The Siberian Traps volcanism is widely considered the main cause of the end-Permian mass extinction, the greatest biological crisis in the Earth history. While the extinction is interpreted as ...catastrophic and sudden with estimates of duration of approximately 35–40 thousand years from marine strata in South China, various lines of evidence have emerged for a more complex, prolonged, and diachronous extinction pattern. We present here the results of a multidisciplinary study of the Permian-Triassic continental transition in the Kuznetsk Basin, Russia. The region is proximal to the Siberian Traps LIP and the detrimental effects of the flood basalt volcanism in the Kuznetsk Basin may have been of similar scale as in the main area of the Siberian Traps distribution (Tunguska and Taymyr regions). Whereas earlier work has placed the Permian-Triassic boundary position between the coal-bearing Tailugan Formation and the volcanoclastic Maltsev Formation, here we revised the traditional model using three independent methods: radioisotopic CA-IDTIMS U-Pb zircon ages, δ13Corg isotope values and paleomagnetic proxies. The regional extinction of the humid-dominated forest flora (cordaites) and the aridity-induced biotic turnover in the Kuznetsk Basin occurred 820 kyr earlier than the end-Permian extinction event recorded in South China at 251.94 Ma. The biota in Kuznetsk Basin at the turnover subsequently diversified (with some exceptions) across the Permian-Triassic transition.
By compiling a large taxonomic database, we find that marine and terrestrial biotic diversity in Siberia progressively increased from the beginning of the Permian up to the middle Roadian (early Guadalupian global glacial event). After that time, the diversity at the species and generic level progressively and slowly declined towards the aforementioned latest Changhsingian (252.76 Ma) biotic turnover. Starting from this time, the biota rapidly diversified in the latest Changhsingian and Early-Middle Triassic. We suggest that the Permian-Triassic mass extinction mostly occurred in the tropics and subtropics due to the strong climatic warming, which was relatively low in late Changhsingian and gradually but quickly extends in the latest Changhsingian to an abnormally high temperature and extremely low oxygenated water in the oceans that was deadly for most marine animals. The warm climate shift poleward during Permian-Triassic transition in the middle-high latitudes caused the replacement (turnover) of the humid-related biotas by the dry climate-related and more diverse communities, which continued to expand throughout the Triassic in both marine and terrestrial habitats. The pattern of the Permian-Triassic event in both marine and terrestrial habitats was more intricate in terms of extinction, turnover, and diversity of biota within the different climatic zones and environmental habitats than has been generally considered.
•Permian-Triassic transition in Kuznetsk Basin (Russia) constrained with CA-IDTIMS dates.•Regional biota evolutionary turnover in the region occurs 820 kyr earlier than in South China.•The biota in Kuznetsk Basin diversified across the Permian-Triassic transition.•Permian-Triassic extinction mostly occurs in the tropics due to the strong climatic warming.•Siberian basalts as a cause of the extinction at the P-T boundary remain questionable.
New hybrid materials based on Pt, Fe, and Pt–Fe nanoparticles stabilized in a matrix of polymethylsilsesquioxane nanogel and ultrahigh molecular weight polyethylene (UHMWPE) were prepared. Metal ...vapor synthesis was used to produce mono- and bimetallic nanoparticles. It was shown that organosilicon nanogel effectively stabilizes Pt nanoparticles with an average size of 0.9 nm. Using the nanogel results in the formation of superparamagnetic Fe particles 3–5 nm in size that consist of ferromagnetic Fe
0
core and antiferromagnetic shells of Fe oxides. It is established that using an organosilicon matrix in the formation of Pt-Fe/UHMWPE systems helps reduce the average particle size of Fe in the material from 6.5 to 4.5 nm and narrow their particle size distribution. The composition, magnetic and electronic characteristics of the nanocomposites are studied via transmission electron microscopy, X-ray photoelectron spectroscopy, Mössbauer spectroscopy, XANES, and EXAFS.
