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Abstract Using the 1H NMR examination of a representative set of crude oils (86 samples, 54 oil fields and exploration areas) from the North Caucasus oil-and-gas basin, we obtained, for the first time, the structural-group composition of crude oils over the entire basin. Distribution density plots were presented for all the composition parameters measured. It was demonstrated that, because none of the parameters obeys normal distribution, non-parametric statistical analysis is needed for the data processing. In particular, medians and median confidence intervals (the latter being determined by signed-rank test), rather than means or root-mean-square deviations, should be relied upon. The North Caucasus oils were found to have a markedly lower content of aromatics (both monocyclic and bi-/polycyclic) than the crude oils from Western Siberia and Volga–Urals. Compared with the Eastern Siberia basin, the North Caucasus oils are distinguished by a slightly higher presence of bicyclic and polycyclic aromatics. At the same time, the North Caucasus oils exhibit the highest content of normal and monomethylated alkanes among the four basins under consideration. The North Caucasus oils were classified into three stratigraphic groups according to their oil composition. The first group consists of Triassic and Jurassic reservoirs. These crude oils have the lowest content of aromatics and the highest content of normal and monomethylated alkanes. The second group is the Cretaceous sediments, and the third group includes Paleogenic and Neogenic deposits. The content of aromatics increases consistently from the bottom to the top of the section.

—A comprehensive study of Domanik deposits of the Timan–Pechora Basin has been carried out. The examined composition of hydrocarbon biomarkers, chemical structure of kerogen, carbon isotope composition, and rock lithology, the Rock-Eval pyrolysis data, and the contents of bitumen and Corg in the rocks give an insight into the geochemical processes in the oil window in the Domanik deposits, which took place at Tmax = 435–450 °C. The bitumen coefficient βCB is maximum in this temperature interval, reaching 30%. The obtained data on the distribution of polycyclic biomarkers in the Domanik rocks and the bitumen and Rock-Eval pyrolysis data allowed determining the boundary values of biomarker maturity coefficients in the study of the maturation of organic matter of the rocks. The carbon isotope composition of bitumen fractions in the Domanik rocks is considered, and the bimodal distribution of the δ13C values of the bitumen is shown.

The distributions of the 13C NMR-measured structural-group composition parameters of the Lena–Tunguska basin crude oils were obtained. All these distributions were shown to be far from normal, many of them being asymmetric and/or bimodal. These oils exhibit a significantly lower content of aromatics than the Volga–Urals and Western Siberia oils. The principal maximum of Car distribution lies in the distribution tail areas of the other two basins. The Lena–Tunguska oils are free of fluids with low content (below 14 abs %) of n-alkyl structures. It was also demonstrated that the crude oils sampled from the basin’s two major tectonic structures, namely the Baikit anteclise and the Nep-Botuob anteclise, differ significantly from one another in the concentrations of aromatics and n-alkyl structures.

Oils in Tatarstan were determined to have been generated in at least two source rock formations, whose organic matter (OM) differed in genesis, redox conditions of sedimentation, and maturity. The oils of type 1 are hosted in Devonian terrigenous reservoir rocks, whereas the oils of type 2 occur in overlying reservoirs. Differences between the oils are reliably identified in most compositional parameters of saturated biomarkers, with the values of the two oil groups not overlapping for two parameters: Ts/Tm and t22/t21. The maturity of the group-1 oils is statistically significantly higher than that of the group-2 ones. The source rocks are identical at the macrolevel: the original organic matter was deposited in marine sedimentation environments under reducing conditions, which is consistent with literature data. Comparison of the compositions of the oils and OM of the Domanik Formation indicates that rocks of the Mukhanovo–Erokhov trough were not involved in producing oil accumulations in Tatarstan. Differences were also detected between genetic characteristics of oils from the terrigenous Devonian rocks and Domanik Formation in the arch part of the area. Organic matter in the arch part of the territory could be significantly involved in the generation of oil accumulations hosted in reservoirs in the Semiluk and higher horizons. It is demonstrated that earlier conclusions that the source rocks of certain oil groups differed in lithology are groundless. To estimate the confidence interval for the median values, a criterion of signs was proposed, which has never before been employed in organic geochemistry.

