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951.
952.
1,1-Dimethylsilacyclobutane, abbreviated as DMSCB, was investigated by Fourier transform microwave spectroscopy, by paying special attention to two types of large-amplitude motions in the molecule: two-top internal rotation and four-membered ring puckering and also to the coupling between the two. In order to clarify the unique feature of the internal dynamics in DMSCB in detail, two independent approaches were employed, one being a combination of a standard two-top theory of internal rotation and an established theory of ring puckering and the other a theory of large-amplitude motions developed by Hougen and his collaborators. In accordance with predictions by the two approaches based on symmetry consideration, the observed rotational spectra were found split into eight (or six when AE/EA lines were not resolved) components, which were assigned to the two-top states of AA, AE, EA, and EE symmetry, each being further split by puckering into two: the symmetric and antisymmetric states. The analyses by two approaches gave spectroscopic results, which were in good agreement with each other. The spectroscopic data on the normal species, combined with those on Si and C isotopic species, yielded molecular structure parameters including the puckering angle (the dihedral angle between the CSiC and CCC planes) of 28.64° or 30.26° (two possible sets). The splitting between the two lowest puckering states was determined to be 11.90(22) MHz, which led, with the equilibrium puckering angle, to the potential barrier to puckering of 395.3 or 347.0 cm−1 for the two sets, respectively, which was slightly lower than the value 440 cm−1 in a “parent” molecule: silacylcobutane. The first-order terms of the coupling between CH3 internal rotation and overall rotation were converted to the barrier to internal rotation of 567.8 and 505.1 cm−1 in the AE (two methyl groups rotating in the same direction, as viewed from Si) and EA (two methyl groups rotating in the opposite direction) states, respectively, which corresponded to the torsional frequencies of 154 and 144 cm−1, at variance with the Raman data of 177 and 172 cm−1, previously reported in literature. 相似文献
953.
Wilson Agerico Diño Yoshio Miura Hiroshi Nakanishi Tsuyoshi Sugimoto 《Solid State Communications》2004,132(10):713-718
We investigate and discuss how hydrogen behaves at the edges of a graphite sheet, in particular the armchair edge. Our density functional theory-based calculations results show that, in contrast to the zigzag edge [W.A. Diño, H. Nakanishi, H. Kasai, T. Sugimoto, T. Kondoe, e-J. Surf. Sci. Nanotech. 2 (2004) 77. [25]], regardless of orientation, there is an activation barrier hindering H2 dissociation at the armchair edges. And once they do get dissociatively adsorbed at the armchair edges, we find that it would be extremely hard to desorb the H from their adsorption sites at the armchair edges. Furthermore, we also found that, consistent with our earlier conclusions [W.A. Diño, Y. Miura, H. Nakanishi, H. Kasai, T. Sugimoto, J. Phys. Soc. Jpn. 72 (2003) 1867. [24]], it is unlikely that we would find a whole H2 in between plain graphite sheets. 相似文献
954.
Tsuyoshi Maeda 《Journal of Physics and Chemistry of Solids》2005,66(11):1924-1927
In order to quantitatively evaluate the formation energies of Cu, In/Ga/Al and Se vacancies in chalcopyrite-type CuInSe2 (CIS), CuGaSe2 (CGS) and CuAlSe2 (CAS), first-principles pseudopotential calculations using plane-wave basis functions were performed. All calculations were performed using a supercell with 64 atoms, which was eight times greater than the number of atoms in a primitive cell with eight atoms. The formation energies of point defects were calculated as a function of the atomic chemical potentials of constituent elements. Atomic arrangements around the vacancy were optimized allowing relaxation of the first- and second-nearest-neighbor atoms of the vacancy. The obtained results were as follows: (1) the formation energy of Cu vacancy was smaller than those of the other vacancies in CIS, CGS and CAS. Under the Cu-poor condition, the formation energy of Cu vacancy in CIS was lowest among those in them; (2) the formation energy of Se vacancy in CIS was relatively lower than those in CGS and CAS; (3) the formation energy of (2VCu+InCu) pair in CIS was greatly dependent on the chemical potential of the constituent elements, i.e. Cu, In and Se. On the other hand, the formation energies of (2VCu+GaCu) in CGS and (2VCu+AlCu) in CAS were not largely dependent on the chemical potential of the constituent elements. Under the Cu-poor condition, the formation energy of (2VCu+InCu) pair in CIS was much lower than those of (2VCu+GaCu) in CGS and (2VCu+AlCu) in CAS. 相似文献
955.
Oxidation of light alkanes, CH4, C2H6, and C3H8, could be performed at 40°C by using the EuCl3-catalytic system (EuCl3, O2, Zn0, and CF3CO2H). In the case of CH4 oxidation, MeOH was produced from CH4 but CO2 from CF3CO2H could not be avoided. However, selective oxygenations of C2H6 (89% selectivity) and C3H8 (91%) could be performed. In the oxidation of C2H6, EtOH was primary product and the successive oxidation of EtOH gave MeCHO and CO2. Regio-selectivities (1°:2°) observed in the oxidation of C3H8 suggested that an electrophilic active oxygen species was generated in the EuCl3-catalytic system. This active oxygen could not oxidize C-H bonds of MeOH (CF3CO2Me) because of a strong electron-withdrawing effect of CF3CO-group. Eu2+ species produced by the reduction with Zn0 was studied by UV-visible spectra. The spectral data proposed that O2 was reductively activated through the redox of Eu3+/Eu2+. 相似文献
956.
