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91.
Logan JL Masse P Dorvel B Skolnik AM Sheiko SS Francis R Taton D Gnanou Y Duran RS 《Langmuir : the ACS journal of surfaces and colloids》2005,21(8):3424-3431
A series of three-arm star block copolymers were examined using atomic force microscopy (AFM). These stars consisted of a polystyrene core composed of ca. 111 styrene units/branch with poly(ethylene oxide) (PEO) chains at the star periphery. Each star contained different amounts of PEO, varying from 107 to 415 ethylene oxide units/branch. The stars were spread as thin films at the air/water interface on a Langmuir trough and transferred onto mica at various surface pressures. Circular domains representing 2D micelle-like aggregated molecules were observed at low pressures. Upon further compression, these domains underwent additional aggregation in a systematic manner, including micellar chaining. At this point, domain area and the number of molecules/domain increased with increasing pressure. In addition, it was found that longer PEO chains led to greater intermolecular separation and less aggregation. These AFM results correspond to attributes seen in the surface pressure-area isotherms of the stars. In addition, they demonstrate the viability of AFM as a quantitative characterization technique. 相似文献
92.
V. V. Shchepin N. Yu. Russkikh D. V. Uzun P. S. Silaichev 《Russian Journal of Organic Chemistry》2005,41(1):131-133
Zinc enolates derived from 1-aryl-2,2-dibromoalkanones react with 3-(2-oxo-2H-chromen-3-ylcarbonyl)-2H-chromen-2-one to give 1-alkyl-1-aroyl-1a-(2-oxo-2H-chromen-3-ylcarbonyl)-1a, 7b-dihydrocyclopropa[c]-chromen-2(1H)-ones as a single stereoisomer.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 1, 2005, pp. 131–133.Original Russian Text Copyright © 2005 by Shchepin, Russkikh, Uzun, Silaichev. 相似文献
93.
Frankamp BL Uzun O Ilhan F Boal AK Rotello VM 《Journal of the American Chemical Society》2002,124(6):892-893
Polystyrene-based diblock copolymers, featuring diaminotriazine functionality on one of the blocks were used to assemble complementary uracil-functionalized nanoparticles into micellar aggregates. The size of these self-assembled aggregates was controlled by block length, as determined in solution (using dynamic light scattering), and in thin films (using transmission electron microscopy). 相似文献
94.
G. Ozek T. Ozek K. H. C. Baser E. Hamzaoglu A. Duran 《Chemistry of Natural Compounds》2007,43(6):667-671
The component composition of essential oils produced by steam distillation from flower heads, leaves, and stems of Salvia anatolica (Lamiaceae), a recently described new species endemic from Turkey, was studied by GC/FID and GC/MS. A total of 127 volatile
components representing 96% of the oil was identified in essential oil from flower heads and leaves. It was found that the
principal oil components of flower heads and leaves were α-pinene (10.9%), β-pinene (6.7%), α-copaene (6.3%), heptacosane (6.2%), and hexadecanoic acid (5.0%). A total of 109 volatile compounds representing 87.9% of
the oil was characterized in essential oil isolated from stems. The principal oil components of stems were identified as hexadecanoic
acid (27.2%), tetradecanoic acid (15.2%), dodecanoic acid (5.5%), and α-copaene (5.0%).
__________
Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 552–555, November–December, 2007. 相似文献
95.
Celal Duran Mustafa Soylak Volkan Numan Bulut Ali Gundogdu Mehmet Tufekci Latif Elci Hasan Basri Senturk 《中国化学会会志》2007,54(3):625-634
A method for speciation of Cr(III) and Cr(VI) in real samples has been developed. Cr(VI) has been separated from Cr(III) and preconcentrated as its pyrrolidinedithiocarbamate (APDC) complex by using a column containing Amberlite XAD–2000 resin and determined by FAAS. Total chromium has also been determined by FAAS after conversion of Cr(III) to Cr(VI) by oxidation with KMnO4. Cr(III) has been calculated by subtracting Cr(VI) from the total. The effect of pH, flow‐rate, adsorption and batch capacity and effect of various metal cations and salt anions on the sorption onto the resin were investigated. The adsorption is quantitative in the pH range of 1.5–2.5, and Cr(VI) ion was desorbed by using H2SO4 in acetone. The recovery of Cr(VI) was 97 ± 4 at a 95% confidence level. The highest preconcentration factor was 80 for a 200 mL sample volume. The adsorption and batch capacity of sorbent were 7.4 and 8.0 mg g?1 Cr(VI), respectively, and loading half time was 5.0 min. The detection limit of Cr(VI) is 0.6 μg/L. The procedure has been applied to the determination and speciation of chromium in stream water, tap water, mineral spring water and spring water. Also, the proposed method was applied to total chromium preconcentration in microwave digested moss and rock samples with satisfactory results. The developed method was validated with CRM‐TMDW‐500 (Certified Reference Material Trace Metals in Drinking Water) and BCR‐CRM 144R s (Certified Reference Material Sewage Sludge, Domestic Origin) and the results obtained were in good agreement with the certified values. The relative standard deviations were below 6%. 相似文献
96.