Increasing of production performance of production systems and equipment in the meat-processing industry is integrally linked to maintenance activities. The article analyzes the influence of technological effectiveness, level of hygiene, reliability and simplicity of equipment design on the main parameters of meat products quality. Here it is shown that the strategy of Total Productive Maintenance (TRM) and Lean production is important tool for assessment of parameter of the Overall Equipment Effectiveness (OEE), which is used to assess the main types of losses that reduce the equipment productivity. The link of influence between the structural and mechanical properties of food masses, the moisture content of the initial food raw material, the temperature and viscosity, the processing pressure, and the density for the optimal operating terms of the equipment are analyzed in this research. With the help of OEE concept, the time losses related to the features of the equipment functioning are determined. The types of losses are classified as follows: downtime and readjustment (availability or readiness for operation) of equipment, short-term shutdown of equipment and a decrease in processing speed (productivity or performance rate of the equipment), product rejects and product losses (quality losses) during startup of equipment. While analyzing of the operation of vacuum filler for sausages production, the values of parameters of equipment availability, it productivity and product quality are calculated. The availability index is 0.79, the productivity index is 0.76, and the product quality index is 0.95. Taking into account the obtained data on equipment availability, productivity and product quality, it is determined that the overall equipment effectiveness (OEE) accounts for 57%. The application of this method for studying the overall equipment effectiveness operation can be applied to any technological equipment used in the meat-processing industry and allows eliminating many problems that arise during the operation of technological equipment, improving its technical and economic parameters, and developing a system of measures for improvement of its maintenance and repair.

We report the results of systematic experimental and theoretical studies of structural and dynamical properties of short-period GaN/AlN superlattices. The multilayer structures with the thicknesses of the constituent layers varying from two to several monolayers are grown using the submonolayer digital molecular beam epitaxy technique. In the framework of density functional theory, the lattice dynamics properties of the superlattices are studied. Good agreement between the experiment and theory is found, which made it possible to establish unambiguously a relationship between the features observed in the Raman spectra and the microscopic nature of the acoustic and optical phonon modes. The results obtained enhance the capabilities of Raman spectroscopy as a fast and non-destructive characterization method of short-period GaN/AlN superlattices and can be used to optimize growth process parameters for the fabrication of structurally perfect low-dimensional heterostructures.

One of the processes that can locally be involved in forming the composition of aromatic hydrocarbons in oils is the reaction of electrophilic methylation of aromatic cycles. Up to 40% of the original oil compounds can be transformed into methylation products. Methylation is demonstrated to most likely proceed during catagenesis, after the generation of the fluid that had produced a given oil accumulation. The methylation of aromatic cycles is a definite indicator that the source rocks are either clays or silicites containing relatively much clay material. The methylation reaction is proved not to be widespread even within a given basin, and hence, analysis for the presence of electrophilic methylation products can be efficiently applied in geochemical reconstructions. One of the consequences of methylation may be changes in the concentrations of isomers of aromatic compounds that are used in calculating maturity coefficients, and this may lead to misinterpretations of the results.

—The composition of compounds employed as markers for anoxia in the photic layer of the sedimentation basin is studied in samples from Upper Devonian domanik-type sediments (Sargaevian, Semilukian, and Mendymian horizons, Famennian stage), which are widespread over the Volga–Urals basin. The studies were carried out along the north-south section spanning the northern and central parts of the Volga–Urals areas. The H2S contamination of photic layer was determined over the most part of the studied territory. During the Semilukian time, the boundary of H2S contamination passed through the middle part of the near-slope zone of the Mukhanovo–Erokhov Trough; the contamination reached the highest thickness in the northern part of the region. The intense H2S contamination also occurred in this part in the Pashiiskian and Sargaevian time. The Mukhanovo–Erokhov Trough during Mendymian and Famennian was characterized by a strong change of setting: from a steady strong contamination to its complete absence. It is shown that changes in the content of anoxia markers in samples from the the Kama–Belsk Basin and South Tatar Arch were caused by variations of thickness of the contaminated layer. It is revealed that the processes of complete hydrogenation of initial polyenes prevail over cyclization for the domanik-type sediments over the entire region. It was found that the ratio of the total content of alkyl benzenes in the fraction of aromatic compounds to the total content of products of complete hydrogenation of initial polyenes in OM from the domanik-type sediments of the studied areas does not depend on the OM maturity. Explanation of this fact is proposed.

Analysis of the composition of crude oils from four oil and gas basins by gas chromatography–mass spectrometry has shown that aromatic compounds bearing a phenyl substituent are as typical of oils as the well-known phenanthrenes and chrysenes. Thus, biphenyls are the first member of the series of compounds of this structural type. Unsubstituted and alkyl substituted phenylnaphthalenes, terphenyls, phenylphenanthrenes, and naphthylnaphthalenes have been identified; the smallest set of components of this type (only phenylnaphthalenes) is in Volga–Urals oils. Unlike the case of dispersed organic matter (OM), the main components in oils are alkyl substituted compounds, which can have as long substituents as C10 alkyls in some cases. The proportion of unsubstituted compounds is small. In all the oils, thermodynamically more stable isomers predominate. The phenylnaphthalene content is close to the content of chrysenes, the proportion of which is about an order of magnitude lower than that of phenanthrenes. In one of the samples, phenylnaphthalenes are about in the same amount as phenanthrenes. The total concentration of terphenyls, phenylphenanthrenes, and naphthylnaphthalenes is usually much lower than the concentration of phenylnaphthalenes. To date, the use of phenyl substituted aromatic compounds in geochemistry has been limited to oil–oil and oil–OM correlations. Studying compounds of this type is important both for more detailed characterization of the composition of aromatic compounds of crude oil and for understanding the processes of oil generation in different environments.

