• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.6
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• pp.1405-1415
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• 1994

The soil on the behavior of the nonlinear elastic work-hardening plasticity has a variety of stress paths due to the state of soil and the test conditions. The soil with a specific volume ${\upsilon}$ in principal stress space (${\sigma}_1$, ${\sigma}_2$, ${\sigma}_3$, and ${\upsilon}$v) displays the shape of an irregular hexagonal pyramid with an end cap. With variations of ${\upsilon}$ the size of the cap is changed but its shape remains unchanged and the movement of the cap is controlled by the increase or decrease of the plastic volumetric strain. By reflecting such a property of soil various cap models have been developed by researchers. In this thesis, a constitutive model of soil with a combination of the nonlinear elastic work-hardening plastic cap and the failure surfaces of Mohr-Coulomb (M-C cap model) has been developed. According to the the results of analyses using the work-hardening plastic cap model, the normally consolidated soil under shearing has experienced the work-hardening and plastic flow (movement of the cap). But in the shearing of the overconsolidated soil the elastic behavior is shown until the stress path has reached the failure surface and the cap does not move.

• Journal of Life Science
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• v.18 no.11
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• pp.1507-1512
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• 2008

In spite of long research period for Salmonella typhi, little information is known about the pathogenesis mechanism of human typhoid fever caused by S. typhi due to lack of infection model in animals. A wild-type of S. typhi Ty2 strain requires cysteine to grow on minimal media. We hypothesized that this cysteine requirement may restrict colonization of S. typhi in animals during infection process. Among the S. typhi strains carrying Salmonella typhimurium genomic library, we have isolated three S. typhi transformants growing on minimal media without cysteine. Although there were three ORFs in DNA of pBP71, the STM1490 ORF complemented cysteine auxotrophy of S. typhi. Analysis of the deduced amino acid sequence of the STM1490 homolog in S. typhi revealed that there are differences in two amino acids. Plasmids containing amino acid substitutions in STM1490 supported S. typhi growth on minimal media without cysteine, indicating irrelevance of these two amino acids to STM1490 function. These results tells us that there are other factors or systems involved in cysteine requirement of S. typhi.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.1
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• pp.95-104
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• 2002

A methods to calculate non-linear moment-curvature relations of high-strength PSC flexural members for numerical analysis has been proposed. The moment-curvature relations were calculated with assumptions of design codes and by the layer method. The results of the proposed procedures for moment-curvature relations and numerical analysis were compared with those of pre-existing tests. The absorption energy rate of the design codes was about 30% larger than that of the layer method. The ultimate load and the external work of the layer method were 90% and 85% of those of tests, respectively The ultimate load of the strength design method was 97% of that of tests, but the external work was over-estimated with 122%. The ultimate load and external work by the proposed equation of the CEB-FIP Model Code were 113% and 173% of those of tests, respectively. It show that the use of ultimate strain of 0.0035 should be over-estimated for high-strength concrete. The procedure of non-linear numerical analysis of this research could be stably simulated the behavior of concrete flexural members until the ultimate state, and calculate results of the load-deflection relation and cracking pattern were very similar with those of tests.

• Asian-Australasian Journal of Animal Sciences
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• v.20 no.4
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• pp.569-576
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• 2007

