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81.
82.
Single-stranded DNA wrap helically around individual single-walled carbon nanotubes to form DNA/CNT hybrids, which are both stable and dispersible in aqueous solution. Subjected to ion-exchange chromatography, a hybrid elutes at an ionic strength that depends on the electronic character and diameter of the core nanotube, thus providing a mechanism for separating nanotubes by chirality. We present a theoretical model for this separation process that explains all the salient features observed experimentally to date, and provides accurate predictions for critical elution salt concentration. The competition between adsorption on the stationary phase and counterion condensation in the mobile phase is characterized by estimating the difference in free energy between the two states of the hybrid. Parametric study of the DNA wrapping geometry, SWNT dielectric properties, hybrid length, and diameter indicate that the elution is most sensitive to the hybrid's effective charge density, primarily governed by the DNA helical pitch. The model correctly predicts hybrids with metallic nanotubes are weaker binding than hybrids with semiconducting nanotubes and larger diameter nanotubes are eluted at later times. 相似文献
83.
Constantine Mavroyannis 《Chemical physics letters》1978,56(2):263-266
It is shown that the excitation spectrum of neutral molecules physisorbed on a dielectric surface consists of two symmetric and two antisymmetric energy modes. The spectral functions of these modes are represented respectively by two lorentzian lines whose spectral widths are described by the radiative decay of the energy modes in question. Numerical results are derived for the energies of excitation and spectral widths for the rare-gas atoms adsorbed on graphite. 相似文献
84.
A microemulsion electrokinetic chromatographic (MEEKC) method was developed for the separation of six catechins, specific marker phytochemicals of Cistus species. The MEEKC method involved the use of sodium dodecyl sulfate (SDS) as surfactant, heptane as organic solvent and butan-1-ol as co-solvent. In order to have a better stability of the studied catechins, the separation was performed under acidic conditions (pH 2.5 phosphate buffer). The effects of SDS concentration and of the amount of organic solvent and co-solvent on the analyte resolution were evaluated. The optimized conditions (heptane 1.36% (w/v), SDS 2.31% (w/v), butan-1-ol 9.72% (w/v) and 50 mM sodium phosphate buffer (pH 2.5) 86.61% (w/v)) allowed a useful and reproducible separation of the studied analytes to be achieved. These conditions provided a different separation profile compared to that obtained under conventional micellar electrokinetic chromatography (MECK) using SDS. The method was validated and applied to the determination of catechin and gallocatechin in lyophilized extracts of Cistus incanus and Cistus monspeliensis. 相似文献
85.
The late-3d transition-metal diatomic fluorides MF = FeF, CoF, NiF, and CuF have been studied using variational multireference (MRCI) and coupled-cluster [RCCSD(T)] methods, combined with large to very large basis sets. We examined a total of 35 (2S+1)|Lambda| states, constructing as well 29 full potential energy curves through the MRCI method. All examined states are ionic, diabatically correlating to M(+)+F(-)((1)S). Notwithstanding the "eccentric" character of the 3d transition metals and the difficulties to accurately be described with all-electron ab initio methods, our results are, in general, in very good agreement with available experimental numbers. 相似文献
86.
87.
David Bookin Carl A. Constantine John W. Root James T. Muckerman 《Chemical physics letters》1983,101(1):23-28
New analytic reaction cross-section functions are reported for hot 18F atoms reacting with H2, HD and D2. A realistic model is proposed for the total non-reactive cross section in these systems throughout the center-of-mass collision energy range 0–100 eV. 相似文献
88.
89.
Constantine John Falliers 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(8):1271-1278
Superior intelligence, creative genius, extraordinary personality, and/or social prominence have been associated with asthma often enough to raise the question of a nonrandom concurrence. With no intent to prove any developmental correlation this article presents such “case reports” (more biographical than biological) for two main reasons: to document the experience of asthma in the life of outstanding persons and to make everyone better acquainted-using asthma as an “excuse”-with the work and the times of some unique human beings. 相似文献
90.