We report the results of systematic Raman spectroscopy studies of AlxGa1 –xN (x ~ 0.75) layers grown using plasma-assisted molecular beam epitaxy at various stoichiometric conditions and growth fluxes. The high-intensity asymmetric low-frequency peak obeying Bose statistics is discovered in Raman spectra of the layers grown by temperature-modulated epitaxy at strongly Ga-enriched conditions. Theoretical model is developed to explain the origin and the high intensity of the observed low-frequency peak, which is attributed to the presence of excessive metallic gallium in AlGaN layers and can be explained by vibrations of gallium clusters with a diameter of ~1 nm. The nature of the low-frequency peak is similar to that of the boson peak in glasses, which occupies the same frequency range in Raman spectra. We demonstrate the capabilities of Raman spectroscopy as an express and non-destructive technique for optimization of growth conditions of AlGaN layers to achieve simultaneously the atomically-smooth droplet-free surface morphology and the high structural quality.

It is established that the source rocks for the oils of Tatarstan was formed under similar conditions in the presence of anoxia in the photic layer of the sedimentation basin that existed during the whole time of accumulation of the initial organic matter at a considerable thickness of the layer infected with hydrogen sulphide. It is not excluded that disturbances in the existence of anoxia existed or thickness of the infected layer was reduced that resulted in decreasing of anoxia markers content for some oils. Biocenoses of microflora in the sedimentation layer contaminated by hydrogen sulfide demonstrate high stability. Transformation conditions of the buried organic matter in diagenesis and catagenesis were uniform, which manifests itself in approximately the same ratio between the depth of the complete hydrogenation and cyclization of the initial polyene aromatic carotenoids, the closeness of the molecular mass distributions of the C-C bond destruction products of components C40 and relatively small differences in the total concentration of monoaromatic compounds and the sum of hydrogenated analogs of the initial aromatic carotenoids. Analysis of content of the components – anoxia markers throughout the whole Devonian section is needed to establish the complexes that generated oils of Tatarstan.

The source rocks of the oils in Tatarstan were determined to be formed under similar conditions, at anoxia in the photic layer of the sedimentation basin, with anoxia continuing throughout the whole time when the initial organic matter was accumulated, at a significant thickness of the H2S-infected layer. For some of the oils, disturbances in the anoxia may have occurred, or the thickness of the H2S-infected layer may have been reduced, and this resulted in a decrease in the content of anoxia markers in these oils. Biocenoses of microflora in the sedimentation layer contaminated with H2S show evidence of high stability. Transformation conditions of the buried organic matter in the course of diagenesis and catagenesis were uniform, as follows from the merely insignificantly varying relations between the depth of the complete hydrogenation and cyclization of the initial polyene aromatic carotenoids, the similarity in the molecular mass distributions of the destruction products of the C–C bond in C40 components, and the relatively small differences in ratios of the total concentration of monoaromatic compounds to the totals of hydrogenated analogues of the initial aromatic carotenoids. The source rocks of oils in Tatarstan can be identified based on analysis for concentrations of components that are anoxia markers in all of the Devonian rocks.

The distribution of the 1H NMR-measurable characteristics of the structural-group composition of crude oils from the Lena–Tunguska basin has been revealed. It has been shown that some distributions are fairly close to the normal one, while others greatly differ from it and are asymmetric. These oils differ from Volga–Urals and Western Siberia oils by a significantly lower aromatics content and a high concentration of radiogenic unsaturated hydrocarbons. The average degree of substitution of aromatics in them is higher than in Western Siberia oils; the distribution maximum for the parameter characterizing this value falls in the region between the two distribution maxima for the Volga–Urals oil. The distribution of the Har,2+/Har,1 ratio is about the same as in the Volga–Urals and Western Siberia oils. A significant difference in the composition between the oils of the Baikit anteclise and the Nepa–Botuoba anteclise has been found.

