• Bulletin of the Korean Chemical Society
• /
• 제33권6호
• /
• pp.1934-1938
• /
• 2012

The reaction mechanism between cyclopropenylidene and formaldehyde has been systematically investigated employing the MP2/6-311+$G^*$ level of theory to better understand the cyclopropenylidene reactivity with carbonyl compound. Geometry optimization, vibrational analysis, and energy property for the involved stationary points on the potential energy surface have been calculated. Energies of all the species are further corrected by the CCSD(T)/6-311+$G^*$ single-point calculations. It was found that one important reaction intermediate (INTa) has been located firstly $via$ a transition state (TSa). After that, the common intermediate (INTb) for the two pathways (1) and (2) has been formed $via$ TSb. At last, two different products possessing three- and four-membered ring characters have been obtained through two possible reaction pathways. In the reaction pathway (1), a three-membered ring alkyne compound has been obtained. As for the reaction pathway (2), it is the formation of the four-membered ring conjugated diene compound. The energy barrier of the ratedetermining step of pathway (1) is lower than that of the pathway (2), and the ultima product of pathway (2) is more stable than that of the pathway (1).

• 공업화학
• /
• 제18권3호
• /
• pp.234-238
• /
• 2007

기능성 도핑제인 혼합 도판트[sodium di(2-ethylhexyl)sulfosuccinate(DEHSNa) Naphthalenesulfonic acid (NSA), DEHSNa Toluensulfonic acid (TSA), DEHSNa Dodecylbenzensulfonic acid (DBSA)], 혼합 산화제[$(NH_4)_2S_2O_8{\cdot}FeCl_3$, $(NH_4)_2S_2O_8{\cdot}Fe_2(SO_4)_3$]을 사용하여 높은 전기전도도를 갖는 유기용매에 가용성인 폴리피롤을 합성하였다. 산화제로 $(NH_4)_2S_2O_8$ (10wt%/vol.)을 사용한 Ppy-DEHS 분말은 혼합 도판트(DEHSNa NSA, 3 wt%/vol.)와 혼합 산화제[$(NH_4)_2S_2O_8{\cdot}Fe_2(SO_4)_3$, 4 wt%/vol.]을 사용한 경우보다 극성 용매(DMF)에서 높은 용해도를 나타내었다. 그러나, DMF 용매에서 제조된 혼합 도판트[DEHSNa NSA, 16 S/cm]와 혼합 산화제[$(NH_4)_2S_2O_8{\cdot}FeCl_3$, 13 S/cm]을 사용한 Ppy-DEHS 필름의 전기전도도는 $(NH_4)_2S_2O_8$ (2 S/cm)을 사용한 경우보다 더 높게 나타났다. 다양한 조건에서 제조된 Ppy-DEHS 필름의 전하전달은 모두 3차원 VRH mode{$\{{\sigma}_{dc}(T)={\sigma}_oexp[-(T_o/T)^{1/4}]\}$에 부합하였다.

• 대한화학회지
• /
• 제31권4호
• /
• pp.308-314
• /
• 1987

중금속 이온의 흡착, 분리 및 회수에 적합한 킬레이트제 침윤수지의 조건을 조사하기 위하여 cupferron (CP), diphenylcarbazone (DPC), salicylaldoxime (SAO), thiosalicylic acid (TSA), 및 dimethylglyoxime (DMG)등의 킬레이트제를 선택하여 Amberite XAD-7 수지에 대한 흡착성을 조사하였다. 킬레이트제-XAD-7 침윤수지들을 만들고, 각 침윤수지들에 대한 Cu(Ⅱ) 이온의 흡착, 분리 및 회수능을 비교하였다. Cu(Ⅱ) 이온에 대해서 적절한 침윤수지로는 비교적 넓은 pH 영역에서 킬레이트제의 흡착이 안정하고 Cu(Ⅱ)와 넓은 pH 범위에서 정량적인 흡착을 보이는 SAO-XAD-7과 DMG-XAD-7 침윤수지임을 알았다. SAO-XAD-7 수지를 사용하여 Cu(Ⅱ) 이온을 공존하는 Ni(Ⅱ) 이온으로부터 분리하였다. Cu(Ⅱ)이온의 최적흡착량은 SAO-XAD-7 침윤수지의 경우는 수지 1g에 대해서 $7{\times}10^{-3}mmol$이며, DMG-XAD-7의 경우는 $2{\times}10^{-3}mmol$이다. 또한 흡착된 Cu(Ⅱ)이온. 1N HCl로 용출시켜 정량적으로 회수하였다. 한편 혼합 침윤수지에서의 Cu(Ⅱ)와 Ni(Ⅱ) 이온의 선택적 흡착성을 조사하였다.

