• Bulletin of the Korean Chemical Society
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• 제30권3호
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• pp.683-686
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• 2009

Slurry phase reaction of elemental silicon with methanol has been studied in the presence of copper using a small amount of cuprous chloride as an activator in DBT (dibenzyltoluene) at various temperatures from 200 ${^{\circ}C}$ to 320 ${^{\circ}C}$. Trimethoxysilane (1a) with a Si-H unit was obtained as the major product and tetramethoxysilane (1b) as the minor product. The reaction worked well using a 0.5 wt % CuCl as an activator. The optimum temperature for this direct synthesis of 1a was 240 ${^{\circ}C}$. Methoxysilanes were obtained in 95% yield with 81% selectivity to 1a from 85% conversion of elemental silicon.

• Bulletin of the Korean Chemical Society
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• 제3권2호
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• pp.70-76
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• 1982

Synthetic utility of 1-fluoro-2,4,6-trinitrobenzene (FTNB) as a condensing agent was investigated. The use of FTNB and DMAP was found to be very effective for direct esterification of carboxylic acids with alcohols or thiols. However, this system was not very effective for macrolactonization. Reaction of 2,4,6-trinitrophenyl esters with several nucleophiles was investigated briefly. Plausible reaction mechanisms of esterification are presented. It seems that the reaction proceeds via the intermediacy of 2,4,6-trinitrophenyl esters by initial formation of 2',4',6'-trinitrophenyl-4-dimethylaminopyridinium salt from which the trinitrophenyl group is transferred to the carboxylic acid.

• Bulletin of the Korean Chemical Society
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• 제34권5호
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• pp.1575-1578
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• 2013

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제26권1호
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• pp.45-52
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• 2000

Nowadays, there are a lot of evidence that mutation of the p53 tumor suppressor gene is one of the most common genetic abnormalities in neoplastic progression. In this study, we analyzed 20 specimens of oral tumors(squamous cell carcinoma 14 cases, ameloblastoma 3 cases, adenoid cystic carcinoma 2 cases, malignant schwannoma 1 case)using polymerase chain reaction and direct sequencing which used an automated DNA sequencer and software for detection of mutations. Polymerase chain reactions were performed with 4 sets of primers encompassing exon 5, 6, 7, 8, and direct sequencing method was employed. The results were as followings. 1. We detected 10 point mutations out of 20 specimens (50%). 2. The genetic alterations included 7 mis-sense mutations resulting in single amino acid subtitutions, 2 silent mutations, 1 non-sense mutations encoding a stop codon. 3. Mutations were mostly in exon 7(7 out of 10 mutations, 70%) and involved codons 225, 234, 235, 236, 238, 247. 4. Therse were 4 cases of $T{\rightarrow}A$ transversion, 2 cases of $C{\rightarrow}A$ transversion, $A{\rightarrow}G$ transition, 1 case of $C{\rightarrow}G$, $T{\rightarrow}G$ transversion respectively. 5. We could find out point mutations more conveniently using PCR - Automated Direct Sequencing method.

• Bulletin of the Korean Chemical Society
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• 제32권4호
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• pp.1187-1194
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• 2011

The hydrogen abstraction reaction of $CF_3CH_2CHO$ + OH has been studied theoretically by dual-level direct dynamics method. Two stable conformers, trans- and cis-$CF_3CH_2CHO$, have been located, and there are four distinct OH hydrogen-abstraction channels from t-$CF_3CH_2CHO$ and two channels from c-$CF_3CH_2CHO$. The required potential energy surface information for the kinetic calculation was obtained at the MCG3-MPWB//M06-2X/aug-cc-pVDZ level. The rate constants, which were calculated using improved canonical transitionstate theory with small-curvature tunneling correction (ICVT/SCT) were fitted by a four-parameter Arrhenius equation. It is shown that the reaction proceeds predominantly via the H-abstraction from the -CHO group over the temperature range 200-2000 K. The calculated rate constants were in good agreement with the experimental data between 263 and 358 K.

• 한국대기환경학회지
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• 제24권3호
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• pp.357-366
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• 2008

In this study, the analytical performance of trimethylamine (TMA) were investigated with respect to headspace-solid phase microextraction (HS-SPME) method. In order to induce the elution of aqueous TMA to headspace, NaOH was added as a decomposition reagent to aqueous TMA standard. By controlling the combination of three major variables for TMA extraction, the extent of extraction was compared between the two contrasting conditions for each variable (i.e., reaction time (long (L) vs short (S)), exposure temperature (30 vs $50^{\circ}C$), and exposure time (10 vs 30 min)). The results of this comparative analysis showed that the extraction efficiency for all eight types of HS-SPME combinations decreased on the order: L-30-30>L-50-10>L-30-10>L-50-30>S-30-30>S-50-30>S-50-10>S-30-10. The effect of reaction time appeared to exert significant influences on the relative recovery rate of HS-SPME at 90% confidence level. However, the effects of exposure temperature or exposure time were not so significant as reaction time. When the recovery rate of HS-SPME is compared against the direct injection of liquid standard into GC injector, it recorded as 2%. According to this comparative study, the reaction conditions for HS-SPME application can exert significant influences on the analysis of TMA.

