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The study is focused on the genetic determinants of the yersiniachelin (Ych) siderophore encoded by the ysu gene cluster and found only in Yersinia pestis and Yersinia pseudotuberculosis. The aim of the investigation was to analyze the genes encoding the biosynthesis of Ych and to assess the possibility of their use for intraspecies differentiation of Yersinia. Materials and methods. The study used complete nucleotide sequences of 583 Y. pestis strains and 300 Y. pseudotuberculosis strains from the NCBI database, as well as 38 Y. pestis and 88 Y. pseudotuberculosis strains from culture collection at the Rostov-on-Don Anti-Plague Institute of the Rospotrebnadzor. The genomes were analyzed using bioinformatics methods and PCR in silico and in vitro. Results and discussion. A comparison of the ysu cluster genes in two Yersinia species has revealed their high conservatism in the plague microbe, while differences in the structure of the transcription terminator of the Ych biosynthesis genes have been found in the pseudotuberculosis microbe. It turned out that the terminator contains nucleotide tandem repeats that differ in the number in different groups of Y. pseudotuberculosis strains, thus indicating their potential use for intraspecies differentiation of these bacteria. To assess the effect of the transcription terminator structure on the Ych expression by plague and pseudotuberculosis microbes, two recombinant plasmids containing PCR copies of Ych biosynthesis operons from Y. pestis KIM and Y. pseudotuberculosis YPIII have been constructed. The introduction of both plasmids into the Escherichia coli H1884 strain, devoid of its own siderophores, has demonstrated that the operon of the YPIII strain determines a significantly higher expression of Ych than that of the KIM strain. The results of the study show that the structure of the transcription terminator of the Ych biosynthesis operon has a considerable impact on the expression of this siderophore and can be used for intraspecies differentiation of Y. pseudotuberculosis strains during epidemiological monitoring.

Nonlinear force-free extrapolations are a common approach to estimate the 3D topology of coronal magnetic fields based on photospheric vector magnetograms. The force-free assumption is a valid approximation at coronal heights, but for the dense plasma conditions in the lower atmosphere, this assumption is not satisfied. In this study, we utilize multiheight magnetic field measurements in combination with physics-informed neural networks to advance solar magnetic field extrapolations. We include a flexible height-mapping, which allows us to account for the different formation heights of the observed magnetic field measurements. The comparison to analytical and simulated magnetic fields demonstrates that including chromospheric magnetic field measurements leads to a significant improvement of our magnetic field extrapolations. We also apply our method to chromospheric line-of-sight magnetograms from the Vector Spectromagnetograph (VSM) on the Synoptic Optical Long-term Investigations of the Sun (SOLIS) observatory, in combination with photospheric vector magnetograms from the Helioseismic Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). The comparison to observations in extreme-ultraviolet wavelengths shows that the additional chromospheric information leads to a better agreement with the observed coronal structures. In addition, our method intrinsically provides an estimate of the corrugation of the observed magnetograms. With this new approach, we make efficient use of multiheight magnetic field measurements and advance the realism of coronal magnetic field simulations.

Pathogenic bacteria use low-molecular-weight iron chelators – siderophores – to assimilate iron in the host body. Being recognized as virulence factors, these molecules, differing in structural and functional properties, are the subject of the most intensive research in medical microbiology. The present study is devoted to the investigation of yersiniachelin siderophore (Ych) found in the causative agent of plague, Yersinia pestis. The aim of the work was to clarify the role of Ych in the physiology of Y. pestis by comparing the properties of three strains of the plague microbe, differing in Ych production. Materials and methods. Three variants of Y. pestis EV76 strain were used in the experiments: parent strain Y. pestis EV76, its mutant that does not produce Ych due to deletion of three siderophore biosynthesis genes (analogues of ypo1530–1532 in Y. pestis CO92 strain) and a complemented mutant that was transformed by a recombinant pSC-A-5EV plasmid containing Ych biosynthesis genes cloned into the high-copy plasmid vector pSC-A-amp/kan. Comparative analysis of the three strains was carried out in terms of colony morphology, siderophore activity, growth rate, and sensitivity to hydrogen peroxide. Results and discussion. The comparison of these strains has revealed that the secretion of Ych by bacteria at 26 °С ensures the assimilation of iron. At 37 °С, Ych is not secreted into the medium and protects bacteria from the bactericidal action of reactive oxygen compounds. Thus, the study shows that yersiniachelin is able to stimulate the assimilation of iron by bacteria under iron-deficit conditions and has antioxidant properties.

