• Journal of Sericultural and Entomological Science
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• v.41 no.1
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• pp.41-47
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• 1999

Silk fibroin dissolved in highly concentrated calcium chloride and ethanol mixture aqueous solution turned into gel under suitable conditions. Preparation conditions and properties of gel were investigated as a function of parameters such as pH of solution, fibroin concentration, glycerol concentration and molecular weight. When pH of silk fibroin aqueous solution was near the isoelectronic point(pH 3.9~4.0), gelation occurred rapidly and strength of gel was stonger than that of pH-unadjusted due to electrostatic repulsion decrease between silk fibroin macromolecules. As concentration of silk fibroin and glycerol was higher, gelation occurred more rapid. FT Infra-red spectra of freeze-dried fibroin gel showed that gelation was derived by intermolecular anti-parallel ${\beta}$-sheet structure formation. In addition to, it was found that white-precipitate occurred instead of gelation when aqueous silk fibroin was treated by enzyme(flavouzyme), however, after flavouzyme-treated silk fibroin aqueous solution was centrifugated gelation occurred instantly. The results of differential scanning thermal analysis and infra-red spectroscopy showed that thermal stability and crystallinity of enzyme-hydrolyzed fibroin are superior to those of unhydrolyzed fibroin.

• BMB Reports
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• v.31 no.6
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• pp.595-599
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• 1998

To investigate conformational information of a low oxygen affinity recombinant hemoglobin (rHb) containing $96Val{\rightarrow}Trp$ mutation at the ${\alpha}96$ position, we ave produced rHb (${\alpha}96Val{\rightarrow}Phe$) and rHb (${\alpha}96Val{\rightarrow}Tyr$), using the Escherichia coli expression system and site-directed mutagenesis. The oxygen affinity of rHb (${\alpha}96Val{\rightarrow}Phe$) is similar to that of human normal adult hemoglobin (Hb A). However, the oxygen affinity of rHb (${\alpha}96Val{\rightarrow}Tyr$) showed much lower oxygen affinity than Hb A which is similar to that of rHb (${\alpha}96Val{\rightarrow}Tyr$), providing an opportunity as a potential candidate for a hemoglobin-based blood substitute. Both rHb (${\alpha}96Val{\rightarrow}Phe$) and rHb (${\alpha}96Val{\rightarrow}Tyr)$ showed high cooperativity in oxygen binding. IH-NMR spectroscopy shows that both rHb (${\alpha}96Val{\rightarrow}Phe$) and rHb (${\alpha}96Val{\rightarrow}Tyr$) have very similar tertiary structure around the heme pockets and uaternary structure in the ${\alpha}_1/{\beta}_2$ subunit interface ompared to Hb A. The low oxygen affinity of rHb (${\alpha}96Val{\rightarrow}Tyr$) has been suggested to be due to a hydrogen bond caused by an extra hydroxyl group not present in rHb (${\alpha}96Val{\rightarrow}Phe$). However, investigation of the carbonmonoxy form of rHb (${\alpha}96Val{\rightarrow}Phe$) and (${\alpha}96Val{\rightarrow}Try$) in the presence of inositol hexaphosphate at low temperature suggests that low oxygen affinity of (${\alpha}96Val{\rightarrow}Try$) may arise from a mechanism different to that of rHb (${\alpha}96Val{\rightarrow}Trp$).

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.324-325
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• 2014

