• Bulletin of the Korean Chemical Society
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• 제32권1호
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• pp.277-280
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• 2011

We studied the relative stability and atomic structure of five $C_{20}^{2+}$ isomers obtained by two-electron ionization of a $C_{20}$ cage (the smallest fullerene). All the isomers are bond-stretch isomers, i.e., they differ in bond length. In particular, in one of the isomers with Ih symmetry, all the bond lengths are equal. Full geometry optimizations of the dipositive ion $C_{20}^{2+}$ were performed using the hybrid density functional (B3LYP/6-31G(d)) methods. All isomers were found to be true minima by frequency analysis at the level of B3LYP/6-31G(d) under the reinforced tight convergence criterion and a pruned (99,590) grid. The zero-point correction energy for the cage bond-stretch isomers was in the increasing order $D_{2h}<C_{2h}<C_2<T_h<I_h$ of $C_{20}^{2+}$. The energy difference among the isomers of cage dipositive ions was less than that among neutral cage isomers. Our results suggest that these isomers show bond-stretch isomerism and that they have an identical spin state and an identical potential energy curve. Although the predominant electronic configurations of the isomers are similar, the frontier orbital characteristics are different, implying that we could anticipate an entirely different set of characteristic chemical reactions for each type of HOMO and LUMO.

• 통합자연과학논문집
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• 제16권4호
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• pp.123-131
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• 2023

Breast cancer continues to pose a substantial worldwide health challenge, thereby requiring the development of innovative strategies to discover new therapeutic interventions. Signal Transducer and Activator of Transcription 3 (STAT-3) has been identified as a significant factor in the development of several types of cancer, including breast cancer. This is primarily attributed to its diverse functions in promoting tumour formation and conferring resistance to therapeutic interventions. This study presents an in silico drug repositioning approach that focuses on identifying specific inhibitors of STAT-3 for the purpose of treating breast cancer. We initially examined the structural and functional attributes of STAT-3, thereby elucidating its crucial involvement in cellular signalling cascades. A comprehensive virtual screening was performed on a diverse collection of drugs that have been approved by the FDA from zinc15 database. Various computational techniques, including molecular docking, cross docking, and cDFT analysis, were utilised in order to prioritise potential candidates. This prioritisation was based on their predicted binding energies and outer molecular orbital reactivity. The findings of our study have unveiled a Dihydroergotamine and Paritaprevir that have been approved by the FDA and exhibit considerable promise as selective inhibitors of STAT-3. In conclusion, the utilisation of our in silico drug repositioning approach presents a prompt and economically efficient method for the identification of potential compounds that warrant subsequent experimental validation as selective STAT-3 inhibitors in the context of breast cancer. The present study highlights the considerable potential of employing computational strategies to expedite the drug discovery process. Moreover, it provides valuable insights into novel avenues for targeted therapeutic interventions in the context of breast cancer treatment.

• 대한화학회지
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• 제32권5호
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• pp.476-482
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• 1988

$Hg^{2+}$ 수용액내에서 cis-[$Co(en)_2YCl$]$^{r+}$ (Y = $NH_3$, $NO_2^-$, NCS$^-$, $H_2O$)의 아쿠아 반응속도를 UV/vis 분광광도계로 측정하여 반응속도식을 결정하였으며, 확장분자궤도법(Extended Huckel Molecular Orbital Method)에 의해 Co(Ⅲ) 전이금속착물의 양자화학적값을 계산하고 실험에서 구한 반응속도와의 상관성을 조사하여 촉매가 관련한 타당한 반응메카니즘을 제안하였다. 본 연구에서 Co(Ⅲ) 전이금속착물과 $Hg^{2+}$에 대하여 각각 1차반응이고, 반응속도는 Co(Ⅲ) 중심금속의 알짜전하 크기와 병행성이 있으며, 이들의 반응속도는 Y의 종류에 따라 $NH_3$ < NCS$^-$ < H$_2$O < NO$_2^-$의 순으로 증가되었다. 그리고 이들 생성물의 cis-이성질체가 약 95${\%}$, trans-이성질체가 약 5${\%}$정도 생성되었다. 또한 EHMO법에 의해 계산된 알짜전하와 결합차수로부터 본 반응계는 결합깨어짐보다 결합형성이 우선되어 H$_2$0가 Co(Ⅲ) 중심금속에 공격하는 단계가 속도결정 단계가 됨을 알았다. 이러한 사실과 실험에서 구한 속도자료 그리고 활성화파라메타값으로부터 Id 메카니즘으로 진행되는 타당한 반응메카니즘을 제안하였다.

