Active carbons have unique physicochemical properties, but their conductivities and surface to weight ratios are much poorer than graphene. A unique and facile method is innovated to chemically ...process biomass by “drilling” holes with H2O2 and exfoliating into graphene‐like nanosheets with HAc, followed by carbonization at a high temperature for highly graphitized activated carbon with greatly enhanced porosity, unique pore structure, high conductivity, and large surface area. This graphene‐like carbon exhibits extremely high specific capacitance (340 F g−1 at 0.5 A g−1) and high specific energy density (23.33 to 16.67 W h kg−1) with excellent rate capability and long cycling stability (remains 98% after 10 000 cycles), which is much superior to all reported carbons including graphene. Synthesis mechanism for deriving biomass into porous graphene‐like carbons is discussed in detail. The enhancement mechanism for the porous graphene‐like carbon electrode reveals that rationally designed meso‐ and macropores are very critical in porous electrode performance, which can network micropores for diffusion freeways, high conductivity, and high utilization. This work has universal significance in producing highly porous and conductive carbons from biomass including biowastes for various energy storage/conversion applications.
A graphene‐like porous activated carbon derived from a biomass fabricated, rationally designed chemical process, followed by carbonization at high temperature, exhibits a specific capacitance of 340 F g−1 at 0.5 A g−1 and high specific energy density (23.33–16.67 W h kg−1), with excellent capacity retention after 10 000 cycles, superior to other carbon electrodes.
Abstract
Soybean red crown rot (RCR) is caused by the soilborne fungal pathogen
Calonectria ilicicola
. It causes root rot, leaf senescence, early defoliation, plant wilting and even death, often ...resulting in a severe reduction in seed yield and quality.
C. ilicicola
is an extremely difficult pathogen to control owing to its wide host range and long survival in soil and plant debris. Currently, no practically effective fungicide for this pathogen is available. Breeding for resistance is considered the most effective and environmentally acceptable means of disease management, but no
C
.
ilicicola
‐resistant soybean variety has yet been identified. Given this situation, it is necessary to promote our understanding of the mechanism of RCR incidence and the development of a comprehensive and sustainable RCR management strategy urgently.
Improving the stability of sensitive catalytic systems is an emerging research topic in the catalysis field. However, the current design of heterogeneous catalysts mainly improves their catalytic ...performance. This paper presents a single‐atom catalyst (SAC) strategy to improve the cobalt‐catalysed fluorination of acyl chlorides. A stable Co−F intermediate can be formed through the oxidative fluorination of Co1−N4@NC SAC, which can replace the unstable high‐valent cobalt catalytic system and avoid the use of phosphine ligands. In the SAC system, KF can be employed as a fluorinating reagent to replace the AgF, which can be applied to various substrates and scale‐up conversion with high turnover numbers (TON=1.58×106). This work also shows that inorganic SACs have tremendous potential for organofluorine chemistry, and it provides a good reference for follow‐up studies on the structure‐activity relationship between catalyst design and chemical reaction mechanisms.
A Co single‐atom catalyst was synthesized via thermal decomposition of a zeolitic imidazolate framework (ZIF). The Co1−N4@NC catalyst generated a stable Co−F intermediate in situ through an oxidative fluorination pathway to replace the substitution fluorination of the unstable high‐valent Co system. In the presence of Co−F intermediates, KF can be used to replace AgF. Co1−N4@NC exhibited ultrahigh catalytic activity for the fluorination of acyl chlorides.
