Analysis of the organic matter of oil shales by nuclear magnetic resonance

¹³C NMR spectroscopy was applied in the investigation of the structure of the organic matter in oil shales. By using Proton Enhanced Nuclear Induction Spectroscopy, a fair resolution of aliphatic and aromatic carbon signals was achieved. This method provided information on the relative ratio of aliphatic and aromatic carbons within a given set of samples (Aleksinac, Kimmeridge, Colorado, Australian torbanite and Estonian kukersite).     

High-Speed BVRI Photometry of SS Cyg at Quiescence and at Outburst

BVRI photometry of SS Cyg from the end of 1996 and the beginning of 1997 is presented. The star underwent an eruption around December 11. The amplitude of which was slightly bigger than those of observed earlier eruptions. We saw some indication of the future outburst in the decreasing of brightness in all colours by about 0.4 mag during the last two weeks before the event. The emission of the system moved strongly to the shorter wavelengths at outburst. Our multicolour data confirm the existence of a light variability with the orbital (spectroscopic) period at quiescence. Moreover we found for the first time that this variability exists also at outburst but its amplitude is 3–5 times smaller. Whereas the amplitudes of the orbital variability at quiescence decrease to the longer wavelengths, they increase at outburst to the longer wavelengths. The orbital folded curve at quiescence has two-wave shape and was fitted well by the different visibility of two diametrical opposite hot spots (210000 K) with angular size 10⁰ on the magnetic poles of the white dwarf. An analogy between the two basic states of the U Gem-star SS Cyg, the polar AM Her and Z Cam-star RX And was found.     

Multistage alkaline permanganate degradation of a type II kerogen

The products of a 27-step alkaline permanganate degradation of a type II kerogen from a sample of Toarcian shale, Paris Basin, have been studied. The high yield of oxidation products consisted of 1.86% neutrals and bases, 24.48% ether-soluble acids, and 45.95% precipitated, ether-insoluble acids, based on weight of original kerogen. The ether-soluble acids and the soluble products of further permanganate degradation of precipitated acids were found to consist mostly of saturated unbranched C₆–C₂₂ α,ω-dicarboxylic and C₉–C₂₅ monocarboxylic acids. Significant amounts of aromatic monocarboxylic, dicarboxylic and tricarboxylic acids were also found. Alkane tri- and tetracarboxylic acids were obtained in small concentration.     

Multicolour Photometry of RX and During 1994/95

The cataclysmic star RX And was observed in the states standstill and quiescence. They differed not only in the light level but in the type of variations around this level. The standstill observed by us turned out quite near to the maximum light and its duration was unusually long. The energy distribution of RX And at the standstill seemed similar to the spectrum of an accretion disk. Two variabilities with periods 3 h 43 min and 1 h 26 min were found at the standstill but only the second of them was present at quiescence too. The star did not show light variability with the spectroscopic period. We tried to interpret some of the results by the supposition that the Z Cam-stars are an intermediate subtype of the cataclysmic stars evolving from UX UMa-subtype to U Gem-subtype and that probably RX And presents a pattern of Z Cam-star that is very near to the U Gem-subtype.     

Multicolour Photometry of AM Her During 1994–96

Multicolour photometry of the polar AM Her was obtained during 3 observational seasons (1994/95/96). The star was in its high state for most of the observations. It was in its low state in '96 April. It was established that these two states differ not only in the average light level but in the larger amplitudes of variations at low state than at high state. Moreover the energy distributions of the two states differ in the stronger dependence of the flux on ν at high state than at low state. The Fourier analysis of the photometric data shows variability with the spectroscopic (orbital) period. The amplitudes of this variability in all colours are about two times bigger at low state than at high state. An attempt to explain the photometric behaviour of AM Her by a model of dominant emission of two hot spots at the magnetic poles of the white dwarf was made and the spot parameters were determined. This revised version was published online in August 2006 with corrections to the Cover Date.     

Consequences of anthropogenic activity for two remote alpine lakes in NW Slovenia as tracked by sediment geochemistry