Quantum wells infrared photodetectors (QWIPs) have been used to detect infrared radiations through the principle based on the localized stated in quantum wells (QWs) [1]. The mature III-V compound semiconductor technology used to fabricate these devices results in much lower costs, larger array sizes, higher pixel operability, and better uniformity than those achievable with competing technologies such as HgCdTe. Especially, GaAs/AlGaAs QWIPs have been extensively used for large focal plane arrays (FPAs) of infrared imaging system. However, the research efforts for increasing sensitivity and operating temperature of the QWIPs still have pursued. The modification of heterostructures [2] and the various fabrications for preventing polarization selection rule [3] were suggested. In order to enhance optical performances of the QWIPs, double barrier quantum well (DBQW) structures will be introduced as the absorption layers for the suggested QWIPs. The DBWQ structure is an adequate solution for photodetectors working in the mid-wavelength infrared (MWIR) region and broadens the responsivity spectrum [4]. In this study, InGaAs/GaAs/AlGaAs double barrier quantum well infrared photodetectors (DB-QWIPs) are successfully fabricated and characterized. The heterostructures of the InGaAs/GaAs/AlGaAs DB-QWIPs are grown by molecular beam epitaxy (MBE) system. Photoluminescence (PL) spectroscopy is used to examine the heterostructures of the InGaAs/GaAs/AlGaAs DB-QWIP. The mesa-type DB-QWIPs (Area : $2mm{\times}2mm$) are fabricated by conventional optical lithography and wet etching process and Ni/Ge/Au ohmic contacts were evaporated onto the top and bottom layers. The dark current are measured at different temperatures and the temperature and applied bias dependence of the intersubband photocurrents are studied by using Fourier transform infrared spectrometer (FTIR) system equipped with cryostat. The photovoltaic behavior of the DB-QWIPs can be observed up to 120 K due to the generated built-in electric field caused from the asymmetric heterostructures of the DB-QWIPs. The fabricated DB-QWIPs exhibit spectral photoresponses at wavelengths range from 3 to $7{\mu}m$. Grating structure formed on the window surface of the DB-QWIP will induce the enhancement of optical responses.

• Polymer(Korea)
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• v.29 no.4
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• pp.363-367
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• 2005

The effects of organic solvent on the charge transport behavior of poly (3,4-ethylenedioxythioph one)/p-toluene-sulfonate(PEDOT-OTs) are investigated. The use of different organic solvents during the oxidative chemical polymerization of 3,4-ethylenedioxythiophene (EDOT) with Iron(III) -tosylate can greatly vary the DC conductivity of PEDOT-OTs along with molecular structure and doping concentration. For example, PEDOT-OTs prepared from methanol shows the conductivity of 19.5 S/cm, which is an increase by a factor of $10^8$ compared to PEDOT-OTa prepared from acetone. From the X-ray diffraction (XRD) experiments, it was found that PEDOT-OTs with ketone is amorphous state, while PEDOT-OTs with alcoholic solvent shows the better defined crystalline structure in which the charge transport along and between the PEDOT chains are promoted. Chemical analysis employing X-ray photoelectron spectroscopy (XPS) revealed that the doping concentration of PEDOT-OTs with alcoholic solvent is much higher than that of PEDOT-OTs with ketones. It is proposed that the interactions between the organic solvent and doping anion can cause the variation in doping concentration and, therefore, result in the PEDOT-OTs of different conductivities and chain structures.

• Applied Chemistry for Engineering
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• v.21 no.5
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• pp.542-547
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• 2010

n-Paraffin and saturated fatty acid methyl esters in the diesel and bio-diesel fuel crystallize at low temperature. Many articles have addressed various solutions for the low temperature crystallization problem and one of them is the use of methacrylate copolymers. In this work, we synthesized a series of copolymers in the reaction condition of 70 : 30 molar ratio of lauryl methacrylate (LMA) (or stearyl methacrylate (SMA)) and alkyl methacrylates. The structures of the copolymers were characterized by $^1H$-NMR and FT-IR spectroscopy, and the molecular weight of copolymers were obtained from Gel Permeation Chromatography (GPC) method. The concentrations of additives were 500~1000 ppm and 1000~10000 ppm in diesel fuels and bio-diesel fuel (BD5 and BD20), respectively. The addition of copolymers changes the many properties of fuel such as the pour point (PP), cloud point (CP) and cold filtering plugging point (CFPP). For example, the low temperature properties of the copolymers containing SMA ($PSMAmR_2n$) were excellently improved about 15, 7, and $10^{\circ}C$ for PP, CP and CFPP, respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.306-307
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• 2011

