University, Seoul 142-742, Korea
| |
Collapse
|
8
|
Jo HB, Lee JK, Choi MY, Han IW, Choi HS, Kang HW, Kim JH, Lim YJ, Koh MS, Lee JH. Is the Prevalence of Gallbladder Polyp Different between Vegetarians and General Population? Korean J Gastroenterol 2015; 66:268-73. [DOI: 10.4166/kjg.2015.66.5.268] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Hee Bum Jo
- Department of Internal Medicine, Dongguk University Ilsan Hospital, Goyang, Korea
| | - Jun Kyu Lee
- Department of Internal Medicine, Dongguk University Ilsan Hospital, Goyang, Korea
| | - Min Young Choi
- Department of Internal Medicine, Dongguk University Ilsan Hospital, Goyang, Korea
| | - In Woong Han
- Department of Surgery, Dongguk University Ilsan Hospital, Goyang, Korea
| | - Han Seok Choi
- Department of Internal Medicine, Dongguk University Ilsan Hospital, Goyang, Korea
| | - Hyoun Woo Kang
- Department of Internal Medicine, Dongguk University Ilsan Hospital, Goyang, Korea
| | - Jae Hak Kim
- Department of Internal Medicine, Dongguk University Ilsan Hospital, Goyang, Korea
| | - Yun Jeong Lim
- Department of Internal Medicine, Dongguk University Ilsan Hospital, Goyang, Korea
| | - Moon-Soo Koh
- Department of Internal Medicine, Dongguk University Ilsan Hospital, Goyang, Korea
| | - Jin Ho Lee
- Department of Internal Medicine, Dongguk University Ilsan Hospital, Goyang, Korea
| |
Collapse
|
9
|
Kwon HW, Choi MY. Generalized hydromechanical model for stomatal responses to hydraulic perturbations. J Theor Biol 2014; 340:119-30. [PMID: 24060618 DOI: 10.1016/j.jtbi.2013.09.016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2012] [Revised: 09/10/2013] [Accepted: 09/13/2013] [Indexed: 11/16/2022]
Abstract
Stomata respond in a common pattern to various hydraulic perturbations on any part of the 'soil-plant-air' system: initial transient 'wrong-way' responses and final stationary 'right-way' responses. In order to describe this pattern on the basis of statistical physics, we propose a simple model where turgor pressure of a cell is taken to be a power function of its volume, and obtain results in qualitative agreement with experimental data for responses to a variety of hydraulic perturbations: Firstly, stationary stomatal conductance as a function of the vapor pressure deficit divides into three regimes characterized by sensitivities of the stomatal conductance and the transpiration rate with respect to vapor pressure deficit; secondly, for every hydraulic perturbation, the initial transient 'wrong-way' responses always appear; thirdly, on condition that water is supplied insufficiently, stomatal oscillations are often observed; finally, stomatal responses following leaf excision exhibit, after the initial transient wrong-way responses, slow relaxation to stomatal closing. In particular, comparison of areoles having different numbers of stomata demonstrates that areoles with small numbers of stomata tend to provoke lack of water in the soil as well as in the plant. In addition, our model also describes well dependence of the stomatal conductance on temperature. It may be extended further to describe stomatal responses to other environmental factors such as carbon dioxide, light, and temperature.
Collapse
Affiliation(s)
- H W Kwon
- Department of Physics and Astronomy and Center for Theoretical Physics, Seoul National University, Seoul 151-747, Republic of Korea; School of Physics, Korea Institute for Advanced Study, Seoul 130-722, Republic of Korea
| | | |
Collapse
|
10
|
Lim SM, Chang H, Yoon MJ, Hong YK, Kim H, Chung WY, Park CS, Nam KH, Kang SW, Kim MK, Kim SB, Lee SH, Kim HG, Na II, Kim YS, Choi MY, Kim JG, Park KU, Yun HJ, Kim JH, Cho BC. A multicenter, phase II trial of everolimus in locally advanced or metastatic thyroid cancer of all histologic subtypes. Ann Oncol 2013; 24:3089-94. [PMID: 24050953 DOI: 10.1093/annonc/mdt379] [Citation(s) in RCA: 102] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Affiliation(s)
- S M Lim
- Department of Internal Medicine, Division of Medical Oncology, Yonsei University College of Medicine, Seoul
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
11
|
Kim M, Jeong D, Kwon HW, Choi MY. Information exchange dynamics of the two-dimensional XY model. Phys Rev E Stat Nonlin Soft Matter Phys 2013; 88:052134. [PMID: 24329241 DOI: 10.1103/physreve.88.052134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Revised: 10/07/2013] [Indexed: 06/03/2023]
Abstract
Information exchange dynamics of the two-dimensional XY model is studied by means of the entropic sampling algorithm. Combining the analytic and numerical results, we obtain the entropy in the whole range of the energy at various system sizes. The time evolution of the order parameter and of the number of vortices is explored, and the corresponding relaxation times are found to grow algebraically with the system size. Such absence of characteristic time scales in the thermodynamic limit manifests the emergent criticality of the exchanging process of information with the environment. The mechanism of information exchange in the XY model is discussed in terms of the dynamic exponents, in comparison with the Ising model.
Collapse
Affiliation(s)
- Minsu Kim
- Department of Physics and Astronomy and Center for Theoretical Physics, Seoul National University, Seoul 151-747, Korea and Soil and Terrestrial Environmental Physics (STEP), Institute of Terrestrial Ecosystems (ITES), ETH Zurich, 8092 Zurich, Switzerland
| | - Daun Jeong
- Computational Science Group, Samsung Advanced Institute of Technology, Yongin 446-712, Korea
| | - H W Kwon
- Department of Physics and Astronomy and Center for Theoretical Physics, Seoul National University, Seoul 151-747, Korea and School of Physics, Korea Institute for Advanced Study, Seoul 130-722, Korea
| | - M Y Choi
- Department of Physics and Astronomy and Center for Theoretical Physics, Seoul National University, Seoul 151-747, Korea
| |
Collapse
|
12
|
Choi MY, Kim BG, Kim JW, Lee KL, Jeong JB, Lee JK, Jung YJ, Kim W, Ahn DW, Kim YH, Joo SK, Chang MS, Kwon HJ. [The effects of family history of colorectal cancer on the development of colorectal adenoma]. Korean J Gastroenterol 2012; 60:36-41. [PMID: 22832798 DOI: 10.4166/kjg.2012.60.1.36] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
BACKGROUND/AIMS Early detection of polyp is important for the prevention of colorectal cancer (CRC). There have been few studies to investigate the relationship between colorectal adenoma and family history of CRC (FHCRC) in Korea. The aim of this study was to identify the relationship between colorectal adenoma and FHCRC. METHODS Between March 2009 and September 2010, 225 patients with adenomatous polyps were included. Their medical records with clinical history and size, numbers, histology of polyps were reviewed. Immunohistochemical staining using Bcl-2, Bax, p-AKT, NF-κB, and β-catenin antibodies were performed. We compared the histology of adenoma and expression of immunohistochemical staining according to the existence of FHCRC. RESULTS The incidence of colorectal adenoma increased in case of FHCRC (p=0.029). In patients with FHCRC, the mean age of patients was 49 years old and younger than patients without FHCRC. In addition in patients with FHCRC, the incidence of advanced adenoma was significantly higher than in patients without FHCRC (p=0.001). The expression of Bax was significantly lower in patients with FHCRC than without FHCRC (p=0.046). CONCLUSIONS There was a tendency for polyp to develop in their younger ages and to be more advanced adenomas in patients with FHCRC. The low expression of Bax, tumor suppressor gene, might be associated with the development of polyps in patient with FHCRC. Therefore, patients with FHCRC may be better to start screening colonoscopy earlier than patient without FHCRC.