Several geological and geochemical parameters were determined in the sediments of the 5th (5 J) and 6th (6 J) Triglav Lakes, Julian Alps (NW Slovenia), in order to study the impact of natural catchment characteristics and anthropogenic activity. Fish were introduced into both lakes in 1991 and a mountain hut lies on the shore of 5 J. Sedimentary grain size (GS) was distinctly coarser in 5 J than 6 J, with arithmetic means ranging between 46 and 60 and 23–36 μm, respectively. In contrast, the mineralogical composition of the two sediments was similar. Calcite predominated strongly, comprising more than 77 % of total minerals, while dolomite and quartz were rare. Organic carbon (OC) and total nitrogen (TN) concentrations were highest in surficial sediments, with levels of 14.4 and 1.8 %, and 19.3 and 2.4 % observed in 5 J and 6 J, respectively. C/N ratios (atomic) were lowest in the same surface sediments, with the two lakes characterized by similar values (9.6 vs. 9.4, respectively), suggesting a predominance of autochthonous organic matter (OM) in both lakes. Contemporary δ¹³C values were lower in 5 J (?21.0 ‰) than 6 J (?18.5 ‰) sediments. Considerable changes in these four parameters were observed in recently deposited material, reflecting a shift in the trophic status of both lakes that was likely induced by the introduction of fish. In addition, the smaller and shallower 6 J seemed to respond to changes faster than the larger and deeper 5 J, indicating the higher sensitivity of the former. δ¹⁵N values in surface sediments of 5 J and 6 J were ?2.9 and ?4.4 ‰, respectively, with levels increasing gradually with depth to approximately +1.0 ‰ in deeper sediments. The observed changes could most likely be attributed to the atmospheric deposition of reactive nitrogen. The mountain hut has seemingly not had a significant enough impact on the lakes to be recorded in their sediments.     

Testing fractal coefficients sensitivity on real and simulated earthquake data

We examined the behavior of different fractal dimensions when applied to study features of earthquake spatial distribution on different types of data. We first examined simulated spatial fields of points of different clustering level, following the so called Soneira-Peebles model. The model was chosen because it displays some similarity to the real clustering structure of earthquakes occurring on hierarchically ordered faults. The analysis of the capacity, clustering and correlation dimensions revealed that their behavior did not completely correlate with the clustering level of the simulated data sets. We also studied temporal variations of the fractal coefficients, characterizing the spatial distribution of the 1999 İzmit-Düzce aftershock sequence. The calculated coefficient values demonstrated analogous behavior like for the simulated data. They exposed different variability in time, but for all of them a systematic fluctuation was observed before the occurrence of the Düzce earthquake. Our analysis revealed that although fractal coefficients could be applied to measure earthquake clustering, they should be used with caution, trying to figure out the best coefficient for a certain data set.     

New maturation parameters based on naphthalene and phenanthrene isomerization and dealkylation processes aimed at improved classification of crude oils (Southeastern Pannonian Basin,Serbia)

Aiming at improved classification of crude oils, naphthalene and phenanthrene isomerization and dealkylation processes were considered in detail as a possible basis to select new maturation parameters. Crude oils originating from the Banat depression (Southeastern Pannonian Basin, Serbia) were used as objects of our study. Four new maturation parameters are proposed in this paper. Two of them are based on dimethylnaphthalene (DMN) and trimethylnaphthalene (TMN) isomerization reactions: DN_x = (1,3-DMN + 1,6-DMN)/(1,4-DMN + 1,5-DMN) and TNy = (1,3,6-TMN + 1,3,7-TMN)/(1,3,5-TMN + 1,4,6-TMN). The other two are based on demethylation of dimethyl-and trimethylphenanthrenes (DMP and TMP) into corresponding methylphenanthrenes (MP): MDR = ΣMP/ΣDMP and MTR = ΣMP/ΣTMP. The new parameters’ advantageous applicability was demonstrated by factor analysis, comparing them with maturation parameters known from literature. The text was submitted by the authors in English.     

An investigation of the significance of local site effects in Plovdiv, Bulgaria

Plovdiv is the second largest city in the Republic of Bulgaria. A large part of the city is located on Holocene alluvial sediments and the oldest neighborhoods are situated on syenitic rock outcrops. We believe that local site effects may be an important contributor to the destruction caused by earthquakes. The primary objective of this study was to estimate quantitatively the local site effects in the central area of Plovdiv in terms of fundamental site frequency and amplification factor. Another important objective was to see how these correlate with the geological structures underlying the city. Measurements of the seismic noise at more than two hundred regularly placed points were made in the central area of the city. The H/V spectra were then calculated and analyzed to determine the spatial distribution of the fundamental site frequency and the amplification factor. The results exhibit very good correlation with the local geology. They were also compared with an intensity map from the strong 1928 Plovdiv earthquake. The comparison clearly demonstrates that the local site effects were the main factor in the destruction of buildings—the zones where the most damage was observed are also the zones where we have low fundamental site frequencies and high amplifications. Similarly the areas with high fundamental site frequencies and low amplification factors cover the neighborhoods where less damage has been observed. This study may form a basis for a more comprehensive and systematic microzonation study in Plovdiv.