• YAKHAK HOEJI
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• v.49 no.1
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• pp.68-73
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• 2005

Epi-xanthatin analogs containing hydrophilic substituents such as carboxylic acid, alcohol, morpholine, amino acid, and glucose derivatives were synthesized and their in vitro cytotoxicity and in vivo antitumor activity were evaluated. The target compounds were generally cytotoxic against tumor cell lines of human origin with $ED_{50}$ values of $0.1{\sim}30{\mu}g/ml$, except the highly hydrophilic analog 6 containing aspartic acid. Contrary to the potent cytotoxicity weakly hydrophilic analogs 2 and 8 were not active in vivo, or even toxic to the test animals. As a result, hydrophilic analog of epi-xanthatin did not show in vitro cytotoxicity and hydrophobic analogs did not show in vivo antitumor activity, thus it is presumed that amphiphilic analogs or those with medium hydrophilicity would exhibit the antitumor potency in vivo.

• YAKHAK HOEJI
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• v.37 no.1
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• pp.66-75
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• 1993

Dental abrasive, dicalcium phosphate dehydrate (DCPD) was prepared and the several important factors affecting on the quality of toothpaste were investigated by means of set test, glycerine absorption, Coulter counter test, color difference, BET adsorption, mercury porosimetery, and rheogram comparing with two foreign DCPDs, MFO4 and Dentphos K. Sample DCPD was prepared by reaction between 85% H$_{3}$PO$_{4}$ and 15% milk of lime at $39^{\circ}C$ (pH6.5), and stabilized with TSPP and TMP. The physicochemical properties of Sample DCPD were obtained as follows: whiteness (98.99), average particle size (15.5 $\mu\textrm{m}$), pH (7.9), remainder particle weight (0.49w/w%), glycerine absorption value (64 ml), and set test (passed). N$_{2}$ adsorption curves (BET) of three kinds of DCPD showed non-porous type III isotherm. BET adsorption parameters of sample DCPD showed that surface area was 24.9 m$^{2}$/g, total pore volume 0.09 cm$^{3}$/g and average pore radius 72.0 $\AA$. The rheogram of the toothpaste containing each DCPD showed bulged plastic flow with yield vlaue and thixotropic behavior. These results meet standard requirements as abrasive standard, and suggested that synthesized sample DCPD could be used a dental abrasive such as a high quality grade in practice as foreign DCPDs.

• Physical Therapy Rehabilitation Science
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• v.2 no.1
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• pp.21-26
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• 2013

Objective: The aim of this study was to investigate the effect of therapeutic ultrasound (US) of cell viability and inflammatory cytokine in rat articular chondrocyte cultures stimulated with lipopolysaccharide (LPS). Design: One group pretest-posttest design. Methods: Cultured chondrocytes were treated with US and/or LPS and assessed for viability, Tumor necrosis factor $(TNF)-{\alpha}$ and Interleukin (IL)-1 production. Results: Oxidative stress was induced in rat chondrocytes with LPS. The cell viability was decreased in chondrocytes after treatment with LPS. The viability revealed that low-intensity pulsed ultrasound (LIPUS) exerted no significant cytotoxicity in the rat chondrocyte. LIPUS inhibited decreased cell viability in the presence of LPS ($30{\mu}g/ml$) in a intensity dependent pattern at LIPUS (p<0.05). $TNF-{\alpha}$ production in the presence of LPS was also inhibited in a dose dependent manner (p<0.05 from $30mW/cm^2$). IL-1 production in the presence of LPS was inhibited as well (p<0.05 from $7.5mW/cm^2$). Conclusions: Our results demonstrate that US was the anti-inflammatory effect of chondrocytes. LIPUS may exert its anti inflammatory effects through inhibition of $TNF-{\alpha}$ and IL-1 synthesis. These results suggest that US have potential for use as a pain relief and reduce the articular destruction.

• Korean Journal of Materials Research
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• v.14 no.5
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• pp.358-362
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• 2004

$Si_3$$N_4$ ceramics have been identified as one of the promising structural ceramics. This study has been carried out to investigate of the synthetic behaviors of $Si_3$$N_4$ derived from domestic silica-stone by direct nitriding method. The silicon nitridation reaction has been studied in the temperature range of $1300～1550^{\circ}C$. Below the $1400^{\circ}C$, the nitriding rate was measured to be 16%. For the temperatures higher than the $1400^{\circ}C$, $\beta$-$Si_3$$N_4$ phase was formed mainly, and the nitriding rate showed above 98%. With the increasing of sample weight of silicon powder, the nitriding rate and $\beta$-$Si_3$$N_4$ phase increased at $1400^{\circ}C$ for 2 hours. The shape and particle size of$ Si_3$$N_4$ powder synthesized at $1400^{\circ}C$ for 2 hours showed the irregular angular-type and 10 $\mu\textrm{m}$, respectively.

