• Progress in Superconductivity
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• 제9권1호
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• pp.62-67
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• 2007

The effects of the heat-treatment temperature on the carbon (C) substitution amount, full width at half maximum (FWHM) value, critical temperature ($T_c$), critical current density ($J_c$) have been investigated for 10 wt % malic acid ($C_4H_6O_5$)-doped $MgB_2/Fe$ wires. All the samples were fabricated by the in-situ powder-in-tube (PIT) method and heat-treated within a temperature range of $650^{\circ}C$ to $1000^{\circ}C$. As the heat-treatment temperature increased, it seemed that the lattice distortion was increased by a more active C substitution into the boron sites from the malic acid addition. These increased electron scattering defects seemed to enhance the $J_c-H$ properties in spite of an improvement in the crystallinity, such as a decrease of the FWHM value and an increase of the $T_c$. Compared to the un-doped wire heat-treated at $650^{\circ}C$ for 30 min, the $J_c$ was enhanced by the C doping in a high-field regime. The wire heat-treated at $900^{\circ}C$ resulted in a higher magnetic $J_c$ of approximately $10^4\;A/cm^2$ at 5 K and 8 T.

• Bulletin of the Korean Chemical Society
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• 제2권4호
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• pp.125-129
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• 1981

The addition reactions of cysteine without blocking amino and carboxyl groups to substituted and unsubstituted ${\beta}$-nitro-styrene derivatives were investigated. ${\beta}$-Nitrostyrene(1a), p-methyl-${\beta}$-nitrostyrene(1b), 3,4,5-trimethoxy-$[\beta}$ -nitrostyrene(1c), $[\varpi}$-3,4-methylenedioxy-${\beta}$ -nitrostyrene(1d), o-, m- and p-chloro-${\beta}$ -nitrostyrene (1e, 1f, 1g) and o-, m- and p-methoxy-${\beta}$-nitrostyrene (1h, 1i, 1j) easily undergo addition reactions with cysteine to form S-(2-nitro-1-phenylethyl)-L-cysteine(3a), S-[2-nitro-1-(p-methyl)phenyl-ethyl]-L-cysteine(3b), S-[2-nitro-1-(3',4',5'-trimethoxy) phenylethyl]-L-cysteine(3c), S-[2-nitro-1-($[\vatpi}$ -3',4'-methylenedioxy)phenylethyl]-L-cysteine(3d), S-[2-nitro-1-(o-chloro)phenylethyl]-L-cysteine(3e), S-[2-nitro-1-(m-chloro)-phenylethyl]-L-cysteine(3f), S-[2-nitro-1-(p-chloro)phenylethyl]-L-cysteine(3g), S-[2-nitro-1-(o-methoxy)phenylethyl]-L-cysteine(3h), S-[2-nitro-1-(m-methoxy)phenylethyl]-L-cysteine(3i) and S-[2-nitro-1-(p-methoxy)phenylethyl]-L-cysteine(3j), respectively. The structure of adducts were confirmed by means of UV-spectrum, IR-spectrum, molecular weight measurement and elemental analysis. The various factors effecting the yield of cysteine adducts to ${\beta}$-nitrostyrene derivatives were also studied.

• 한국미생물·생명공학회지
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• 제31권3호
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• pp.271-276
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• 2003

한국의 전통 대두발효식품인 청국장에서 혈전용해능이 우수한 미생물을 분리하였으며, 이를 동정한 결과 B.amyloliquefaciens D4로 명명하였다. 혈전용해효소의 대량분비를 위해 N-methyl-N-nitro-N-nitrosoguanidine을 사용한 돌연변이를 유도하여 B. amyloliquefaciens D4-7 변이주를 얻었으며, plasmin 1 U/ml 6.5배 정도의 높은 혈전분해능을 나타내었다. B. amyloliquefaciens D4-7는 분리대두단백배지에서 혈전용해효소 분비능이 가장 우수하였다. B. amyloliquelaciens D4-7가 생산하는 혈전용해효소의 최적 활성조건은 pH 10, 5$0^{\circ}C$이었고, pH 7.0 에서 pH 11 사이에서 상대적으로 안정하였으며, $50^{\circ}C$에서 30분간 방치하였을 경우 50%의 활성이 유지되었다. 또한, NaCl, glycerol 또는glucose 첨가에 의해 혈전용해효소의 저장안정성이 높아지는 것을 확인할 수 있었다.