• Asian Pacific Journal of Cancer Prevention
• /
• 제14권12호
• /
• pp.7529-7536
• /
• 2013

Background and Aims: MicroRNA-21 (miR-21) is reported to be overexpressed and to contribute to proliferation, apoptosis and gemcitabine resistance in pancreatic ductal adenocarcinomas (PDACs). The aims of this study were to explore regulation of miR-21 expression by epigenetic change and its impact on chemoresistance and malignant properties of of pancreatic cancer. Materials and methods: We retrospectively collected 41 cases of advanced pancreatic cancer patients who were sensitive or resistant to gemcitabine and assessed levels of serum circulating miR-21 for correlation with cytotoxic activity. Histone acetylation in the miR-21 promoter was also studied in gemcitabine-sensitive and gemcitabine-resistant PDAC cells. Gemcitabine-resistant HPAC and PANC-1 cells were transfected with pre-miR-21 precursors (pre-miR-21) and antisense oligonucleotides (anti-miR-21), and were treated with TSA. Finally, invasion and metastasis assays were performed and alteration in mir-21, PTEN, AKT and pAKT level was evaluated in these cells. Results: Serum miR-21 levels were increased in gemcitabine-resistant PDAC patients compared with gemcitabine-sensitive subjects. The miR-21 levels were increased in 6 PDAC cells treated with gemcitabine significantly, associated with 50% inhibitory concentrations ($IC_{50}s$). Histone acetylation levels at miR-21 promoter were increased in PDAC cells after treatment with gemcitabine. Enhanced invasion and metastasis, increased miR-21 expression, decreased PTEN, elevated pAKT level were demonstrated in gemcitabine-resistant HPAC and PANC-1 cells. Pre-miR-21 transfection or TSA treatment further increased invasion and metastasis ability, decreased PTEN, and elevated pAKT levels in these two lines. In contrast, anti-miR-21 transfection could reverse invasion and metastasis, and PTEN and pAKT expressions induced by gemcitabine. Conclusions: MiR-21 upregulation induced by histone acetylation in the promoter zone is associated with chemoresistance to gemcitabine and enhanced malignant potential in pancreatic cancer cells.

• 공업화학
• /
• 제28권3호
• /
• pp.332-338
• /
• 2017

본 연구에서는 주요한 휘발성 유기화합물의 발생원인 도장공장 중에서 중소규모의 공장에 적용 가능한 저온 vacuum swing adsorption (VSA) 기술에 대하여 연구하였다. 저온 VSA 기술이란 기존의 thermal swing adsorption (TSA)의 단점을 보완하기 위하여 저온($60{\sim}90^{\circ}C$)에서 감압하여 흡착질을 탈착하는 방식이다. 국내에서 시판되고 있는 상용 활성탄을 이용하여 대표적인 VOCs인 톨루엔의 흡 탈착 특성을 랩(Lab)규모로 실험하였으며, 이를 바탕으로 $30m^3min^{-1}$ 규모의 VSA 시스템을 설계하여 실제 도장 공장에 적용하여 VSA 시스템의 현장적용 가능성에 대하여 평가하였다. 랩 규모 실험 결과, 2 mm 펠렛형 활성탄은 4 mm 펠렛형 활성탄보다 높은 톨루엔 흡착능을 나타내었으며, 이에 파일럿 규모의 VSA의 충진 활성탄으로 사용되었다. 탈착 실험에서는 $80{\sim}90^{\circ}C$의 온도와 100 torr의 압력이 최적 조건으로 결정되었다. 랩 규모 실험 결과를 바탕으로 파일럿 규모 VSA 시스템을 설계하였으며 실제 도장 공장에 현장 적용하여 95회 흡 탈착 실험을 반복 수행하였다. 수행 결과, 연속 흡 탈착 반복실험 후, 도정공장에서 배출된 VOCs를 98% 이상 효과적으로 제거 가능함을 확인하였으며 VSA 시스템의 안정적인 현장 적용이 가능함을 검증하였다.

• 한국식물병리학회:학술대회논문집
• /
• 한국식물병리학회 2003년도 정기총회 및 추계학술발표회
• /
• pp.102.1-102
• /
• 2003

A bacterial strain YC4963 with antifungal activity against Colletotrichum orbiculare, a causal organism of cucumber anthracnose was isolated from the rhizosphere soil of Siegesbeckia pubescens (Siegesbeckia pubescens Makino；Family：Compositae) in Korea. Based on physiological and biochemical characteristics and 16S ribosomal DNA sequence analysis, the bacterial strain was identified as Pseudomonu aureofaciens. The bacteria also inhibited mycelial growth of several plant fungal pathogens such as Botrytis cinerea, Fusarium oxysporum and Rhizoctonia solani on PDA and 0.1 TSA media. The antibiotic activity was found from the culture filtrate of TSB(tryptic soy broth) and its active compounds were quantitatively bound to XAD adsorber resin. The antibiotic spectrum was broad and growth of C. orbiculare and F. oxysporum, B. cinerea were inhibited at very low concentration. The chemical data from various chromatographic procedures showed that active fraction consisted of at least two phenazine derivatives. However, the metabolites had no inhibitory effect on Pythium ultimum which was reported to be sensitive to phenazine antibiotics. The compounds responsible for the activity are now under investigation.

