• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.106.2-106.2
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• 2011

The two competing theories of star formation are based on turbulence and ambipoar diffusion. I will first briefly explain the two theories. There have been analytical (or semi-analytic) models, which estimate star formation rates in a turbulent cloud. Most of them are based on the log-normal density PDF (probability density function) of the turbulent cloud without self-gravity. I will first show that the core (star) formation rate can be increased significantly once self-gravity of a turbulence cloud is taken into account. I will then present the evolution of molecular line profiles of HCO+ and C18O toward a dense core that is forming inside a magnetized turbulent molecular cloud. Features of the profiles can be affected more significantly by coupled velocity and abundance structures in the outer region than those in the inner dense part of the core. During the evolution of the core, the asymmetry of line profiles easily changes from blue to red, and vice versa. Finally, I will introduce a method for incorporating ambipolar diffusion in the strong coupling approximation into a multidimensional magnetohydrodynamic code.

• Journal of the Korean Ceramic Society
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• v.34 no.7
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• pp.713-721
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• 1997

Molecular dynamic (MD) simulations with new interatomic potential function including the covalent bond were performed on the phase transition of $\alpha$-quartz-type GeO2 under high pressure. The optimized crystal structure and the pressure dependence of the lattice constant showed higher reproducibility than the previous models and were in very good agreement with the experimental data. A phase transition of $\alpha$-quartz and $\alpha$-quartz-type GeO2 by simulation was found approximately 24 GPa and 6-7 GPa, respectively. This phase transition involved an abrupt volume shrinkage and showed 4-6 coordination mixed structure with the increasing in the coordination number of cation.

• Advances in concrete construction
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• v.4 no.4
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• pp.305-317
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• 2016

Porous materials such as concrete could be subjected to aggressive ions transport. Durability of cement paste is extremely depended on water and ions penetration into its interior sections. These ions transport could lead different damages depending on reactivity of ions, their concentrations and diffusion coefficients. In this paper, chloride diffusion process in cement hydrates is simulated at atomistic scale using molecular dynamics. Most important phase of cement hydrates is calcium silicate hydrate (C-S-H). Tobermorite, one of the most famous crystal analogues of C-S-H, is used as substrate in the simulation model. To conduct simulation, a nanopore is considered in the middle of simulation cell to place water molecules and aggressive ions. Different chloride salts are considered in models to find out which one is better for calculation of the transport properties. Diffusion coefficients of water molecules and chloride ions are calculated and validated with existing analytical and experimental works. There are relatively good agreements among simulation outputs and experimental results.

• Proceedings of the PSK Conference
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• 2003.10b
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• pp.65.2-65.2
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• 2003

88 selective COX-2 inhibitors belonging to three chemical classes (triaryl rings, diaryl cycloalkanopyrazoles, and diphenyl hydrazides) were studied using comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA). Partial least squares analysis produced statistically significant models with q values of 0.84 and 0.79 for CoMFA and CoMSIA, respectively. The key spatial properties were detected by careful analysis of the isocontour maps. The binding energies calculated from flexible docking correlated with inhibitory activities by the least-squares fit method. (omitted)

• BMB Reports
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• v.43 no.4
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• pp.225-232
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• 2010

Parkinson's Disease (PD) is a common neurodegenerative disease characterized by the progressive degeneration of nigrostriatal dopaminergic (DA) neurons. Although the causative factors of PD remain elusive, many studies on PD animal models or humans suggest that glial activation along with neuroinflammatory processes contribute to the initiation or progression of PD. Additionally, several groups have proposed that dysfunction of the blood-brain barrier (BBB) combined with infiltration of peripheral immune cells play important roles in the degeneration of DA neurons. However, these neuroinflammatory events have only been investigated separately, and the issue of whether these phenomena are neuroprotective or neurotoxic remains controversial. We here review the current knowledge regarding the functions of these neuroinflammatory processes in the brain. Finally, we describe therapeutic strategies for the regulation of neuroinflammation with the goal of improving the symptoms of PD.

