• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.6
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• pp.643-648
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• 2010

Portable fuel cells are commonly operated in the dead-end mode because of such as high fuel utilization. However, the performance of such systems deteriorates continuously with an increase in the amount of by-products such as water vapor and nitrogen. In this study, to verify the effect of water vapor on Proton Exchange Membrane Fuel Cells (PEMFCs), constant-load experiments were carried out for a current density of 600 mA/cm2 and a voltage of 0.4 V, respectively. The performance of the cell was more stable under constant voltage conditions than under constant current density conditions. Condensed water accumulated in the anode channel near the cell outlet. The experimental results show how the relative humidity (RH = 0.15, 0.4 and 0.75) of air at the cathode side affect the performance of PEMFCs with dead-end anode. At RH values higher than 0.15, the mean power density increased by up to 51% and the mean purge duration decreased by up to 25% compared to the corresponding initial values.

• Korean Journal of Animal Reproduction
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• v.26 no.3
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• pp.205-214
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• 2002

There are many methods to introduce exogenous DNA into embryo to produce transgenic animals. Exogenous gene can be integrated into oocyte by sperm vector. In this study, sperm was used as a vector for a transgene, which is encoding enhanced green fluorescent protein (EGFP). The objective of this study was to investigate the expression of exogenous gene in bovine embryos after injection of spermatozoa cocultured with EGFP DNA fragment. Spermatozoa were plunged into liquid nitrogen and thawed several times or shook in 0.2% Triton X-100 to remove sperm membrane followed by DTT treatment. The injected oocytes were co-cultured with vero cells in CR1aa, and expression of EGFP gene was observed under fluorescent microscope. Blastocyst formation rates of oocytes injected with sperm treated with DTT, DTT-freezing or DTT-Triton X-100 were 34.7, 39.4 and 31.9%, respectively. The rates of EGFP expression in oocytes injected with 54 ng DNA after DTT-treated, DTT-freezing and DTT-Triton X-100-treated sperm were 0, 19.1 and 13.9%. On the other hands, expression rate of oocytes injected with sperm cocultured with 13.5, 27 and 63.5 ng of EFGP DNA were 6.7, 9.0 and 5.1%, respectively. When intact sperm was mixed with 63.5 ng/${mu}ell$ EGFP DNA fragment, and then electroporated before injection, the expression rate of injected oocyte was 2%. Unexpectedly, electro-poration could not increase the expression rate. These results suggest that sperm can be used as a transgene vector, even if the efficiency was low (19.1%).

• 한국유가공학회:학술대회논문집
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• 1997.05a
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• pp.41-61
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• 1997

젖산균의 유전자 연구를 촉진하기 위해 간단하고 신속한 plasmid DNA의 분리방법과 electro-poration을 이용하여 vector plasmid의 간단하고 신속한 전이방법을 얻기 위해 젖산균의 형질전환에 영향하는 요인에 대하여 연구하였으며 연구결과는 다음과 같다. 1. O'Sullivan과 Klaenhammer의 방법을 개선하여 젖산균 plasmid DNA의 분리에 좋은 결과를 얻을 수 있는 신속하고 쉬운 방법을 고안하였으며, genomic DNA 분리에 이용되는 guanidium thio-cyanate 처리방법을 plasmid의 분리에 적용할 수 있었다. 2. L. casei, L. acidophilus. L. delbruekii var. bulgaricus. L. brevis와 L. plantarum 균주에서 plasmid를 확인하였으며, 돼지 분에서 분리된 L. lactis ssp. lactis. L. fermentum과 L. plantarum에서도 plasmid를 분리 확인하였다. 3. Lactococci의 plasmid분리는 lactobacilli와는 달리 mutanolysin의 처리없이도 잘 되었으며, L. lactis ssp. lactis와 Ent. faecalis에서 plasmid를 확인하였다. 4. E. coli plasimd 분리에 이용되는 MPS membrane filter 방법으로 젖산균 plasmid pLZ12의 분리가 가능하였으나, 세포파편이 filter를 막아 사용에 어려움이 있는 것으로 확인되었다. 5. Plasmid 분리없이 electroporation을 이용한 세포 대 세포 전이법으로 간편하고 빠르게 E. coli DH5${\alpha}$에 E. coli Jm109의 plasmid pBX19, pBR322를 전이시켰다. 6. L. lactis ssp. lactis 균주에 lysozyme 처리시 30${\sim}$80%의 생존율을 보였으며, 대부분의 L. acidophilus 균주의 경우 약 70%의 생존율을 보였다. L. casei 102S의 경우는 45분간 처리 시에도 100%의 생존율을 보였다. 8. L. lactis ssp. lactis 균주에 pLZ12를 6.0kV에서 전이시킨 결과 12.5kV에서보다 형질전환 효율이 훨씬 높았으며 lysozyme 처리에 의해 형질전환 효율이 증가되었다. 9. L. acidophilus 균주에 pLZ12를 전이시 6.0kV에서는 전이가 모두 이루어졌으나, 12.5kV에서는 L. acidophilus WIESBY와 NCFM에서 전이가 이루어지지 않았으며, lysozyme 처리 후 pLZ12를 전이시켰을 때 12kV보다 6.0kV에서 형질전환 효율이 증가되었다. 10. Gene Pulser와 Progenitor II를 사용하여 pLZ12를 L. lactis ssp. lactis 균주에 전이하였을 때 Gene Pulser에 비해 Progenitor II의 형질전환 효율이 현저히 떨어졌다. L. acidophilus HY7008과 HY7001은 두 기기 모두 형질전환이 이루어졌으나, L. acidophilus WEISBY와 NCFM은 Progeni-tor II에서 전이가 일어나지 않았으며, Gene Pulser에서 전이균주를 얻어 두 electroporator간에 형질전환 효율의 차이를 보였다. 11. L. casei 102S에 pLZ12를 electroporation시 낮은 전압에서 형질전환 효율이 비교적 좋았으며, 배양 시기를 달리하여 전이시켰을 때 대수생장 말기의 세포가 형질전환 효율이 좋았다. 12. L. casei 102S세포를 각각 10% glycerol, EB, 2차 증류수 등에 녹여 electroporation을 실시하였을 때 각각 $3.8{\times}10^3$, $5.0{\times}10^2$,1.5${\times}10^2$cfu의 형질전환 효율을 보였으며, 1.0mM HEPES, TE buffer를 사용하였을 때에는 전이가 이루어지지 않았다. 13. Plasmid pLZ12의 농도를 달리하여 electroporation을 하였을 때 형질전환 효율이 농도에 비례하여 증가하였다. 14. L. casei 102S에 대수생장 말기의 세포를 채취하여 10% glycerol, 200 Ohms, 25 ${\mu}$FD, 10kV/cm로 plasmid pLZ12를 electroporation할 때 최대 형질전환 효율인 3.8${\times}$10$^{3}$cfu를 얻었으며, lysozyme 처리가 다른 젖산균과는 달리 형질전환 효율을 증가시키지 못하였다. 15. L. casei 102S 세포를 10% glycerol과 EB에 녹여 -20$^{\circ}C$에서 냉동시킨 다음 1일과 7일 후의 세포를 electroporation한 결과 냉동시 세포에 손상을 주는 것으로 인식되었다.