• 마이크로전자및패키징학회지
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• 제6권4호
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• pp.55-59
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• 1999

전자 패키징에 적용 가능한 납성분이 포함되어 있지 않는 Bi계저융점유리의 연구를 행하였다. Bi계유리중, 70wt% $Bi_2O_3$+ l5wt% $B_2O_3$ + 8wt% $SiO_2$+ 2wt% $P_2O_5$ + 4wt% $A1_2O_3$ + lwt%ZnO 성분의 유리는 융점이 약 $550^{\circ}C$ 였으며, $P_2O_5$의 함량에 따라서 그 융점이 변화하였다. 10wt%이상의 $P_2O_5$ 첨가에서는 $450^{\circ}C$의 열처리로 결정화가 진행되었다. $B_2O_3$가 많이 함유된 조성의 유리에서는 그 융점이 상승하였다.

• 소성∙가공
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• 제24권1호
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• pp.44-51
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• 2015

The current study seeks to examine the effects of V and C additions on the mechanical and low thermal expansion properties of a high strength invar base alloy. The base alloy (Fe-36%Ni-0.9%Co-2.75%Mo-0.7Cr-0.23Mn-0.17Si-0.3%C, wt.%) contains $Mo_2C$ carbides, which form as the main precipitate. In contrast, alloys with additions of 0.4%V+0.3%C (alloy A) or 0.4%V+0.45%C (alloy B) contain $Mo_2C$+[V, Mo]C carbides. The average thermal expansion coefficients of these high strength invar based alloys were measured in the range of $5.16{\sim}5.43{\mu}m/m{\cdot}^{\circ}C$ for temperatures of $15{\sim}230^{\circ}C$. Moreover, alloy B showed lower thermal expansion coefficient than the other alloys in this temperature range. For the mechanical properties, the [V, Mo]C improved hardness and strengths(Y.S. and T.S.) of the high strength invar base alloy. T.S.(tensile strength) and Y.S.(yield strength) of hot forged alloy B specimen were measured at 844.6MPa and 518.0MPa, respectively. The tensile fractography of alloy B exhibited a ductile transgranular fracture mode and voids were initiated between the [V, Mo]C particles and the matrix. Superior properties of high strength and low thermal expansion coefficient can be obtained by [V, Mo]C precipitation in alloy B with the addition of 0.4%V and 0.45%C.

• 한국분말재료학회지
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• 제4권2호
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• pp.113-121
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• 1997

The densification of the compacts of Co+32%Cr+20%W+l.5%C, Co+32%Cr+20%W+3.0%C and Co+32%Cr+20%W+4.5%C sintered under $H_2$ gas or vacuum was investigated. The effect of V and B addition on the densification was also investigated. The densification of these compacts were always incomplete regardless of sintering atmosphere, temperature and time. The amounts of oxygen and carbon in compacts sintered in $H_2$ for 3.6ks at 1523K were 0.105~0.160 mass% and 0.33~0.89 mass%, respectively. And those in vacuum were 0.028~0.032% and 0.957~4.08%, respectively. Relative density(Ds) of Co+29%Cr+17%W+3.0%C compact containing 6%V and Co+32%Cr+20%W+2.97%C compact containing 0.03%B were 99 and 100%, respectively, indicating complete densification by solid phase sintering. Victors hardness of sintered compacts containing 6%V or 0.03%B were 632 and 568, showing 50~60% increase in comparison to those without V or B. These results can be explained in terms of oxidation/reduction of oxides and equilibrium pressure of CO in isolated pore, instead of presence of liquid formation and grain boundary separation from pores due to large grain growth.

• 대한소아치과학회지
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• 제34권2호
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• pp.299-308
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• 2007

