• Korean Chemical Engineering Research
• /
• 제50권2호
• /
• pp.317-327
• /
• 2012

케이크 여과와 고액분리에서 가장 중요한 지표인 케이크 평균 비저항을 결정하는 방법으로 여과실험을 사용하고 있으나 침전 등의 영향으로 정확한 값을 측정하기 어렵다. 이 연구에서는 조금 더 안정된 방법으로 여과 후 형성된 케이크에 입자제거수를 투과시켜 평균 비저항을 측정하는 여과-투과 실험을 제안한다. 탄산칼슘 1 wt% 현탁액을 사용하여 여과-투과 실험을 8종의 여과매체에 대하여 여과매체 1장과 3장, 압력 0.5 기압과 0.2 기압의 조건에서 각 조건 당 3~5회씩 동일한 실험을 수행하였다. 그 결과 여과 후 투과에서도 안정된 투과 속도가 측정됨을 확인하였고, 이를 바탕으로 Ruth의 공식을 분석하여 투과기간의 특징을 구명(究明) 하고 여과기간에 발생하는 침전의 영향을 분석하였다. 그 다음, 여과매체 3종을 선택하여 여과와 투과에서의 케이크 평균 비저항값으로 일원배치법에 의한 분석을 하였다. 분석결과 여과에 의해서는 0.5 기압과 0.2 기압의 케이크 평균 비저항값이 구분되지 않으나, 투과에 의해서는 충분히 구분되었다. 또한 투과기간의 케이크 평균 비저항값들이 여과기간의 그것에 비해 매우 좁은 분포를 가지는 것을 확인했다. 여러 여과매체의 여과 실험결과를 분석하여, 여과매체 저항을 현재의 방법으로 측정하는 것은 큰 의미가 없음을 밝혔고, 유리섬유 여과-투과 실험 결과로 낮은 압력에서 입자의 여과매체 이동 가능성에 대한 분석을 수행했다.

• 한국식품위생안전성학회지
• /
• 제25권1호
• /
• pp.36-42
• /
• 2010

식품유사용매 중 EDA 및 HMDA 분석법을 확립하고, 국내유통 재질 조리기구 124건에 대하여 식품유사용매별 이행량을 조사하였다. EDA 및 HMDA를 ethyl chloroformate로 디우레탄 유도체화한 후 GC/FID로 정량 또는 GC/MS로 확인하였다. 확립된 분석방법은 EDA 및 HMDA 각각에 대하여 LOD $0.3\;{\mu}g/mL$ 및 $0.1\;{\mu}g/mL$이었으며, 상판계수($r^2$) 0.999이상의 직선성 및 식품유사용매별로 88% 이상의 회수율을 확인할 수 있었다. 확립된 정량분석방법을 적용하여 식품유사용매별 이행량을 조사한 결과, EDA는 식품유사용매로 물을 사용한 경우 2품목에서만 각각 $1.31\;{\mu}g/mL$ 및 $2.06\;{\mu}g/mL$ 수준으로 검출되었으며, 나머지는 모두 불검출이었다. HMDA는 식품유사용매로 20% 에탄올을 사용한 경우 3 품목에서 $0.27{\sim}0.93\;{\mu}g/mL$, n-헵탄을 사용한 경우 10 품목에서 $0.26{\sim}0.44\;{\mu}g/mL$으로 검출되었으며, 나머지는 모두 불검출이었다. 본 연구에서 확인된 이행량은 유럽연합의 EDA 및 HMDA 각각의 이행기준인 $12\;{\mu}g/mL$ 및 $2.4\;{\mu}g/mL$과 비교 시 매우 낮은 수준이었다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 추계학술대회 논문집 전기물성,응용부문
• /
• pp.112-114
• /
• 2001

In this letter, we report on the investigation of Si/Ti, Pt/Si/Ti, Co/Si/Ti Ohmic contacts to p-type 4H-SiC. The contacts were formed by a 2-step vacuum annealing at $550^{\circ}C$ for 5 min, $850^{\circ}C$ for 2 min respectively. The contact resistances were measured using the transmission line model method, which resulted in specific $10^{-4}{\Omega}cm^2$, and the physical properties of the contactcontact resistivities in the $9.2{\times}10^{-4}$, $7.1{\times}10^{-4}$ and $4.5{\times}s$ were examined using microscopy, AES(auger electron spectroscopy). AES analysis has shown that, at this anneal temperature, there was a intermixing of the Ti and Si, migration of into SiC. Overlayer of Pt, Co had the effect of decreasing the specific contact resistivity and improving the surface morphology of the annealed contact.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
• /
• pp.51.2-51.2
• /
• 2015

