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81.
Regio‐ and stereoselective 1,3‐dipolar cycloaddition of nitrile oxides to internal 2‐pentenols, α,β‐unsaturated esters and amides catalyzed by R‐(+) BINOL‐lanthanide complexes affords corresponding 3‐aryl‐2‐isoxazolines with enantioselectivities up to 89% ee. 相似文献
82.
Nishimura G Maehara H Shiraishi Y Hirai T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(1):259-271
An azamacrocyclic ligand (L) containing two anthracene (AN) fragments connected through two triethylenetetramine bridges has been synthesized, in which each of the bridges can coordinate with one metal cation. The effects of pH and metal cations (Zn2+ and Cd2+) on the emission properties of L were studied in water. Without metal cations, L does not show any emission at basic pH values. The addition of Zn2+ leads to the production of excimer emission, which is due to a static excimer formed by direct excitation of the intramolecular ground-state dimer of the bipolar AN fragments that approach each other by Zn2+ binding. In contrast, Cd2+ addition does not result in excimer emission because the Cd2+-AN pi complex, formed by donation of a pi electron of the AN fragments to the adjacent Cd2+, suppresses pi-stacking interactions of the AN fragments. The most notable feature is the appearance of excimer emission controlled by the input sequence of metal cations: Zn2+-->Cd2+ sequential addition (each one equivalent) allows excimer emission, whereas the reverse sequence (Cd2+-->Zn2+) does not. In the Zn2+-->Cd2+ sequence, Cd2+ coordination is structurally restricted by the first Zn2+ coordination with the other polyamine bridge, leading to the formation of a weak Cd2+-AN pi complex. In contrast, for the reverse sequence, the first Cd2+ coordination forms a stable Cd2+-AN pi complex, which is not weakened by sequential Zn2+ coordination, resulting in no excimer emission. 相似文献
83.
The subject of this paper is the long distance propagation of train noise. The sound exposure level of train noise LAE was measured. To describe the results of measurements, a semi-analytical model was used. It takes into account the wave-front divergence, air absorption, ground effect, and the turbulence destroying the coherent nature of the ground effect. The model contains three adjustable parameters that must be estimated at the site. To verify the model, we performed measurements of LAE at the distance D = 450 m from the train track center. The difference between the calculated and measured mean values of LAE equals 1.3 dB. 相似文献
84.
Go Gwang Sub Lee Hong Joo Moon Dong Ju Kim Young Chul 《Research on Chemical Intermediates》2016,42(1):289-304
Research on Chemical Intermediates - In this study, we focused on the catalytic activity, stability, and kinetics of glycerol steam reforming (GSR) for the hydrogen production over... 相似文献
85.
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87.
Becerril R Gómez-Lus R Goñi P López P Nerín C 《Analytical and bioanalytical chemistry》2007,388(5-6):1003-1011
The aim of this work is the optimization and application of a group of analytical and microbiological techniques in the study
of the activity of essential oils (EOs) incorporated in a new antimicrobial packaging material and the research in depth of
the interaction between the microbial cells and the individual compounds present in the active material. For this purpose
the antimicrobial activity of the active packaging containing cinnamon or oregano was evaluated against E. coli and S. aureus. The vapour phase activity and the direct contact between the antimicrobial agents themselves, or once incorporated in the
packaging material, and the microbial cells have been studied. The direct contact was studied using a broth dilution method.
The vapour phase was evaluated by using a new method which involves the use of a filter disk containing the EOs. Furthermore,
the kill time assay was used to determine the exposure time for the maximum efficiency in packaging, and transmission electron
microscopy was used to investigate the antimicrobial activity and the possible mechanism of action against E. coli and S. aureus. Finally, the compounds absorbed by cells were identified. The results showed that the techniques used provide relevant information
about the antibacterial activity of cinnamon and oregano in direct contact as well as in the vapour phase. The antimicrobial
packaging showed a fast efficiency which supports its likely application as a food packaging material. Bacteria treated with
EOs exhibit a wide range of significant abnormalities; these include formation of blebs, coagulation of cytoplasmatic constituents,
collapse of the cell structure and lack of cytoplasmatic material. Some of these observations are correlated to the ability
of some of these substances to disrupt envelop structure, especially the inner membrane. After an extraction from dead cells,
cinnamaldehyde was detected by GC-MS in E. coli exposed to the active packaging containing cinnamon. 相似文献
88.
Calix[4]bis(thiacrown-5) (L) with 1,3-alternating conformation was employed as a strong dinucleating ligand for the soft metal ions AgI and CuI. The reaction of L with AgPF6 afforded a discrete endo-coordinated disilver(I) complex 1, [Ag2L](PF6)2. In contrast, mixed products (2a + 2b) consisting of 3D networks were obtained from the reaction of L and CuI; 2b linked with a Cu4I4 cubane unit was shown to generate photoluminescence, while 2a linked with a Cu2I2 rhomboid unit does not. 相似文献
89.
Shiraishi Y Ishizumi K Nishimura G Hirai T 《The journal of physical chemistry. B》2007,111(30):8812-8822
Fluorescence properties of a diethylenetriamine bearing two end pyrene fragments (L) have been studied in water, where effects of adding metal cations (Zn2+, Cd2+, Cu2+, Hg2+, Ag+) on the emission properties of L have been studied. Without metal cations, L shows dual-mode fluorescence consisting of monomer and excimer emissions. The monomer emission intensity (I(M)) is strong at acidic pH but decreases with a pH increase because of an electron transfer (ET) from the unprotonated nitrogen atoms to the excited pyrene fragment. The excimer emission is due to the static excimer formed via a direct photoexcitation of the intramolecular ground-state dimer (GSD) of the end pyrene fragments. The excimer emission intensity (I(E)) is weak at acidic pH but increases with a pH increase because of the GSD stability increase associated with the deprotonation of the polyamine chain. Addition of metal cations leads to I(M) decrease, where chelation-driven I(M) enhancement does not occur even with diamagnetic Zn2+ and Cd2+ at any pH. This is because a pyrene-metal cation pi-complex, formed via a donation of pi-electron of the pyrene fragment to the adjacent metal center, suppresses the monomer photoexcitation. I(E) also decreases upon addition of metal cations because the pyrene-metal cation pi-complex weakens pi-stacking interaction of the end pyrene fragments, leading to GSD stability decrease. The emission properties of L-Zn2+ complexes were studied by means of time-resolved fluorescence decay measurements, and the effects of adding a less-polar organic solvent were also studied to clarify the detailed emission properties. 相似文献
90.
用双相法提纯青虫菌(Bacillus thuringiensis var.galleriae)的晶体,碱解后免疫家兔获晶体蛋白抗体,然后用纯化的晶体感染莱青虫,半小时至1小时取中肠上皮细胞作酶标电镜观察,结果表明仅在细胞膜上看到抗原的存在。 相似文献