The present work introduces nanocomposites based on carbon materials of various nature and hexarhenium chalcogenide clusters as surface modifiers of screen-printed graphite electrodes for ...amperometric immunosensing of the tricyclic antidepressant desipramine. The surface modification of the electrodes by chronoamperometric reduced graphene oxide in combination with chalcogenide hexarhenium clusters or nanodiamonds was developed for the determination of desipramine. The properties of the nanocomposites studied by voltammetry and electrochemical impedance spectroscopy (EIS) were correlated with the roughness parameters of their modified surface associated with the height properties of the irregularities estimated by atomic force microscopy. The composition of the hybrid nanostructures was optimized to provide the following analytical figures of merit for the immunosensors: the range of working concentrations from 1 × 10
−4
to 1 × 10
−9
М and the lower limit of the determined concentrations of (5-8) × 10
−10
М. The optimal parameters for sequential injection analysis were obtained at a flow rate of 25 µl s
−1
and the injected volume of 3125 µl of the supporting buffer at pH 7.5. It is possible to determine lower concentrations of desipramine equal to (7-9) × 10
−11
M using the proposed immunosensors in the flow mode. The testing of the developed immunosensors was characterized by the determination of the analyte in a pharmaceutical preparation and in urine. The relative standard deviation was less than 0.072.
A service is described that makes possible the effective construction of a three-dimensional ionospheric model based on the data of ground receivers of signals from global navigation satellite ...positioning systems (GNSS). The obtained image has a high resolution, mainly because data from the IPG GNSS network of the Federal Service for Hydrometeorology and Environmental Monitoring (Rosgidromet) are used. A specially developed format and its implementation in the form of
SQL
structures are used to collect, transmit, and store data. The method of high-altitude radio tomography is used to construct the three-dimensional model. The operation of all system components (from registration point organization to the procedure for constructing the electron density three-dimensional distribution and publication of the total electron content map on the Internet) has been described in detail. The three-dimensional image of the ionosphere, obtained automatically, is compared with the ionosonde measurements, calculated using the two-dimensional low-altitude tomography method and averaged by the ionospheric model.
A method for assaying nitrofuran drugs (furazolidone, furadonine, and furagin) using an amperometric biosensor based on a printed platinum electrode and immobilized monoamine oxidase was developed ...for analysis of medicinal formulations and urine. Nitrofuran derivatives were found to have inhibitory actions, albeit weaker than those of classical tricyclic antidepressants, on the catalytic activity of monoamine oxidase. This side-effect inhibitory action allowed assay of furazolidone, furadonine, and furagin with lower detection limits, which were 8.3 × 10
−9
, 8.5 × 10
−8
, and 9.4 × 10
−10
M respectively. The results obtained here show that this side effect of furazolidone, furadonine, and furagin must be taken into consideration when these agents are prescribed to patients.
A significant proportion of publications related to the ionospheric disturbances that arise during earthquake preparation over the regions of their preparation refer to these disturbances as ...anomalies. In this case, the identification of the ionospheric precursor is actually based on an estimate of the amplitude of the deviation of the ionospheric parameters from the undisturbed value. We propose a completely different approach based on the physical mechanism of the generation of disturbances created by the interaction of the ionosphere with the lithosphere and atmosphere. At the same time, this interaction gives the observed variations unique properties that are typical only for earthquake precursors, based on which the precursors are identified with an intelligent algorithm. Another advantage of this approach is that the method, which we call “cognitive identification”, does not require large deviations from unperturbed values, since it is based on recognition of the “image” of the precursor. It is created in a way that considers morphological features of the precursors and can be effectively used even at low values of the signal/noise ratio.
