Perovskite solid solution ceramics of (1 − x)BaTiO3–xBi(Mg2/3Nb1/3)O3 (BT–BMN) (x = 0.05–0.2) were synthesized by solid‐state reaction technique. The results show that the BMN addition could lower ...the sintering temperature of BT‐based ceramics. X‐ray diffraction results reveal a pure perovskite structure for all studied samples. Dielectric measurements exhibit a relaxor‐like characteristic for the BT–BMN ceramics, where broadened phase transition peaks change to a temperature‐stable permittivity plateau (from −50°C to 300°C) with increasing the BMN content (x = 0.2), and slim polarization–electric field hysteresis loops were observed in samples with x ≥ 0.1. The dielectric breakdown strength and electrical resistivity of BT–BMN ceramics show their maxima of 287.7 kV/cm and 1.53 × 1013 Ω cm at x = 0.15, and an energy density of about 1.13 J/cm3 is achieved in the sample of x = 0.1.
Potassium‐ion batteries (PIBs) are recognized as promising alternatives for lithium‐ion batteries as the next‐generation energy storage systems. However, the larger radius of K+ hinders the K+ ...insertion into the conventional carbon electrode and results in sluggish potassiation kinetics and poor cycling stability. Here, nitrogen and fluorine dual doping of soft carbon nanotubes (NFSC) anode are synthesized in one pot, achieving extraordinary electrochemical performance for PIBs. It is demonstrated that NFSC with a doping dose of 5.6 at% nitrogen and 1.3 at% fluorine together exhibits the highest reversible capacity of 238 mAh g−1 at 0.2 A g−1 and cycling stability of 186 mAh g−1 after 1000 cycles at 1 A g−1. The extraordinary electrochemical performance can be attributed to the hollow structure, expanded interlayer distance, nitrogen and fluorine dual doping, and the binding ability of abundant defect sites. Moreover, density functional theory shows that the extra fluorine modification can dramatically enhance the conventional nitrogen doping effect and reduces the formation energy which makes a great contribution to the improvement of electrical conduction and K‐ions insert. This work may promote the development of low‐cost and sustainable carbon‐based materials for PIBs and other advanced energy storage devices.
The nitrogen and fluorine dual‐doped soft carbon fiber serves as the advanced anode for potassium ion battery. The dual‐doping effect is realized by locking the fluorine and nitrogen sources in the polypyrrole fiber cage which boosts the high conductivity, outstanding rate performance, and cycling stability.
•In this large-scale longitudinal epidemiologic assessment of a cohort of college students in China, the prevalence of acute stress symptoms decreased, while the rates of depressive and anxiety ...symptoms increased over the course of the epidemic.•Around 10% of students had persistent and/or developed new mental health problems. Multiple factors, including senior students, COVID-19 exposure, COVID-19-related worries, social support, and family function were significant predictors of distinct mental health trajectories.•Mental health concerns significantly increased over the course of the epidemic, clinicians and academic administrations alike should pay close attention to college students’ expressed needs and associated risk factors for trajectories of psychopathology.
Growing evidence supports a clear association between COVID-19 pandemic and mental health. However, little is known about the longitudinal course of psychopathology in young adults at different stages of the pandemic.
This large-scale, longitudinal, population-based survey was conducted among college students in China. The rates of three mental health problems (acute stress, anxiety, and depressive symptoms), and their change patterns at two phases of the pandemic (early vs under-control) were measured. Predictors of changes in mental health symptoms were examined utilizing multivariate regression.
Among the 164,101 college students who participated in the first wave survey (T1=during onset of outbreak), 68,685 (41.9%) completed a follow-up survey (T2=during remission). In the follow-up survey, the prevalence of probable acute stress (T1: 34.6%; T2: 16.4%) decreased, while the rates of depressive (T1: 21.6%; T2: 26.3%) and anxiety symptoms (T1: 11.4%; T2: 14.7%) increased. Senior students, with suspected or conformed cases in their community and COVID-19 related worries (all AORs > 1.20, ps < 0.001) were found to have a higher risk of developing mental health problems in at least one wave. Less physical exercise, low perceived social support, and a dysfunctional family were found to negatively impact psychological symptoms.
Acute stress, anxiety, and depressive symptoms have been prevalent among college students during the COVID-19 epidemic, and showed a significant increase after the initial stage of the outbreak. Some college students, especially those with the risk factors noted above, exhibited persistent or delayed symptoms.
A heterojunction device which has good transport characteristics and low sensitivity is obtained through two kinds of organic molecules inert to NO2. Using the heterojunction device, constructing ...more‐sensitive double‐heterojunction devices can obtain better room‐temperature detection characteristics.
Particle swarm optimization (PSO) has been employed to solve numerous real-world problems because of its strong optimization ability and easy implementation. However, PSO still has some shortcomings ...in solving complicated optimization problems, such as premature convergence and poor balance between global exploration and local exploitation. A novel hybrid particle swarm optimization using adaptive strategy (ASPSO) is developed to address associated difficulties. The contribution of ASPSO is threefold: (1) a chaotic map and an adaptive position updating strategy to balance exploration behavior and exploitation nature in the search progress; (2) elite and dimensional learning strategies to enhance the diversity of the population effectively; (3) a competitive substitution mechanism to improve the accuracy of solutions. Based on various functions from CEC 2017, the numerical experiment results demonstrate that ASPSO is significantly better than the other 16 optimization algorithms. Furthermore, we apply ASPSO to a typical industrial problem, the optimization of melt spinning progress, where the results indicate that ASPSO performs better than other algorithms.
