• Journal of Korean Neurosurgical Society
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• v.30 no.9
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• pp.1059-1064
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• 2001

Objective : 6R-Tetrahydrobiopterin(BH4) is a cofactor for the aromatic amino acid hydroxylases which is essential for the biosynthesis of catecholamines and serotonin. It also acts as a cofactor for nitric oxide synthase, and stimulates the release of some neurotransmitters such as dopamine, serotonin, acetylcholine and glutamate. Recently, it has been reported that BH4 could induce cellular proliferation and enhance neuronal survival. This study was performed to investigate the antioxidative effect of BH4 on the various oxidative insults in mouse cerebral cortical cell cultures. Methods : Iron ion(FeCl2), zinc ion(ZnCl2), sodium nitroprusside(SNP) and buthionine sulfoximine(BSO, a glutathione depletor) were used as oxidants. Cell death was assessed by measurement of lactate dehydrogenase efflux to bathing media at the end of exposure. Result : All 4 oxidants induced neuronal cell death associated with cell body swelling, which was markedly inhibited by trolox($100{\mu}M$), a vitamin E analog. BH4($10-100{\mu}M$) markedly inhibited the neuronal cell death induced by all 4 oxidants($20{\mu}M\;Cu^{2+}$, $20{\mu}M\;Zn^{2+}$, $1{\mu}M$ SNP or 1mM BSO). However, BH4 failed to inhibit the neuronal cell death induced by 24hr exposure to $20{\mu}M$ NMDA. Conculsion : These results suggest that BH4 has antioxidative action independently of any actions of enzyme cofactor.

• Biomedical Science Letters
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• v.13 no.4
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• pp.325-332
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• 2007

Cell-mediated immune response (CMI) is a major immune protective mechanism against tuberculosis (TB) infection. Among several components involved in CMI, recent studies suggest that CD8+ T cells are important in controlling TB infection. In our previous report, we defined four Mycobacterium tuberculosis (MTB) derived epiotpe peptides specific for HLA-A*0201-restricted CD8+ T cells. These four peptides are $PstAl_{75-83}$, $ThyA_{30-38}$, $RpoB_{127-135}$ and $85B_{15-23}$. In this study, these epitope peptides specific CD8+ T cell responses in tuberculous pleurisy were investigated using ex vivo $IFN-\gamma$ elispot assay and intracellular $IFN-\gamma$ staining method. As a result, we observed these epitope peptide specific CD8+ T cell responses are induced in all three patients with tuberculous pleurisy suggesting that CD8+ T cells are involved in protective immune mechanism against MTB infection in tuberculous pleurisy. However, the CMI to mitogens and MTB antigens from pleural fluids of patients with tuberculous pleurisy does not seem to correlate with that from peripheral blood, although the sample size is too small to make any conclusion. In sum, the MHC I restricted CD8+ T cell responses seem to be induced efficiently in the pleural fluids, at the site of TB infection, in which the CMI is actively induced. In addition, these experiments suggest that MHC I restricted CD8+ T cell mediated immune responses are also involved in protective mechanism against MTB infection in extra-pulmonary TB.

• Land and Housing Review
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• v.2 no.3
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• pp.227-238
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• 2011

There are similarities between Korea and Japan in terms of national planning and development system and housing policies. Japan has suffered from great shifts of social and economic systems due to skyrocketing land prices for three times and the collapse of the bubble economy after the Second World War. The study reviews historically important changes in the national territory and housing policies for last 60 years in Japan. It also investigates changing trends and characteristics of many socioeconomic indicators with regard to population, housing and other fields in response to these policies. First of all, Japan has experienced significant economic growth before and after the 1960's, and the era of national rebuilding projects in the 1970's. After then, the period of the bubble economy has emerged since 1980; however, it suffered from skyrocketing land values between the late 1980's and the early 1990's, and the collapse of Japanese bubble economy in the early 1990's. In response, many urban regeneration policies and projects were proposed to recover the national economy since 2000. It is found that these national territory development and housing supply policies throughout the country have been influenced by the changing characteristics of social and economic conditions. Since the housing supply ratio in 1968 reached up to around 100% on average, Japan has been focusing attention to improving the residential and living quality for existing housing stock rather than supplying new housing units through large-scale new town projects. These experiences are full of helpful suggestions for our future housing and urban regeneration policies as we reach to more than 100% of housing supply ratio on average.

