• Journal of Korea Water Resources Association
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• v.43 no.9
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• pp.801-811
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• 2010

A three-dimensional numerical model called NEWTANK is employed to investigate solitary wave run-up with an internal wave-maker on a steep slope. The numerical model solves the spatially averaged Navier-Stokes equations for two-phase flows. The LES (large-eddy-simulation) approach is adopted to model the turbulence effect by using the Smagorinsky SGS (sub-grid scale) closure model. A two-step projection method is adopted in numerical solutions, aided by the Bi-CGSTAB (Bi-Conjugate Gradient Stabilized) method to solve the pressure Poisson equation for the filtered pressure field. The second-order accurate VOF (volume-of-fluid) method is used to track the distorted and broken free surface. A solitary wave is first internally generated and propagated over a constant water depth in the three-dimensional domain. Numerically predicted results are compared with analytical solutions and numerical errors are analyzed in detail. The model is then applied to study solitary wave run-up on a steep slope and the obtained results are compared with available laboratory measurements.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.10
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• pp.4331-4338
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• 2014

$N^1$-(2, 5-dimethoxyphenyl)-$N^8$-hydroxyoctanediamide (N25) is a novel SAHA cap derivative of HDACi, with a patent (No. CN 103159646). This invention is a hydroxamic acid compound with a structural formula of $RNHCO(CH_2)6CONHOH$ (wherein R=2, 5dimethoxyaniline), a pharmaceutically acceptable salt which is soluble. In the present study, we investigated the effects of N25 with regard to drug distribution and molecular docking, and anti-proliferation, apoptosis, cell cycling, and $LD_{50}$. First, we designed a molecular approach for modeling selected SAHA derivatives based on available structural information regarding human HDAC8 in complex with SAHA (PDB code 1T69). N25 was found to be stabilized by direct interaction with the HDAC8. Anti-proliferative activity was observed in human glioma U251, U87, T98G cells and human lung cancer H460, A549, H1299 cells at moderate concentrations ($0.5-30{\mu}M$). Compared with SAHA, N25 displayed an increased antitumor activity in U251 and H460 cells. We further analyzed cell death mechanisms activated by N25 in U251 and H460 cells. N25 significantly increased acetylation of Histone 3 and inhibited HDAC4. On RT-PCR analysis, N25 increased the mRNA levels of p21, however, decreased the levels of p53. These resulted in promotion of apoptosis, inducing G0/G1 arrest in U251 cells and G2/M arrest in H460 cells in a time-dependent and dose-dependent manner. In addition, N25 was able to distribute to brain tissue through the blood-brain barrier of mice ($LD_{50}$: 240.840mg/kg). In conclusion, our findings demonstrate that N25 will provide an invaluable tool to investigate the molecular mechanism with potential chemotherapeutic value in several malignancies, especially human glioma.

• Journal of Korean Society of Forest Science
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• v.106 no.1
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• pp.1-9
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• 2017

Forest harvest as large scale artificial disturbance makes edge environment in both clear-cutted and forested habitat. To clarify the development and recovery process of forest edge after disturbances is essential to understand vegetation responses and landscape level consequences such as edge-distance. In Korea, after clear-cutting, edge-related changes of environment and vegetation was not clarified yet. In Korean red pine (Pinus densiflora) forest, by applying space-for-time approach (sites with undisturbed and 1, 3, 10, 16 yr after cutting), the edge-related change of plant abundance and abiotic factors were determined for 20 line-transect (60 m) and 340 ($1m{\times}5m$) quadrats, and clarified depth and duration of the disturbance. Immediately after edge formation, within 15m form the edge, biotic and abiotic factors such as cover, richness, canopy openness, temperature and moisture content exhibited larger changes compared to forest interior. Plant abundance and abiotic variables were stabilized at the level of forest inside within 16 yr and 10 yr after edge creation, respectively. Woody (tree and shrub) species generally was showed larger increment with proximity to edge than did herb or graminoid species. In addition, negative interactions between woody and herbaceous species were detected during the period of forest edge closure. Our results suggested that depth of forest edge formed by clear-cutting of Korean red pine forest was at least from 15 m to 20 m and edge effect were likely sustained more than 16 years. As the first empirical study on edge-distance between two contrast habitats of clear-cutted and adjacent forest in South Korea, the analytical reality on landscape structure and habitat patches can be improved.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.91-91
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• 2013