• Macromolecular Research
• /
• 제10권2호
• /
• pp.122-126
• /
• 2002

A molecularly imprinted polymer (MIP) having both amidine and imidazole functional groups in the active site has been prepared using p-nitrophenyl phosphate as a transition state analogue (TSA). The imprinted polymer MIP with amidine and imidazole found to have the highest hydrolysis activity compared with other MIPs with either amidine or imidazole groups only. It is postulated a cooperative effect between amidine and imidazole in the hydrolysis of p-nitrophenyl methyl carbonate (NPMC) as a substrate when both groups were arranged in proximity by molecular imprinting. The rate enhancement of the hydrolysis by MIP was 60 folds over the uncatalyzed solution reaction and two folds compared with the control non-imprinted polymer CPI having both functional groups. The enzyme-mimetic catalytic hydrolysis of p-nitrophenyl acetate by MIP was evaluated in buffer at pH 7.0 with $K_{m}$ of 1.06 mM and $k_{cat}$ of 0.137 $h^{-1}$ . . .

• Journal of Korean Neurosurgical Society
• /
• 제49권6호
• /
• pp.339-344
• /
• 2011

Objective : Pituitary apoplexy is one of the most serious life-threatening complications of pituitary adenoma. The purpose of this study is to investigate the visual outcome after early transsphenoidal surgery for the patients with pituitary apoplexy. Methods : We retrospectively reviewed the 31 patients with pituitary apoplexy who were admitted due to acute visual acuity or field impairment and treated by transsphenoidal surgery. Five patients were excluded because of the decreased conscious level. The visual acuity of each individual eye was evaluated by Snellen's chart Visual fields were also checked using automated perimetry. To compare the visual outcome according to the surgical timing, we divided the patients into 2 groups. The first group, 21 of the patients have been undertaken transsphenoidal approach (TSA) within at least 48 hours after admission. The second group included 8 patients who have been undertaken TSA beyond 48 hours. All patients were monitored at least 12 months after surgery. Results : Patients were 21 males and 8 females (M : F=2.6 : 1) with the mean age of 42.4 years. Among the enrolled 29 patients, 26 patients presented with decreased visual acuity and 23 patients revealed the defective visual field respectively. Postoperatively, improvement in the visual acuity was seen in 15 patients (83.3%) who underwent surgery within the first 48 hours of presentation, as compared to those in whom surgery was delayed beyond 48 hours (n=5; 62.5%) (p=0.014). Improvement in the visual field deficits was observed in 15 (88.2%) of patients who had been operated on within the first 48 hours of presentation, as compared to those in whom surgery was delayed beyond 48 hours (n=3; 50.0%) (p=0.037). Conclusion : This study suggests that rapid transsphenoidal surgery is effective to recover the visual impairment in patients with pituitary apoplexy. If there are associated abnormalities of visual acuity or visual fields in patients with hemorrhagic pituitary apoplexy, early neurosurgical intervention within 48 hours should be also required to recover visual impairment.

• KIEE International Transactions on Power Engineering
• /
• 제2A권4호
• /
• pp.131-135
• /
• 2002

This paper describes a new ultra-fast contingency screening algorithm for on-line TSA without time simulation. All machines are represented in a classical model and the stability index is defined as the ratio between acceleration power during a fault and deceleration power after clearing the fault. Critical clustering of machines is done based on the stability index, and the power-angle curve of the critical machines is drawn assuming that the angles of the critical machines increase uniformly, while those of the non-critical ones remain constant. Finally, the critical clearing time (CCT) is computed using the power-angle curve. The proposed algorithm is tested on the KEPCO system comprised of 900-bus and 230-machines. The CCT values computed with the screening algorithm are in good agreement with those computed using the detailed model and the SIME method. The computation time for screening about 270 contingencies is 17 seconds with 1.2 GHz PC.

• Journal of Astronomy and Space Sciences
• /
• 제38권2호
• /
• pp.119-134
• /
• 2021

The data set collected during the night of the discovery of a minor body constitutes a too-short arc (TSA), resulting in failure of the differential correction procedure. This makes it necessary to recover the object during subsequent nights to gather more observations that will allow a preliminary orbit to be calculated. In this work, we present a recovery technique based on sampling the admissible region (AdRe) by the constrained Delaunay triangulation. We construct the AdRe in its topocentric and geocentric variants, using logarithmic and exponential metrics, for the following near-Earth-asteroids: (3122) Florence, (3200) Phaethon, 2003 GW, (1864) Daedalus, 2003 BH84 and 1977 QQ5; and the main-belt asteroids: (1738) Oosterhoff, (4690) Strasbourg, (555) Norma, 2006 SO375, 2003 GE55 and (32811) Apisaon. Using our sampling technique, we established the ephemeris region for these objects, using intervals of observation from 25 minutes up to 2 hours, with propagation times from 1 up to 47 days. All these objects were recoverable in a field of vision of 95' × 72', except for (3122) Florence and (3200) Phaethon, since they were observed during their closest approach to the Earth. In the case of 2006 SO375, we performed an additional test with only two observations separated by 2 minutes, achieving a recovery of up to 28 days after its discovery, which demonstrates the potential of our technique.