Highly efficient scintillation Lu2SiO5 ‒ z:Y3+:Ce3+:Ca2+ crystals are grown from 20 to 85

The instability of asphaltenes in crude oils, manifested in their precipitation, is a major production issue that may arise both during the recovery and processing of petroleum feedstocks. The purpose of this study was to investigate the molecular structure of asphaltenes in order to shed light on the causes of their precipitation. To this end, the molecular structures of stable (remaining in the solution) and unstable (precipitated) asphaltenes were characterized by EPR, NMR, and IR spectroscopy. Using crude oil asphaltenes and air-blown asphalt as objects for the study, only weak increasing and decreasing trends were observed in the content of aromatics and oxygenates, respectively, in the unstable asphaltene fraction. The stable and unstable asphaltenes were found to differ in adsorption capacity. It was shown that the species adsorbed on asphaltenes are rich in moieties of aromatic acid esters, and that removing these species further eliminates the structural-group composition differences between stable and unstable asphaltenes. The study findings suggest that the stability of asphaltenes in crude oils can be controlled by introducing synthetic aromatic acid esters structurally similar to natural surfactants.

The paper presents the results of numerical modeling and analysis of the stress–strain state of the epicentral zone of a strong earthquake in Northeast China that occurred on July 27, 1976, with Ms = 7.8. Many present-day works continue to discuss the reasons for such a strong earthquake, which occurred in tectonic conditions: far from interplate boundaries, inside the Tangshan tectonic block bounded by tectonic faults. However, new published geodynamic, seismological, geophysical, and geodetic data provide confidence in the determining role of fault tectonics in this region. Based on an analysis of the results of modeling of the stress–strain state preceding the Tangshan earthquake with coseismic geophysical and geodetic data, we propose an earthquake rupture formation model. The results of comparing independent shear stress estimates with the results of modeling in the sources of strong earthquakes suggest that areas of tectonic stress concentration are localized in the interfault rupture of the Tangshan fault, reaching maximum values at the termination of fault ruptures σi ≈ 50 MPa and τxy ≈ 20 MPa. The hypocenter of the main seismic event (taking into account the coordinate determination error) is located in the region of stress intensity 35‒50 MPa and a ratio of main stresses σxx/σyy ≈ 8–10. It should be expected that these zones are the rupture initiation site, the extent of which depends on the amount of accumulated elastic potential energy of tectonic stresses in the adjacent region. For the Tangshan earthquake, this area corresponds to high-intensity stresses in a band with a length exceeding 30 km and width reaching 4.5 km, exceeding 30 MPa.

Our study compares the structural, photophysical, and electrochemical characteristics of 3,4,5- triphenyl-1-neomenthyl-1,2-diphosphole (1) and 3,4,5-triphenyl-1-mesityl-1,2-diphosphole (2). Experimental and optimized geometries of 1-R-1,2-diphospholes are close to each other and imply a significant delocalization within the 1,2-diphosphole ring for both molecules. Both compounds exhibit a green solid-state emission, whereas the DCM solutions are non-emissive. The preliminary electrochemical oxidation followed by electrochemical reduction leads to the anion-radical paramagnetic form, which is stable for 1-aryl-1,2-diphosphole, but unstable for 1-alkyl-1,2-diphosphole. The radical nature of 2(center dot-) was confirmed by in situ EPR-spectroelectrochemistry along with DFT calculations and in situ UV/Vis-spectroelectrochemistry.

The results of modeling the stress–strain state of the epicentral zone of the strong crustal earthquake Aketao, which occurred near Muji (China) on November 25, 2016, with magnitude Mw 6.6, are presented. The finite element method is used to model the stress–strain state in the epicentral zone with subsequent construction of stress intensity maps before and after the earthquake. The possibility to determine the location of the rupture origin and its extent, including estimation of the scalar seismic moment and the earthquake magnitude, is shown. The possibility to calculate the seismic moment rate as a function of time Mo(t) based on the model of the stress–strain state of rupture (earthquake focus) is presented for the first time, which allows obtaining synthetic seismograms and accelerograms of a potential earthquake in the future.

