Prediction of physical properties of hydrocarbon mixtures by partial-least-squares calibration of carbon-13 nuclear magnetic resonance data

By using the partial-least-squares (PLS) method, bulk properties of 12-component synthetic mixtures containing n-alkanes, iso-alkanes, cyclo-alkanes and aromatics are calibrated against intensities and chemical shifts of ¹³C-NMR spectra. The standard error of prediction (SEP) for the determinations of density, refractive index, mean molecular weight and carbon-type distribution was found to be less than 3.2% of the observed range. The SEP for excess densities is significantly larger, especially for values based on chemical shift data. The chemical shift variation supplies unique chemical information on solute/solvent interactions.     

Influence and correction of peak shift and band broadening observed by rank analysis on vibrational bands from variable-temperature measurements

Variable-temperature infrared (IR) spectra of cyclohexane and IR and Raman spectra of chlorocyclohexane have been investigated by graphic eigenvalue analysis. Thermal effects known as peak shift and band broadening combined with heteroscedastic noise in vibrational bands are found to have severe influence on the interpretation of the outcome of rank analysis. Methods for correction of frequency shifts and band broadening in the spectral profiles due to temperature variation are developed and tested.     

Final state correlation effects on the auger transition rates of methane

The doubly ionized Auger final states of CH₄ and the corresponding states of of Ne atom are studied by semi-internal configuration interaction (Cl) calculations. Correlation redistributes dramatically the intensities between the Auger diagram states and gives rise to strong satellite peaks in the law-kinetic-energy part of the spectrum.     

Visualizing information in multivariate data: Applications to petroleum geochemistry : Part 2. Interpretation and correlation of north sea oils by using three different biomarker fractions

Pentacyclic triterpanes, steranes and aromatic steroids of thirty-five North Sea crude oils are investigated for their usefulness in correlation and interpretation. Oblique components are necessary for obtaining data projections amenable to geochemical interpretation and for selecting molecular markers, i.e., compounds related to specific geochemical factors. Normoretane is shown to be a specific maturity parameter for the North Sea oils examined.