A procedure is proposed for estimating the content of individual groups of compounds, anoxia markers, in the photic layer of the sedimentation basin and their total content in fractions of oils and dispersed organic matter. Appropriate variants of data presentation are analyzed. Based on the data on the common content of anoxia markers, a method has been proposed for answering the question of whether hydrogen sulfide contamination was permanent, covering the major part of the water column, or there was an episodic infection spread to a limited water layer. These data also allow the assessment of the role of organic matter formed under anoxic conditions in its total balance. A composition parameter is proposed that ensures the determination of the similarities in the conditions of organic matter transformation in different rocks.

This study presents data on concentrations of n-alkylbenzenes, n-alkylnaphthalenes, phytanylnaphthalene, and methylphytanylnaphthalene in representative crude oils of Tatarstan. The results of the study reveal the elevated concentrations of C19, C21, and C23 homologues of n-alkylbenzenes and n-alkylnaphthalenes, which can be considered as biomarkers. The proposed procedure for comprehensive quantification of this group of biomarkers can be used as an efficient tool to study oils from the major petroleum basins of Russia. Based on the results of the study, four genetic groups of oils in Tatarstan have been distinguished: (1) oils from the north and northwest (Bir saddle, Lower Kama system of linear faults, and Saraily saddle), (2) oils from Devonian terrigenous reservoirs within the South Tatar arch and Melekes depression, (3) oils from Carboniferous reservoirs, and (4) oils from Devonian carbonate reservoirs. All these oils belong to the same genetic macrotype. Based on the results of this study, the sedimentary sections of the Melekes depression cannot be regarded as potential source rocks. It is assumed that oil has migrated to the northern part of the region from the north or east. Some of the possible migration routes for oils from the remaining part of Tatarstan are from the southeast and/or south.

International audience; Electronic structure of series of tellurium oxide crystals within the TeO 2-TeO 3 binary system is studied with generalized gradient approximation to DFT, hybrid DFT-HF method with the PBE0 and B3LYP exchange-correlation functionals and with quasiparticle G 0 W 0 approach. Comparison with available experimental data revealed significant underestimation of the band gap values within DFT. The hybrid DFT-HF method leads to slightly overestimated values of the bandgap, and the best agreement with experimental data provides the "one-shot" G 0 W 0 calculations starting from Kohn-Sham solutions. The electronic structure of tellurium oxides is discussed in details. It is found that bandgap value decreases proportionally to fraction of tellurium atoms in octahedral coordination. This change is due to formation of gap states by 5s(Te) electrons which do not participate in Te(VI)-O bonding. Dielectric properties is calculated within Random Phase approximation for the series of tellurium oxides and high nonlinear properties of the compounds is predicted by empirical Miller's rule.

The composition of saturated biomarkers (alkanes, steranes, and triterpanes) in the Upper Devonian sediments (the Sargaev, Semiluk, and Mendym horizons, the Famennian stage) that belong to the Domanik formation, which is widespread on the territory of the Volga-Ural basin, was studied. The section elongated from N to S that covers the northern and central regions of the Volga-Ural basin was observed. A set of 21 parameters was used to characterize saturated hydrocarbons, including those rarely used in geochemical studies. For each parameter a set of mean values for the considered region as a whole and its individual parts was calculated and distribution-density plots were built. It was established that the most representative parameter for characterizing the Domanik-type deposits as a whole is a highly specific parameter, that is, the ratio of 29,30-bisnorhopane C28 to hopane C29. Most of the characteristics of the genetic composition demonstrate the difference between the organic matter (OM) of the vault part of the region and the Mukhanov- Erokhovsky trough. There are large differences in the parameters that characterize the maturity of OM. The characteristic values of the parameters for both the vault and the depression zone are given; two to three genetic groups of OM were determined for the majority of the parameters in both regions. A method for constructing the distribution-density graphs of the parameters is proposed that makes it possible to take their features fully into account.

Composition of saturated biomarkers revealed the presence of at least two sources of oils of the Romashkino field with the monotypic conditions. All the studied oils are characterized by presence of a large number of components—anoxia testifiers in the photic layer of sedimentation basin in the fractions of aromatic compounds. These are products full or partial hydrogenation, cyclization and degradation of polyene compounds. Total content of this group of compounds is measured in these fractions for the first time. It is shown that the total content of the anoxia testifiers is high. Thus the specific characteristic of oil source rocks is defined—their formation in the conditions of existence of anoxia in the photic layer during the entire accumulation time of initial organic matter, and the thickness of the layer infected with hydrogen sulphide was significant. On the basis of composition and content of the anoxia testifiers it is shown that the hydrogenation of initial polyenes prevailed in diagenesis over the processes of cyclization.

