| 1. |
- Lukina, I N, et al.
(author)
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Effect of synthesis parameters on the structure and properties of carbon particles formed from amorphous fullerites
- 2020
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Conference paper (peer-reviewed)abstract
- The effect of high-pressure synthesis temperature on the structure and indentation characteristics of the superelastic hard carbon formed from amorphous fullerites and on the tribological properties of the Co-based composite materials (CM) reinforced by the particles of such carbon has been studied by Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), indentation measurements, and tribological tests. It is shown that ball milling (for 48 h) of C60 fullerite crystals results in the amorphization of the product of fullerite transformation upon their high-pressure treatment at temperatures above the stability limit of fullerene molecule (~800°C). An increase in synthesis temperature at 8 GPa from 800°C to 1200°C leads to a gradual graphitization of the structure of amorphous fullerite derived carbon. This decreases its hardness and indentation modulus from 32 to 18 GPa and from 256 to 95 GPa, respectively, and increases the elastic recovery (from 80% to 86%). The best tribological characteristics of the CM are attained at the maximum particle hardness, which is realized in the CM synthesized at 800°C. When the synthesis temperature is elevated to 1200°C, the friction coefficient and wear rate of the CM increase, but they remain substantially lower than those of the matrix cobalt.
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| 2. |
- Voitsekhovskaja, O. V., et al.
(author)
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Photosynthetic activity as assessed via chlorophyll a fluorescence suggests a role of potassium channels in root to shoot signaling
- 2020
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In: Photosynthetica (Praha). - : Institute of Experimental Botany. - 0300-3604 .- 1573-9058. ; 58:2, s. 608-621
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Journal article (peer-reviewed)abstract
- Potassium is indispensable for plant growth. Recently, a role of K+ channels has emerged in sensing and transducing stress and nutrient status. Tetraethylammonium (TEA(+)) is a specific blocker of K+ transport and affects K+ channel gene expression. Two barley varieties with contrasting salinity tolerance, and a chlorophyll b-less mutant, were grown either in the presence of TEA(+) alone or combined with NaCl, at two different concentrations of external K+ and Ca2+, and were analyzed nine days after germination. Chlorophyll a transients monitored via JIP-tests were used to evaluate the state of the photosynthetic machinery. In contrast to reported responses to K+ deficiency, TEA(+) inhibited shoot growth while inducing root growth and increasing photosynthetic performance. Both TEA(+) and NaCl induced the appearance of negative K-bands in OJIP kinetics and an increase in PIABS, indicating a stimulation of photosynthesis by increased sink strength in the context of root to shoot signaling.
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