• Molecular & Cellular Toxicology
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• v.5 no.2
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• pp.99-107
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• 2009

Naphthalene is bicyclic aromatic compound that is widely used in various domestic and commercial applications including lavatory scent disks, soil fumigants and moth balls. Exposure to naphthalene results in the development of bronchiolar damage, cataracts and hemolytic anemia in humans and laboratory animals. However, little information is available regarding the mechanism of naphthalene toxicity. We investigated gene expression profiles and potential signature genes in human hepatocellular carcinoma HepG2 cells and human promyelocytic leukemia HL-60 cells after 3 h and 48 h incubation with the IC$_{20}$ and IC$_{50}$ of naphthalene by using 44 k agilent whole human genome oligomicroarray and operon human whole 35 k oligomicroarray, respectively. We identified 616 up-regulated genes and 2,088 down-regulated genes changed by more than 2-fold by naphthalene in HepG2 cells. And in HL-60, we identified 138 up-regulated genes and 182 down-regulated genes changed by more than 2-fold. This study identified several interesting targets and functions in relation to naphthalene-induced toxicity through a gene ontology analysis method. Apoptosis and cell cycle related genes are more commonly expressed than other functional genes in both cell lines. In summary, the use of in vitro models with global expression profiling emerges as a relevant approach toward the identification of biomarkers associated with toxicity after exposure to a variety of environmental toxicants.

• Bulletin of the Korean Chemical Society
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• v.32 no.7
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• pp.2397-2404
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• 2011

Variable selection k nearest neighbor QSAR modeling approach was applied to a data set of 80 3-arylisoquinolines exhibiting cytotoxicity against human lung tumor cell line (A-549). All compounds were characterized with molecular topology descriptors calculated with the MolconnZ program. Seven compounds were randomly selected from the original dataset and used as an external validation set. The remaining subset of 73 compounds was divided into multiple training (56 to 61 compounds) and test (17 to 12 compounds) sets using a chemical diversity sampling method developed in this group. Highly predictive models characterized by the leave-one out cross-validated $R^2$ ($q^2$) values greater than 0.8 for the training sets and $R^2$ values greater than 0.7 for the test sets have been obtained. The robustness of models was confirmed by the Y-randomization test: all models built using training sets with randomly shuffled activities were characterized by low $q^2{\leq}0.26$ and $R^2{\leq}0.22$ for training and test sets, respectively. Twelve best models (with the highest values of both $q^2$ and $R^2$) predicted the activities of the external validation set of seven compounds with $R^2$ ranging from 0.71 to 0.93.

• BMB Reports
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• v.50 no.11
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• pp.546-553
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• 2017

Aging is a natural and gradual process in human life. It is influenced by heredity, environment, lifestyle, and disease. DNA methylation varies with age, and the ability to predict the age of donor using DNA from evidence materials at a crime scene is of considerable value in forensic investigations. Recently, many studies have reported age prediction models based on DNA methylation from various tissues and body fluids. Those models seem to be very promising because of their high prediction accuracies. In this review, the changes of age-associated DNA methylation and the age prediction models for various tissues and body fluids were examined, and then the applicability of the DNA methylation-based age prediction method to the forensic investigations was discussed. This will improve the understandings about DNA methylation markers and their potential to be used as biomarkers in the forensic field, as well as the clinical field.

• 한국전산유체공학회:학술대회논문집
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• 2008.03a
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• pp.84-91
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• 2008

Generalized hydrodynamic (GH) theory for multi-species gas and the computational models are developed for the numerical simulation of hypersonic rarefied gas flow on the basis of Eu's GH theory. The rotational non-equilibrium effect of diatomic molecules is taken into account by introducing excess normal stress associated with the bulk viscosity. The numerical model for the diatomic GH theory is developed and tested. Moreover, with the experience of developing the dia-tomic GH computational model, the GH theory is extended to a multi-species gas including 5 species; O$_2$, N$_2$, NO, O, N. The multi-species GH model includes diffusion relation due to the molecular collision and thermal phenomena. Two kinds of GH models are developed for an axisymmetric flow solver. By compar-ing the computed results of diatomic and multi-species GH theories with those of the Navier-Stokes equations and the DSMC results, the accuracy and physical consistency of the GH computational models are examined.

• BMB Reports
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• v.44 no.7
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• pp.435-445
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• 2011

Serous ovarian cancer is one of the most lethal gynecological malignancies. Progress on effective diagnostics and therapeutics for this disease are hampered by ambiguity as to the cellular origins of this histotype of ovarian cancer, as well as limited suitable animal models to analyze early stages of disease. In this report, we will review current animal models with respect to the two proposed progenitor cells for serous ovarian cancer, the ovarian surface epithelium and the fallopian tube epithelium.