• Journal of Microbiology
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• v.34 no.4
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• pp.355-362
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• 1996

Complementation cloning of the argC, E, B, D, F, and G genes in Corynebacterium glutamicum was done by transforming the genomic DNA library into the corresponding arginine auxotrophs fo Escherichia coli. Recombinant plasmids containing 6.7 kb and 4.8kb fragments complementing the E. coli argB mutant were also able to complement the E. coli argC, E, A, D, and F mutants, indicating the clustered organization of the arginine biosynthetic genes within the cloned DNA fragments. The insert DNA fragments in the recombinant plasmids, named pRB1 AND pRB2, were physically mapped with several restriction enzymes. By further subcloning the entire DNA fragment containing the functions and by complementation analysis, we located the arg genes in the order of ACEBDF on the restriction map. We also determined the DNA nucleotide sequence of the fragment and report here the sequence of the argB gene. When compared to that with the mutant strain, higher enzyme activity of N-acetylglutamate kinase was detected in the extract of the mutant carrying the plasmid containing the putative argB gene, indicating that the plasmid contains a functional argB gene. Deduced amino acid sequence of the argB gene shows 45%, 38%, and 25% identity to that from Bacillus strearothermophilus, Bacillus substilus, and E. coli respectively. Our long term goal is genetically engineering C. glutamicum which produces more arginine than a wild type strain does.

• Korean Journal of Materials Research
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• v.8 no.9
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• pp.843-848
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• 1998

The Usages of composite materials have been steadily on the rise in the industries of automobiles, air crafts, shipbuilding and other structures for transportations. Commonly required in those industries are light weight and high strength of the structures. Consequently, serious efforts in research have been focused on searching for light materials and on developments and characterizations of advanced substitutes including various kinds of composite materials. In this investigation, transversely isotropic composite materials are chosen and formed into two kinds of beams; Euler-Bernoulli beam(thin team) and Timoshenko beam(thick beam) for determinations of elastic constants. As an experimental technique Impulse Excitation Method is utilized to measure resonance frequencies of the beams of the composite materials in vibration tests. Elastic constants are evaluated from measured resonance frequencies for the two types of beams to observe and establish possible existence of effects of rotary inertia and shear deformations.

• Korean Journal of Materials Research
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• v.9 no.8
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• pp.763-767
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• 1999

Composite materials have been increasingly used in automotive and aircraft industries, naturally leading to active researches on the materials. Carbon-epoxy composites, one of major composite materials, are investigated to determine their thermal characteristics. Under conditions of thermal fatigues composed of repeated heatings and coolings, variations of elastic constants are studied for the carbon-epoxy composites to reveal the thermal nature of the composites. In general, composite materials are known to have decreasing elastic constants with increasing temperatures. However, in contrary to this commonly observed behavior, the results obtained in this investigation for the elastic constants of the carbon-epoxy composites show unexpected phenomena in that the elastic constants initially increase with increasing temperatures to certain point and decrease later with further increase in temperatures when the carbon-epoxy composites are subjected to thermal fatigues.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2006.11a
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• pp.453-457
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• 2006

After the introduction of Professional Engineer System to secure superior technical personnel in 1963, the engineering license regulations were introduced in 1995 - the person qualified with either the academic back ground or career in the construction field can be authorized as a construction engineer- to cope with higher demands for construction engineers caused by revitalization of construction business such as 2 million house construction. As a result, the number of construction engineers has been increased drastically since year 2000, which caused serious problems in utilizing top technical certificate, the PE's. Recently, relating to the opening of technology market according to WTO agreement and mutual authentication among countries and etc., the government is preparing legal and systematic foundations to guarantee the professionalism of engineers. Through the exact supply-demand forecast of PE's reflecting these systematic aspects, we are going to analyze the problems in the supply-demand of PE's and suggest the systematic improvement plans for managing the supply-demand of PE's. The result of this research can be used for building efficient and consistent raising and utilizing system of PE's as well as supply and demand system of qualified PE's

• Textile Coloration and Finishing
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• v.25 no.2
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• pp.126-133
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• 2013