• Polymer(Korea)
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• v.35 no.1
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• pp.35-39
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• 2011

In this work, mesoporous carbons (CMK-3) were prepared by a conventional templating method using mesoporous silica (SBA-15) for using catalyst supports in polymer electrolyte membrane fuel cells (PEMFCs). The CMK-3 were chemically activated to obtain high surface area and small pore diameter with different potassium hydroxide (KOH) amounts, i.e., 0, 1, 3, and 4 g as an activating agent. And then Pt-Ru was deposited onto activated CMK-3 (K-CMK-3) by a chemical reduction method. The characteristics of Pt-Ru catalysts deposited onto K-CMK-3 were determined by surface area and pore size analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and inductive coupled plasma-mass spectrometry (ICP-MS). The electrochemical properties of Pt-Ru/K-CMK-3 catalysts were also analyzed by cyclic voltammetry (CV). From the results, the K3g-CMK-3 carbon supports activated with 3 g KOH showed the highest specific surface areas. In addition, the K3g-CMK-3 led to uniform dispersion of Pt-Ru onto K-CMK-3, resulted in the enhancement of elelctro-catalystic activity of Pt-Ru catalysts.

• Applied Microscopy
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• v.9 no.1
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• pp.57-69
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• 1979

The ultrastructural changes of embryo and endosperm cells were observed during the green fruit with embryo about $250{\mu}$ long to germination. 1. In the embryo cells of green fruit with embryo about $250{\mu}$ long, mitochondrial cristae and plastid are undifferentiated and dictyosome are occasionally observed. There are electron-opaque globoids in the vacuole and a lot of spherosomes in the outer layer of smooth endoplasmic reticulum. Endosperm is filled with spherosomes and electron-opaque protein bodies surrounded by spherosomes, and due to these, other organelle are not observed. 2. In the embryo cells of seeds with red seed coat, mitochondrial cristae are well developed, electron-opaque globoids increased, and vacuoles are enlarged. In the endosperm, however, spherosomes increased, protein bodies are enlarged, and electron-opaque globoidal crystals are dispersed within them. 3. In the procambium and epicotyl cells of dehiscent seed, Golgi vacuoles and vesicles are well developed, and mitochondrial cristae are also well differentiated. Spherosomes are numerously present and radicle cells, peripheral cells of hypocotyl, and vacuoles of cotyledon are well differentiated. Endosperm is filled with spherosomes containing electron-opaque granules and protein bodies are surrounded by a single membrane. There are acid phosphatase around globoids and spherosomes. 4. At the time of seeding, spherosomes markedly increased in the outer layer of cotyledon and protein bodies are also observed. Cell organelles are differentiated and plastids containing starch are also present. 5. In the outer $2{\sim}3$ layers of cotyledons, radicle cells, and peripheral cells of hypocotyl during post-seeding to germination, spherosomes and plastids with starch increased, and mitochondria and microbodies are also found around the nucleus of embryo cells. With approaching, the germination stage, in the endosperm contacting with embryo, vacuoles are well differentiated but spherosomes decreased. There increased electron-opaque materials within vacuoles. In other endosperm, with the decrease of spherosome, mitochondria increased and electro n-opaque globular bodies are formed and gradually increased. The outer layer of protein bodies are reduced while electron-transparent portions are enlarged and fused together to occupy the outer layer where small particles are formed. 6. In the endosperm of germination stage, spherosomes decreased while protein bodies, are fused together to form 2 or 3 within a cell.