Understanding interfacial phenomena has been one of the main research issues not only in semiconductors but only in life sciences. I have been trying to meet the atomic scale surface and interface analysis challenges from semiconductor industries and furthermore to extend the application scope to biomedical areas. Optical imaing has been most widely and successfully used for biomedical imaging but complementary ion beam imaging techniques based on mass spectrometry and ion scattering can provide more detailed molecular specific and nanoscale information In this presentation, I will review the 27 years history of medium energy ion scattering (MEIS) development at KRISS and DGIST for nanoanalysis. A electrostatic MEIS system constructed at KRISS after the FOM, Netherland design had been successfully applied for the gate oxide analysis and quantitative surface analysis. Recenlty, we developed time-of-flight (TOF) MEIS system, for the first time in the world. With TOF-MEIS, we reported quantitative compositional profiling with single atomic layer resolution for 0.5~3 nm CdSe/ZnS conjugated QDs and ultra shallow junctions and FINFET's of As implanted Si. With this new TOF-MEIS nano analysis technique, details of nano-structured materials could be measured quantitatively. Progresses in TOF-MEIS analysis in various nano & bio technology will be discussed. For last 10 years, I have been trying to develop multimodal nanobio imaging techniques for cardiovascular and brain tissues. Firstly, in atherosclerotic plaque imaging, using, coherent anti-stokes raman scattering (CARS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) multimodal analysis showed that increased cholesterol palmitate may contribute to the formation of a necrotic core by increasing cell death. Secondly, surface plasmon resonance imaging ellipsometry (SPRIE) was developed for cell biointerface imaging of cell adhesion, migration, and infiltration dynamics for HUVEC, CASMC, and T cells. Thirdly, we developed an ambient mass spectrometric imaging system for live cells and tissues. Preliminary results on mouse brain hippocampus and hypotahlamus will be presented. In conclusions, multimodal optical and mass spectrometric imaging privides overall structural and morphological information with complementary molecular specific information, which can be a useful methodology for biomedical studies. Future challenges in optical and mass spectrometric imaging for new biomedical applications will be discussed.

• 대한한방내과학회지
• /
• 제27권1호
• /
• pp.208-220
• /
• 2006

Objective: Eosinophils are typically characterized by a bilobar nucleus with highly condensed chromatin and cytoplasm containing two major types of granules, specific and primary granules, and lipid bodies. The role of inflammation in asthma and other allergic diseases of the airways is widely appreciated, and airway inflammation is now included as a defining feature of asthma. The importance of the presence of eosinophils in the airways of patients with fetal asthma has long been recognized, but the mechanism by which these cells are recruited and retained in the lungs are only now being elucidated. Eotaxin is a potent and specific eosinophil chemoattractant that is mobilized in the respiratory epithelium after allergic stimulation. Methods : Water extracts of Armeniacae Amarum Semen(AAS) and pulmonary epithelial cell lines A549(alveolar typeII epithelial cells) and human eosinophils were used. Cytotoxic effects of AAS and MIS assay were estimated, as well as the effects of AAS on chemokines from prestimulated A549 cells by sandwich ELISA and RI-PCR. Chemotaxis assay was conducted on prestimulated eosinophils treated with AAS. Results : In this study it is demonstrated that $TGF-{\alpha}$, IL-4 and $IL-1{\beta}$ induced the accumulation of chemokine mRNAs in the alveolar epithelial cell lines A549 in dose-dependent manner. Eotaxin and IL-8 were inhibited by AAS in dose-dependent manner(p<0.05). Eosinophil migration was inhibited at high concentrations of AAS(p<0.05). Conculusions : These findings are indicative of suppression of eotaxin and IL-8, and suggest that this is accomplished through AAS treatment. This raises the possibility that AAS is of therapeutic value in diseases such as asthma.

• 대한한방내과학회지
• /
• 제22권4호
• /
• pp.639-645
• /
• 2001

Angiogenesis is a fundamental process in reproduction and wound healing. Under these condition, neovascularization is tightly regulated. Unregulated angiogenesis may lead to several angiogenic diseases, and is thought to be indispensible for solid tumor growth and metastsis. The construction of new vascular network is a multistep cascade involving basement membrane degradation, endothelial cell proliferation, endothelial cell migration, and tube formation. Newly reported anti-angiogenic agents in oriental medical field have targeted both specific and multistep stages in the angiogenic process. From recent approach in oriental medical field with several herb medicines including activating blood flow and removing blood stasis medicine(活血化瘀藥), it may be possible in the future to develope specific anti-angiogenic agents that offer a less toxic potential therapy for cancer and angiogenic disease.

• 공업화학
• /
• 제24권5호
• /
• pp.489-493
• /
• 2013

기존의 EDLC용 활성탄소 대신 리튬이차전지용 탄소류 음전극(천연흑연, 인조흑연, 하드카본, MCMB)을 이용해 리튬이온 커패시터를 구성하면 리튬의 층간 삽입반응으로 인해 기존의 물질보다 에너지 밀도가 큰 전극소재를 개발할 수 있을 것이다. 이 실험에서는 기존 리튬이차전지 음극용 탄소 물질을 대칭 전극으로 사용하여 코인형 커패시터를 제조하여 성능을 측정하였다. 또한 리튬을 미리 삽입시킨 탄소류 전극을 이용한 커패시터를 제조한 후 성능을 측정한 결과, 축전현상이 일어나는 것을 알 수 있었다. 즉 전해액에서 전하분리에 의한 리튬이온의 이동을 보충할 수 있다면 기존의 리튬이온은 탄소류 전극의 층간으로 확산되어 들어가 기존의 대칭성 탄소류 전극의 경우에 비해 축전 용량이 증가한다. 또한 표면적이 매우 큰 graphene oxide를 사용하여 위와 같이 실험한 결과 용량이 크게 나왔으며 이로부터 슈퍼커패시터 전극용 물질에는 높은 비표면적이 중요한 요소로 작용한다는 것을 알 수 있었다.

