• 대한금속재료학회지
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• 제49권6호
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• pp.425-439
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• 2011

A review of the development history of interatomic potential models for ionic materials was carried out paying attention to the way of future development of an interatomic potential model that can cover ionic, covalent and metallic bonding materials simultaneously. Earlier pair potential models based on fixed point charges with and without considering the electronic polarization effect were found to satisfactorily describe the fundamental physical properties of crystalline oxides (Ti oxides, $SiO_2$, for example) and their polymorphs, However, pair potential models are limited in dealing with pure elements such as Ti or Si. Another limitation of the fixed point charge model is that it cannot describe the charge variation on individual atoms depending on the local atomic environment. Those limitations lead to the development of many-body potential models(EAM or Tersoff), a charge equilibration (Qeq) model, and a combination of a many-body potential model and the Qeq model. EAM+Qeq can be applied to metal oxides, while Tersoff+Qeq can be applied to Si oxides. As a means to describe reactions between Si oxides and metallic elements, the combination of 2NN MEAM that can describe both covalent and metallic elements and the Qeq model is proposed.

• Biotechnology and Bioprocess Engineering:BBE
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• 제7권1호
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• pp.1-5
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• 2002

A fusion protein, consisting of a human epidermal growth factor (hEGF) as the recognition domain and human angiogenin as the toxin domain, can be used as a targeted therapeutic against breast cancer cells among others. The fusion protein was expressed as inclusion body in recombinant E. coli, and when the conventional, solution-phase refolding process was used the refolding yield was very low due to severe aggregation. It was probably because of the opposite electric charge at a neutral pH resulting from the vastly different pI values of each domain. The solid-phase refolding process that exploited the ionic interactions between ionic exchanger surface and the fusion protein was tried, but the adsorption yield was also very low, below $ 30\%$, regardless of the resins and pH conditions used. Therefore, to provide a higher ionic affinity toward the solid matrix, six lysine residues were tagged to the N-terminus of the hEGF domain. When heparin-Sepharose was used as the matrix, the adsorption capacity increased 2.5-3 times to about $88\%$. Besides the intrinsic affinity of angiogenin to heparin, the poly-lysine tag provided additional ionic affinity. And the subsequent refolding yield increased nearly 13-fold, from ca. $4.8\%$ in the conventional refolding of the untagged fusion protein to $63.6\%$. The process was highly reproducible. The refolded protein in the column eluate retained RNase bioactivity of angiogenin.

• 한국수소및신에너지학회논문집
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• 제33권3호
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• pp.209-218
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• 2022

Recently, research on the development of anion exchange membranes (AEMs) has received considerable attention from the scientific community around the world. Here, we fabricated a series of AEMs with branched structures with different alkyl spacers and conducted comparative evaluations. The introduction of these branched structures is an attempt to overcome the low ionic conductivity and stability problems that AEMs are currently facing. To this end, branched polymers with different spacer lengths were synthesized and properties of each membrane prepared according to the branched structure were compared. The chemical structure of the polymer was investigated by proton nuclear magnetic resonance, Fourier transform infrared, and gel permeation chromatography, and the thermal properties were investigated using thermogravimetric analysis. The branched anion exchange membrane with (CH₂)₃ and (CH₂)₆ spacers exhibited ionic conductivities of 8.9 mS cm^-1 and 22 mS cm^-1 at 90℃, respectively. This means that the length of the spacer affects the ionic conductivity. Therefore, this study showing the effect of the spacer length on the ionic conductivity of the membrane in the polymer structure constituting the ion exchange membrane is judged to be very useful for future application studies of AEM fuel cells.

• 한국고분자학회지:고분자과학과기술
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• 제24권2호
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• pp.177-182
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• 2013

• Korean Membrane Journal
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• 제9권1호
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• pp.1-11
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• 2007

To prepare chemically stable asymmetric microporous membranes with a hydrophilic surface, which would be expected to have better antifouling properties, poly(vinylidene fluoride) (PVDF) blend membranes were prepared by the phase inversion process. PVDF mixture solutions in N-methylpyrrolidone (NMP) blended with several polar potential ionic polymers such as polyacrylonitrile (PAN), poly(methylmethacrylate) (PMMA) and poly(N-isopropylacrylamide) (NIPAM) were used for the formation of the PVDF blend membranes. They were then characterized with several analytical methods such as FESEM, FTIR, contact angle measurement, pore size distribution and permeability measurement. Regardless of different polar polymers blended, they all showed a finger-like structure with more hydrophilic surface than the pristine PVDF membrane. For all the PVDF blend membrane, due to the polar potential ionic polymers used, the flux of those was improved. Especially the PVDF blend membrane with NIPAM showed the highest flux among the membranes prepared. Also antifouling property of the PVDF membrane was improved by the use of the polar polymers.

• Bulletin of the Korean Chemical Society
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• 제31권11호
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• pp.3411-3414
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• 2010

• 천문학회보
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• 제38권1호
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• pp.58.1-58.1
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• 2013

We present $10{\mu}m-35{\mu}m$ Spitzer spectra of the interstellar medium in the Central Molecular Zone (CMZ), the central 210 pc ${\times}$ 60 pc of the Galactic center (GC). We present maps of the CMZ in ionic and $H_2$ emission, covering a more extensive area than earlier spectroscopic surveys in this region. The radial velocities and intensities of ionic lines and $H_2$ suggest that most of the $H_2$ 0-0 S(0) emission comes from gas along the line-of-sight, as found by previous work. We compare diagnostic line ratios measured in the Spitzer Infrared Nearby Galaxies Survey (SINGS) to our data. Previous work shows that forbidden line ratios can distinguish star-forming galaxies from LINERs and AGNs. Our GC line ratios agree with star-forming galaxies and not with LINERs or AGNs.

