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Process Optimization for Preparing High Performance PAN-based Carbon Fibers
Yun, Jeong-Hyeon,Kim, Bo-Hye,Yang, Kap-Seung,Bang, Yun-Hyuk,Kim, Sung-Ryong,Woo, Hee-Gweon Korean Chemical Society 2009 Bulletin of the Korean Chemical Society Vol.30 No.10
wet spun polyacrylonitrile (PAN) fiber precursors. The process variables chosen were treatment temperature, applied tension in stabilization process. The temperature profile of the stabilization was set on the basis of exothermic peaks of the differential scanning calorimetry (DSC) result. Both tensile strength and modulus increased with holding at onset temperatures of the exothermic peaks for extended duration, and with a higher heating rate up to the onset temperatures at a given applied tension among the experimental conditions. The increase in load monotonously increased the tensile modulus, on the other hand, the tensile strength was maximum at the load of 15 mg/filament (T15). The load 20 mg/ filament (T20) was considered to be exceeded to form oriented crystalline structure, possibly introducing more defects in the fiber than under load of T15. The sample CP3-T15 O5 H30 showed the best tensile properties among the samples experimented whose tensile properties are compatible with the commercialized grade of general purpose carbon fibers even at low carbonization temperature such as $800\;{^{\circ}C}$ (the carbonization temperature in the commercial process. 1300∼$1500\;{^{\circ}C}$).
Process Optimization for Preparing High Performance PAN-based Carbon Fibers
Jeong-Hyeon Yun,Bo-Hye Kim,Kap Seung Yang,Yun Hyuk Bang,Sung Ryong Kim,Hee-Gweon Woo 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.10
Optimum process conditions were investigated for maximizing the mechanical properties of the carbon fiber by from wet spun polyacrylonitrile (PAN) fiber precursors. The process variables chosen were treatment temperature, applied tension in stabilization process. The temperature profile of the stabilization was set on the basis of exothermic peaks of the differential scanning calorimetry (DSC) result. Both tensile strength and modulus increased with holding at onset temperatures of the exothermic peaks for extended duration, and with a higher heating rate up to the onset temperatures at a given applied tension among the experimental conditions. The increase in load monotonously increased the tensile modulus, on the other hand, the tensile strength was maximum at the load of 15 mg/filament (T15). The load 20 mg/filament (T20) was considered to be exceeded to form oriented crystalline structure, possibly introducing more defects in the fiber than under load of T15. The sample CP3-T15 O5 H30 showed the best tensile properties among the samples experimented whose tensile properties are compatible with the commercialized grade of general purpose carbon fibers even at low carbonization temperature such as 800 °C (the carbonization temperature in the commercial process. 1300∼1500°C ).
Long-term effects of rTMS on motor recovery in patients after subacute stroke.
Chang, Won Hyuk,Kim, Yun-Hee,Bang, Oh Young,Kim, Sung Tae,Park, Yun H,Lee, Peter K W Taylor Francis 2010 Journal of rehabilitation medicine Vol.42 No.8
<P>OBJECTIVE: Repetitive transcranial magnetic stimulation (rTMS) has been recognized as a promising intervention for treatment of stroke patients. However, most previous reports have described the short-term effects of rTMS on motor performance. We conducted a sham-controlled trial to evaluate long-term effects of high-frequency rTMS on motor recovery in subacute stroke patients. METHODS: Twenty-eight patients were randomly divided into two groups, and received either real or control rTMS. Both treatments were accompanied by motor practice. A daily dose of 1000 pulses of subthreshold 10 Hz rTMS was applied over the primary motor cortex of the affected hemisphere for 10 days within one month after onset of stroke. Motor function was assessed before and after treatment, and 3 months after the stroke. RESULTS: Motor function improved in both groups after treatment; however, patients who received real rTMS experienced additional improvement in motor function of the affected upper limb. Over 3 months after the stroke, the time and type of intervention for the Motoricity Index of the affected upper extremity showed significant interaction. CONCLUSION: Positive long-term effects on motor recovery could be achieved after 10 daily sessions of high-frequency rTMS in conjunction with motor practice during the sub-acute period of stroke.</P>
김정혁 ( Jung Hyuk Kim ),허환 ( Hwan Herr ),방기태 ( Ki Tae Bang ),배강우 ( Kwang Woo Bae ),장현규 ( Hyun Kyu Chang ),이명용 ( Myoung Yong Lee ),이인선 ( In Sun Lee ),윤보영 ( Bo Young Yoon ),이윤우 ( Yun Woo Lee ) 대한류마티스학회 2004 대한류마티스학회지 Vol.11 No.3
Behcet`s disease (BD) is a chronic inflammatory disease, involving several organs. It is well known that there are the marked regional differences in the disease expression of BD. In case of the vascular involvement in BD, the frequency rate has been described in 25∼30% among the patients from the Middle East, whereas it has been noted in 5∼15% in our country. In general, BD associated with large vessel lesions is named vasculo-BD. On the other hand, the cardiac involvement in BD has rarely been reported in the literature. Ebstein anomaly is a kind of malformation that is characterized by a downward displacement of the tricuspid valve into the right ventricle. We reported a 54-year-old male patient with vasculo-BD who had inferior vena cava obstruction and Ebstein anomaly. The association of Ebstein anomaly with vasculo-BD is considered to be coincidental. To the best of our knowledge, this is the first case of Ebstein anomaly associated with BD.
Extremely low‐frequency magnetic fields modulate nitric oxide signaling in rat brain
Cho, Sung In,Nam, Yun Sung,Chu, Li Ying,Lee, Jong Hyuk,Bang, Joon Seok,Kim, Hye Ryoun,Kim, Hyoung‐,Chun,Lee, Yu Jeung,Kim, Hyeong‐,Dong,Sul, Jung Duk,Kim, Daejin,Chung, Yoon Hee,Jeong, Ji Wiley Subscription Services, Inc., A Wiley Company 2012 BioElectroMagnetics Vol.33 No.7
<P><B>Abstract</B></P><P>Our previous study has shown that an extremely low‐frequency magnetic field (ELF‐MF) induces nitric oxide (NO) synthesis by Ca<SUP>2+</SUP>‐dependent NO synthase (NOS) in rat brain. The present study was designed to confirm that ELF‐MF affects neuronal NOS (nNOS) in several brain regions and to investigate the correlation between NO and nNOS activation. The exposure of rats to a 2 mT, 60 Hz ELF‐MF for 5 days resulted in increases of NO levels in parallel with cGMP elevations in the cerebral cortex, striatum, and hippocampus. Cresyl violet staining and electron microscopic evaluation revealed that there were no significant differences in the morphology and number of neurons in the cerebral cortex, striatum, and hippocampus. Differently, the numbers of nNOS‐immunoreactive (IR) neurons were significantly increased in those cerebral areas in ELF‐MF‐exposed rats. These data suggest that the increase in NO could be due to the increased expression and activation of nNOS in cells. Based on NO signaling in physiological and pathological states, ELF‐MF created by electric power systems may induce various physiological changes in modern life. Bioelectromagnetics 33:568–574, 2012. © 2012 Wiley Periodicals, Inc.</P>