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11.
Lal V Khalizov AF Lin Y Galvan MD Connell BT Zhang R 《The journal of physical chemistry. A》2012,116(24):6078-6090
Epoxides have recently been identified as important intermediates in the gas phase oxidation of hydrocarbons, and their hydrolysis products have been observed in ambient aerosols. To evaluate the role of epoxides in the formation of secondary organic aerosols (SOA), the kinetics and mechanism of heterogeneous reactions of two model epoxides, isoprene oxide and α-pinene oxide, with sulfuric acid, ammonium bisulfate, and ammonium sulfate have been investigated using complementary experimental techniques. Kinetic experiments using a fast flow reactor coupled to an ion drift-chemical ionization mass spectrometer (ID-CIMS) show a fast irreversible loss of the epoxides with the uptake coefficients (γ) of (1.7 ± 0.1) × 10(-2) and (4.6 ± 0.3) × 10(-2) for isoprene oxide and α-pinene oxide, respectively, for 90 wt % H(2)SO(4) and at room temperature. Experiments using attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) reveal that diols are the major products in ammonium bisulfate and dilute H(2)SO(4) (<25 wt %) solutions for both epoxides. In concentrated H(2)SO(4) (>65 wt %), acetals are formed from isoprene oxide, whereas organosulfates are produced from α-pinene oxide. The reaction of the epoxides with ammonium sulfate is slow and no products are observed. The epoxide reactions using bulk samples and Nuclear Magnetic Resonance (NMR) spectroscopy reveal the presence of diols as the major products for isoprene oxide, accompanied by aldehyde formation. For α-pinene oxide, organosulfate formation is observed with a yield increasing with the acidity. Large yields of organosulfates in all NMR experiments with α-pinene oxide are attributed to the kinetic isotope effect (KIE) from the use of deuterated sulfuric acid and water. Our results suggest that acid-catalyzed hydrolysis of epoxides results in the formation of a wide range of products, and some of the products have low volatility and contribute to SOA growth under ambient conditions prevailing in the urban atmosphere. 相似文献
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The static permittivity and viscosity of glycerol–formamide (Gly–FA) binary mixtures were measured at eleven concentrations
over the entire composition range and at temperatures T=288.15, 303.15, 318.15 and 333.15 K. The excess static permittivity and excess viscosity of the mixtures were determined
using the mole-fraction additive mixture law. Results indicated that the molecular dielectric polarization in Gly–FA mixtures
is governed by 1:1 complexes with a decrease in number of H-bonded parallel aligned dipolar ordering at all of the investigated
temperatures. The 2Gly:FA complexes facilitate the viscous flow process and the number of these complexes decreases with increasing
temperature. The apparent activation energy of viscous flow, determined from Arrhenius plots, increases with increases of
the Gly concentration in the mixtures. The electric-field-induced increment of the Helmholtz free energy and the entropy of
these binary mixtures were determined from the temperature dependence of the static permittivity and its derivative, respectively. 相似文献
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An analysis of self-phase modulation (SPM) induced nonlinearities in a 40 Gbps link with chirped Gaussian pulses of different duty cycles has been reported in this paper. In the present analysis only SPM effect has been considered to control the pulse propagation behavior through the fiber by appropriate selection of pulse width, peak power and channel length to suppress the other channel impairments caused by group velocity dispersion (GVD) and third order dispersion (TOD). The effect of SPM on the Q-factor for the transmission of 40 Gbps chirped pulses with different initial pulse widths and input peak powers has been investigated. It has been observed that a wider pulse having maximum negative chirp can withstand the nonlinear effect of SPM for relatively higher ranges of input peak power. 相似文献
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The mixed-ligand complexes, [Cux,(phen)yLz] (where phen stands for 1,10-phenanthroline and L for some aliphatic acids, aromatic acids, amino acids, phenols and ethylenediamine in the ratio 1 : 1 : 1 and 1 : 2 : 1) undergo two-step, diffusion-controlled, irreversible electro-reduction in 0.5 M KNO3 at the dropping mercury electrode. The double-wave nature of these complexes may be attributed to the adsorption effect of 1,10-phenanthroline. From the characteristics of the irreversible wave, the rate constant kf, for each complex has been calculated at its formal potential. The driving force for the formation of ternary systems has been analysed. The parent complex, [Cu(phen)] is found to show a discriminating nature towards the incoming secondary ligand. Additional stability effects compared to such systems with 2,2′-bipyridyl as the parent ligand have been explained on the basis of comparatively greater π-effects of 1,10-phenanthroline. Such effects are found t o become more pronounced, due to the cooperative effect, if the secondary ligand also has a π-system. 相似文献
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Vinita Dubey A. K. Gupta S. N. Maiti 《Journal of Polymer Science.Polymer Physics》2002,40(17):1821-1827
The diffusion of sulfur mustard (SM), a chemical warfare agent, through butyl (IIR) and nitrile (NBR) rubber membranes was studied with a standard spot disc breakthrough time test at temperatures ranging from 298 to 333 K. The mechanism of diffusion was interpreted on the basis of an Arrhenius relation and dynamic adsorption theory. The permeant SM was pictured to reversibly dwell at each adsorption site for about 1.5 × 10?13 s and hop randomly through the polymer matrices in small steps, with jump lengths of the order of a picometer. A comparatively lower activation energy, a solubility parameter closer to that of SM, and a lower thermodynamic interaction parameter also contributed toward faster uptake of SM by NBR in comparison with IIR. The diffusion data were also used to derive the collision diameter of SM in these polymer matrices. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1821–1827, 2002 相似文献
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The eigen frequencies of radial pulsations of neutron stars are calculated in a strong magnetic field. At low densities we
use the magnetic BPS equation of state (EOS) similar to that obtained by Lai and Shapiro while at high densities the EOS obtained
from the relativistic nuclear mean field theory is taken and extended to include strong magnetic field. It is found that magnetized
neutron stars support higher maximum mass whereas the effect of magnetic field on radial stability for observed neutron star
masses is minimal. 相似文献