Franz Keldysh Oscillation (FKO)은 p-n 접합 구조의 공핍층(depletion zone)에서 전기장(electric field)에 의해 발생되며, Photoreflectance (PR) spectroscopy를 통하여 관측된다. InAs/GaAs 양자점 태양전지(Quantum Dot Solar Cells, QDSCs)에서 PR 신호에 대한 Fast Fourier Transform (FFT)을 통하여 FKO 주파수들을 관측할 수 있고, 각각의 FKO 주파수들은 태양전지 구조에 대응하는 표면 및 내부전기장(internal electric field) 들로 분류할 수 있다. InAs/GaAs 양자점 태양전지에서 AlGaAs potential barrier의 두께에 따른 내부전기장의 변화를 조사하기 위해, GaAs-matrix에 8주기의 InAs 양자점 층이 삽입된 태양전지를 molecular beam epitaxy (MBE) 방법으로 성장하였다. 양자점의 크기는 2.0 monolayer (ML)이며, 각 양자점 층은 1.6 nm에서 6.0 nm의 AlGaAs potential barrier들로 분리되어 있다. 또한 양자점 층의 위치에 따라 내부전기장 변화를 조사하기 위해, p-i-n 구조에서 양자점 층이 공핍층 내에 위치한 경우와 p+-n-n+ 구조에서 양자점 층이 공핍 층으로부터 멀리 떨어진 n-base 영역에 삽입하여 실험결과를 비교분석하였다. PR 실험결과로부터, p-i-n 구조에서 InAs 양자점 태양전지의 내부전기장 변화는 potential barrier 두께에 따라 다소 복잡한 변화를 보였으며, 이는 양자점 층이 공핍층 내에 위치함으로써 격자 불일치(lattice mismatch)로 발생된 응력(strain)의 영향으로 설명할 수 있다. 이러한 결과들을 각각의 태양전지 구조에서 표면 및 내부전기장에 대해 계산된 값들에 근거하여, p+-n-n+ 구조에서 양자점 층이 공핍 층으로부터 멀리 떨어진 영역에 삽입된 경우의 결과와 비교해 보면 내부전기장의 변화는 더욱 분명해진다. 즉, 양자점 층의 potential barrier의 두께를 조절하거나, 양자점 층의 위치를 변화시킴으로써 양자점 태양전지의 내부전기장을 조작할 수 있으며, 이는 PR 실험을 통해 FKO를 관측함으로써 확인할 수 있다.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.06a
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• pp.129-136
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• 2005

There should not be ion exchange resin particles in S/G sludge. The suspicious spherical resin particles observed in S/G sludge sample were characterized for particle size distribution under optical microscope using the micro-technique, for element analysis by the electron probe micro analysis (EPMA), and for molecular identification by the IR spectroscopy The particle sizes are distributed from 1 to 200 ${\mu}m$ for the sludge, while 40 to 500 ${\mu}m$ for the spherical resin particles. The results of the elemental analysis showed different major impurities: Si, Al, Mn, Cr, Ni, Zn and Ti for the sludge particles, while Si, Cu, Zn for the spherical resin particles. However, both particles contain Fe as a matrix of hematite ($Fe_{3}O_4$). IR spectrum of the spherical particles was quite different from that of ion exchange resins used in S/G system. These results indicate that the spherical particles are not related to ion exchange resin particles and formed by the process of the sludge formation.

• Corrosion Science and Technology
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• v.7 no.1
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• pp.50-60
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• 2008

