THE RUDERAL VEGETATION OF CENTRAL YAKUTIA (THE ECOLOGO-PHYTOCENOTIC ANALYSIS)

The purpose of the work: the analysis of the spatial-temporal and ecological laws of the ruderal vegetation in Central Yakutia. The basic anthropogenous places of inhabitation have been typified. The syntaxonomy of the ruderal vegetation of Central Yakutia has been built, in which 5 unions, 16 assiciations, 19 subassociations are new. The connections of the syntaxons of the ruderal vegetation with natural and anthropogenous factors have been revealed. The regioning of the ruderal vegetation has been performed on the base sigma-syntaxonomy. The performed investigation has allowed to develop the design of optimization of the ruderal vegetation of the Central Yakutia, accepted for use by the State Committee of Building of Sacha Republic (Yakutia)Available from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio

Vegetation cover analysis of the mountainous part of north-eastern Siberia by means of geoinformation modelling and machine learning (basic principles, approaches, technology and relation to geosystem science)

For the first time, the geoinformation modelling and machine learning approaches have been used to study the vegetation cover of the mountainous part of North-Eastern Siberia – the Orulgan medium-altitude mountain landscape province. These technologies allowed us to distinguish a number of mapping units that were used for creation and analysis of 1:100 000 scale vegetation map of the interpreted key area. Based on the studies, we decided upon the basic principles, approaches and technologies that would serve as a methodology basis for the further studies of vegetation cover of the large region. Relief, slope aspect, genetic types of sediments, and moisture conditions were selected as supplementary factors to the vegetative indices for differentiation of both plant communities and vegetation map units

: Application of Geoinformation Modeling Methods to Study the Spatial Structure of Vegetation Cover in the Orulgan Middle-Mountain Landscape Province (Northeastern Yakutia)

International audienceИзучена пространственная структура растительного покрова одной из высокогорных ландшафтных провинций Северо-Восточной Якутии. С помощью методов анализа данных дистанционного зондирования Земли и геоинформационного моделирования, включающих также и методы машинного обучения, было выделено 9 геоботанических картируемых подразделений, которые позволили построить и проанализировать геоботаническую карту масштаба 1:100 000

Анализ ландшафтной структуры восточного склона хребта Орулган

International audienceThe aim of the research is to analyze the landscape structure of the eastern slope of the Orulgan ridge using complex geoinformation modelling. We use the field surveys data made in 2018-2019. The geoinformation modelling technique consists of the supervised pixel-based classification of time series remote sensing data of Landsat 8 OLI/ TIRS and Sentinel 2 MSI and TPI-based landform classification using ASTER GDEM scenes. As a result of a combination of the obtained physiognomic criteria, relief and vegetation, the types of terrain and landscape units of the study area were identified. The Random Forest classifier was the most efficient in identifying 8 association groups with an overall accuracy of 79.7% by the confusion matrix. With an overlay of terrain types and vegetation associations, we allow the creation of the permafrost-landscape map. In total, 22 landscape units were identified within the study area. The use of geoinformation modeling made it possible to obtain a detailed landscape structure of study area and assess the main properties of the landscape spatial organization of the eastern slope of the Orulgan ridge. The mountainous area characterized by strong dissection, causes a well-defined vertical zonation. In general, the most common altitudinal permafrost landscapes is mountain woodlands (57% of the territory) and mountain tundra occupies 16%. Intrazonal mountain and boreal landscapes occupy 15%. The leading role in the landscape diversity of the eastern slope of the Orulgan Range is played by a combination of various geological structures that determine the types of erosion-tectonic (mountain-slope and rocky mountain tops), glacial-accumulative (moraine, outwash and glacial-valley) and erosion-accumulative terrain. (medium-altitude terrace and low-terrace) origin

Nd³⁺, Yb³⁺:YF₃ Optical Temperature Nanosensors Operating in the Biological Windows

This work is devoted to the study of thermometric performances of Nd3+ (0.1 or 0.5 mol.%), Yb3+ (X%):YF3 nanoparticles. Temperature sensitivity of spectral shape is related to the phonon-assisted nature of energy transfer (PAET) between Nd3+ and Yb3+). However, in the case of single-doped Nd3+ (0.1 or 0.5 mol.%):YF3 nanoparticles, luminescence decay time (LDT) of 4F3/2 level of Nd3+ in Nd3+ (0.5 mol.%):YF3 decreases with the temperature decrease. In turn, luminescence decay time in Nd3+ (0.1 mol.%):YF3 sample remains constant. It was proposed, that at 0.5 mol.% the cross-relaxation (CR) between Nd3+ ions takes place in contradistinction from 0.1 mol.% Nd3+ concentration. The decrease of LDT with temperature is explained by the decrease of distances between Nd3+ with temperature that leads to the increase of cross-relaxation efficiency. It was suggested, that the presence of both CR and PAET processes in the studied system (Nd3+ (0.5 mol.%), Yb3+ (X%):YF3) nanoparticles provides higher temperature sensitivity compared to the systems having one process (Nd3+ (0.1 mol.%), Yb3+ (X%):YF3). The experimental results confirmed this suggestion. The maximum relative temperature sensitivity was 0.9%·K−1 at 80 K

Distribution and Structure Analysis of Mountain Permafrost Landscape in Orulgan Ridge (Northeast Siberia) Using Google Earth Engine

