Dual-defect engineering of catalytic cathode materials for advanced lithium-sulfur batteries
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A semitransparent cathode is proposed for an efficient operation of the relativistic magnetron (RM) with axial extraction. The semitransparent cathode is a kind of shaped cathode. It is achieved using a cylindrical cathode with longitudinal strips removed. The cross section of each removed strip is fan-shaped and all the emit strips are connected in the central area of the cathode. Results of the 3-D particle-in-cell simulations show that the using a semitransparent cathode yields similar performance benefits compared with that using the transparent cathode proposed by the University of New Mexico. Simulation results also show that output characteristics of the RM using the semitransparent cathode are insensitive to the depth and width of each cathode slot. Thus, the semitransparent cathode might be more robust for practical applications.
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Cavity magnetron
Cold cathode
Hot cathode
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The purple sulfur bacterium Allochromatium vinosum can use elemental sulfur as an electron donor for anoxygenic photosynthesis. The elemental sulfur is taken up, transformed into intracellular sulfur globules and oxidized to sulfate. Commercially available 'elemental' sulfur usually consists of the two species cyclo-octasulfur and polymeric sulfur. The authors investigated whether only one sulfur species is used or at least preferred when Alc. vinosum takes up elemental sulfur and forms globules. To this end, Alc. vinosum was cultivated photolithoautotrophically with two types of elemental sulfur that differed in their cyclo-octasulfur : polymeric sulfur ratio, as well as with pure polymeric sulfur. Sulfur speciation was analysed using X-ray absorption spectroscopy, and sulfate contents were determined by HPLC to quantify the amount of elemental sulfur being taken up and oxidized by Alc. vinosum. The results show that Alc. vinosum uses only the polymeric sulfur (sulfur chain) fraction of elemental sulfur and is probably unable to take up and form sulfur globules from cyclo-octasulfur. Furthermore, direct cell–sulfur contact appears to be necessary for uptake of elemental sulfur by Alc. vinosum.
Sulfur Cycle
Anoxygenic photosynthesis
Green sulfur bacteria
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X-ray absorption near edge structure (XANES) spectroscopy at the sulfur K-edge was applied to probe the speciation of sulfur of metabolically different sulfur-accumulating bacteria in situ. Fitting the spectra using a least-square fitting routine XANES reveals at least three different forms of sulfur in bacterial sulfur globules. Cyclooctasulfur dominates in the sulfur globules of Beggiatoa alba and the very recently described giant bacterium Thiomargarita namibiensis. A second type of sulfur globules is present in Acidithiobacillus ferrooxidans: here the sulfur occurs as polythionates. In contrast, in purple and green sulfur bacteria the sulfur mainly consists of sulfur chains, irrespective of whether it is accumulated in globules inside or outside the cells. These results indicate that the speciation of sulfur in the sulfur globules reflects the different ecological and physiological properties of different metabolic groups of bacteria.
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Genetic algorithm
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Oxidizing agent
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With the development of high power magnetron, cathode is researched a lot to endure higher temperature and intense electron bombardment. In order to decrease the central part temperature of cathode in magnetron and extend magnetron's lifetime, a kind of variable pitch helical cathode is proposed in this paper. Computer simulations are adopted to verify whether cathode surface electric field distribution is consistent with its structural uniformity. So electrostatic field uniformity of variable pitch helical cathode is simulated by CST-EM and compared with cylindrical cathode and even pitch helical cathode. The results show that thought variable pitch cathode has the worst structural uniformity, it has similar field uniformity to even pitch cathode, and the uniformity of electric field near the cathode surface of variable pitch cathode is relatively close to that of the cylindrical cathode. So it may be adopted in magnetrons to improve magnetrons' performance and extend their lifetime.
Cavity magnetron
Hot cathode
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Catalyst poisoning
Selective catalytic reduction
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Abstract Titanocenedicarbonyl, Cp2Ti(CO)2, activates the sulfur-sulfur bond in organic disulfides and sulfur homocycles like S6S7 and S8- Cyclic disulfides form chelating ligands with sulfur atoms attached to the Ti atom. The reaction with S6 yields a new compound with an eight sulfur atoms containing ligand. The novel titanocene compounds have been used as precursors for the synthesis of a series of methylene polysulfides.
Methylene
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Abstract Available sulfur was determined in a greenhouse experiment with 30 surface soils from the Southeastern United States by growing cotton plants at six levels of applied sulfate‐sulfur, 0, 2, 4, 8, 16, and 32 ppm. The A value technique involving radiosulfur was used as an index of available sulfur. Sulfur A values varied from 9.8 ppm. to 42 ppm. A high degree of correlation was obtained between A values and the percent sulfur in the control plants. Growth responses from applied sulfate‐sulfur were also related to percent sulfur in the control plants and to A value sulfur in the soil. The total uptake of sulfur also was related closely to the total available sulfur in the soil ( A value plus fertilizer sulfur). A sixteen‐fold increase in the rate of sulfur addition increased the A value by approximately 20%.
Sulfur Cycle
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