Fractions of trace metals in the sediments of permafrost-affected lakes in Northern Siberia, Lena delta

Summary The aim of the study is to estimate the role of sediment components in the accumulation of microelements in lakes of the permafrost-affected area (the Lena Delta, northern Siberia). A fractional analysis of several trace elements (V, Cr, Co, Ni, Cu, Zn, Sn, and Pb) was conducted. Samples were collected from 10 lakes during the summer period of the “LENA 2019” expedition. The content of the chemical elements in the sediments was measured with the ICP-MS instrument. The results of the work show a relatively homogeneous distribution of the acid-soluble forms of the metals in sediments from different lakes. The content of trace elements in all the lakes studied is determined by natural (lithogenic) sources. Stable minerals inherited from the rocks play a crucial role in the sediment formation. Most of the elements are predominantly fixed in stable mineral and organometallic fractions. However, for V, Co, and Cr a high level of geochemical mobility was identified in some of the lakes. The metals of soluble complexes are capable of migrating from the sediments to the water due to physical and chemical changes in the aquatic environment. Furthermore, the organic substances and the Fe/Mn hydroxides of the sediments have a low potential ability to bind the metals into stable compounds.Цель исследования — оценка роли компонентов донных отложений в накоплении микроэлементов в озерах криолитозоны (дельта Лены, северная Сибирь). Проведен фракционный анализ некоторых микроэлементов (V, Cr, Co, Ni, Cu, Zn, Sn, Pb). Пробы были отобраны из 10 озер в летний период экспедиции «ЛЕНА 2019». Содержание химических элементов в осадках измеряли прибором ICP-MS. Результаты работы показали относительно однородное распределение кислоторастворимых форм металлов в донных отложениях разных озер. Большинство элементов преимущественно закреплено в устойчивых минеральных и металлоорганических соединениях. Однако для V, Co и Cr в некоторых озерах отмечен высокий уровень подвижности. Металлы растворимых комплексов способны мигрировать из донных отложений в воду за счет изменений физико-химических параметров водной среды. Кроме того, органические и минеральные вещества осадков обладают низкой потенциальной способностью связывать металлы в устойчивые соединения.

Shock Wave Structure for Argon, Helium, and Nitrogen

We compare the thickness of shock wave fronts at different Mach numbers, modeled via Navier-Stokes (NS) and Quasi-gasdynamic (QGD) equations, with experimental results from the literature. Monoatomic argon and helium, and diatomic nitrogen, are considered. In this modeling a finite-difference scheme with second-order spatial accuracy is employed. For argon the density thickness calculated via QGD and NS models are in good agreement with each other, and with the experimental results. For helium QGD and NS results agree well with those from the bimodal model. For nitrogen, the QGD results are closer to the experimental data than NS results. The QGD-based algorithm converges to the steady state solution faster than the NS-based one.Comment: 6 pages, 6 figure

Experimental and numerical investigation of an axisymmetric supersonic jet

21 pages, 10 figures, 2 tables.A comprehensive study of a steady axisymmetric supersonic jet of CO2, including experiment, theory, and numerical calculation, is presented. The experimental part, based on high-sensitivity Raman spectroscopy mapping, provides absolute density and rotational temperature maps covering the significant regions of the jet: the zone of silence, barrel shock, Mach disk, and subsonic region beyond the Mach disk. The interpretation is based on the quasi-gasdynamic (QGD) system of equations, and its generalization (QGDR) considering the translational–rotational breakdown of thermal equilibrium. QGD and QGDR systems of equations are solved numerically in terms of a finite-difference algorithm with the steady state attained as the limit of a time-evolving process. Numerical results show a good global agreement with experiment, and provide information on those quantities not measured in the experiment, like velocity field, Mach numbers, and pressures. According to the calculation the subsonic part of the jet, downstream of the Mach disk, encloses a low-velocity recirculation vortex ring.This research was supported by the Spanish Dirección General de Investigación Científica y Enseñanza Superior (DGICYES), Research Projects PB94{1526 and PB97{1203, and by the Fund for Fundamental Investigations of the Russian Academy of Sciences N 98-01-00155.Peer reviewe

ASCORBIС ACID DEGRADATION IN N, N-DIMETHYLFORMAMIDE SOLUTIONS

Objective: Investigate the mechanisms of L-ascorbic acid transforтmation and formation of coloured enamines in N, N-dimethyl-formamide solutions. Methods: An automatic polarimeter Atago POL-1/2 was used for polarimetric investigation. Electronic spectra were recorded by UV-spectrometer Cary 60 (Agilent). The statistical analysis was carried out using the OriginPro 9.1 packages. Results: The Biot’s law violation was found in below 0.1% solutions of L-ascorbic acid (AA) in N, N-dimethylformamide (DMF). During the day, the specific rotation   of 1% AA solution varied from+37 to-1.0. Gradually, the solution acquired the red colour, and its intensity depended on the AA concentration. Spectrophotometrically, it was shown that after 15 min AA was absent in the n·10-3% solutions. The decomposition followed the first-order kinetics (k1=1.83·10-2с-1). At the same time, new absorption bands appeared at 273, 390, 533 nm. Model solutions containing dimethylamine (DMA) had a similar spectrum, and the intensity of the absorption bands increased in proportion to the concentration of DMA. Conclusion: The results show that the first step in the decomposition of ascorbic acid AA in DMF follows first-order kinetics. Numerous decomposition products are optically active compounds and reverse the sign of the optical rotation of the solution. The water resulting from the decomposition of AA is involved in the hydrolysis of the solvent. The hydrolysis product, the secondary amine DMA, interacts with the carbonyl groups of the AA decomposition products to form coloured enamines. Magnesium (II) accelerates the formation of coloured products