• Animal cells and systems
• /
• 제6권1호
• /
• pp.69-74
• /
• 2002

Recent evidence has suggested that trunk neural crest cell generally assumed to have equivalent differentiation potentials, demonstrate differentiation bias along the anterior/posterior axis. In amphibian and fish, neural crest cells give rise to three chromatophore types, melanophores, xantho-phores, and iridophores. Each pigment cell type has distinct characteristics but there is speculation about the cellular plasticity that exists among them. Neural crest cells migrate along specific routes, ventromedially and dorsolaterally. Neural crest cells that travel dorsolaterally are the first cells to begin migration in the axolotl and are the major contributors to the visible pigment pattern. Many factors and mechanisms that are responsible for guiding migratory neural crest cells along potential pathways or determining their fate remain unknown. A single lineage of the crest, which becomes restricted to one of the three pigment cell types, gives us the opportunity to examine the existence of neural crest stem cell populations and cellular plasticity. Study presented here showed results from recent in vitro studies designed to identify parameters influencing differentiation events of individual neural crest-derived pigment cell lineages. Melanophore production from neural crest explants originating from different levels along the anterior/posterior axis of wild type-axolotl embryos were compared and demonstrate that the differentiation of melanophores is enhanced in subpopulation of neural crest treated with forskolin. Forskolin (an adenylate cyclase activator) increases intracellular CAMP concentration and eventually activates the protein kinase-A signaling pathway. Melanophore number, melanin content, and tyrosinase activity in explants taken from the anterior-most region of the crest increased significantly in response to forskolin treatment. This study suggests implications of region specific influences and developmental regulation in the development of pigment pattern.

• Journal of Ginseng Research
• /
• 제22권3호
• /
• pp.168-172
• /
• 1998

Systematic electrophoretic analysis of alcohol-soluble proteins and salt-soluble proteins of 247 Panax ginseng (P.g) and Panax quinquefolium (P.q) germplasms seed was carried out on an improved lactate-polyacrylamide gel electrophoresis, a method with high resolving power, good reproducibility and stability. The electrophoregrams of proteins, according to their migration rate, were classified into four groups such as ${\alpha}$, ${\beta}$, ${\gamma}$ and $\omega$ for the alcohol-soluble proteins and three such as I, II and III for the salt-soluble ones. Panax ginseng or Panax quinquefolium had their own unique band pattern distinguishable from each other, regarding as their specific "fingerprint". In this study, 3 of 168 (1.8%) P.g germplasms and 1 of 79 (1.3%) P.q germplasms had their own unique band pattern, showing that P.g and P.q germplasms have poor genetic diversity in species. The band patterns of dry seed and stratified seed (embryo rate=60%) were basically the same. The band number of the F, hybrid of p.gx p.q was exactly equivalent to the number of the common bands plus the specific bands of the two parents, indicating that the difference of band patterns was a genetic trait con- trolled by the nuclear genes. The electrophoregram of F1 of P.g x P.q could be predicted by that of the two parents and the band pattern of the F1 hybrids could be demnonstrated by that of the mixed seed extract from the two parents.

• 한국재료학회지
• /
• 제4권5호
• /
• pp.502-509
• /
• 1994

dynamic strain gage와 12bit AD(analog to digital converter)를 이용한 새로운 제진특성 측정 장치를 제작하였다. 이 장치를 이용하여 일반재료와 고제진재료의 제진특성을 연구하였다. 또한 열처리 조건, 초기 진동 진폭, 그리고 내부응력의 변화에 따른 SDC(specific damping capacity)변화에 관하여 연구하였다. 일반재료와 제진재료의 비교에서, 제진재료는 진동을 가한 후 0.4초 이내에 진동 진폭이 거의 사라졌지만, 같은 시간에 일반재료의 진동 진폭은 거의 감소하지 않았다. Fe-16wt. %Cr계 합금의 제진 특성은 노냉일 때 SDC max 가 40%이상이었고, Fe-5.5wt.%Ai합금의 제진 특성은 공냉일 때 SDC max값이 30%이상이었다. 초기 진동 진폭이 증가할수록 최대 제진 특성치는 낮은 진동 진폭 영역으로 이동하였다. 제진 특성은 내부 응력이 증가할수록 급격한 감소를 보였으며, 본 연구에서 개발한 제진측정 장치는 낮은 진동 진폭의 영역에서 정확한 제진 특성 측정이 가능하였다.