托木斯克国立大学

Constantly reducing the size and improving the performance of electronics lead to the heat generation enhancement and unstable operation of such devices. Therefore, the modeling and production of the efficient cooling systems is one of the most important modern challenges. Based on this, in the present research a numerical study on the heat-conducting base material influence on the power-law nanofluid thermal convection within a cavity having a local source of constant volumetric heat generation is performed. The problem is described by transient differential equations written using the Oberbeck–Boussinesq approximation, the Ostwald-de Waele power law and the single-phase nanoliquid approaches. The nanosuspension characteristics are calculated employing the experimental relations reflecting the impact of the nanoparticles concentration and liquid temperature. The equations are solved using the developed in-house numerical algorithms based on the finite difference technique. The locally one-dimensional difference scheme has been used to reduce 2D problem to a set of 1D problems. Convective terms have been approximated by the second upstream scheme, the diffusion terms are approximated by the central differences, while the transient terms are discretized by the Euler scheme. The obtained sets of algebraic equations have been solved using effective direct and iterative methods. The work analyzes the impact of the power-law index, the material of the thermally conductive substrate, the material of nanoparticles and their concentration on heat transfer performance and the cooling technique efficiency. Numerical simulations show that the simultaneous usage of a thermally conductive copper substrate and copper nanoparticles makes it possible to diminish the mean temperature of the heated element. Moreover, a growth of the nanoparticles volume fraction allows to decrease the heater average temperature. The obtained results can be used for improvement of the electronics cooling systems, modern heat exchangers and thermal energy storage systems where the combination of non-Newtonian nanofluid as a working fluid and heat-conducting substrates can be considered as an effective approach for the optimization of the heat transfer.

Peatlands store large carbon reservoirs, but the landscape controls on their lateral carbon losses remain insufficiently resolved. We investigated dissolved organic carbon (DOC) concentrations and export along a bog–swamp forest–Klyuch River continuum within the Great Vasyugan Mire, Western Siberia. Peat-profile characterization, pore-water chemistry and hydrometeorological monitoring were combined to assess spatial and seasonal DOC patterns. Swamp-forest waters at the thicker-peat site contained more DOC than waters from the open sedge–Sphagnum bog and the shallow-peat forest. The contrast between the two forested sites indicates that forest cover alone is insufficient to explain DOC enrichment. Pore-water DOC varied with peat decomposition and water-table conditions, while bulk peat TOC was a weaker predictor. Riverine DOC concentrations were higher in the forest-draining tributaries than in the main channel. Concentration and export maxima were seasonally separated: DOC concentrations were highest during the warm season, whereas the largest export occurred during spring high flow. These findings identify hydrologically connected swamp-forest margins as important DOC-rich source areas within the studied catchment. They also show why peatland carbon assessments should distinguish carbon availability in pore waters from the hydrological timing of export. Warming, changing precipitation and vegetation shifts may alter these source–transport linkages, but the direction and magnitude of future lateral carbon loss will depend on runoff and retention as well as DOC production.

Early Devonian magmatism in the Minusinsk trough of the Altai-Sayan Large Igneous province provides a critical record of regional geologic history. In this study, we determined the U-Pb baddeleyite isotope age, major and trace element geochemistry, and Sr-Nd isotope composition of igneous rocks in the Uryup sector of Minusinsk trough, with the aim of constraining their magmatic origin. The volcanic succession is divided, from base to top, into three Suites: (1) the Bazyr Suite, composed of basalts, trachybasalts, basaltic trachyandesites, transitional tephrites-trachybasalts, and phonotephrites; (2) the Beresh Suite, consisting of trachybasalts, basaltic trachyandesites, phonotephrites, tephriphonolites, and feldspathoid ijolites; and (3) the Ashpan Suite, comprising basalts, trachybasalts, and basaltic trachyandesites. The Early Devonian age of these Suites, established in previous geological and palaeontological studies, is confirmed here by new U-Pb geochronological data on baddeleyite obtained by ID-TIMS. Rare-element concentrations in all mafic rocks, regardless of alkalinity, vary widely, showing features typical of both oceanic island basalts and island arc basalts. Compared with sub-alkalic counterparts, alkalic mafic rocks contain abundant nepheline phenocrysts (up to 30 wt.%) and are enriched in Na2O, Al2O3, Rb, Ba, Th, U, K, Nb, REE, and radiogenic Sr, while exhibiting similar and only slightly variable radiogenic Nd values. We propose a model in which all Uryup sector rocks were derived from a single sub-alkalic basaltic parental melt generated in the asthenospheric mantle by the influence of a mantle plume on fragments of ancient supra-subduction lithospheric mantle. Geochemical and isotopic variations are inconsistent with a simple comagmatic relationship between sub-alkalic and alkalic rocks or with fractional crystallization as the sole controlling process. Bazyr sub-alkalic basaltic magmas experienced simultaneous fractional crystallization and contamination by silicate crust. Beresh phonotephrites, tephriphonolites, and feldspathoid ijolites formed from differentiated sub-alkalic melts through carbonate contamination, possibly within the continental crust.

This article provides the first comprehensive description and assessment of environmental changes in a unique natural transboundary region-South-Eastern Altai, which is located in the arid territories of Russia and Mongolia. This region of Asia is rightfully included in the high-mountain Third Pole (Roof of the World). In three key areas, Tsambagarav Massif (Mongolia), Mongun-Taiga Massif, and North-Chuya Ridge (Russia), the following are considered: (1) the latest dynamics of glaciers from the early 1960s (beginning of regular instrumental observations) to the present day; (2) climate change and land use systems; and (3) the characteristics of the biota and the causes of its dynamics. The article concludes with a consideration of (4) population adaptation models.

Samples of hydroxyapatite modified with strontium ions were synthesized. The amount of doped ions during the synthesis varied from 0.1 to 0.5 mol. The phases were identified and their crystallographic parameters were determined using X-ray phase and X-ray structural analysis. It was found that there is an isomorphic substitution of calcium ions by strontium ions in the samples of strontium- modified hydroxyapatite. The surface of the samples was studied using scanning electron microscopy and X-ray spectral microanalysis and an assessment was made of the quantitative distribution of chemical elements on the surface: strontium is uniformly distributed over the surface of the synthesized samples. An assessment of the antibacterial properties in relation to Escherichia coli and Staphylococcus aureus bacteria was carried out. All samples have bactericidal properties.