Tsuyoshi Katayama 《Operations Research Letters》2005,33(3):295-300
We consider an MX/G/1 queue with nonpreemptive time-limited service and timer and exhaustive vacations. We analyze the waiting time distribution in this multiple vacation model by applying the level-crossing method to a workload process with two types of vacations. 相似文献
957.
In this paper, some generalized invariant subspaces for uncertainlinear infinite-dimensional systems in the sense that each uncertainparameters are in given real intervals are studied. 相似文献
958.
Hidenori Otsuka Taketomo Sanbai Daisuke Matsukuma Yusuke Ikenaga 《Colloid and polymer science》2014,292(2):291-300
We have newly synthesized amphiphilic block copolymers composed of hydrophilic poly(ethylene glycol) (PEG) and hydrophobic pyridine segments (PEG-b-Py). Chain transfer agent-terminated PEG was subsequently chain-extended with 3-(4-pyridyl)-propyl acrylate to obtain PEG-b-Py by reversible additional-fragmentation chain transfer polymerization. Particularly, the effect of varying molecular weight (Mn) of PEG (Mn?=?2,000 and 5,000) and Py in the block copolymers was investigated in terms of critical micelle concentration, pyrene solubilization, micelle size distribution, and association number per micelle. Based on the amphiphilic balance, PEG-b-Pys formed core-shell type polymer micelle. The association number of PEG2k-b-Py was higher than that of PEG5k-b-Py, suggesting the degree of phase separation strongly depended on PEG Mn. Furthermore, the adsorption of PEG-b-Py copolymer onto silica nanoparticles as dispersant was studied to estimate the effect of PEG Mn in the copolymers and their solubility in the medium on the adsorption. Adsorbed density of PEG2k-b-Py copolymer onto silica nanoparticle was higher than that of PEG5k-b-Py, which was significantly correlated with the degree of phase separation. Furthermore, the adsorbed amount of copolymer increased with the increase in ionic strength due to the reduced solubility of PEG in the buffer solution. The resultant dispersion stability was highly correlated with the graft density of copolymer onto silica surface. However, the stability of PEG2k-b-Py coated particles was lower than that with PEG5k-b-Py, this is attributed to the relatively thin layer of PEG at the silica surface, which cannot provide the system with sufficient steric stabilization as the salt concentration increases. These fundamental investigations for the surface modification of the nanoparticle provide the insight into the highly stable colloidal dispersion, particularly in the physiological condition with high ionic strength. 相似文献
959.
Koichi Kutsuzawa Toshihiro Suzuki Hidehiro Kishimoto Akiichi Murakami Takachika Azuma Ryo Abe Hidenori Otsuka 《Colloid and polymer science》2014,292(4):839-848
Recombinant Chinese hamster ovary (rCHO) cells have been the most commonly used mammalian host for large-scale commercial production of therapeutic proteins. Although recent advances in 3D culture of rCHO cells is preferred to 2D monolayer culture for highly productive and robust expression of therapeutic proteins, there exists still limitation for efficient protein production. Therefore, a new cell culture system is essentially required for an efficient protein production. Here, we report on a new 3D cell culture system as a spheroid cell culture on the micropattern array for efficient production of protein by CHO cells. Particularly, cocultivation of CHO spheroids with bovine aortic endothelial cells (BAEC) as a feeder layer cells was essential to stably increase a protein production. We investigated the co-culture mechanism of functional enhancement with respect to the cell–cell interactions. Functional comparison between 2D and 3D co-cultures suggested the preferred configuration as spheroid for higher protein production. Specifically, to estimate the effect of respective cell constitution in co-cultured spheroids on the protein production per CHO cell, the number of viable cells in cell proliferation was determined with culture periods. These studies demonstrated the significant role of micropatterned BAEC as a feeder layer for the retained formation of CHO spheroids, resulting in predominantly enhanced production of proteins, although the functional enhancement of CHO cells was obtained by co-culture with BAECs in both 2D and 3D configurations. Thus, heterotypic cell communications that play indispensable roles in increasing CHO functions should be properly obtained in 3D cell configurations. Significantly, these spheroids in the serum-free medium drastically enhanced protein expression level up to sevenfold compared with CHO monospheroids, suggesting that a suitable culture conditions for heterotypic cell–cell interactions would allow improved protein secretion to occur unimpeded. 相似文献
960.
Ken-ichi Itoh Kaoru Nakamura Tadashi Aoyama Tsuyoshi Kakimoto Masahiko Murakami Toshio Takido 《Tetrahedron letters》2014
Asymmetric reduction of ketone by a microalga, Synechocystis sp. PCC 6803, smoothly afforded to the corresponding (S)-alcohol in excellent enantiomeric excess by the aid of illumination of orange and red LED lights which are more effective than other LEDs such as blue and green lights. The condition under minimum energy flux (1.0 W/m2) of orange-red LEDs is enough for the reduction of ketone, and it seems that orange-red light rather effectively forwarded the regeneration of coenzyme. 相似文献