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21.
Garland R. Marshall 《Journal of computer-aided molecular design》2013,27(2):107-114
Molecular mechanics attempts to represent intermolecular interactions in terms of classical physics. Initial efforts assumed a point charge located at the atom center and coulombic interactions. It is been recognized over multiple decades that simply representing electrostatics with a charge on each atom failed to reproduce the electrostatic potential surrounding a molecule as estimated by quantum mechanics. Molecular orbitals are not spherically symmetrical, an implicit assumption of monopole electrostatics. This perspective reviews recent evidence that requires use of multipole electrostatics and polarizability in molecular modeling. 相似文献
22.
Determination of anionic surfactants during wastewater recycling process by ion pair chromatography with suppressed conductivity detection 总被引:2,自引:0,他引:2
A direct approach utilizing ion pairing reversed-phase chromatography coupled with suppressed conductivity detection was developed to monitor biodegradation of anionic surfactants during wastewater recycling through hydroponic plant growth systems and fixed-film bioreactors. Samples of hydroponic nutrient solution and bioreactor effluent with high concentrations (up to 120 mS electrical conductance) of inorganic ions can be analyzed without pretreatment or interference. The presence of non-ionic surfactants did not significantly affect the analysis. Dynamic linear ranges for tested surfactants [Igepon TC-42, ammonium lauryl sulfate, sodium laureth sulfate and sodium alkyl (C10-C16) ether sulfate] were 2 to approximately 500, 1 to approximately 500, 2.5 to approximately 550 and 3.0 to approximately 630 microg/ml, respectively. 相似文献
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Garland D. Smith Colleen E. Donelan Roland E. Barden 《Journal of colloid and interface science》1977,60(3):488-496
On the basis of conductivity and centrifugation data and visual examination, ternary phase diagrams were prepared for systems composed of hexane, water, and 2-propanol. Certain ternary compositions were shown to be oil-continuous microemulsions, even though a soap or detergent was not present. Of a number of short-chain alcohols tested, only 2-propanol and 1-propanol could stabilize a microemulsified ternary solution. Addition of a small amount of hexadecyltrimethylammonium perchlorate to the ternary solutions produced only modest changes in the ternary phase diagram. However, in the presence of hexadecyltrimethylammonium salts, most short-chain alcohols containing less than eight carbons could stabilize an oil-continuous microemulsion. 相似文献
25.
A theory is presented explaining the recently observed superconductivity at 9 °K in Pd-H and at 11 °K in Pd-D as due to the quenching of the spin-fluctuations and as due to the decrease of the Coulomb pseudo-potential μ present in Pd. That one observes for PdD a larger superconducting transition temperatureT c than for PdH is explained by the larger lattice expansion resulting for adding H to Pd. The observed non-monotonic dependence ofT c on the Hydrogen concentration is explained by the fact that approximately λ ∝N(0) for smallN(0), whereN(0) is the electronic density of states at the Fermi-energy and where λ denotes the electron-phonon coupling constant. Superconducting transition temperatures are estimated for PtH and RhH. 相似文献
26.
An a.c. calorimetric technique has been developed for high-pressure work and used for the study of chromium near its Néel transition line. Heat capacity data were obtained as a function of pressure along four isotherms. At 37·51 and 34·95°C the Cp values showed lambda-like singularities at 490 and 890 bar, respectively. At 32·60°C there was a finite cusp in Cp at a transition pressure of 1060 bar. At 27·75°C there was, surprisingly, no indication of any heat capacity anomaly at an expected transition pressure of ~2900 bar. 相似文献
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The use of entropy minimization and spectral dissimilarity is applied to three nuclear magnetic resonance (NMR) data sets. The data sets contain 2, 2, and 3 observables each. It was found that without any a priori information the sets of pure component spectra underlying the NMR spectroscopic observations could be extracted. These successful spectral resolutions suggest that a combined entropy minimization and spectral dissimilarity approach can be further developed for even larger NMR data sets containing a larger number of observables. Brief comparison to DECRA and PMF curve resolution results is also presented. 相似文献
29.
Dan Lee Leanne Leer Shara Pilch Yu Yasufuku 《Proceedings of the American Mathematical Society》2001,129(11):3193-3200
We find necessary and sufficient conditions for a complete local ring to be the completion of a reduced local ring. Explicitly, these conditions on a complete local ring with maximal ideal are (i) or , and (ii) for all , if is an integer of , then .
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