• Journal of Microbiology and Biotechnology
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• 제16권12호
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• pp.1968-1976
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• 2006

Recombinant E. coli ACV 1003 (recA:: lacZ) was used to measure low concentrations of DNA-damaging chemicals, which produce $\beta$-galactosidase via an SOS regulon system. Very low $\beta$-galactosidase activities of less than 0.01 unit/ml, $\beta$-galactosidase produced through an SOS response corresponding to the 10 ng/ml (ppb) of DNA damaging chemicals in the environment, can be rapidly determined by using an alternative interferometric biosensor with optically flat thin films of porous silicon rather than by the conventional time-consuming Miller's enzyme assay as well as the ELISA method. fu order to enhance the sensitivity in the interferometry, it needs to obtain more uniform distribution and higher biolinking efficiency, whereas interferometric sensing is rapid, cheap, and advantageous in high throughput by using a multiple-well-type chip. In this study, pore size adjusted to 60 nm for the target enzyme $\beta$-galactosidase to be bound on both walls of a Si pore and a calyx crown derivative was apllied as a more efficient biolinker. Furthermore, anti-$\beta$-galactosidase was previously functionalized with the biolinker for the target $\beta$-galactosidase to be specifically bound. When anti-$\beta$-galactosidase was bound to the calyx-crown derivative-linked surface, the effective optical thickness was found to be three times as high as that obtained without using anti-$\beta$-galactosidase. The resolution obtained was very similar to that afforded by the time-consuming ELISA method; however, the reproducibility was still unsatisfactory, below 1 unit $\beta$-galactosidase/ml, owing to the microscopic non-uniform distribution of the pores in the etched silicon surface.

• 한국재료학회지
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• 제10권1호
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• pp.7-14
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• 2000

본 연구는 무금속프탈로시아닌 색소계를 이용한 전자사진 감광체의 개발에 관한 것이다. 전하발생물질로서는 각종 형태의 무금속프탈로시아닌을 사용했고, 결합제로서는 각종 폴리머를 사용했으며, 전하이동물질로서는 히드라존유도체나 아연착화합물을 사용했다. 전하발생물질로서 사용한 ${\alpha}-$, ${\beta}-$, x형의 프탈로시아닌중에서는 x형의 무금속프탈로시아닌($x-H_2Pc$)의 경우가 가장 좋은 감도를 보였다. 전하발생물질로서는 $x-H_2Pc$를, 전하수송물질로서는 히드라존유도체를 사용했을 때, 다른 감광체들과 비교하여 73.1%의 높은 $1.50lux{\cdot}sec$의 좋은 감도를 보였다.

• Transactions on Electrical and Electronic Materials
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• 제18권5호
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• pp.287-297
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• 2017

Novel power system stabilizers (PSSs) have been proposed to effectively dampen low frequency oscillations (LFOs) in multi-machine power systems and have attracted increasing research interest in recent years. Due to this attention, recently, fractional order controllers (FOCs) have found new applications in power system stability issues. Here, a tilt-integral-derivative power system stabilizer (TID-PSS) is proposed to enhance the dynamic stability of a multi-machine power system by providing additional damping to the LFOs. The TID is an extended version of the classical proportional-integral-derivative (PID) applying fractional calculus. The design of the proposed three-parameter tunable TID-PSS is systematized as a nonlinear time domain optimization problem in which the tunable parameters are adjusted concurrently using a modified group search optimization (MGSO) algorithm. An integral of the time multiplied squared error (ITSE) performance index is considered as the objective function. The proposed stabilizer is simulated in the MATLAB/SIMULINK environment using the FOMCON toolbox and the dynamic performance is evaluated on a 3-machine 6-bus power system. The TID-PSS is compared with both classical PID-PSS (PID-PSS) and conventional PSS (CPSS) using eigenvalue analysis and time domain simulations. Sensitivity analyses are performed to assess the robustness of the proposed controller against large changes in system loading conditions and parameters. The results indicate that the proposed TID-PSS provides the better dynamic performance and robustness compared with the PID-PSS and CPSS.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.487-492
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• 2007

The enhancement of the service life of damaged or cracked structures is a major issue for researchers and engineers. The hierarchical void element with the integrals of Legend polynomials is used to characterize the fracture behavior of unpatched crack as well as repaired crack with bonded composite patches by computing the stress intensity factors and stress contours at the crack tip. The numerical approach is based on the v-version degenerate shell element including the theory of anisotropic laminated composites. Since the equivalent single layer approach is adopted in this study, the proposed element is necessary to represent a discontinuous crack part as a continuum body with zero stiffness of materials. Thus the aspect ratio of this element to represent the crack should be extremely slender. The sensitivity of numerical solution with respect to energy release rate, displacement and stress has been tested to show the robustness of hierarchical void element as the aspect ratio is increased up to 2000. The stiffness derivative method and displacement extrapolation method have been applied to calculate the stress intensity factors of Mode I problem.

