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排序方式: 共有204条查询结果,搜索用时 0 毫秒
1.
This paper presents a simple chaotic circuit consisting of two capacitors, one linear two-port VCCS and one time-state-controlled
impulsive switch. The impulsive switch causes rich chaotic and periodic behavior. The circuit dynamics can be simplified into
a one-dimensional return map that is piecewise linear and piecewise monotone. Using the return map, we clarify parameter conditions
for existence of chaotic and periodic attractors and coexistence state of attractors. 相似文献
2.
3.
Shinji Toyota Takashi Nakagawa Masashi Kotani Michinori
ki Hidehiro Uekusa Yuji Ohashi 《Tetrahedron》2002,58(52):10345-10351
All the three possible rotamers of the title compound were separated by chromatography, and unambiguously identified by NMR and X-ray analysis. One of the isomers was optically inactive Ci conformation. The other optical active forms were resolved to give a pair of enantiomers, which were characterized by optical rotation and CD spectra. Thus the optical inactivity of a compound such as meso-tartaric acid that can take Ci conformation in solution, is now ascribed to that the molecule has an optically inactive Ci conformer and equal amounts of optically active conformers, that are enantiomers, in solution. 相似文献
4.
The effects of a magnetic field on spectral intensities in plasma-jet spectrometry were examined, and detection limits for rare-earth elements were calculated. Plasma-jet emission spectrometry was applied to the determination of lanthanum, yttrium and gadolinium in a monazite sample from which thorium had been separated. A standard addition method was used in order to improve accuracy, and the internal standard and background compensation method was applied to measurements of spectral line intensities to achieve good precision. The coefficient of variation was 1.51% for 50 μg La ml?1. 相似文献
5.
Function of the Reaction Center of Green Sulfur Bacteria 总被引:1,自引:0,他引:1
The reaction center (RC) of green sulfur bacteria belongs to the Fe-S type RC, as do the photosystem I of oxygenic photosynthetic organisms and the RC of heliobacteria. The core parts of the green sulfur bacterial and the heliobacterial RC are assumed to be homodimeric, in contrast to those of purple bacteria, photosystem I and photosystem II. This paper describes recent advances in the study of the function of the green sulfur bacterial RC. 相似文献
6.
Misa Sugino Keisuke Hatanaka Tetsuya Miyano Ichiro Hisaki Mikiji Miyata Aya Sakon Hidehiro Uekusa Norimitsu Tohnai 《Tetrahedron letters》2014
An organic salt composed 9,10-bis(4-aminophenyl)anthracene and hypophosphorous acid emits yellow-green fluorescence in the crystalline state. The salt also gives water inclusion crystal which provides blue-green fluorescence. Single X-ray crystal studies revealed that water molecules induced the fluorescence change resulting from reaggregation of molecular packing. 相似文献
7.
The effect of amines on the selective bromination of some β-substituted-2-butenoic esters is described. The bromination of methyl (Z)-4-t-butyldiphenylsilyloxy-3-methylbutenoate 2 in the presence of DIPEA (N, N-diisopropylethylamine) and the successive treatment of the obtained dibromide with potassium t-butoxide afford the desired Z bromide selectively. But the corresponding E bromide forms exclusively when 2, 6-di-t-butyl-4-methylpyridine is used in the bromination. 相似文献
8.
Dr. Bernd M. Schmidt Berit Topolinski Dr. Mihoko Yamada Dr. Shuhei Higashibayashi Prof. Dr. Mitsuhiko Shionoya Prof. Dr. Hidehiro Sakurai Prof. Dr. Dieter Lentz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(41):13872-13880
The syntheses and properties of corannulenes carrying electron‐withdrawing groups (F, CF3, C6F5) are reported. Direct fluorination of corannulene (C20H10) was carried out with xenon difluoride, and the crystal structure of the product was confirmed by the X‐ray analysis. Novel trifluoromethylated corannulenes, including the versatile 4,9‐dibromo‐1,2‐bis(trifluoromethyl)corannulene, were obtained by various established ring‐closing reactions. Besides the use of hexafluorobutyne for the construction of fluoranthenes by Diels–Alder reaction as precursor molecules to form 1,2‐disubstituted corannulenes, bis(pentafluorophenyl)acetylene was employed as dienophile. The molecular structure and crystal packing of a trifluoromethylated corannulene was determined by single‐crystal X‐ray analysis and compared with those known brominated and trifluoromethylated corannulenes. The general electron‐acceptor properties of corannulenes bearing substituents introduced in particular positions by liquid‐phase synthesis are discussed together with published computational results. 相似文献
9.
Li-Hsiang Wang Norihiko Hayase Dr. Haruki Sugiyama Juntaro Nogami Prof. Dr. Hidehiro Uekusa Prof. Dr. Ken Tanaka 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(41):18107-18113
Single and double cyclophenylene–ethynylenes (CPEs) with axial and helical chirality have been synthesized by the Sonogashira cross-coupling of di- and tetraethynyl biphenyls with a U-shaped prearomatic diiodoparaphenylene followed by reductive aromatization. X-ray crystallographic analyses and DFT calculations revealed that the CPEs possess highly twisted bent structures. Bend angles on the edge of the paraphenylene units were close to the value of [5]cycloparaphenylene (CPP)—the smallest CPP to date. The double and single CPEs possessed stable chirality despite flexible biphenyl structures because of the high strain in the diethynyl–paraphenylene moiety. In both the single and double CPEs, orbital interactions along the biphenyl axis were observed by DFT calculations in LUMO and LUMO+2 of the single CPE and LUMO+1 of the double CPE, which likely cause lowering of these orbital energies. Concerning chiroptical properties: boosting of the gabs value was observed in the biphenyl-based double CPE, as well as the binaphthyl-based single CPE, compared to the biphenyl-based single CPE. 相似文献
10.
Yukimasa Aida Juntaro Nogami Dr. Haruki Sugiyama Prof. Dr. Hidehiro Uekusa Prof. Dr. Ken Tanaka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(55):12579-12588
The enantioselective synthesis of polycyclic aromatic hydrocarbon (PAH)-based planar chiral cyclophanes was achieved for the first time by the rhodium-catalyzed intramolecular regio- and enantioselective [2+2+2] cycloaddition of tethered diyne-benzofulvenes followed by stepwise oxidative transformations. The thus synthesized planar chiral bent cyclophanes, that possess bent p-terphenyl- and 9-fluorenone-cores, were converted to 9-fluorenol-based ones with excellent ee values of >99 % by diastereoselective 1,2-reduction. These 9-fluorenol-based cyclophanes exhibited high fluorescence quantum yields, which were significantly higher than that of an acyclic reference molecule (78–82 % vs. 48 %). The bending effect on the chiroptical property was also examined, which revealed that the anisotropy factors (gabs values) for electronic circular dichroism (ECD) of these 9-fluorenol-based planar chiral bent cyclophanes increase as the tether length becomes shorter. 相似文献