The results of joint theoretical and experimental studies aimed at revealing features in the Raman spectra, which can be used for evaluation of the interface quality between GaN and AlN layers in short-period GaN/AlN superlattices (SLs) are presented. The Raman spectra for SLs with sharp interface and with different degree of interface diffusion are simulated by ab initio calculations and within the framework of random-element isodisplacement model, respectively. The comparison of the results of theoretical calculations and experimental data obtained on PA MBE and MOVPE grown SLs, leads to conclusion that the spectral region of the A1(LO) confined phonons is very sensitive to the degree of interface sharpness. As a result of comprehensive studies, the correlations between the parameters of the A1(LO) confined phonons and the structure of SLs are obtained. The results of the complex studies can be used to optimize the parameters of the growth process in order to form structurally perfect short-period GaN/AlN SLs.

The paper presents gaz chromatography–mass spectrometry and 1H- and 13C-NMR data on the composition of hydrocarbon markers and structural-group composition of oils in the Timan–Pechora oil and gas province. The set of samples is subdivided into groups whose oils differ in composition and the distribution of their polycyclic biomarkers. All of the oils show closely similar geochemical characteristics, types of their source organic matter, and thermal maturity. Comparison of oil characteristics (composition of the polycyclic biomarkers) and parameters determined by chromatography–mass spectrometry makes it possible to reveal certain important (and calling for further investigation) relations between the composition of the structural groups of hydrocarbons in the oil fluid and its geochemical characteristics.

Samples of carbonate and siliceous-carbonate deposits of Semiluk—Sargaev horizons of the N‒NE slope of the South Tatar uplift, Volga-Ural petroliferous basin, have been studied. Specific feature of the source rocks—high concentration of compounds—anoxia testifiers in the photic layer has been identified. That is, organic matter has been deposited under the conditions of the constant presence of anoxia in the photic layer of the sedimentation basin at sufficiently high thickness of the water column contaminated with hydrogen sulfide. Since by the composition of saturated hydrocarbons the studied samples are typical for deposits of the Semiluk horizon of the central part of the Volga-Ural basin, we can assume a fairly wide prevalence of such conditions within the South-Tatar arch. Changes in the concentrations of the components—anoxia markers—show cyclical changes in output layer contaminated with hydrogen sulfide or its bioproduction within the studied time.

In Volga−Urals crude oils, an increase in the aromatics content is characterized by a rapid increase in the relative amount of polysubstituted aromatic rings and a generally lower proportion of bi- and polycyclic aromatics, unlike the case of Western Siberia oils. The difference between the oil and gas basins is most probably due to the special features of the source organic matter of the oils. The regional features of the Volga−Urals oils are a relatively weak relationship between the concentrations of mono- and bi- + polycyclic aromatics and a relatively close relation of Σn-Alk to typically uninformative parameter Hβ, which indicate a high uniformity of the composition of saturated cyclic compounds and moieties of hybrid naphthenoaromatic components. In addition, the assumption that (H/C)ar/(H/C)al = const does not hold for Volga−Urals oils. However, the relationships between the main parameters describing total aromaticity (primarily, Car, Har) and n-alkyl structures (primarily, Σn-Alk) are identical for oils from both the basins. The total number of relationships that can be universal for oils from different oil-and-gas basins is fifteen. To estimate Car from 1H NMR data for Volga−Urals crude oils, a linear dependence on the two variables Har and Hα should be used. The expressions obtained to relate the structural-group parameters have made it possible to reveal a number of oils that stands out among the others.

The finite field method using ab initio hybrid functional approach was applied to estimate nonlinear properties of the cluster based on paratellurite crystal structure. The good agreement was found with previously reported data.The method demonstrate high efficiency in prediction of nonlinear properties for a wide ensemble of sufficiently large polyatomic clusters.

The results of experimental and theoretical studies of phonon modes in short-period GaN/AlN superlattices grown by PA MBE on the (0001) Al2O3 substrate are reported. In the framework of Density Functional Theory and Elastic Continuum Model the lattice dynamics properties are studied of (GaN)m(AlN)n SLs (m+n≤24), where n and m are the number of monolayers. Good agreement between experiment and theory is found, which made it possible to establish unambiguously a relationship between the features observed in the Raman spectra and the microscopic nature of the acoustic phonon modes. The obtained results open new possibilities for analyzing the structural properties of GaN/AlN SLs by Raman spectroscopy.