The study considers a possibility of studying the manifestation of the major background ions derived from the main elements (H, N, O, and Ar) of inductively coupled plasma under low-temperature (“cold”) plasma conditions through thermodynamic simulation. These ions, known to induce significant spectral interferences, are always observed when aqueous samples are injected into inductively coupled plasma mass spectrometers (ICP–MS). Using thermodynamic simulation in the temperature range from 2000 to 5000 K, the quantitative composition of the major background ions in ICP–MS was determined as a function of plasma temperature. A comparison of the theoretical calculations and experimental data from mass spectral measurements of the major background ions was conducted, revealing a high degree of correlation between the two sets of the results. This agreement between the calculations and experiments confirms the validity of the thermodynamic model used for thermochemical processes in ICP–MS and its applicability to subsequent calculations in addressing analytical challenges. Additionally, a method is proposed for the unambiguous evaluation of the gas kinetic temperature of the plasma, while simultaneously considering practically all major background ions.

Highly efficient scintillation Lu2SiO5 -z:Y3+:Ce3+:Ca2+ crystals are grown from 20 to 85% of the initial melt using the Czochralski method. Crystallization of less than 50% of the melt residues in the iridium crucible leads to its deformation and short operating time. Optimized parameters of the growth process and the composition of the initial melt make it possible to grow crystalline boules with a diameter of 75-80 mm. The scintillation properties of elements measuring 3 x 3 x 20 mm for time-of-flight positron emission tomography (TOF PET), made of the upper and lower parts of a boule weighing 5 kg, are studied.

ESR spectra of asphaltenes from a series of crude oils from the Devonian and Carboniferous deposits of the South-Tatar Dome in Tatarstan with low vanadium content and of vanadiferous crude oils from deposits of the Melekess depression in Tatarstan are analyzed. For asphaltenes from Devonian oils, the correlation between the concentrations of stable free radicals (SFR) and vanadyl complexes (VCs) has direct trend, whereas for asphaltenes from Carboniferous oils the trend is inverse. Taking into account the previously revealed inverse trend for asphaltenes of vanadium-enriched highly viscous crude oils [ 1 ], the opposite trends in SFR–VC correlations (direct and inverse) suggest different structures of asphaltene molecules in oils with different vanadium content and, correspondingly, different sources and conditions of the formation of oil deposits. Specific features of the ESR characteristics of asphaltenes of core and extractable oils and of oils from Devonian and Carboniferous deposits are revealed.

This paper reports results of mathematical modeling applied to the stress and strain in epicentral zones before and after the large earthquakes that occurred on June 22, 2002 in the Qazvin Province, northwestern Iran (Mw = 6.4) and the Gujarat, India earthquake of January 26, 2001 (M = 6.9). The modeling relied on a method for calculating stress and strain in a blocky elastic isotropic heterogeneous medium disturbed by a set of faults that are due to an external tectonic stress field. The boundary conditions were specified based on geological and seismological data. It has been shown that the epicenters of large crustal earthquakes occur in zones of high stress concentration at the ends of tectonic faults. Rupture occurs when the relationship between acting tectonic stresses satisfies the requirement σyy/σxx >3, thus connecting zones of high stress. The evolution of the aftershock process is controlled by the stress drop caused by a new rupture, while the resulting aftershock clusters are in spatial correlation with the stress drop zone. The new rupture propagates in the direction of dominant tectonic fault orientation in the region. We show a relationship to exist between rupture length and the possible retrospectively predicted location and magnitude of the earthquake depending on the elastic energy buildup and its possible release under specified structural tectonic conditions.