Imagine a world where we could biomanufacture hybrid nanomaterials having atomic-scale resolution over functionality and architecture. Toward this vision, a fundamental challenge in materials science is how to design and synthesize protein-like material that can be fully self-assembled and exhibit information-specific process. In an ongoing effort to extend the fundamental understanding of protein structure to non-natural systems, we have designed a class of short peptides to fold like proteins and assemble into defined nanostructures. In this talk, I will talk about new strategies to drive the self-assembled structures designing sequence of peptide. I will also discuss about the specific interaction between proteins and inorganics that can be used for the development of new hybrid solar energy devices. Splitting water into hydrogen and oxygen is one of the promising pathways for solar to energy convertsion and storage system. The oxygen evolution reaction (OER) has been regarded as a major bottleneck in the overall water splitting process due to the slow transfer rate of four electrons and the high activation energy barrier for O-O bond formation. In nature, there is a water oxidation complex (WOC) in photosystem II (PSII) comprised of the earthabundant elements Mn and Ca. The WOC in photosystem II, in the form of a cubical CaMn4O5 cluster, efficiently catalyzes water oxidation under neutral conditions with extremely low overpotential (~160 mV) and a high TOF number. The cluster is stabilized by a surrounding redox-active peptide ligand, and undergo successive changes in oxidation state by PCET (proton-coupled electron transfer) reaction with the peptide ligand. It is fundamental challenge to achieve a level of structural complexity and functionality that rivals that seen in the cubane Mn4CaO5 cluster and surrounding peptide in nature. In this presentation, I will present a new strategy to mimic the natural photosystem. The approach is based on the atomically defined assembly based on the short redox-active peptide sequences. Additionally, I will show a newly identified manganese based compound that is very close to manganese clusters in photosystem II.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.48 no.2
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• pp.87-95
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• 2022

This study is about the development of transparent cleansing water with one of the beta-hydroxy acids (BHA), salicylic acid, and capryloyl salicylic acid, which is one of the lipo-hydroxy acids (LHA). Transparent appearance was stabilized by increasing the solubility of lipophilic salicylic acid and capryloyl salicylic acid in water using ethanol, polyol, and sodium hydroxide, and supplementing suspension and deposition using a double micelle structure of two types of PEG surfactants. Cleansing water applied with this technology was developed, and makeup removing ability and skin texture improvement ability were confirmed using an optical camera and an image analyzer. This solubilization technology is proposed as a new approach of LHA, which has been difficult to apply due to its low solubility in water, and is expected to help in the development of new chemical peeling products.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4D
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• pp.671-678
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• 2006

In this study, to describe vehicle-structure dynamic interaction phenomena with 1/4 vehicle model, nonlinear Hertzian contact spring and nonlinear contact damper are adopted. The external loads acting on 1/4 vehicle model are selfweight of vehicle and geometry information of running surface. The constraint equation on contact surface is implemented by the Penalty method with stabilization and the reaction from constraint violation. To describe pitching motion of various vehicles two types of the displacement constraint equations are exerted to connect between car bodies and between bogie frames, i.e., the rigid body connection and the rigid body connection with pin, respectively. For the time integration of dynamic equations of vehicles and structure Newmark time integration scheme is adopted. To reduce the error caused by inadequate time step size, adaptive time-stepping technique is also adopted. Thus, it is expected that more versatile dynamic interaction phenomena can be described by this approach and it can be applied to various railway dynamic problems with low computational cost.

• Journal of the Korean Orthopaedic Association
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• v.56 no.5
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• pp.419-426
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• 2021

Purpose: In the surgical treatment of pyogenic lumbar spondylodiscitis, screw insertion at the affected vertebra has been avoided because of biofilm formation, and the risk of infection recurrence. The authors analyzed the success rate of infection treatment while minimizing the number of instrumented segments by inserting pedicle screws into the affected vertebrae. Therefore, this study examined the usefulness of this technique. Materials and Methods: From January 2000 to June 2018, among patients with pyogenic lumbar spondylodiscitis treated surgically, group A consisted of patients with pedicle screws inserted directly at the affected vertebrae (28 cases), and group B underwent fusion by inserting screws at the adjacent normal vertebrae due to bone destruction of the affected vertebral pedicle (20 cases). The classified clinical results were analyzed retrospectively. All patients were treated via the posterior-only approach, so the affected disc and sequestrum were removed. Posterior interbody fusion was performed with an autogenous strut bone graft, and the segments were then stabilized with pedicle screw systems. The hospitalization period, operation time, amount of blood loss, EQ-5D index, duration of intravenous antibiotics, and the clinical and radiological results were analyzed. Results: In group A, the number of instrumented segments, operation time, blood loss, and EQ-5D index at one month postoperatively showed significant improvement compared to group B. There were no significant differences in the duration of antibiotic use, hospitalization, radiological bone union time, sagittal angle correction rate, and recurrence rate. Conclusion: Minimal segmental fixation, in which pedicle screws were inserted directly into the affected vertebrae through the posterior approach, reduced the surgery time and blood loss, preserved the lumbar motion by minimizing fixed segments and showed rapid recovery without spreading or recurrence of infection. Therefore, this procedure recommended for the surgical treatment of lumbar pyogenic spondyodiscitis.

