Time filter

Source Type

Andong, South Korea

Andong National University is a government-operated university in Andong City, North Gyeongsang province, South Korea. It enrolls roughly 6500 students. It contains undergraduate colleges of Humanities, Social science, Education, Natural science, Engineering, Human Ecology, and Arts and Physical Education, as well as graduate schools of Education, Management, and General Studies. The undergraduate students of March 2006 numbered 10,274, representing a steady upward trend in recent years, according to the school website . Wikipedia.

BACKGROUND: Ginger leaf (GL) has long been used as a vegetable, tea and herbal medicine. However, its pharmacological properties are still poorly understood. Thus, we performed in vitro studies to evaluate anti-cancer properties of ginger leaf and then elucidate the potential mechanisms involved.METHODS: Cell viability was measured by MTT assay. ATF3 expression level was evaluated by Western blot or RT-PCR and ATF3 transcriptional activity was determined using a dual-luciferase assay kit after the transfection of ATF3 promoter constructs. In addition, ATF3-dependent apoptosis was evaluated by Western blot after ATF3 knockdown using ATF3 siRNA.RESULTS: Exposure of GL to human colorectal cancer cells (HCT116, SW480 and LoVo cells) reduced the cell viability and induced apoptosis in a dose-dependent manner. In addition, GL reduced cell viability in MCF-7, MDA-MB-231 and HepG-2 cells. ATF3 knockdown attenuated GL-mediated apoptosis. GL increased activating transcription factor 3 (ATF3) expressions in both protein and mRNA level and activated ATF3 promoter activity, indicating transcriptional activation of ATF3 gene by GL. In addition, our data showed that GL-responsible sites might be between -318 and -85 region of the ATF3 promoter. We also observed that ERK1/2 inhibition by PD98059 attenuated GL-mediated ATF3 expression but not p38 inhibition by SB203580, indicating ERK1/2 pathway implicated in GL-induced ATF3 activation.CONCLUSIONS: These findings suggest that the reduction of cell viability and apoptosis by GL may be a result of ATF3 promoter activation and subsequent increase of ATF3 expression through ERK1/2 activation in human colorectal cancer cells. Source

In this paper, we examine an efficient calculation of the approximate frequency response (FR) for large-size finite element (FE) models using the Krylov subspace-based model order reduction (MOR) and its direct design sensitivity analysis with respect to design variables for sizing. Information about both the FR and its design sensitivity is necessary for typical gradient-based optimization iterations; therefore, the problem of high computational cost may occur when FRs of a large-size FE models are involved in the optimization problem. In the method suggested in this paper, reduced order models, generated from the original full-order FE models through the Arnoldi process, are used to calculate both the FR and FR sensitivity. This maximizes the speed of numerical computation of the FR and its design sensitivity. Assuming that the Krylov basis vectors remain constant with respect to the perturbation of a design variable, the FR sensitivity analysis is performed in a more efficient manner. As numerical examples, a car body with 535,992 degrees of freedom (DOF) and a 6 × 6 micro-resonator array with 368,424 DOF are adopted to demonstrate the numerical accuracy and efficiency of the suggested approach. Using the reduced-order models, we found that the FR and FR sensitivity are in a good agreement with those using the fullorder FE model. The reduction in computation time is also found to be significant because of the use of Krylov subspace-based reduced models. © 2012 The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg. Source

Shin H.-S.,Andong National University
Journal of Alloys and Compounds | Year: 2014

A small-scale joining technique for dissimilar friction stir spot welding (FSSW) of a BMG alloy to lightweight crystalline alloys has been developed. An experimental apparatus which could possible give a precise control of the friction time, the plunge speed and the plunge depth of the tool was used. In this study, the influences of tool geometry with different pin shape on the joining characteristics and on the failure load of specimens after dissimilar FSSW were investigated. As a result, it was found that the tool geometry influenced on the welding performance of the BMG alloy to lightweight crystalline alloys at small tool plunge depth and the extent of BMG particles penetrated onto the lightweight alloy side, especially for the Mg alloy/BMG material combination. © 2012 Elsevier B.V. All rights reserved. Source

Hwang H.Y.,Andong National University
Journal of Composite Materials | Year: 2011

Several researches on nondestructive damage monitoring of composite materials by piezoelectric method had been conducted recently, and concluded that the piezoelectric method can be useful for glass fiber epoxy composites. However, few studies were performed about piezoelectric properties of composites despite the importance for analyses of the electro-mechanical coupling systems. Therefore, in this study, the effect of strain rate on the piezoelectric characteristics of unidirectional glass fiber epoxy composites (UGFEC) was investigated. Under various strain rates, stress-strain curve and charge output signal from composite specimens were obtained by experiments. From experimental results, through-thickness modulus increased but electric charge output decreased linearly by increasing the strain in log scale. And piezoelectric strain constant of UGFEC was almost same while piezoelectric stress constant decreased with respect to the strain rate. From the results, it was concluded that electric charge output of UGFEC is influenced by the strain itself rather than by the strain rate. © The Author(s) 2010. Source

Jeong G.Y.,Andong National University | Achterberg E.P.,Leibniz Institute of Marine Science
Atmospheric Chemistry and Physics | Year: 2014

Mineral dust supplied to remote ocean regions stimulates phytoplankton growth through delivery of micronutrients, notably iron (Fe). Although attention is usually paid to Fe (hydr)oxides as major sources of available Fe, Fe-bearing clay minerals are typically the dominant phase in mineral dust. The mineralogy and chemistry of clay minerals in dust particles, however, are largely unknown. We conducted microscopic identification and chemical analysis of the clay minerals in Asian and Saharan dust particles. Cross-sectional slices of dust particles were prepared by focused ion beam (FIB) techniques and analyzed by transmission electron microscopy (TEM) combined with energy dispersive X-ray spectroscopy (EDXS). TEM images of FIB slices revealed that clay minerals occurred as either nanothin platelets or relatively thick plates. Chemical compositions and lattice fringes of the nano-thin platelets suggested that they included illite, smectite, illite-smectite mixed layers, and their nanoscale mixtures (illite-smectite series clay minerals, ISCMs) which could not be resolved with an electron microbeam. EDXS chemical analysis of the clay mineral grains revealed that the average Fe content was 5.8% in nano-thin ISCM platelets assuming 14% H2O, while the Fe content of illite and chlorite was 2.8 and 14.8 %, respectively. In addition, TEM and EDXS analyses were performed on clay mineral grains dispersed and loaded on micro-grids. The average Fe content of clay mineral grains was 6.7 and 5.4% in Asian and Saharan dusts, respectively. A comparative X-ray diffraction analysis of bulk dusts showed that Saharan dust was more enriched in clay minerals than Asian dust, while Asian dust was more enriched in chlorite. Clay minerals, in particular nanocrystalline ISCMs and Fe-rich chlorite, are probably important sources of Fe to remote marine ecosystems. Further detailed analyses of the mineralogy and chemistry of clay minerals in global mineral dusts are required to evaluate the inputs of Fe to surface ocean microbial communities. © Author(s) 2014. Source

Discover hidden collaborations