Collapse
Affiliation(s)
- Min Young Choi
- Department of Internal Medicine, Seoul National University Boramae Hospital, Seoul 156-707, Korea
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
13
|
Goh S, Lee K, Park JS, Choi MY. Modification of the gravity model and application to the metropolitan Seoul subway system. Phys Rev E Stat Nonlin Soft Matter Phys 2012; 86:026102. [PMID: 23005820 DOI: 10.1103/physreve.86.026102] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2012] [Indexed: 06/01/2023]
Abstract
The Metropolitan Seoul Subway system is examined through the use of the gravity model. Exponents describing the power-law dependence on the time distance between stations are obtained, which reveals a universality for subway lines of the same topology. In the short (time) distance regime the number of passengers between stations does not grow with the decrease in the distance, thus deviating from the power-law behavior. It is found that such reduction in passengers is well described by the Hill function. Further, temporal fluctuations in the passenger flow data, fitted to the gravity model modified by the Hill function, are analyzed to reveal the Yule-type nature inherent in the structure of Seoul.
Collapse
Affiliation(s)
- Segun Goh
- Department of Physics and Astronomy and Center for Theoretical Physics, Seoul National University, Seoul, Korea
| | | | | | | |
Collapse
|
14
|
Choi MY, Choi DJ, Ahn KO, Ro I, Kim YH, Suh SH. Fabrication of copper nanoparticles in a thick polyimide film cured by rapid thermal annealing. J Nanosci Nanotechnol 2012; 12:3637-3640. [PMID: 22849185 DOI: 10.1166/jnn.2012.5588] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We investigated the imidization of a polyimide (PI) and the formation of Cu nanoparticles in a PI film by curinga precursor of PI (polyamic acid (PAA) dissolved in n-methyl-2-pyrrolidinone) in a reducing atmosphere in the rapid thermal annealing (RTA) system. A Cu film was deposited onto the SiO2/Si substrate, and the PAA was spin-coated onto the Cu film. After the PAA reacted with the Cu film, soft-baking was performed to evaporate the solvent. Finally, the PAA was imidized to PI at 450 degrees C by curing in a reducing atmosphere with the RTA. Fourier transform infrared spectroscopy showed that the PAA was successfully imidized by the RTA. X-ray diffraction patterns revealed that Cu nanoparticles formed by RTA curing at 450 degrees C for 5 minutes in a reducing atmosphere, and transmission electron microscopy showed that Cu nanoparticles about 6.5 nm in size were uniformly dispersed in the PI film. Curing by RTA is an attractive method because it takes only a few minutes.
Collapse
Affiliation(s)
- Min Young Choi
- Division of Materials Science and Engineering, Hanyang University Seoul, 133-791, Korea
| | | | | | | | | | | |
Collapse
|
15
|
Cheong SH, Yang YI, Choi MY, Kim MH, Cho KR, Lim SH, Lee JH, Lee KM, Moon SH. Lung injury induced by the pulmonary instillation of povidone-iodine in rats. J Anesth 2011; 26:70-9. [PMID: 21983968 DOI: 10.1007/s00540-011-1242-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2011] [Accepted: 09/16/2011] [Indexed: 11/24/2022]
Abstract
PURPOSE Povidone-iodine (polyvinylpyrrolidone iodine, PI), which is commonly used as a pre- and postoperative oral antiseptic, has been reported to cause pneumonia secondary to its pulmonary aspiration. Because no studies have yet investigated the underlying mechanisms of PI-induced pneumonia, we conducted an animal study to analyze the effect of PI on the lung following its pulmonary instillation. METHODS The lungs of 61 male Sprague-Dawley rats (150-250 g) were instilled with varying volumes of either phosphate-buffered saline or PI solutions varying in strength from 0.01% to 10%. The lungs were harvested from the rats 1 h or 1, 3, 5, 7, 14, or 21 days after instillation for radiologic examination, macroscopic and light and scanning electron microscopic assessment, and an assessment of pulmonary toxicity using an MTT-based cytotoxicity assay. RESULTS Macroscopically, atelectasis was the primary pulmonary lesion after PI instillation. The primary light and scanning electron microscopic findings were an initial inflammatory phase with edema, alveolar rupture, and leukocyte infiltration into the pulmonary interstitium, which progressed into a phase of lung parenchyma loss, and then resolved itself with scar tissue formation. Lung tissue viability following 1-day exposure to 0.01%, 0.1%, 1%, or 5% PI progressively decreased in a significant dose-dependent manner. CONCLUSIONS PI aspiration can cause lung injury, including pulmonary fibrosis.
Collapse
Affiliation(s)
- Soon Ho Cheong
- Department of Anesthesiology, Paik Hospital, Inje University, Gaegumdong, Jingu, Busan, Korea.
| | | | | | | | | | | | | | | | | |
Collapse
|
16
|
Jo J, Fortin JY, Choi MY. Weibull-type limiting distribution for replicative systems. Phys Rev E Stat Nonlin Soft Matter Phys 2011; 83:031123. [PMID: 21517470 DOI: 10.1103/physreve.83.031123] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2010] [Revised: 02/05/2011] [Indexed: 05/30/2023]
Abstract
The Weibull function is widely used to describe skew distributions observed in nature. However, the origin of this ubiquity is not always obvious to explain. In the present paper, we consider the well-known Galton-Watson branching process describing simple replicative systems. The shape of the resulting distribution, about which little has been known, is found essentially indistinguishable from the Weibull form in a wide range of the branching parameter; this can be seen from the exact series expansion for the cumulative distribution, which takes a universal form. We also find that the branching process can be mapped into a process of aggregation of clusters. In the branching and aggregation process, the number of events considered for branching and aggregation grows cumulatively in time, whereas, for the binomial distribution, an independent event occurs at each time with a given success probability.
Collapse
Affiliation(s)
- Junghyo Jo
- Laboratory of Biological Modeling, NIDDK, National Institutes of Health, Bethesda, Maryland 20892, USA
| | | | | |
Collapse
|
17
|
Goh S, Kwon HW, Choi MY, Fortin JY. Emergence of skew distributions in controlled growth processes. Phys Rev E Stat Nonlin Soft Matter Phys 2010; 82:061115. [PMID: 21230652 DOI: 10.1103/physreve.82.061115] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2010] [Indexed: 05/30/2023]
Abstract
Starting from a master equation, we derive the evolution equation for the size distribution of elements in an evolving system, where each element can grow, divide into two, and produce new elements. We then probe general solutions of the evolution equation, to obtain such skew distributions as power-law, log-normal, and Weibull distributions, depending on the growth or division and production. Specifically, repeated production of elements of uniform size leads to power-law distributions, whereas production of elements with the size distributed according to the current distribution as well as no production of new elements results in log-normal distributions. Finally, division into two, or binary fission, bears Weibull distributions. Numerical simulations are also carried out, confirming the validity of the obtained solutions.