Hydrothermal carbonization of cellulose, lignin, d-xylose (substitute for hemicellulose), and wood meal (WM) was experimentally conducted between 225 and 265 °C, and the chemical and structural ...properties of the hydrochars were investigated. The hydrochar yield is between 45 and 60%, and the yield trend of the feedstock is lignin > WM > cellulose > d-xylose. The hydrochars seem stable below 300 °C, and aromatic structure is formed in all of these hydrochars. The C content, C recovery, energy recovery, ratio of C/O, and ratio of C/H in all of these hydrochars are among 63–75%, 80–87%, 78–89%, 2.3–4.1, and 12–15, respectively. The higher heating value (HHV) of the hydrochars is among 24–30 MJ/kg, with an increase of 45–91% compared with the corresponding feedstock. The carbonization mechanism is proposed, and furfural is found to be an important intermediate product during d-xylose hydrochar production, while lignin hydrothermal carbonization products are made of polyaromatic hydrochar and phenolic hydrochar. The formation of microspheres on the surface of cellulose and WM hydrochars is discussed, and transformation of the hemicellulose should be the reaction for WM microsphere production.
•The prevalence of anxiety symptom and depressive symptom during the COVID-19 pandemic were relatively high.•The prevalence of anxiety symptom and depressive symptom varies among different countries’ ...college students.•The pooled prevalence of depressive symptom in females was higher compared with males.
The global pandemic of COVID-19 has brought huge changes to people's lifestyles, college students have also been affected seriously. Evidence about these significant changes indicated that college students were more prone to feel anxious and depressed. To derive a precise assessment of the prevalence of anxiety symptom and depressive symptom among college students worldwide, we conducted this meta-analysis.
Based on the guidance of PRISMA, literature was searched in Pubmed, Web of Science, Embase, and PsycArticles (last search November 6, 2020). These articles after the screening were analyzed by a random-effects model to estimate the pooled prevalence of anxiety symptom and depressive symptom. Also, subgroup analysis, sensitivity analysis, and publication bias were performed in this meta-analysis.
The results showed that the pooled anxiety symptom prevalence was 31% (95% CI: 23-39%), pooled depressive symptom prevalence was 34% (95% CI: 27-41%). Subgroup analysis showed that the prevalence of anxiety symptom and depressive symptom among different countries’ college students were different, and the pooled depressive symptom prevalence of females was higher compared with males.
The prevalence of anxiety symptom and depressive symptom in worldwide college students could be better assessed by a standard and reliable questionnaire.
The results suggest that the prevalence of anxiety symptom and depressive symptom during the COVID-19 pandemic is relatively high. Except for interventions that should be taken to control the pandemic urgently, mental health services are also needed to decrease the risk of anxiety and depression among college students.
Binary relations, coverings and neighborhood systems/operators are useful tools to study fuzzy rough set theory. In this paper, we use the notion of real-valued hemimetric, a weak version of the ...standard metric, as the basic structure to define and study fuzzy rough sets by using the usual addition and subtraction of real numbers. We define a pair of fuzzy upper and lower rough approximation operators and investigate their properties and interrelations. These two operators have nice logical descriptions by using the Lukasiewicz logical system. It is shown that upper definable fuzzy subsets, lower definable fuzzy subsets and Lipschitz fuzzy subsets are the same thing in this model. Definable fuzzy subsets are exactly the upper sets with respect to the induced fuzzy preorder, which form a stratified Alexandrov fuzzy topology. A comparison between hemimetric-based fuzzy rough sets and fuzzy preorder-based fuzzy rough sets has been made. Results show that the former can be considered as a real-valued extension of the latter. At the end, an application of the hemimetric-based rough set model to contour extraction of digital surfaces is proposed.
A chemical vapor deposition method is developed for thickness‐controlled (one to four layers), uniform, and continuous films of both defective gallium(II) sulfide (GaS): GaS0.87 and stoichiometric ...GaS. The unique degradation mechanism of GaS0.87 with X‐ray photoelectron spectroscopy and annular dark‐field scanning transmission electron microscopy is studied, and it is found that the poor stability and weak optical signal from GaS are strongly related to photo‐induced oxidation at defects. An enhanced stability of the stoichiometric GaS is demonstrated under laser and strong UV light, and by controlling defects in GaS, the photoresponse range can be changed from vis‐to‐UV to UV‐discriminating. The stoichiometric GaS is suitable for large‐scale, UV‐sensitive, high‐performance photodetector arrays for information encoding under large vis‐light noise, with short response time (<66 ms), excellent UV photoresponsivity (4.7 A W–1 for trilayer GaS), and 26‐times increase of signal‐to‐noise ratio compared with small‐bandgap 2D semiconductors. By comprehensive characterizations from atomic‐scale structures to large‐scale device performances in 2D semiconductors, the study provides insights into the role of defects, the importance of neglected material‐quality control, and how to enhance device performance, and both layer‐controlled defective GaS0.87 and stoichiometric GaS prove to be promising platforms for study of novel phenomena and new applications.
