• Bulletin of the Korean Chemical Society
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• v.34 no.12
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• pp.3733-3737
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• 2013

Polyacrylonitrile (PAN)-based ultrafine fibers and carbon fibers were produced by wet-spinning, and the crystal sizes and thermal and mechanical properties of the fibers were investigated. Scanning electron microscopy revealed that the superfine fibrils in the surfaces of the PAN/polyvinyl acetate (PVA) blend fibers increased slightly with increasing PAN content before removal of the PVA. Differential scanning calorimetry indicated that the PAN and PVA in the blend fibers do not mix and, therefore, each maintains their inherent thermal characteristics. The crystal sizes of the blend fibers prepared by removing PVA with water increased at 5 wt % water. The extent of the reaction of the PAN carbon fibers, as calculated from the FT-IR spectra, is maximized at the stepwise temperature of $230^{\circ}C$, and the density increased significantly above this temperature. The carbon fibers had relatively good mechanical properties, as shown by their tensile strength and modulus values of 2396 MPa and 213 GPa, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.12
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• pp.1167-1171
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• 2006

This work describes the effect of binders, such as carboxymethylcellulose (CMC), CMC+ Polytetrafluoroethylene (PTFE) and PTFE, on the electrochemical and mechanical properties of activated carbon-electrode for electric double layer capacitor. The cell capacitors using the electrode bound with binary binder composed of CMC and PTFE, especially in composition CMC PTFE = 60 : 40 wt.%, has better rate capability and the lower internal resistance than those of the cell capacitor with CMC. On the other hand, the sheet type electrode kneaded with PTFE was bonded with conductive adhesive on Al foil. This cell capacitor using the electrode with PTFE exhibited the best mechanical properties and rate capability compared to the CMC and CMC+PTFE one. These behaviors could be explained by the well-developed network structure of PTFE fibrils doting the kneading process.

• Journal of the Korean Society of Clothing and Textiles
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• v.25 no.1
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• pp.144-153
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• 2001

The effect of crosslinking on hand of the cellulase treated Tencel fabrics was investigated. Tencel fabrics were crosslinked with DMDHEU, mechanically prefibrillated, hydrolyzed by cellulase, and treated with softener. The treated fabrics were characterized by add-on, weight loss, DP rating, WRA, strength, SEM analysis and hand measurement. As DMDHEU concentration increased, weight loss of DMDHEU/cellulase treated fabrics decreased. However, cellulase treatment decreased DP properties and strength retention. Less fibrils were observed in the cellulase treated fabrics after DMDHEU treatment than the cellulase treated ones. It was confirmed that crosslinking with DMDHEU treatment was effective to control fibrillation. At 5% of DMDHEU concentration, DMDHEU/cellulase treated fabrics showed softer, smoother and bulkier hand compared with other treated fabrics. Among mechanical properties, bending and shearing properties were decreased progressively through DMDHEU, cellulase, and softener treatment. DMDHEU treatment contributed to impart resilience, cellulase treatment to bulkiness and softener treatment to smoothness. As the treatment of DMDHEU, cellulase, and softener progressed NUMREI, FUKURAMI, and THV increased with the exception of KOSHI.

• Journal of Periodontal and Implant Science
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• v.23 no.2
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• pp.219-227
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• 1993

The purpose of the present study was to evaluate the effects of 5% tetracycline(Tc) with or without citric acid on periodontally diseased root surfaces. Six single-rooted teeth extracted from one patient was selected and received thorough scaling and root planning, followed by saline irrigation. Each one tooth was divided into eight fragments with a thin separating disc. Total 48 fragments were prepared and setted into 4 groups for this study. Group I (control group)were treated with saline. Group II were treated with 5% Tc gel. Group III were treated with 33% citric acid-5% Tc gel. Group IV were treated with Tc solution. All the specimens are evaluated under Scanning Electron Microscope(SEM). Group I showed large amount of debris in spite of thorough scaling and root planing, but Group II, III & IV showed clean and soft root surface texture. In higher magnification(x3, 000), Group II, III & IV showed nunmerous dentinal tubules, especially Group IV showed collagen fibrils. In the present study, Tc gel and Tc gel with citric showed clinically successful result when treated on periodontally diseased root surface, in vitro.

• Journal of the Korean Society of Food Science and Nutrition
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• v.26 no.3
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• pp.501-506
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• 1997

As pyridinoline is one of the predominant cross-lins in a mature collagen, pyridinoline formation may be an essential step during the growth process to obtain normal mechanical strength in collagen fibrils. However, the excess formation of pyridinoline in collagen will probably make the tissue stiffer, less soluble and less digestible by enzymes. We investigated the changes of pyridinoline of bone collagen and the role of ascforbic acid(AsA) on the formation of pyridinoline. The pyridinoline content of bone collagen significantly increased during incubation for 1~5 weeks at 37$^{\circ}C$ in vitro. The addition of AsA decreased pyridinoline to half the amount found in controls with 5 week incubation. When dehydroascorbic acid(DHA) and L-2, 3-diketogulonic acid (DKG), the oxidative products of AsA, were supplemented to bone collagen solution instead of AsA, the content of pyridinoline in bone collagen was about 80% or 70% that of controls, respectively. These results suggest that pyridinoline content decreases by the addition of AsA in vitro. Furthermore, it was shown that AsA in oxidized from also affected the formation of pyridinoline.

