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Hiltrud Breitenfelder-Manske Friedrich Kohler 《Monatshefte für Chemie / Chemical Monthly》1985,116(11):1247-1261
The second virial coefficients of homonuclear three-centerLennard-Jones molecules are calculated with various parameters of the isosceles triangle connecting the three sites. A special effort is made to establish the reducedBoyle temperaturesT
B and the values of the second virial coefficients atT/T
B=0.3 for the sake of comparison with one- and two-centerLennard-Jones molecules. It is shown that it is possible to find parameter values of the interaction potential of one- and two-centerLennard-Jones molecules which give very similar values of second virial coefficients forT/T
B0.3, and the equivalence conditions are established. These conditions might not only give a basis for a microscopic scaling of state variables, but also some restrictions for the validity of the group contribution concept.Presented in part at the DFG-Colloquium at Paderborn, 19th April 1982, and at the 5th Conference on Mixtures of Nonelectrolytes and Intermolecular Interactions, April 18–22, 1983, at Halle (GDR). 相似文献
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C. A. Fyfe H. Meyer zu Altenschildesche K. C. Wong-Moon H. Grondey J. M. Chezeau 《Solid state nuclear magnetic resonance》1997,9(2-4):97-106
The framework structure of As-synthesized A1PO4-14 has been investigated with a combination of different one-dimensional 27Al and 31P solid state NMR techniques and 27Al/31P double resonance methods. The results are found to be fully consistent with the assumed structural model. 27Al MAS and DOR experiments at three different magnetic field strengths together with simulations show the presence of two tetrahedral sites, one pentacoordinated and one octahedral aluminum site. The 27Al quadrupolar coupling constants and the 31P isotropic chemical shifts of the tetrahedral sites correlate well with tetrahedral shear-strain parameters and mean P-O-A1 bond angles, respectively. These correlations allow one to assign all of the NMR resonances to specific T-sites in the proposed framework structure. The assignments are then further confirmed by the application of three different two-dimensional heteronuclear correlation methods (i.e., 27Al → 31P TEDOR, CP, and INEPT) which reveal the connectivities between AlOx and PO4 polyhedra. The two-dimensional INEPT experiment is applied here for the first time in the solid state. 相似文献
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Guido Machek Hiltrud Riezler Fritz Prior 《Monatshefte für Chemie / Chemical Monthly》1953,84(2):335-341
Zusammenfassung Es wird der Verlauf der Sulfurierung des m-Kresols auf Grund der zwei dabei gebildeten Sulfone, dem - und -m-Oxytolylsulfon vonZehenter, geklärt. Die Konstitution des -m-Oxytolylsulfons wird als die des 2,2-Dioxy-4,4-dimethyldiphenylsulfons erkannt; für das -m-Oxytolylsulfon wird die Konstitution des 4,2-Dioxy-2,4-dimethyldiphenylsulfons wahrscheinlich gemacht. 相似文献
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Enantiomers and chiral relaxation reagents (CRR) afford diastereomeric complexes, which differ clearly in their 13C spin-lattice relaxation times. 相似文献
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Charge ordering in lithium vanadium phosphates: electrode materials for lithium-ion batteries 总被引:2,自引:0,他引:2
Yin SC Grondey H Strobel P Huang H Nazar LF 《Journal of the American Chemical Society》2003,125(2):326-327
The delithiation process in monoclinic Li3V2(PO4)3 has been determined by powder neutron diffraction coupled with 7Li solid-state NMR techniques. Charge ordering of vanadium (V3+/V4+) was observed in Li2V2(PO4)3 as shown by the gray and blue V-O octahedra, respectively, indicating that the electrons are pinned in this phase and hence transport is limited. 相似文献
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Yin SC Grondey H Strobel P Anne M Nazar LF 《Journal of the American Chemical Society》2003,125(34):10402-10411
Monoclinic lithium vanadium phosphate, alpha-Li(3)V(2)(PO(4))(3), is a highly promising material proposed as a cathode for lithium-ion batteries. It possesses both good ion mobility and high lithium capacity because of its ability to reversibly extract all three lithium ions from the lattice. Here, using a combination of neutron diffraction and (7)Li MAS NMR studies, we are able to correlate the structural features in the series of single-phase materials Li(3-y)V(2)(PO(4))(3) with the electrochemical voltage-composition profile. A combination of charge ordering on the vanadium sites and lithium ordering/disordering among lattice sites is responsible for the features in the electrochemical curve, including the observed hysteresis. Importantly, this work highlights the importance of ion-ion interactions in determining phase transitions in these materials. 相似文献
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We analyze the time-dependent spectrum of eigenvalues of the correlation matrix for multivariate EEG data at the transition to epileptic seizures. By a mechanism of level repulsion between states at both edges of the spectrum of the correlation matrix, relevant information about quantitative correlation changes is reflected in the largest and smallest eigenvalues and corresponding eigenvectors. By the application of measures from random matrix theory we provide evidence that statistically relevant information can be obtained both at the upper and the lower end of the spectrum. In addition, information about spatial characteristics of correlation changes can be extracted. 相似文献
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Precht JC Ganchev B Heinkele G Brauch H Schwab M Mürdter TE 《Analytical and bioanalytical chemistry》2012,403(1):301-308
Letrozole is an efficient endocrine treatment of postmenopausal breast cancer, however, not all patients benefit from this
treatment, and moreover, severe side-effects like arthralgia frequently lead to discontinuation. To better understand inter-individual
variability in drug response and side-effects, plasma analysis of steady-state concentrations of letrozole and its major metabolites
is crucial. We developed a rapid, sensitive, and specific method for the simultaneous quantification of letrozole and its
metabolites 4,4′-(hydroxymethylene)dibenzonitrile (carbinol) and bis(4-cyanophenyl)methyl hexopyranosiduronic acid (carbinol-gluc)
by UHPLC-ESI-MS/MS using in-house synthesized, stable isotope-labeled internal standards. Following solid-phase extraction
in BondElut C18 96-well plates, the analytes were separated on a ZORBAX Eclipse XDB-C18 column (1.8 μm, 4.6 × 50 mm) with
a gradient of acetonitrile in 0.1% acetic acid in water and detected on a triple quadrupole mass spectrometer with electrospray
ionization in the multiple reaction monitoring mode. Lower limits of quantification were 20, 0.2, and 2 nM for letrozole,
carbinol, and carbinol-gluc, respectively. The assay has been validated according to FDA guidance and applied to the analysis
of 20 plasma samples of postmenopausal breast cancer patients treated with 2.5 mg of letrozole per day. Mean plasma levels
(±SD) were 366 ± 173, 0.38 ± 0.09, and 34 ± 12 nM for letrozole, carbinol, and carbinol-gluc, respectively. Our rapid and
sensitive mass spectrometry based method enables future pharmacokinetic investigations of letrozole outcome. 相似文献