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111.
Masashi Daido Yukio Kawashima Masanori Tachikawa 《Journal of computational chemistry》2013,34(28):2403-2411
The structure of Watson–Crick‐type adenine‐thymine and guanine‐cytosine pairs has been studied by hybrid Monte Carlo (HMC) and path integral hybrid Monte Carlo (PIHMC) simulations with the use of semiempirical PM6‐DH+ method in the gas phase. We elucidated the nuclear quantum effect and temperature dependency on the hydrogen‐bonded moiety of base pairs. It was shown that the contribution of nuclear quantum effect on the hydrogen‐bonded structure is significant not only at low temperature 150 K but also at temperature as high as 450 K. The relative position of hydrogen‐bonded proton between two heavy atoms and the nuclear quantum nature of the proton are also shown. Furthermore, we have applied principal component analysis to HMC and PIHMC simulations to analyze the nuclear quantum effect on intermolecular motions. We found that the ratio of Buckle mode (lowest vibrational mode from normal mode analysis) decreases due to the nuclear quantum effect, whereas that of Propeller mode (second lowest vibrational mode) increases. In addition, nonplanar structures of base pairs were found to become stable due to the nuclear quantum effect from two‐dimensional free energy landscape along Buckle and Propeller modes. © 2013 Wiley Periodicals, Inc. 相似文献
112.
Shiro Matsumoto Yasuyuki Sugiyama Seizou Sakata Takayoshi Hayashi 《Liquid crystals》2013,40(5):649-655
Polymers containing droplets of liquid crystal smaller than 100 nm, which have good transparency and easily form films, were prepared under various conditions to evaluate their potential as electro-optic materials for waveguide-type devices. By varying the liquid crystal concentration and the strength of the UV irradiation causing photo-induced phase separation of the droplets, we were able to control the droplet size and density. We have clarified how the birefringence generated in an applied electric field, switching speed, and optical loss of light propagating in the film depend on droplet size and density. Polymer materials having a large electro-optic effect (δn = 0.001 at 8 V μm-1), low propagation loss (~2.5 dB cm-1), and fast response time (~10 μs) have been developed. 相似文献
113.
Various types of crystalline cellulose consisting of group I (cell I, IIII, IVI) and group II (cell II, IIIII, IVII) prepared from cotton linter were adjusted for their degree of polymerization (DP) as starting materials. These celluloses were then treated by semi-flow hot-compressed water (HCW) at 230–270 °C/10 MPa/2–15 min to study their decomposition behaviors. The treatments performed resulted in residues of celluloses and water-soluble (WS) portions. Consequently, the crystallinity of the residues was found to remain the same, but the DP was reduced as the temperature increased. Additionally, X-ray diffractometry and Fourier transform-infrared analyses demonstrated that crystallographic changes occurred for residues of cell IIII, IVI and IIIII. Despite these changes, the overall results of the residues showed that group I has higher resistance to decomposing than group II. As for the WS portions, the yields of the hydrolyzed and degraded products were higher in group II than group I, indicating that group II is less resistant to decomposition by HCW treatment. Results for both the residues and WS portions are in agreement with each other, showing that the degree of difficulty of decomposition was higher in group I than group II. Therefore, the decomposition behaviors of the celluloses are due to differences in the crystalline forms. 相似文献
114.
