• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.1-2
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• 2003

While aromatic polyimides and polyamides have found widespread use as high performance polymers, the present work addressed the need for organosoluble materials through the use of a hyperbranching scheme. The $AB_2$ monomers were prepared. The $AB_2$ monomers were then polymerized via aromatic fluoride-displacement and Yamazaki reactions to afford the corresponding hydroxyl-terminated hyperbranched polyimides (HT-PAEKI) and amine-terminated hyperbranched polyamides, respectively. HT-FAEKI was then functionalized with allyl and propargyl bromides as well as epichlorohydrin to afford allyl-terminated AT-PAEKI, propargyl-terminated PT-PAEKI, and epoxy (glycidyl)-terminated ET-PAEKI, in that order. All hyperbranched poly(ether-ketone-imide)s were soluble in common organic solvents. AT-PAEKI was blended with a bisphenol-A-based bismaleimide (BFA-BMI) in various weight ratios. Thermal, rheological, and mechanical properties of these blend systems were evaluated. Two characteristic hyperbranched polyamides, which the one has para-electron donating groups to the surface amine groups and the other has para-electron withdrawing groups to the surface amine groups, were selected to compare BMI curing behaviors. The electron rich polymer displayed ordinary Michael addition type exothermic reaction, while electron deficient polymer did display unusual curing behaviors. Based on analytical data, the later system provided the strong evidences to support room temperature curing of BMI by reactive intermediates instead of reactive primary amine groups on the macromolecule surface.

• Journal of the Korean Chemical Society
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• v.56 no.4
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• pp.473-477
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• 2012

The novel chitosan-based thermosensitive hydrogels were prepared as control-releasing drug carriers. N-carboxyethyl chitosan (ACS) was synthesized by microwave heating for 1 h through Michael addition of CS to acrylic acid in a grafting yield of 52.97%, which was proved to be a faster and more efficient way than ordinary methods. 5-Fu was modified with formaldehyde to synthesize N,N'-Bis(hydroxymethyl)-5-fluorouracil (5-Fu-OH). Then an esterification was performed using ACS and 5-Fu-OH to give 5-Fu-ACS. The new thermosensitive hydrogels were prepared by adding sodium glycerophosphate to the solution of compounds under a certain constant temperature. Simultaneously, the hydrogels' swelling rate, in vitro drug release rate and thermosensitive were studied, and found that the 5-Fu-ACS composite hydrogel had more excellent releasing effect, higher drug loading and better thermosensitive.

• Transactions of Materials Processing
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• v.13 no.1
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• pp.15-20
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• 2004

In order to evaluate spring-back behavior in automotive sheet forming processes, a panel shape idealized as a double S-rail has been investigated. After spring-back has been predicted for double S-rails using the finite element analysis, results has been compared with experimental measurements for three automotive sheets. To account for hardening behavior such as the Bauschinger and transient effects in addition to anisotropic behavior, the combined isotropic-kinematic hardening law based on the Chaboche type model and a recently developed non-quadratic anisotropic yield function have been utilized, respectively.

• International Journal of Concrete Structures and Materials
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• v.8 no.4
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• pp.301-307
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• 2014

Rice husk ash (RHA) is classified as a highly reactive pozzolan. It has a very high silica content similar to that of silica fume (SF). Using less-expensive and locally available RHA as a mineral admixture in concrete brings ample benefits to the costs, the technical properties of concrete as well as to the environment. An experimental study of the effect of RHA blending on workability, strength and durability of high performance fine-grained concrete (HPFGC) is presented. The results show that the addition of RHA to HPFGC improved significantly compressive strength, splitting tensile strength and chloride penetration resistance. Interestingly, the ratio of compressive strength to splitting tensile strength of HPFGC was lower than that of ordinary concrete, especially for the concrete made with 20 % RHA. Compressive strength and splitting tensile strength of HPFGC containing RHA was similar and slightly higher, respectively, than for HPFGC containing SF. Chloride penetration resistance of HPFGC containing 10-15 % RHA was comparable with that of HPFGC containing 10 % SF.

• Journal of Microbiology and Biotechnology
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• v.14 no.1
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• pp.74-80
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• 2004

Aspergillus fumigatus is one of the most common fungi in the human environment, both in-doors and out-doors. It is the main causative agent of invasive aspergillosis, a life-threatening mycosis among immunocompromised patients. The genome has been sequenced by an international consortium, including the Wellcome Trust Sanger Institute (U.K.) and The Institute for Genomic Research (TIGR, U.S.A.), and a ten times whole genome shotgun sequence assembly has been made publicly available. In this study, we identified tricarboxylic acid (TCA) cycle enzymes of A. fumigatus by comparative analysis with four other fungal species. The open reading frames showed high amino acid sequence similarity with the other fungal citric acid enzymes and well-conserved functional domains. All genes present in Saccharomyces cerevisiae, Schizosaccharomyces pombe, Candida albicans, and Neurospora crassa were also found in A. fumigatus. In addition, we identified four A. fumigatus genes coding for enzymes in the glyoxylate shunt, which may be required for fungal virulence. The architecture of multi-gene encoded enzymes, such as isocitrate dehydrogenase, 2-ketoglutarate, succinyl-CoA synthetase, and succinate dehydrogenase was well conserved in A. fumigatus. Furthermore, our results show that genes of A. fumigatus can be detected reliably using GlimmerM.