A chemical vapor deposition method is developed for controlling defects in gallium(II) sulfide (GaS), and their influence on the UV photosensing response in devices is elucidated. Defects in GaS act as sites of photoinduced oxidation and degradation. High‐quality GaS 2D films show uniform UV photodetector response and defect tuning enables selective UV sensing.
Biomass fast pyrolysis liquefaction has aroused great attention and interests both at home and abroad extensively in recent years. This paper reviews the physicochemical properties and discusses the ...characteristics of the components and compositions of biomass pyrolysis oil. Furthermore, the problems and focuses were summarized with some suggestions presented on upgrading and applications of bio-oil in the decades.
Summary
Anthocyanin biosynthesis is induced by low temperatures in a number of plants. However, in peach (cv Zhonghuashoutao), anthocyanin accumulation was observed in fruit stored at 16°C but not at ...or below 12°C. Fruit stored at 16°C showed elevated transcript levels of genes encoding anthocyanin biosynthetic enzymes, the transport protein glutathione S‐transferase and key transcription factors. Higher transcript levels of PpPAL1/2, PpC4H, Pp4CL4/5/8, PpF3H, PpF3’H, PpDFR1/2/3 and PpANS, as well as transcription factor gene PpbHLH3, were associated with lower methylation levels in the promoter of these genes. The DNA methylation level was further highly correlated with the expression of the DNA methyltransferase genes and DNA demethylase genes. The application of DNA methylation inhibitor 5‐azacytidine induced anthocyanin accumulation in peach flesh, further implicating a critical role for DNA demethylation in regulating anthocyanin accumulation in peach flesh. Our data reveal that temperature‐dependent DNA demethylation is a key factor to the post‐harvest temperature‐dependent anthocyanin accumulation in peach flesh.
Significance Statement
Anthocyanin accumulates at 16°C but not below 12°C in an originally white‐fleshed peach cultivar, accompanied by a global increase in transcript levels of anthocyanin biosynthetic and transcription factor genes. Elevated transcript levels are associated with decreases in DNA methylation as a result of regulating expression of DNA methyltransferase and DNA demethylase genes. The involvement of DNA demethylation in induction of anthocyanin accumulation was further confirmed using fruit treated with the DNA methylation inhibitor 5‐azacytidine.
Lignin is a carbon-rich renewable source owning aromatic structure units, which is an important constituent in biomass. Hydrothermal conversion of lignin is widely studied as a promising method to ...produce not only bioenergy but also value-added useful chemicals. Fuel gas, aromatic aldehydes and phenolic products can be obtained from lignin hydrothermal gasification, wet oxidation and hydrothermal liquefaction, respectively. This article discusses and compares the three methods of lignin hydrothermal conversion, including their process parameters, possible conversion routes, catalysts, application of products. Effects of hot-compressed organic solvent–water mixture solution on conversion of lignin and effects of lignin in biomass hydrothermal conversion are commented. Wet oxidation of lignin is an efficient mean of recovering value-added aromatic aldehydes, especially vanillin. Hydrothermal liquefaction of lignin is a promising way of recovering phenolics-rich bio-oils. Both aromatic aldehyde and phenolic compound are important chemical intermediates. There are strict requirements of process conditions and relative high costs to get fuel gas from direct hydrothermal gasification of lignin. However, further studies on improving gasification of lignin seem necessary in order to get fuel gas from hydrothermal gasification of the whole biomass.
PDF
