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81.
Hwang IW Park M Ahn TK Yoon ZS Ko DM Kim D Ito F Ishibashi Y Khan SR Nagasawa Y Miyasaka H Ikeda C Takahashi R Ogawa K Satake A Kobuke Y 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(12):3753-3761
The excitation-energy-hopping (EEH) times within two-dimensional cyclic zinc(II)-porphyrin arrays 5 and 6, which were prepared by intermolecular coordination and ring-closing metathesis reaction of olefins, were deduced by modeling the EEH process based on the anisotropy depolarization as well as the exciton-exciton annihilation dynamics. Assuming the number of energy-hopping sites N = 5 and 6, the two different experimental observables, that is, anisotropy depolarization and exciton-excition annihilation times, consistently give the EEH times of 8.0 +/- 0.5 and 5.3 +/- 0.6 ps through the 1,3-phenylene linkages of 5 and 6, respectively. Accordingly, the self-assembled cyclic porphyrin arrays have proven to be well-defined two-dimensional models for natural light-harvesting complexes. 相似文献
82.
Sadahito Aoshima Hiroshi Oda Eiichi Kobayashi 《Journal of polymer science. Part A, Polymer chemistry》1992,30(11):2407-2413
Living cationic polymerization of alkoxyethyl vinyl ether [CH2?CHOCH2CH2OR; R: CH3 (MOVE), C2H5 (EOVE)] and related vinyl ethers with oxyethylene units in the pendant was achieved by 1-(isobutoxy)ethyl acetate ( 1 )/Et1.5AlCl1.5 initiating system in the presence of an added base (ethyl acetate or THF) in toluene at 0°C. The polymers had a very narrow molecular weight distribution (M?w/M?n = 1.1–1.2) and the M?n proportionally increased with the progress of the polymerization reaction. On the other hand, the polymerization by 1 /EtAlCl2 initiating system in the presence of ethyl acetate, which produces living polymer of isobutyl vinyl ether, yielded the nonliving polymer. When an aqueous solution of the polymers thus obtained was heated, the phase separation phenomenon was clearly observed in each polymer at a definite critical temperature (Tps). For example, Tps was 70°C for poly(MOVE), and 20°C for poly(EOVE) (1 wt % aqueous solution, M?n ~ 2 × 104). The phase separation for each case was quite sensitive (ΔTps = 0.3–0.5°C) and reversible on heating and cooling. The Tps or ΔTps was clearly dependent not only on the structure of polymer side chains (oxyethylene chain length and ω-alkyl group), but also on the molecular weight (M?n = 5 × 103-7 × 104) and its distribution. © 1992 John Wiley & Sons, Inc. 相似文献
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Tsutsumi T Amakura Y Nakamura M Brown DJ Clark GC Sasaki K Toyoda M Maitani T 《The Analyst》2003,128(5):486-492
The chemical-activated luciferase expression (CALUX) assay is a reporter gene assay that detects dioxin-like compounds based on their ability to activate the aryl hydrocarbon receptor (AhR) and thus expression of the reporter gene. In this paper, the CALUX assay was examined for its application in the screening of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (dioxin-like PCBs) in retail fish. The sample extracts were cleaned up on a sulfuric acid-silica gel column followed by an activated carbon column, and the AhR activity of the separated PCDD/F and dioxin-like PCB fractions was determined using the assay. The quantitative limit for 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) was 0.98 pg ml(-1) (0.19 pg assay(-1) in the standard curve, corresponding to 0.16 pg g(-1) of CALUX-based toxic equivalency (2,3,7,8-TCDD equivalents) in the tested sample. Recovery tests in which dioxins were added to fish samples resulted in acceptable recoveries (77-117%). The CALUX assay performed well in the analysis of dioxins in fish samples and a comparative study revealed a strong correlation between the CALUX assay and high-resolution gas chromatography-high-resolution mass spectrometry analysis for the determination of PCDD/Fs (r = 0.89) and dioxin-like PCBs (r = 0.91) in retail fish (n = 22). These data revealed that the CALUX assay would be a useful screening method for PCDD/Fs and dioxin-like PCBs in retail fish. 相似文献
85.