Four hundred and fifty tilapias ($6.77{\pm}0.23$ g) were assigned randomly to six groups to evaluate the feasibility of the tested antibacterial peptides (ABPs) and oligosaccharides as substitutes for antibiotics. The control group was fed with a commercial tilapia diet; other five groups were fed with the same commercial diet supplemented with konjac glucomannan (KGLM), cluster bean galactomannan (CBGAM), and three animal intestinal ABPs derived from chicken, pig and rabbit at 100 mg/kg respectively. After 21 days of feeding, growth, disease resistance, and in vivo anti-adherence were determined. Furthermore, the inhibitory effect of tested agents on adhesion of Aeromonas veronii biovar sobria (A.vbs) strain BJCP-5 to tilapia enteric epithelia in vitro was assessed by cell-ELISA system. As a result, the tested agents supplemented at 100 mg/kg show significant benefit to tilapia growth and disease resistance (p<0.05), and the benefit may be correlated with their interfering in the contact of bacteria with host mucosal surface. Although none of the tested agents did inhibit the growth of BJCP-5 in tryptic soy broth at $100{\mu}g/ml$, all of them did inhibit the adhesion of A.vbs to tilapia enteric epithelia in vivo and in vitro. In vitro mimic assays show that three ABPs at low concentrations of $25{\mu}g/ml$ and $2.5{\mu}g/ml$ have the reciprocal dose-dependent anti-adherence effect. The inhibition of ABPs may be correlated with a cation bridging and/or receptor-ligand binding, but not with hydrophobicity. The KGLM and CBGAM inhibited the adherence of BJCP-5 to tilapia enteric epithelia with dose-dependent manner in vitro, and this may be through altering bacterial hydrophobicity and interfering with receptor-ligand binding. Our results indicate that the anti-adherence of the tested ABPs and oligosaccharides may be one of the mechanisms in promoting tilapia growth and resistance to A.vbs.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.23 no.1
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• pp.27-44
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• 1993

This study was performed to investigate the changes of mandibular condyle by low calcium diet and the effects of irradiation on the bone in osteoporotic state. In order to carry out this experiment, 80 seven-week old Sprague-Dawley strain rats weighing about 150 gm were selected and equally divided into one experimental group of 40 rats and one control group with the remainder. The experimental group and the control group were then subdivided into two group and exposed to irradiation. The two irradiation groups received a single dose of 20 Gy on the jaw area only and irradiated with a cobalt-60 teletherapy unit. The rats in the control and experimental groups were serially terminated by fours on the 3rd, the 7th, the 14th, and the 21st day after irradiation. After termination, both sides of the dead rats mandibular condyle were removed and fixed with 10% neutral formalin. The bone mineral density of mandibular condyle was measured by use of dual energy X-ray bone densitometer(model DDX-alpha, Lunn Corp., U. S. A.). The mandibular condyle was radiographed with Hitex HA-80(Hitex Co., Japan). Thereafter, the obtained radiographs were observed, and the mandibular condyle was further decalcified and embedded in paraffin as the general method. The specimen sectioned and stained with hematoxylin-eosin, PAS and Rabbit Anti-Human Tumor Necrosis Factor-a observed by a light microscope. The obtained results were as follows: 1. In the non-irradiated group with the low calcium diet, the bone mineral density of the condyle was markedly decreased after 14 days, and decrease the number of trabeculae of the condyle and resorption of the calcified cartilaginous zone were observed after 3 days. On microscopic observations, the number nd size of trabeculae were decreased after 7 days of experiment. 2. In the irradiated group with the low calcium diet, the bone mineral density of the condyle was markedly decreased after 14 days and resorption of the calcified cartilaginous zone and decrease the number and coarse of the trabeculae of the condyle were observed. These findings were extended rather than in non-irradiated group with low calcium diet. On microscopic observations, many osteoclasts were detected and the number and size of trabeculae were somewhat decreased after 7 days. Also there was degenerative changes of tissues of bone marrow on the 14th day but that condition was restored on the 21st day of experiment. 3. In the irradiated group with normal diet, the bone mineral density of the condyle was somewhat decreased with times and degree of decrease of the number of trabeculae was somewhat larger than in the non-irradiated group with normal diet. On microscopic observations, the tissues of bone marrow were atrophic and degenerative changes but that condition was restored on the 21st day of experiment. 4. In immunocytochemical findings, in the irradiated and non-irradiated groups with low calcium diet, negative or partial positive response to TNF was observed, but positive response in the normal diet groups.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.305-305
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• 2014

