• 미생물학회지
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• 제46권4호
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• pp.359-365
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• 2010

조릿대 근권토양으로부터 분리한 방선균 50균주를 대상으로 고추 세균성 점무늬병원균(Xanthomonas axonopodis pv. vesicatoria)의 항균활성 12균주를 선발하였다. 이들 항균활성 12균주의 계통학적 위치를 검토한 결과, 모두 Streptomyces 속의 Cluster II에 속하는 특징을 나타내었다. JR-24 균주는 최소저해 농도(MIC) 10 ${\mu}l$/disc를 나타내었으며, 배양액 5 ${\mu}l$/ml를 처리 하여 12시간 배양한 결과 Xanthomonas axonopodis pv. vesicatoria에 강한 생육저해효과를 나타내어 최우수 균주로 선발되었다. 항균활성 균주 JR-24의 16S rRNA 유전자 염기서열을 검토한 결과, Streptomyces galbus $DSM40089^T$ (X79852)와 98.1%, Streptomyces longwoodensis $LMG20096^T$ (AJ781356)와 98% 그리고 Streptomyces capoamus $JCM4734^T$ (AB045877)와 97.8%의 상동성을 나타내었다. API 20NE와 API 50CHE를 이용하여 JR-24 균주의 생리 생화학적 특성을 확인한 결과, L-arabinose, D-fructose, D-glucose, D-galactose을 이용하며 gelatin, protein, starch에 대하여 분해능이 있는 것으로 확인되었다. 주요지방산으로는 iso-$C_{14:0}$ (25.93%), iso-$C_{15:0}$ (10.13%), anteiso-$C_{15:0}$ (19.29%) 그리고 iso-$C_{16:0}$ (20.35%) 등을 함유하였으며, 퀴논종은 MK-9 ($H_4$) 4.37%, MK-9 ($H_6$) 51.22% 그리고 MK-9 ($H_8$) 49.47%로 동정되었다. Streptomyces sp. JR-24 균주의 계통학적 특성을 근연종인 Streptomyces galbus $DSM40089^T$와 비교한 결과, 다수의 표현형적 및 계통학적 차이를 나타내었다. 본 연구에서 분리된 Streptomyces sp. JR-24는 친환경 미생물제제 개발을 위한 유전자원 확보에 있어서 매우 큰의의가 있을 것으로 사료 된다.

• Bulletin of the Korean Chemical Society
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• 제29권2호
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• pp.413-416
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• 2008

A synthesis route to ordered mesoporous carbons with controllable nitrogen content has been developed for high-performance EDLC electrodes. Nitrogen-doped ordered mesoporous carbons (denoted as NMC) were prepared by carbonizing a mixture of two different carbon sources within the mesoporous silica designated by KIT-6. Furfuryl alcohol was used as a primary carbon precursor, and melamine as a nitrogen dopant. This synthesis procedure gave cubic Ia3d mesoporous carbons containing nitrogen as much as 13%. The carbon exhibited a narrow pore size distribution centered at 3-4 nm with large pore volume (0.6-1 cm3 g-1) and high specific BET surface area (700-1000 m2 g-1). Electrochemical behaviors of the NMC samples with various N-contents were investigated by a two-electrode measurement system at aqueous solutions. At low current density, the NMC exhibited markedly increasing capacitance due to the increase in the nitrogen content. This result could be attributed to the enhanced surface affinity between carbon electrode and electrolyte ions due to the hydrophilic nitrogen functional groups. At high current density conditions, the NMC samples exhibited decreasing specific capacitance against the increase in the nitrogen content. The loss of the capacitance with the N-content may be explained by high electric resistance which causes a significant IR drop at high current densities. The present results indicate that the optimal nitrogen content is required for achieving high power and high energy density simultaneously.