Collapse
Affiliation(s)
- Segun Goh
- Department of Physics and Astronomy and Center for Theoretical Physics, Seoul National University, Seoul 151-747, Korea
| | | | | | | |
Collapse
|
18
|
Abstract
Vitamin D is a pleiotropic secosteroid hormone important for health and disease prevention. The actions of vitamin D are mediated by the vitamin D receptor that binds the active form of vitamin D [1,25(OH)(2)D] to induce both transcriptional and non-genomic responses. Vitamin D has well known classical functions in calcium uptake and bone metabolism, but more recent work highlights the importance of the nonclassical actions of vitamin D in a variety of cell types. These actions include modulation of the innate and adaptive immune systems and regulation of cell proliferation. Adequate vitamin D intake is essential for maternal and fetal health during pregnancy, and epidemiological data indicate that many pregnant women have sub-optimal vitamin D levels. Notably, vitamin D deficiency correlates with preeclampsia, gestational diabetes mellitus, and bacterial vaginosis, and an increased risk for C-section delivery. Recent work emphasizes the importance of nonclassical roles of vitamin D in pregnancy and the placenta. The placenta produces and responds to vitamin D where vitamin D functions as a modulator of implantation, cytokine production and the immune response to infection. We describe vitamin D metabolism and the cellular responses to vitamin D, and then summarize the role of vitamin D in placental trophoblast, pregnancy and the fetus.
Collapse
Affiliation(s)
- J S Shin
- Department of Obstetrics and Gynecology, CHA University School of Medicine, Seoul, Republic of Korea
| | | | | | | |
Collapse
|
19
|
Abstract
Vitamin D is a pleiotropic secosteroid hormone important for health and disease prevention. The actions of vitamin D are mediated by the vitamin D receptor that binds the active form of vitamin D [1,25(OH)(2)D] to induce both transcriptional and non-genomic responses. Vitamin D has well known classical functions in calcium uptake and bone metabolism, but more recent work highlights the importance of the nonclassical actions of vitamin D in a variety of cell types. These actions include modulation of the innate and adaptive immune systems and regulation of cell proliferation. Adequate vitamin D intake is essential for maternal and fetal health during pregnancy, and epidemiological data indicate that many pregnant women have sub-optimal vitamin D levels. Notably, vitamin D deficiency correlates with preeclampsia, gestational diabetes mellitus, and bacterial vaginosis, and an increased risk for C-section delivery. Recent work emphasizes the importance of nonclassical roles of vitamin D in pregnancy and the placenta. The placenta produces and responds to vitamin D where vitamin D functions as a modulator of implantation, cytokine production and the immune response to infection. We describe vitamin D metabolism and the cellular responses to vitamin D, and then summarize the role of vitamin D in placental trophoblast, pregnancy and the fetus.
Collapse
Affiliation(s)
- J S Shin
- Department of Obstetrics and Gynecology, CHA University School of Medicine, Seoul, Republic of Korea
| | | | | | | |
Collapse
|
20
|
Kwon HW, Choi MY. Comment on "Dynamical phase transition of a one-dimensional transport process including death". Phys Rev E Stat Nonlin Soft Matter Phys 2010; 82:013101. [PMID: 20866671 DOI: 10.1103/physreve.82.013101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2010] [Indexed: 05/29/2023]
Abstract
Motivated by the mycologic situation, Dorosz and collaborators considered a modification of the totally asymmetric exclusion process, including the probabilities of injection and of death. In the case of the backward-ordered sequential dynamics with the death probability larger than the critical value, the average particle density in the stationary state was erroneously reported to equal the injection probability. Correcting the error, we find that the average density is given by the death probability rather than the injection probability.
Collapse
|
21
|
Choi EJ, Kim DH, Kim JG, Kim DY, Kim JD, Seol OJ, Jeong CS, Park JW, Choi MY, Kang SG, Costa ME, Ojeda SR, Lee BJ. Estrogen-dependent transcription of the NEL-like 2 (NELL2) gene and its role in protection from cell death. J Biol Chem 2010; 285:25074-84. [PMID: 20538601 DOI: 10.1074/jbc.m110.100545] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
NELL2 (neural tissue-specific epidermal growth factor-like repeat domain-containing protein) is a secreted glycoprotein that is predominantly expressed in neural tissues. We reported previously that NELL2 mRNA abundance in brain is increased by estrogen (E2) treatment and that NELL2 is involved in the E2-dependent organization of a sexually dimorphic nucleus in the preoptic area. In this study we cloned the mouse NELL2 promoter and found it to contain two half-E2 response elements. Electrophoretic mobility shift assays and promoter assays showed that E2 and its receptors (ERalpha and ERbeta) stimulated NELL2 transcription by binding to the two half-E2 response elements. Hippocampal neuroprogenitor HiB5 cells expressing recombinant NELL2 showed increased cell survival under cell death-inducing conditions. Blockade of endogenous synthesis of NELL2 in HiB5 cells abolished the cell survival effect of E2 and resulted in a decrease in phosphorylation of extracellular signal-regulated kinase 1 and 2 (ERK1/2). These data suggest that the NELL2 gene is trans-activated by E2 and contributes to mediating the survival promoting effects of E2 via intracellular signaling pathway of ERK.
Collapse
Affiliation(s)
- Eun Jung Choi
- Department of Biological Sciences, University of Ulsan, Ulsan 680-749, South Korea
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
22
|
Cheong SH, Lee KM, Yang YI, Seo JY, Choi MY, Yoon YC. Blind oral endotracheal intubation of rats using a ventilator to verify correct placement. Lab Anim 2010; 44:278-80. [PMID: 20385651 DOI: 10.1258/la.2010.009118] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Endotracheal intubation in rats is challenging due to difficulties visualizing the epiglottis and vocal cords. No visualization of these structures results in repeated intubation attempts which can cause trauma to the oral cavity and/or oesophagus, and death of the animal due to respiratory failure. Here, we describe a simple blind oral tracheal intubation technique in the rat that decreases the frequency of repeated intubations using an intubation device that comprises a 16 G intravenous catheter and a modified 18 G epidural needle, and a rodent ventilator. The epidural needle is bent in such a way that it curves in conformity with the rat's oral airway in order to direct the catheter into the larynx, and the rodent ventilator is used to verify its correct placement. The first attempt success rate of endotracheal intubation using the blind oral tracheal intubation technique with a rodent ventilator was greater than the first attempt success rate using the blind oral tracheal intubation technique without using a rodent ventilator. Although this method is a simple modification of a previously described method of blind oral endotracheal intubation, our method is easy to learn, inexpensive and does not require specialized equipment.
