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It is well-known that the presence of serial correlation may result in an inefficient or even biased estimation in time series analysis. In this paper, we consider testing serial correlation in a general d-factor model when the model errors follow the GARCH process, which is frequently used in modeling financial data. Two empirical likelihood-based testing statistics are suggested as a way to deal with problems that might come up with infinite variance. Both statistics are shown to be chi-squared distributed asymptotically under mild conditions. Simulations confirm the excellent finite-sample performance of both tests. Finally, to emphasize the importance of using our tests, we explore the impact of the exchange rate on the stock return using both monthly and daily data from eight countries. [ABSTRACT FROM AUTHOR]

Background: The increasingly severe salinization of the aquatic environment has led to serious damage to the habitats of aquatic organisms. Benthic diatoms are commonly employed as indicator species for assessing water quality and serve as a reflection of the overall health of the aquatic ecosystem. Nitzschia palea is a common diatom found in freshwater, with high oil content, rapid reproductive rate, and it is a commonly dominant species in various rivers. Results: The results showed that after 4 days (d) of saline-alkali stress, the cell density and chlorophyll a content of Nitzschia palea reached their maximum values. Therefore, we selected Nitzschia palea under 4 d stress for Tandem Mass Tag (TMT) quantitative proteomic analysis to explore the molecular adaptation mechanism of freshwater diatoms under saline-alkali stress. Totally, 854 proteins were enriched, of which 439 differentially expressed proteins were identified. Gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and subcellular fractionation analysis revealed that these proteins were mainly enriched in the photosynthesis pathway, citric acid cycle (TCA cycle), fatty acid synthesis, and glutathione cycle. Conclusions: This study aims to reveal the physiological, biochemical and proteomic mechanisms of salt and alkali tolerance and molecular adaptation of Nitzschia palea under different saline-alkali concentrations. This study showed that Nitzschia palea is one candidate of the environmental friendly, renewable bioenergy microalgae. Meantime, Nitzschiapalea reveals for the proteome of the freshwater and provides the basis, it became a model algal species for freshwater diatoms. [ABSTRACT FROM AUTHOR]

Highlights: The flower-like δ-MnO2 nanostructures with controlled oxygen vacancies as an extraordinary ZIBs cathode are innovatively developed. The cathode can present large capacity and high-rate zinc-ion storage. DFT analysis substantially unveils the effects of various vacancy concentrations on their electrochemical performances. In recent years, manganese-based oxides as an advanced class of cathode materials for zinc-ion batteries (ZIBs) have attracted a great deal of attentions from numerous researchers. However, their slow reaction kinetics, limited active sites and poor electrical conductivity inevitably give rise to the severe performance degradation. To solve these problems, herein, we introduce abundant oxygen vacancies into the flower-like δ-MnO2 nanostructure and effectively modulate the vacancy defects to reach the optimal level (δ-MnO2−x−2.0). The smart design intrinsically tunes the electronic structure, guarantees ion chemisorption–desorption equilibrium and increases the electroactive sites, which not only effectively accelerates charge transfer rate during reaction processes, but also endows more redox reactions, as verified by first-principle calculations. These merits can help the fabricated δ-MnO2−x−2.0 cathode to present a large specific capacity of 551.8 mAh g−1 at 0.5 A g−1, high-rate capability of 262.2 mAh g−1 at 10 A g−1 and an excellent cycle lifespan (83% of capacity retention after 1500 cycles), which is far superior to those of the other metal compound cathodes. In addition, the charge/discharge mechanism of the δ-MnO2−x−2.0 cathode has also been elaborated through ex situ techniques. This work opens up a new pathway for constructing the next-generation high-performance ZIBs cathode materials. [ABSTRACT FROM AUTHOR]