양자점(Quantum dots)은 3차원적 운반자 구속과 낮은 전류와 높은 온도에서 작동하는 나노 크기의 전기적, 광학적 소자로 응용이 적합하기 때문에 그 특성을 이용한 단전자 트랜지스터, 적외선 검출기, 레이저, LED, 태양전지 등 반도체 소자로의 응용연구가 활발히 진행되고 있다. 특히 양자점의 낮은 임계전류밀도와 높은 차동 이득(differential gain), 그리고 고온에서 작동이 용이하여 양자점 레이저로 활용되고 있다. 이러한 분야에 양자점을 응용하기 위해서는 양자점의 운반자 동역학을 이해하고 양자점의 모양, 크기, 크기 분포와 같은 특성 조절이 필요하다. 또한 기존의 연구들은 III-V족 화합물 반도체 양자점에 대한 연구가 대부분이며, II-VI족으로 구성된 연구가 미흡한 상황이기 때문에 II-VI족 화합물 반도체 양자점에 대한 많은 연구가 필요한 상황이다. II-VI 족 화합물 반도체 양자점은 기존의 III-V 족 양자점보다 더 큰 엑시톤 결합에너지(exciton binding energy)를 가지고 있으며, 이러한 특성을 가지는 II-VI 족 화합물 반도체 양자점 중에서도 CdTe 양자점은 높은 엑시톤 결합에너지와 녹색 스펙트럼 영역을 필요로 하는 광학적 장치들에 응용 가능성이 높기 때문에 더욱 주목받고 있다. 본 연구에서는 분자 선속 에피 성장법(Molecular Beam Epitaxy; MBE)과 원자 층 교대 성장법(Atomic Layer Epitaxy; ALE)으로 CdTe/ZnTe 나노구조에서 ZnTe 완충층의 두께에 따른 운반자 동역학 및 광학적 특성을 연구 하였다. 저온 광루미네센스 측정(Photoluminescence; PL) 을 통하여 ZnTe 완충층 두께가 증가할수록 양자점의 광루미네센스 피크가 낮은 에너지로 이동함을 알 수 있었는데, 이는 ZnTe 완충층의 두께가 증가할수록 ZnTe 완충층과 CdTe 양자점의 격자 불일치(lattice mismatch)로 인한 구조 변형력이 감소하고 이에 따라 CdTe 양자점으로 가해지는 변형(Strain)이 감소하여 CdTe 양자점의 크기가 증가했기 때문이다. 그리고 ZnTe 완충층의 두께가 증가할수록 PL 세기가 증가함을 알 수 있었는데, 이는 ZnTe 완충층의 두께가 증가할수록 양자 구속 효과로부터 electronic state와 conduction band edge 사이의 에너지 차이의 증가 때문이다. 또한 시분해 광루미네센스 측정 결과 ZnTe의 두께가 증가할수록 양자점의 소멸 시간이 더 길게 측정되었는데, 이는 더 큰 양자점 일수록 엑시톤 오실레이터 강도가 감소하기 때문에 더 긴 소멸 시간을 나타내는 것을 확인할 수 있었다. 결과적으로 본 연구는 ZnTe 두께 변화를 통해 양자점의 에너지 밴드를 제어할 수 있으며, 양자점의 효율 향상을 할 수 있는 좋은 방법임을 제시하고 있다.

• Journal of Microbiology
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• v.43 no.3
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• pp.285-294
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• 2005

A bacterial strain M4-7 capable of degrading various polyesters, such as poly$(\varepsilon-caprolactone)$, poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxyoctanoate), and poly(3-hydroxy-5-phenylvalerate), was isolated from a marine environment and identified as Pseudomonas alcaligenes. The relative molecular mass of a purified extracellular medium-chain-length poly(3-hydroxyalkanoate) (MCL-PHA) depolymerase $(PhaZ_{palM4-7})$ from P. alcaligenes M4-7 was 28.0 kDa, as determined by SDS-PAGE. The $PhaZ_{palM4-7}$ was most active in 50 mM glycine-NaOH buffer (pH 9.0) at $35^{\circ}C$. It was insensitive to dithiothreitol, sodium azide, and iodoacetamide, but susceptible to p-hydroxymercuribenzoic acid, N-bromosuccinimide, acetic anhydride, EDTA, diisopropyl fluorophosphate, phenylmethylsulfonyl fluoride, Tween 80, and Triton X-100. In this study, the genes encoding MCL-PHA depolymerase were cloned, sequenced, and characterized from a soil bacterium, P. alcaligenes LB19 (Kim et al., 2002, Biomacro-molecules 3, 291-296) as well as P. alcaligenes M4-7. The structural gene $(phaZ_{palLB19})$ of MCL-PHA depolymerase of P. alcaligenes LB19 consisted of an 837 bp open reading frame (ORF) encoding a protein of 278 amino acids with a deduced $M_r$ of 30,188 Da. However, the MCL-PHA depolymerase gene $(phaZ_{palM4-7})$ of P. alcaligenes M4-7 was composed of an 834 bp ORF encoding a protein of 277 amino acids with a deduced Mr of 30,323 Da. Amino acid sequence analyses showed that, in the two different polypeptides, a substrate-binding domain and a catalytic domain are located in the N-terminus and in the C-terminus, respectively. The $PhaZ_{palLB19}$ and the $PhaZ_{palM4-7}$ commonly share the lipase box, GISSG, in their catalytic domains, and utilize $^{111}Asn$ and $^{110}Ser$ residues, respectively, as oxyanions that play an important role in transition-state stabilization of hydrolytic reactions.

