• BMB Reports
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• 제29권6호
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• pp.507-512
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• 1996

The NADPH oxidase of phagocytes catalyzes the reduction of oxygen to $O_{2}^{-}$ at the expense of NADPH The enzyme is dormant in resting neutrophils and hecomes activated on stimulation. During activation. $p47^{phox}$ (phagocyte oxidase factor), a cytosolic oxidase subunit, becomes extensively phosphorylated on a number of serines located between S303-S379. Although the biochemical role of phosphorylation is speculative, it has been suggested that phosphorylation could neutralize the strongly cationic C-terminal which may result in the change of conformation of $p47^{phox}$ and subsequent translocation of this protein and other cytosolic components to the membrane. In order to mimic the effect of phosphorylation in terms of neutralizing the positive charges, recombinant $p47^{phox}$ was treated with phenylglyoxal, which removes positive charges of arginine residues. Modification of recombinant $p47^{phox}$ resulted in the activation of oxidase in a cell-free translocation system as well as a conformational change in recombinant $p47^{phox}$ which may be responsible for the activation of the enzyme.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.12-12
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• 2010

By using scanning tunneling microscopy/spectroscopy (STM/S), we can make images of various physical properties in nanometer-scale spatial resolutions. Here, I demonstrate imaging of two electron-correlated subjects; screening and superconductivity by STM/S. The electrostatic potential around a charge is described with the Coulomb potential. When the charge is located in a metal, the potential is modified because of the free electrons in the host. The potential modification, called screening, is one of the fundamental phenomena in the condensed matter physics. Using low-temperature STM we have developed a method to measure electrostatic potential in high spatial and energy resolutions, and observed the potential around external charges screened by two-dimensional surface electronic states. Characteristic potential decay and the Friedel oscillation were clearly observed around the charges [1]. Superconductivity of nano-size materials, whose dimensions are comparable with the coherence length, is quite different from their bulk. We investigated superconductivity of ultra-thin Pb islands by directly measuring the superconducting gaps using STM. The obtained tunneling spectra exhibit a variation of zero bias conductance (ZBC) with a magnetic field, and spatial mappings of ZBC revealed the vortex formation [2]. Size dependence of the vortex formation will be discussed at the presentation.

• Carbon letters
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• 제8권3호
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• pp.184-190
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• 2007

Carbon Nano Tubes could be either metallic or semi-conducting in nature, depending on their diameter. Its photocatalytic behavior has given an impetus to use it as an anti-microbial agent. More than 95% Escherichia coli and Staphylococcus aureus bacteria got killed when exposed to Carbon Nano Tubes for 30 minutes in presence of sunlight. Carbon Nano Tubes are supposed to have smooth surface on to which it accumulates positive charges when exposed to light. The surface that is non illuminated has negative charge. At the cellular level microorganisms produce negative charges on the cell membrane, Therefore damaging effect of multi walled carbon nano tubes (exposed to light) on the microorganisms is possible. In this paper, photo catalytic killing of microbes by multi walled carbon nano tubes is reported. Killing was due to damage in the cell membrane, as seen in SEM micrographs. Moreover biochemical analysis of membrane as well as total cellular proteins by SDS PAGE showed that there was denaturation of membrane proteins as well as total proteins of both the microbes studied. The killed microbes that showed a decrease in number of protein bands (i.e. due to breaking down of proteins) also showed an increase in level of free amino acids in microbes. This further confirmed that proteins got denatured or broken down into shorter units of amino acids. Increased level of free amino acids was recorded in both the microbes treated with multi walled carbon nano tubes and sunlight.

• 한국항만경제학회지
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• 제32권3호
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• pp.21-33
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• 2016

두 국가에 위치한 국내 기업과 외국 기업이 경쟁하는 복점시장에서, 국가의 무역 정책에 따른 항만운영구조(국영화/민영화) 선택 전략을 분석한다. 그리고 항만 운영구조 선택에 따른 각 기업의 이윤, 항만 사용료 수준과 항만의 이윤, 사회후생을 비교분석하고, 자유무역 정책과 관세 정책의 각 균형 비교분석을 통해 최적 전략을 도출한다. 그 결과, (i) 관세 정책에서, 운송비와 상관없이 정부는 항만 국영화를 선택하는 것이 지배전략이다. (ii) 관세 정책에서, 항만은 높은 항만 사용료를 설정하는 민영화 정책의 경우 더 높은 이윤을 달성하며, 국가와 항만의 이해관계 불일치가 발생한다. (iii) 관세 정책과 상관없이 낮은 운송비 수준이라면, 정부는 항만 국영화 선택을 통해 더 높은 후생을 달성하며, 높은 운송비 수준이라면 항만 운영구조(민영화/국영화)에 상관없이 정부는 자유무역 정책의 경우가 더 높은 후생을 달성한다.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 2000년도 추계학술대회 및 정기총회
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• pp.302-305
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• 2000

The operation of a networked computing system (NCS), such as Internet, can be viewed as a resource allocation problem, and can be analyzed using the techniques of mathematical modeling. We define a general NCS and translate that setup into a model of an economy. The preferences of users are taken as primitives, and servers in the network are viewed as productive firms with priority input queues. Each sewer charges a rental price for its services by priority class. We characterize optimal system allocation, and derive formulae for supporting rental prices and priority premia such that the aggregated individual user demands do not exceed optimal levels and waiting-time expectations are correct. Our economic approach has the added benefit of providing a sound basis for evaluating NCS investment alternatives, using a process analogous to free entry and exit in free-enterprise economies.