The aim of this study was to develop a new method of intraspecific genetic differentiation of Yersinia pseudotuberculosis, based on the detection of INDEL-markers using PCR. Materials and methods. Analyzed were 308 strains from the NCBI database and 15 strains sequenced within the frames of this study. The nucleotide sequences of the strains were determined using the MiSeq technology platform. The genomes of the strains sequenced in the work, as well as genomes from the NCBI database, were assessed using in silico PCR with 7 pairs of primers designed in the study. As a result of a comparison of genome-wide sequences of 22 Y. pseudotuberculosis strains from the NCBI database, using the author’s software (GenExpert), 7 INDEL-markers were selected that make it possible to effectively distinguish between strains of the causative agent of pseudotuberculosis. Based on these markers, 7 pairs of primers were designed and synthesized for the analysis of different strains using PCR. Analysis of 323 strains in PCR in silico and 70 strains in PCR in vitro allowed for dividing them into 30 genetic groups. Comparison of the results of PCR in silico and in vitro confirmed the possibility of using the proposed primers for intraspecific differentiation of Y. pseudotuberculosis. Based on the data obtained, a dendrogram reflecting the phylogenetic relations of different strains of Y. pseudotuberculosis was constructed. When analyzing the distribution of Y. pseudotuberculosis strains by various clusters and genetic groups, a number of patterns were revealed. Conducted in silico and in vitro PCR show that the proposed method of INDEL-typing can be used for intraspecific genetic differentiation of the causative agent of pseudotuberculosis.

This review systematizes and analyzes the data published over the past decade, devoted to the study of low-molecular-weight high affinity iron chelators – siderophores. Siderophores, which are found in bacteria, fungi and mammals, are able to extract iron from insoluble inorganic compounds, and in the host organism – from complexes with proteins that perform the function of nonspecific protection of mammals from infections. The extracted iron is delivered to cells through surface protein receptors specific for each siderophore, as well as various protein transport systems that make up membranes. Siderophores play an important role in virulence in pathogenic bacteria, performing many functions in the host organism, in addition to providing microbes with iron and other biological metals. They participate in the storage of excess iron, toxic to cells, protect bacteria from reactive oxygen compounds, compete for iron with phagocytes, and have a harmful effect on host cells, acting as secreted bacterial toxin in some cases. Bacterial siderophores perform a signaling function and regulate both, their own synthesis and the synthesis of other virulence factors. Many pathogenic bacteria produce several siderophores that are active under different conditions, against various sources of iron in the host organism and at different stages of infectious process. The review presents the results of the experimental studies aimed at elucidating the structure and diverse functions of bacterial siderophores, the mechanisms of their biosynthesis and regulation of expression, as well as the role of these molecules in the physiology and virulence of pathogenic bacteria. Special emphasis is put on siderophores of bacteria causing particularly dangerous infections.