• 한국미생물·생명공학회지
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• 제17권3호
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• pp.193-197
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• 1989

Spanner chain의 탄소수가 2,4 또는 6개의 alkylene diisothiocyanate를 합성 후 cefadroxil-2DMF와 반응시켜 spanner chain의 탄소수 2, 4 또는 6개로 연결되어 있고 양쪽에 thioureido group과 $\beta$-lactam ring을 가진 bivalent ligand 구조의 alkylene bisdithioureido $\beta$-lactam 유도체를 합성하고 그 화합물들의 항균작용에 대하여 연구하였다. 그 유도체의 I식 화합물은 $C_{36}$H$_{38}$N$_{8}$O$_{10}$S$_4$, II식 화합물은 $C_{38}$H$_{42}$N$_{8}$O$_{10}$S$_4$, III식 화합물은 $C_{40}$H$_{46}$N$_{8}$O$_{10}$S$_4$의 분자식이다. $\beta$-lactam 감수성 균주에 대한 항균력은 spnner chain의 탄소수가 많을수록 감소하였다.

• 분석과학
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• 제19권1호
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• pp.107-114
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• 2006

본 연구에서는 trimethylsilyl (TMS) 및 trifluoroacetyl (TFA)유도체화를 이용하여 소변여지에서 대사이상 질환을 신속하게 스크리닝하는 GC/MS 분석법을 개발하였다. 유기산과 아미노산을 동시에 유도체화하기 위해 메틸오렌지를 지시약으로 하여 $60^{\circ}C-70^{\circ}C$에서 15-20 분간 카르복실기는 TMS로 아미노기는 TFA로 유도체한 후 GC/MS-SIM으로 분석하였다. 유기산과 아미노산의 직선성의 범위는 0.001-50 mg이었고, 소변에서의 검출한계는 10-200 ng, 정량한계는 80-900 ng 이었다. 직선성을 보이는 범위에서의 상관계수(R2)는 0.994-0.998이었고, 회수율은 methylcitric acid와 glycine을 제외하고 80-100%를 보였다. 이 방법은 기존의 유기산분석에는 GC/MS를 아미노산 분석에는 아미노산분석기를 사용하는 것과 비교할 때 GC/MS만 사용하여 동시에 유기산과 아미노산을 분석함으로써 전처리가 간단하고 짧은 분석시간과 우수한 감도, 정확도, 정밀도를 보여 주었다. 정상인과 대사이상질환 환자의 검체에 적용해 보았을 때, 본 분석방법은 유기산과 아미노산대사이상의 유전성대사질환 환자의 스크리닝, 진단 및 모니터링에 임상적으로 유용함을 보여주었다.

• Molecules and Cells
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• 제25권2호
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• pp.224-230
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• 2008

Ceramides are well-known second messengers that induce apoptosis in various kinds of cancer cells, and their effects are closely related to radiation sensitivity. Phytoceramides, the yeast counterparts of the mammalian ceramides, are also reported to induce apoptosis. We investigated the effect of a novel ceramide derivative, N-acetylphytosphingosine (NAPS), on the radiosensitivity of NCI-H460 human lung carcinoma cells and its differential cytotoxicity in tumor and normal cells. The combination of NAPS with radiation significantly increased clonogenic cell death and caspase-dependent apoptosis. The combined treatment greatly increased Bax expression and Bid cleavage, but not Bcl-2 expression. However, there was no effect on radiosensitivity and apoptosis in BEAS2B cells, which derive from normal human bronchial epithelium. Cell proliferation and DNA synthesis were significantly inhibited by NAPS in both NCI-H460 and BEAS2B cells, but only the BEAS2B cells recovered by 48h after removal of the NAPS. Furthermore, the NCI-H460 cells underwent more DNA fragmentation than the BEAS2B cells in response to NAPS. Our results indicate that NAPS may be a potential radiosensitizing agent with differential effects on tumor vs. normal cells.