Detection of rifampicin and izoniazid resistance in Mycobacterium tuberculosis strains from Samara Region (Central Russia)

Recently high rates of tuberculosis incidence and prevalence are observed in civilian and prisons sectors in Russia. One of the main reasons for high morbidity levels and ineffectiveness of treatment is wide spreading of drug resistant Mycobacterium tuberculosis strains, but accurate and comprehensive information on levels of drug resistance among strains circulating in Central Russia is unavailable. Rifampicin and izoniazid resistance detection in TB isolates from Samara (Central Russia) civilian and prison TB hospitals and dispensaries in 2000–2002 by revealing mutations in rpoB, katG and inhA genes using Macroarray technique. Methods: A total of 342 M. tuberculosis isolates were tested using Macroarray method. It is based on multiplex amplification of rpoB, katG and inhA genes fragments (with three pairs of biotin labeled primers) following by dothybridization with normal and mutant oligonucleotide probes (fragments of rpoB, katG and inhA genes in which mutations occur) immobilized on nylon membrane strips. Mycobacterial DNA was extracted by heating of cell suspensions following by chloroform extraction. Streptavidin-alkaline phosphatase color development system was used for visualization of results

Revealing the diversity of Fusarium micromycetes in agroecosystems of the North Caucasus plains for replenishing the State Collection of Phytopathogenic Microorganisms of the All-Russian Scientific Research Institute of a Phytopathology

In order to prevent crop yield losses from the most dangerous and economically important pathogenic organisms, it is necessary not only to monitor the virulence gene pool, but also to study the nature of pathogen variability and determine the potential for the emergence of new genes and races. This requires centralized collections of fungal cultures characterized by a set of stable strains to provide for phytopathological, immunological, breeding, genetic, toxicological, parasitological and other studies. The State Collection of Phytopathogenic Microorganisms of the ARSRIP is the State Depository of Phytopathogenic microorganisms that are non-pathogenic to humans or farmed animals. Currently, it has more than 4,500 accessions of plant pathogenic strains of fungi, oomycetes, bacteria, viruses, phytoplasmas, and the collection is updated annually. For this purpose, the study of the inter- and intraspecific genetic diversity of genus Fusarium was carried out in agricultural systems of the Krasnodar Territory. In 2020, the State Collection of Phytopathogenic Microorganisms was supplemented with 13 strains of Fusarium fungi isolated from tissues of winter wheat plants collected in several locations of the Krasnodar region. The complex of Fusarium fungi revealed on winter wheat usually included Fusarium oxysporum, F. culmorum, F. lolii, F. graminearum, F. fujikuroi, F. sporotrichioides, etc. The effect of the preceding crop on the frequency of Fusarium species isolated from winter wheat was observed. After series cloning of collected isolates, 21 strains of different fungal species characterized by stable morphology traits and known pathogenic and phytotoxic properties were selected for collection replenishment. Significant differences in pathogenic activity were revealed between fungi belonging to either the same or different species; the manifestation of this activity varied from the absence of any effect of spore suspensions on seedling development to a complete inhibition of their growth. The phytotoxic activity towards wheat seedlings varied from medium to high. Species possessing a high intensity of phytotoxic activities are the most dangerous for wheat, since they promote accumulation of dangerous phytotoxins in plant tissues

A characteristic of the species composition of pathogenic fungi of the genus <i>Fusarium</i> in corn biocenoses of the Voronezh region

