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991.
992.
Mohammad Reza Zamanloo Yaghoob Mansoori Gholam Hassan Imanzadeh Saber Taghizadeh 《Polymer Science Series B》2010,52(1-2):26-34
1,5-Naphthene dioxy diacetic acid was synthesized from the reaction of 1,5-naphthalene diol and chloroacetic acid. It was used then as a bi-functiona l monomer in polycondensation reaction with aromatic diamines in the presence of tripnenylphosphite to produce poly(amide-ether)s. All the obtained polymers were characterized by IR and elemental analysis; their solubility behaviour was evaluated in polar organic solvents as well as in concentrated H2SO4. The extent of thermal stability and phase transitions of poly(amide- ether)s were investigated by thermogravimetric analysis and differential scanning calorimetry respectively; while the morphology was estimated by X-ray powder diffraction patterns. Besides, the fu-fu stacking character of polymer chain interactions in the solid state was confirmed by absorption spectra of solid thin films. 相似文献
993.
994.
Mudasir Ahmad Tantry Reehana Khan Seema Akbar Abdul Rouf Dar Abdul Sami Shawl Mohammad Sarwar Alam 《中国化学快报》2011,22(5):575-579
An unusual oleanane triterpene(1) was isolated from aerial parts of Rhododendron campanulatum.The compound had shown prominent antibacterial and immunomodulatory activities.The structure of the compound was determined by spectroscopic data including 1D and 2D NMR spectral analysis. 相似文献
995.
Hamid Reza Memarian Asadollah Farhadi Hassan Sabzyan Mousa Soleymani 《Journal of photochemistry and photobiology. A, Chemistry》2010,209(2-3):95-103
A variety of Biginelli 5-acetyl-3,4-dihydropyrimidin-2(1H)-ones are efficiently oxidized to their corresponding pyrimidin-2(1H)-one derivatives upon UV irradiation under argon atmosphere in chloroform solution. The nature of the additional substituent on the phenyl ring located on C-4 of the heterocyclic ring influences the rate of reaction. An electron-transfer induced photoreaction is proposed based on the formation of HCl and CH2Cl2. 相似文献
996.
Giovanni Borghi Marco Polini Reza Asgari A.H. MacDonald 《Solid State Communications》2009,149(27-28):1117-1122
In single-layer graphene sheets non-local interband exchange leads to a renormalized Fermi-surface effective mass which vanishes in the low carrier-density limit. We report on a comparative study of Fermi surface effective mass renormalization in single-layer and AB-stacked bilayer graphene. We explain why the mass does not approach zero in the bilayer case, although its value is still strongly suppressed. 相似文献
997.
S. Kimiagar M. Sadegh Movahed S. Khorram M. Reza Rahimi Tabar 《Journal of statistical physics》2011,143(1):148-167
Using the Markovian method, we study the stochastic nature of electrical discharge current fluctuations in the Helium plasma.
Sinusoidal trends are extracted from the data set by the Fourier-Detrended Fluctuation analysis and consequently cleaned data
is retrieved. We determine the Markov time scale of the detrended data set by using likelihood analysis. We also estimate
the Kramers-Moyal’s coefficients of the discharge current fluctuations and derive the corresponding Fokker-Planck equation.
In addition, the obtained Langevin equation enables us to reconstruct discharge time series with similar statistical properties
compared with the observed in the experiment. We also provide an exact decomposition of temporal correlation function by using
Kramers-Moyal’s coefficients. We show that for the stationary time series, the two point temporal correlation function has
an exponential decaying behavior with a characteristic correlation time scale. Our results confirm that, there is no definite
relation between correlation and Markov time scales. However both of them behave as monotonic increasing function of discharge
current intensity. Finally to complete our analysis, the multifractal behavior of reconstructed time series using its Keramers-Moyal’s
coefficients and original data set are investigated. Extended self similarity analysis demonstrates that fluctuations in our
experimental setup deviates from Kolmogorov (K41) theory for fully developed turbulence regime. 相似文献
998.
Alkyl halides are efficiently converted to their corresponding nitroalkanes under mild and nonaqueous conditions by using polymer supported nitrites. The polymeric reagent is regenerable. 相似文献
999.
Application of Monte Carlo simulation method to polymerization kinetics over Ziegler–Natta catalysts
In the current work, the Monte Carlo simulation method was applied to ethylene polymerization over Ziegler–Natta catalysts. As expected, polymerization over each center of a Ziegler–Natta catalyst leads to a polymer having a Schultz–Flory molecular weight distribution. Notwithstanding, the total molecular weight distribution obtained by all catalyst centers together is at least twice as broad as that of each center. As another interesting finding, the introduction of hydrogen to the reaction deactivates the catalyst active centers and thereby reduces the catalyst activity. Nevertheless, it does not mainly affect the polymerization kinetics. In addition, the polymer molecular weight falls as hydrogen is added to the reaction since it acts as a strong transfer agent. The same effect is seen when cocatalyst concentration increases. Hydrogen also widens the polymer molecular weight distribution. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 41: 45–56, 2009 相似文献
1000.
Atif Fazal Sahar Al-Fayez Laila H. Abdel-Rahman Zaki S. Seddigi Abdul Rahman Al-Arfaj Bassam El Ali Mohammad A. Dastageer Mohammad A. Gondal Mohammed Fettouhi 《Polyhedron》2009,28(18):4072-4076
New copper(I) mixed-ligand complexes 1–4 of the formula Cu(N–N)PR3X, where N–N = 1,10-phenanthroline (phen), 2,2′-bipyridine (bpy), 5,5′-dimethyl-2,2′-bipyridine (5,5′dimbpy) and PR3 = tricyclohexylphosphine, tris(2-cyanoethyl)phosphine and isopropyldiphenylphosphine, have been synthesized. The complexes were characterized by EA, IR, NMR and single crystal X-ray diffraction. The solution fluorescence emission spectra were measured. The single crystal X-ray analysis showed that the copper(I) ion is four-coordinate with a distorted tetrahedral geometry. The complexes catalyze the formation of diphenylacetylene from the coupling of halobenzene with phenylacetylene. The complex Cu(5,5′-dimethylbpy)P{(cyhexyl)3}I showed the highest catalytic activity. At room temperature all four complexes exhibit, in dichloromethane, emission maxima in the 329–344 nm range, corresponding to intra-ligand excited states. 相似文献