Introduction. A promising direction in solving the problem of increasing the recovery of diamonds with weak or anomalous luminescence is the use of modern technologies for modifying the spectral characteristics of diamonds with luminophore-containing reagents. Materials and methods. In the experiments, we used collections consisting of diamond crystals with weak and anomalous luminosity and grains of kimberlite minerals selected from the gravity enrichment concentrate. When evaluating the efficiency of fixing luminophores on the surface of diamonds, a vision-metric method was used in UV radiation with the determination of the proportion of surface areas covered with luminophores. The spectral and kinetic characteristics of diamond crystals and kimberlite grains were measured under laboratory conditions on a «Polus-M» separator. The separation of diamonds and kimberlite grains was carried out in the mode used in the industrial radar process. Results. The causes and regularities of the interaction of modifier reagents with kimberlite minerals, as well as the effect of dispersant reagents on the fixation of luminophores and the spectral and kinetic characteristics of kimberlite are determined. Discussion. It is shown that the fixation of an organic collector with luminophores on kimberlite minerals proceeds according to the adhesion mechanism with the formation of focal surface formations on hydrophobic minerals and point fixation on the surface of faces with low surface energy. It is shown that the high selectivity of the X-ray luminescence separation process is achieved at a surface concentration of the luminophores on diamonds of at least 15 % and a surface concentration of luminophores on kimberlite minerals of no more than 3%, controlled by the addition of reagents-dispersants. Conclusions. The article presents the results of studies of the mechanism and regularities of fixing luminophore-containing compositions on kimberlitic minerals in the presence of dispersant reagents. It was found that the addition of luminophore-containing reagents-modifiers of sodium hexametaphosphate, sulfonol, carboxymethylcellulose and liquid glass to the aqueous phase of emulsions provides an increase in the selectivity of fixing luminophores on the surface of diamonds and improves the performance of X-ray luminescent separation of diamond-containing products. A mode of increasing the selectivity of the action of an aqueous emulsion of the MLA-3 modifier reagent based on luminophore E-515-115-G5 has been developed by adding sodium hexametaphosphate to the emulsion aqueous phase at a concentration of 1-1.5 g/l, providing 90% recovery of weakly and abnormally luminous diamonds into the X-ray luminescent separation concentrate with a decrease in kimberlite yield by 33 %. The tested modifier agents and the selected conditions of their application can be useful in industrial conditions for the X-ray luminescent separation of diamond-containing kimberlites. Resume. As a result of the studies, a mode was developed to increase the selectivity of the action of an aqueous emulsion of the MLA-3 modifier reagent based on the E-515-115-G5 luminophore with the addition of a dispersant reagent (sodium hexametaphosphate) to the aqueous phase of the emulsion at a concentration of 1-1.5 g/l , providing the possibility of 90 % extraction of weakly and abnormally luminous diamonds into the concentrate of X-ray luminescent separation while reducing the yield of kimberlite by 33 %. Suggestions for practical application and direction for future research. The developed reagents-modifiers and the selected conditions for their use are recommended for testing and implementation in industrial conditions.

The authors have correlated the fluorescence spectrum with the spectrum and kinetics of X-ray luminescence of organic collectors. The correlations prove applicability of organic collectors with modifying agents. From the integrated evaluation of organic liquids by the criteria of their adhesion capacity relative to diamonds and extraction capacity relative to inorganic luminophores, the selected organic collectors are: diesel, heavy gasoil of catalytic cracking, and their mixture. The spectral functions of organic luminophores contained in organic collectors are replaceable with polyaromatic hydrocarbons which generate intense signals similar to the signals of organic luminophores. Efficiency of modifying agents containing organic collectors and hydrophobic luminophores E-515-115-G5 and FL-530-GZ is high. The test organic collector was heavy gasoil of catalytic cracking and diesel fraction at a ratio of 61–9:1. Recovery of weakly and abnormally fluorescent diamonds was 80–90

Redox properties of bis(1-naphtylimino)acenaphthene have been studied using various voltammetry techniques. Radical anion of diimine ligand has been obtained in situ through electrochemical reduction, and its optical properties have been studied. A new sodium complex having the anion-radical form of bis(1-naphthylimino)-acenaphthene has been obtained and structurally characterized. We have found that the solvent nature affects the long-wavelength absorption band of the sodium complex, which is determined by the contribution of the coordinated solvent molecules to the lowest unoccupied molecular orbital (LUMO) energy.