Yoshiaki Yoshida Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2018,56(19):2255-2262
Polyaddition of various diisothiocyanates and dithiols was achieved with triethylamine in dimethylformamide at 25 °C for 12 h under nitrogen, and then the corresponding polydithiourethanes (PDTUs) were obtained with high yield and molecular weight without depending on the monomer structures, although the dithiol monomer of the low nucleophilicity was unsuitable for polyaddition in this system. The chemical and physical properties of the obtained PDTUs such as solvent solubility, glass transition temperature, thermal stability, transparency, refractive index, and tensile strength, were analyzed in detail by gel permeation chromatography, nuclear magnetic resonance, Fourier transform infrared–attenuated total reflection, ultraviolet–visible, differential scanning calorimetry, thermogravimetric analysis, and tensile testing measurements. These results proved that PDTUs and their cast films having the aliphatic diisothiocyanate and dithiol moieties exhibited excellent chemical and physical properties compared to that of the aromatic PDTUs. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2255–2262 相似文献
86.
Control of thermoresponsivity of biocompatible poly(trimethylene carbonate) with direct introduction of oligo(ethylene glycol) under various circumstances
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Nalinthip Chanthaset Yoshikazu Takahashi Yoshiaki Haramiishi Mitsuru Akashi Hiroharu Ajiro 《Journal of polymer science. Part A, Polymer chemistry》2017,55(20):3466-3474
Poly(trimethylene carbonate) (PTMC) is a well‐known biodegradable polymer with good biocompatible properties which make it suitable for biomedical applications. Poly(5‐[2‐{2‐(2‐methoxyethoxy)ethyoxy}‐ethoxymethyl]‐5‐methyl‐1,3‐dioxa‐2‐one) (PTMC‐MOE3OM) and copolymers, bearing oligo ethylene glycol (OEG) at the side chain of PTMC backbone, were selected to investigate the cloud point behavior by solvents such as PBS, water, 10% ethanol solution and various ionic strengths. A pH‐responsive copolymer, poly(TMCM‐MOE3OM‐co‐(5‐methyl‐5‐carboxylic‐1,3‐dioxane‐2‐one)) as carboxylic acid carbonate showed a decreased critical temperature at pH 2. Photo‐responsive copolymer, poly(TMCM‐MOE3OM‐co‐coumarin derivatives) bearing 1% and 10% of photo‐induced molecules (7‐[(5‐(5‐methyl‐1,3‐dioxa‐2‐one)methoxy)]‐methoxy coumarin (TMCM‐coumarin)) exhibited a low cloud point because of the hydrophobic moieties. Meanwhile, alternative coumarin polymer including 2% of 4‐methyl‐7‐[(5‐(5‐methyl‐1,3‐dioxa‐2‐one)methoxy)butoxy)]‐methoxy coumarin (TMCM‐4‐methyl‐coumarin) has been successfully synthesized and copolymerized as a novel molecule. The various combinations of monomers were studied and the significant properties were determined via external triggers after copolymerization. This study showed basically synthetic progress toward designs and trivial rationalization of thermoresponsive copolymers close to body temperature. At present, various pendant groups as side part affect to the lower critical solution temperature (LCST) and biodegradable polymer in order to utilize the actual external stimuli application. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3466–3474 相似文献
87.
In this paper, we establish new sufficient conditions for the infected equilibrium of a nonresident computer virus model to be globally asymptotically stable. Our results extend two kind of known results in recent literature. 相似文献
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90.
Hiroya Takada Yoshiaki Nishibayashi Sanjay Kumar Srivastava Kouichi Ohe Sakae Uemura 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):629-632
Asymmetric intramolecular selenocyclisation of alkenoic acids, alkenols and alkenyl urethanes using chiral ferrocenylselenenyl cations proceeds smoothly to give the corresponding lactones, cyclic ethers and N-heterocyclic compounds, respectively, in moderate yields with very high diastereoselectivities. 相似文献