Collapse
Affiliation(s)
- S H Cheong
- Department of Anesthesia and Critical Care Medicine, Paik Hospital, Inje University, Busan, Korea.
| | | | | | | | | | | |
Collapse
|
23
|
Cheong SH, Lee JH, Lee KM, Cho KR, Yang YI, Seo JY, Yoon SY, Lee JN, Choi MY, Lee SE, Kim YH, Lim SH. The effects of hemodilution on acute inflammatory responses in a bleomycin-induced lung injury model. Exp Lung Res 2010; 35:841-57. [PMID: 19995278 DOI: 10.3109/01902140902946962] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Acute normovolemic hemodilution (ANH) can be used in acute lung injury (ALI) patients who refuse blood transfusions. To investigate the effects of hemodilution on the acute inflammatory response in lung injury, the authors studied the effects of ANH in a rat model of bleomycin-induced lung injury. Bleomycin (10 mg/kg) was used to induce lung injury in 2 groups of rats. The treatment groups included a lung injury group with hemodilution (HI), a lung injury group without hemodilution (NHI), and a control group. Hemodilution was performed by removing blood and substituting the same amount of hydroxyethyl starch solution targeted to 7.0 g/dL via the right and left internal jugular veins. At day 3 after bleomycin instillation, systemic hemoglobin concentration was 9.5 +/- 1.1 g/dL. Tumor necrosis factor-alpha, interleukin-1beta, and interleukin-6 levels measured in the bronchoalveolar lavage fluid (BALF), blood, and lung tissue were not significantly different between the HI and NHI groups 3 days after lung injury. Microscopic findings showed fibrosis and inflammation in the HI and NHI groups 28 days after lung injury, but no significant differences were found between the 2 groups. Hemodilution after bleomycin administration did not further affect the acute inflammatory response or lung injury.
Collapse
Affiliation(s)
- Soon Ho Cheong
- Department of Anesthesia and Pain Medicine, Paik Hospital, Inje University, Busan, Republic of Korea.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
24
|
Choi MY, Oh HJ, Kwon KJ, Song EM, Kim SH, Jun YH, Choi HJ, Kim YK. A Case Report on Successful Nonsurgical Treatment Using Antibiotics Alone in Aortic Stent Infection Diagnosed by Positron Emission Tomography. Infect Chemother 2010. [DOI: 10.3947/ic.2010.42.6.407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- Min Young Choi
- Department of Internal Medicine, Ewha Womans University, College of Medicine, Seoul, Korea
| | - Hyun Jung Oh
- Department of Internal Medicine, Ewha Womans University, College of Medicine, Seoul, Korea
| | - Kyoung Joo Kwon
- Department of Internal Medicine, Ewha Womans University, College of Medicine, Seoul, Korea
| | - Eun Mi Song
- Department of Internal Medicine, Ewha Womans University, College of Medicine, Seoul, Korea
| | - Soo Hyun Kim
- Department of Internal Medicine, Ewha Womans University, College of Medicine, Seoul, Korea
| | - Yun Hee Jun
- Department of Internal Medicine, Ewha Womans University, College of Medicine, Seoul, Korea
| | - Hee Jung Choi
- Department of Internal Medicine, Ewha Womans University, College of Medicine, Seoul, Korea
| | - Yoo Kyoung Kim
- Department of Radiology, Ewha Womans University, College of Medicine, Seoul, Korea
| |
Collapse
|
25
|
Ha T, Chung S, Choi MY. 1/t pressure and fermion behaviour of water in two dimensions. J Phys Condens Matter 2009; 21:202101. [PMID: 21825506 DOI: 10.1088/0953-8984/21/20/202101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
A variety of metal vacuum systems display the celebrated 1/t pressure, namely power-law dependence on time t, with the exponent close to unity, the origin of which has been a long-standing controversy. Here we propose a chemisorption model for water adsorbates, based on the argument for fermion behaviour of water vapour adsorbed on a stainless-steel surface, and obtain analytically the power-law behaviour of pressure, with an exponent of unity. Further, the model predicts that the pressure should depend on the temperature T according to T(3/2), which is indeed confirmed by our experiment. Our results should help elucidate the unique characteristics of the adsorbed water.
Collapse
Affiliation(s)
- Taekyun Ha
- Department of Physics, POSTECH, Pohang 790-784, Republic of Korea
| | | | | |
Collapse
|
26
|
Wee YM, Kim SC, Koo SK, Kim YH, Jung EJ, Choi MY, Park YH, Park KT, Lim DG, Han DJ. Improved islet yields after purification following the novel endogenous trypsin inhibitor and histidine-tryptophan-ketoglutarate treatment in pigs. Transplant Proc 2008; 40:2585-7. [PMID: 18929808 DOI: 10.1016/j.transproceed.2008.08.020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
BACKGROUND Adult porcine islet xenotransplantation into humans is greatly diminished by the difficulty to isolate islets because of their fragility. The goal of this study was to improve the efficacy of islet yields using endogenous trypsin inhibitor and histidine-tryptophan-ketoglutarate (HTK) perfusate. METHOD We compared two porcine islet isolation protocols: Eurocollins solution for in situ pancreas perfusion without use of an endogenous trypsin inhibitor versus HTK solution including endogenous trypsin inhibitor for pancreas perfusion. RESULTS Endogenous trypsin inhibitor and HTK strategies significantly improved total islet yield, recovery, and islet index after purification (P < .05), whereas unpurified islet yield did not increase. An average of 228,000 +/- 95,000 islet equivalents (IEQ) (n = 20) purified islets were obtained in the first group compared with 115,000 +/- 56,000 IEQ (n = 18) in the second group. The average islet index was significantly increased in the first group compared with the second group before and after purification: before: 0.28 versus 0.49 versus after: 0.25 versus 0.4 (P < .05). At this time, islet purity, viability, and stimulation index did not show a significant difference between groups. CONCLUSION Our study showed that endogenous trypsin inhibitor and HTK strategies significantly improved purified islet isolation efficacy because of reduction of islet fragility.
Collapse
Affiliation(s)
- Y M Wee
- Asan Institute for Life Science, Seoul, Korea
| | | | | | | | | | | | | | | | | | | |
Collapse
|
27
|
Koo SK, Kim SC, Wee YM, Kim YH, Jung EJ, Choi MY, Park YH, Park KT, Lim DG, Han DJ. Experimental microencapsulation of porcine and rat pancreatic islet cells with air-driven droplet generator and alginate. Transplant Proc 2008; 40:2578-80. [PMID: 18929806 DOI: 10.1016/j.transproceed.2008.08.019] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Transplantation of microencapsulated islets is proposed as an ideal therapy for the treatment of type 1 diabetes mellitus without immunosuppression. This strategy is based on the principle that foreign cells are protected from the host immune system by an artificial membrane. The aim of this study was to establish an ideal condition of microencapsulation using an air-driven droplet generator and alginate in vitro. The optimal conditions for islet encapsulation were an alginate inflow rate of 10 mL/h, CO2 flow rate of 2.0 L/min in a concentration of 2% alginate. For 2.5% alginate, the alginate inflow rate of 20 mL/h, CO2 flow rate 3.0 L/min was ideal; alginate inflow rate of 40 mL/h, CO2 flow rate of 4.0 L/min showed good microcapsules at 3% alginate. Viability of encapsulated islets was greater than 90%. In terms of insulin secretion, encapsulated islets secreted insulin in response to glucose in static culture medium. However, there was no normal response to low or high glucose challenge with a stimulation index less than 2.0. Microencapsulation of pig islets was successfully performed with air-driven droplet generator and alginate in vitro. Further studies about biocompatibility and glucose control in vivo may provide a useful tool for treatment of patients with diabetes mellitus.
