• 한국주조공학회지
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• 제25권3호
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• pp.115-122
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• 2005

In the present study, an EMC (Electromagnetic Casting) process, using a segmented Cu cold crucible under a high frequency alternating magnetic field of 20 kHz, was practiced for the fabrication of poly-crystalline Si ingot of 50 mm diameter. The effects of Joule heating and electromagnetic pressure in molten Si were systematically investigated with various processing parameters such as electric current and crucible configuration. A preliminary experimental work was initiated with the pure Al system for the establishment of a stabilized non-contact working condition, and further adapted to the semiconductor-off-grade Si system. A commercialized software such as Opera-3D was utilized in order to simulate electromagnetic pressure and Joule heating. In order to evaluate the meniscus shape of the molten melts, shape parameter was used throughout the research. A segmented graphite crucible, which was attached at the upper part of the cold crucible, was introduced to enhance significantly the heating efficiency of Si melt keeping non-contact condition during continuous melting and casting processes.

• 한국어류학회지
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• 제23권2호
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• pp.145-149
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• 2011

인위적 수온변화에 의한 미꾸라지 피부의 점액세포 반응을 확인하기 위해 고온($32^{\circ}C$)과 저온($4^{\circ}C$)에 적응시킨 실험군의 표피조직을 실온($18^{\circ}C$)의 대조군 집단과 비교 분석하였다. 그 결과, 고온적응 설험군에서는 대조군과 유의한 차이를 보이지 않았으나, 저온적응 실험군에서는 등, 체측, 후두부의 점액세포 수와 크기가 현저하게 증가하는 경향을 보였다(P<0.01). 또한 저온적응 실험군의 수온을 증가시켜 상온에서 재 적응시킨 결과에서도 피부 정액세포의 수와 크기가 현저히 감소하는 경향을 보였다(P<0.01). 따라서 미꾸라지 피부의 점액세포가 저온에 매우 민감하게 반응하는 양상은 어류의 조직학적 환경지표로서 유용할 것으로 여겨진다.

• 미생물학회지
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• 제38권1호
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• pp.45-49
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• 2002

Bradyrhizobium japonicum 은 콩과 식물의 뿌리에 감염하여 뿌리흑을 형성 질소를 고정하는 독특한 능력을 갖는 토양 세균이며 미생물 비료제로 사용되고 있다. 본 연구에서는 저온에서 전처리한 B . japonicum 균주를 여러 가지 환경스트레스 조건에 노출하였을 때 생균수의 변화를 확인하였다. 저온 전처리는 16시간 동안 $4^{\circ}C$의 조건을 유지했다. 다양한 스트레스(알콜, 과산화수소, 고온, 건조)에 노출하였을 때, 저온 전처리한 것이 그렇지 않는 것보다 10~1,000배 정도 높은 생균수를 유지하였다. 이러한 내성중진 현상에 전처리 동안 새로운 단백질 합성이 수반되는 것을 단백질 합성 저해제 인 chloramphenicol을 전처리 과정에 포함하여 확인하였다. 저온 스트레스 내성에 관여하는 유전자를 B. japonicum genome 으로부터 중폭하였고 염기서열 분석을 실시하였다. 실험에서 확인된 B . japonicum의 CSP (Cold shock protein) 단백질의 부분적 아미노산 서열은 이미 확인된 다른 균주의 Csp 단백질과 유사함을 확인하였다.

• Journal of Microbiology and Biotechnology
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• 제20권12호
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• pp.1724-1734
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• 2010

A phosphate-solubilizing bacterial strain isolated from Hippophae rhamnoides rhizosphere was identified as Rahnella sp. based on its phenotypic features and 16S rRNA gene sequence. The bacterial strain showed the growth characteristics of a cold-adapted psychrotroph, with the multiple plant growth-promoting traits of inorganic and organic phosphate solubilization, 1-aminocyclopropane-1-carboxylate-deaminase activity, ammonia generation, and siderophore production. The strain also produced indole-3-acetic acid, indole-3-acetaldehyde, indole-3-acetamide, indole-3-acetonitrile, indole-3-lactic acid, and indole-3-pyruvic acid in tryptophan-supplemented nutrient broth. Gluconic, citric and isocitric acids were the major organic acids detected during tricalcium phosphate solubilization. A rifampicin-resistant mutant of the strain exhibited high rhizosphere competence without disturbance to the resident microbial populations in pea rhizosphere. Seed bacterization with a charcoal-based inoculum significantly increased growth in barley, chickpea, pea, and maize under the controlled environment. Microplot testing of the inoculum at two different locations in pea also showed significant increase in growth and yield. The attributes of cold-tolerance, high rhizosphere competence, and broad-spectrum plant growth-promoting activity exhibited the potential of Rahnella sp. BIHB 783 for increasing agriculture productivity.

• Journal of Microbiology and Biotechnology
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• 제24권11호
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• pp.1484-1489
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• 2014

A novel esterase gene, est01, was successfully unearthed from a biogas digester microbiota metagenomic library. The 1,194 bp est01 gene encodes a protein of 44,804 Da (designated Est01). The amino acid sequence of Est01 shows only moderate (33%) identity to a lipase/esterase. Phylogenetic analysis and biochemical characterization confirmed that Est01 is a new member of family VIII esterases. The purified Est01 from recombinant Escherichia coli BL21 (DE3) showed high hydrolytic activity against short-chain fatty acid esters, suggesting that it is a typical carboxylesterase rather than a lipase. Furthermore, the Est01 was even active at $10^{\circ}C$ (43% activity remained), with the optimal temperature at $20^{\circ}C$, and had a broad pH range from 5.0 to 10.0, with the optimal pH of 8.0. These properties suggest that Est01 is a cold-adaptive esterase and could have good potential for low-temperature hydrolysis application.

