• 대한화학회지
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• 제38권8호
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• pp.576-584
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• 1994

수중의 금속 산화물을 신속하고 간단하게 용해시킬 수 있는 연속흐름 마이크로파 용해장치를 개발하였다. 이로서 금속 산화물 입자를 용해시킴과 동시에 유도결합 플라즈마 분광기(ICP-AES)를 이용하여 ON-LINE으로 분석하는 완전 자동화 분석 장치의 개발이 가능토록 하였다. 연속흐름 마이크로파 용해장치는 개방형 튜브 장치와 억제형 튜브 장치로 구분하여 제작하고 최적화 시험을 수행하였다. 개방형 튜브 용해장치의 최적조건은 튜브길이가 30m, 마이크로파 출력 20%, 염산 농도 0.6N, 유속은 3.5ml/min였으며, 억제형 튜브 용해장치는 튜브 길이가 7.2m, 마이크로파 출력 30%, 염산 농도 0.6N, 유속은 3.1ml/min였다. 억제형 튜브 용해장치가 개방형 장치에 비하여 용해시간이 3배 정도 단축되었고 용해시킬 수 있는 시료의 농도 범위도 10배 정도 높았다. 제작된 용해장치의 정밀도는 베치식 용기 용해법과 거의 유사한 결과를 나타내어 Fe, Cu는 5% 정도의 상대 표준 편차값을 나타내었고, Zn,Co는 10%내외로 다소 높게 나타났다.

• 한국자동차공학회논문집
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• 제12권6호
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• pp.38-45
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• 2004

This paper studies the effects of intake port configuration on the swirl that is key parameter in the flow field of direct injection diesel engines. In-cylinder flow characteristics is known to have significant effects on fuel air mixing, combustion and emissions. To investigate the swirl flow generated by various intake ports, steady state flow tests were conducted to evaluate the swirl. Helical port geometry, SCV shape and bypass were selected as the design parameters to increase the swirl flow and parametric study was performed to choose the optimal port shape that would generate a high swirl ratio efficiently. The results revealed that a key factor in generating a high swirl ratio was to suitably control the direction of the intake air flow passing through the valve seat. For these purposes, we changed the distance of helical and tangential port as well as installed bypass near the valve seat and the effects of intake port geometry on in-cylinder flow field were visualized by a laser sheet visualization method. From the experimental results, we found that the swirl ratio and mass flow rate had a trade off relation. In addition, the result indicates that the bypass is a effective method to increase the swirl ratio without sacrificing mass flow rate.

• Clinical and Experimental Reproductive Medicine
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• 제24권3호
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• pp.319-324
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• 1997

Despite the direct placement of sperm within the oocyte, fertilization failure still occurs after ICSI. This study was accomplished to analyze the chromosomes in oocytes failed to fertilize after ICSI comparing to oocytes failed to fertilize by conventional in vitro insemination. Seventy-four ICSI cycles and 122 conventional IVF cycles were included in analysis. Included unfertilized oocytes were from 74 patients (mean age = $32.7{\pm}3.7$). Ninety-three oocytes were informative and 83 oocytes were legible for cytogenetic analysis. Sixty-two oocytes out of 83 (74.7%) had normal chroruosomes, while 15 (18.1%) were hypoploidy, 6 (7.2%) were hyperploidy. Eighteen oocytes out of 93 (17.6%) were premature chromosome condensation (PCC). Two hundred ninety-four unfertilized oocytes after conventional insemination were subjected to chromosomal analysis and 180 oocytes were legible for analysis. One hundred thirty-two oocytes out of 180 (73.3%) were normal, while 22 (12.2%) were hypoploidy, 20 (11.1%) were hyperploidy, and 6 (3.3%) were polyploidy. Twenty-two oocytes (12.2%) were PCC. There was no difference in chromosomes between oocytes that failed to fertilize after ICSI or conventional insemination. High PCC rates in fertilization-failed oocytes suggest that oocytes maturity is another important factor in achieving successful fertilization.

• Archives of Pharmacal Research
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• 제16권4호
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• pp.336-338
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• 1993

The immunomodulating activity of Kp, an antitumor protein-polysacchanide preparation from the shake-cultured mycelia of Phellinus linteus, was investigated in ICR mice subcutaneously implanted wit $1\times10^6$ cells of sarcoma 180. The mice were intraperitoneally administered with Kp at a does of 100 mg/kg once daily for five consecutive days starting from 24 hrs after the tumor implantation. Ten days after the last injection, the mice were immunized with $1\times10^7$ or $4\times10^8$ sheep red blood cells (SRBC) and five days later, the antibody-forming immune response were assessed by direct hemolytic plaque assay. To an immunization does of $1\times10^7$ SRBC, the Kp-treated mice elicied a successful humoral immune response despite the turmor-burden and produced $259\times10^3$ plaque-forming cells (PFC)/spleen, while the corresponding tumor-bearing control mice showed virtually no reponse $(2.0\times10^3$ PFC/spleen) (the stimulation index=129.5). However, to an immunization dose of $4\times10^8$ SRBC, both of the control mice and Kp-treated mice showed almost the same level of strong humoral immune response. From these data it is clear that Kp effectively restores the humoral immune response of the turmor-bearing ICR mice.