• Korean Journal of Materials Research
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• v.13 no.8
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• pp.524-530
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• 2003

In order to prepare the uniform copper particles from copper sulfate solution by using hydrazine as a reduction agents, the reduction behavior of copper particles from copper sulfate was investigated in detail at room temperature by the observation of reaction products. The effects of $NH_4$OH and $Na_4$$P_2$$O_{7}$ on the formation of uniform copper particles were discussed. ($NHCu_3$)$_4$$SO_4$was completely formed at over pH 11 by adding $NH_4$OH in copper sulfate solution. The fine $Cu_2$O with the particle size of 50 nm was produced in the initial reduction process of (NH$Cu_3$)$_4$$SO_4$solution with $Na_4$$P_2$$O_{ 7}$ and then the Cu$_2$O was converted into copper particles by inserting additional hydrazine. When Cu(NH$_3$)$_4$SO$_4$solution with $Na_4$$P_2$$O_{ 7}$ was reduced at $80^{\circ}C$ by hydrazine, the highly dispersed copper particles with the particle size of about 0.8 $\mu\textrm{m}$ was obtained.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.11
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• pp.596-602
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• 2000

Diamond thin films were synthesized on WC-Co substrate at various experimental parameters using 13.56MHz RF PACVD)radio frequency plasma-assisted chemical vapor deposition). In order to increased the nucleation density, the WC-Co substrate was polished with 3${\mu}m$ diamond paste. And the WC-Co substrate was preatreated in $HNO_3\;:\;H_2O$ = 1:1 and $O_2$ plasma. In $H_2-CH_4$ gas mixture, the crystallinity of thin film increased with decreasing $CH_4$ concentration at 800W discharge power and 20torr reaction pressure. In $H_2-CH_4-O_2$ gas mixture, the crystallinity of thin film increased with increasing $O_2$ concentration at 800W discharge power, 200torr reaction pressure and 4% $CH_4$ concentration.

• Journal of the Korean Ceramic Society
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• v.32 no.5
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• pp.543-548
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• 1995

Li-ferrite powders were prepared from mixture of Fe and Li salts using a hydrothermal method. Their crystal structure, microstructure and magnetic property were investigated with X-ray diffraction analysis, chemical analysis, SEM, and VSM. In the case of using FeCl3 as a precursor, Li-ferrite powders were synthesized. However, Fe3O4 was formed when the precursor was a divalented Fe2SO4 or FeCl2. The precipitation rate of Li-ferrite was increased as the reaction temperature increased. The optimum conditions of synthesis were the mole ratio of Fe+++/Li+=2, pH 13, the reaction temperature of 25$0^{\circ}C$ and the reaction time of 120min. With this condition, the spherical particles with good dispersion were obtained with average particle size of 0.4${\mu}{\textrm}{m}$ and saturation magnetization of 65 emu/g.

• Journal of Surface Science and Engineering
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• v.50 no.2
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• pp.114-118
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• 2017

Bismuth telluride ($Bi_2Te_3$) and its alloys are well-known thermoelectric materials for ambient temperature applications. In this study, the dissolved Bi-Te precursor solution was used to synthesis metallic $Bi_2Te_3$ powder via ultrasonic spray pyrolysis and reduction process. The droplets of the Bi-Te precursor solution were decomposed to Bi-Te oxide powders by ultrasonic spray pyrolysis. The spherical $Bi_2Te_3$ powders were synthesized by reduction reaction in atmosphere of hydrogen gas at the temperature above $375^{\circ}C$ for 6h. The reduced $Bi_2Te_3$ powders have a mean particle size of $1.5{\mu}m$. The crystal structure of the powder was evaluated by X-Ray diffraction(XRD), and the microstructure with size and shape powders was observed by fieldemission scanning electron microscope(FE-SEM) and transmission electron microscope(TEM).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.12C
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• pp.181-189
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• 2001

In this thesis, a policing algorithm is proposed, which is one of the traffic management function in ATM networks. The proposed algorithm minimizes CLR(Cell Loss patio) of high priority cells and solves burstiness problem of the traffic caused by multiplexing and demultiplexing process. The proposed algorithm has been implemented with VHDL and is divided into three parts, which are an input module, an UPC module, and an output module. In implementation of the UPC module\`s memory access, memory address is assigned according to VCI\`s LSB(Lowest Significant Byte) of ATM header for convenience. And the error of VSA operation from counter\`s wrap-around can be recovered by the proposed method. ANAM library 0.25 $\mu\textrm{m}$ and design compiler of Synopsys are used for synthesis of the algorithm and Synopsys VSS tool is used for VHDL simulation of it

• Journal of the Korean Society of Combustion
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• v.21 no.2
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• pp.7-14
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• 2016

Evaporation and combustion characteristics of fuel droplet with carbon nanoparticle were investigated in a rapid compression machine(RCM). RCM is an experimental equipment to simulate one compression stroke of reciprocating engine. Nitrogen was charged into reaction chamber for evaporation experiment, while oxygen was charged for combustion experiment. N990 carbon black and n-heptane were used to synthesize the carbon nanofluids. Surfactant, span80, was used to make synthesis easier. The droplet pictures were taken using a high speed camera with 500 frames per second. Thermocouple, of which tip is $50{\mu}m$, was used not only to measure transient bulk temperature, but also to suspend the droplet. Reaction chamber temperature was calculated from pressure data. The evaporation rate of nanofluids was improved compared to pure fuel. The ignition delay was promoted due to the nanoparticle, but the burning rate was decreased.