• Journal of Microbiology and Biotechnology
• /
• v.13 no.5
• /
• pp.666-672
• /
• 2003

Vacuolar degeneration of the gastric epithelial cells is a characteristic feature of the derangement of mucosa where Helicobacter pylori colonizes, and H. pylori vacuolating cytotoxin (VacA) has been suggested to playa key role in it. To elucidate the VacA-involved degenerative mechanism, VacA was purified, and its impact on degeneration of HeLa cells was determined. In the presence of ammonium chloride, cell vacuolation by VacA was dose-and time-dependent, however, no detectable degeneration of the cells was observed with the VacA concentration tested. A further increase of vacuolation was shown in cells pre-treated with diethyl pyrocarbonate (DEPC) , and this resulted in a change of the cell morphology to become spherical. Similar phenomena were also observed when HeLa cells were co-cultivated with intact H. pylori cells. It was remarkable to note that the degree of growth inhibition was proportional to the increase in vacuole formation, suggesting that the vacuolation rate would be critical for cell degeneration. Surprisingly, although VacA was itself inhibited by DEPC, its uptake was markedly increased by this agent, similar to that found in cells with Nabutyrate. These data indicate that the cell's tolerance of VacA transport may be critical for vacuolar degeneration and may be changeable during H. pylori inhabitation.

• Environmental Engineering Research
• /
• v.25 no.1
• /
• pp.71-79
• /
• 2020

This paper uses super-efficiency DEA model and Malmquist index to evaluate the carbon emission efficiency (CEE) values of the nine western provinces along the "Silk Road Economic Belt" for the period from 2000 to 2015, and analyses the influencing factors of the CEE. The major findings of this study are the following: (1) the overall CEE of the nine western provinces is not high, and there are significant inter-provincial differences in the CEE. Meanwhile, the provinces with higher levels of economic development generally have higher CEE. (2) The annual total factor productivity (TFP) of the nine western provinces, which is mainly determined by technological change, is greater than 1. Moreover, the total average growth rate of the TFP is 15.5%. (3) The CEE of the nine western provinces is not spatially dependent. In addition, the urbanization, openness, use of energy-saving technologies and research and development (R&D) investment have a significant positive impact on the CEE values, while the industrial structure, foreign direct investment, fixed asset investment, government expenditure levels and energy structure have a significant negative impact on the CEE. Among them, R&D investment is the primary factor in promoting the development of CEE, and the government expenditure has the greatest negative impact on the CEE.

• Journal of the Korean Magnetic Resonance Society
• /
• v.3 no.1
• /
• pp.44-51
• /
• 1999

An enzyme derived conformational changes of cobalamine is thought to be important in the homolytic cleavage of Co-C bond which is the first step of catalytic Cl-cycle of coenzyme B12-dependent enzymes. Modern 2D-NMR and NMR-based distance geometric studies were carried out to determine the 3D structure of corrin ring. Homonuclear and heteronuclear correlation NMR experiments were performed for complete 1H-NMR signal assignments. Distances between numerous proton pairs were deduced based on the NOE cross peak intensities and subsequently used as input into the distance geometry program for the 3D structure determination. The detailed 3D structure from the present NMR-based analysis was compared with the result from X-ray crystallographic study, which revealed greater conformational changes occur in benzimidazole group and sugar ring than in macrocyclic corrin and tetrapyrrole. In addition, the distance geometry used in this study was found to be quite useful for NMR-based structure determination of medium-sized molecules that give poor NOE effects arising from their intermediate tumbling rate ($\omega$$\tau$c 1.0).

• Journal of the Korean Professional Engineers Association
• /
• v.42 no.4
• /
• pp.45-50
• /
• 2009

The modal split structure of the Korea's transportation system has been dominated by road-oriented structure. The shortage of the inftrastructure to accommodate the rapidly increasing travel demand has brought about socio-economic losses such as severe traffic congestion and high logistic costs, and thereby weakened the competitiveness of the country. Highway transportation sector is more vulnerable to energy consumption comparing with railway sector since the highway sector is dependent mostly on fossil fuels for its energy source. In 2006 annual road cogestion costs in Korea reached 24.6 trillion won, with an average annual growth rate of 5.4%. The annual road congestion cost of intercity highways were 9.2 trillion won. As the new cities that recently developed are located far from Seoul area, the boundary of commuting in Seoul metropolitan area is extended. It makes passengers have longer trips with longer travel time, and the congestion problem to be more serious. In this regards, Gyeonggi Provincial Government proposed a deeper underground metropolitan express train system for the greater Metropolitan area. which is named as GTX. Gyeonggi Province suggested 3 key underground lines, based on the outcome of the feasibility study conducted by the Korea Society of Transportation, and submitted to the Ministry of Land Transportation and Maritime Affairs for its review. If the project is approved for construction and completed in 2016, the daily volume of surface traffic bound for Seoul will be reduced substantially and therefore the users will be benefitted for time savings by an annual amount of 2 trilion won every year.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1998.11a
• /
• pp.339-342
• /
• 1998

Ferroelectric L $a_2$ $Ti_2$ $O_{7}$(LTO) thin films were prepared by chemical solution deposition processes. Acetylacetone was used as chelating agent and nitric acid was added in the stock solution to control hydrolysis and condensation reaction rate. The LTO thin films were spin-coated on Pt/Ti/ $SiO_2$/(100)Si and Pt/Zr $O_2$/ $SiO_2$/(100)Si substrates. After multiple coating, dried thin films were heat-treated for decomposition of residual organics and crystallization. The role of acetylacetone in Ti iso-propoxide stabilization by possibly substituting $O^{i}$Pr ligand was studied by H-NMR. B site-rich impurity phase, i.e. L $a_4$ $Ti_{9}$ $O_{24}$, was found after annealing, where its appearance was dependent on process temperature indicating the possible reaction with substrate. Dielectric and other relevant electrical properties were measured and the results were compared between modified sol-gel and MOD processes.s.s.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1997.04a
• /
• pp.183-187
• /
• 1997