• The Journal of Korean Society of Virology
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• v.29 no.1
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• pp.33-38
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• 1999

Retroviral vector provide a highly efficient method for gene transfer into eukaryotic cells. This vector system can be divided into two components; the retroviral vector itself and the retroviral packaging cell line. The key improvement in the design of these two components are, focused on two aspects; the reduction of helper virus production and high titer-virus. We used PA317 for retrovirus packaging cell line, for its high producibility of viral titer. To test the ability of the vectors to generate high titer-virus, we have chosen four different retroviral vectors; LN, LNSX, LNCX and LXSN. To test easily the viral titer, we have made recombinant construction with CD4 and CD8, checked their viral titer and stained their surface expression. LXSN which contain SV40 early promoter in front of neo gene showed best results in viral transient transfection assay, dot blot assay and surface expression. In addition, recombinant containing CD8 generally showed much higher viral titration and surface expression than CD4.

• Rapid Communication in Photoscience
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• v.2 no.3
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• pp.68-71
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• 2013

Acetone sensitized photoadditions of isopropanol to (5R)-5-menthyloxy-2-(5H)-furanone were investigated in two different microflow reactor systems. Setup A employed a commercially available glass reactor under a UVB-panel. Setup B utilized a FEP microcapillary wrapped tightly around a Pyrex cylinder with a single UVB fluorescent tube at its center. The reactions under flow conditions were subsequently compared to analogue reactions conducted in a batch chamber reactor. Overall, the microflow systems gave faster conversions and higher isolated yields. The flexible microcapillary setup, however, showed the best performance and promise in terms of future scale-up and reactor optimization.

• Journal of Pharmaceutical Investigation
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• v.36 no.4
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• pp.263-269
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• 2006

Deficiencies in the early ADMET(absorption, distribution, metabolism, elimination and toxicity) information on drug candidate extract a significant economic penalty on pharmaceutical firms. Microscale cell culture analogue-microscale gastrointestinal(${\mu}CCA-{\mu}GI$) device using Caco 2, L2 and HEp G2/C3A cells, which mimic metabolic process after absorption occurring in humans was used to investigate the toxicity of the model chemical, acetaminophen(AAP). The toxicity of acetaminophen determined after induction of CYP 1A1/2 in Caco 2 cells was not significant. In a coculture system, although no significant reduction in viability of HEp G2/C3A and L2 cells was found, approximately 5 fold increase in the CYP 1A1/2 activity was observed. These results appear to be related to organ-organ interaction. The oral administration of a drug requires addition of the absorption process through small intestine to the current ${\mu}CCA$ device. Therefore, a perfusion coculture system was employed for the evaluation of the absolution across the small intestine and resulting toxicity in the liver and lung. This system give comprehensive and physiologic information on oral uptake and resulting toxicity as in the body. The current ${\mu}CCA$ device can be used to demonstrate the toxic effect due to organ to organ interaction after oral administration,

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.575-579
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• 2005

A beautiful, flexible active-matrix electrophoretic display (AM-EPD) device is reported. The flexible AM-EPD device has a $40.0{\times}30.0\;mm^2$ display area, measures about 0.27 mm in thickness, weighs about 0.45 g and possesses only 20 external connections. The flexible AM-EPD device displays clear black-and-white images with 5 gray-scales on $160{\times}120$ pixels. The display is free from residual image problems, because we use an area-gray-scale method on $320{\times}240$ EPD elements, each of which is driven with binary signals. Each pixel consists of 4 EPD elements. In addition, since the response time of the electrophoretic material is as long as approximately 400 ms and since the display possesses a large number of EPD elements, we have developed a special driving method suitable for changing EPD images comfortably. A complete image is formed on the AM-EPD device, consisting of a reset frame and several, typically 6, image frames.

• Macromolecular Research
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• v.12 no.5
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• pp.534-539
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• 2004

Two biopolymers, silk fibroin (SF) and chitosan, were conjugated by tyrosinase (EC 1.14.18.1), a polyphenolic oxidase, to improve their physicochemical properties, such as their thermal properties and morphological stabilities in organic solvents. The crosslinking between SF and chitosan took place mainly through Michael addition reactions. A main reaction between the amino groups in chitosan and o-quinone, the oxidation product of the tyrosyl residue in SF, was confirmed by UV spectroscopy. Measurements of viscosity and light scattering indicated that the crosslinked SF/chitosan conjugate was compact: it had a smaller particle size because of tight bonding forces between the SF and chitosan molecular chains. Thermal decomposition of SF/chitosan conjugates crosslinked by tyrosinase occurred at higher temperatures. The adhesiveness of the SF/chitosan conjugates decreased steadily as the crosslinking reaction progressed. We propose that this new crosslinking method be used for the preparation of silk fibroin/chitosan conjugates using tyrosinase. We expect that SF/chitosan conjugates crosslinked by tyrosinase can be used preferentially in biomedical applications because of its unique properties and non-toxicity.