• Journal of the Korean Chemical Society
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• v.40 no.7
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• pp.474-482
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• 1996

Two crystal structures of the vacuum dehydrated $Ag^+$-exchanged zeolite X have been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd3 at 21(1)$^{\circ}C$ (a=24.922(1)${\AA}$ and a=24.901(1)${\AA}$, respectively). Each crystal was ion exchanged in flowing streams of aqueous $AgNO_3$ for three days. The first crystal was dehydrated at 300$^{\circ}C$ and $2{\times}10^{-6$torr for two days. The second crystal was similarly dehydrated at 350$^{\circ}C$. Their structures were refined to the final error indices, $R_1=0.095\;and\;R_2=0.092$ with 227 reflections, and $R_1=0.096\;and\;R_2=0.087$ with 334 reflections, respectively, for which I > 3${\sigma}$(I). In the first crystal, Ag species are found at five different crystallographic sites: sixteen $Ag^+$ ions fill the site I, the center of the double 6-ring, thirty-two Ag0 atoms fill the I' site in the sodalite cavities opposite double six-rings, seventeen $Ag^+$ ions lie at the 32-fold site II' inside the sodalite cavity at the single six-oxygen ring in the supercage, fifteen Ag+ ions lie at the 32-fold site II, in the supercage, and the remaining twelve $Ag^+$ ions lie at site III' in the supercage at a little off two-fold axes. In the second crystal, all Ag species are located similarly as crystal 1; 16 at site I, 28 at site I', 16 at site II, 16 at site II', 6 at site III and 6 at site III'. Total 88 silver species were found per unit cell. The remaining four Ag atoms were migrated out of the zeolite framework to form small silver crystallites on the surface of the zeolite single crystal. In the first structure, the numbers of Ag atoms per unit cell are approximately 32.0 and these may form tetrahedral $Ag_4$ clusters at the centers of the sodalite cavities. The probable four-atom cluster is stabilized by coordination to two $Ag^+$ ions. The Ag-Ag distance in the cluster, ca. 3.05 ${\AA}$, is a little longer than 2.89 ${\AA}$, Ag-Ag distance in silver metal. At least two six-ring $Ag^+$ ions on sodalite cavity (site II') must necessarily approach this cluster and this cluster may be viewed as a distorted octahedral silver cluster, (Ag6)2+.

• Journal of the Mineralogical Society of Korea
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• v.4 no.1
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• pp.22-31
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• 1991

Three crystal structures of dehydrated $Ag^+$-and $Ca^{2+}$- exchanged zeolite $A(Ag_4Ca_4-A,\;Ag_^Ca_3-A,\;and\;Ag_8Ca_2-A)$ treated at 250${\circ}C$ with 0.1 Torr of Rb vapor have been determined by single-crystal x-ray diffraction techniques in the cubic space group Pm3m at 21(1)${\circ}C$ (a=12,271(1)${\AA}$, 12.255(1)${\AA}$, and 12.339(1)${\AA}$, respectively). Their structures were refined to the final error indices. R(weighted) of 0.072 with 130 reflections, 0.050 with 110 reflections, and 0.083 with 86 reflections, respectively, for which $I>3{\rho}(I)$. In each structure, Rb species are found at three different crystallographic sites:3$Rb^+$+ions per unit cell are located at 8-ring centers, ca. 5.6 to 6.4 $Rb^+$ ions are found opposite 6-rings on threefold axes in the large cavity, and ca. 2.5 to 3.0 $Rb^+$ ions are found on threefold axes in the sodalite unit. Also, Ag species are found at two different crystallographic stites: ca. 0.7 to 2.1 $Ag^+$ lie opposite 4-rings and ca. 2.2 to 4.8 Ag atoms are located near the center of the large cavity. In these structures, the numbers of Ag atoms per unit cell are 2.2, 2.4, and 4.8, respectively, and these may form hexasilver clusters at the centers of the large cavities. The $Rb^+$ ions, by blocking 8-rings, may have prevented silver from migrating out of the structure. Each hexasilver cluster is stabilized by coordination to up to 13 $Rb^+$ions. An excess absorption of about 0.8 Rb atom per unit cell indicates that the presence of a triangular symmetric $(Rb_3)2^{+}$ cation in sodalite cavity. At least one large-cavity six-ring $Rb^+$ ion must necessarily approach this cluster and may be viewed as a member of it to give $(Rb)_4^{3+}$, $(Rb)_5^{4+}$ or $(Rb)_6^{5+}$.