• Polymer(Korea)
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• v.27 no.4
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• pp.377-384
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• 2003

High impact polystyrene/organically modified layered silicate (HIPS/OLS) nanocomposites by in situ polymerization were synthesized to investigate the effect of clay on the particle size and properties of rubber. In the OLS, the montmorillonite having benzyl group showed best dispersion in polystyrene phase. With the addition of clay, the intercalated peak from XRB was confirmed, but the peak gradually shifted to lower angle as rubber concentration increased. Thus, it is speculated that the organoclay disperses better in rubber phase than in polystyrene phase. The average rubber particle size increased and the particle size distribution widened as the amount of clay increased, which may be caused by the increase of the viscosity ratio of rubber to polystyrene phases and the unstable dispersion. The materials having clay showed improved thermal properties from thermogravimetric analysis. Rheological properties such as complex viscosity and storage modulus increased as the amount of clay increased.

• Journal of the Korean Chemical Society
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• v.41 no.9
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• pp.488-494
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• 1997

Lithium and sodium ions have been intercalated into two dimensional structure of $FeMoO_4Cl$. The electronic localization and the large difference in unit cell parameter between the pristine material and the intercalates lead to the existence of large biphased domains. In the case of the lithium system, a narrow range of $Li_xFeMoO_4Cl$ ($0.95{\leq}x{\leq}1.06$) solid solution has been found around the $LiFeMoO_4Cl$ composition. The OCV curve fitting has been performed using Armand's model. The occurrence of several parts in the charge-discharge curve is related to the electronic and structural modifications of the material during the intercalation process.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.18 no.3
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• pp.488-499
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• 1996

Diabetes mellitus revealed a chronic disorder of lipid, carbohydrate and protein metabolism characterized by insulin deficiency, and a striking tendency toward development of atherosclerosis, microangiopathy, nephropathy, neuropathy and recently cardiomyopathy etc. The mechanism of heart failure in patients with diabetic cardiomyopathy is not clear but diabetic cardiomyopathy usually occurs in persons with long standing diabetes. After diabetes induced in made Sprague- Dawley strain rats by injection of streptozotocin(60mg/kg), cardiac tissue with hematoxylin-eosin and Masson's trichrome stain was examined at 3 days, 1, 2, 4, 6 weeks later under light microscope. The results were obtained as follows : 1. In H&E stain of control group, myocardiac cells were shorter than skeletal muscle cell, which was branched out and connected each other at terminal with striation, intercalated disk and nucleus at center of cell. 2. In MT stain of control group, a few of collagen fibrile were seen at periva scular interstium, but wasn't seen between skeletal muscle fiber, and cardiac muscle was seen in various size. 3. In MT stain of experimental group, increased collagen fiber deposition at perivascular interstiums were seen periodically. 4. In MT stain of experimental group, increased collagen fiber deposition at interstitial matrix between perimyocardiac cells were seen at 3 day, 4 weeks and 6 weeks after DM induction. 5. In H&E stain of experimental group, partial degeneration of myocardiac cells was seen after 4 weeks of DM induction. From above results, streptozotocin induced diabetes mellitus increased collagen around perivascular and between intercellular matrix in heart.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.17 no.1
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• pp.123-135
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• 1987

The author observed the effects of retrograde infusion of water soluble contrast media (Tele- brix 30) on the rabbit submandibular glands and compared the effects of different degrees of filling. 26 rabbits were divided into 2 groups of 12 each as experimentals and I group of 2 as normal controls. One experimental group was filled with 0.2㎖ and the other with 0.4㎖. Right submandibular gland of each rabbit was infused with contrast media and left one with physiologic saline as a experimental control, at a constant rate of 0.12㎖/min. using an infusion pump via the main excretory duct. Immediately after the infusion of contrast media, oblique lateral radiographs of the glands were made with occlusal film in order to confirm the glandular filling. The rabbits were sacrificed after varying periods (1, 8, 24 hours and 3, 6, 10 days) and the tissues were prepared for light and electron microscopic examination. The results were as follows: 1. In glands filled with 0.2㎖ contrast media, the initial changes were a few vacuole formation in the acini and slight dilation of the intralobular duct. The moderately severe changes such as vacuole formation in the acini, the abnormal substructure within the secretory granule, dilation of acinar and intercalated duct lumen, scalloping of striated duct lumen and inflammatory cell infiltrate were observed at 3 days. The general appearance was successively recovered, so the tissue had a normal appearance at 10 days. 2. In glands filled with 0.4㎖ contrast media, the most prominent alterations such as severe acinar atrophy, decreased number of secretory granules, proliferation of connective tissue stroma and pronounced inflammatory cell infiltrates appeared at 6 days. Although the general appearance returned to be almost normal at 10 days, acinar cells showed some atrophy and decreased secretory granules. 3. In glands subjected to 0.4㎖ infusion, the alterations were more severe and the recovery was slower than those seen in the glands to 0.2㎖ infusion.

• Journal of the Korean Electrochemical Society
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• v.5 no.1
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• pp.1-6
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• 2002

Silver doped vanadium pentoxides with a doping ratio Ag/V ranging from 0.03 to 0.11 were synthesized by sol-gel process, and $Li/Ag_xV_2O_5$ cell was investigated by the electrochemical methods. It appears to be amorphous layered material and entangled fibrous textures has been grown to form anisotropic corrugated fibrils. NMR measurements revealed that several different kinds of $Li^+$ ions exist in the lithium intercalated xerogel electrodes and the average cell potential was about 3.0V vs. $Li/Li^+$. The cell capacity of the silver doped $Ag_xV_2O_5$ xerogel cathodes was more than 359 mAh/g at discharge current 10mA/g and cycle efficiency $94\%$ was achieved.

