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Calcified heart valves display a significant imbalance in tissue content of trace and essential elements. The valvular calcification is an age-related process and there are data suggesting involvement of lipids. We studied elemental composition and lipid distribution in three distinct regions of calcified human aortic valves, representing successive stages of the calcific degeneration: normal, thickened (early lesion) and calcified (late lesion), using SR-μXRF (Synchrotron Radiation Micro X-Ray Fluorescence) for elemental composition and Oil Red O (ORO) staining for demonstration of lipids. Two-dimensional SR-μXRF maps and precise point spectra were compared with histological stainings on consecutive valve sections to prove topographical localization and colocalization of the examined elements and lipids. In calcified valve areas, accumulation of calcium and phosphorus was accompanied by enhanced concentrations of strontium and zinc. Calcifications preferentially developed in lipid-rich areas of the valves. Calcium concentration ratio between lipid-rich and lipid-free areas was not age-dependent in early lesions, but showed a significant increase with age in late lesions, indicating age-dependent intensification of lipid involvement in calcification process. The results suggest that mechanisms of calcification change with progression of valve degeneration and with age. [ABSTRACT FROM AUTHOR]

Abstract: The definition of kerogen as the insoluble fraction of sedimentary organic matter leads to the assumption that all of its chemical constituents are autochthonous. Evidence is presented that some of the organic N in kerogen derives from allochthonous mobile and chemically reactive N species (e.g., ammonium, HCN and low molecular weight organic N containing compounds) that are delivered by migrating fluids to stationary kerogen. Reactions of humic compounds (e.g., protokerogen) with ammonium in soil and sediment are facilitated biologically. At higher temperatures, reactions between kerogen in rocks and N containing compounds in mobile fluids are driven geochemically. N isotopic exchange between kerogen and or NH3 is evident from experiments where 15N enriched ammonium chloride solutions and source rocks containing kerogen types I, II, IIS and III were heated over 5 years at temperatures of 100, 144 and 196°C. The resulting data corroborate earlier results from hydrous pyrolysis experiments (330°C for up to 144h) and prove that ammonium is readily converted abiogenically to organic N in kerogen at temperatures that approach those in naturally maturing sediments. The propensity of different types of kerogen to react with or NH3 increases in the order II

Abstract: A series of Late Devonian to Early Mississippian type II kerogens with vitrinite reflectance values R o 0.29–2.41% were analyzed using py-GC–MS. In addition, a low maturity kerogen with R o 0.44% was separated into fractions via density gradient centrifugation, followed by py-GC–MS of the alginite and amorphinite maceral concentrates. Alkylbenzenes and n-alk-1-ene/n-alkane doublets represented the main compound classes identified in all pyrolysates. The pyrolysate from alginite featured 1,2,4-trimethylbenzene and toluene as the two most prominent alkylbenzenes. In contrast, alkylbenzenes in pyrolysates from amorphinite and low maturity bulk kerogens with R o 0.29–0.63% were dominated by 1,2,3,4-tetramethylbenzene. With increasing thermal maturity, pyrolysates were increasingly dominated by (i) alkylbenzenes with fewer methyl groups, namely by tri- and dimethylbenzenes at medium maturity (R o 0.69–1.19%), and (ii) by toluene at higher maturity (R o 1.30–2.41%). With increasing maturity of kerogen type II, the decreasing abundance of highly methyl-substituted alkylbenzenes and the parallel increase in less methyl-substituted alkylbenzenes in flash pyrolysates suggest that demethylation is an important chemical process in the thermal maturation of kerogen type II. [Copyright &y& Elsevier]

Abstract: Stable isotope ratios of non-exchangeable hydrogen (δD n) and of carbon were measured in type-II kerogens from two suites of Late Devonian to Early Mississippian black shale, one from the New Albany Shale (Illinois Basin) and the other from the Exshaw Formation (Alberta Basin). The largely marine-derived organic matter had similar original stable isotope ratios, but today the suites of kerogens express gradients in thermal maturity that have altered their chemical and isotopic compositions. In both suites, δD n values increase with maturation up to a vitrinite reflectance of R o 1.5%, then level out. Increasing δD n values suggest isotopic exchange of organic hydrogen with water-derived deuterium and/or preferential loss of 1H-enriched chemical moieties from kerogen during maturation. The resulting changes in δD n values are altering the original hydrogen isotopic paleoenvironmental signal in kerogen, albeit in a systematic fashion. The specific D/H response of each kerogen suite through maturation correlates with H/C elemental ratio and can therefore be corrected to yield paleoenvironmentally relevant information for a calibrated system. With increasing thermal maturity, the abundance of hydrogen in the kerogen that is isotopically exchangeable with water hydrogen (expressed as Hex, in % of total hydrogen) first decreases to reach a minimum at R o ∼0.8–1.1%, followed by a substantial increase at higher thermal maturity. [Copyright &y& Elsevier]

Abstract: FTIR absorbance signals in kerogens and macerals were evaluated as indices for thermal maturity. Two sets of naturally matured type-II kerogens from the New Albany Shale (Illinois Basin) and the Exshaw Formation (Western Canada Sedimentary Basin) and kerogens from hydrous pyrolysis artificial maturation of the New Albany Shale were characterized by FTIR. Good correlation was observed between the aromatic/aliphatic absorption ratio and vitrinite reflectance R 0. FTIR parameters are especially valuable for determining the degree of maturity of marine source rocks lacking vitrinite. With increasing maturity, FTIR spectra express four trends: (i) an increase in the absorption of aromatic bands, (ii) a decrease in the absorption of aliphatic bands, (iii) a loss of oxygenated groups (carbonyl and carboxyl), and (iv) an initial decrease in the CH2/CH3 ratio that is not apparent at higher maturity in naturally matured samples, but is observed throughout increasing R 0 in artificially matured samples. The difference in the CH2/CH3 ratio in samples from natural and artificial maturation at higher maturity indicates that short-term artificial maturation at high temperatures is not fully equivalent to slow geologic maturation at lower temperatures. With increasing R 0, the (carboxyl+carbonyl)/aromatic carbon ratio generally decreases, except that kerogens from the Exshaw Formation and from hydrous pyrolysis experiments express an intermittent slight increase at medium maturity. FTIR-derived aromaticities correlate well with R 0, although some uncertainty is due to the dependence of FTIR parameters on the maceral composition of kerogen whereas R 0 is solely dependent on vitrinite. [Copyright &y& Elsevier]