The work is aimed to study the processes of nonradiative energy transfer from Yb3+ ions to Tm3+ ions, as well as the processes of interaction between Tm3+ ions in Y2O3:Yb, Tm (CYb = 6, 10, 15 at. %, ...CTm = 1 at. %), Y2O3: Yb, Tm (СYb = 6, 10, 15 at. %, CTm = 3 at. %) ceramics.
The luminescence spectra due to the 1G4→3H6, 1G4→3F4, 3F3→3H6, 3H4→3H6 transitions of the Tm3+ ions, as well as the luminescence decay curves from the 2F5/2 level of Yb3+ and 1G4, 3F3, 3H4, 3F4 levels of the Tm3+ ions recorded upon excitation of the level of the Yb3+ ions, were analyzed for concentration series Y2O3: Yb, Tm (CYb = 6, 10, 15 at. %, CTm = 1 at. %), Y2O3:Yb, Tm (СYb = 6, 10, 15 at. %, CTm = 3 at. %. %) ceramics. On the basis of this, the mechanisms of population and unloading of the corresponding levels of Tm3+ ions were proposed.
•Nonradiative energy transfer between Yb3+ and Tm3+ in Y2O3:Yb, Tm ceramics was studied.•Mechanisms of population and unloading of levels of Yb3+ and Tm3+ ions are proposed.•Y2O3:Yb, Tm is a potentially active medium for solid-state lasers.•Lasing can be obtained at 3F4.→3H6 transition of Tm3+ by pumping Yb3+ to 2F5/2 level
This paper presents estimates of forest mortality from fires that occurred in the northern territories in the 21st century, based on the analysis of fire burning intensity obtained from MODIS ...instruments installed on satellites
Terra
and
Aqua
. A brief analysis of fire distribution and forest mortality resulting therefrom is also presented in the paper both by year and by different territories (countries). The analysis shows that from 2002 to 2021, 70 659 fires were registered in Zone 60 (the area north of 60° N) and 5997 fires were registered in Zone AC (the area north of the Arctic Circle). Moreover, 33 892 fires in Zone 60 were registered from 2002 to 2011 and 36 767 fires from 2012 to 2021; 2395 fires were registered in Zone AC from 2001 to 2011 and 3602 fires from 2012 to 2021. Between 2002 and 2021, 102 million ha of forest land were covered by fires in Zone 60 and 8 million ha in Zone AC. At the same time, more than 22 million ha of forests died in Zone 60 (they received the fifth grade of the average weighted category state in the final fire year), and over 2 million ha died in Zone AC. Over 2002–2011, 7 015 000 ha of forests died in Zone 60 (1.2 % of all forest vegetation in the zone; an average of 19.6% of the area affected by fire) and 15 372 000 ha of forests over 2012–2021 (2.6 and 23.3%, respectively); over 2002–2011, 641 thousand ha of forests died in Zone AC (2.8 and 23.7%, respectively) and 1 379 000 ha of forests over 2012–2021 (1.9 and 26.5%, respectively). The paper also presents information on forest death by territories (countries) in the analyzed zones. The presented data made it possible to draw the following preliminary conclusions: over recent decades, there have been no significant changes in the number of fires in Zone 60. Nevertheless, it is worth noting that, in 2019–2020, the number of fires in Zone AC increased drastically in Russia; in the second decade of the analyzed period, an increase in forest death from fires in the analyzed zones in Russia was observed; over the study period, no trends were observed in the ratio of the area of dead forests and total forest area in the analyzed countries; the average percentage of dead forests for the entire study period is comparable in Russia, the United States, and Canada, though it is significantly lower in Northern European countries; the same picture is observed in the ratio of dead forest area and fire affected area.
The effect of biochar on the properties of a loamy sand Spodosol with different fertility level in the ploughed horizon has been studied in a 60-day laboratory experiment. It has been found that the ...application of biochar resulted in a significant increase of the soil water content in the range of soil-water potential from −5 to −50 kPa, a significant decrease of the total shrinkage of the soil with high level of fertility after three wetting-drying cycles, and the accumulation of a significantly higher content of nitrates in the soil. At a water content of 21%, less favorable conditions for the denitrification development were formed in the soil with high level of fertility than in the medium-fertile soil, which resulted in lower cumulative N₂O emission from the former. The addition of biochar resulted in no significant changes in the cumulative emission of CO₂from the studied soil but significantly reduced the emission of N₂O from the soil at the simultaneous addition of biochar and clover residues.