Shiro Kubuki Koken Matsuda Kazuhiko Akiyama Tetsuaki Nishida 《Journal of Radioanalytical and Nuclear Chemistry》2014,299(1):453-459
A relationship between local structure, thermal stability and electrical conductivity (σ) of xR2O·10Fe2O3·(90 ? x)V2O5 glasses (abbreviated as xRFV glasses, where R = Li, Na, K; x = 20 and 40 in mol %) was investigated by 57Fe-Mössbauer spectroscopy, X-ray diffractometry, differential thermal analysis (DTA) and DC two- and four-probe method. From DTA study, thermal stability of 20RFV glasses is lower than that of 40RFV glasses by evaluating Hruby parameter (K gl). Constant activation energy for crystallization (E a) of 2.5 eV obtained from both 20RFV and 40RFV glasses indicate that the crystallization proceeds with the cleavage of Fe–O bond having the energy of 2.6 eV. Isochronally annealed 20RFV glass at 400–450 °C resulted in the increase in electrical conductivity (σ) from the order of 10?3 to 10?1 S cm?1, whereas slight decrease in σ was observed for 20RFV glass annealed above 460 °C. A paramagnetic doublet with an identical isomer shift (δ) of 0.39 mm s?1 was observed in the 57Fe-Mössbauer spectra of 20RFV glass after isothermal annealing conducted at 400–450 °C for 100 min, which caused a decrease of quadruple splitting (Δ) from 0.67 to 0.52 mm s?1 for 20LiFV glass and from 0.66 to 0.53 mm s?1 for 20NaFV glass. On the other hand, three paramagnetic doublets with δ and Δ of 0.40 and 0.25, 0.38 and 0.60, and 0.31 and 1.11 mm s?1 respectively were observed for 20RFV glass annealed at 460–550 °C, reflecting precipitation of semiconducting FeVO4 phase having σ of 6.0 × 10?7 S cm?1. It can be concluded that isochronal annealing of 20RFV glass below 450 °C resulted in increase in σ due to the structural relaxation, while annealing above 500 °C resulted in the decrease of σ due to the precipitation of FeVO4 phase. 相似文献
115.
Kohei Matsuzaki Kenta Okuyama Etsuko Tokunaga Motoo Shiro Norio Shibata 《ChemistryOpen》2014,3(6):233-237
A sterically demanding unsymmetrical pentafluorophenyl-triisopropylphenyl-λ3-iodane was developed as an effective reagent for the electrophilic pentafluorophenylation of various β-keto esters and a β-keto amide. 17 examples of α-pentafluorophenylated 1,3-dicarbonyl compounds 3 having a quaternary carbon center are provided. The resulting compounds were nicely transformed into chiral α-pentafluorophenyl ketones with an all-carbon stereogenic center in high yields and high enantioselectivities using asymmetric organocatalysis (up to 98 % ee) or asymmetric metal catalysis (up to 82 % ee). 相似文献
116.
Hardness and slip systems by an indentation method were investigated on different habit planes of orthorhombic hen egg-white lysozyme (O-HEWL) crystals containing water. A dependence of the hardness on the water-evaporation time exhibits three stages as incubation, transition and saturated ones, as tetragonal (T)-HEWL crystals reported previously. The hardness values of (1 1 0), (0 1 0) and (0 1 1) habit planes of O-HEWL in the incubation stage or wet condition exhibits 6, 8 and 10 MPa, respectively. The hardness depends on indented planes but it is independent of the air-humidity and crystal volumes. These values correspond to the intrinsic hardness for O-HEWL crystals containing water. In the incubation stage, the slip traces are clearly observed around the indentation mark and the corresponding six kinds of slip systems are identified to be {0 1 1}<1 0 0>, {1 1 0}<1 1 0>, {0 1 1}<0 1 1>, {1 1 0}<0 0 1>, {1 0 0}<0 0 1> and {0 1 0}<0 0 1>. 相似文献
117.
Development of a New Benzylating Reagent Spontaneously Releasing Benzyl Cation Equivalents at Room Temperature
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Dr. Kohei Yamada Yuichi Tsukada Yukiko Karuo Dr. Masanori Kitamura Prof. Dr. Munetaka Kunishima 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(38):12274-12278
A new O‐benzylating reagent, that is, 4‐(4,6‐diphenoxy‐1,3,5‐triazin‐2‐yl)‐4‐benzylmorpholinium trifluoromethanesulfonate (DPT‐BM), has been developed. Benzyl cation equivalents are generated from DPT‐BM by dissolving the compound in a solvent at room temperature under non‐acidic conditions. The benzylation of various alcohols by using a combination of DPT‐BM and magnesium oxide provided the benzyl ethers in good yields. 相似文献
118.
Dr. Arlin Jose Amali Dr. Hideto Hoshino Dr. Chun Wu Dr. Masanori Ando Prof. Qiang Xu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(27):8279-8282
Highly photoluminescent carbon nanodots (CNDs) were synthesized for the first time from metal–organic framework (MOF, ZIF‐8) nanoparticles. Coupled with fluorescence and non‐toxic characteristics, these carbon nanodots could potentially be used in biosafe color patterning. 相似文献
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