• Structural Engineering and Mechanics
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• 제53권5호
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• pp.867-880
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• 2015

Mechanical fastening is still one of the main methods used for joining components. Different techniques have been applied to reduce the effect of stress concentration of notches like fastener holes. In this work we evaluate the feasibility of combining laser shock peening (LSP) and cold expansion to improve fatigue crack initiation and propagation of open hole specimens made of 6061-T6 aluminum alloy. LSP is a new and competitive technique for strengthening metals, and like cold expansion, induces a compressive residual stress field that improves fatigue, wear and corrosion resistance. For LSP treatment, a Q-switched Nd:YAG laser with infrared radiation was used. Residual stress distribution as a function of depth was determined by the contour method. Compact tension specimens with a hole at the notch tip were subjected to LSP process and cold expansion and then tested under cyclic loading with R=0.1 generating fatigue cracks on the hole surface. Fatigue crack initiation and growth is analyzed and associated with the residual stress distribution generated by both treatments. It is observed that both methods are complementary; cold expansion increases fatigue crack initiation life, while LSP reduces fatigue crack growth rate.

• 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.

• 한국수산과학회지
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• 제40권4호
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• pp.226-233
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• 2007

Physiological responses of mullet Mugil haematocheilus to cold shock in winter were investigated. The experimental mullets were initially acclimated at $10.0^{\circ}C$ and then the water temperature was reduced to $-1.2^{\circ}C$ for cold shock experiment. The stress responses was monitored for nearly 50 hours. The parameters monitored include survival rate, plasma alanine aminotransferase (ALT), aspartate aminotransferase (AST), glucose (GLU), total protein (TP), electrolytes $(Na^+,\;K^+,\;Cl^-)$, cortisol and thyroid hormones $(TT_4,\;TT_3,\;FT_4\;and\;FT_3)$. With the exception of the TP and electrolytes, most parameters changed significantly during the cold shock. The survival rate did not change from $10^{\circ}C\;to\;-0.6^{\circ}C$, but decreased significantly below $-1.0^{\circ}C$, and was zero at $-1.2^{\circ}C$. The plasma AST and ALT concentrations increased remarkably from $2.5^{\circ}C\;to\;0.5^{\circ}C$ and from $2.5^{\circ}C\;to\;1.5^{\circ}C$, respectively, and then declined rapidly as the temperature decreased to $-1.2^{\circ}C$. The plasma GLU concentration did not change until -0.5'E, and then the concentration increased significantly at $-1.2^{\circ}C$. The plasma cortisol concentration increased remarkably from $2.5^{\circ}C\;to\;-0.5^{\circ}C$, and then declined at $-1.2^{\circ}C$. The plasma thyroid hormones showed two changes during the cold shock. Both plasma 74 concentrations increased remarkably from $2.5^{\circ}C$\;to\;0.5^{\circ}C$, then declined rapidly until $-1.2^{\circ}C$, while both plasma 73 concentrations decreased significantly from $10^{\circ}C\;to\;2.5^{\circ}C$, and then remained significantly lower than the concentration at $10^{\circ}C$.

• 한국수정란이식학회:학술대회논문집
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• 한국수정란이식학회 2006년도 The 6th Intermational Symposium on Developmental Biotechnology
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• pp.98-99
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• 2006

• Journal of Microbiology and Biotechnology
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• 제15권4호
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• pp.831-837
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• 2005

Low-temperature adaptation and cryoprotection were studied in Leuconostoc mesenteroides SYl, a strain isolated from Kimchi. L. mesenteroides SY1 cells grown in exponential growth phase at $30^{\circ}C$ were exposed to $15^{\circ}C,\;10^{\circ}C$, and $5^{\circ}C$ for 2, 4, and 6 h, respectively, and then frozen at $- 70^{\circ}C$ for 24 h. Survival ratio was measured after the cells were thawed. The freezing-thawing cycles were repeated four times. Preadapted cells survived better than non-adapted control cells, and the highest survival ratio ($96\%$) was observed for cells preadapted for 2 h at $5^{\circ}C$, whereas control cells showed only $22\%$. The 2D gel showed that two proteins (spots A and B) were induced in cells preadapted at lower temperatures. Spots A and B have the same molecular weight (7 kDa), but the pI was 4.6 for spot A and 4.3 for spot B. The first 29 and 15 amino acid sequences from spots A and B were determined, and they were identical, except for one amino acid. A csp gene was cloned, and nucleotide sequencing confirmed that the gene encoded spot A cold shock protein.

• Reproductive and Developmental Biology
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• 제35권3호
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• pp.265-271
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• 2011

This study was undertaken to find out the effect of methyl-beta-cyclodextrin (MBCD) on cold shock and membrane cholesterol quantity of sperm during the freezing process in miniature pigs. For this study, semen ejaculated from PWG M-type miniature pig was diluted that freezing solution (with egg yolk group) and m-Modena B (without egg yolk group) treated with 0, 1, 5, 10 and 20 mM MBCD before freezing process. The diluted semen was monitored sperm ability at room temperature, after cooled until $5^{\circ}C$ and after forzen-thawed for cold shock test of spermatozoa. Also, membrane cholesterol of sperm was extracted by folch solution at the same time sperm ability was assessed for viability and acrosomal status. The membrane cholesterol quantity was measured by thin-layer chromatography (TLC) method. The result, viability and acrosome integrity in semen diluted without egg yolk groups were decreased at all temperature range by increasing of MBCD concentration. In particular, sperm of egg yolk group was showed that significantly higher viability and lower acrosome damage when treated with 5 mM MBCD (p<0.05). The results of TLC experiment, cholesterol amounts were increased with MBCD cocentration in egg yolk, and decreased with MBCD concentration in m-Modena B. In cryopreservation efficiency, there was no significant difference at viability, and acrosomal state of sperm in 5 mM MBCD concentration was significantly lower in acrosome damage than other groups (p<0.05). Therefore, the addition MBCD in egg yolk was protected spermatozoa from cold shock injury. This protective effect of MBCD may be due to addition of sperm membrane cholesterol.