The local control of arterial diameter by blood flow rate has been attributed to the ability of the endothelial cells to sense the shear stress exerted on them by flowing blood. Since shear stress is ...proportional to the product of flow rate and fluid viscosity, an increase in the latter will augment shear stress and lead to arterial dilatation as well. We therefore designed experiments to reveal the control of the arterial lumen by blood viscosity and to compare it with the control by blood flow rate. Changes in external diameter of a segment of feline femoral artery caused by variations in blood viscosity and/or flow rate were recorded during the perfusion in situ under stabilised transmural pressure. Decrease in blood viscosity evoked by haemodilution at a constant flow rate led to arterial constriction whereas an increase in viscosity due to haemoconcentration caused arterial dilatation. These viscosity induced changes in arterial diameter depended on intact endothelium. Responses to the changes in blood viscosity and flow rate of the same magnitude were practically identical. These results show that blood viscosity is a factor affecting vascular smooth muscle tone and confirm the suggestion that shear stress is the key signal in the endothelium dependent control of the arterial lumen by blood flow rate.
A model of tunneling multiresonant electronic transitions in nanocontacts containing ultrasmall nanoparticles with adsorbed atoms has been developed. Mechanisms of the formation of series of ...equidistant negative differential resistances in tunneling spectra of these structures have been analyzed. The possibility of the coexistence of equidistant series of two types, Coulomb and vibrational, has been shown. The signatures for identification of these series have been formulated. Tunneling spectra of ultrasmall metal nanoparticles containing information on their electron vibrational subsystems have been interpreted.
Laboratory experiments were carried out to test the electroslag remelting of corrosion-resistant titaniumalloyed steel using AKF235 low-silicon flux. The titanium loss in these experiments was ...compared with the available literature data on titanium loss in similar steels during electroslag remelting using ANF-29 high-silicon flux. It is shown that the use of AKF235 flux reduces the titanium loss if all the other conditions (content of titanium dioxide in slag and slag deoxidation conditions) are equal. If the content of titanium dioxide in the starting flux is 2.5%, the titanium loss is practically suppressed by a sufficient amount of deoxidizers added to the slag: 6 g Al and 1.5 g Ti per 1 kg of melted metal. Reducing the weights of added deoxidants to 3 g Al and 0.5 g Ti per 1 kg of melted metal, as well as reducing the content of titanium dioxide in the slag increase the titanium loss.
Abstract
Very often, when designing and developing radio electronic devices, engineers are regularly faced with the need to solve various kinds of problems to ensure the operation of a product under ...the required mechanical loads or thermal conditions during operation. One of the main issues that arise when conducting thermal modeling of radio electronics is the correct assessment of the results. There are a number of electronic components that need to be cooled, mainly through a printed circuit board: power supply transistors, power diodes, microcircuits, etc. For such elements, 90% (or more) of the heat flux from the component is diverted through the printed circuit board, and then to the radiator. Therefore, when carrying out the simulation, it is necessary to have previously obtained reliable temperature results on the power elements. The use of a detailed 3D model for modeling is most often unjustified and can introduce certain errors in the calculations. This article compares different 3D transistor models and the effect of detailing on the modeling process in CAD SolidWorks.
αβT-cell-depleted allogeneic hematopoietic cell transplantation holds promise for the safe and accessible therapy of both malignant and non-malignant blood disorders. Here we employed molecular ...barcoding normalized T-cell receptor (TCR) profiling to quantitatively track T-cell immune reconstitution after TCRαβ-/CD19-depleted transplantation in children. We demonstrate that seemingly early reconstitution of αβT-cell counts 2 months after transplantation is based on only several hundred rapidly expanded clones originating from non-depleted graft cells. In further months, frequency of these hyperexpanded clones declines, and after 1 year the observed T-cell counts and TCRβ diversity are mostly provided by the newly produced T cells. We also demonstrate that high TCRβ diversity at day 60 observed for some of the patients is determined by recipient T cells and intrathymic progenitors that survived conditioning regimen. Our results indicate that further efforts on optimization of TCRαβ-/CD19-depleted transplantation protocols should be directed toward providing more efficient T-cell defense in the first months after transplantation.
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