Among 120 pairwise relations between 16 main 1H and 13C NMR-measurable characteristics of the structural group composition of Volga–Urals crude oils, 10 most consistent relations (correlation coefficients |rs| ≥ 0.9), 13 relations with |rs| in the range of 0.8–0.9, and 33 pairs with loosely related or mutually independent members (|rs| ≤ 0.3) have been revealed. Several relationships are parametric. The main parameter is Car. The overall picture of the relationships is complex; correlation coefficients with the absolute value above 0.7 are observed not only between the parameters characterizing the structure in the same group of entities (aromatic, n-alkyl): it has been found that Car correlates with the total content of n-alkyl structures (rs =–0.76). Having definitely common features, oils from the Volga–Urals and Western Siberia oil and gas basins noticeably differ from one another. To explain the differences, it is necessary to launch an integrated study that is methodologically beyond the scope of contemporary petroleum geochemistry. The paper demonstrates the capabilities of correlation analysis for solving problems to which this method has not been yet applied in petroleum geochemistry: partial correlation coefficients as a means of identifying parametric relationships and Spearman correlation coefficients for nonnumeric values in determining differences in the composition between oils of different structures and from different territories or stratigraphic plays.

Raman spectra of the mixed crystalline oxides of the (1 - x)TeO2 + xTeO3 (x = 0, ¼, ½, 1) series were recorded and simulated by using the DFT calculations. Good agreement between observed and calculated Raman spectra makes it possible to establish unambiguous assignment for all prominent Raman lines. This result gives an insight into relations between structural peculiarities and observed spectral features for the crystals promising as nonlinear optical materials. Highlights • Several mixed TeO2-TeO3 crystals were synthesized by solid-state chemistry • DFT calculations well describe structures and phonon spectra of TeO2-TeO3 oxides • Raman lines can be assigned to internal vibrations of TeO4 and TeO6 polyhedrons • Observed Raman bands can be used as fingerprints of different structural units.

The character of the distribution of 16 main NMR-measurable parameters of the structural-group composition of Volga–Urals crude oils has been assessed. It has been shown that the distributions quite significantly differ from the normal distribution; they are in general asymmetrical and essentially different. Total aromaticity and the amount of n-alkyl structures in oils of the major stratigraphic plays are on average the same, although there are differences between the northern, central, and southern parts of the oil-and-gas basin. Regarding the concentration of unsaturated hydrocarbons, there are differences between both the plays and territories. Similarities and dissimilarities between the West Siberian and Volga–Urals basins in distributions have been revealed. Some features observed for Western Siberia oils have to be other in the Volga–Urals basin. Upper Carboniferous and Lower Permian carbonate reservoirs in the northeast of the basin have been found to contain oils with a uniquely high concentration of aromatics that evidently differ in composition from those normally present in crude oils. The advantages of interval plots of probability density over histograms for comparing the distributions have been demonstrated. Using the particular material, it has been shown that the Student t-test conventionally used to compare average values for oil groups leads to false conclusions. To determine systematic shifts between distributions, it is necessary to use the Mann–Whitney test and compare the medians of distributions.

Equations to describe the relationships between 37 pairs of fairly well correlated basic and most easily NMR-measurable characteristics of the structural-group composition of Western Siberia crude oils have been derived. Different variants of graphing the regression lines have been considered. A method for processing initial data has been proposed that suits the standard situation for petroleum geochemistry when the scatter of data points around the trend line is determined by differences between the samples, rather than measurement errors. The characteristics of the deviations of values for the composition parameters from their trend lines, by which a reasonable sequence of the extension of the sets of measured parameters can be built in a comparative study of the composition according to the research objectives, are reported. It has been demonstrated that the given description of the composition can help to identify objects that stand out and are unique in this sense and provides new criteria for grouping fluids of this kind. It has been shown that the parameter Car defining aromaticity of the samples from Western Siberia can be calculated with good accuracy from the value of the rapidly and inexpensively measurable quantity Har. A correlation between the aromaticity of the samples and the amount of n-alkyl structures in them has been revealed.

The oligomerization of higher α-olefins over a set of heterogeneous mesoporous catalysts has been studied using the example of decene-1. It has been shown that mesoporous catalysts based on the sulfonated, perfluorinated copolymer F-4SF exhibit high activity in oligomerization of decene-1 in both a batch reactor and a flow system: in the former case, the olefin conversion reaches 95–99% with the yield of dimers of 90–95%; in the latter case, the conversion of decene-1 to oligomers exceeds 70%.

International audience; The ab initio calculations performed for the TeO2?Te4O9?Te2O5?TeO3 series of crystal lattices have revealed that, in this series, the average v3 non-linear susceptibility increases for about 10 times. Such a huge effect is attributed to the strong augmentation of the Te atom d-function contributions in valence molecular orbitals, which accompanies the Te4+?Te6+ transformation. The results obtained allow concluding that the TeO3-related materials can be of interest in non-linear optic device engineering.