• Applied Microscopy
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• v.20 no.2
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• pp.127-159
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• 1990

This study was investigated to elucidate the effect of chlorambucil on the heart in aging rats. Male rat ranging in age from 3 to 36 months were used. Each age groups(3, 6, 12, 18, 24, 36 months) included control and chlorambucil treated rats. As a part of the study, the ultrastructural changes in the left ventricular myocardial cells were described by using the qualitative and morphometric techniques. The results are summarized as follows. Age associated ultrastructural changes included: an increase in vacuoles, protrusion of plasma membranes, lipid droplets, and lipofuscins in myocardium of control groups. These changes which begin to occur at 12 months and continue through 36 months. At the 36 months some instance of unusual formation of contraction band and separation of intercalated discs were encountered. Morever, these changes and contents with chlorambucil treatment were remarkably increased in comparison with control groups. Age-dependent changes of control group measured with morphometry were not observed in the volume densities of mitochondria and myofibrils. But there was increase in interstitium. On the other hand decrease in sarcoplasmic reticulum and T-tubule system. In chlorambucil treated groups, volume densities of mitochondria and interstitium were increased in comparison with those of the control groups. But sarcoplasmic reticulum and T-tubule system were remarkably decreased.

• Polymer(Korea)
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• v.25 no.5
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• pp.691-698
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• 2001

Nanocomposites based on epoxy acid nanoclay were prepared employing organically modified mica type silicate (OMTS), diglycidyl ether of bisphenol A (DGEBA) type epoxy. curing agent (dicyandiamide; DICY), and catalyst (benzyl dimethyl amine; BDMA). Both melt mixing and solution mixing were und for the sample preparation and structural developments with curing reaction were analyzed using X-ray diffractometer (XRD) and small angle X-ray scattering (SAXS). Because of the different curing rate between extra-gallery and intra-gallery reactions of epoxy mixtures, only intercalated structure was observed for the sample prepared by melt mixing while fully exfoliated structure was observed for the sample prepared by solution mixing. Mechanical properties of exfoliated epoxy nanocomposite were investigated using a dynamic mechanical analyzer (DMA). The dynamic storage modulus of the nanocomposite in both glass and rubbery plateau regions were increased with increasing OMTS contents, but glass transition temperatures ($T_g$) remained unchanged. Thermal properties of epoxy nanocomposite were investigated using thermogravimetric (TGA) and limit oxygen index (LOI) methods. Thermal decomposition onset points and LOI values were increased with increasing OMTS contents due to barrier effects of OMTS sheets.

• Polymer(Korea)
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• v.24 no.4
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• pp.571-577
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• 2000

A new type of filler for epoxy-clay nanocomposites has been prepared by the reaction of octadecyltrimethylammonium bromide and layered sodium montmorillonite (MMT) via an ion-exchange reaction. The gallery space was further modified by grafting the aminopropyl groups via a reaction between a octadecyltrimethylammonium-MMT and 3-aminopropyltriethoxysilane (APS). The interlayer modification of MMT was confirmed by XRD, IR, and solid-state $^{29}$ Si CP/MAS NMR. Furthermore, clay-polymer nanocomposites have been synthesized by the polymerization of diglycidyl ether of bisphenol A(DGEBA) and $C_{18}$ H$_{37}$ N($CH_3$)$_3$-APS-MMT. The resulting hybrid nanocomposites were characterized by XRD, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The results proved that the organomontmorillonite could be exfoliated and uniformly dispersed in the epoxy matrix.

• BMB Reports
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• v.38 no.1
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• pp.104-110
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• 2005

We extended the measurable time scale of DNA dynamics to microsecond using $[Ru(phen)_2(dppz)]^{2+}$ (phen = 1,10-phenanthroline, dppz = dipyrido[3,2-a:2',3'-c]phenazine) (RuPD), which displays a mean lifetime near 500 ns. To evaluate the usefulness of this luminophore (RuPD) for probing nucleic acid dynamics, its intensity and anisotropy decays when intercalated into supercoiled and linear pBluescript (pBS) II SK(+) phagemids were examined using frequency-domain fluorometry with a blue light-emitting diode (LED) as the modulated light source. The mean lifetime for the supercoiled phagemids (< $\tau$ > = 489.7 ns) was somewhat shorter than that for the linear phagemids (< $\tau$ > = 506.4 ns), suggesting a more efficient shielding from water by the linear phagemids. The anisotropy decay data also showed somewhat shorter slow rotational correlation times for supercoiled phagemids (997.2 ns) than for the linear phagemids (1175.6 ns). The slow and fast rotational correlation times appear to be consistent with the bending and torsional motions of the phagemids, respectively. These results indicate that RuPD can have applications in studies of both bending and torsional dynamics of nucleic acids.

• Applied Chemistry for Engineering
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• v.16 no.3
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• pp.337-341
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• 2005

This paper reports the study on coking rate and carbon formation route as a function of reaction temperature using the Ni catalysts in the $CO_2$ reforming of methane. In this paper, carbon deposition on catalysts and its kinetics during reforming reaction were studied by using a thermogravimetric analyzer. Kinetic studies show that reaction orders of carbon formation obtained 1.33 ($CH_4$) and -0.52 ($CO_2$) by experiments on partial pressure of reactant gas, respectively. On the basis of model equation, the kinetic parameters for the coking reaction at different temperatures indicated that methane decomposition dominated carbon formation at lower temperatures ($<600^{\circ}C$), while $CH_4$decomposition and Boudouard reactions become significant for coking in the temperature range of $600{\sim}700^{\circ}C$.