• Macromolecular Research
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• 제13권6호
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• pp.467-476
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• 2005

The main objective of this study was to develop and characterize pH-sensitive biodegradable polymeric materials. For pH-sensitivity, we employed three kinds of moieties: 2-amino-3-(lH-imidazol-4-yl)-propionic acid (H), N-[4-( 4,6-dimethyl-pyrimidin-2ylsulfamoyl)-phenyl]succinamic acid (SM), and 2- {3-[ 4-( 4,6-dimethyl-pyrim­idin- 2-ylsulfamoyl)-phenylcarbamoyl]-propionylamino} -3-(3 H - imidazol-4-yl)-propionic acid (SH). The pH -sensitive diblock copolymers were synthesized by ring opening polymerization and coupling reaction from poly(ethylene glycol) (MPEG), $\varepsilon$-caprolactone (CL), D,L-lactide (LA) and pH-sensitive moieties. The pH-sensitive SH molecule was synthesized in a two-step reaction. The first step involved the synthesis of SHM, a methyl ester derivative of SH, by coupling reaction of SM and L-histidine methyl ester dihydrochloride, whereas the second step involved the hydrolysis of the same. The synthesized SM, SHM and SH molecules were characterized by FTIR, $^{1}H$-NMR and $^{13}C$-NMR spectroscopy, whereas diblock copolymers and pH-sensitive diblock copolymer were characterized by $^{1}H$-NMR and GPC analysis. The critical micelle concentrations were determined at various pH conditions by fluorescence technique using pyrene as a probe. The micellization and demicellization studies of pH-sensitive diblock copolymers were also done at different pH conditions. The pH-sensitivity was further established by acid-based titration and DLS analysis.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.1038-1043
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• 2003

There are many industrial applications including thin-body structures such as fins. For the numerical modeling of radiation of sound from thin bodies, the conventional boundary element method (BEM) using the Helmholtz integral equation fails to yield a reliable solution. Therefore, many researchers have tried to solve the thin-body acoustic problems. In the area of the design sensitivity analysis (DSA) and optimization methods, however, there has been just a few study reported. Especially fur the thin-body acoustics, however, no further study in the DSA and optimization fields has been reported. In this research, the normal derivative integral equation is adopted as an analysis formulation in the thin-body acoustics, and then used for the sizing DSA and optimization. Since the gradient-based method is used for the optimization, it is important to have accurate gradients (design sensitivities) of the objective function and constraints with respect to the design variables. The DSA formulations are derived through chain-ruled derivatives using the finite element method (FEM) and BEM by using the direct differentiation and continuum variation concepts. The proposed approaches are implemented and validated using a numerical example.

• 대한기계학회논문집
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• 제11권1호
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• pp.82-87
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• 1987

본 논문에서는 열전달문제 역시 변분형으로 전환될 수 있음에 착안하여 전미 분 개념을 도입해서 전도와 대류가 있는 열전달모델에서 주어진 면적 제한조건을 만족 시키며 지정된 경계에서의 온도가 주어진 온도에 가장 근접할 수 있는 모델의 형상을 찾는 방법을 연구하였다. 어떤 물질의 열전달 상태를 바꾸어 경계에서의 온도를 원 하는 바대로 조정하는 문제는 실제 공정에서 중요한 경우가 많다.해석시 열전달 상 태 방정식과 adjoint식은 6절점 삼각형 등계수 요소의 유한 요소법을 이용하여 해석하 였다.설계민감도의 정확한 계산을 위해서는 임의의 형상변화에 따른 경계에서의 수 치적분이 정확해야 하므로 경계를 곡선으로 표시할 수 있는 등계수 요소가 필요하다. 설계 민감도 해석이 진행된 후에는 최적화 기법의 하나인 미분벡터 투영법(Gradient Projection Method)을 사용하여 최적화를 시도했다. 최적설계 과정중 매번 계산결과 에 의해 형상의 변화가 진행되므로 그때마다 유한 요소 모델을 적절히 변화시켜 주어 야 한다. 모델의 경계는 3차함수로 근사화하여 형상이 부드러운 곡선이 되도록 했 으며 설계변수는 근사화한 3차함수를 결정할 수 있도록 정하면 되나 본 연구에서는 모 델의 변화에 따른 y좌표의 변화는 없다고 가정하여 모델경계의 세점을 취해 그 점들의 x좌표를 설계변수로 했다.