• Journal of Periodontal and Implant Science
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• 제31권2호
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• pp.389-400
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• 2001

Previous studies have demonstrated an increase in bone mass and density with the use of bisphosphonate in osteoporosis. This agent acts as an inhibitor of osteoclastic activity, and results in increase of net osteoblastic activity. Currently, it has been reported that bisphosphonate has direct effect on osteoblast. This study was designed to evaluate the effect of alendronate on bone regeneration in defect of rat calvaria. The animals used for these experiments were 48 male rats, over 6-8 weeks old. They were divided into three groups according to the dose of alendronate($MK-217^{(R)}$, Merck, USA) administered. After the calvarial defects were surgically created, the rats received a peritoneal alendronate(0.25mg/kg) in group I, a peritoneal alendronate(1.25mg/kg) in group II, and a peritoneal normal saline injection in the control group. Three and six weeks later, blood was sampled and evaluated for alkaline phosphatase activity. The animals were sacrificed for histological observation and histometric analysis of the level of bone formation. The alkaline phosphatase activity was similar in three groups at 3 weeks of experiment. The activity at 6 weeks increased more than twice, compared to 3 weeks, and was slightly higher in group I than the other two groups. In histological observation, all the groups at 3 weeks, osteoblast rimming and new bone formation were observed along the defect margin. At 6 weeks, the defect was almost closed with new and more mature bone, but new bone is thinner than original bone in the central portion of defect. In histometric analysis, group I and II at 3 weeks showed significantly greater new bone formation than the control, and all the groups at 6 weeks showed similar amount of bone formation. These result suggest that alendronate administration in the dose of 0.25mg/kg and 1.25mg/kg promote osseous regeneration.

• Journal of Electrical Engineering and Technology
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• 제13권4호
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• pp.1682-1691
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• 2018

Natural ester is a suitable substitute for mineral oil and has been widely used in AC transformer in many countries. In order to further application of natural ester in direct current (DC) equipment, it is needed to investigate its long term insulation property under DC condition. In this paper, a thermal ageing experiment was conducted for both mineral oil-paper and natural ester-paper insulation. The DC breakdown and space charge characteristics of insulation paper impregnated with natural ester and mineral oil was compared. Results show that the resistivity of the paper immersed in natural ester and mineral oil both increase as the ageing goes on. While insulation paper impregnated with natural ester has higher resistivity and DC breakdown voltage than the paper impregnated with mineral oil. The DC breakdown voltage for the oil impregnated insulation paper being DC pre-stressing is higher than that without pre-stressing. The average DC breakdown field strength difference between the test with pre-stressing and without pre-stressing clearly shows that there is an apparent enhancement effect for the homo-charge injection on the DC breakdown.

• 한국자동차공학회논문집
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• 제12권1호
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• pp.17-24
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• 2004

As the environmental pollution becomes serious global problem, the regulation of emission exhausted from automobiles is strengthened. Therefore, it is very important to know how to reduce the NOx and PM simultaneously in diesel engines, which has lot of merits such as high thermal efficiency, low fuel consumption and durability. By this reason, the new concept called as Homogeneous Charge Compression Ignition(HCCI) engines are spotlighted because this concept reduced NOx and P.M. simultaneously. However, it is well known that HCCI engines increased HC and CO. Thus, the investigation of combustion characteristics which consists cool and hot flames for HCCI engines were needed to obtain the optimal combustion condition. In this study, combustion characteristics for direct injection type HCCI engine such as quantity of cool flame and hot flame, ignition timing and ignition delay were investigated to clarify the effects of these parameters on performance. The results revealed that diesel combustion showed the two-stage ignition of cool flame and hot flame, the rate of cool flame increase and hot flame decrease with increasing intake air temperature. On the other hand, the gasoline combustion is the single-stage ignition and ignition timing is near the TDC. In addition mixed fuel combustion showed different phenomenon, which depends on the ratio of gasoline component. Ignition timing of mixed fuel is retarded near the TDC and the ignition delay is increased according to ratio of gasoline.