Although para-aramid fibers poss higher mechanical properties, they show very low resistance to sunlight exposure. This paper studied on the effect of nano-sol coated $TiO_2$ to improve the photo-stability of p-aramid fibers. Titanium dioxides were prepared by sol-gel method from titanium iso-propoxide at different R ratio ($H_2O$/titanium iso-propoxide). All samples were characterized by XRD, TEM and UV-vis spectrometer. The mechanical properties of p-aramid fabrics by $TiO_2$ nano-sol coating before and after sunlight irradiation were measured with tensile tester. XRD pattern of titanium dioxide particles was observed by mixing phase together with rutile and anatase type. The results showed, after sunlight irradiation, the decreased mechanical properties of the fiber. Furthermore, the sunlight irradiation obviously deteriorated the surface and defected areas of the fiber severely by photo-induced chain scission and end group oxidation in air.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.243-243
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• 2010

Low-temperature grown (LTG) InGaAs epilayers were grown by MBE technique for studying a correlation between terahertz (THz) emission and the intrinsic defects. The 1.2-um-thick Be-compensated LTG-InGaAs epilayers were prepared on SI-InP:Fe substrate at $200-250^{\circ}C$, and subsequently in-situ annealed under As environment at $550^{\circ}C$ for 5-30 minutes. The carrier concentration/mobility and the crystalline structure were analyzed by the Hall effect and the x-ray diffraction (XRD), respectively, and the carrier lifetime were determined by the fs time-resolved pump-probe spectroscopy. THz generation from LTG-InGaAs was carried out by a Ti-sapphire laser (800 nm) of a pulse width of 190 fs at a repetition of 76 MHz. Figure shows the spectral amplitude of generated waves in the THz region. As the growth temperature of epilayer increases, the amplitude is enhanced. However, two samples grown at $200^{\circ}C$, as-grown and annealed, show almost no difference in the spectral amplitude. This suggests that the growth temperature is critical in the formation of defect states involved in THz emission. We are now investigating the correlations between the XRD band attributed to defects, the Hall parameter, and the spectral amplitude of generated THz wave.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.236-236
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• 2010

단일접합 $n^+-p/p^+$ (p-emitter) 및 $p^+-n/n^+$ (n-emitter) GaAs 태양전지 (Solar Cell)를 각각 제작하여, 그 소자특성을 비교 분석하였다. AM 1.5 (1 sun, $100\;mW/cm^2$) 표준광을 조사할 경우, p-emitter/n-emitter 소자의 개방회로전압 (Voc), 단락회로전류 (Jsc), 충전율 (FF), 효율 (Eff)은 각각 0.910/0.917 V, $15.9/16.1\;mA/cm^2$, 78.7/78.9, 11.4/12.1%로서, n-emitter 소자가 다소 크지만 거의 비슷한 값을 가지고 있었다. 태양전지의 집광 특성을 분석하기 위하여 조사광의 출력에 따른 태양전지의 소자 특성을 측정하였다. 조사광 강도가 높아짐에 따라 p-emitter 소자의 특성은 점진적으로 증가하는 반면, n-emitter는 1.3 sun에서 약 1.4 배의 최대 효율 (17%)을 나타내고 조사광이 더 증가함에 따라 급격히 감소하는 특성을 보여 주었다. (그림 참고) 본 연구에서 사용한 2종류 소자의 층구조는 서로 반대되는 대칭구조로서, 모두 가까이에 위치하고 있는 표면전극 (surface finger) 방향으로 소수전하 (minority carrier)가 이동하고 다수전하 (majority carrier)는 기판 (두께 $350\;{\mu}m$)을 통한 먼 거리의 후면전극 (back electrode)으로 표류 (drift)되도록 설계되어 있다. 이때, n-emitter에서는 이동도 (mobility)와 확산길이 (diffusion length)가 높은 전자가 후면전극으로 이동하기 때문에 적정밀도의 전자-정공 쌍 (EHP)이 여기될 경우에는 Jsc와 Eff가 극대화되지만, 조사광 강도 또는 EHP가 더 높아질 경우에는 직렬저항의 증가와 함께 전류-전압 (I-V)의 이상인자 (ideality factor)가 커짐으로서 FF와 효율이 급격히 감소한 결과로 분석된다. 현재 전산모사를 통한 자세한 분석을 진행하고 있으며, 본 결과는 효율 극대화를 위한 최적 층구조 및 도핑 밀도 설계에 활용할 수 있을 것으로 판단된다.