Corn is one of the main crops of modern world agriculture. It ranks f irst in terms of gross grain harvests and second in terms of acreage, ceding only to the main grain crop of the globe, wheat. The problem of increasing the production of grain and green mass of corn remains one of the urgent tasks of agricultural production. High potential yields very often remain untapped due to diseases, direct losses from which are estimated at 20–50 %. The purpose of this work was to study the species composition of micromycetes on corn collected in different phases of vegetation in May-July 2020 in the Voronezh region, to identify phytopathogenic genus Fusarium fungi, to study pathogenic and phytotoxic strains of the fungi to replenish the collection of the All-Russian Scientific Research Institute of a Phytopathology. Preservation of infectious material of fungi from the genus Fusarium is of no small importance for phytopathological, immunological, breeding, genetic and toxicological studies. As a result of the mycological studies carried out, a lot of fungi isolates from the genera Fusarium, Aspergillus, Cladosporium, Curvularia, Penicillium, Rhizopus, Periconia, Pythium, Trichothecium, etc., isolated from the affected roots, stems and ears of corn in the Voronezh region in 2020 were identif ied. Fungi isolates from seven taxonomic groups: Fusarium fujikuroi Nirenberg (F. moniliforme, F. verticillioides), Fusarium oxysporum Schltdl., Fusarium culmorum (Wm.G. Sm.) Sacc., Fusarium graminearum Schwabe, Fusarium heterosporum Nees &amp; T. Nees (F. lolii ), Fusarium roseum Link (F. sambucinum), Fusarium sporotrichioides Sherb. were tested for pathogenicity and phytotoxicity on seedlings of plant-testers. It has been shown that pathogenic and phytotoxic activity in fungi varies signif icantly between Fusarium species and within the same species. The greatest danger to corn is represented by the species F. sporotrichioides, F. graminearum, F. culmorum, F. fujikuroi, F. oxysporum, F. heterosporum, which have a high intensity of phytotoxic activity associated with the fact that they contribute to the synthesis and accumulation of dangerous toxins in plant tissues. As a result of the conducted studies, 55 strains of fungi from the genus Fusarium belonging to seven species were selected. The isolates, stable in morphological and cultural characteristics and studied for pathogenicity and toxicity, were placed for long-term storage in the Russian State Collection of Plant Pathogenic Microorganisms and Cultivars for Identif ication of Phytopathogenic Microbial Strains at the All-Russian Scientif ic Research Institute of a Phytopathology

Design Features of Nuclear Power Plants

Уровень безопасности и надежности эксплуатации атомных электростанций определяется качеством разработки проектной документации на объектах использования атомной энергии. Именно на этапе проектирования закладываются основы безопасной эксплуатации АЭС, поэтому главные задачи этого этапа — наиболее полный учет в проекте требований и принципов безопасности, использование систем безопасности и таких проектных решений, при которых реакторная установка обладает свойствами самозащищенности.The level of safety and reliability of operation of nuclear power plants is determined by the quality of development of design documentation for the construction and installation of equipment at nuclear power facilities. It is at the design stage that the foundations for the safe operation of nuclear power plants are laid, therefore, the main tasks of this stage are the most complete consideration of safety requirements and principles in the project, the use of safety systems and design solutions in which the reactor plant has self-protection properties

Interpolymer complexes based on Carbopol^® and poly(2-ethyl-2-oxazoline) as carriers for buccal delivery of metformin

Introduction. Buccal drug delivery has a number of advantages over oral administration: ease of application, good blood supply to the buccal mucosa, drug can enter the systemic circulation directly, avoiding the "first pass effect through the liver", and are not exposed to the acidic environment of the gastric juice and the destructive action of digestive enzymes. The use of interpolymer complexes (IPCs) makes it possible not only to ensure adhesion to the mucosal membranes of the oral cavity, but also to achieve a prolonged release of drugs.Aim. Development of carriers based on interpolymer complexes using Carbopol® 971 NF (C971) and poly(2-ethyl-2-oxazoline) (POZ) of different molecular weights for buccal delivery of metformin (MF).Materials and methods. The study of IPC adhesion was carried out using a TA.XTplus texture analyzer (Stable Micro Systems, UK); mucin compacts with a diameter of 13 mm were used as a substrate; these were prepared by compressing porcine gastric mucin powder using a manual hydraulic press for IR spectroscopy (PerkinElmer, USA) at a pressure of 2.45 MPa. The study of the swelling capacity was carried out by placing polymer matrices in an artificial saliva medium, with constant thermostating at a temperature of 37.0 ± 0.5 °C for 5 hours. The study of the release of MF from the matrices based on IPC was carried out using a DFZ II apparatus (Erweka, Germany) according to the Flow Through Cell method (USP IV) with cells for tablets (22.6 mm) and adaptors for ointments, creams and gels in a medium simulating saliva. The concentration of MF in the samples from the dissolution tests was determined with UV-spectrophotometry (Lambda, PerkinElmer, USA) at 232.8 nm.Results and discussion. In a comparative study of the mucoadhesive properties of polymer samples, IPC compacts showed a mucoadhesion capacity comparable to that of poly(2-ethyl-2-oxazoline); at the same time, compacts from physical mixtures (PM) and C971 are inferior in terms of the separation force to IPC samples, however, POZes dissolve in an artificial saliva medium, that is, they are not suitable as dosage forms for buccal delivery. For 5 hours of the experiment to assess the swelling capacity, the IPC matrices did not change significantly, which can ensure their comfortable use as carriers for buccal delivery. When evaluating the release of metformin from polymer matrices (with weight ratio MF/IPC 1: 0.5), the most complete release (more than 90 %) is observed from both IPC matrices compared to matrices of PM and individual polymers.Conclusion. Polycomplex matrix systems based on C971-POZ (50 kDa) and C971-POZ (500 kDa) are suitable for buccal delivery of metformin