Highly Variable Active Galactic Nuclei in the SRG/eROSITA All-Sky Survey: I. Constructing Sample and Catalog of Sources Detected in Low State

We present the results of our search for highly variable active galactic nuclei (AGNs) the X-ray flux from which changed by more than an order of magnitude during the SRG/eROSITA all-sky survey. Using the eROSITA data obtained in the period from December 2019 to February 2022, we have found 1325 sources the X-ray flux from which in the 0.3-2.3 keV energy band changed by more than a factor of 10 at a confidence level of at least 99.73 %. Of them, 635 objects have been classified as AGNs or AGN candidates. We describe the procedure of searching for highly variable sources and the selection of extragalactic objects among them and describe the statistical properties of the produced catalog. We provide a catalog of 49 sources for which a statistically significant flux in their low state was detected. For the latter we provide their light curves and X-ray spectra and discuss in detail the most interesting of them.Comment: 9 figures, 2 table

Application of pile foundations in structurally unstable soils

The active development of the Asia-Pacific region is often accompanied by geotechnical problems that require a rational solution. The article presents the results of a laboratory experiment that simulates the process of slurried pile construction in sandy frozen soils. The authors present the dependence of changes in the temperature of the soil and cement-sand mortar in time, defined the maximum radius of thawing and the total duration of the process of thawing and freezing back to the natural state, given the recommendations for the design of slurried piles taking into account thermal interaction with permafrost soils. The article presents a laboratory study of the interaction of auger cast piles with frozen soil. The results of laboratory studies of the strength of cement mortars of different compositions, hardened at a negative temperature. Recommendations on the choice of the solution composition for the installation of grout-injected piles in frozen soil are given. The article presents the state of the question of designing multi-blade screw piles, reflects the relevance of the development of methods of calculation and updating the regulatory framework. The authors carried out calculations of the bearing capacity of screw piles on various calculation schemes, the results of which are compared with field tests. As a result of comparison recommendations on the choice of the reliable settlement scheme are given. The authors believe that the solution of the problems identified in the article related to the use of advanced types of pile foundations in difficult geotechnical conditions will significantly improve the reliability of structures, reduce construction time and reduce economic costs

Phenological shifts of abiotic events, producers and consumers across a continent

Ongoing climate change can shift organism phenology in ways that vary depending on species, habitats and climate factors studied. To probe for large-scale patterns in associated phenological change, we use 70,709 observations from six decades of systematic monitoring across the former Union of Soviet Socialist Republics. Among 110 phenological events related to plants, birds, insects, amphibians and fungi, we find a mosaic of change, defying simple predictions of earlier springs, later autumns and stronger changes at higher latitudes and elevations. Site mean temperature emerged as a strong predictor of local phenology, but the magnitude and direction of change varied with trophic level and the relative timing of an event. Beyond temperature-associated variation, we uncover high variation among both sites and years, with some sites being characterized by disproportionately long seasons and others by short ones. Our findings emphasize concerns regarding ecosystem integrity and highlight the difficulty of predicting climate change outcomes. The authors use systematic monitoring across the former USSR to investigate phenological changes across taxa. The long-term mean temperature of a site emerged as a strong predictor of phenological change, with further imprints of trophic level, event timing, site, year and biotic interactions.Peer reviewe

Chronicles of nature calendar, a long-term and large-scale multitaxon database on phenology

We present an extensive, large-scale, long-term and multitaxon database on phenological and climatic variation, involving 506,186 observation dates acquired in 471 localities in Russian Federation, Ukraine, Uzbekistan, Belarus and Kyrgyzstan. The data cover the period 1890-2018, with 96% of the data being from 1960 onwards. The database is rich in plants, birds and climatic events, but also includes insects, amphibians, reptiles and fungi. The database includes multiple events per species, such as the onset days of leaf unfolding and leaf fall for plants, and the days for first spring and last autumn occurrences for birds. The data were acquired using standardized methods by permanent staff of national parks and nature reserves (87% of the data) and members of a phenological observation network (13% of the data). The database is valuable for exploring how species respond in their phenology to climate change. Large-scale analyses of spatial variation in phenological response can help to better predict the consequences of species and community responses to climate change.Peer reviewe

