• Preventive Nutrition and Food Science
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• v.16 no.2
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• pp.174-178
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• 2011

The cell permeability and cytotoxic effects of different-sized zinc oxide (ZnO) particles were investigated using a human colorectal adenocarcinoma cell line called Caco-2. Morphological observation by scanning electron microscopy revealed that three zinc oxides with different mean particle sizes (ZnO-1, 20 nm; ZnO-2, 90~200 nm; ZnO-3, $1\sim5\;{\mu}m$) tended to aggregate, particularly in the case of ZnO-1. When cytotoxicities of all three sizes of zinc oxide particles were measured at concentration ranges of $1\sim1000\;{\mu}g$/mL, significant decreases in cell viability were observed at concentrations of $50\;{\mu}g$/mL and higher. Among the three zinc oxides, ZnO-1 showed the lowest viability at $50\;{\mu}g$/mL in Caco-2 cells, followed by ZnO-2 and ZnO-3. The permeate concentration of ZnO-1 from the apical to the basolateral side in the Caco-2 model system after four hours was about three-fold higher than that of either ZnO-2 or ZnO-3. These results demonstrated that ZnO-1, with a 20 nm mean particle size, had poorer viability and better permeability in Caco-2 cells than ZnO-2 and ZnO-3.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.399-402
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• 2006

현재까지 연료전지 전해질 막으로는 Nafion으로 잘 알려져 있는 perfluorosulfonic acid(PFSA)막이 주를 이루고 있다. 이 막들은 $80^{\circ}C$ 이하의 낮은 온도의 연료전지에서 가장 좋은 성능을 보인다. PFSA 막들은 탄소-불소로 이루어진 사슬의 특성상 산화, 환원의 조건에서도 뛰어난 안정성을 보이며 이온 전도도가 0.1S/cm 이상으로 기존에 알려진 전해질 막들 중 가장 우수한 성능을 나타낸다. 하지만 연료전지의 작동온도가 $100^{\circ}C$ 이상의 높은 온도에서 는 막에 존재하던 수분이 제거되면서 수소이온 전도도가 떨어지며 기계적 물성도 떨어지는 문제점을나타낸다. $100^{\circ}C$ 이상의 온도에서 연료전지를 작동시키면 양쪽의 전극에서 일어나는 촉매반응의 속도가 향상되며, 물의 끓는점 이상에서 작동되므로, 전지 내에서 다양한 상을 고려하지 않고 기화된 물만을 고려하여 설계를 할 수가 있다. 따라서 최근 이러한 고온/저가습 운전을 위 한 전해질 막의 개발을 위해 기존의 Nafion 막에 전도성 무기 입자를 도입하는 연구들이 활발히 진행되고 있다. 본 연구에서는 전도성 무기 입자로서 $ZrO_2$나노입자를 합성하고, 이를 상용 10 wt.% Nafion 용액에 분산하여 solution casting 방법을 통해 $61{\mu}m$ 두께의 유기-무기 복합막을 제조하였다. 제조한 유기-무기 복합막의 성능 평가를 위하여 함수율, 이온 전도도, 당량무게 및 단위 전지를 이용한 전류-전압 곡선을 측정하여 상용 Nafion 112 막과 비교해 보았다. $ZrO_2$ 입자는 전도성이며 동시에 친수성을 나타내기 때문에 상용 막에 비하여 함수율 및 수소이온 전도도가 우수하게 나타났다. 복합막의 이러한 물성은 $100^{\circ}C$이상의 고온에서 전해질 막 내의 물 관리를 용이하게 한다. 단위 전지 운전 온도 $130^{\circ}C$, 상대습도 37%의 운전 조건에서도 상당히 우수한 전지 성능을 보임에 따라 고온/저가습 조건에서 상용 Nafion 112 막보다 우수한 막 특성을 나타냄을 확인하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.6
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• pp.45-50
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• 2005

To determine precise position GPS carrier phase measurements are used. In addition, the multi-antenna system consisting of 2 or more GPS antennas can make attitude determination effectively. When GPS carrier phase measurements are used the integer ambiguity must be fixed. The success rate is used to validate the integer ambiguity. For LEO satellite attitude determination the double difference carrier phase measurements are used, the success rate is calculated using the covariance matrix and the measurement matrix. The constraint that LEO satellite position vector and attitude vector is orthogonal is suggested for improving the success rate. The LEO satellite orbit model is KITSAT3. The results of the simulation are shown and analyzed.

