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61.
Goda Hiroshi; Hirasawa Mikami; Yamamoto Ryosuke 《Proceedings London Mathematical Society》2001,83(2):472-492
Let R be a Seifert surface obtained by applying Seifert's algorithmto a connected diagram D for a link L. In this paper, lettingD be almost alternating, we give a practical algorithm to determinewhether L is a fibered link and R is a fiber surface. We furthershow that L is a fibered link and R is a fiber surface for Lif and only if R is a Hopf plumbing, that is, a successive plumbingof a finite number of Hopf bands. It has been known for sometime that this is true if D is alternating, and we show thatit is not always true if D is 2-almost alternating. In the appendix,we partially answer C. Adams's open question concerning almostalternating diagrams. 2000 Mathematical Subject Classification:57M25. 相似文献
62.
Kōchi Mikami Katsuhiko Fujimoto Takashi Kasuga Takeshi Nakai 《Tetrahedron letters》1984,25(52):6011-6014
The diastereo- and/or enantioselection are described in the title rearrangement of the chiral 2-(2-alkenyloxy)methyl 2-oxazolines which eventually provides optically active -hydroxy, γ,δ- unsaturated esters and (+)-verrucarinolactone. 相似文献
63.
Kazunobu Toshima Ken-ichi Kasumi Kanako Kawahara Shuichi Matsumura 《Tetrahedron》2004,60(25):5331-5339
Novel α- and β-stereocontrolled glycosidations using a heterogeneous solid acid, sulfated zirconia (SO4/ZrO2), as an activator have been developed. The glycosidations of manno- and 2-deoxyglucopyranosyl α-fluorides with several alcohols using SO4/ZrO2 in MeCN proceeded α-stereoselectively, while those with the same activator in the presence of MS 5A in Et2O occurred with β-stereoselectivity. Thus, both the α- and β-manno- and 2-deoxyglucopyranosides were effectively obtained by the present glycosidations. 相似文献
64.
65.
We present a practical algorithm to determine the minimal genus of non-orientable spanning surfaces for 2-bridge knots, called the crosscap numbers. We will exhibit a table of crosscap numbers of 2-bridge knots up to 12 crossings (all 362 of them). 相似文献
66.
Asymmetric “Acetylenic” [3+2] Cycloaddition of Nitrones Catalyzed by Cationic Chiral PdII Lewis Acid
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Highly enantioselective [3+2] cycloaddition of ynones and nitrones has been developed. Very bulky ligand, DTBM‐SEGPHOS, was used for an effective asymmetric induction over distal reaction centers on the linear ynone dipolarophile and for prevention of PdII catalyst deactivation by coordination of the nitrones. The reaction has wide scope of substrates in both ynones and nitrones. 相似文献
67.
Ca3Co4O9/Ag composites incorporating different amounts of Ag were synthesized by solid-state reaction. Scanning electron microscopy revealed Ag particles dispersed among and combined with Ca3Co4O9 grains several times larger in size. The electrical resistivity (ρ) of the composites is favorably lower than that of Ca3Co4O9 alone and decreases with increasing Ag content. It can thus be inferred that the highly conductive Ag particles between the oxide grains contribute to the reduction of ρ. Although minimal in smaller amounts, the addition of Ag also seems to have a negative impact on the Seebeck coefficient (S) of the composites due to its poor S. Since the reduction of ρ is more significant than the degradation of S, the power factor is found to be improved by the addition of 10 wt% Ag. 相似文献
68.
Urata S Tsuzuki S Takada A Mikami M Uchimaru T Sekiya A 《Journal of computational chemistry》2004,25(3):447-459
The intermolecular interaction energy curves of CH(3)OCH(3)-CH(2)F(2), CF(3)OCH(3)-CH(2)F(2), CF(3)OCF(3)-CH(2)F(2), CH(3)OCH(3)-CHF(3), CF(3)OCH(3)-CHF(3), and CF(3)OCF(3)-CHF(3) complexes were calculated by the MP2 level ab initio molecular orbital method using the 6-311G** basis set augmented with diffuse polarization functions. We investigate the fluorine substitution effects of both methane and dimethyl ether on intermolecular interactions. In addition, orientation dependence of intermolecular interaction energies is also studied with utilizing eight types of orientations. Our analyses demonstrate that partial fluorinations of methane make electrostatic interaction dominant, and consequently enhance attractive interaction at several specific orientations. On the contrary, fluorine substitutions of dimethyl ether substantially decrease the electrostatic interaction between ether and CH(2)F(2) or CHF(3); thus, there is no such characteristic interaction between the C-H of fluorinated methane and ether oxygen of CF(3)OCF(3) as conventional hydrogen bonding, due to reduced polarity of fluorinated ether. The combination of different pairs of the electrostatic interaction is therefore responsible for the intermolecular interaction differences among the complexes investigated herein and also their orientations. 相似文献
69.
Kōichi Mikami Toshihiko Maeda Naoyuki Kishi Takeshi Nakai 《Tetrahedron letters》1984,25(45):5151-5154
An enantiospecific synthesis of the title compound is described which involves the TiCl4-promoted cyclization of the chiral allylic silane having formyl group, which was obtained via the Claisen rearrangement of (, )-1-trimethylsilyl-1-buten-3-ol. 相似文献
70.