• 대한화학회지
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• 제18권2호
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• pp.85-96
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• 1974

$C_6H_5YCH_2Cl$(Y=None, -$CH_2$-,-O-,-S-,-CO-,-$SO_2$-)에 대하여 EHT및 CNDO/2 MO계산을 행하고 이에 bond index 해석법을 적용하여, 분자내의 하전분포는 주로 원자가 비활성 전자의 이동에 기인되며, -O->-S->-$CH_2$-$SO_2$-의 순서로 ${\sigma}$-전자받게의 특성과 ${\pi}$-전자주게의 특성을 나타내며 -CO-는 ${\sigma}$-전자주게, ${\pi}$-전자받게로 작용함을 밝혔다. 또한 $C_6H_5YCH_2Cl$의 $S_N2$반응성이 현저한 용매효과가 없을 때 -O-${\thickapprox}$-CO->>-S-${\thickapprox}$None>-$CH_2$-의 순일 것으로 제안하였으며 실험 사실과 거의 일치함을 알았다. 이로부터 $S_N$형 반응에 크게 영향을 미치는 효과는 용매효과를 제안하였으며 실험 사실과 거의 일치함을 알았다. 이로 부터 SN형 반응에 크게 영향을 미치는 효과는 용매효과를 제외하면 반응중심의 양(+)하전 크기, C-Cl 결합에 대하여 ${\sigma}$-반결합성인 비점유궤도함수의 에너지 및 그 준위에서의 C-Cl간 반결합성이 경쟁적으로 작용할 것임을 밝혔다.

• 대한화학회지
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• 제17권2호
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• pp.95-104
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• 1973

일련의 염화알킬(염화메틸, 에틸, 이소-프로필, 트란스 n-부틸, sec-부틸, tert-부틸)의 바닥 상태 전자구조와 친핵성 치환반응성을 근사적 시그마 분자궤도법$(\sigma-MO)$인 EHT 와 CNDO/2 법을 이용하여 비교 검토하였다. 염화알킬처럼 상호 구조적 차이가 현저하지 못한 경우에 있어서는 EHT법이 CNDO/2 법에 비하여 비교적 부정확함을 알았다. CNDO/2 계산에 의하면, 쌍극자모멘트의 계산치가 실험치 보다 약간 크게 주어지며 대체로 primary$\alpha$탄소와 Cl사이에 비교적 약한 $\pi$-반결합 $({\pi}^{\ast})$성을 가지고 있으며, 전자밀도가 거의 염소원자에 집중되어 있어 염소의 p-고립상 전자와 같은 특성을 가지고 있음을 알았다. 그 반면 최저 비점유 궤도함수(LUMO)는$\alpha$탄소와 염소 사이에 강한 시그마-반결합$({\alpha}^{\ast})$성을 가짐을 알았다. 염화알킬의 $S_N2$반응성은 주로 $\alpha$인 LUMO에의하여 좌우되며, 특히 이 MO에서 $\alpha$탄소와 염소간의 반결합 세기가 $S_N2$반응성의 척도가 될 것으로 예측되며, 결합-polorizability와의 관련성도 논의하였다. 염화알킬의 $S_N2$반응성은 주로 ${\pi}^{\ast}$인 HOMO에서 $\alpha$탄소와 염소간의 반결합 세기가 큰 역할을 하며 바닥상태의 C-Cl결합세기도 상당한 역할을 할 것으로 기대된다.