• Journal of the Korean Society of Food Science and Nutrition
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• v.30 no.2
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• pp.307-313
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• 2001

Iron excess is known to affect long-term iron accumulation and tissue change such as fibrosis in liver. To determine the changes of expression level of genes associated with fibrosis by short-term iron exposure, we measured liver mRNA levels by reverse transcription polymerase chain reaction (RT-PCR) in rats fed dietary carbonyl iron (3%, wt/wt) for 9 weeks. The results showed that the expression of the collagen (I, III) and transforming growth factor (TGF)-$\beta$I mRNAs was enhanced in high-dose iron treated rat, compared to normal-dose iron treated rat. An electron microscopy study revealed that excess iron caused increase of collagen fibrils in liver. The cell shapes and compositions of hepatocytes and extracellular matrix(ECM) in liver were changed by the iron-treatment. Also, necrosised hepatocytes were broadly seen in ECM. Taken together, we suggest that iron overload affects changes of collagen and TGF-$\beta$I gene expression and these changes are associated with liver fibrogenesis.

• Applied Microscopy
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• v.38 no.2
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• pp.135-140
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• 2008

In this study, I investigated on the ultrastructure of scalp skin from full term baby mummy by using transmission and scanning electron microscopy. The baby mummy was found within the uterus of a 16th century (Joseon Dynasty) mummified woman aged 20${\sim}$30 years old. In scanning electron microscopic study, I found that the outer surface of scalp skin containing of sweat gland and stratum corneum are well preserved. The skin of the scalp measured about 1 mm in thickness and the epidermis was well distinguished from the dermis. In transmission electron microscopy, the shape and structure of the epithelial cells were not confirmed. I also observed well preserved collagen fibers composed of collagen fibrils with cross banding pattern ultrastructurally. But, the other connective cells were not observed due to decomposition of the dermis.

• Textile Coloration and Finishing
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• v.3 no.1
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• pp.1-7
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• 1991

The influences, that various mercerization conditions had on the dying property of cotton fiber, were studied. Crystallization degrees accompained by lattice transformation of slack-mercerized cotton by IR spectroscopic analysis and morphology of the slack-merceized cotton by SEM were observed in this research. The above results were as follows; 1. Equilibrium dye adsorption rates of slack-mercerized cotton with C. I. Reactive Blue 19 were gained in the case of 8M NaOH, $10^{\circ}C$, 20 min., about 2 times as large as the rates of untreated cotton and gained about 2.5 times in the case of 8M $NH_3$, $10^{\circ}C$, , 20 min. 2. Equilibrium dye adsorption rates of slack-mercerized cotton with C. I. Reactive Blue 2 were gained in the case of 2M NaOH, $10^{\circ}C$, 20 min., about 1.7 times as large as the rates of untreated cotton and gained about 2.4 times in the case of 8M $NH_3$, $10^{\circ}C$, 20 min. 3. It was confirmed by SEM that untreated cotton fibrils are formed in the shape of screw and treated cotton is rearranged in the direction of fiber axis.

• Journal of Animal Science and Technology
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• v.57 no.10
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• pp.30.1-30.4
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• 2015

The present study was aimed to study the light and electron microscopic studies of thymic Hassall's corpuscles was done in various age groups of Nandanam Chicken ranging from day-old to forty weeks. Hassall's corpuscles are special, unique structures present in thymic medulla and also in the cortex of all the age groups of Nandanam chicken (from hatch to forty weeks) in the present study. Size of the Hassall's corpuscles in the medulla is larger than the ones present in the cortical region of thymus. The Hassall's corpuscles are made up of structureless eosinophilic mass surrounded by concentrically arranged reticuloepithelial cells. Under electron microscope, the Hassall's corpuscles were composed of reticuloepithelial cells interconnected by many desmosomes. The epithelial cells had abundance of cytoplasmic fibrils and desmosomes with few mitochondria and ribosomes. The nucleus was oval or round which was slightly indented. The centre of the Hassall's corpuscles was appeared either solid or cystic. The cystic corpuscles had cell debris within the cyst lumen.

• Smart Structures and Systems
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• v.17 no.2
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• pp.275-296
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• 2016

This paper focuses on developing a new configuration on magnetorheological (MR) brake damper as prosthetic knee. Prosthetic knee uses magnetic fields to vary the viscosity of the MR fluid, and thereby its flexion resistance. Exerted transmissibility torque of the knee greatly depends on the magnetic field intensity in the MR fluid. In this study a rotary damper using MR fluid is addressed in which a single rotary disc will act as a brake while MR fluid is activated by magnetic field in different walking gait. The main objective of this study is to investigate a prosthetic knee with one activating rotary disc to accomplish necessary braking torque in walking gait via T-shaped drum with arc surface boundary and implementing of Newton's equation of motion to derive generated torque at the inner surface of the rotary drum. For this purpose a novel configuration of a T-shaped drum based on the effects of a material deformation process is proposed. In this new design, the T-shaped disc will increase the effective areas of influences in between drum and MR fluid together and the arc wall crushes the particles chains (fibrils) of the MR fluid together instead of breaking them via strain in a conventional MR brake. To verify the proposed MR brake, results of the proposed and conventional MR brakes are compared together and demonstrated that the resisting torque of the proposed MR brake is almost two times greater than that of the conventional brake.