• Carbon letters
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• 제27권
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• pp.90-97
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• 2018

Electromagnetic interference (EMI) shielding is an important issue in modern daily life due to the increasing prevalence of electronic devices and their compact design. This study estimated EMI-shielding effect (EMI-SE) of small ($8-14{\times}17mm$) Hanji (Korean traditional paper) doped with carbon nanotubes (CNTs) and compared to Hanji without CNT using $^2H$ (92.1 MHz) and $^{23}Na$ (158.7 MHz) nuclear magnetic resonance (NMR) peak area data obtained from 1 M NaCl in $D_2O$ samples in capillary tubes that were wrapped in the Hanji samples. The simpler method of using the variation of reflected power and tuning frequency by inserting the sample into an NMR coil was also tested at 242.9, 158.7, and 92.1 MHz. Overall, EMI shielding was relatively more effective at the higher frequencies. Our results validated that NMR methods to be useful to evaluate EMI-SE, particularly for small, flexible shielding materials, and demonstrated that EMI shielding by absorption is dominant in Hanji mixed with CNT.

• Applied Microscopy
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• 제49권
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• pp.1.1-1.10
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• 2019

Joints of three-dimensional (3D) rutile-type (r) tin dioxide ($SnO_2$) nanowire networks, produced by the flame transport synthesis (FTS), are formed by coherent twin boundaries at $(101)^r$ serving for the interpenetration of the nanowires. Transmission electron microscopy (TEM) methods, i.e. high resolution and (precession) electron diffraction (PED), were utilized to collect information of the atomic interface structure along the edge-on zone axes $[010]^r$, $[111]^r$ and superposition directions $[001]^r$, $[101]^r$. A model of the twin boundary is generated by a supercell approach, serving as base for simulations of all given real and reciprocal space data as for the elaboration of three-dimensional, i.e. relrod and higher order Laue zones (HOLZ), contributions to the intensity distribution of PED patterns. Confirmed by the comparison of simulated and experimental findings, details of the structural distortion at the twin boundary can be demonstrated.

• 대한금속재료학회지
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• 제48권1호
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• pp.57-61
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• 2010

Nanosized surface structures of Cu powders were investigated at the atomic scale by field-emission transmission electron microscope techniques. The nanoscale surface oxide layer on the Cu powder was analyzed to be the $CU_2O$ phase by electron diffraction pattern and electron energy-loss spectroscopy. In addition, it was found from high-resolution transmission electron microscopy study that there are formed no surface oxide layers on the surface of alkanethiol coated Cu powders.

• Bulletin of the Korean Chemical Society
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• 제32권1호
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• pp.95-99
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• 2011

$CaTi_{1-x}Fe_xO_3(0{\leq}x{\leq}0.4)$ solid solution photocatalysts were synthesized by iron doping during the conventional solid state reaction at $1100^{\circ}C$ for 5 h and characterized by ultraviolet-visible (UV-vis) absorption spectroscopy, X-ray diffraction, morphological analysis. We found that $CaTi_{1-x}Fe_xO_3$ samples not only absorb UV but also the visible light photons. This is because the Fe substitution at Ti-site in $CaTi_{1-x}Fe_xO_3$ lattice induces the band transition from Fe3d to the Fe3d + Ti3d hybrid orbital. The photocatalytic activity of Fe doped $CaTiO_3$ samples for hydrogen production under UV light irradiation decreased with the increase in the Fe concentration. There exists an optimized concentration of iron in $CaTiO_3$, which yields a maximum photocatalytic activity under visible light ($\lambda\geq420nm$) photons.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.176.1-176.1
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• 2014

Graphene has attracted an increasing attention due to its extraordinary electronic, mechanical, and thermal properties. Especially, the two dimensional (2D) sheet of graphene with an extremely high surface to volume ratio has a great potential in the preparation of multifunctional nanomaterials, as 2D supports to host metal nanoparticles (NPs). Copper oxide is widely used in various areas as antifouling paint, p-type semiconductor, dry cell batteries, and catalysts. Although the copper oxide(II) has been well known for efficient catalyst in C-N cross-coupling reaction, copper oxide(I) has not been highlighted. In this research, CuO and Cu2O nanoparticles (NPs) dispersed on the surface of grapehene oxide (GO) have been synthesized by impregnation method and their morphological and electronic structures have been systemically investigated using TEM, XRD, and XAFS. We demonstrate that both CuO and Cu2O on graphene presents efficient catalytic performance toward C-N cross coupling reaction. The detailed structural difference between CuO and Cu2O NPs and their effect on catalytic performance are discussed.

