• Analytical Science and Technology
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• v.28 no.1
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• pp.33-39
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• 2015

CdS-QD particles are a nano-sized semiconducting crystal that emits light. Their optical properties show great potential in many areas of applications such as disease-diagnostic reagents, optical technologies, media industries and solar cells. The wavelength of emitting light depends on the particle size and thus the quality control of CdS-QD particle requires accurate determination of the size distribution. In this study, CdS-QD particles were synthesized by a simple ${\gamma}$-ray irradiation method. As a particle stabilizer polyvinyl pyrrolidone (PVP) were added. In order to determine the size and size distribution of the CdS-QD particles, sedimentation field-flow fractionation (SdFFF) was employed. Effects of carious parameters including the the flow rate, external field strength, and field programming conditions were investigated to optimize SdFFF for analysis of CdS-QD particles. The Transmission electron microscopy (TEM) analysis show the primary single particle size was ~4 nm, TEM images indicate that the primarty particles were aggregated to form secondary particles having the mean size of about 159 nm. As the concentration of the stabilizer increases, the particle size tends to decrease. Mean size determined by SdFFF, TEM, and dynamic light scattering (DLS) were 126, 159, and 152 nm, respectively. Results showed SdFFF may become a useful tool for determination of the size and its distribution of various types of inorganic particles.

• Journal of Periodontal and Implant Science
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• v.38 no.sup2
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• pp.373-384
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• 2008

Purpose: The aim of this study is to compare the healing response of various Hydroxyapatite(HA) coated dental implants by Ion-Beam Assisted Deposition(IBAD) placed in the surgically created circumferential gap in dogs. Materials and methods: In four mongrel dogs, all mandibular premolars and the first molar were extracted. After an 8 weeks healing period, six submerged type implants were placed and the circumferential cylindrical 2mm coronal defects around the implants were made surgically with customized step drills. Groups were divided into six groups : anodized surface, anodized surface with 150nm HA and heat treatment, anodized surface with 300nm HA and heat treatment, anodized surface with 150nm HA and no heat treatment, and anodized surface with 150nm HA, heat treatment and bone graft, anodized surface with bone graft. The dogs were sacrificed following 12 weeks healing period. Specimens were analyzed histologically and histomorphometrically. Results: During the healing period, healing was uneventful and implants were well maintained. Anodized surface with HA coating and $430^{\circ}C$ heat treatment showed an improved regenerative characteristics. Most of the gaps were filled with newly regenerated bone. The implant surface was covered with bone layer as base for intensive bone formation and remodeling. In case that graft the alloplastic material to the gaps, most of the coronal gaps were filled with newly formed bone and remaining graft particles. The bone-implant contact and bone density parameters showed similar results with the histological findings. The bone graft group presented the best bone-implant contact value which had statistical significance. Conclusion: Within the scope of this study, nano-scale HA coated dental implants appeared to have significant effect on the development of new bone formation. And additional bone graft is an effective method in overcoming the gaps around the implants.

• Nuclear Engineering and Technology
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• v.5 no.1
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• pp.30-37
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• 1973

The Nishitani's equations for impedance of anodic oxide films have been derived based on a p-i-n model under the assumption of $\omega$$\varepsilon$$\rho$$_{ο}$<<4$\pi$<<$\omega$$\varepsilon$$\rho$$_{\omega}$, where $\omega$ is angular frequency, $\varepsilon$ is dielectric constant, and $\rho$$_{ο}$ and $\rho$$_{\omega}$ are the resistivity of the interface region and the intrisic region of the anodic oxide film, respectively. Since it is not possible to evaluate all parameters in the equations, however, any clear physical picture cannot be obtained from the equations. Therefore, the equations are modified under the assumption of $\omega$$\tau$$_{\omega}$>>1 and In(1+$\omega$$^2$$\tau$$_{ο}$$^2$)<<1, where $\tau$$_{\omega}$=$\varepsilon$$\rho$$_{\omega}$(4$\pi$) and $\tau$$_{ο}$=$\varepsilon$$\rho$$_{ο}$/(4$\pi$). The modified equations are then used to explain the change in the frequency characteristics of anodic oxide films when they are heated. The change in impedance of anodic oxide films when they are heated is attributed mainly to the increase in the diffusion layer and to the decrease in the resistivity of anodic oxide films.s.