Poater J Fradera X Duran M Solà M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(2):400-406
This work introduces a new local aromaticity measure, defined as the mean of Bader's electron delocalization index (DI) of para-related carbon atoms in six-membered rings. This new electronic criterion of aromaticity is based on the fact that aromaticity is related to the cyclic delocalized distribution of pi-electrons. We have found that this DI and the harmonic oscillator model of aromaticity (HOMA) index are strongly correlated for a series of six-membered rings in eleven planar polycyclic aromatic hydrocarbons. The correlation between the DI and the nucleus-independent chemical shift (NICS) values is less remarkable, although in general six-membered rings with larger DI values also have more negative NICS indices. We have shown that this index can also be applied, with some modifications, to study of the aromaticity in five-membered rings. 相似文献
97.
Miquel Sol Jordi Mestres Josep M. Oliva Miquel Duran Ramon Carb 《International journal of quantum chemistry》1996,58(4):361-372
Exact quantum molecular overlaplike and Coulomb-like self-similarity measures are studied in a selected series of molecules with the same number of electrons. It is found that quantum molecular overlap self-similarity measures can be used to estimate the concentration of electronic charge in molecules. A good linear relationship between the overlap self-similarity measure and the volume is found for molecules with the same number of electrons when the atoms of the systems being compared belong to the same row of the periodic table. Finally, an upper bound for the quantum molecular overlap self-similarity measure of molecules with a number of electrons up to 54 is given from the atomic quantum self-similarity measures obtained using Slater-type functions. © 1996 John Wiley & Sons, Inc. 相似文献
98.
Antonio J. Duran 《Journal of Approximation Theory》1999,100(2):2239
Ratio asymptotic results give the asymptotic behaviour of the ratio between two consecutive orthogonal polynomials with respect to a positive measure. In this paper, we obtain ratio asymptotic results for orthogonal matrix polynomials and introduce the matrix analogs of the scalar Chebyshev polynomials of the second kind. 相似文献
99.
Zexing Cao Miquel Sol Hui Xian Miquel Duran Qianer Zhang 《International journal of quantum chemistry》2001,81(2):162-168
Hybrid density functional theory calculations on the structures, vibrational frequencies, electron binding and dissociation energies, and bonding properties of CuO$_{3}^{-}$ and CuO3 species have been carried out. Stable isomers containing an O3 subunit and composed of O2 bound to CuO have been located on the potential energy hypersurfaces of CuO$_{3}^{-}$ and CuO3. The isomers formed by O2 bonded to CuO in side‐on and end‐on coordination are more stable than those containing an O3 subunit. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 81: 162–168, 2001 相似文献
100.
Cemil Aydoğan Fatma Yılmaz Duygu Çimen Lokman Uzun Adil Denizli 《Electrophoresis》2013,34(13):1908-1914
A new type of polymethacrylate‐based monolithic column with chiral stationary phase was prepared for the enantioseparation of aromatic amino acids, namely d ,l ‐phenylalanine, d ,l ‐tyrosine, and d ,l ‐tryptophan by CEC. The monolithic column was prepared by in situ polymerization of butyl methacrylate (BMA), N‐methacryloyl‐l ‐histidine methyl ester (MAH), and ethylene dimethacrylate (EDMA) in the presence of porogens. The porogen mixture included DMF and phosphate buffer. MAH was used as a chiral selector. FTIR spectrum of the polymethacrylate‐based monolith showed that MAH was incorporated into the polymeric structure via in situ polymerization. Some experimental parameters including pH, concentration of the mobile phase, and MAH concentration with regard to the chiral CEC separation were investigated. Single enantiomers and enantiomer mixtures of the amino acids were separately injected into the monolithic column. It was observed that l ‐enantiomers of aromatic amino acids migrated before d ‐enantiomers. The reversal enantiomer migration order for tryptophan was observed upon changing of pH. Using the chiral monolithic column (100 μm id and 375 μm od), the best chiral separation was performed in 35:65% ACN/phosphate buffer (pH 8.0, 10 mM) with an applied voltage of 12 kV in CEC. SEM images showed that the chiral monolithic column has a continuous polymeric skeleton and large through‐pore structure. 相似文献