The Thin films were obtained by plasma polymerization of phenyl isothiocyanate. Polymerizations were carried out in rf(13.56 [MHz]) glow discharge generated in an inter-electrode capacitively coupled gas flow system. It was fecund that this monomer produces uniform films with a wide range of thicknesses, from hundreds of nanometers to tens of micrometers. The deposition rate appeared to be dependent on the substrate distance from the monomer inlet. The IR data revealed significant decrease in -NCS groups content in the polymer as compared with the monomer spectrum and indicated for the appearance of new absorption bands corresponding to the -CN and C-H aliphatic groups. The soluble fraction by GC was found to be composed of numerous low molecular-weight compounds.

• Archives of Pharmacal Research
• /
• v.13 no.1
• /
• pp.55-63
• /
• 1990

An attempt was made to investigate the effect of intracerebroventricular 5-hydroxytrypatamine (5-HT) on the cardiovascular system in urethane-anesthetized rabbit and to elucidate the mechanism of its action. 5-HT given into a lateral ventricle caused clearly a dose-dependent decrease inboth arterial blood pressure and in heart rate. The bradycardia and hypotension induced by 5-HT were significantly attenuated by the prior injection of ketanserin, cyproheptadine or clonidine. Pretreatment of atropine with bilateral vagotomy did not affect both bradycardia and hypotension. Propranolol weakened markedly the breadcardia of 5-HT but did not influence the depressor response of 5-HT. These experimental results suggest that intraventricular 5-HT cause the hypotension and bradyardia in rabbits through the stimulation of serotonergic receptors in brain, which is seemed to be associated to inhibition of sympathetic tone.

• Macromolecular Research
• /
• v.14 no.2
• /
• pp.155-165
• /
• 2006

The present article describes the experimental and theoretical observations on the formation of holographic, polymer-dispersed, liquid crystals and electrically switchable, photonic crystals. A phase diagram of the starting mixture of nematic liquid crystal and photo-reactive triacrylate monomer was established by means of differential scanning calorimetry (DSC) and cloud point measurement. Photolithographic patterns were imprinted on the starting mixture of LC/triacrylate via multi-beam interference. A similar study was extended to a dendrimer/photocurative mixture as well as to a single component system (tetra-acrylate). Theoretical modeling and numerical simulation were carried out based on the combination of Flory-Huggins free energy of mixing and Maier-Saupe free energy of nematic ordering. The combined free energy densities were incorporated into the time-dependent Ginzburg-Landau (Model C) equations coupled with the photopolymerization rate equation to elucidate the spatio-temporal structure growth. The 2-D photonic structures thus simulated were consistent with the experimental observations. Furthermore, 3-D simulation was performed to guide the fabrication of assorted photonic crystals under various beam-geometries. Electro-optical performance such as diffraction efficiency was evaluated during the pattern photopolymerization process and also as a function of driving voltage.

• Macromolecular Research
• /
• v.17 no.12
• /
• pp.1010-1014
• /
• 2009

Monodispersed microparticles with a poly(D,L-lactide-co-glycolide) (PLGA) core and a poly(ethyl 2-cyanoacrylate) (PE2CA) shell were prepared by Shirasu porous glass (SPG) membrane emulsification to reduce the initial burst release of doxorubicin (DOX). Solution mixtures with different weight ratios of PLGA polymer and E2CA monomer were permeated under pressure through an SPG membrane with $1.9\;{\mu}m$ pore size into a continuous water phase with sodium lauryl sulfate as a surfactant. Core-shell structured microparticles were formed by the mechanism of anionic interfacial polymerization of E2CA and precipitation of both polymers. The average diameter of the resulting microparticles with various PLGA:E2CA ratios ranged from 1.42 to $2.73\;{\mu}m$. The morphology and core-shell structure of the microparticles were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The DOX release profiles revealed that the microparticles with an equivalent PLGA:E2CA weight ratio of 1:1 exhibited the optimal condition to reduce the initial burst of DOX. The initial release rate of DOX was dependent on the PLGA:E2CA ratio, and was minimized at a 1:1 ratio.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1996.05c
• /
• pp.145-150
• /
• 1996

Acoustic Emission (AE) technique was applied to stress corrosion cracking of Inconel 600 to investigate the AE capability of detecting crack growth and to obtain the relation between AE characteristics and crack mechanism. The specimens were heat-treated in two conditions (600$^{\circ}C$ for 30 hrs or 700 $^{\circ}C$ for 1 hr) and undergone CERT at two extension rates ( 2.5${\times}$10$^{-5}$ or 1.25${\times}$10$^{－4}$(mm/s)). It was found that the AE peak amplitude from plastic deformation was generally smaller than about 48dB (0.25mV), while Intergranular stress corrosion cracking (IGSCC) and ductile fracture produced higher values of 49 to 70dB (0.3mV to 3mV). The slopes of cumulative amplitude distribution (b-values) were linearly dependent on IGSCC susceptibility and the higher the susceptibility, the smaller the b-value. The monitoring of combined AE parameters such as event rate, amplitude, count and energy can provide effective means to clearly identify the transition from crack initiation and small crack growth to rapid growth of dominant cracks.