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101.
The cycloaddition reaction of N-ethoxycarbonyl-1H-azepine with 2,5-dimethoxycarbonyl-3,4-diphenylcyclopentadienone gave anti-endo [4+2]π and exo [6+4]π cycloadducts. These structures were fully identified by X-ray crystallographic techniques. Mechanism for their cycloaddition reactions are also discussed. 相似文献
102.
Fluoro-, chloro-, bromo-, and iodocyclopropane derivatives were obtained in 10–80% yields by the reaction of FCHI2, ClCHI2, BrCHI2, and CHI3, respectively, with Cu in the presence of olefins. The reaction was electrophilic, and proceeded stereospecifically, i.e., cis and trans olefins afforded cyclopropane derivatives whose configurations with respect to the substituents from original olefins were cis and trans, respectively. Since isomeric olefins were not detected in the reaction mixture which would be expected from the insertion of the corresponding free monohalocarbenes into C—H bonds, the reaction seemed to proceed via organocopper intermediates rather than free monohalocarbenes. With respect to the configuration of the halogen introduced by the new reaction, the cis or endo isomers were generally obtained predominantly over the corresponding trans or exo isomers. 相似文献
103.
Hamao Umezawa Tomohisa Takita Yukio Sugiura Masami Otsuka Susumu Kobayashi Masaji Ohno 《Tetrahedron》1984,40(3):501-509
Biosynthetic intermediates and synthetic analogues of bleomycin (BLM) have been investigated for their metal binding, dioxygen activation, and DNA cleavage. Molecular O2 was activated by the Fe(II) complex of a synthetic model ligand. Nucleotide sequence specificities in DNA cleavage by the BLM-Fe(II) and deglyco-BLM-Fe(II) complexes were almost identical. It has been shown that (1) the β-aminoalanine-pyrimidine-β-hydroxyhistidine portion of BLM is essential for the metal binding and dioxygen activation and (2) the bithiazole moiety contributes to the specific binding to guanine base of DNA. 相似文献
104.
Shibukawa Masami Saito Masanori Kuroda Rokuro 《Analytical and bioanalytical chemistry》1984,319(4):410-414
Analytical and Bioanalytical Chemistry - The size-exclusion chromatographic behaviour of 8-hydroxyquinoline (abbreviated as HOx) and its metal(II, III) chelates on Fractogel PVA 2000 in p-dioxane... 相似文献
105.
Most national curricula for both primary and secondary grades encourage the active involvement of learners through the manipulation of materials (either concrete models or dynamic instruments). This trend is rooted in the emphasis given, at the dawn of ICMI, to what might be called an experimental approach: the links between mathematics, natural sciences and technology were in the foreground in the early documents of ICMI and also in the papers of its first president, Felix Klein. However, the presence of this perspective in teaching practice is uneven. In this paper, we shall reconstruct first an outline of what happened in three different parts of the world (Europe, USA and Japan) under the direct influence of Klein. Then, we shall report classroom activities realized in the same regions in three different research centres: the Laboratory of Mathematical Machines at the University of Modena and Reggio Emilia, Italy (http://www.mmlab.unimore.it); the pedagogical space of Kinematical Model for Design Digital Library at Cornell, USA (http://kmoddl.library.cornell.edu/); and the Centre for Research on International Cooperation in Educational Development at Tsukuba University, Japan (http://math-info.criced.tsukuba.ac.jp/). They have maintained the reference to concrete materials (either models or instruments), with original interpretations that take advantage of the different cultural conditions. Although in all cases the reference to history is deep and systematic, the synergy with mathematical modelling and with information and communication technologies has been exploited, not to substitute but to complement the advantages of the direct manipulations. 相似文献
106.
In this paper we shall make a further study on the the equivalence problem, i.e., equivalent conditions to the Riemann hypothesis in terms of Farey series by developing a rather analytical (-arithmetical) method to establish unexpected short interval results, namely
results, therewith simultaneously clarifying the underlying reasons for
results obtained in Part I. 相似文献
107.
