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W. Hiltner H. A. Freye R. J. Fosbinder J. W. Schoonover M. Kilpatrick E. F. Chase L. C. Riesch A. Janke F. Sekera G. F. Davidson J. O. Burton H. Matheson S. F. Acree G. Haugaard F. L. Vodret F. Hovorka W. C. Dearing T. Mikawa E. Newbery A. Itano S. Arakawa T. R. Ball W. B. Schmidt K. S. Bergstresser E. Vellinger A. E. Lorch F. Lux W. von Brehmer M. Déribéré A. F. Peters und A. Osol 《Fresenius' Journal of Analytical Chemistry》1935,103(7-8):285-292
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Asphaltenes from four different crude oils (Arab Heavy, B6, Canadon Seco, and Hondo) were fractionated in mixtures of heptane and toluene and analyzed chemically, by vapor pressure osmometry (VPO), and by small angle neutron scattering (SANS). Solubility profiles of the asphaltenes and their subfractions indicated strong cooperative asphaltene interactions of a particular subfraction that is polar and hydrogen bonding. This subfraction had lower H/C ratios and modestly higher N, V, Ni, and Fe contents than the less polar and more soluble subfraction of asphaltenes. VPO and SANS studies indicated that the less soluble subfractions formed aggregates that were considerably larger than the more soluble subfractions. In general, asphaltene aggregate size increased with decreasing solvent aromaticity up to the solubility limit, beyond which the aggregate size decreased with heptane addition. The presence of a low wavevector Q feature in the scattering curves at 25 degrees C indicated that the individual aggregates were flocculating; however, the intensity of the feature was diminished upon heating of the samples to 80 degrees C. The solubility mechanism for Canadon Seco asphaltenes, the largest aggregate formers, appears to be dominated by aromatic pi-bonding interactions due to their low H/C ratio and low nitrogen content. B6 and Hondo asphaltenes formed similar-sized aggregates in heptol and the solubility mechanism is most likely driven by polar interactions due to their relatively high H/C ratios and high nitrogen contents. Arab Heavy, the least polar asphaltene, had a H/C ratio similar to Canadon Seco but formed the smallest aggregates in heptol. The enhancement in polar and pi-bonding interactions for the less soluble subfraction indicated by elemental analysis is reflected by the aggregate size from SANS. The less soluble asphaltenes contribute the majority of species responsible for aggregation and likely cause many petroleum production problems such as pipeline deposition and water-in-oil emulsion stabilization. 相似文献
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Effects of petroleum resins on asphaltene aggregation and water-in-oil emulsion formation 总被引:4,自引:0,他引:4
P. Matthew Spiecker Keith L. Gawrys Chad B. Trail Peter K. Kilpatrick 《Colloids and surfaces. A, Physicochemical and engineering aspects》2003,220(1-3):9-27
Asphaltenes from four crude oils were fractionated by precipitation in mixtures of heptane and toluene. Solubility profiles generated in the presence of resins (1:1 mass ratio) indicated the onset of asphaltene precipitation occurred at lower toluene volume fractions (0.1–0.2) than without resins. Small-angle neutron scattering (SANS) was performed on solutions of asphaltene fractions in mixtures of heptane and toluene with added resins to determine aggregate sizes. Water-in-oil emulsions of asphaltene–resin solutions were prepared and separated by a centrifuge method to determine the vol.% water resolved. In general, the addition of resins to asphaltenes reduced the aggregate size by disrupting the π–π and polar bonding interactions between asphaltene monomers. Interaction of resins with asphaltenic aggregates rendered the aggregates less interfacially active and thus reduced emulsion stability. The smallest aggregate sizes observed and the weakest emulsion stability at high resin to asphaltene (R/A) ratios presumably corresponded to asphaltenic monomers or small oligomers strongly interacting with resin molecules. It was often observed that, in the absence of resins, the more polar or higher molecular weight asphaltenes were insoluble in solutions of heptane and toluene. The addition of resins dissolved these insolubles and aggregate size by SANS increased until the solubility limit was reached. This corresponded approximately to the point of maximum emulsion stability. Asphaltene chemistry plays a vital role in dictating emulsion stability. The most polar species typically required significantly higher resin concentrations to disrupt asphaltene interactions and completely destabilize emulsions. Aggregation and film formation are likely driven by polar heteroatom interactions, such as hydrogen bonding, which allow asphaltenes to absorb, consolidate, and form cohesive films at the oil–water interface. 相似文献
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T.M. Semkow D.K. Haines S.E. Beach B.J. Kilpatrick A.J. Khan K. O'Brien 《Physics letters. [Part B]》2009
Several older and recent reports provided evidence for the oscillatory character of the exponential decay law in radioactive decay and attempted to explain it with basic physics. We show here that the measured effects observed in some of the cases, namely in the decay of 226Ra, 32Si in equilibrium, and 36Cl, can be explained with the temperature variations. 相似文献
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Kilpatrick LE Neta P Yang X Simón-Manso Y Liang Y Stein SE 《Journal of the American Society for Mass Spectrometry》2012,23(4):655-663
Tandem mass spectra of peptide ions, acquired in shotgun proteomic studies of selected proteins, tissues, and organisms, commonly
include prominent peaks that cannot be assigned to the known fragmentation product ions (y, b, a, neutral losses). In many
cases these persist even when creating consensus spectra for inclusion in spectral libraries, where it is important to determine
whether these peaks represent new fragmentation paths or arise from impurities. Using spectra from libraries and synthesized
peptides, we investigate a class of fragment ions corresponding to yn-1 + 10 and yn-1 + 11, where n is the number of amino acid residues in the peptide. These 10 and 11 Da differences in mass of the y ion were
ascribed before to the masses of [+ CO – H2O] and [+ CO – NH3], respectively. The mechanism is suggested to involve dissociation of the N-terminal residue at the CH-CO bond following
loss of H2O or NH3. MS3 spectra of these ions show that the location of the additional 10 or 11 Da is at the N-terminal residue. The yn-1 + 10 ion is most often found in peptides with N-terminal proline, asparagine, and histidine, and also with serine and threonine
in the adjacent position. The yn-1 + 11 ion is observed predominantly with histidine and asparagine at the N-terminus, but also occurs with asparagine in positions
two through four. The intensities of the yn-1 + 10 ions decrease with increasing peptide length. These data for yn-1 + 10 and yn-1 + 11 ion formation may be used to improve peptide identification from tandem mass spectra. 相似文献
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A. Leclère A. Hahn A. Kretschmann C. Du Rietz S. Hähnel Dr. N. Gerbers Co. m. b. H F. Tödt L. S. Foster I. J. Gruntfest M. Déribéré L. J. Desha R. E. Sherrill L. M. Harrison G. Kloz H. Leonhardt N. Bjerrum G. S. Hartley W. B. Fortuno M. G. Mellon I. M. Kolthoff L. S. Guss H. Eichler H. Gorke E. Köppe F. Staiger A. Thiel F. W. Panepinto M. Kilpatrick T. Teorell E. Stenhagen W. L. German 《Analytical and bioanalytical chemistry》1939,116(9-10):336-347