Collapse
Affiliation(s)
- S K Koo
- Asan Institute for Life Science, Seoul, Korea
| | | | | | | | | | | | | | | | | | | |
Collapse
|
28
|
Abstract
It is commonly believed that spike timings of a postsynaptic neuron tend to follow those of the presynaptic neuron. Such orthodromic firing may, however, cause a conflict with the functional integrity of complex neuronal networks due to asymmetric temporal Hebbian plasticity. We argue that reversed spike timing in a synapse is a typical phenomenon in the cortex, which has a stabilizing effect on the neuronal network structure. We further demonstrate how the firing causality in a synapse is perturbed by synchronous neural activity and how the equilibrium property of spike-timing dependent plasticity is determined principally by the degree of synchronization. Remarkably, even noise-induced activity and synchrony of neurons can result in equalization of synaptic efficacy.
Collapse
Affiliation(s)
- Myoung Won Cho
- BK21 Frontier Physics Research Division, Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea
| | | |
Collapse
|
29
|
Kim YH, Choi MY, Kim YS, Park CH, Lee JH, Chung IY, Yoo JM, Choi WS, Cho GJ, Kang SS. Triamcinolone acetonide protects the rat retina from STZ-induced acute inflammation and early vascular leakage. Life Sci 2007; 81:1167-73. [PMID: 17881007 DOI: 10.1016/j.lfs.2007.08.024] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2007] [Revised: 08/08/2007] [Accepted: 08/17/2007] [Indexed: 10/22/2022]
Abstract
Streptozotocin (STZ) has been commonly used to induce in vivo and in vitro hyperglycemic diabetes and its toxicity leads to inflammation and vascular injury. Triamcinolone acetonide (TA), as an anti-angiogenic/anti-inflammatory drug, is clinically used to improve the visual acuity in neovascular and edematous ocular diseases. The aim of this study was to investigate the effect of TA on early inflammation and vascular leakage in the retina of STZ-induced hyperglycemic rats. Hyperglycemia was induced in 8-week-old male Sprague-Dawley (SD) rats by a single intraperitoneal injection of STZ (65 mg/kg); only rats with blood glucose levels >13.9 mmol/l 1 day after STZ injection were included in STZ-hyperglycemic group. Sex- and age-matched SD rats injected with buffer were used as the control group. One day before STZ and buffer injection, 2 microl TA (4 mg/ml in saline) and 2 microl saline were intravitreal-injected into the right and the left eyes of rats, respectively. Retinal vascular leakage was measured using the Evans-blue method. Changes in pro-inflammatory target genes, such as tumor necrotic factor (TNF)-alpha, intracellular adhesion molecule (ICAM)-1, and vascular endothelial growth factor (VEGF) were assessed by immunoblottings, immunostaining, and ELISA analyses. Vascular hyperleakage and up-regulation of most pro-inflammatory genes peaked within a few days after STZ injection and had recovered. However, these changes were blocked by TA pretreatment. Our data suggest that TA controls STZ-induced early vascular leakage and temporary pro-inflammatory signals in the rat retina.
Collapse
Affiliation(s)
- Y H Kim
- Department of Anatomy and Neurobiology, Institute of Health Science, School of Medicine, Gyeongsang National University, Jinju, Gyeongnam 660-751, South Korea
| | | | | | | | | | | | | | | | | | | |
Collapse
|
30
|
Kim YH, Choi MY, Kim YS, Han JM, Lee JH, Park CH, Kang SS, Choi WS, Cho GJ. Protein kinase C delta regulates anti-apoptotic alphaB-crystallin in the retina of type 2 diabetes. Neurobiol Dis 2007; 28:293-303. [PMID: 17904375 DOI: 10.1016/j.nbd.2007.07.017] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2007] [Revised: 07/06/2007] [Accepted: 07/17/2007] [Indexed: 12/22/2022] Open
Abstract
We investigated the relationship between phosphorylation of alphaB-crystallin (alphaBC) and retinal apoptosis in type 2 diabetes. The retinas of male Otsuka Long-Evans Tokushima fatty (OLETF) rats at 24 and 35 weeks were used as an animal model for type 2 diabetes and sex- and age-matched Long-Evans Tokushima Otsuka (LETO) rats were used as controls. In the retinas of 35-week OLETF rats, the interaction between alphaBC and protein kinase C delta (PKC delta) among the PKC isozymes, alphaBC phosphorylation at Ser45 (S45p-alphaBC), TUNEL-positive apoptotic ganglion cells, several apoptotic signs, and co-localization of S45p-alphaBC and TUNEL significantly increased as compared with other groups while the alphaBC-Bax interaction greatly decreased. These changes were abolished by rottlerin treatment, a highly specific PKC delta inhibitor. These results suggest that PKC delta is involved in regulation of anti-apoptotic function of alphaBC in the retina of type 2 diabetes.
Collapse
Affiliation(s)
- Y H Kim
- Department of Anatomy and Neurobiology, School of Medicine, Institute of Health Science, Gyeongsang National University, Jinju, Chilam-dong 92, Jinju, Gyeongnam 660-751, South Korea
| | | | | | | | | | | | | | | | | |
Collapse
|
31
|
Kim S, Yi J, Choi MY. Magnetization of circular DNA. Phys Rev E Stat Nonlin Soft Matter Phys 2007; 76:012902. [PMID: 17677517 DOI: 10.1103/physreve.76.012902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2006] [Indexed: 05/16/2023]
Abstract
We investigate the orbital magnetization of DNA molecules in the relaxed circular structure. It is shown that DNA of homogeneous sequence exhibits paramagnetic responses to external magnetic fields and, surprisingly, the magnetism of circular DNA is equivalent to that of linear DNA. This turns out to result from the fact that the electron population is localized largely on one of the strands. More intriguingly, the magnetic susceptibility is observed to depend on the ring topology defined by the linking number. We also consider sequence heterogeneity and find that the magnetization displays characteristic oscillations, the pattern of which depends crucially on the sequence and the base content.