A joint campaign of several spaceborne and ground-based observatories, such as the GREGOR solar telescope, the Extreme-ultraviolet Imaging Spectrometer (EIS), and the Interface Region Imaging Spectrograph (Hinode Observing Plan 381, 2019 October 11–22) was conducted to investigate the plasma β in quiet Sun regions. In this work, we focus on 2019 October 13, 17, and 19 to obtain the plasma β at different heights through the solar atmosphere based on multiheight observational data. We obtained temperature, density, and magnetic field estimates from the GREGOR High-resolution Fast Imager, Infrared Spectrograph, Interface Region Imaging Spectrograph, and EIS and complementary data from the Solar Dynamics Observatory Atmospheric Imaging Assembly (AIA). Using observational data and models (e.g., FALC and PFSS), we determined the plasma β in the photosphere, chromosphere, transition region, and corona. The obtained plasma β values lie inside the expected ranges through the solar atmosphere. However, at EIS and AIA coronal heights (from 1.03 to 1.20 R _⊙ ), plasma β values appear in the limit defined by Gary; such behavior was previously reported by Rodríguez Gómez et al. Additionally, we obtained the plasma β in the solar photosphere at different optical depths from $\mathrm{log}\tau =-1.0$ to –2.0. These values decrease with optical depth. This work provides a complete picture of plasma β in quiet Sun regions through the solar atmosphere, which is a prerequisite of a better understanding of the plasma dynamics at the base of the solar corona.

For many years, communicative interactions between people have been the subject of conceptual and heuristic consideration in the frameworks of the psychological and social sciences. About ten years ago, the study of communicative interactions began using the methods of experimental neurosciences. Until now research in this area has focused on the accumulation of various phenomenа and the development of methodology. Basic directions and perspectives of communicative interactions research by means of experimental neuroscience methods and mathematical modeling have been considered.

Context. Coronal dimmings are regions of reduced emission in the lower corona observed in the wake of coronal mass ejections (CMEs), representing their footprints. Studying the lifetime evolution of coronal dimmings helps us to better understand the recovery and replenishment of the corona after large-scale eruptions. Aims. We study the recovery of dimmings on different spatial scales to enhance our understanding of the replenishment and dynamics of the corona after CMEs. Methods. In order to investigate the long-term evolution of coronal dimming and its recovery, we propose two approaches that focus on both the global and the local evolution of dimming regions: the fixed mask approach and the pixel boxes approach. We present four case studies (September 6, 2011; March 7, 2012; June 14, 2012; and March 8, 2019) in which a coronal dimming is associated with a flare/CME eruption. We analyzed each event with the same methodology, using extreme-ultraviolet filtergrams from the Solar Dynamics Observatory's Atmospheric Imaging Assembly (SDO/AIA) and Solar TErrestrial RElations Observatory's Extreme UltraViolet Imager (STEREO/EUVI) instruments. We identified the dimming region by image segmentation, then restricted the analysis to a specific portion of the dimming and tracked the time evolution of the dimming brightness and area. In addition, we study the behavior of small subregions inside the dimming area, of about 3 × 3 pixels, to compare the recovery in different regions of the dimming. Results. Three out of the four cases show a complete recovery 24 hours after the flare/CME eruption. The primary recovery mechanism identified in the observations is the expansion of coronal loops into the dimming region. The recovery of the brightness follows a two-step trend, with a steeper and quicker segment followed by a slower one. In addition, some parts of the dimming, which may be core dimmings, are still present at the end of the analysis time and do not recover within 3 days, whereas the peripheral regions (secondary dimmings) show a full recovery. Conclusions. The high temporal and spatial resolution of SDO/AIA observations combined with multi-view data of the STEREO/EUV instrument reveal high-situated coronal loops expanding after CME eruptions, which cover dimming regions and gradually increase their intensity. Our developed approaches enable the analysis of dimmings alongside these bright structures, revealing different timescales of recovery for core and secondary or twin dimming regions. Combined with magnetic field modeling, these methods lay the foundation for further systematic analysis of dimming recovery and enhance the knowledge gained from already-analyzed events. [ABSTRACT FROM AUTHOR]