The found interaction mechanism between a mineral–diamond mixture and a modifying agent includes the stage of adhesive attachment of luminophore at grains of diamonds and kimberlite. The selected compositions of modifying agents and the modification process parameters ensure efficient attachment of luminophore-bearing compositions at diamonds. The proposed criterion of selective action of modifying agent on spectral characteristics of diamonds enable choosing modes of recovery of weak and high luminous diamonds from kimberlite ore in X-ray luminescence separation. The rational variation parameters are determined for the organic collector composition, water phase of a modifying agent and for the process of modifying treatment of diamond–kimberlite products before the X-ray luminescence separation. The test of the selected compositions of modifying agents and the diamond-bearing product treatment modes proved almost complete extraction of weak and high luminescence diamonds to concentrate at minimized yield of kimberlite.

One of the research areas focused on improving the efficiency of diamond-bearing kimberlite beneficiation processes involves the utilization of technology aimed at enhancing the recovery of weakly and anomalously luminescent diamonds during the X-ray luminescence separation process using luminophore-containing chemical agents. The objective of this research was to select the optimal composition of agents that modify the spectral characteristics of minerals and the conditions for their application. A crucial factor for process efficiency is the effective attachment of modifying agents to diamond crystals while avoiding similar attachment to kimberlite mineral surfaces. This is achieved through the use of organic collectors with an optimal composition, characterized by their ability to both adhere to the diamond surface and retain inorganic luminophore grains. The evaluation of luminophore attachment efficiency was performed using visiometric analysis in the UV range. The capability of diamonds to retain luminophore collector droplets or films on their surfaces was evaluated using a technique to measure the three-phase limiting wetting angle. The spectral and kinetic characteristics of diamonds and their recovery during the X-ray luminescence separation process were determined using a separator “Polyus-M”. The feasibility of purposefully modifying the spectral characteristics of weakly and anomalously luminescent diamonds through luminophore-containing compositions based on zinc sulfides and zinc orthosilicate has been confirmed through the conducted studies. By considering the criterion of selectivity in the attachment of luminophore emulsion to diamonds and kimberlite minerals, calculated based on the measured surface concentrations of luminophores on the minerals, the optimal ratios between the masses of inorganic luminophore, organic collector, and the aqueous phase of the emulsion were determined. Dispersing agents that offer selective binding of luminophores to diamond crystals were identified, and rational parameters for the composition of the organic collector were established. The temperature range for treating diamond-containing material was defined. As a result of bench testing the modifying agents with the selected composition and conditions for their application in the diamond-containing material treatment cycle before XRF separation, it was confirmed that the recovery of anomalously and weakly luminescent diamonds could exceed 90%, while keeping the yield of kimberlite minerals in the concentrate below 1%.

The feasibility of targeted modification of the spectral properties of weakly and anomalously luminescent diamonds by modifying reagents containing luminophores based on sulfides and zinc orthosilicate, characterized by medium and low deviation of the luminescence signal from that of natural diamond. It was found that the hydrophobic treatment of inorganic luminophores with potassium butyl xanthate could increase the recovery of anomalous luminescent diamonds in the process of X-ray luminescence separation up to 80%. Organic collectors (optically transparent oil products with high extractability for luminophores and adhesion to diamonds) based on technical-grade diesel fuel and catalytically cracked heavy gas oil are recommended for the luminophorecontaining compositions. The feasibility of reducing the fixation of luminophores on the surface of kimberlite grains using sodium hexametaphosphate, sulfonol, carboxymethylcellulose and liquid glass was demonstrated. The application of these reagents in low-salinity water provides decreasing coating of kimberlite grains with luminophores while maintaining the required concentration of luminophores on the surface of diamonds. Semi-industrial tests with an LS-D-4-03N separator proved the possibility of complete recovery of weakly and anomalously luminescent diamonds after treatment of XRS tailings with the modifying reagents.

The products from the reaction of petroleum asphaltenes with sulfuric acid under various conditions, accompanied by oxidation, sulfonation, and decomposition reactions, were studied. The change in the content of stable free radicals and vanadyl complexes in the products from the reaction of asphaltenes with sulfuric acid in relation to the time and temperature was determined by EPR spectroscopy. The chemical processes in the reaction of asphaltenes with sulfuric acid take place most strongly in the first hour, being accompanied by peak growth of the concentration of stable free radicals. With increase in the length of treatment of the asphaltenes with sulfuric acid there is a decrease in the concentration of stable free radicals accompanied by a decrease in the content of sulfo groups in the products. After only 30 min of the process there was a marked decrease in the content of vanadyl complexes in the reaction products.