Collapse
Affiliation(s)
- Seongjin Kim
- Department of Physics, Pusan National University, Busan 609-735, Korea
| | | | | |
Collapse
|
32
|
Kim YH, Chung IY, Choi MY, Kim YS, Lee JH, Park CH, Kang SS, Roh GS, Choi WS, Yoo JM, Cho GJ. Triamcinolone suppresses retinal vascular pathology via a potent interruption of proinflammatory signal-regulated activation of VEGF during a relative hypoxia. Neurobiol Dis 2007; 26:569-76. [PMID: 17434742 DOI: 10.1016/j.nbd.2007.02.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2006] [Revised: 01/31/2007] [Accepted: 02/04/2007] [Indexed: 10/23/2022] Open
Abstract
We examined the effect of triamcinolone acetonide (TA), a corticosteroid, on the relationship between vascular pathophysiology and vascular endothelial growth factor (VEGF) activation in the retina of a rat model of oxygen-induced retinopathy (OIR). OIR was induced by exposure of hyperoxia (80% oxygen) to Sprague-Dawley (SD) rats from P2 to P14 and then returned to normoxic conditions. TA was intravitreal-injected once into the right eye of OIR rats at P15. Effects of TA on vascular pathophysiology or changes of various genes in response to hypoxia and/or proinflammation under hypoxic retina were assessed by the Evans-blue method, fluorescein isothiocyanate-dextran (FITC-D) infusion, immunoblotting, and ELIZA. TA not only reduced retinal neovascularization and vascular leakage in the OIR-rat retina, but also blocked the induction of hypoxia-response proinflammatory genes before it negatively controlled VEGF activation. These findings suggest a potential that TA suppresses retinal neovascular pathophysiology via proinflammation-mediated activation of VEGF during hypoxia.
Collapse
Affiliation(s)
- Y H Kim
- Department of Anatomy and Neurobiology, College of Medicine, Gyeongsang National University, Chilam-dong 92, Jinju, Gyungnam 660-751, South Korea
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
33
|
Jeong D, Choi J, Choi MY. Collective oscillations, bicluster motion, and dynamical order in a system of globally coupled rotors with repulsive interactions. Phys Rev E 2007; 74:056106. [PMID: 17279967 DOI: 10.1103/physreve.74.056106] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2005] [Revised: 07/02/2006] [Indexed: 11/07/2022]
Abstract
We perform extensive numerical simulations on a system of globally coupled rotors with repulsive interactions. By controlling systematically initial conditions, we determine the criterion for the emergence of bicluster motion. It is found that stable bicluster motion emerges at low temperatures, where the initial kinetic energy accounts for less than about 60% of the total energy. Also observed are collective oscillations of the potential energy and the magnetization, which are persistent. With appropriately chosen initial conditions, the system exhibits characteristic motion where biclusters keep forming and disappearing continually. It is argued that such bicluster motion is closely related to the dynamical order suggested recently.
Collapse
Affiliation(s)
- Daun Jeong
- Department of Physics and Center for Theoretical Physics, Seoul National University, Seoul 151-747, Korea
| | | | | |
Collapse
|
34
|
Abstract
The effects of solute polarizability on solvation and solute transport in the room-temperature ionic liquid 1-ethyl-3-methylimidazolium hexafluorophosphate (EMI+PF(6)-) are investigated via molecular dynamics simulations. A valence-bond description is employed to account for the instantaneous adjustment of the solute electronic charge distribution to the fluctuating solvent environment. It is found that the ultrafast inertial component of solvation dynamics becomes slower as the solute polarizability grows. Moreover, its contribution to overall solvent relaxation becomes reduced with increasing polarizability, especially in the case of nonequilibrium solvation dynamics. Overall, the inclusion of the solute electronic polarizability in the simulations improves the agreement with time-dependent Stokes shift measurements.
Collapse
Affiliation(s)
- Daun Jeong
- Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea
| | | | | | | |
Collapse
|
35
|
Shim Y, Jeong D, Choi MY, Kim HJ. Rotational dynamics of a diatomic solute in the room-temperature ionic liquid 1-ethyl-3-methylimidazolium hexafluorophosphate. J Chem Phys 2006; 125:61102. [PMID: 16942266 DOI: 10.1063/1.2232303] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Reorientational time correlation functions C(l)(t)( identical withP(l)[cos theta(t)]) for a diatomic solute in 1-ethyl-3-methylimidazolium hexafluorophosphate (EMI(+)PF(6) (-)) are analyzed via molecular dynamics computer simulations, where <...> denotes an equilibrium ensemble average, P(l) the lth order Legendre polynomial and theta(t) the angle between the solute orientation at time t and its initial direction. Overall results are indicative of heterogeneous dynamics in EMI(+)PF(6) (-). For a small nondipolar solute, C(l)(t) are well-described as stretched exponential functions in wide time ranges. One striking feature is that after rapid initial relaxation, C(2)(t) decays more slowly than C(1)(t). As a result, the correlation time associated with the former is considerably longer than that with the latter. This is ascribed to solvent structural fluctuations, which allow large-amplitude solute rotations. As the solute size grows, relaxation of C(l)(t) approaches exponential decay.
Collapse
Affiliation(s)
- Youngseon Shim
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
| | | | | | | |
Collapse
|
36
|
Yoon BG, Choi J, Choi MY, Fortin JY. Health status and resonance in a model for living organisms under periodic stress and healing. Phys Rev E Stat Nonlin Soft Matter Phys 2006; 73:031905. [PMID: 16605556 DOI: 10.1103/physreve.73.031905] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2005] [Revised: 12/07/2005] [Indexed: 05/08/2023]
Abstract
We apply the dynamic model for failures to a living organism under periodic stress and study how the health status of the organism evolves. It is found that without healing, the average fraction of intact cells decays either stepwise to zero or to a constant value far from zero, depending on the peak value of the periodic stress. As the parameter measuring the healing probability is raised from zero, the fraction exhibits oscillating behavior, reminiscent of periodic synchronization. The power spectrum at the stress frequency at first increases with the healing parameter, then decreases, which may be called healing resonance. We also study the time evolution of the system in the case that the healing parameter varies periodically with time and observe a transition from the unhealthy state to the healthy one as the healing frequency increases. This suggests how to adjust the frequency of medical treatment to the optimum.
Collapse
Affiliation(s)
- B-G Yoon
- Department of Physics, University of Ulsan, Ulsan 680-749, Korea.
| | | | | | | |
Collapse
|
37
|
Abstract
PURPOSE The surgical success rates for intermittent exotropia of the convergence insufficiency type have been reported to be variable, and most were studied retrospectively in adults. The purpose of this study was to evaluate prospectively the long-term surgical results of unilateral lateral rectus (LR) muscle recession and medial rectus (MR) muscle resection in children with intermittent exotropia of the convergence insufficiency type. METHODS A total of 14 children with intermittent exotropia greater at near than at distance by 10 prism diopters (PD) or more were included in this prospective study. The amounts of resection and recession were based on near and distance deviation, respectively. Minimum follow-up was 1 year (mean 26.6 months; range, 12-68 months) after surgery. The paired t-test was used to compare preoperative and postoperative measurements of the angle of deviation at distance and near, near-distance difference. RESULTS Significant postoperative reduction was achieved in terms of mean distance exodeviation, from 22.5 PD to 9.1 PD (P=0.000), and mean near exodeviation from 33.8 PD to 13.6 PD (P=0.000). Mean near-distance difference reduced from 11.3 PD preoperatively to 4.6 PD postoperatively (P=0.000). Fresnel prism was used temporarily to treat postoperative esotropia in only one patient for postoperative 6 months. CONCLUSIONS Unilateral surgery biased to MR strengthening more than LR weakening in children with intermittent exotropia of the convergence insufficiency type, was found to successfully reduce both distance and near deviation and to collapse near-distance differences with a low risk of long-term postoperative esotropia.