• Food Science and Preservation
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• v.12 no.1
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• pp.48-53
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• 2005

Comparative effects between commercial fumigation (methyl bromide/MeBr, phosphine $gas/PH_3$) and gamma irradiation (5, 10 kGy) on dried red pepper were investigated in terms of it microbiological quality, moisture content Hunter's colors, and UV-visible spectra during storage for 8 months at mom temperature. The non-treated control samples showed total aerobic bacteria as $4.8\times10^5\;CFU/g$ in powdered state and $1.8\times10^2\;CFU/g$ in whole red repper. While yeasts and molds were $1.7\times10^5\;CFU/g$ in powdered pepper and $5.0\times10^2\;CFU/g$ in whole pepper, respectively. The effect of chemical fumigant on microbial decontamination was negligible, whereas irradiation at 5 kGy was proven to reduce the microbial populations by 2 to 3 log cycles that could improve the hygienic quality of powdered pepper. Moisture content of the samples showed no noticeable changes resulting 1mm irradiation or fumigation. Immediately after treatments, irradiation or fumigation reduced Hunter's lightness (L), redness (a), and yellowness (b) of the samples (p<0.05), but there was no difference in color parameters between the control and all treated stoups after 4 months of storage. It was found that storage period was more influential than irradiation or fumigation to changes in moisture and color of dried red pepper and ie powder.

• Journal of the Korean Chemical Society
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• v.17 no.2
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• pp.105-114
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• 1973

The crystal structure of morpholinothiosemicarbazide has been determined by single crystal X-ray analysis. The lattice constants are a = 4.19(2), b = 6.56(2) and c = 26.67(4)${\AA}$. The unit cell contains 4 molecules and the space group is$P2_12_12_1$. The atomic parameters have been refined by least-squares method to a final R value of 0.07, based on the 651 observed reflexions. The amino nitrogen atom forms hydrogen bonds to the sulfur atoms of the other molecules related by the two-fold screw axis parallel to the a-axis, the distances of the hydrogen bonds being 3.48 and 3.49${\AA}$. On the other hand, the imino nitrogen atom forms a hydrogen bond to the amino nitrogen atom of the other molecule related by the two-fold screw axis parallel to the a-axis, the distance of the hydrogen bond being 3.04${\AA}$. These three hydrogen bonds arrange the molecules around the two-fold screw axis. Apart from the hydrogen bonding system the structure is held together by van der Waals forces.

• Nuclear Engineering and Technology
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• v.6 no.1
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• pp.14-22
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• 1974

Effects of anodization voltage on frequency characteristics of anodic oxide films on tantalum were analyzed based on the following impedance equatious : (equation omitted) Here $R_{f}$, $C_{f}$ and tan $\delta$$_{f}$ are equivalent series resistance in ohm, equivalent Belies capacitance in farad and dielectric loss, of anodic oxide films respectively Parameters P, $\tau$$_{ο}$, $\tau$$_{\omega}$, and Co are defined as follows: P=(d-w)/w, $\tau$$_{ο}$=$textsc{k}$$\rho$$_{ο}$, $\tau$$_{\omega}$=$textsc{k}$$\rho$$_{\omega}$, $C_{ο}$=$textsc{k}$A/d where d is the thickness of oxide film, $\omega$ is the diffusion layer thickness. $\rho$$_{ο}$ is the resistivity of oxide film at the interface of metal and the oxide, $\rho$$_{\omega}$ is the resistivity of oxide film at intrinsic region and A is the area of the film and $textsc{k}$=0.0885$\times$10$^{-12}$ $\times$dielectric constant, (in farad/cm). It was shown that dielectric loss and frequency dependence of equivalent series capacitance decrease as anodization voltage increases. This is a consequence of the fact that the thickness of diffusion layer increases a little with increasing anodization voltage whereas the total oxide thickness is proportional to the anodization voltage. The ngative deviation of measured values from tile relation, tan $\delta$$_{f}$=0.682 $\Delta$ $C_{f}$, was also discussed based on the Impedance equations given above. Here $\Delta$ $C_{f}$ is the change in capacitance between 0.1 and 1 KHZ.KHZ.Z.

