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291.
利用氧化法成功地合成了同核meso位直结型稳定卟啉二聚体锌络合物,收率接近理论值;无论是碱式还是金属络合物都显示出卟啉环间成平面正交的电子吸收光谱;在循环伏安图谱中都显示出卟啉环间再氧化还原过程中较强烈的库仑作用;每个卟啉环的一电子氧化或还原均为可逆过程。 相似文献
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Daisuke Sawai Mika Miyamoto Tetsuo Kanamoto Masayoshi Ito 《Journal of Polymer Science.Polymer Physics》2000,38(19):2571-2579
No systematic study has been reported on the lamellar thickening in atactic poly(acrylonitrile) (PAN) upon annealing because PAN, in the form of solution‐cast films or their drawn products, generally shows no small‐angle X‐ray scattering (SAXS) maximum corresponding to the lamellar thickness. In this work, PAN crystals were precipitated during the thermal polymerization of acrylonitrile in solution. The nascent PAN film, obtained by the filtration of the crystal suspension, exhibited a clear SAXS maximum revealing the lamellar structure. The lamellar thickening upon annealing of the nascent PAN films was studied in the temperature range 100–180 °C, where the degradation was minimal, as confirmed by the absence of an IR absorption band at 1605 cm−1 ascribed to the cyclized nitrile groups. Above 190 °C, the degradation of the samples was significant, and the SAXS became too broad to determine the scattering maximum. The long period was significantly affected by the annealing time (ta) and the temperature (Ta). Depending on ta, three stages were observed for the lamellar thickening behavior. The lamellar thickness stayed constant in stage I (ta = 0.5–3 min, depending on Ta), rapidly increased in stage II (ta = 0.5–8 min), and stayed at a constant value characteristic for each Ta at yet longer ta's in stage III. The lamellar thickness characteristic for Ta increased rapidly with increasing Ta at 165 °C (or higher), which was 152 °C lower than the estimated melting temperature of PAN (Tm = 317 °C). A possible mechanism for such lamellar thickening in PAN far below the Tm is discussed on the basis of the enhanced chain mobility in the crystalline phase above the crystal/crystal reversible transition at 165–170 °C detected by differential scanning calorimetry and wide‐angle X‐ray diffraction. The structural changes associated with annealing are also discussed. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2571–2579, 2000 相似文献
296.
Koji Ishizu Daisuke Takahashi Hisashi Takeda 《Macromolecular rapid communications》2000,21(10):660-664
Two poly(4‐methylstyrene) (P4MS)‐block‐polystyrene (PS)‐block‐P4MS triblock copolymers were prepared by successive anionic addition of styrene and 4‐methylstyrene monomers as the core backbone ( CB ) for the architecture of block‐graft polymers. Both terminal 4‐methylstyrene blocks of CB were metalated with a sec‐butyllithium (sec‐BuLi)/tetramethylethylenediamine (TMEDA) complex in cyclohexane. The first‐generation block‐graft polymer ( 1BG ) was prepared by anionic polymerization of α‐methylstyrene by the lithiated CB in tetrahydrofuran (THF) at –78°C and subsequently the terminal graft ends were capped with a small amount of 4‐methylstyrene. The characterization of those block‐graft polymers was carried out in detail. 相似文献
297.
Asynchronously tuned elementary cellular automata (AT-ECA) are described with respect to the relationship between active and passive updating, and that spells out the relationship between synchronous and asynchronous updating. Mutual tuning between synchronous and asynchronous updating can be interpreted as the model for dissipative structure, and that can reveal the critical property in the phase transition from order to chaos. Since asynchronous tuning easily makes behavior at the edge of chaos, the property of AT-ECA is called the unfolded edge of chaos. The computational power of AT-ECA is evaluated by the quantitative measure of computational universality and efficiency. It shows that the computational efficiency of AT-ECA is much higher than that of synchronous ECA and asynchronous ECA. 相似文献
298.
Daisuke Nakano Kenji Ishitsuka Madoka Ishihara Ryota Tsuchihashi Masafumi Okawa Kazuo Tamura Junei Kinjo 《Molecules (Basel, Switzerland)》2021,26(24)
During the screening of novel chemotherapeutic candidates from plants against adult T-cell leukemia/lymphoma, we identified that the extracts of Thuja occidentalis (Cupressaceae) showed potent anti-proliferative activity in MT-1 and MT-2 cells. Therefore, we attempted to isolate the active components from this plant. We isolated and identified 32 compounds (1–32; eight lignans, 18 terpenoids, and six flavonoids) from the extracts of the leaves and cones. Their structures were determined by spectroscopic analysis. Several of the isolated compounds inhibited the growth of both cell lines. Lignans showed more potent activity than other classes of compounds. A comparison of the activities of compounds 1–8 revealed that the presence of a trans-lactone (linkage of C-6 to C-7) correlated with increased activity. Diterpenes showed moderate activity, and the presence of a ketone moiety at the C-7 position correlated with increased activity in compounds 12–21. In addition, biflavones showed moderate activity, and the presence of methoxy functions appeared to influence the activity of these compounds. Several lignans were lead compound of anti-cancer reagent (etoposide). In conclusion, not only lignans, but also diterpenes and/or biflavones, may be promising candidates for the treatment of adult T-cell leukemia/lymphoma. 相似文献
299.
Guan-Yeow Yeap Faridah Osman Keisuke Ito Daisuke Takeuchi Chien-Min Lin Hong Cheu Lin 《Liquid crystals》2017,44(5):809-821
A series of symmetrical S-shaped mesogens based on 4,4′-bis-(6-bromohexyloxy)biphenyl as a central unit containing two 2-{6-[4-(4-substitutedphenylazo)phenoxy]hexyloxy}phenol as side-chain groups has been successfully synthesised. The terminal substituent was varied from halogen (X = F, Cl, Br and I) to non-halogen (X = C2H5 and OC2H5). The oligomers with C2H5 and OC2H5 substituents exhibit predominantly the monotropic nematic (N) phase. The OC2H5-containing derivatives possess long-range stability of N phase than its C2H5-containing analogue in which it has small range of N phase stability. As for halogen-containing analogues, oligomer with F exhibits monotropic N phase whilst oligomers with Cl and Br exhibit monotropic N and smectic A (SmA) phases. In addition, homologue with Br shows additional phase which is smectic B (SmB) phase upon further cooling. However, the oligomers in which F, Cl and Br were substituted by I exhibits purely monotropic SmA and SmB phases. X-ray diffraction measurements reveal that the smectic phase is inclined to the monolayer structure. 相似文献
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