AlN/GaN superlattices (SL) grown by metalorganic vapor-phase epitaxy with the period of SLs varied from 20 nm to 140 nm, and the thickness of the structures ranged from 0.7 to 1 µm were studied by polarized Raman spectroscopy technique. The peaks within a complex spectral feature of the symmetry A1(TO) observed at about 580 cm−1, were assigned to the interface and quasi-confined phonons. Frequency splitting between the peaks was found monotonously increasing along with the SL period. This dependence was explained using the dielectric continuum model. A method based on this finding was proposed for estimating the period SL using Raman spectroscopy. This method extends the traditional approach based on the studies of folded acoustic phonons in the short-period SLs.

Knowledge about the stability of hydrous borates and borosilicates at high pressures are of critical importance to our understanding on the boron geochemical cycle. Raman spectroscopic measurements of parasibirskite CaHBO

Nickel orthoborate $\mathrm{N}{\mathrm{i}}_{3}{(\mathrm{B}{\mathrm{O}}_{3})}_{2}$ having a complex orthorhombic structure Pnnm (No. 58, $Z=2$) of the kotoite type is known for quite a long time as an antiferromagnetic material below ${T}_{\mathrm{N}}=46\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, but up to now its physical properties including the lattice dynamics have not been explored. Six $[\mathrm{Ni}{\mathrm{O}}_{6}]$ units of $2a$ and $4f$ types are linked via rigid $[\mathrm{B}{\mathrm{O}}_{3}]$ groups and these structural particularities impose restrictions on the lattice dynamics and spin-phonon interactions. We performed the symmetry analysis of the phonon modes at the center of the Brillouin zone. The structural parameters and phonon modes were calculated using the dmol3 program. We report and analyze results of infrared and Raman studies of phonon spectra measured in all required polarizations. Most of the even and odd phonons predicted on the basis of the symmetry analysis and theoretical calculations were reliably identified in the measured spectra. Clear evidence of the spin-phonon interaction was found for some particular phonons below ${T}_{\mathrm{N}}$. An unexpected emergence of several very narrow and weak phonon lines was observed in the infrared absorption spectra exactly at the magnetic ordering temperature ${T}_{\mathrm{N}}$. Moreover, anomalous behavior was found for some Raman phonons. The emergence of new phonon modes in the infrared and Raman spectra exactly at ${T}_{\mathrm{N}}$ proves the existence of a magnetostructural phase transition of a new type in $\mathrm{N}{\mathrm{i}}_{3}{(\mathrm{B}{\mathrm{O}}_{3})}_{2}$. A possible nature of this transition is discussed.

Correlations between frequencies of the Raman-active A(TO) and E(LO) phonons and the layer thickness ratio in the AlN/GaN superlattices are determined. Theoretical frequency-structure relations are derived by using the dielectric continuum model. It is found that the elastic strains which inevitably arising in the layers upon SL growth affect frequencies of the most Raman-intense polar modes insignificantly. The obtained frequency-structure relations agree well with available experimental data. These results confirm efficiency of the Raman spectroscopy for a fast nondestructive structure characterization.

Assignment of 13C NMR signals of compounds with ethyl, n-propyl, n-butyl, n-amyl, and n-C6+ alkyl substituents in different positions of carbon chains in the spectra of saturated hydrocarbon fractions of crude oils and in the spectra of crude oils, taking into account the dependence of chemical shifts on the recording temperature, the concentration of the test solution. and the composition of the object of study, has been proposed. The capabilities of the 13C NMR technique as applied to determination of this almost unexplored group of hydrocarbons in crude oils have been discussed.

International audience; Ideas currently dominating the field of structural studies of TeO2-based glasses are critically considered. A new physically and chemically consistent approach to the constitution of binary TeO2-WO3 glasses is proposed, in which the reasoning coming from the Raman spectra reexamination are correlated with the basic principles of thermodynamics. Separation into two phases is suggested in such glasses. One phase is TeO2, and another is Te(WO4)2 consisting of tetrahedral [WO4]2 anions and of Te4þ cations. Supplementary MnOk oxides added to the glasses are found incorporated in the former phase, thus producing solid solutions (for M¼Ti, Nb) or tellurite compounds (for M¼Nd).

A group of saturated nonisoprenane dimethyl-branched, alkyl-substituted hydrocarbons of the R-CCCCCC(C)CCC(C)CCCCC-R′ type has been found for the first time in crude oils and dispersed organic matter (DOM). Their concentration in the saturated hydrocarbon fractions of crude oils and DOM from the southern part of the Anadyr basin is 1–2 wt % and is well above that of their structural isomers with the closest structure in the same samples. Some ideas about possible sources of these hydrocarbons have been advanced. In the methodological aspect, the simplicity and efficiency of 13C NMR spectroscopy as applied to searching for previously unidentified alkyl structures in crude oils and DOM have been demonstrated, using as spectral parameters coefficients that determine the dependence of chemical shift on the recording temperature and the concentration of the fraction in the solution.