Collapse
Affiliation(s)
- M Y Choi
- Department of Ophthalmology, Chungbuk National University College of Medicine, Cheongju, Korea
| | | | | |
Collapse
|
38
|
Kang H, Jo J, Kim HJ, Choi MY, Rhee SW, Koh DS. Glucose metabolism and oscillatory behavior of pancreatic islets. Phys Rev E Stat Nonlin Soft Matter Phys 2005; 72:051905. [PMID: 16383643 DOI: 10.1103/physreve.72.051905] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2004] [Revised: 08/15/2005] [Indexed: 05/05/2023]
Abstract
A variety of oscillations are observed in pancreatic islets. We establish a model incorporating two oscillatory systems of different time scales: One is the well-known bursting model in pancreatic cells and the other is the glucose-insulin feedback model which considers direct and indirect feedback of secreted insulin. These two are coupled to interact with each other in the combined model, and two basic assumptions are made on the basis of biological observations: The conductance gK(ATP) for the ATP-dependent potassium current is a decreasing function of the glucose concentration whereas the insulin secretion rate is given by a function of the intracellular calcium concentration. Obtained via extensive numerical simulations are complex oscillations including clusters of bursts, slow and fast calcium oscillations, and so on. We also consider how the intracellular glucose concentration depends upon the extracellular glucose concentration, and examine the inhibitory effects of insulin.
Collapse
Affiliation(s)
- H Kang
- Department of Physics and Center for Theoretical Physics, Seoul National University, Seoul 151-747, Korea
| | | | | | | | | | | |
Collapse
|
39
|
Abstract
PURPOSE To evaluate the long-term results of slanted medial rectus (MR) resection for intermittent exotropia (X(T)) of the convergence insufficiency type. METHODS In all, 10 patients with an X(T) greater at near than at distance by 10 prism diopters (PD) or more were included in this prospective study. Patients received slanted bilateral MR resection. The upper edge of the MR was resected according to the distance exodeviation and the lower edge of the MR was resected according to near exodeviation. The postoperative follow-up period was between 6 and 62 months with a mean of 38.9 months. The paired t-test was used to compare: mean distance angle of deviation preoperatively and postoperatively; mean near angle of deviation preoperatively and postoperatively; and mean near-distance exodeviation difference preoperatively and postoperatively. RESULTS Bilateral slanted MR resections reduced mean exodeviation at distance from 23.0+/-7.2 to 16.3+/-5.4 PD (P=0.03); mean exodeviation at near from 34.3+/-7.7 to 24.6+/-6.9 PD (P=0.01); and mean near-distance difference from 11.4+/-2.6 to 8.3+/-3.5 PD (P=0.04). At the final follow-up examination, all patients demonstrated an exodeviation of 10 PD or more at distance and near, and the exodeviation difference between distance and near deviation was within 10 PD in five of the 10 patients. Three patients had an esodeviation at distance after surgery, but all resolved within 4 weeks. CONCLUSIONS Bilateral slanted MR resections in patients with X(T) of the convergence insufficiency type resulted in undercorrection in all patients.
Collapse
Affiliation(s)
- M Y Choi
- Department of Ophthalmology, Chungbuk National University College of Medicine, Cheongju, Korea. mychoi@ chungbuk.ac.kr
| | | |
Collapse
|
40
|
Hong H, Park H, Choi MY. Collective synchronization in spatially extended systems of coupled oscillators with random frequencies. Phys Rev E Stat Nonlin Soft Matter Phys 2005; 72:036217. [PMID: 16241558 DOI: 10.1103/physreve.72.036217] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2004] [Indexed: 05/05/2023]
Abstract
We study collective behavior of locally coupled limit-cycle oscillators with random intrinsic frequencies, spatially extended over d -dimensional hypercubic lattices. Phase synchronization as well as frequency entrainment are explored analytically in the linear (strong-coupling) regime and numerically in the nonlinear (weak-coupling) regime. Our analysis shows that the oscillator phases are always desynchronized up to d=4 , which implies the lower critical dimension dP(l) =4 for phase synchronization. On the other hand, the oscillators behave collectively in frequency (phase velocity) even in three dimensions (d=3) , indicating that the lower critical dimension for frequency entrainment is dF(l)=2 . Nonlinear effects due to the periodic nature of limit-cycle oscillators are found to become significant in the weak-coupling regime: So-called runaway oscillators destroy the synchronized (ordered) phase and there emerges a fully random (disordered) phase. Critical behavior near the synchronization transition into the fully random phase is unveiled via numerical investigation. Collective behavior of globally coupled oscillators is also examined and compared with that of locally coupled oscillators.
Collapse
Affiliation(s)
- H Hong
- Department of Physics, Chonbuk National University, Jeonju 561-756, Korea and School of Physics, Korea Institute for Advanced Study, Seoul 130-722, Korea
| | | | | |
Collapse
|
41
|
Jeong D, Choi MY, Park H. Slow relaxation in the Ising model on a small-world network with strong long-range interactions. Phys Rev E Stat Nonlin Soft Matter Phys 2005; 71:036103. [PMID: 15903489 DOI: 10.1103/physreve.71.036103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2004] [Indexed: 05/02/2023]
Abstract
We consider the Ising model on a small-world network, where the long-range interaction strength J2 is in general different from the local interaction strength J1, and examine its relaxation behaviors as well as phase transitions. As J(2)/J(1) is raised from zero, the critical temperature also increases, manifesting contributions of long-range interactions to ordering. However, it becomes saturated eventually at large values of J(2)/J(1) and the system is found to display very slow relaxation, revealing that ordering dynamics is inhibited rather than facilitated by strong long-range interactions. To circumvent this problem, we propose a modified updating algorithm in Monte Carlo simulations, assisting the system to reach equilibrium quickly.
Collapse
Affiliation(s)
- Daun Jeong
- Department of Physics, Seoul National University, Seoul 151-747, Korea
| | | | | |
Collapse
|
42
|
Choi MY, Dong F, Miller RE. Multiple tautomers of cytosine identified and characterized by infrared laser spectroscopy in helium nanodroplets: probing structure using vibrational transition moment angles. Philos Trans A Math Phys Eng Sci 2005; 363:393-413. [PMID: 15664890 DOI: 10.1098/rsta.2004.1499] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Infrared laser spectroscopy in helium nanodroplets is used to identify and characterize several distinct tautomers of cytosine. The experimentally observed species correspond to the lowest-energy structures obtained from ab initio calculations, also reported here. The assignment of the infrared vibrational bands in the spectra is aided by the measurement of the corresponding vibrational transition moment angles, which are also calculated using ab initio methods. In the present study we confirm the existence of three primary tautomers and provide tentative assignments for even higher-energy forms of cytosine in helium nanodroplets.