The purpose of this paper is to study the structure of congruence modules (or modules of congruences) associated with Eisenstein series in various contexts in the Λ-adic theory of elliptic modular forms. Under some assumptions, we explicitly describe such modules in terms of Kubota-Leopoldt p-adic L-functions. 相似文献
108.
Summary Electrothermal atomization of thallium in a molybdenum microtube atomizer is described. The addition of a low flow rate of hydrogen to argon purge gas resulted in higher peak absorption. In the presence of thiourea the addition of hydrogen did not alter the peak absorption value in pure argon, although the peak temperature shifted to lower region. A high heating rate of the atomizer was recommended for higher peak absorption and improvement of interferences from concomitants. The interferences by concomitants at 50 ng level were modified with thiourea. Modification with thiourea was effective even for interferences from 500 ng of cadmium, zinc or copper, while it was insufficient for 500 ng of calcium, magnesium, chromium, bismuth or lead. Provided the atomization of thallium was carried out at high heating rate and on addition of thiourea as a matrix modifier, the interference from chloride (500 ng) was modified. The absolute sensitivity (0.0044 abs) for thallium was 1.2 pg.
Thalliumbestitmmung durch AAS mit elektrothermischer Atomisierung in einem metallischen Atomizer
Zusammenfassung Zur AAS-Bestimmung von Thallium wird eine Molybdän-Mikroröhre als Atomizer empfohlen. Zusatz von geringeren Wasserstoffmengen zum Argongas ergab eine höhere Absorption. In Gegenwart von Thioharnstoff erfolgte durch Wasserstoff-Zugabe keine Änderung des Absorptionswertes in reinem Argon, obwohl die Peaktemperatur in einen niederen Bereich verschoben wurde. Für höhere Absorption und zur Verminderung von Störungen durch Begleitelemente wurden höhere Erhitzungsgeschwindigkeiten empfohlen. Störungen durch Begleitelemente im Bereich von 50 ng konnten mit Thioharnstoff verringert werden. Die Zugabe von Thioharnstoff erwies sich ebenfalls als wirksam für 500 ng Cadmium, Zink oder Kupfer, während sie für dieselben Mengen an Calcium, Magnesium, Chrom, Bismut oder Blei ungenügend war. Mit hoher Erhitzungsgeschwindigkeit und Thioharnstoffzusatz konnte eine Störung durch Chlorid im Bereich von 500 ng reduziert werden. Die absolute Empfindlichkeit für Thallium (0,0044 abs) betrug 1,2 pg.相似文献
109.
Masami Kurano Masami Yasuda Jun-Ichi Nakagami Yuji Yoshida 《Fuzzy Optimization and Decision Making》2004,3(4):367-374
Stimulated by Zadeh's paper (Journal of Statistical Planning and Inference,2002, 105, 233--264), we will try to consider a perceptive analysis of the optimal stopping problem. In this paper, the fuzzy perception value of the expectation of the optimal stopped reward is characterized and calculated by a new recursive equation. Also, a numerical example described by triangular fuzzy numbers is given. 相似文献
110.
Hiroshi Tabata Kinya Kumazawa Masami Funakawa Jun-ichi Takimoto Makio Akimoto 《Optical Review》1996,3(2):139-145
This paper describes the mechanism generating the beautiful wing colors of various male butterflies and the relationship between the wing material and the color appearance. The microstructure of the scales covering the upper surface of the wings was analyzed with the aid of a scanning electron microscope. The basic mechanism of color generation of structurally colored scales is determined for the first time in accordance with the theory of optical interference in thin film layers using a model of wing scales. Optical properties were found in relation to the three-dimensional spectral reflectance of the samples, and differences were observed between the brightness perceived in subjective evaluations and calculated values based on the reflective spectra of the structurally colored wings. The results of this study suggest that the microroughness of the upper wing surface may influence the perceived gloss of structurally colored wings. 相似文献