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231.
Galina Ya. Popova Galina Ya. Popova Tamara V. Andrushkevich Tamara V. Andrushkevich Yuriy A. Chesalov Yuriy A. Chesalov Elena V. Ovchinnikova Elena V. Ovchinnikova 《Reaction Kinetics and Catalysis Letters》2006,87(2):387-394
Summary In situFTIR spectroscopy was used to study the interaction of<span style='font-family:Symbol;mso-bidi-font-family:Symbol'>b-picoline
with the surface of a V-Ti-O catalyst in the temperature range of 120-300°C.b-picoline was found to react with the Lewis acid
sites of the catalyst to form a nitrogen-coordinated complex. This complex turns into an aldehyde-like complex at</o:p>150-250°C
and then into a nicotinate, which is a direct precursor of nicotinic acid.</o:p> 相似文献
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233.
R. Bielski J. M. J. Frchet J. V. Fusco K. W. Powers H. C. Wang 《Journal of polymer science. Part A, Polymer chemistry》1993,31(3):755-762
The crosslinking chemistry of a new elastomer based on brominated poly(isobutylene-co-4-methylstyrene) has been investigated using model compounds. In order to mimic the conditions that prevail within the highly allphatic rubber, the study was carried out in mineral oil using catalysts that are compatible with such low polarity media. Electrophilic aromatic substitution reactions occur in a system consisting of p-isopropylbenzyl bromide and p-isopropyl toluene in the presence of zinc oxide and zinc stearate. The reaction proceeds after a significant induction period while no induction period is seen for a similar reaction with zinc bromide as the catalyst. The in situ formation of reactive species containing Zn? Br bonds appears to be an important step in the overall process. The stoichiometric ratio of zinc salt to benzylic bromide is important. High ratios lead to the accumulation of benzylic stearate or benzylic alcohol in the system which retards the alkylation reaction. The model study emphasizes the importance of stoichiometry of reagents in this reaction and provides insight into the crosslinking mechanism. © 1993 John Wiley & Sons, Inc. 相似文献
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236.
Zsolt Keresztessy Magdolna Bodnár Elizabeth Ber István Hajdu Min Zhang John F. Hartmann Tamara Minko János Borbély 《Colloid and polymer science》2009,287(7):759-765
For the purpose of targeted drug delivery, composite biodegradable nanoparticles were prepared from chitosan and the poly-γ-glutamic
acid via an ionotropic gelation process. These stable self-assembled nanoparticles were characterized by dynamic light scattering,
transmission electron microscopy, and atomic force microscopy, which demonstrated that the nanosystem consists of spherical
particles with a smooth surface both in aqueous environment and in dried state. Toxicity measurements showed that the composition
is nontoxic when tested either on cell cultures or in animal feeding experiments. To evaluate the potential of the nanosystem
for intracellular drug delivery, the nanoparticles were fluorescently labeled and folic acid was attached as a cancer cell-specific
targeting moiety. The ability of the particles to be internalized was tested using confocal microscopic imaging on cultured
A2780/AD ovarian cancer cells, which overexpress folate receptors. The quantitative data obtained by digital processing of
the intensity of green color of each pixel in the pictures inside the cell boundaries and total intensity of fluorescence
inside the cells showed that “targeted” particles internalized into the cells significantly faster and the total accumulation
of these particles was substantially higher in the cancer cells when compared with “nontargeted” particles, which may facilitate
effective and specific cytoplasmic delivery of anticancer agents loaded into such nanoparticles.
Zsolt Keresztessy and Magdolna Bodnár contributed equally to this work. 相似文献
237.
Dejan Poleti Ljiljana Karanovi Tamara ?ordjevi Katarina ?uri 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(9):m355-m357
Sodium citrate dihydrate doped with Mn3+ ions, namely trisodium(I) managnese(III) citrate(3−) dihydrate, [Na3Mn0.011(C6H5O7)(H2O)2]n, was obtained during attempts to prepare some complex MnIII citrates from a concentrated strong alkaline solution containing Na+, Mn3+ and citrate ions. The compound is isostructural with the recently described Na3(C6H5O7)·2H2O [Fischer & Palladino (2003). Acta Cryst. E 59 , m1080–m1082]. The essential difference between these two structures is the presence of a very small proportion (0.205 wt%) of Mn3+ ions, which are positioned at the special 4e Wyckoff position in C2/c, where they are in a highly distorted octahedral environment of O atoms from two citrate anions. 相似文献
238.
A new approach for determination of refractive index dispersion n(λ) (the real part of the complex refractive index) and thickness d of thin films of negligible absorption and weak dispersion is proposed. The calculation procedure is based on determination
of the phase thickness of the film in the spectral region of measured transmittance data. All points of measured spectra are
included in the calculations. Barium titanate thin films are investigated in the spectral region 0.38–0.78 μm and their n(λ) and d are calculated. The approach is validated using Swanepoel’s method and it is found to be applicable for relatively thin films
when measured transmittance spectra have one minimum and one maximum only.
相似文献
239.
Vakul'skaya TI Titova IA Dolgushin GV Lopyrev VA 《Magnetic resonance in chemistry : MRC》2005,43(12):1023-1027
The primary radical anions of substrate in the reactions of vicarious nucleophilic substitution of hydrogen in 1-methyl-4-nitropyrazole with 1,1,1-trimethylhydrazinium iodide and 4-amino-1,2,4-triazole in t-BuOK-DMSO were observed and identified by EPR monitoring. The probable mechanism of the substrate radical anions formation is discussed. 相似文献
240.
Microlaser-pumped periodically poled lithium niobate optical parametric generator-optical parametric amplifier 总被引:2,自引:0,他引:2
For what is believed to be the first time, a single-longitudinal-mode passively Q-switched Nd:YAG microlaser is used to pump a narrow-bandwidth periodically poled lithium niobate (PPLN) optical parametric generator-optical parametric amplifier (OPG-OPA). Before amplification in the OPA, the output of the OPG stage was spectrally filtered with an air-spaced etalon, resulting in spectroscopically useful radiation (bandwidth, ~0.05 cm(-1) FWHM) that was tunable in 15-cm(-1) segments anywhere in the signal range 6820-6220 cm(-1) and the idler range 2580-3180 cm(-1). The ability to pump an OPG-OPA with compact, high-repetition-rate, intrinsically narrow-bandwidth microlasers is made possible by the high gain of PPLN. The result is a tunable light source that is well suited for use in portable spectroscopic gas sensors. 相似文献