• Bulletin of the Korean Chemical Society
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• v.27 no.7
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• pp.981-985
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• 2006

Novel copolymers consisting of poly(2-hydroxyethyl aspartamide-co-N,N'-dimethyl-1,3-propane aspartamide) (PHEA-DPA) were prepared from polysuccinimide (PSI), which is the thermal polycondensation product of aspartic acid, via a ring-opening reaction with N,N'-dimethyl-1,3-propane diamine (DPA) and ethanolamine. The prepared water-soluble copolymer was then crosslinked by reacting it with hexamethylene diisocyanate to provide the corresponding gel. The swelling behavior and morphology of the crosslinked hydrogels were investigated. The degree of swelling decreased with increasing crosslinking reagent due to the higher crosslinking density. It was also confirmed that the swelling property is affected by pH. At low pH (< pH 4), swelling is increased due to the ionization of DPA with a tertiary amine moiety. In addition, a reversible swelling and de-swelling behavior was demonstrated by adjusting the pH of the solution. The prepared hydrogels showed a well-interconnected microporous structure with regular 5-20 $\mu$m sized pores.

• Bulletin of the Korean Chemical Society
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• v.31 no.2
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• pp.275-280
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• 2010

Actinobacillus actinomycetemcomitans is a gram-negative, nonmotile coccobacillus bacterium that is associated with several human diseases, including endocarditis, meningitis, osteomyelitis, subcutaneous abscesses and periodontal diseases. A full-length Omp1-like protein gene from A. actinomycetemcomitans was cloned into a pQE30 vector and overexpressed in Escherichia coli BL21(DE3) cells. The protein revealed sequence homologies to Seventeen kilodalton proteins (Skp) from Pasteurella multocida and E. coli that have been characterized as periplasmic chaperones. This soluble Omp1-like protein was successfully purified to homogeneity for further folding and functional studies. The purity, identity, and conformation of the protein were determined using sodium dodecyl sulfate polyacrylamide gel electrophoresis, matrix-assisted laser desorption ionization mass spectrometry, circular dichroism, fluorescence spectroscopic, and differential scanning calorimetric studies. We showed that the protein formed an oligomer larger than a tetramer. We found, further, that it is comprised of mostly $\alpha$-helices and boasts high thermal stability.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.4
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• pp.297-306
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• 2014

Recently nano-materials are gaining more importance in the construction industry due to its enhanced energy efficiency, durability, economy, and sustainability. Nano-silica addition to cement based materials can control the degradation of the fundamental calcium-silicate-hydrate reaction of concrete caused by calcium leaching in water as well as block water penetration and therefore lead to improvements in durability. In this paper, the influence of synthesized nano silica from locally available rice husk on the mechanical properties and corrosion resistant properties of OPC (Ordinary Portland Cement) has been studied by conducting various experimental investigations. Micro structural properties have been assessed by conducting Scanning Electron Microscopy, Thermo gravimetry and Differential Thermal Analysis, X-Ray Diffraction analysis, and FTIR studies. The experimental results revealed that NS reacted with calcium hydroxide crystals in the cement paste and produces Calcium Silicate Hydrate gel which enhanced the strength and acts as a filler which filled the nano pores present in concrete. Hence the strength and corrosion resistant properties were enhanced than the control.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.37.1-37.1
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• 2009

몰리브덴 금속박막(Metal Mo)은 우수한 전기전도도로 인해 $CuInSe_2$로 대표되는 I-III-$VI_2$족 화합물 반도체 박막태양전지에서 후면전극으로 널리 이용되고 있는 재료로서 일반적인 증착방법으로CVD, PVD, Thermal evaporation, Sol-gel 등이 있으며, 이중에서 Sputtering에 의한 증착법이 주로 사용되고 있다. 이에 본 연구에서는 $MoO_3$분말의 수소 환원 과정 중에 발생하는 기상인 $MoO_3(OH)_2$ 기상의 화학증기수송(CVT)를 이용하여 $MoO_x$ 박막을 증착하고 다시 수소분위기에서 수소 환원하는 증착법을 통해 균일하고 부착성이우수한 Mo 박막을 제조 하였다. $550^{\circ}C$, 60min의 유지시간에서 약 900nm의 균일한 $MoO_x$ 박막을 증착하였으며, $650^{\circ}C$, 15min 의 환원조건에서 모두 금속 몰리브덴 박막으로 상변화 함을 XRD와 SEM을 통해 확인하였다. 본 연구에서 사용된 화학증기수송에 의한 박막 증착은 기존의 공정에 비해 매우 저렴하며, 반응중에 유해하지 않은 부산물로 인해 환경 친화적이며 또한 대형화가 가능한 공정으로 많은 응용이 기대된다.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.14-14
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• 2009

High frequency electromagnetic(EM) waves are increasingly being applied in industries because of saturationat lower frequency bands as a result of huge demand. However, electromagneticinterference (EMI) has become a serious problem, and as a result, highfrequency EM absorbers are now being extensively studied. Also, recentdevelopments in absorber technology have focused on producing absorbers thatare thin, flexible, and strong. Hence, one-dimension ferrous nano-materials area potential research field, because of their interesting electronic andmagnetic properties. Commercially, EM wave absorbing products are made ofcomposites, which blend the insulating polymer with magnetic fillers. Inparticular, the shape of the magnetic fillers, such flaky, acicular, or fibrousmagnetic metal particles, rather than spherical, is essential for synthesizingthin and lightweight EM wave absorbers with higher permeability. High aspectratio materials exhibit a higher permeability value and therefore betterabsorption of the EM wave, because of electromagnetic anisotropy. Nanowires areusually fabricated by drawing, template synthesis, phase separation, selfassembly, and electrospinning with a thermal treatment and reduction process.Producing nanowires by the electrospinning method involves a conventionalsol-gel process that is simple, unique, and cost-effective. In thispresentation, Magnetic nanowire and dielectric materials coated magneticnanowire with a high aspect ratio were successfully synthesized by theelectrospinning process with heat treatment and reduction. In addition toestimating the EM wave absorption ability of the synthesized magnetic anddielectric materials coated magnetic nanowire with a network analyzer, weinvestigated the possibility of using these nanowires as high-frequency EM waveabsorbers. Furthermore, a wide variety of topics will be discussed such as thetransparent conducting nanowire and semiconducting nanowire/tube with theelectrospinning process.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.422-422
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• 2009