The review presents brief analysis of the published over the past decade results of investigations devoted to studies of currently known molecular action mechanisms of Yersinia pestis virulence factors. Analyzed are different Y. pestis components, synthesized by the bacteria at four stages of infectious process in case of bubonic plague: in derma, lymph nodes, parenchymal organs, and blood. Described are the factors and mechanisms that induce microbe protection from bactericidal action of humoral and cell factors of innate host immunity, which effect the organism of animals in different ways, stimulating pro- or anti-inflammatory reaction of a host to the infection, and contribute to the shift of bacterial life cycle inside the host, providing for the transfer from intracellular propagation in phagocytes at early stages to extracellular propagation in lymph node, spleen, liver and blood at later stages. Discussed are only those factors of Y. pestis the interaction of which with host molecules and cells at different stages of infectious process in case of bubonic plague is experimentally proved.

Objective of the study is to investigate the role of resident plasmids pMT1, pCD1, and pPCP1 in the production of extracellular form of Yersinia pestis lipopolysaccharide (LPS).Materials and methods. The experiments have been performed using Y. pestis strain EV76 (pMT1, pCD1, pPCP1), carrying the whole plasmid set, as well as plasmid-free Y. pestis variant EV76 (pMT1-, pCD1-, pPCP1-), and isogenic clones, harbouring only one plasmid: Y. pestis EV76 (pMT1); Y. pestis EV76 (pCD1); Y. pestis EV76 (pPCP1). The presence of extracellular LPS in the incubation medium of Y. pestis EV76 cells has been confirmed by supernatant toxicity for laboratory animals and also by LAL-test reaction.Results and conclusions. It has been established that LPS extracellular form is produced by 37 °C Y. pestis EV76 cultures of the initial strain and its variants, carrying pMT1 or pPCP1 plasmid. Plasmid-free cultures and variant harbouring pCPP1 plasmid are deprived of such ability. The results of LAL-test has shown that the process of LPS separation from cell wall membrane into the environment is associated with translocation of proteins encoded by pMT1 and pCD1 plasmids and constitutes a natural form of existence of Y. pestis cells. The involvement of pCD1 plasmid in realization of the toxic potential of Y. pestis LPS has been established for the first time ever.

Aim. Elucidation of the role of extrachromosomal elements of heredity in manifestations of toxic properties of Yersinia pestis. Materials and methods. The study was carried out in vaccine strain Y. pestis EV76 (pMTl, pCDl, pPCPl) and non-plasmid variants of vaccine EV76 (pMTl\ pCDl', pPCPl') and virulent 231 (рМТГ, pCDl’, pPCPl') strains of Y. pestis. Presence of functionally active form of lipopolysaccharide (LPS) in the incubation medium of the bacteria was evaluated via toxicity of supernatant of Y. pestis for intact animals (infection-toxic shock) and mice sensitized by D-GalN. Results. 37°C cultures of Y. pestis EV76 containing a full amount of plasmids were established to release LPS into the environment. Non-plasmid variants of both vaccine and virulent strains of Y. pestis pMTl', pCD Г, рРСР 1 do not have this ability. Separation of LPS from cell wall was detected in live bacteria of plague infectious agent. This process is assumed to be coupled with translocation of proteins coded by pMTl, pCDl, pPCPl plasmids from the cell into the environment. Conclusion. Functional interconnection between extrachromosomal elements of heredity and toxic activity of Y. pestis LPS is established for the first time.

Предложена теоретико-игровая модель борьбы двух крупных партий за электорат в ходе предвыборной кампании. Доказано существование и единственность решения задачи выбора оптимальной стратегии распределения денежных средств по районам. На основе решения поставленной оптимизационной задачи в работе указывается решающее правило, которое определяет, какие средства вложить партии для выигрыша, когда информация о конкурентах носит лишь вероятностный характер.