• 분석과학
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• 제9권4호
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• pp.325-330
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• 1996

몸무우의 자엽에 저온과 polyamine(PA)을 처리하면 세포내의 환원당과 설탕의 농도가 증가되었고, 가을무우의 자엽에 저온처리를 하면 환원당과 설탕의 농도가 증가되나, 저온과 PA를 동시에 처리하면 세포내에 당류의 농도가 증가되지 않았다. 몸무우 자엽에서는 저온처리에 의해 총 아미노산의 농도는 증가되나, 가을무우에서는 증가되지 않았다. 이 결과는 저온에 예민한 봄무우는 세포내의 삼투조절에 의하여 적응하며, 봄무우와 가을무우 사이에 생리 및 생화학적인 대사가 다름을 보여 주었다. 저온에 예민한 봄무우에서 PA는 저온처리와 함께 상승효과를 보이나, 저온 스트레스에 강한 가을무우에서는 PA 처리로 상승효과를 나타내지 못함은 처음 보고 하는 결과이다.

• Bulletin of the Korean Chemical Society
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• 제32권6호
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• pp.1925-1930
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• 2011

Psychrophilic bacteria have acquired cold-resistance in order to protect themselves against freezing temperatures, which would otherwise be lethal. DnaK/DnaJ/GrpE systems are molecular chaperones which facilitate proper folding of newly synthesized proteins. Efficient folding processes are of great importance especially in a cold environment, such as the Arctic. In order to understand the protection mechanisms of psychrophilic bacteria against cold temperatures, we have explored a genome of KOPRI22215, tentatively identified as Psychromonas arctica, whose genome sequence has not yet been discovered. With an aim of searching for a coding gene of DnaK from KOPRI22215, we have applied a series of polymerase chain reactions (PCR) with homologous primers designed from other Psychromonas species and LA PCR in vitro cloning. 1917 bp complete coding sequence of dnaK from KOPRI22215 was identified including upstream promoter sites. Recombinant plasmids to overexpress PaDnaK along with EcDnaK (DnaK of E. coli) were then constructed in pAED4 vector and the pET-based system to induce PaDnaK expression by IPTG. Characterization assays of expressed PaDnaK were carried out by measuring survival rates upon 4 day incubation at 4 $^{\circ}C$: a refolding assay as molecular chaperone, and ATPase assay for functional activity. Taking account of all the data together, we conclude that PaDnaK was identified, successfully expressed, and found to be more efficient in providing cold-resistance for bacterial cells.

• Asian-Australasian Journal of Animal Sciences
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• 제11권3호
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• pp.265-267
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• 1998

Cattle in Alaska seemed to be tolerant to low blood selenium (Se) although arctic winter energy demands might exacerbate oxidative damage to tissues lacking protection by Se. The thermogenic properities of brown adipose tissue (BAT) and the long cold adaptation period for Alaskan cattle indicates that they might develop BAT. Eighteen mature beef cows with whole blood Se of< 19 ppb were used to examine possible relation-ships among Se deficiency, tissue lesions, and observable BAT. All cows were wintered on a diet low in Se and nine cows were given supplemental Se provided by intraruminal bolus. Blood Se was elevated (p < .05) from November through February by supplemental Se, but body weight and back fat thickness were unaffected (p < .10). Tissues were taken from two Se deficient cows, two cows supplemented with Se, and two cows given large doses of Se (300 mg by injection) four weeks before slaughter. Histopathological examination of 187 samples of fat (7 to 55 from each cow) showed no observable amount of BAT. Examination of other tissues showed no lesions attributable to Se deficiency.

• Bulletin of the Korean Chemical Society
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• 제32권7호
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• pp.2405-2409
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• 2011

The psychrophilic bacteria Psychromonas arctica survives at subzero temperatures by having adapted several protective mechanisms against freezing and oxidative stresses. Many reactive oxygen species are likely generated in P. arctica as a result of reduced metabolic turnover rates. A previous study identified the pasod gene for superoxide dismutase from P. arctica using a series of PCR amplifications. Here, upon cloning into a His-tag fused plasmid, the sod gene from P. arctica (pasod) was successfully expressed by IPTG induction. His-tagged PaSOD was subsequently purified by $Ni^{2+}$-NTA affinity chromatography. The purified PaSOD exhibited a higher SOD activity than that of Escherichia coli (EcSOD) at all temperatures. The difference in activity between PaSOD and EcSOD becomes even more significant at 4$^{\circ}C$, indicating that PaSOD plays a functional role in the cold adaptation of P. arctica in the Arctic.

• Corrosion Science and Technology
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• 제9권2호
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• pp.67-73
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• 2010

Niobium microalloying is effective in hot-rolled and cold-rolled steels by providing a fine-grained microstructure resulting in increased strength. To optimize the strengthening effect, alloy design and hot-rolling conditions have to be adapted. As a key issue the dissolution and precipitation characteristics of Nb are discussed in particular with regard to the run-out table conditions. It is then considered how the hot-rolled microstructure and the solute state of Nb interact with the hot-dip galvanizing cycle. The adjusted conditions allow controlling the morphology and distribution of phases in the cold-rolled annealed material. Additional precipitation hardening can be achieved as well. The derived options can be readily applied to produce conventional HSLA and IF high strength steels as well as to modern multiphase steels. It will be explained how important application properties such as strength, elongation, bendability, weldability and delayed cracking resistance can be influenced in a controlled and favorable way. Examples of practical relevance and experience are given.