| 1. |
- Gao, Guangbin, et al.
(author)
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Understanding filamentous cyanobacteria and their adaptive niches in Lake Honghu, a shallow eutrophic lake
- 2025
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In: Journal of Environmental Sciences (China). - 1001-0742. ; 152, s. 219-234
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Journal article (peer-reviewed)abstract
- Freshwater lakes globally are witnessing an escalation in the frequency and intensity of cyanobacterial harmful blooms. However, underlying factors influencing the succession or coexistence of cyanobacteria, especially filamentous ones, remain poorly understood. Lake Honghu, a Ramsar Wetland of International Importance with degrading aquatic ecological quality, served as a case study to elucidate the intricate relationship between environmental changes and cyanobacterial dynamics. Our analysis revealed a significant increase in the dominance of filamentous cyanobacteria, marked by high spatiotemporal variability in community structure. This dominance of filamentous diazotrophic cyanobacteria is attributed to a decrease in the ratio of dissolved inorganic nitrogen to total phosphorus and their capacity to utilize organic phosphorus in phosphorus-deficient conditions. Species-specific density variations were linked to diverse environmental factors, with total nitrogen or total phosphorus concentration remaining as a crucial factor influencing dominant cyanobacterial density fluctuations. The dominance of low-temperature-tolerant Aphanizomenon and Pseudanabaena was evident in spring and winter, whereas Dolichospermum and Cylindrospermopsis, which prefer higher temperatures, thrived in summer and autumn. Additionally, non-algal turbidity and heterogeneity can potentially alter the competitive outcome among filamentous cyanobacteria or foster coexistence under conditions of elevated temperatures and nutrient limitation. This study predicts that filamentous cyanobacteria may spread and persist in lakes spanning a wide trophic range. Current findings enhance our comprehension of the dynamic responses exhibited by filamentous bloom-forming cyanobacteria in the face of environmental changes within shallow eutrophic lakes and provide valuable insights for lake managers involved in the remediation of degraded shallow lakes.
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| 2. |
- Zhang, Jiawei, et al.
(author)
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High-Performance Low-Cost n-Type Se-Doped Mg3Sb2-Based Zintl Compounds for Thermoelectric Application
- 2017
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In: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 29:12, s. 5371-5383
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Journal article (peer-reviewed)abstract
- Thermoelectric materials, capable of converting heat directly into electricity without moving parts, provide a promising solid-state solution for waste heat harvesting. However, currently available commercial thermoelectric materials PbTe and Bi2Te3 are based on tellurium, an extremely scarce and expensive element, which prohibits large scale applications. Herein, we present a systematic study on a new low-cost Te-free material, n-type Se-doped Mg3Sb1.5Bi0.5, by combining the structure and property characterization with electronic structure and electrical transport modeling. Compared with pure Mg3Sb2, Se-doped Mg3Sb1.5Bi0.5 shows the considerably enhanced power factor as well as much lower thermal conductivity. The excellent electrical transport originates from a nontrivial near-edge conduction band with six conducting carrier pockets and a light conductivity effective mass as well as the weak contribution from a secondary conduction band with a valley degeneracy of 2. The accurate location of the conduction band minimum is revealed from the Fermi surface, which appears to be crucial for the understanding of the electronic transport properties. In addition, the total thermal conductivity is found to be reasonably low (∼0.62 W m-1 K-1 at 725 K). As a result, an optimal zT of 1.23 at 725 K is obtained in Mg3.07Sb1.5Bi0.48Se0.02. The high zT, as well as the earth-abundant constituent elements, makes the low-cost Se-doped Mg3Sb1.5Bi0.5 a promising candidate for the intermediate-temperature thermoelectric application. Moreover, the systematic electronic structure and transport modeling provide an insightful guidance for the further optimization of this material and other related Zintl compounds.
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| 3. |
- Zhang, Jiawei, et al.
(author)
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New Insight on Tuning Electrical Transport Properties via Chalcogen Doping in n-type Mg3Sb2-Based Thermoelectric Materials
- 2018
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In: Advanced Energy Materials. - : Wiley. - 1614-6832. ; 8:16
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Journal article (peer-reviewed)abstract
- n-type Mg3Sb1.5Bi0.5 has recently been discovered to be a promising thermoelectric material, yet the effective n-type dopants are mainly limited to the chalcogens. This may be attributed to the limited chemical insight into the effects from different n-type dopants. By comparing the effects of different chalcogen dopants Q (Q = S, Se, and Te) on thermoelectric properties, it is found that the chalcogen dopants Q become more efficient with decreasing electronegativity difference between Q and Mg, which is mainly due to the increasing carrier concentration and mobility. Using density functional theory calculations, it is shown that the improving carrier concentration originates from the increasing doping limit induced by the stabilizing extrinsic defect. Moreover, the increasing electron mobility with decreasing electronegativity difference between Q and Mg is attributed to the smaller effective mass resulting from the enhancing chemical bond covalency, which is supported by the decreasing theoretical density of states. According to the above trends, a simple guiding principle based on electronegativity is proposed to shed new light on n-type doping in Zintl antimonides.
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