• Nano
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• 제13권12호
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• pp.1850139.1-1850139.10
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• 2018

$Co_3O_4$ nanocrystals have been synthesized via an ordinary one-step calcination of a cobalt-based 2D coordination polymer [Co(tfbdc)(4,4'-bpy)$(H_2O)_2$]. As an anode material for lithium-ion batteries, the obtained $Co_3O_4$ nanocrystals exhibit high reversible capacity, excellent cyclic stability and better rate capability. The reversible capacity of the $Co_3O_4$ nanocrystals maintains $713mA\;h\;g^{-1}$ after 50 cycles at a current density of $50mA\;g^{-1}$. Our results confirm that searching for metal oxides nanomaterials used as anode materials of lithium ion batteries via the calcinations of 2D coordination polymer is a new route.

• Bulletin of the Korean Chemical Society
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• 제34권4호
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• pp.1077-1080
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• 2013

Fluorinated polymaleimides with high thermal stability and low optical absorption loss in the optical communication wavelength of $1.55{\mu}m$ were investigated for application in low-loss waveguide materials. The fluorinated polymaleimides were prepared from two monomers phenylmaleimide (H-PMI) and pentafluorophenylmaleimide (F-PMI). All synthesized copolymers had high thermal stability (decomposition temperature $(T_d)=380-430^{\circ}C$). The refractive index of the copolymers could be tuned from 1.4969 to 1.5950 in the TE mode and from 1.4993 to 1.5932 for the TM mode at 632.8 nm by copolymerizing different weight ratios of H-PMI and F-PMI. The refractive index of the copolymers decreased with increasing F-PMI content. In addition, when the amount of F-PMI was increased, optical loss and absorption loss at 632.8 nm and 1550 nm, respectively, decreased.

• 한국산업보건학회지
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• 제26권2호
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• pp.225-236
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• 2016

Objectives: Nanomaterials have been used in various fields. As use of nanoproducts is increasing, workers dealing with nanomaterials are also gradually increasing. Exposure assessments for nanomaterials have been carried out for protection of worker's health in workplace. Exposure studies were mainly focused on manufacturing processes, but these studies on after-treatment processes such as refinement, weighing, and packing were insufficient. So, we investigated exposure characteristics of particles during after-treatment processes of $Al_2O_3$ fibers and Ni powders. Methods: Mass-production of Ni powder process was carried out in enclosed capture-type canopy hood. In a developing stage, $Al_2O_3$ was handled with a local ventilation unit. Exposure characteristics of particles were investigated for $Al_2O_3$ fiber and Ni powder processes during the periods of 10:00 to 16:00, 20 May 2014 and 13:00 to 16:00, 21 May 2014, respectively. Three real-time aerosol instruments were utilized in exposure assessment. A scanning mobility particle sizer(SMPS, nanoscan, model 3910, TSI) and an optical particle counter(OPC, portable aerosol spectrometer, model 1.109, Grimm) were used to determine the particle size distribution in the size range of 10-420 nm and $0.25-32{\mu}m$, respectively. In addition, a nanoparticle aerosol monitor(NAM, model 9000, TSI) was used to measure lung-deposited nanoparticle surface area. Membrane filters(isopore membrane filter, pore size of 100 nm) were also used for air sampling for the FE-SEM(model S-5000H, Hitachi) analysis using a personal sampling pump(model GilAir Plus by 2.5 L/min, Gilian). Conclusions: For Ni powder after-treatment process, only 27% increase in particle concentration was found during the process. However, for $Al_2O_3$ fiber after-treatment process, significant exposure(1.56-3.34 times) was observed during the process.