A styrene-butadiene copolymer is filled with mixtures of pyrogenic silica combined with a silane coupling agent and fibers of organophilic sepiolite. The mechanical properties of the composites reveal that a mixture of double fillers impart to the elastomeric matrix a higher degree of reinforcement than that which would result from a simple addition of the two types of fillers. The swelling ratio of the composite containing the two types of fillers was found to highly decrease with regard to the pure polymer reflecting strong interactions with the matrix. The changes in the state of dispersion by adding the second filler were evaluated by transmission electron microscopy. 相似文献
Ion/molecule reactions of +CH2OCH2. with alpha-dicarbonyl compounds were performed via pentaquadrupole mass spectrometry. Besides the previously known [3+ + 2] 1,3-cycloaddition reaction that forms cyclic 1,3-dioxonium ions, an unprecedented reaction proceeding formally by [4 + 1+] cycloaddition of ionized methylene (CH2+.) to the alpha-dicarbonyl compounds occurs competitively, leading to the gas-phase synthesis of several ionized 2-unsubstituted 1,3-dioxoles. This novel cycloaddition reaction may therefore be added to the set of methods available for the synthesis of 1,3-dioxoles. 相似文献
A series of novel pyrrolo-allocolchicine derivatives (containing a 1-methyl-1H-indol-5-yl moiety replacing ring?C) was synthesized. The tetracyclic ring system was constructed by Suzuki-Miyaura cross-coupling of a 1-methylindole-5-boronate with an ortho-iodo-dihydrocinnamic acid derivative and subsequent intramolecular Friedel-Crafts acylation. After reduction of the resulting ketone, the nitrogen functionality was introduced in a Mitsunobu-type reaction by using zinc azide followed by LiAlH(4) reduction. Structural assignments were supported by X-ray crystallography. The compounds synthesized were then tested against BJAB tumor cells and found to exhibit pronounced cytotoxic activity (proliferation inhibition and apoptosis induction). The ketone 24?b was even active at sub-nanomolar concentration. In addition, the antitumor potential of the compounds was confirmed by using B lymphoid cell lines. 相似文献
NMRP is a controlled polymerization technique with the ability to produce polymers with a highly controlled microstructure. The properties of the thus obtained polymers make it desirable to scale this technique to an industrial level, but there are still some challenges to be faced, e.g., to develop emulsion NMRP at low temperatures (lower than about 100 °C) with inexpensive, commercially available nitroxides such as TEMPO. Here, the emulsion NMRP of styrene using TEMPO at temperatures lower than 100 °C is described. An optimal control of molecular weights and polydispersities and a fast polymerization rate are obtained.
Today, an alarming rise of bacterial gastroenteritis in humans resulting from consuming Campylobacter-tainted foods is being observed. One of the solutions for mitigating this issue may be the antibacterial activity of essential oils. In the present research, we propose to study the antibacterial activity against Campylobacter and other Gram-negative bacteria of Daucus carota essential oil and its active molecules. In addition, a few chemically synthesized molecules such as (E)-methylisoeugenol, Elemicin, and eugenol were also studied. The results showed that the essential oil itself and its most active component, (E)-methylisoeugenol, exhibited bactericidal effects. Similar effects were detected using purified and chemically synthesized molecules. Also, it was observed that the Daucus carota essential oil and its active molecules affected intracellular potassium and intracellular ATP contents in Campylobacter cells. Inhibition of the membrane bound FOF1-ATPase was also observed. Eventually, for the first time, the efflux mechanism of active molecules of Daucus carota essential oil was also identified in gamma proteobacteria and its specific antibacterial activity against Campylobacter jejuni was associated with the lack of this efflux mechanism in this species. 相似文献
The reactions between titanium alkoxides Ti(OR)4 (R = Et,i Pr) and strontium -diketonates Sr(-dik)2 (-dik = thd, acac) were investigated. The various Sr-Ti species, Sr2Ti2(-dik)4 (OR)8, have a 1:1 Sr:Ti stoichiometry and were characterized by elemental analysis, FT-IR and by single-crystal X-ray diffraction for Sr2Ti2(3-OiPr)2 (-OiPr)4 (OiPr)2(thd)4 (1). The hydrolysis-polycondensation reactions of the various species were investigated and the resulting powders analyzed by light scattering and XRD. While acetone was found to have little influence on the hydrolysis reactions of the Sr-Ti species, polycondensation of Ti(OiPr)4 in neat acetone offers a trinuclear enolate Ti(3-O)2(OCMe=CH2)3 (OiPr)5(iPrOH) (4). Comparisons between the Ba-Ti and Sr-Ti systems are given. 相似文献