Application of pile foundations in structurally unstable soils

The active development of the Asia-Pacific region is often accompanied by geotechnical problems that require a rational solution. The article presents the results of a laboratory experiment that simulates the process of slurried pile construction in sandy frozen soils. The authors present the dependence of changes in the temperature of the soil and cement-sand mortar in time, defined the maximum radius of thawing and the total duration of the process of thawing and freezing back to the natural state, given the recommendations for the design of slurried piles taking into account thermal interaction with permafrost soils. The article presents a laboratory study of the interaction of auger cast piles with frozen soil. The results of laboratory studies of the strength of cement mortars of different compositions, hardened at a negative temperature. Recommendations on the choice of the solution composition for the installation of grout-injected piles in frozen soil are given. The article presents the state of the question of designing multi-blade screw piles, reflects the relevance of the development of methods of calculation and updating the regulatory framework. The authors carried out calculations of the bearing capacity of screw piles on various calculation schemes, the results of which are compared with field tests. As a result of comparison recommendations on the choice of the reliable settlement scheme are given. The authors believe that the solution of the problems identified in the article related to the use of advanced types of pile foundations in difficult geotechnical conditions will significantly improve the reliability of structures, reduce construction time and reduce economic costs

Formation of solitons in a waveguide at second harmonic generation

Second harmonic generation in a quadratic nonlinear waveguide is analyzed analytically and numerically. Formation of spatio-temporal solitons is demonstrated. They can form both positive and negative coefficients of group velocity dispersion due to the waveguide geometry. Analytical results are confirmed by computer simulations

VS-OSCILLOCSOPE ONLIE: WEB-APPLICATION OF PROCESS-BASED VAGANOV-SHASKIN MODEL FOR TREE-RING GROWTH

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала.The efficiency of the process-based Vaganov-Shashkin model for tree-ring growth simulation has been tested previously on extensive dendrochronological material from the Northern Hemisphere in USA, China, Russia, Tunisia, Spain and France. But using the model is not a trivial task, taking into account a number of the model parameters that should be adjusted for the certain environmental conditions based on parameterization approach. Here we present a new web tool of the VS-model parameterization, i.e. VS-Oscilloscope online, which can be used any computer platform due to the universal internet technologies. The software was tested on different datasets, and results of the web simulation were identical to the modeling based on previous version of parameterization – VS-Oscilloscope as a benchmark. It provides researchers an opportunity to use the complex model for visual simulation, reconstruction and forecast realistic tree-ring growth based on daily climatic conditions

Formation of solitons in a waveguide at second harmonic generation

Second harmonic generation in a quadratic nonlinear waveguide is analyzed analytically and numerically. Formation of spatio-temporal solitons is demonstrated. They can form both positive and negative coefficients of group velocity dispersion due to the waveguide geometry. Analytical results are confirmed by computer simulations

Differences in spatial versus temporal reaction norms for spring and autumn phenological events

For species to stay temporally tuned to their environment, they use cues such as the accumulation of degree-days. The relationships between the timing of a phenological event in a population and its environmental cue can be described by a population-level reaction norm. Variation in reaction norms along environmental gradients may either intensify the environmental effects on timing (cogradient variation) or attenuate the effects (countergradient variation). To resolve spatial and seasonal variation in species' response, we use a unique dataset of 91 taxa and 178 phenological events observed across a network of 472 monitoring sites, spread across the nations of the former Soviet Union. We show that compared to local rates of advancement of phenological events with the advancement of temperature-related cues (i.e., variation within site over years), spatial variation in reaction norms tend to accentuate responses in spring (cogradient variation) and attenuate them in autumn (countergradient variation). As a result, among-population variation in the timing of events is greater in spring and less in autumn than if all populations followed the same reaction norm regardless of location. Despite such signs of local adaptation, overall phenotypic plasticity was not sufficient for phenological events to keep exact pace with their cues-the earlier the year, the more did the timing of the phenological event lag behind the timing of the cue. Overall, these patterns suggest that differences in the spatial versus temporal reaction norms will affect species' response to climate change in opposite ways in spring and autumn

PRISM (Polarized Radiation Imaging and Spectroscopy Mission): an extended white paper

Contains fulltext : 126057.pdf (preprint version ) (Open Access