The majority of the described experimental results deal with relatively pure aluminium. Variations were made in the pretreatment of the aluminum substrates and an investigation was performed on the resulting changes in oxide layer composition and chemistry. Subsequently, the bonding behavior of the surfaces was investigated by using model adhesion molecules. These molecules were chosen to represent the bonding functionality of an organic polymer. They were applied onto the pretreated surfaces as a monolayer and the bonding behavior was studied using infrared reflection absorption spectroscopy. A direct and clear relation was found between the hydroxyl fraction on the oxide surfaces and the amount of molecules that subsequently bonded to the surface. Moreover, it was found that most bonds between the oxide surface and organic functional groups are not stable in the presence of water. The best performance was obtained using molecules, which are capable of chemisorption with the oxide surface. Finally, it was found that freshly prepared relatively pure aluminum substrates, which are left in air, rapidly lose their bonding capacity towards organic functional groups. This can be attributed to the adsorption of contamination and water to the oxide surface. In addition the adhesion of a typical epoxy-coated aluminum system was investigated during exposure to water at different temperatures. The coating was found to quite rapidly lose its adhesion upon exposure to water. This rapid loss of adhesion corresponds well with the data where it was demonstrated that the studied epoxy coating only bonds through physisorptive hydrogen bonding, these bonds not being stable in the presence of water. After the initial loss the adhesion of the coating was however found to recover again and even exceeded the adhesion prior to exposure. The improvement could be ascribed to the growth of a thin oxyhydroxide layer on the aluminum substrate, which forms a new, water-stable and stronger bond with the epoxy coating. Two routes for improvement of adhesion are finally decribed including an interphasial polymeric thin layer and a treatment in boiling water of the substrate before coating takes place. The adhesion properties were finely also studied as a function of the Mg content of the alloys. It was shown that an enrichment of Mg in the oxide could take place when Mg containing alloys are heat-treated. It is expected that for these alloys the (hydr)oxide fraction also depends on the pre-treatment and on the distribution of magnesium as compared to the aluminium hydroxides, with a direct impact on adhesive properties.

• Food Science of Animal Resources
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• v.36 no.5
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• pp.665-670
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• 2016

The objectives of this study were conducted to characterize pepsin-soluble collagen (PSC) extracted from bones (PSC-B), skins (PSC-S), and tendons (PSC-T) of duck feet and to determine their thermal and structural properties, for better practical application of each part of duck feet as a novel source for collagen. PSC was extracted from each part of duck feet by using 0.5 M acetic acid containing 5% (w/w) pepsin. Electrophoretic patterns showed that the ratio between α₁ and α₂ chains, which are subunit polypeptides forming collagen triple helix, was approximately 1:1 in all PSCs of duck feet. PSC-B had slightly higher molecular weights for α₁ and α₂ chains than PSC-S and PSC-T. From the results of differential scanning calorimetry (DSC), higher onset (beginning point of melting) and peak temperatures (maximum point of curve) were found at PSC-B compared to PSC-S and PSC-T (p<0.05). Fourier transform infrared spectroscopy (FT-IR) presented that PSC-S and PSC-T had similar intermolecular structures and chemical bonds, whereas PSC-B exhibited slight difference in amide A region. Irregular dense sheet-like films linked by random-coiled filaments were observed similarly. Our findings indicate that PSCs of duck feet might be characterized similarly as a mixture of collagen type I and II and suggest that duck feet could be used for collagen extraction without deboning and/or separation processes.

• Journal of Adhesion and Interface
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• v.11 no.2
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• pp.41-49
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• 2010

Furan-containing epoxide monomers (8, 9) were designed and synthesized as carbon-neutral, environment-friendly adhesion material. Bicyclic skeleton were constructed using the Diels-Alder reaction of furan and methyl acrylate, both readily accessible starting material from a biomass via bio-refinery process. After reduction of ester functionality, resulting hydroxyl moieties were coupled to epichlorohydrin to provide the epoxy-functionalized furanic monomers (8, 9). The structure of new furanic monomers was confirmed by $^1H$ and $^{13}C$ NMR spectroscopy. As UV-curable monomers, basic properties such as UV curing time and the extent of UV curing were evaluated by photo DSC. Photo-curing shrinkages were measured by linear variable differential transformer transducer (LVDT) and the effect of molecular structure on shrinkage was considered. In addition, new synthetic compounds showed the shear strength over 3 MPa when they were photo-cured between polycarbonate plates, which indicates these compounds are feasible to use as photo-curable adhesive materials.