• 한국수소및신에너지학회논문집
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• 제32권6호
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• pp.514-523
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• 2021

This study investigated the effect of anode fuel composition on the performance of direct borohydride/hydrogen peroxide fuel cells (DBHPFCs). The effect of sodium borohydride (NaBH₄) and sodium hydroxide (NaOH) concentrations on fuel cell performance was determined through fuel cell tests. Fuel cell performance increased with an increase in the NaBH₄ concentration, whereas it decreased with an increase in the NaOH concentration. The anode fuel composition was selected as 10 wt% NaBH₄+10 wt% NaOH+80 wt% H₂O based on the fuel viscosity, electrochemical reaction rate, and decomposition reaction rate. DBHPFCs were also tested to analyze the effect of operating temperature and operation time on fuel cell performance. The present results can be used as a reference basis to determine operating conditions of DBHPFCs.

• 에너지공학
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• 제19권3호
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• pp.188-194
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• 2010

DCFC는 가스 터빈이나 엔진과 달리 탄소를 사용하여 전기화학반응을 통해 직접 전기를 생산하는 연료전지이며, 주요 특징으로 기존의 발전설비 보다 높은 효율과 낮은 배기 배출물을 발생한다. 본 연구에서는 간단한 열역학 평형 해석을 통해 CO와 $CO_2$가 이론 기전력에 미치는 영향을 확인하였으며, 2차원 CFD 해석 방법을 이용하여 온도에 따른 반응 생성물 변화를 살펴보았다. 그 결과, CO 생성 반응(Boudouard 반응)을 동시에 고려한 이론 기전력 값은 $CO_2$ 생성 반응만 고려한 값(약 1.02 V)보다 크며, 특히 온도가 증가할수록 그 값이 증가함을 보여주었다. 2차원 수치해석 결과를 통하여서 Boudouard 반응이 고온으로 갈수록 중요하며, 비활성 기체로 인하여 Boudouard 반응이 지연됨을 확인하였다.

• The Journal of Korean Physical Therapy
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• 제22권5호
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• pp.103-108
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• 2010

Purpose: The aim of this study is to investigate whether motor cortex excitability by transcranial direct current stimulation (tDCS) over primary motor cortex (M1) affects motor performance of serial reaction task. Methods: Cathodal, anodal and sham tDCS (1 mA) are applied over right M1 of 24 subjects for 30 minutes including 11minutes for task period time. We applied two electrodes at the same position to both an experimental group and a sham-controlled group, and we made 2 groups recognize to be applicated of stimulation. Flexion, extension of wrist and thumb flexion are carried out following colors of arrows on the monitor. Serial reaction time task was applied to confirm the difference of the reaction time between 2 groups. Results: Reaction time is decreased in both tDCS-group and Sham-controlled tDCS group, and the degree of reduction is much greater in the post-test than pre-test. Reduction of reaction time between groupsis statistically significant. Conclusion: We consider that anodal tDCS increased the cortical excitability of the underlying motor cortex and it can be helpful to modulate motor performance. It seems that tDCS is an effective modality to modulate brain function, and it will be great help to mediate strategy for the brain injury patients.

• Journal of Microbiology and Biotechnology
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• 제25권10호
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• pp.1742-1750
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• 2015

Human insulin is composed of 21 amino acids of an A-chain and 30 amino acids of a B-chain. This is the protein hormone that has the role of blood sugar control. When the recombinant human proinsulin is expressed in Escherichia coli, a serious problem is the formation of an inclusion body. Therefore, the inclusion body must be denatured and refolded under chaotropic agents and suitable reductants. In this study, H27R-proinsulin was refolded from the denatured form with β-mercaptoethanol and urea. The refolding reaction was completed after 15 h at $15^{\circ}C$, whereas the reaction at $25^{\circ}C$ was faster than that at $15^{\circ}C$. The refolding yield at $15^{\circ}C$ was 17% higher than that at $25^{\circ}C$. The refolding reaction could be carried out at a high protein concentration (2 g/l) using direct refolding without sulfonation. The most economical and optimal refolding condition for human preproinsulin was 1.5 g/l protein, 10 mM glycine buffer containing 0.6 M urea, pH 10.6, and 0.3 mM β-mercaptoethanol at $15^{\circ}C$ for 16 h. The maximum refolding yield was 74.8% at $15^{\circ}C$ with 1.5 g/l protein. Moreover, the refolded preproinsulin could be converted into normal mature insulin with two enzymes. The average amount of human insulin was 138.2 g from 200 L of fermentation broth after enzyme reaction with H27R-proinsulin. The direct refolding process for H27R-proinsulin was successfully set up without sulfonation. The step yields for refolding and enzyme reaction were comparatively high. Therefore, our refolding process for production of recombinant insulin may be beneficial to the large-scale production of other biologically active proteins.