• Journal of Positioning, Navigation, and Timing
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• 제4권2호
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• pp.43-55
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• 2015

In the case of satellite navigation positioning, the shielding of satellite signals is determined by the environment of the region at which a user is located, and the navigation performance is determined accordingly. The accuracy of user position determination varies depending on the dilution of precision (DOP) which is a measuring index for the geometric characteristics of visible satellites; and if the minimum visible satellites are not secured, position determination is impossible. Currently, the GLObal NAvigation Satellite system (GLONASS) of Russia is used to supplement the navigation performance of the Global Positioning System (GPS) in regions where GPS cannot be used. In addition, the European Satellite Navigation System (Galileo) of the European Union, the Chinese Satellite Navigation System (BeiDou) of China, the Quasi-Zenith Satellite System (QZSS) of Japan, and the Indian Regional Navigation Satellite System (IRNSS) of India are aimed to achieve the full operational capability (FOC) operation of the navigation system. Thus, the number of satellites available for navigation would rapidly increase, particularly in the Asian region; and when integrated navigation is performed, the improvement of navigation performance is expected to be much larger than that in other regions. To secure a stable and prompt position solution, GPS-GLONASS integrated navigation is generally performed at present. However, as available satellite navigation systems have been diversified, finding the minimum satellite constellation combination to obtain the best navigation performance has recently become an issue. For this purpose, it is necessary to examine and predict the navigation performance that could be obtained by the addition of the third satellite navigation system in addition to GPS-GLONASS. In this study, the current status of the integrated navigation performance for various satellite constellation combinations was analyzed based on 2014, and the navigation performance in 2020 was predicted based on the FOC plan of the satellite navigation system for each country. For this prediction, the orbital elements and nominal almanac data of satellite navigation systems that can be observed in the Korean Peninsula were organized, and the minimum elevation angle expecting signal shielding was established based on Matlab and the performance was predicted in terms of DOP. In the case of integrated navigation, a time offset determination algorithm needs to be considered in order to estimate the clock error between navigation systems, and it was analyzed using two kinds of methods: a satellite navigation message based estimation method and a receiver based method where a user directly performs estimation. This simulation is expected to be used as an index for the establishment of the minimum satellite constellation for obtaining the best navigation performance.

• Bulletin of the Korean Chemical Society
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• 제24권6호
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• pp.864-880
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• 2003

A unified picture for magnetism, superconductivity, quantum optics and other properties of molecule-based materials has been presented on the basis of effective model Hamiltonians, where necessary parameter values have been determined by the first principle calculations of cluster models and/or band models. These properties of the matetials are qualitatively discussed on the basis of the spin and pseudo-spin Hamiltonian models, where several quantum operators are expressed by spin variables under the two level approximation. As an example, ab initio broken-symmetry DFT calculations are performed for cyclic magnetic ring constructed of 34 hydrogen atoms in order to obtain effective exchange integrals in the spin Hamiltonian model. The natural orbital analysis of the DFT solution was performed to obtain symmetry-adapted molecular orbitals and their occupation numbers. Several chemical indices such as information entropy and unpaired electron density were calculated on the basis of the occupation numbers to elucidate the spin and pair correlations, and bonding characteristic (kinetic correlation) of this mesoscopic magnetic ring. Both classical and quantum effects for spin alignments and singlet spin-pair formations are discussed on the basis of the true spin Hamiltonian model in detail. Quantum effects are also discussed in the case of superconductivity, atom optics and quantum optics based on the pseudo spin Hamiltonian models. The coherent and squeezed states of spins, atoms and quantum field are discussed to obtain a unified picture for correlation, coherence and decoherence in future materials. Implications of theoretical results are examined in relation to recent experiments on molecule-based materials and molecular design of future molecular soft materials in the intersection area between molecular and biomolecular materials.

• 항공우주정책ㆍ법학회지
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• 제32권1호
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• pp.385-417
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• 2017