Forecasting geomagnetic storms is highly important for many space weather applications. In this study, we review performance of the geomagnetic storm forecasting service StormFocus during 2011–2016. The service was implemented in 2011 at SpaceWeather.Ru and predicts the expected strength of geomagnetic storms as measured by Dst index several hours ahead. The forecast is based on L1 solar wind and IMF measurements and is updated every hour. The solar maximum of cycle 24 is weak, so most of the statistics are on rather moderate storms. We verify quality of selection criteria, as well as reliability of real-time input data in comparison with the final values, available in archives. In real-time operation 87% of storms were correctly predicted while the reanalysis running on final OMNI data predicts successfully 97% of storms. Thus the main reasons for prediction errors are discrepancies between real-time and final data (Dst, solar wind and IMF) due to processing errors, specifics of datasets.

Описано построение математических моделей в задаче определения местоположения объекта с учетом нелинейной зависимости измеряемых параметров от координат, в которых определяется движение объекта. Приводятся результаты сравнительного анализа алгоритмов идентификации априорно неопределенных параметров модели и адаптивного оценивания состояния объекта для моделей измерения, которые описываются линейными и нелинейными уравнениями.

Досліджено EUV хвилі за допомогою епіполярної геометрії. EUV хвиля ще досі вивчається і щодо неї існує чимало гіпотез. Відновлення просторової структури EUV хвилі дало б змогу пояснити її походження, фізичну природу та оцінити кінематичні характеристики. Запропоновано підхід, що грунтується на епіполярній геометрії для ідентифікації та узгодження об’єктів за стереозображеннями з космічних апаратів і визначення висоти хвилі. Показано, що є сегменти фронту хвилі, для яких задача встановлення відповідності стає некоректною і вироджується.

Context. The energy release in eruptive flares and the kinematics of the associated coronal mass ejections (CMEs) are interlinked and require favorable observing positions as both on-disk and off-limb signatures are necessary to characterize these events. Aims. We combine observations from different vantage points to perform a detailed study of a long duration eruptive C7 class flare that occurred on 17 April 2021 and was partially occulted from Earth view. The dynamics and thermal properties of the flare-related plasma flows, the flaring arcade, and the energy releases and particle acceleration are studied together with the kinematic evolution of the associated CME in order to place this long duration event in context of previous eruptive flare studies. Methods. We use data from the Spectrometer-Telescope for Imaging X-rays (STIX) onboard the Solar Orbiter to analyze the spectral characteristics, timing, and spatial distribution of the flare X-ray emission. Data from the Extreme Ultraviolet Imager (EUVI) onboard the Solar TErrestrial RElations Observatory-Ahead (STEREO-A) spacecraft are used for context images as well as to track the ejected plasma close to the Sun. With Atmospheric Imaging Assembly extreme ultraviolet (EUV) images from the Solar Dynamics Observatory, the flare is observed off-limb and differential emission measure maps are reconstructed. The coronagraphs onboard STEREO-A are used to track the CME out to around 8 R. Results. The flare showed hard X-ray (HXR) bursts over the duration of an hour in two phases lasting from 16:04 UT to 17:05UT. During the first phase, a strong increase in emission from hot plasma and impulsive acceleration of the CME was observed. The CME acceleration profile shows a three-part evolution of slow rise, acceleration, and propagation in line with the first STIX HXR burst phase, which is triggered by a rising hot (14 MK) plasmoid. During the CME acceleration phase, we find signatures of ongoing magnetic reconnection behind the erupting structure, in agreement with the standard eruptive flare scenario. The subsequent HXR bursts that occur about 30 min after the primary CME acceleration show a spectral hardening (from 7 to 4) but do not correspond to further CME acceleration and chromospheric evaporation. Therefore, the CME-flare feedback relationship may only be of significance within the first 25 min. of the event under study, as thereafter the flare and the CME eruption evolve independently of each other. [ABSTRACT FROM AUTHOR]