Streptococcus mutans Ingbritt의 비수용성 글루칸을 합성하는 효소인 glucosyltransferase B 및 C의 mRNA 발현에 대한 각 당의 영향을 fluorescent in situ hybridization(FISH) 방법으로 관찰하여 다음의 결과를 얻었다. 1. 1% 설탕이 함유된 BHI 배지에서 S. mutans Ingbritt를 접종하여 배양할 때 배양 9시간 째 gtfB 및 gtfC유전자의 mRNA가 발현이 급격히 증가하였다. 2 BHI 액체배지에 설탕을 첨가한 경우 gtfB및 gtfC유전자의 mRNA가 발현되었으며, 10% 설탕을 첨가한 경우 1%와 5%보다 gtfB 및 gtfC 유전자의 발현이 감소되었다. 3. 1% 설탕이 첨가된 BHI 액체 배지에 당을 첨가한 경우 포도당은 10% 첨가하였을 때 gtfB 및 gtfC 유전자의 mRNA 발현이 감소하였고, 과당의 경우 1% 첨가한 경우 감소하여 5% 와 10%에서는 gtfB및 gtfC 유전자가 거의 발현되지 않았다. 4. 자일리톨의 경우 1%부터 gtfB및 gtfC유전자 mRNA 발현이 대조군보다 감소하였고, 5%와 10%에서는 두 유전자 모두 발현이 현저하게 감소하였다. 5. 유당의 경우 두 유전자의 발현에 거의 영향을 미치지 않는 것으로 관찰되었고, 솔비톨의 경우 각 농도에서 두 유전자의 발현이 대조군보다 감소하였다. 결론적으로 비수용성 글루칸 합성하는 gtfB및 gtfC 유전자의 mRNA 발현이 포도당, 과당 자일리톨 첨가에 의해 감소함을 알 수 있었다.

• 미생물학회지
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• 제43권4호
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• pp.304-310
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• 2007

Bacillus cereus 1-1 균주는 광이 없는 호기적 환경에서 levulinic acid와 같은 저해제 처리 없이도 5-aminolevulinic acid (ALA)를2 mM까지 생산하였다. B. cereus 1-1 균주는 TCY 배지에서 전 배양과 본 배양을 18시간 동안 지속하고, 배지의 pH가 6.8에 도달하는 대수기 후기에 acetic acid를 비롯한 유기산들을 16 mM 첨가하였을 때 많은 ALA를 생산하였으며, 본 배양 시작시 0.3% glucose를 첨가하는 것이 효과적이었다. Acetic acid 대신 glutamic acid를 첨가하였을 때 ALA 생산이 8시간 이상 지속되었고, $40\;{\mu}M$의 gabaculine을 첨가하면 생산이 현저히 저해되는 것으로 보아 B. cereus 1-1 균의 ALA 생산은 C-5 경로에 의함을 알 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제20권10호
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• pp.1177-1180
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• 1999

The ab initio SCF MO and density functional theory (DFT) studies are carried out on the electrophilic (1a) and electron transfer (1b) addition reactions to the vinyl double bond of aryl vinyl sulfides and ethers. In the electrophilic addition processes, a double bond shift from C3 = C4 to X = C3 occurs with occupation number (1.97) close to the normal two. Due to this shift direct conjugation between the cationic center, X = S or O, and the para electron-donor substituent becomes impossible so that the reaction energies (or log K) are correlated with σ rather than σ+. By contrast, radical cation formation leads to delocalization of the SOMO, a lone-pair πorbital on X, with four major resonance structures in which cationic charge as well as spin density is delocalized over C4 , X and C7 atoms. As a result, partial πbonds are formed over C1 -X and C3 - C4 with occupation numbers (0.82) lower than one. In two of the cannonical structures, III(Ⅹ) and III(X+), direct conjugation between the cationic center, X, and the para substituent is achieved so that a better correlation with σ+ rather than σis obtained. The SCF MO energies at the HF/3-21G* and HF/6-31G* levels lead to very much inferior Hammett correlations in the σ/ σ+ diagnostic criterion. In contrast, the ρvalues evaluated with the DFT energies can give reliable diagnostic distinction between the two addition mechanisms.

• 한국세라믹학회지
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• 제34권8호
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• pp.811-816
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• 1997

SiO2-P2O5-B2O3 glass soot was fabricated by flame hydrolysis deposition and their properties by SEM, XRD, TGA-DSC were investigated., The mechanism of consolidation process of a glass soot as a function of consolidation temperature was analyzed by SEM observations. In the XRD patterns, the crystalline peaks which seem to be generated from B2O3 and BPO4 were observed. When the temperature of heat treatment exceeded 105$0^{\circ}C$, the non-crystalline state of SiO2-P2O5-B2O3 glass was observed. In the TGA-DSC curves, the evaporation of water molecule by a sudden endothermic reaction was observed at 128$^{\circ}C$ and a broad endothermic peak was seen in the temperature range of 40$0^{\circ}C$-95$0^{\circ}C$, without any weight loss. Finally, this peak was began to recover its baseline at 953$^{\circ}C$. This point is equal to the temperature at which the densification begins. Furthermore, we observed that the addition of dopants such as P2O5 and B2O3 decrease the onset of consolidation temperature till 95$0^{\circ}C$.