Photocurable inorganic-organic hybrid materials were prepared from colloidal-silica nanoparticles synthesized through the solgel process and using acryl resin. The synthesized colloidal-silica nanoparticles had uniform diameters of around 20 nm, and they were organically modified, using methyl and methacryl functional silanes, for efficient hybridization with acryl resin. The organically modified and stabilized colloidal-silica nanoparticles could be homogeneously hybridized with aeryl resin without phase separation. The successfully fabricated hybrid materials exhibit efficient photocurability and simple film formation due to the photopolymerization of the organically modified colloidal-silica nanoparticles and acryl resin upon UV exposure. The fabricated hybrid films exhibit an excellent optical transmission of above 90% in the visible region as well as an enhanced surface smoothness of around 1 nm RMS roughness. In addition, the hybrid films exhibit improved thermal and mechanical characteristics, much better than those of acryl resin. More importantly, these photocurable hybrid materials fabricated through the synergistic combination of colloidal-silica nanoparticles with acryl resin are candidates for optical and electrical applications.

• Applied Biological Chemistry
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• v.21 no.2
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• pp.103-108
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• 1978

Acid-stable ${\alpha}-amylase$ was partially purified from Paecilomyces subglobosum by Sephadex G-150 gel filtration. About 7.7-fold purification was obtained and the partially purified preparation has 5.0 U of ${\alpha}-amylase$ activity per mg of protein. Using this partially purified ${\alpha}-amylase$, general properties were studied and it showed the maximal activities at the conditions of pH 4.0 and $38^{\circ}C$. High stability of the acid-stable ${\alpha}-amylase$ in acidic condition was observed, whereas thermal stability was similar to the conventional ${\alpha}-amylase$.

• Preventive Nutrition and Food Science
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• v.2 no.4
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• pp.296-300
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• 1997

Glucose syrup and lactose, mixed with citric acid as a polymerizing catalyst, was processed using twin screw extruder, in which 40 of L/D(length/diameter) ratio was designed to provide sufficient retention in extruder for polymerization of sugars. The polymerization yields of glucose syrup were 36.90%, 55.44% and 77.10% at 160, 180 and 20$0^{\circ}C$, respectively, while those of lactose were 26.45%, 38.16% and 45.86% at the same temperatures. Gel permeation chromatography exhibited that the higher molecular weight fractions were increased with extrusion temperature, which also led to increasing hydrodynamic intrinsic viscosity. Both uco-oligosaccharides and lacto-oligosaccharides produced by extrusion of glucose syrup and lactose were stable for thermal treatments over a wide range of pH3.0~11.0. In addition, $\alpha$-amylase and amyloglucosidase treatment of gluco-oligosaccharides did not affect the solution viscosity, indicating the random linkage rather than $\alpha$-1, 4 linkages of glucose and thus the potential applications as a dietary fiber. In this research it was clearly observed that twin screw extrusion can be successfully utilized to produce gluco-oligosaccharides and lacto-oligosaccharides rapidly and continuously in conjunction with selective control of polymerized composition.

• Korean Journal Plant Pathology
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• v.11 no.4
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• pp.361-366
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• 1995

A virus was isolated from petunia (Petunia hybrida Vilm.) plants showing chlorotic ring spots on the leaves and color breaking on the flowers, and was identified as petunia asteroid mosaic virus (PAMV). Identification of the PAMV was established by host range test, electron microscopy, serological reaction, and physical properties of the virus. In the host range test, Nicotiana glutinosa, N. rustica, N. clevelandii, P. hybrida, Gomphrena globosa, and Chenopodium amaranticolor were systemically infected with the virus. The virus produced local lesions on inoculated leaves of N. tabacum‘Samsun’, N. tabacum‘Xanthi nc’, Datura stramonium, Vigna unguiculata‘White eye’, C. quinoa, Capsicum annuum, Vicia faba, and Lycopersicon esculentum‘Rutgers’. However, Cucurbita sativus and C. moschata did not show any symptoms. PAMV particles were isometric with 30 nm in diameter. The crude sap from G. globosa infected with the virus reacted positively with antiserum to tomato bushy stunt virus (TBSV) in agar gel double diffusion test. Thermal inactivation point of the virus was 8$0^{\circ}C$ and the virus retained its infectivity at the dilution of 10-4. Longevity in vitro of the virus was estimated longer than 35 days.

• The Korean Journal of Mycology
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• v.19 no.3
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• pp.214-219
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• 1991

Adenosine-5'-triphosphatase$(F_1-ATPase)$ in the Lentinus edodes was fractionated by ammonium aulfate 30% saturation and purified by Sephadex G-200 gel filtration in three times. Three kinds of protein fractions of $F_1-ATPase$ were isolated from this mushroom, and fraction I and ll showed its activity for the substrate, adenosine-5'-triphosphate. Its optimum pH and temperature were found to be pH 7.6 and $58^{\circ}C$, and its thermal stability was stabled for 30 min. at $20-30^{\circ}C$. The Km value of this enzyme was 1.81 mM.