International audienceAn analysis of the landscape spatial structure and diversity in the mountain ranges of Northeast Siberia is essential to assess how tundra and boreal landscapes may respond to climate change and anthropogenic impacts in the vast mountainous permafrost of the Arctic regions. In addition, a precise landscape map is required for knowledge-based territorial planning and management. In this article, we aimed to explore and enhanced methods to analyse and map the permafrost landscape in Orulgan Ridge. The Google Earth Engine cloud platform was used to generate vegetation cover maps based on multi-fusion classification of Sentinel 2 MSI and Landsat 8 OLI time series data. Phenological features based on the monthly median values of time series Normalized Difference Vegetation Index (NDVI), Green Normalized Difference Vegetation Index (GNDVI), and Normalized Difference Moisture Index (NDMI) were used to recognize geobotanical units according to the hierarchical concept of permafrost landscapes by the Support Vector Machine (SVM) classifier. In addition, geomorphological variables of megarelief (mountains and river valleys) were identified using the GIS-based terrain analysis and landform classification of the ASTER GDEM scenes mosaic. The resulting environmental variables made it possible to categorize nine classes of mountain permafrost landscapes. The result obtained was compared with previous permafrost landscape maps, which revealed a significant difference in distribution and spatial structure of intrazonal valleys and mountain tundra landscapes. Analysis of the landscape structure revealed a significant distribution of classes of mountain Larix-sparse forests and tundra. Landscape diversity was described by six longitudinal and latitudinal landscape hypsometric profiles. River valleys allow boreal–taiga landscapes to move up to high-mountainous regions. The features of the landscape structure and diversity of the ridge are noted, which, along with the specific spatial organization of vegetation and relief, can be of key importance for environmental monitoring and the study of regional variability of climatic changes

Synthesis and Single Crystal Growth by Floating Zone Technique of FeCr2O4 Multiferroic Spinel: Its Structure, Composition, and Magnetic Properties

We present the new synthesis root of spinel-structure FeCr2O4 and its single crystal growth by the optical floating zone method, ensuring its single phase and near-ideal composition. The advantage of the proposed synthesis method is the creation of the reducing atmosphere in the oven needed for preserving the Fe2+ oxidation state via decomposition of the iron (II) oxalate FeC2O4 used as one of the initial components. The occurrence of the Fe3+ ions in the obtained polycrystalline samples as well as grown single crystals was carefully monitored by means of Mössbauer spectroscopy. Magnetic susceptibility and heat capacity temperature dependences reveal a sequence of the structural (138 K) and magnetic (at 65 K and 38 K) phase transition characteristics for the FeCr2O4 compound

An Effect of Fe³⁺ Ion Substitution for Cr³⁺ in the Octahedral Sites of FeCr₂O₄ Multiferroic Spinel: Mössbauer Spectroscopy Study

We present the results of a successful synthesis and investigation of polycrystalline Fe2+(Cr3+, Fe3+)2O4 powder, where 1/8 part of the Cr3+ ions in the octahedral sites is substituted by the Fe3+ ones. It is shown that under such doping, the material retains the cubic spinel structure characteristic of the parent FeCr2O4 compound. However, the values of the critical temperatures have changed. Both the orbital and magnetic orderings occur at about 120 K, and magnetic structure rearrangement associated with an onset of spiral modulation takes place at 26 K. Mössbauer studies in a wide temperature range make it possible to accurately control the content of iron ions, their valence and magnetic states, and local environment, therefore, allowing a deeper understanding of the features of the revealed transformations

Li₃V₂(PO₄)₃ Cathode Material: Synthesis Method, High Lithium Diffusion Coefficient and Magnetic Inhomogeneity

Li3V2(PO4)3 cathodes for Li-ion batteries (LIBs) were synthesized using a hydrothermal method with the subsequent annealing in an argon atmosphere to achieve optimal properties. The X-ray diffraction analysis confirmed the material’s single-phase nature, while the scanning electron microscopy revealed a granular structure, indicating a uniform particle size distribution, beneficial for electrochemical performance. Magnetometry and electron spin resonance studies were conducted to investigate the magnetic properties, confirming the presence of the relatively low concentration and highly uniform distribution of tetravalent vanadium ions (V4+), which indicated low lithium deficiency values in the original structure and a high degree of magnetic homogeneity in the sample, an essential factor for consistent electrochemical behavior. For this pure phase Li3V2(PO4)3 sample, devoid of any impurities such as carbon or salts, extensive electrochemical property testing was performed. These tests resulted in the experimental discovery of a remarkably high lithium diffusion coefficient D = 1.07 × 10−10 cm2/s, indicating excellent ionic conductivity, and demonstrated impressive stability of the material with sustained performance over 1000 charge–discharge cycles. Additionally, relithiated Li3V2(PO4)3 (after multiple electrochemical cycling) samples were investigated using scanning electron microscopy, magnetometry and electron spin resonance methods to determine the extent of degradation. The combination of high lithium diffusion coefficients, a low degradation rate and remarkable cycling stability positions this Li3V2(PO4)3 material as a promising candidate for advanced energy storage applications

Interrelation between the Solid-State Synthesis Conditions and Magnetic Properties of the NiCr₂O₄ Spinel

The synthesis of the NiCr2O4 compound with the spinel structure via the high-temperature solid-state reaction leads to different deviations of the cationic composition from the nominal depending on the atmosphere in the furnace chamber. The samples prepared from the same starting NiO and Cr2O3 compounds but in different atmospheres differ in phase composition and orbital and spin ordering temperatures. We find that a common route of synthesis in the air and a possible presence of the Ni2O3 in initial NiO lead to the incorporation of the Ni3+ ions into the octahedral sites regularly occupied by the Cr3+ ions. This results in a decrease in the orbital ordering and an increase in the Nèel temperatures. We propose that the Nèel temperature value serves as a measure of a departure of a composition from the nominal NiCr2O4. The lowest Nèel temperature among our series was TN = 63 K which we consider the closest to the intrinsic quantity of the NiCr2O4 compound