• Journal of radiological science and technology
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• v.10 no.1
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• pp.13-23
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• 1987

Author has studied for finding the method of decreasing the radiation dose and increasing diagnostic range in chest X-ray radiography. The study for the added filter thickness from half value layer to 1/8 value layer by decreasing curve and research for the exposure factors, decreasing ratio of radiation dose, ratio of scatter ray and image quality in chest X-ray radiography. The results were as follows: 1. By using the rare earth intensifying screen system at 120 Kvp, the sensitivity is increased by times and the exposure ratio is decreased 0.22 by comparison with the $CaWO_{4}$ intensifying screen system at 80 Kvp. 2. By using Al added filter of 1/8 value layer, the scatter ray is increased more than no filter, But the scatter ray is decreased more in $G_{4}/RxOG$ intensifying system than in LT-II/Rx intensifying system. 3. At 120 Kvp, the image quality value of $G_{4}/RxOG$ system is increased more than LT-II/Rx system compared with slight decreasing image quality value at 80 Kvp. Concluded that by using the added filter could decrease the radiation dose by 1/3 and obtain effective image quality with the added filter at high voltage hard exposure.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.4
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• pp.378-383
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• 2001

Larvae of Metapenaeopsis dalei (Rathbun) were successfully spawned and reared in the laboratory under controlled conditions. The experiments were designed to examine effects of salinity (20, 25, 30 and 35), temperature (21, 24 and $27^{\circ}C$ ) and food (five items) on larval development, survival and growth, Salinity affected larval survival, from $\%$ at 20, to $60\%$ at 35 (protozoea 1 to first postlarva), The highest survival rate was obtained at $35\%_{\circ}$. Temperature affected larval survival, from $46\%$ at $27^{\circ}C$ to $54\%$ at $21^{\circ}C$(protozoea 1 to first postlarva). The highest survival rate was obtained at $24^{\circ}C$. Mortality was the highest from protozoea 1 to protozoea 3, but decreased considerably for all temperatures once the mysis stage was reached. Larval growth was affected by different of food items. Phytoplankton (Isochrysis galbana) was the optimum food for the larval survival and the growth from protozoea 3 to first postlarva.

• Journal of Preventive Medicine and Public Health
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• v.41 no.4
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• pp.225-231
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• 2008

Objectives: Bioterrorism (BT) preparedness and response plans are particularly important among healthcare workers who will be among the first involved in the outbreak situations. This study was conducted to evaluate the current status of education for BT preparedness and response in health care-related colleges/junior colleges and to develop learning objectives for use in their regular curricula. Methods: We surveyed all medical colleges/schools, colleges/junior colleges that train nurses, emergency medical technicians or clinical pathologists, and 10% (randomly selected) of them that train general hygienists in Korea. The survey was conducted via mail from March to July of 2007. We surveyed 35 experts to determine if there was a consensus of learning objectives among healthcare workers. Results: Only 31.3% of medical colleges/schools and 13.3% of nursing colleges/junior colleges had education programs that included BT preparedness and responses in their curricula. The most common reason given for the lack of BT educational programs was 'There is not much need for education regarding BT preparedness and response in Korea'. None of the colleges/junior colleges that train clinical pathologists, or general hygienists had an education program for BT response. After evaluating the expert opinions, we developed individual learning objectives designed specifically for educational institutions. Conclusions: There were only a few colleges/junior colleges that enforce the requirement to provide education for BT preparedness and response in curricula. It is necessary to raise the perception of BT preparedness and response to induce the schools to provide such programs.