A series of (1-x)Bi
La
Na
Li
Ti
Zr
O
-xNa
Bi
NbO
((1-x)LLBNTZ-xNBN) (x = 0-0.14) ceramics were designed and fabricated using the conventional solid-state sintering method. The phase structure, ...microstructure, dielectric, ferroelectric and energy storage properties of the ceramics were systematically investigated. The results indicate that the addition of Na
Bi
NbO
(NBN) could decrease the remnant polarization (P
) and improve the temperature stability of dielectric constant obviously. The working temperature range satisfying TCC
≤±15% of this work spans over 400 °C with the compositions of x ≥ 0.06. The maximum energy storage density can be obtained for the sample with x = 0.10 at room temperature, with an energy storage density of 2.04 J/cm
at 178 kV/cm. In addition, the (1-x)LLBNTZ-xNBN ceramics exhibit excellent energy storage properties over a wide temperature range from room temperature to 90 °C. The values of energy storage density and energy storage efficiency is 0.91 J/cm
and 79.51%, respectively, for the 0.90LLBNTZ-0.10NBN ceramic at the condition of 100 kV/cm and 90 °C. It can be concluded that the (1-x)LLBNTZ-xNBN ceramics are promising lead-free candidate materials for energy storage devices over a broad temperature range.
•Microbiome and EPS are the hottest topics in the study of NRGS properties.•NRGS displays satisfactory nitrogen removal efficiency in most cases.•NRGS properties are strongly associated with the ...performance.•Technological advancements provide in-depth insights into NRGS characterization.•Future prospects for research and application of NRGS are proposed.
Nitrogen-removal granular sludge (NRGS) is a promising technology in wastewater treatment, with advantages of efficient nitrogen removal, less footprint, lower sludge production and energy consumption, and is a way for wastewater treatment plants to achieve carbon–neutrality. Aerobic granular sludge (AGS) and anammox granular sludge (AnGS) are two typical NRGS technologies that have attracted extensive attention. Mounting evidence has shown strong associations between NRGS properties and the status of NRGS systems; however, a holistic view is still missing. The aim of this article is to provide an overview of NRGS with an emphasis on characterization. Specifically, the integrated nitrogen transformation pathways inside NRGS and the performance of NRGS treating various wastewaters are discussed. NRGS properties are categorized as physical-, chemical-, biological- and systematical ones, presenting current advances and corresponding characterization technologies. Finally, the future prospects for furthering the mechanistic understanding and engineering application of NRGS are proposed. Overall, the technological advancements in characterization have greatly contributed to understanding NRGS properties, which are potential factors for optimizing the performance and evaluating the working status of NRGS. This review will provide guidance in characterizing NRGS properties and boost the introduction of novel characterization technologies.
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Combination of lightweight and superior electrical conductive performance is charming for the application of macroscopic graphene foam composite. A porous carbon nanotubes/reduced graphene oxide ...(CNTs/RGO) foam composite are prepared by freeze-drying and in-situ catalytic grown methods. The CNTs/RGO foam composite consists of interconnected RGO nanosheets as the 3D frame and in-situ growth CNTs as the electromagnetic wave (EM) absorbing reinforcement, which grow on graphene substrate. The in-situ grown CNTs on graphene nanosheets lead to the enhancement of conductive and polarization loss, which results in the enhancement of absorption shielding performance. The CNTs/RGO foam composites with different CNT loading are prepared to investigate their EM shielding properties in X-band. The EM shielding effectiveness (SE) of CNTs/RGO foam composite reaches 31.2 dB with 2 mm thickness, especially the specific EMI shielding effectiveness reaches 547 dB cm3/g with an ultralight density of 57 mg cm−3, the absorption is the primary shielding mechanism. Furthermore, SE value reaches 49 dB with thickness of 3.1 mm. Owing to the unique 3D foam hierarchical architecture, light density and outstanding SE performance, our work shows a promising designable approach of preparing CNTs/RGO foam composite to lightweight and absorption type EMI shielding materials.
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Spermiogenesis is a complex cellular differentiation process that the germ cells undergo a distinct morphological change, and the protamines replace the core histones to facilitate chromatin ...compaction in the sperm head. Recent studies show the essential roles of epigenetic events during the histone-to-protamine transition. Defects in either the replacement or the modification of histones might cause male infertility with azoospermia, oligospermia or teratozoospermia. Here, we summarize recent advances in our knowledge of how epigenetic regulators, such as histone variants, histone modification and their related chromatin remodelers, facilitate the histone-to-protamine transition during spermiogenesis. Understanding the molecular mechanism underlying the modification and replacement of histones during spermiogenesis will enable the identification of epigenetic biomarkers of male infertility, and shed light on potential therapies for these patients in the future.
Carbon materials, including graphite, hard carbon, soft carbon, graphene, and carbon nanotubes, are widely used as high‐performance negative electrodes for sodium‐ion and potassium‐ion batteries ...(SIBs and PIBs). Compared with other materials, carbon materials are abundant, low‐cost, and environmentally friendly, and have excellent electrochemical properties, which make them especially suitable for negative electrode materials of SIBs and PIBs. Compared with traditional carbon materials, modifications of the morphology and size of nanomaterials represent effective strategies to improve the quality of electrode materials. Different nanostructures make different contributions toward improving the electrochemical performance of electrode materials, so the synthesis of nanomaterials is promising for controlling the morphology and size of electrode materials. This paper reviews the progress made and challenges in the use of carbon materials as negative electrode materials for SIBs and PIBs in recent years. The differences in Na+ and K+ storage mechanisms among different types of carbon materials are emphasized.
Carbon materials represent one of the most promising candidates for negative electrode materials of sodium‐ion and potassium‐ion batteries (SIBs and PIBs). This review focuses on the research progress of carbon materials such as graphite, hard carbon, soft carbon, graphene and carbon nanotubes, and other carbon nanomaterials as negative electrode materials for SIBs and PIBs.
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