The control of the precise concentration of steroid hormones and their synthetic analogs in biomedical objects is a relevant analytical task. A method for selective and highly sensitive simultaneous ...amperometric determination of adrenaline, melatonin, and cortisol with the use of a two-detector flow-injection system is developed. Screen-printed carbon electrodes (SPE) with one or two working electrodes modified with a gold–palladium binary system that exhibits catalytic activity upon electrooxidation of the organic compounds under consideration are used as detectors. The high sensitivity of determination is attributed to the catalytic properties of the metal modifier: the transition from the metal to the binary system leads to an increase in the catalytic oxidation current of hormones. The selectivity of determination of adrenaline in the presence of melatonin and cortisol is provided by the difference in the oxidation potentials of the hormones on the proposed electrode. For selective determination of melatonin and cortisol, the surface of the modified working electrode is coated with a Nafion film. The difference of potentials of the peaks of oxidation of adrenaline, melatonin, and cortisol on such an electrode is 300 mV. The proposed method is tested in the analysis of urine samples. The flow-injection scheme is supplemented with a dialyzer and a chromatographic minicolumn to eliminate the interfering effect of electrophilic compounds. The linear bilogarithmic dependence of the analytical signal on the concentration of adrenaline, melatonin, and cortisol is observed in the ranges of 5.0 × 10
–10
–5.0 × 10
–3
, 5.0 × 10
–11
–5.0 × 10
–3
, and 5.0 × 10
–12
–5.0 × 10
–3
mol/L, respectively. Amperometric determination of the hormones in the flow-injection system leads to an increase in the productivity of the analysis and a decrease in the consumption of the sample and makes it possible to automate the process.
Various nanostructured materials (graphene, fullerene C
60
, carbon nanotubes, and cobalt nanoparticles as a label) are used as nanocomposites to modify the surface of primary signal ...converters (screen-printed graphite electrode) in the development of amperometric immunosensors for the determination of tricyclic antidepressant amitriptyline. The use of nanomaterials improved the analytical characteristics of the corresponding immunosensors. The range of working concentrations of the immunosensor is 1 × 10
–9
–1 × 10
–4
M, the lower limit of the analytical range is at a level of 5 × 10
–10
M. The binding constants of antigen–antibody immune complexes are determined. Immunosensors are tested in the control of contents of medicinal preparations in urine.
Amperometric monoamine oxidase biosensors based on screen-printed graphite electrodes modified with nanostructured reduced graphene oxide (RGO) composites and cobalt nanoparticles (CoNPs) were ...developed to determine antidepressant drug substances (tianeptine, thioridazine, and fluoxetine). Carbon nanomaterials with metal nanoparticles (nanocomposites) allow individual components to retain their properties but also ensure better quality of devices owing to joint contribution of constituents. The nanomodifier was applied to the surface of screen-printed graphite electrodes via dropwise evaporation. The RGO fastening on the surface is due to electrostatic interaction between RGO carboxyl groups and amine groups of the amine derivative on the platform of polyester polyol (H20–NH
2
). Cobalt nanoparticles were obtained using the electrochemical chronoamperometry method at a potential
E
= –1.0 V and different times of their accumulation (50 and 60 s) on the electrode surface. According to atomic force microscopy data, the CoNP size varies with the time of electrochemical deposition of NPs, achieving predominately (40 ± 2) and (78 ± 8) nm. The electrochemical impedance spectroscopy reveals the lowest values of the charge transfer resistance for RGO-chitosan/CoNP nanocomposites and RGO-amine derivative on the polyester polyol (H20–NH
2
)/CoNPs platform. The use of these nanocomposites in the electrode surface modification was found to significantly improve the analytical characteristics of biosensors, extending the operating concentration range from 1 × 10
–4
to 5 × 10
–9
mol/L, increasing the sensitivity and correlation coefficients, and decreasing the detectable concentration limit. Biosensors were shown to be promising in the quality control of antidepressants upon the determination of the main active substance in medicinal drugs and biological fluids. The lower limit of detectable concentrations of (7–9) × 10
–10
mol/L is attained by using tyramine as a substrate for the determination of fluoxetine, thioridazine, and tianeptine.
Materials based on copolymers of isobornylacrylate (IBA) with methylmethacrylate (MMA) or acrylonitrile (AN) have been synthesized by radical copolymerization using monomeric mixtures with different ...composition. The copolymer compositions were determined and relative activities of monomers were calculated by different methods. All copolymers have transparency up to 80% in the ultraviolet region. The mechanical and thermophysical properties of the copolymers depend on composition. The best combination of optical transparency and tensile strength is achieved in the copolymers containing 13% and 49% units of IBA (in the case of MMA and AN, respectively. The prospects of application of the copolymers as a matrix for creating photoinduced nanocomposites containing CdS are shown. Using the specially selected compounds of cadmium, materials with new optical properties were obtained by UV irradiation.