• 공업화학
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• 제16권4호
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• pp.527-532
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• 2005

이온성고분자-금속복합체(Ionic Polymer Metal Composites, IPMC)는 전기활성 고분자이며, 낮은 구동전압에서도 큰 변위를 나타내는 유연한 스마트 소재(soft smart material)이다. 이온성고분자-금속복합체의 표면전극 제조는 일반적으로 화학적 환원방법(무전해 전기도금)에 의해 제조되고 있지만, 이러한 방법에서는 그 재료가 다공성 고분자 막으로 표면이 균일한 전극을 제조하기에 어려움이 있다. 본 연구에서는 전극의 표면 저항을 감소시켜 응답속도를 증가시킴과 동시에 낮은 전압에서 큰 변위를 낼 수 있는 IPMC 제조방법을 고안하여 수행하였다. 화학적 환원방법으로 이온고분자-금속 복합체를 형성시킨 후, 이온빔보조증착법(Ion Beam Assisted Deposition)으로 균질한 표면 전극 층을 형성시켜 화학적 특성을 개선하여 전기적 자극에 의한 구동반응 속도를 향상시킬 수 있는 구동체 제조방법을 제안하였다.

• 한국잡초학회지
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• 제30권3호
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• pp.233-242
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• 2010

본 연구에서는 1-alkyl-3-methylimidazolium chloride계 이온성 액체를 가지고 수생태계에서의 유해조류 방제제로서의 사용 가능성 및 활용시 예상되는 문제점 등을 알아보기 위하여 5종의 녹조류, 4종의 남조류, 1종의 규조류를 대상으로 이들의 생육에 미치는 이온성 액체의 선택적 영향을 검토해 보고자 실시하였다. 이온성 액체의 alkyl group 탄소수에 따라 활성이 달리 나타났는바, butyl < octy l< dodecyl 순으로 탄소수 길이가 길수록 살조활성이 증가되는 경향이었다. 공시된 조류종 전체를 비교해 보았을 때, Stephanodiscus hantzschii f. tenuis, Oscillatoria tenuis, Spirulina pratensis가 1-dodecyl-3-methylimidazolium chloride (MAIC12)에 민감한 생육억제 반응을 보이며 그 다음은 Microcystis aeruginosa이었고, 나머지 조류 종은 상대적으로 덜 민감하였다. 선택성 정도는 80% 억제농도를 기준하여 검토해 보았을 때 대략 10-20배 정도였다. 한편 자연상태와 비슷한 조건(온실조건의 퇴적물 존재)에서 이온성 액체가 수중에 처리되었을 때의 살조활성 지속성을 조사하였다. 그 결과 MAIC8 $1.0{\mu}g\;mL^{-1}$ 농도에서는 처리후 6일까지 생장이 중지되었다가 9일째에는 조류가 약간 발생하였으며 이후 생장이 뚜렷하게 증가하는 경향으로서 20일째에는 엽록소 함량이 $264.4{\mu}g\;L^{-1}$로서 무처리 대비 58.2% 생장을 나타냈다. MAIC12의 경우는 MAIC8 보다 약 5배 높은 활성을 나타내는 경향으로서 $0.2{\mu}g\;mL^{-1}$ 농도로 처리했을 때 처리후 6일까지 조류발생이 전혀 없었다가 9일째에는 조류가 약간 번식하였으며 이후 생장이 비교적 뚜렷하게 증가하여 20일째에는 엽록소 함량이 $251.2{\mu}g\;L^{-1}$로서 무처리 대비 55.2% 생장을 나타냈다. 결론적으로 1-alkyl-3-methylimidazolium chloride계 이온성 액체는 살조활성 특성 측면에서 볼 때는 우수한 효능, 선택적 살조활성 및 효과 지속성으로 인해 수생태계에서의 유해조류 선택적 방제제로서 사용될 수 있을 것 같았으나, 화합물 분해 측면에서 볼 때는 상대적으로 난분해성 특성을 가져 환경친화적으로 사용하기에는 개선될 필요성이 있는 것 같았다.

• 한국세라믹학회지
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• 제46권1호
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• pp.41-46
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• 2009

The rheological properties of highly concentrated Ag nano sol depending on particle size were studied. The Ag nano sol was prepared by reducing the Ag ion in aqueous solution. The size of Ag nano particle was controlled by two steps of nucleation and growth, and the thickness of adsorption layer was varied by molecular weight of polyelectrolytes. The polyelectrolytes acted as not only ionic complex agent in ionic state and but also dispersant after formation of Ag nano sol. The effective volume was controlled by combination of varying the molecular weight of polyelectrolytes and the size Ag nano sol. The particle size and the viscosity of nano sol were characterized by particle size analyzer, HR-TEM and cone & plate viscometer. It was found that the 10 nm and 40 nm-sized Ag nano sols were prepared by controlling the nucleation and growth steps, respectively. Finally, we could prepare highly concentrated Ag nano sol over 50 wt%.