• Tribology and Lubricants
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• 제30권5호
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• pp.247-255
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• 2014

Charged polymer chains, i.e., polyelectrolytes, are known to show superior aqueous lubricating properties compared to those of neutral polymer chains, especially in brush conformation. This is primarily because of the incorporation of a large amount of counterions within the polymer layers and the consequently increased osmotic pressure. However, this effect is active only when the polymer chains remain immobilized even under tribostress, which is not realistic for high-contact pressure tribological applications, especially when they are irreversibly immobilized on tribopair surfaces. In contrast, with free polymers, which can be included as surface-active additives in the base lubricant (water), long-term lubricating performance based on "self-healing" properties is readily expected. In order to assess whether the superior aqueous lubricating properties of polyelectrolyte chains are valid for free polymers too, this study reviews recent studies on the tribological properties of many charged biopolymer and synthetic copolymers at a nonpolar, hydrophobic interface. In contrast to the irreversibly immobilized polyelectrolyte chains, free polyelectrolyte chains show inferior aqueous lubricating properties compared to their neutral counterparts owing to charge accumulation and the consequently impeded surface adsorption on the nonpolar surface. Nevertheless, bovine submaxillary mucin (BSM), a representative biopolymer, shows a sufficiently effective surface adsorption and aqueous lubricating capabilities even at neutral pH without losing the polyanionic characteristics.

• E2M - 전기 전자와 첨단 소재
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• 제7권1호
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• pp.32-41
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• 1994

In this study, the TSC spectroscopy has been applied to investigate the influence of structural change due to a process of curing reaction on the electrical properties of epoxy composites cured with acid-anhydride. Five TSC peaks appeared in -160-250[.deg.C]: in the low temperature region below glass transition temperature(T$\_$g/), three relaxation mode peaks due to action of side chains, substitution group or terminal groups have been observed, a peak associated with T$\_$g/, appeared in 110[.deg. C] and p peak due to ionic space charges located in 150[.deg.C]. Each peak was separated into elementary peaks by the partial polarization procedure, and the distribution of activation energy and relaxation time were analized to clearify the origin of each peak. Also, overaboundantly added hardener separated a .betha. peak near 10[.deg. C] into two peaks of .betha.$\_$1/(10.deg. C) and .betha.$\_$2/(20.deg. C) according to increasement of forming field, and the separated hardener was oxidated thermally with increasing surrounding temperatures. The expansion of the free volume need in molecular motion and the reduction of the structural packing density through thermal oxidation process increased TSC between .alpha. peak and .betha. peak and decreased T$\_$g/.

• 한국광학회지
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• 제3권1호
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• pp.43-49
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• 1992

Marx generator와 진공 다이오드, Bifilar helical wiggler, 인도자장 솔레노이드 등을 이용하여 마이크로파 영역의 자유전자 레이저를 설계 제작하였다. Bifilar helical wiggler의 자장분포를 분석하였고 공간전하의 수직성분 효ㅗ가를 고려하여 계산한 전자궤적 모의실험을 통하여 Wiggler자장이 전자빔 입사에 적합함을 확인하였다. Wiggler자장 300G, 인도자장 4.4kG, 전자빔 에너지 170keV일때 분산방정식에 의하여 계산된 출력 주파수는 약 11GHz였고 실험 결과 나타난 출력 주파수의 점위는 9.78GHz-11.7GHz로 추정되었다. 전자 속도의 축방향 퍼짐을 고려하여 이론적으로 이득을 계산하였다.

• 대한기계학회논문집B
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• 제26권2호
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• pp.227-237
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• 2002

A numerical technique for simulating the aggregation of charged particles was presented with a Brownian dynamic simulation in the free molecular regime. The Langevin equation was used for tracking each particle making up an aggregate. A periodic boundary condition was used for calculation of the aggregation process in each cell with 500 primary particles of 16 nm in diameter. We considered the thermal force and the electrostatic force for the calculation of the particle motion. The electrostatic force on a particle in the simulation cell was considered as a sum of electrostatic forces from other particles in the original cell and its replicate cells. We assumed that the electric charges accumulated on an aggregate were located on its center of mass, and aggregates were only charged with pre-charged primary particles. The morphological shape of aggregates was described in terms of the fractal dimension. In the simulation, the fractal dimension for the uncharged aggregate was D$\_$f/ = 1.761. The fractal dimension changed slightly for the various amounts of bipolar charge. However, in case of unipolar charge, the fractal dimension decreased from 1.641 to 1.537 with the increase of the average number of charges on the particles from 0.2 to 0.3 in initial states. In the bipolar charge state, the average sizes of aggregates were larger than that of the uncharged state in the early and middle stages of aggregation process, but were almost the same as the case of the uncharged state in the final stage. On the other hand, in the unipolar charge state, the average size of aggregates and the dispersion of particle volume decreased with the increasing of the charge quantities.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.605-611
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• 2001

A numerical technique for simulating the aggregation of charged particles was presented with a Brownian dynamic simulation in the free molecular regime. The Langevin equation was used for tracking each particle making up an aggregate. A periodic boundary condition was used for calculation of the aggregation process in each cell with 500 primary particles of 16 nm in diameter. We considered the thermal force and the electrostatic force for the calculation of the particle motion. The morphological shape of aggregates was described in terms of the fractal dimension. The fractal dimension for the uncharged aggregate was $D_{f}=1.761$. The fractal dimension changed slightly for the various amounts of bipolar charge. However, in case of unipolar charge, the fractal dimension decreased from 1.641 to 1.537 with the increase of the average number of charges on the particles from 0.2 to 0.3 in initial states.