Collapse
Affiliation(s)
- M Y Choi
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599, USA
| | | | | |
Collapse
|
43
|
Shim Y, Choi MY, Kim HJ. A molecular dynamics computer simulation study of room-temperature ionic liquids. I. Equilibrium solvation structure and free energetics. J Chem Phys 2005; 122:44510. [PMID: 15740270 DOI: 10.1063/1.1819317] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Solvation in 1-ethyl-3-methylmidazolium chloride and in 1-ethyl-3-methylimidazolium hexafluorophosphate near equilibrium is investigated via molecular dynamics computer simulations with diatomic and benzenelike molecules employed as probe solutes. It is found that electrostriction plays an important role in both solvation structure and free energetics. The angular and radial distributions of cations and anions become more structured and their densities near the solute become enhanced as the solute charge separation grows. Due to the enhancement in structural rigidity induced by electrostriction, the force constant associated with solvent configuration fluctuations relevant to charge shift and transfer processes is also found to increase. The effective polarity and reorganization free energies of these ionic liquids are analyzed and compared with those of highly polar acetonitrile. Their screening behavior of electric charges is also investigated.
Collapse
Affiliation(s)
- Y Shim
- Department of Physics, Seoul National University, Seoul 151-747, Korea
| | | | | |
Collapse
|
44
|
Shim Y, Choi MY, Kim HJ. A molecular dynamics computer simulation study of room-temperature ionic liquids. II. Equilibrium and nonequilibrium solvation dynamics. J Chem Phys 2005; 122:44511. [PMID: 15740271 DOI: 10.1063/1.1819318] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The molecular dynamics (MD) simulation study of solvation structure and free energetics in 1-ethyl-3-methylimidazolium chloride and 1-ethyl-3-methylimidazolium hexafluorophosphate using a probe solute in the preceding article [Y. Shim, M. Y. Choi and H. J. Kim, J. Chem. Phys. 122, 044510 (2005)] is extended to investigate dynamic properties of these liquids. Solvent fluctuation dynamics near equilibrium are studied via MD and associated time-dependent friction is analyzed via the generalized Langevin equation. Nonequilibrium solvent relaxation following an instantaneous change in the solute charge distribution and accompanying solvent structure reorganization are also investigated. Both equilibrium and nonequilibrium solvation dynamics are characterized by at least two vastly different time scales--a subpicosecond inertial regime followed by a slow diffusive regime. Solvent regions contributing to the subpicosecond nonequilibrium relaxation are found to vary significantly with initial solvation configurations, especially near the solute. If the solvent density near the solute is sufficiently high at the outset of the relaxation, subpicosecond dynamics are mainly governed by the motions of a few ions close to the solute. By contrast, in the case of a low local density, solvent ions located not only close to but also relatively far from the solute participate in the subpicosecond relaxation. Despite this difference, linear response holds reasonably well in both ionic liquids.
Collapse
Affiliation(s)
- Y Shim
- Department of Physics, Seoul National University, Seoul 151-747, Korea
| | | | | |
Collapse
|
45
|
Abstract
Infrared laser spectroscopy is used to show that four structural isomers of the uracil-water binary complex are formed in helium nanodroplets. The assignment of the infrared spectra is aided by measurements of vibrational transition moment angles (VTMAs) for various vibrational modes of these complexes. The experimental results are in excellent agreement with ab initio calculations, which had previously predicated the existence of the same four isomers. The results suggest that the relative abundances of the various isomers formed in helium droplets have more to do with the widths of the valleys in the potential surface that funnel into a particular local minimum than on the associated energetics.
Collapse
Affiliation(s)
- M Y Choi
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599, USA
| | | |
Collapse
|
46
|
Hong H, Park H, Choi MY. Collective phase synchronization in locally coupled limit-cycle oscillators. Phys Rev E Stat Nonlin Soft Matter Phys 2004; 70:045204. [PMID: 15600451 DOI: 10.1103/physreve.70.045204] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2003] [Indexed: 05/24/2023]
Abstract
We study collective behavior of locally coupled limit-cycle oscillators with scattered intrinsic frequencies on d -dimensional lattices. A linear analysis shows that the system should always be desynchronized up to d=4 . On the other hand, numerical investigation for d=5 and d=6 reveals the emergence of the synchronized (ordered) phase via a continuous transition from the fully random desynchronized phase. This demonstrates that the lower critical dimension for the phase synchronization in this system is d(l) =4 .
Collapse
Affiliation(s)
- H Hong
- Department of Physics, Chonbuk National University, Jeonju 561-756, Korea
| | | | | |
Collapse
|
47
|
Hong H, Kim BJ, Choi MY, Park H. Factors that predict better synchronizability on complex networks. Phys Rev E Stat Nonlin Soft Matter Phys 2004; 69:067105. [PMID: 15244784 DOI: 10.1103/physreve.69.067105] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2003] [Revised: 03/04/2004] [Indexed: 05/24/2023]
Abstract
While shorter characteristic path length has in general been believed to enhance synchronizability of a coupled oscillator system on a complex network, the suppressing tendency of the heterogeneity of the degree distribution, even for shorter characteristic path length, has also been reported. To see this, we investigate the effects of various factors such as the degree, characteristic path length, heterogeneity, and betweenness centrality on synchronization, and find a consistent trend between the synchronization and the betweenness centrality. The betweenness centrality is thus proposed as a good indicator for synchronizability.
Collapse
Affiliation(s)
- H Hong
- School of Physics, Korea Institute for Advanced Study, Seoul 130-722, Korea
| | | | | | | |
Collapse
|
48
|
Kim MJ, Choi MY, Lee JK, Ahn Y. Enzymatic selective acylation of glycosides in ionic liquids: significantly enhanced reactivity and regioselectivity. ACTA ACUST UNITED AC 2003. [DOI: 10.1016/j.molcatb.2003.04.001] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
49
|
Abstract
We consider a system of globally coupled rotors, described by a set of Langevin equations, and examine the stability of the incoherent phase. The corresponding Fokker-Planck equation, providing a unified description of microcanonical and canonical ensembles, bears a few solutions, depending upon the ensemble. It is found that the stability of each solution varies differently with the temperature, revealing the inequivalence between the two ensembles. This also suggests a physical explanation of the quasistationarity observed in recent numerical results.
Collapse
Affiliation(s)
- M Y Choi
- Department of Physics, Seoul National University, Seoul 151-747, Korea
| | | |
Collapse
|
50
|
Jeong D, Hong H, Kim BJ, Choi MY. Phase transition in the Ising model on a small-world network with distance-dependent interactions. Phys Rev E Stat Nonlin Soft Matter Phys 2003; 68:027101. [PMID: 14525147 DOI: 10.1103/physreve.68.027101] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2003] [Indexed: 05/24/2023]
Abstract
We study the collective behavior of an Ising system on a small-world network with the interaction J(r) proportional to r(-alpha), where r represents the Euclidean distance between two nodes. In the case of alpha=0 corresponding to the uniform interaction, the system is known to possess a phase transition of the mean-field nature, while the system with the short-range interaction (alpha-->infinity) does not exhibit long-range order at any finite temperature. The Monte Carlo simulations are performed at various values of alpha, and the critical value alpha(c) beyond which the long-range order does not emerge is estimated to be 0. Thus, concluded is the absence of a phase transition in the system with the algebraically decaying interaction r(-alpha) for any nonzero positive value of alpha.
Collapse
Affiliation(s)
- Daun Jeong
- Department of Physics, Seoul National University, Seoul 151-747, Korea
| | | | | | | |
Collapse
|