• Journal of Veterinary Clinics
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• v.35 no.4
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• pp.155-160
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• 2018

A 6-year-old intact female Shih-tzu dog was referred due to anorexia. Physical examination, complete blood count, serum chemical analysis, radiography, and ultrasonography were evaluated. Physical examination and hematological analysis showed normal findings. Abdominal radiographs and ultrasound revealed well-defined masses in the spleen. Other abdominal organs showed no significant abnormalities. Tissue samples taken via sono-guided fine needle aspiration of the splenic mass showed many bare nuclei, which were variable in size. Results of histopathological and immunohistochemical (IHC) analyses performed after splenectomy were consistent with paraganglioma. Based on these findings, we diagnosed this patient with a paraganglioma of splenic origin. Two months after splenectomy, abdominal ultrasonography revealed a new neoplastic lesion in the liver. The clients refused further management and the patient expired three months after initial diagnosis. Necropsy as well as histopathological and IHC examinations of other systemic organs including the liver, adrenal gland, kidney, brain, urinary bladder, lung, aortic body, carotid body, and pancreas were performed. The neoplastic tissue in the liver also demonstrated features of a paraganglioma, and there were no remarkable findings in all other organs.

• Journal of environmental and Sanitary engineering
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• v.20 no.4 s.58
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• pp.31-37
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• 2005

The objective of this study is to analyze and suggest the policy on devolution of environmental administrative function between central and local government in Korea. This study also research to make the prospect of power from central government to local government's officers by analyzing the characteristics and contents, standards of local devolution and the attitudes of central and local governments on its process from September 2001 to April 2003. The date collected from the more than 675 questionnairs of government officers included as the Ministry of Environment and local government. The date also collected from interview and field survey. The questionnaire had collected in two times between 2001 and 2003. The environmental administrative function has reallocated from central government to local government since 2001. The devolution focused on simple implemental services and institutional delegated services might result in the lack of initiative and locality of local governments. Therefore, devolution should be proceed towards reinforcing the decision-making capacity and financial and manpower of local government. This paper also showed the weakness on speciality and experience on local bureaucratic in Korean society. This study announced that local government's officer has appeared the negative impact on environmental regulation and the conflict between central and local government.

• Journal of Veterinary Clinics
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• v.34 no.3
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• pp.193-196
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• 2017

A 14-year-old, castrated male, domestic shorthair cat was referred for gastrointestinal (GI) signs, including nausea, regurgitation, anorexia, and weight loss. Abdominal ultrasonography revealed thickening of the wall of the gastric and proximal duodenum, moderately enlarged mesenteric lymph nodes, and coarse echotexture of the splenic parenchyma. The results of the feline leukemia virus test were positive. Based on gastrointestinal endoscopic characteristics and histopathological examinations, low-grade alimentary lymphoma was identified in multiple regions of the gastrointestinal tract. The patient was treated with oral prednisolone and chlorambucil chemotherapy, and the clinical signs resolved gradually. During serial follow-up, ultrasonographic findings demonstrated decreases in the duodenal wall thickness and size of the abdominal lymph nodes over a period of 550 days. Survival time was 886 days with prednisolone and chlorambucil chemotherapy. This report describes clinical features, imaging findings, endoscopic characteristics, histopathological features, and long-term management with chlorambucil chemotherapy in a case of feline low-grade alimentary lymphoma.

• Journal of Microbiology and Biotechnology
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• v.11 no.3
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• pp.399-405
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• 2001

Urushiol, a natural pro-electrophilic quinone compound, has potential structural characteristics as antitumor chemotherapeutic agents. However, urushiol's use as an antitumor drug has some problems, because it is hardly miscible with an aqueous solution. Purified urushiol is highly viscous and soluble only in strong solvents. for this study, we prepared an urushiol-ethanol micro-emulsion with a unimodal size distribution by high-speed homogenization. This generated effective delivery of urushiol to its action wites, so that we could investigate its cytotoxic activity against cancer cells. Using a colony-forming assay, we were able to show that urushiol selectively inhibited the growth of the ovarian cancer cells PA-1 and 2774 at a concentration of $10^{-6}$, whereas it had only a negligible effect on normal CHO cells at the same concentration. The data suggest that urushiol may have potential as an effective antitumor agent in the treatment of ovarian cancer. In addition, we addressed the question of whether the specific cytotoxic effect of urushiol is linked to apoptosis, by DNA fragmentation and DAPI staining assays. The inhibitory effects of urushiol on the growth of ovarian cancer cells was found to be associated with DNA fragmentation and the fragmented nuclei formation, both of which represent markers for the induction of apoptosis. Therefore, the results suggested that urushiol affected its profound cytotoxicity by triggering apoptosis in ovarian cancer cells.