Insurances of space activities are divided into satellite insurance, astronaut insurance and third party liability insurance. Against the background of the rapid development of space commercialization, especially the increasing participation of private entities in space affairs, the present international and domestic mechanisms of space insurance are challenged. As a space-faring state which is in the process of developing space businesses, the regulations of space insurance in China are deserved to be discussed. Satellites insurance is at present well-developed, the "pre-launch", "launch" and "in-orbit" phases of satellites are all possible to be insured by related companies. China created the CAIA in 1997 to provide insurance for Chinese satellites. However, with more private entities start to involve in space as well as satellite industry, the regime established under the framework of CAIA is necessary to be modified, and the mechanism relating to space insurance brokers should be promoted. The astronauts are recognized as the envoy of humankind, and relevant international regulations are made to provide assistance to them in emergency circumstances. From the domestic perspective, astronauts will be fully insured. China creates a particular type of insurance for astronauts. However, once space tourism becomes a business, the insurance of the tourist will be demanded to be created. In order to promote China's space tourism, it is recommended to take the "Astronaut Group Insurance" as an optional model to space tourists, if the tourists are customers of a governmental-owned space company. Once private involvement of providing orbital/suborbital tourism service becomes a reality, new rules are required. Getting a third party liability insurance is deemed as an indispensable precondition for an applicant to get a launch permission. Domestic space laws will include provisions for the third party liability insurance. China's "Interim Measures" of 2002 realizes the importance of third party liability insurance and requires the permit holder to get it before entering the launching site. This regulation is different from the practices of other states. Concerning that China is the sponsor of APSCO, for the purpose of promoting commercial space cooperation, a harmonized approach to domestic law is recommended to be found.

• Archives of Plastic Surgery
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• 제41권6호
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• pp.679-685
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• 2014

Background Frontal sinus fractures, particularly anterior sinus fractures, are relatively common facial fractures. Many agree on the general principles of frontal fracture management; however, the optimal methods of reduction are still controversial. In this article, we suggest a simple reduction method using a subbrow incision as a treatment for isolated anterior sinus fractures. Methods Between March 2011 and March 2014, 13 patients with isolated frontal sinus fractures were treated by open reduction and internal fixation through a subbrow incision. The subbrow incision line was designed to be precisely at the lower margin of the brow in order to obtain an inconspicuous scar. A periosteal incision was made at 3 mm above the superior orbital rim. The fracture site of the frontal bone was reduced, and bone fixation was performed using an absorbable plate and screws. Results Contour deformities were completely restored in all patients, and all patients were satisfied with the results. Scars were barely visible in the long-term follow-up. No complications related to the procedure, such as infection, uncontrolled sinus bleeding, hematoma, paresthesia, mucocele, or posterior wall and brain injury were observed. Conclusions The subbrow approach allowed for an accurate reduction and internal fixation of the fractures in the anterior table of the frontal sinus by providing a direct visualization of the fracture. Considering the surgical success of the reduction and the rigid fixation, patient satisfaction, and aesthetic problems, this transcutaneous approach through a subbrow incision is concluded to be superior to the other reduction techniques used in the case of an anterior table frontal sinus fracture.

• 한국지하수토양환경학회지:지하수토양환경
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• 제9권2호
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• pp.20-27
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• 2004

수용액상에서 철광물질과 유기 용매간의 반응 속도는 여러 반응인자에 따라 반응 속도 실험을 하였다 F $e^{0}$ , FeS와 Fe $S_2$를 반응 매개물로 $C_2$C $l_{6}$에 대한 반응에서 F $e^{0}$ ＞ FeS ＞ Fe $S_2$ 순으로 분해반응 속도가 빠르게 나타났다. 철 광물질에 대해서 $C_2$C $l_{6}$, CHC $l_{5}$ , $C_2$C $l_4$, CHC $l_3$에 대한 분해 반응 속도는 염소 치환기가 적을수록 환원반응 속도는 느리게 일어난다. 환원 반응 속도는 pH, 교반 속도, 반응 온도와 비표면적에 의존적임을 확인하였다. 1,10-phenanthroline과 EDTA화합물은 고립전자 쌍을 가진 2개의 질소 원자에 의해 형성된 두 자리 킬레이트 작용기가 철 표면에 흡착하며 전자 이동 속도를 증가시켜 분해 반응 속도를 증가시킨다. 즉 분자 $\pi$＊ 오비탈을 가진 질소원자는 비어있는 금속에 비편재(delocalized)되어 전자이동 속도를 증가시킨다. 그리고 hydroquinone은 반응 속도에 영향을 주지 않았다. 자연계에 존재하는 카올리나이트는 철 광물질의 부식을 유발시켜 분해 반응속도를 증가시켰다. 반면 F $e^{2+}$와 S $O_4$$^{2-}$ 와 같은 이온은 반응속도에 영향을 주지 않았다.