The informativity of 13C NMR spectroscopy as applied to solving the class of problems based on the data of comparative analysis of objects has been evaluated using a material from the southern part of the Anadyr oil-and-gas basin (saturated-hydrocarbon fractions of crude oils and bitumenoids). A set of 27 parameters measured from 13C NMR spectra has been proposed to characterize the composition of the samples with different degrees of detailing the structure of all components of the fractions. Methods for the determination of the degree of closeness of the sample composition have been considered, and it has been shown that not all of them satisfy the natural requirement of transitivity. A simple comparison procedure has been proposed for the case of multiparameter description of the fractions, with the values of the parameters lying in a wide range that has the property of transitivity on the material in question. It has been shown that 13C NMR radically extends the capabilities of the comparative analysis of the composition of crude oils relative to the conventional methods (GLC, GC-MS). In contrast to the results of study of the individual composition of saturated hydrocarbons (including the presumably most informative data on the composition of cyclic biomarkers), the 13C NMR data for the given material revealed a regular change of oils from the bottom up the section and to establish that the bitumenoids from its lowest part has nothing in common with the crude oils examined. The analytical parameters derived from the 13C NMR spectral data are not, in this case, too sensitive to inevitable variations in composition associated with sampling procedures or other insignificant factors. Thus, the generally accepted view on 13C NMR as a technique useless for tackling this class of problems can be regarded as refuted.

Vibrational spectra of rhombohedral TeO3 (r-TeO3) are analyzed along with those of ReO3-like proto-phase (c-TeO3) and α-TeO2 (paratellurite), emphasizing their lattice dynamic and crystal chemistry aspects. It is shown that (1) r-TeO3 can be regarded as resulting from the condensation of a particular R-point soft phonon of c-TeO3; (2) the Raman spectra of r-TeO3 and α-TeO2 are indicative of the two fundamentally different (from the crystal chemistry point of view) types of crystalline oxides, namely, framework-type and island-type, respectively. Copyright © 2010 John Wiley & Sons, Ltd.

Unsaturated hydrocarbons (UHCs) of thermocatalytic origin (0.3–1.3 wt %) generated directly from the heteroatomic components of organic matter (OM) of source rock strata were first discovered in Mesozoic-Cenozoic oils. In addition, radiogenic UHCs (∼1.5 wt %) were found for the first time among hydrocarbons from bitumens of dispersed OM. It was shown that their presence can be attributed to natural radiation due to radioactive isotopes occurring in the rock. Thus, it was demonstrated that noticeable effects of radiation-induced processes on the composition of rock OM should be taken into account in young (Neogene) deposits as well. Unsaturated hydrocarbons were generated under conditions in which processes involving the carbocationic mechanism did not play a noticeable role. In the samples from Neogene deposits from the southern Anadyr basin, UHCs experienced to a small extent the effect of secondary aging processes, which resulted in reduction in the relative concentration of the least stable components. Dimensionless parameters were proposed such that their numerical values make it possible to differentiate UHCs of different origins and to assess the severity of their aging processes.

Vibrational spectroscopy data were used to gain insight into the possible locations of extra oxygen ions introduced into La8+xSr2−y(SiO4)6O2+δ compounds to raise their ionic conductivity. Perturbations observed in the Raman and infrared spectra of these compounds with increasing δ were explained by using the ab initio calculation results for the fully stoichiometric (x = y = δ = 0) lattice. This allowed the inference that the extra oxygen ions are incorporated into LaO tunnel-like fragments inherent in the studied structures. Copyright © 2010 John Wiley & Sons, Ltd.

The presence of C15+ trans-1-methyl-2-alkylcyclopentanes in crude oil has been proven for the first time by means of the 13C NMR technique, and a procedure for their identification is described. It has been shown that these hydrocarbons represent a group of compounds bearing structurally different substituents, including the homologous series of trans-1-methyl-2-n-alkylcyclopentanes extended over a broad range of molecular masses. Their concentration in five samples of topped saturated petroleum hydrocarbons varies severalfold, with the maximal value being ∼1 wt %. The ability of hydrocarbons from this group to form complexes with urea and thiourea was examined. The importance of the analysis of the temperature and concentration dependences of the chemical shifts of signals for the determination of the structure of previously unknown compounds in oil.