• KSBB Journal
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• v.21 no.4
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• pp.286-291
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• 2006

Various ${\beta}$-ionone resistant mutants were isolated from the wild-type red yeast Xanthophyllomyces dendrorhous KCTC 7704. Although the growth of X. dendrorhous KCTC 7704 was strongly inhibited at 0.025 mM ${\beta}$-ionone, one of the ${\beta}$-ionone resistant mutants isolated at 0.1 mM ${\beta}$-ionone by NTG mutagenesis showed rather 70% of relative survival at 0.15 mM ${\beta}$-ionone. Fermentation kinetics study with the mutant was carried out at $20^{\circ}C$ for 4 days in 300-mL baffled flasks. The mutant yielded up to 2.3-fold higher carotenoids content(viz. $1.2{\mu}g$ of total carotenoids per mg of dry cells) compared with the wild-type strain. The production of metabolites such as organic acids could be neglected. Studies on the kinetics with various carbon substrates revealed both an increase in final dry cell mass and a higher total carotenoids content in cell mass with glucose when compared to fructose or sucrose. As a further part of study, the effect of pH on the fermentation kinetics was investigated in glucose-limited chemostat at a dilution rate of $0.04h^{-1}$. When compared to steady-state kinetic parameters obtained at pH 4.0, a significant reduction in cell concentration at pH 3.0 and a lower carotenoids content at pH 5.2 were evident.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.2
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• pp.33-40
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• 2020

Various studies have been conducted on the structural health monitoring using optical fiber. Optical fibers can be used to measure multiple and distributed strain. Among the optical fiber sensors, FBG sensor has advantages of dynamic response measurement and high precision, but the number of measurement points is limited. Distributed fiber sensors, represented by distributed Brillouin sensors, usually have more than 1000 measurement points, but the low sampling rate makes dynamic measurements impossible. In this study, a hybrid nerve sensor system using only the advantages of the FBG sensor and the distributed Brillouin sensor has been proposed. Laboratory experiments were performed to verify the proposed system, and the accuracy and reproducibility were verified by comparing with commercial sensors. Applying the proposed system, dynamic response ambient measurements are used to evaluate the global state of the structure. When an abnormal condition is detected, the local condition of the structure is evaluated by static response measurement using the distributed measurement system. The proposed system can be used for efficient structural health monitoring.

• Applied Microscopy
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• v.40 no.4
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• pp.211-218
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• 2010

The mammalian ovary is innervated by sympathetic and sensory neurons which contribute to regulating several aspects of ovarian function, including blood flow, steroidogenesis and follicular development. The existence of a neural connection between central neurons and the ovary has been rarely reported, but the mechanism underlying integration of ovarian activity to broader neuroendocrine responses has not been reported. We have now used a viral transneuronal tracing technique combined with a conventional retrograde labeling procedure of CT-HRP to demonstrate that oxytocin-producing neurons of the hypothalamus are synaptically connected to the ovary. Since ovarian activity is suppressed but the activity of oxytocin neurons is increased during breast feeding. Our finding that the oxytocinergic neural connection is likely to provide a direct transsynaptic mechanism by which the central nervous system maintains the state of infertility that accompanies lactation in mammals.