• Archives of Pharmacal Research
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• v.28 no.7
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• pp.791-798
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• 2005

The hepatoprotective activity of flavonol glycosides rich fraction (F-2), prepared from 70% alcohol extract of the aerial parts of V calcarata Desf., was evaluated in a rat model with a liver injury induced by daily oral administration of $CCl_4$ (100 mg/kg, b.w) for four weeks. Treatment of the animals with F-2 using a dose of (25 mg/kg, b.w) during the induction of hepatic damage by $CCl_4$ significantly reduced the indices of liver injuries. The hepatoprotective effects of F-2 significantly reduced the elevated levels of the following serum enzymes: alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH). The antioxidant activity of F-2 markedly ameliorated the antioxidant parameters including glutathione (GSH) content, glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), plasma catalase (CAT) and packed erythrocytes glucose-6-phosphate dehydrogenase (G6PDH) to be comparable with normal control levels. In addition, it normalized liver malondialdehyde (MDA) levels and creatinine concentration. Chromatographic purification of F-2 resulted in the isolation of two flavonol glycosides that rarely occur in the plant kingdom, identified as quercetin-3,5-di-O-$\beta$-D-diglucoside (5) and kaempferol-3,5-di-O-$\beta$-D-diglucoside (4) in addition to the three known compounds identified as quercetin-3-O-$\alpha$-L-rhamnosyl- (${\rightarrow}6$)-$\beta$-D-glucoside [rutin, 3], quercetin-3-O-$\beta$-D-glucoside [isoquercitrin, 2] and kaempferol-3-O-$\beta$-D-glucoside [astragalin, 1]. These compounds were identified based on interpretation of their physical, chemical, and spectral data. Moreover, the spectrophotometric estimation of the flavonoids content revealed that the aerial parts of the plant contain an appreciable amount of flavonoids (0.89%) calculated as rutin. The data obtained from this study revealed that the flavonol glycosides of F-2 protect the rat liver from hepatic damage induced by $CCl_4$ through inhibition of lipid peroxidation caused by $CCl_4$ reactive free radicals.

• Analytical Science and Technology
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• v.15 no.6
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• pp.502-508
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• 2002

See-through hollow cathode glow discharge cell has been developed for the trace analysis of metal ions. The systems consists of new glow discharge cell improved the cooling system. In the case of previous type of hollow cathode glow discharge cell, it had been utilized for the trace analysis of metal ions but it had a problem that the plasma becomes unstable by air-cooled device. In this study, the modified hollow cathode glow discharge cell has been developed in order to minimize the problem associated with the air-cooled device. thus the stability of the plasma with water-cooling device has been improved and also the higher plasma temperature has been measured. The fundamental characteristics of modified systems have been investigated. And the discharge parameters, such as discharge pressure, material, and diameter of cathode, have been studied to find optimum discharge conditions.

• Analytical Science and Technology
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• v.15 no.6
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• pp.514-520
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• 2002

The electrothermal vaporization (ETV) hollow cathode glow discharge atomic emission spectrometer for analysis of liquid sample has been developed and characterized. This system has improved the sample introduction method of electrothermal vaporization and the hollow cathode glow discharge. The sample introduction method was possible to provide high analyte transport efficiency to the plasma by helix coil made of tungsten material. In addition, small volume samples (<$30{\mu}{\ell}$) could be used. The system has glow discharge cell with special design for improvement of precision. The effect of discharge parameters such as discharge power, gas flow rate has been studied to find optimum condition. The emitted light was effectively carried into detector by fiber optic cable in UV region. The calibration curve of Pb, Cd were obtained with 3 samples.

• Nuclear Engineering and Technology
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• v.11 no.4
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• pp.263-274
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• 1979

A statistical approach is used to investigate the relative economic advantages of pressurized water reactor (PWR) and pressurized heavy water reactor (PHWR-CANDU) nuclear power plants for hypothetical 900Mwe systems with the throwaway fuel cycle to be built in the Republic of Korea. Power cost is decomposed into the cost components related to the plant capital, operation and maintenance, working capital requirements and fuel cycle operation. The calculation of construction cost is performed with the modified version of computer code ORCOST, and the modified POWERCO-50 is used to evaluate the cost components. Most of economic parameters are treated as statistical variables, each being given with a certain range. Through a random sampling procedures. the probability histograms on unit plant construction costs and power generating costs are obtained. The power cost probability histograms of the PWR and the PHWR plants overlap considerably, and the power costs of two systems appear to be almost same with the PHWR power cost being 0.4mil1/kwh lower compared with 39.4 mills/kwh for the PWR plant (July 1986 US-dollars). When a construction period of PHWR plant is longer by one year than that of PWR plant, there is no difference in the unit power cost of two plants. This comparison leads to no definite conclusion on the cost advantage of the PWR plant versus the PHWR plant. We conclude that the selection issue of nuclear power plants in Korea still remains an open question and that future effort to solve this question should be made toward economic quantification of those factors such as technology transfer and localization.