• The Korean Journal of Physiology and Pharmacology
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• 제16권6호
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• pp.437-446
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• 2012

Ulcerative colitis is an inflammatory bowel disease (IBD) characterized by recurrent episodes of colonic inflammation and tissue degeneration in human or animal models. The contractile force generated by the smooth muscle is significantly attenuated, resulting in altered motility leading to diarrhea or constipation in IBD. The aim of this study is to clarify the altered contractility of circular and longitudinal smooth muscle layers in proximal colon of trinitrobenzen sulfonic acid (TNBS)-induced colitis mouse. Colitis was induced by direct injection of TNBS (120 mg/kg, 50% ethanol) in proximal colon of ICR mouse using a 30 G needle anesthetized with ketamin (50 mg/kg), whereas animals in the control group were injected of 50% ethanol alone. In TNBS-induced colitis, the wall of the proximal colon is diffusely thickened with loss of haustration, and showed mucosal and mucular edema with inflammatory infiltration. The colonic inflammation is significantly induced the reduction of colonic contractile activity including spontaneous contractile activity, depolarization-induced contractility, and muscarinic acetylcholine receptor-mediated contractile response in circular muscle layer compared to the longitudinal muscle layer. The inward rectification of currents, especially, important to $Ca^{2+}$ and $Na^+$ influx-induced depolarization and contraction, was markedly reduced in the TNBS-induced colitis compared to the control. The muscarinic acetylcholine-mediated contractile responses were significantly attenuated in the circular and longitudinal smooth muscle strips induced by the reduction of membrane expression of canonical transient receptor potential (TRPC) channel isoforms from the proximal colon of the TNBS-induced colitis mouse than the control.

• Journal of Microbiology
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• 제43권4호
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• pp.375-380
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• 2005

Autonomous ultradian metabolic oscillation (T$\simeq$50 min) was detected in an aerobic chemostat culture of Saccharomyces cerevisiae. A pulse injection of GSH (a reduced form of glutathione) into the culture induced a perturbation in metabolic oscillation, with respiratory inhibition caused by $H_2S$ burst pro-duction. As the production of $H_2S$ in the culture was controlled by different amino acids, we attempted to characterize the effects of GSH on amino acid metabolism, particularly with regard to branched chain and sulfur-containing amino acids. During stable metabolic oscillation, concentrations of intra-cellular glutamate, aspartate, threonine, valine, leucine, isoleucine, and cysteine were observed to oscil-late with the same periods of dissolved $O_2$ oscillation, although the oscillation amplitudes and maximal phases were shown to differ. The methionine concentration was stably maintained at 0.05 mM. When GSH (100 $\mu$M) was injected into the culture, cellular levels of branched chain amino acids increased dramatically with continuous $H_2S$production, whereas the cysteine and methionine concentrations were noticeably reduced. These results indicate that GSH-dependent perturbation occurs as the result of the promotion of branched chain amino acid synthesis and an attenuation of cysteine and methionine synthesis, both of which activate the generation of $H_2S$. In a low sulfate medium containing 2.5 mM sulfate, the GSH injections did not result in perturbations of dissolved $O_2$ NAD(P)H redox oscillations without burst $H_2S$ production. This suggests that GSH-dependent perturbation is intimately linked with the metabolism of branched-chain amino acids and $H_2S$ generation, rather than with direct GSH-GSSG redox control.

• Biomolecules & Therapeutics
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• 제3권4호
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• pp.316-321
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• 1995

All the pharmacological studies of LB17522 described here were carried out with high doses (fifteen to sixty times of the therapeutic dose) to determine an indication of potential side effects in clinical use in terms of the acute clinical signs, cardiovascular and central nervous system. LB10522 does not produce any observable clinical signs except for the symptoms such as moist eye, skin rash, slight salivation, vomitting, and slightly reduced activity. The effects of LB10522 on the hemodynamics and cardiac function of anesthetized beagle dogs are as follows; heart rates and mean arterial blood pressure had a tendency to increase mildly, which is a normal finding in anesthetized dogs. All the animals except for one showed relatively stable respiratory rates throughout the observation period. Each animal treated with LB10522 showed slight increase in the left cardiac work and left ventricular stroke work which are mainly related to corresponding increases in cardiac output. Femoral blood flow were shown to be increased in some animals treated with LB10522. The epileptogenic activities of various cephalosporins were assessed by a direct intracerebral injection of appropriate concentration of test articles. The CD$_{50}$ values (nmol) obtained from the analysis of the dose-response data are as follows; 78.2, 175.3, 156.3, and 53.5 for cefazolin, cephaloridine, ceftazidime, and LB 10522, respectively. LB10522 seems to be equipotent with cefazolin or to be three times more potent than cephaloridine and ceftazidime in causing adverse CNS stimulation. Taken into consideration all the information obtained, LB10522 is not supposed to induce much changes in the functions examined in these studies in man at therapeutic doses.s.