This article presents the seismotectonic consequences of the strong Maule earthquake in Chile, which occurred on February 27, 2010 at Mw = 8.8. The consequences are considered as a manifestation of a large-scale fragment of the general seismotectonic process on the western edge of the South American plate (Chilean sector). Our study shows that manifestations of postseismic processes of the Maule earthquake cover a much larger area compared to the epicentral zone of the aftershocks. Based on the comparison of the results of numerical modeling of the stress–strain state before and after the earthquake, seismological, geodetic, and satellite data, an alternative model of the development of the seismotectonic process in the Chilean sector of the South American plate was proposed. Stress–strain modeling was performed by the finite-element method. The source of the Maule earthquake, at a depth of 33 km, falls into the region of relatively high values of compression stresses and positive maximum shear stresses. It was shown that other strong earthquakes of the Chilean sector in the interval of depths from 20 to 50 km are caused by high concentration of tectonic stresses in the region of transition from oceanic to continental lithosphere. Within the framework of the proposed model of the seismotectonic process ruptures weaken the contact between the oceanic and continental lithosphere after strong earthquakes. Abrupt sinking of the continental lithosphere into the mantle causes an increase in viscous melt pressure, promotes penetration into mega-cracks, and rises to the surface, causing subsequent volcanic eruptions. The results obtained in comparison with the coseismic consequences of earthquakes do not contradict these results of numerical modeling and give new insights into the structure of the lithosphere in the continent‒ocean transition zone and the development of the seismotectonic process.

In this work chromia-alumina catalysts have been studied by the electron paramagnetic resonance (EPR) spectroscopy in the temperature range-120-200 ?. It was observed, that the activity of the catalysts in the dehydrogenation of n-butane and i-butane correlates with the amount of strongly interacting Cr3+ ions of the amorphous chromia phase. A disproportionate increase in the antiferromagnetic coupling energy delta E between Cr3+ ions was shown in the concentration range 4.7-9.8%wt.Cr (from 210 to 420 cm(-1)) and 9.8-13.3%wt.Cr (from 420 to 450 cm(-1)). It was established, that an increase in the exchange interaction between Cr3+ ions is more favourable for the dehydrogenation of i-butane as compared to n-butane.

Stepwise oxidation-sulfonation of vacuum residue asphaltenes was carried out. It was shown that oxidation leads to the formation of carboxyl groups around the perimeter of the polyaromatic core. By contrast to ammonium persulfate, potassium dichromate oxidizes to a greater extent the sulfur atoms in the composition of asphaltenes which undergo desulfurization in an acidic medium. In the oxidation-sulfonation products the C/H parameter increases by a factor of 2.1, and the O/C parameter, by a factor of 19. The reaction of sulfonation of the oxidized asphaltenes proceeds less efficiently than that of the initial asphaltenes, as expressed in the value of the total static exchange capacity. Complexes of the oxidation-sulfonation products of asphaltenes with divalent copper cations were converted to redox ion-exchange materials by subsequent reduction with sodium dithionite in an alkaline medium.

The authors study the processing behavior of luminophore-containing blends of zinc and cadmium chalcogenides with a view to using them for the modification of the kinetic and spectral characteristics toward enhanced recovery of weakly and abnormally luminescent diamonds usually lost in X-ray luminescence separation. It is shown that zinc and cadmium sulfides activated by copper and silver have the kinetic and spectral characteristics which are the most similar to natural diamonds. The procedure developed for the improvement of the processing behavior of luminophores with zinc and cadmium sulfides includes the circuits of surface activation with copper cations and subsequent treatment in the potassium butyl xanthate solution. The visiometric analysis reveals that the increased oil receptivity of luminophores and the dispersing agents ensure selective attachment of luminophores to diamonds. The bench testing proves feasibility of complete extraction of diamonds to concentrate, including weakly and abnormally luminescent crystals.