• Asian-Australasian Journal of Animal Sciences
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• 제21권2호
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• pp.190-197
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• 2008

This study was designed to analyze boar sperm to compare motility, acrosome morphology, viability and ATP by various preservation methods between Duroc boar A with cold shock resistance sperm and Duroc boar B with cold shock sensitivity sperm. Semen volume, sperm concentration, motility and normal acrosome between Duroc boar A and B did not show any differences within 2 h after collection. There were no differences in sperm motility and normal acrosome between boar A and B at 1 day of preservation at $17^{\circ}C$ and $4^{\circ}C$, respectively. However, sperm motility and normal acrosome from 2 day of preservation at $17^{\circ}C$ and $4^{\circ}C$, respectively, were higher for boar A than boar B. The frozen-thawed sperm motility and normal acrosome were higher for boar A than boar B. The sperm viability and ATP concentration according to storage period of liquid semen at $17^{\circ}C$ and $4^{\circ}C$ were higher for boar A than boar B. Also, the sperm viability and ATP concentration of frozen-thawed semen were higher for boar A than boar B. In conclusion, we found out that the original quality of boar semen with cold shock resistance sperm played an important role.

• 미생물학회지
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• 제54권1호
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• pp.9-17
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• 2018

저온 환경에서의 생장에 영향을 주는 지방산 합성 관련 유전자 bkdR, sigL, yplP, des들의 역할을 알아보기 위하여 각각 유전자들이 상실된 Bacillus subtilis CU1065와 JH642 돌연변이들을 제조하였다. 이들 유전자들의 저온 민감성을 확인하기 위해 $37^{\circ}C$와 $15^{\circ}C$에서 세포들의 생장을 측정하였다. $37^{\circ}C$에서 야생형과 결실 돌연변이 균주는 거의 유사한 정도의 생장을 보였으나, $15^{\circ}C$에서 오직bkdR 결실 돌연변이만이 야생형에 비해 매우 느린 생장이 관찰되었으며 sigL, yplP 결실의 경우 야생형에 비해 다소 느리거나 유사한 생장을 보였다. bkdR, sigL, yplP 결실에 대한 이중, 삼중 돌연변이를 만들어 LB agar에서 $20^{\circ}C$로 키워 저온생장을 조사한 결과, bkdR 결실이 포함되지 않은 어떤 이중, 삼중 결실들에서는 저온에 민감한 생장을 보이지 않았다. 온도 민감성 특성을 보다 잘 알아보기 위하여 $37^{\circ}C$에서 $OD_{600}=0.4$까지 키워 $15^{\circ}C$로 온도를 내리는 저온충격 조건에서 생장하는 실험을 진행하였다. 이 실험에서 오직bkdR 결실 돌연변이만이 현저히 낮은 생장을 보였으며 추가적인 des 결실은 저온 민감성을 증가시킨다. bkdR은 branched-chain fatty acid을 합성하는 전구물질인 isoleucine, valine, leucine 아미노산을 생산하는 bkd operon을 활성화한다. bkdR 결실 돌연변이의 저온생장에서 이들 아미노산의 저온생장에 미치는 영향을 조사한 결과 isoleucine은 bkdR 결실에 대한 저온 민감성을 회복시켜주나 valine은 저온 민감성을 회복시켜 주지 못하는 결과를 보였다. isoleucine은 분해되어 anteiso-branched 지방산 합성의 전구물질로 만들어지는 반면에, valine은 iso-branched 지방산 합성의 전구물질로 만들어진다. 따라서 저온생장에서 branched-chain fatty acid 중 anteiso-branched 지방산이 중요한 역할을 하고 있음을 알 수 있었다.

• Food Science and Biotechnology
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• 제18권3호
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• pp.788-792
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• 2009

Gamma $({\gamma})-irradiation$ can be used to control pathogens such as Vibrio vulnificus in seafood. The effects of irradiation on microbial cell populations (%) have been studied in order to develop detection methods for irradiated foods. The method used in this study was ethidium bromide monoazide (EMA) real-time polymerase chain reaction (PCR), using V. vulnificus specific primer, EMA, and $SYBR^{(R)}$ Green to discriminate between ${\gamma}-irradiated$ and non-irradiated cells. Confocal microscope examination showed that ${\gamma}-irradiation$ damaged portions of the cell membrane, allowing EMA to penetrate cells of irradidated V. vulnificus. ${\gamma}-Irradiation$ at 1.08 KGy resulted in log reduction ($-1.15{\pm}0.13$ log reduction) in genomic targets derived from EMA real-time PCR. The combination cold/heat shock resulted in the highest ($-1.74{\pm}0.1$ log reduction) discrimination of dead irradiated V. vulnificus by EMA real-time PCR.

• KSBB Journal
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• 제21권6호
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• pp.461-465
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• 2006

본 연구에서는 저온에서 발현이 유도되고 지속적으로 발현된다고 알려진 대장균의 6개의 유전자 (frdA, glpB, hypE, katG, nupG, ompT)에 대한 promoter의 단백질 생산성을 알아보기 위하여 GFP를 reporter 단백질로 이용하여 각각의 promoter들에 대한 $37^{\circ}C$와 $15^{\circ}C$에서의 발현도와 저온 유도성에 대하여 고찰하였다. nupG promoter의 경우 $37^{\circ}C$와 $15^{\circ}C$ 모두에서 지속적인 유전자 발현도를 보였으나 promoter에 의한 저온 유도성은 없는 것으로 판별되었다.