The Solar Influences Data analysis Center (SIDC) is the World Data Center for the production and the distribution of the International Sunspot Index, coordinating a network of about 80 stations worldwide. From this core activity, the SIDC has grown in recent years to a European center for nowcasting and forecasting of solar activity on all timescales. This paper reviews the services (data, forecasts, alerts, software) that the SIDC currently offers to the scientific community. The SIDC operates instruments both on the ground and in space. The USET telescope in Brussels produces daily white light and Hα images. Several members of the SIDC are co-investigators of the EIT instrument onboard SOHO and are involved in the development of the next generation of Europe's solar weather monitoring capabilities. While the SIDC is staffed only during day-time (7 days/week), the monitoring service is a 24 h activity thanks to the implementation of autonomous software for data handling and analysis and the sending of automated alerts. We will give an overview of recently developed techniques for visualization and automated analysis of solar images and detection of events significant for space weather (e.g. CMEs or EIT waves). As part of the involvement of the SIDC in the ESA Pilot Project for Space Weather Applications we have developed services dedicated to the users of the Global Positioning System (GPS). As a Regional Warning Center (RWC) of the International Space Environment Service (ISES), the SIDC produces daily forecasts of flaring probability, geomagnetic activity and 10.7 cm radio flux. The accuracy of these forecasts will be investigated through an in-depth quality analysis.

An important task for the problem of coronal heating is to produce reliable evaluation of the statistical properties of energy release and eruptive events such as micro-and nanoflares in the solar corona. Different types of distributions for the peak flux, peak count rate measurements, pixel intensities, total energy flux or emission measures increases or waiting times have appeared in the literature. This raises the question of a precise evaluation and classification of such distributions. For this purpose, we use the method proposed by K. Pearson at the beginning of the last century, based on the relationship between the first 4 moments of the distribution. Pearson's technique encompasses and classifies a broad range of distributions, including some of those which have appeared in the literature about coronal heating. This technique is successfully applied to simulated data from the model of Krasnoselskikh et al. (2002). It allows to provide successful fits to the empirical distributions of the dissipated energy, and to classify them as a function of model parameters such as dissipation mechanisms and threshold.

Coronal holes (CHs) are the source of high-speed streams (HSSs) in the solar wind, whose interaction with the slow solar wind creates corotating interaction regions (CIRs) in the heliosphere. Whenever the CIRs hit the Earth, they can cause geomagnetic storms. We develop a method to predict the strength of CIR/HSS-driven geomagnetic storms directly from solar observations using the CH areas and associated magnetic field polarity. First, we build a data set comprising the properties of CHs on the Sun, the associated HSSs, CIRs, and orientation of the interplanetary magnetic field (IMF) at L1, and the strength of the associated geomagnetic storms by the geomagnetic indices Dst and Kp. Then, we predict the Dst and Kp indices using a Gaussian process model, which accounts for the annual variation of the orientation of Earth's magnetic field axis. We demonstrate that the polarity of the IMF at L1 associated with CIRs is preserved in around 83 per cent of cases when compared to the polarity of their CH sources. Testing our model over the period 2010–2020, we obtained a correlation coefficient between the predicted and observed Dst index of R = 0.63/0.73, and Kp index of R = 0.65/0.67, for HSSs having a polarity towards/away from the Sun. These findings demonstrate the possibility of predicting CIR/HSS-driven geomagnetic storms directly from solar observations and extending the forecasting lead time up to several days, which is relevant for enhancing space weather predictions. [ABSTRACT FROM AUTHOR]

In this paper we address the prediction of the maximum sunspot number in solar cycle 24. We correlate the integral sunspot activity related to the variability of the cycle decrease speed in the declining phase with the height of the next sunspot maximum. Using this method we predict that the sunspot maximum of cycle 24 will be weaker than the previous one and its peak value will not exceed 72.

Для исследования статистических свойств оценок в условиях ограниченной экспериментальной информации в работе предлагается совмещать обработку экспериментальных данных с процедурой имитационного моделирования, имитирующей продолжение эксперимента в тех же условиях. Предложенная методика используется для повышения эффективности процедуры оценивания показателя степени закона распределения энергии солнечных вспышек.