Price volatility spillovers among China’s crude oil, corn and fuel ethanol markets are analyzed based on weekly price data from September 5, 2003 to August 31, 2012, employing the univariate EGARCH ...model and the BEKK-MVGARCH model, respectively. The empirical results indicate a higher interaction among crude oil, corn and fuel ethanol markets after September, 2008. In the overall sample period, the results simultaneously provide strong evidence that there exist unidirectional spillover effects from the crude oil market to the corn and fuel ethanol markets, and double-directional spillovers between the corn market and the fuel ethanol market. However, the spillover effects from the corn and fuel ethanol markets to the crude oil market are not significant.
•Employing univariate EGARCH model and BEKK-MVGARCH model, respectively. Unidirectional spillover effects from crude oil market to corn and fuel ethanol markets.•Double-directional spillovers between corn market and fuel ethanol market.•The spillover effects from corn and fuel ethanol markets to crude oil market are not significant.•The empirical results indicate a higher interaction among crude oil, corn and fuel ethanol markets after September, 2008.
Graphene quantum dots (GQDs) are great promising in various applications owing to the quantum confinement and edge effects in addition to their intrinsic properties of graphene, but the preparation ...of the GQDs in bulk scale is challenging. We demonstrated in this work that the micrometer sized graphene oxide (GO) sheets could react with Fenton reagent (Fe2+/Fe3+/H2O2) efficiently under an UV irradiation, and, as a result, the GQDs with periphery carboxylic groups could be generated with mass scale production. Through a variety of techniques including atomic force microscopy, X-ray photoelectron spectroscopy, gas chromatography, ultraperformance liquid chromatography–mass spectrometry, and total organic carbon measurement, the mechanism of the photo-Fenton reaction of GO was elucidated. The photo-Fenton reaction of GO was initiated at the carbon atoms connected with the oxygen containing groups, and C–C bonds were broken subsequently, therefore, the reaction rate depends strongly on the oxidization extent of the GO. Given the simple and efficient nature of the photo-Fenton reaction of GO, this method should provide a new strategy to prepare GQDs in mass scale. As a proof-of-concept experiment, the novel DNA cleavage system using as-generated GQDs was constructed.
A certified 25.2% efficiency of metal halide perovskite solar cells (PSCs) has been rapidly reached in 2019 within just a decade which is unprecedented in the field of photovoltaics. Excellent ...optoelectronic properties such as high absorption coefficient, tunable direct bandgap, long diffusion length, and high carrier mobility promise a further improvement of device performance. However, as a result of the solution precursor compositions and rapid processing conditions, tremendous amounts of defects with various types are formed within perovskite absorbers or on the surfaces, which serve as the nonradiative recombination centers to impede the rapid development of PSCs. Therefore, learned from the field of mature Silicon-based solar cell, passivation of such defects in the bulk and/or at the surface, as well as influence the interface tuning of structure and energetics has to be urgently conducted by choosing appropriate chemical molecules, which have the potential of tailoring crystallization and growth of perovskite absorbers. Here, recent advances in passivation engineering for perovskite film formation or interface optimization are summarized and discussed according to the following typical categories: Lewis acid (e.g., metal cations, organic cations, zwitterion, fullerene derivatives), Lewis base based on the donor type (e.g., anions, S-donor, N-donor, O-donor, graphene derivatives, and n-π conjugated materials), passivators with multifunctional groups. Finally, a perspective is predicted on future research trends concerning passivation engineering in advancing the development of PSCs, especially in efficiency, stability, and commercialization.
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•Defects in the surface and GB of PSCs seriously limit efficiency enhancement.•The diversity of defects require passivators with different passivation capacities.•Different functional groups of passivators determine the effect of passivation.•The mechanisms of passivators with different functional groups are reviewed.
With rapid economic development, China has been plagued by choking air pollution in recent years, and the frequent occurrence of haze episodes has caused widespread public concern. The purpose of ...this study is to describe the sources and formation of haze, summarize the mitigation measures in force, review the relationship between haze pollution and public health, and to discuss the challenges, potential research directions and policy options. Haze pollution has both natural and man-made causes, though it is anthropogenic sources that are the major contributors. Accumulation of air pollutants, secondary formation of aerosols, stagnant meteorological conditions, and trans-boundary transportation of pollutants are the principal causes driving the formation and evolution of haze. In China, haze includes gaseous pollutants and fine particles, of which PM2.5 is the dominant component. Short and long-term exposure to haze pollution are associated with a range of negative health outcomes, including respiratory diseases, cardiovascular and cerebrovascular diseases, mental health problems, lung cancer and premature death. China has paid increasing attention to the improvement of air quality, and has introduced action plans and policies to tackle pollution, but many interventions have only temporary effects. There may be fierce resistance from industry groups and some government agencies, and often it is challenging to enforce relevant control measures and laws. We discuss the potential policy options for prevention, the need for wider public dialogue and the implications for scientific research.
The sources, formation, and health effects of haze pollution in China. Display omitted
•The relationship between haze pollution and public health in China was reviewed for the first time.•The sources and formation of haze episode were described.•The existing mitigation measures and challenges faced China were summarized.•The potential policy options and future research directions were discussed.•Individual prevention measures during haze events from the public aspects were further suggested.
Biochemical and biomedical applications of graphene oxide (GO) critically rely on the interaction of biomolecules with it. It has been previously reported that the biological activity of the ...GO–enzyme conjugate decreases due to electrostatic interaction between the enzymes and GO. Herein, the immobilization of horseradish peroxidase (HRP) and oxalate oxidase (OxOx) on chemically reduced graphene oxide (CRGO) are reported. The enzymes can be adsorbed onto CRGO directly with a tenfold higher enzyme loading than that on GO, and maximum enzyme loadings reach 1.3 and 12 mg mg−1 for HRP and OxOx, respectively. Significantly, the more CRGO is reduced, the higher the enzyme loading. The CRGO–HRP conjugates also exhibit higher enzyme activity and stability than GO–HRP. Excellent properties of the CRGO–enzyme conjugates are attributed to hydrophobic interaction between the enzymes and the CRGO. The hydrophobic interaction mode of the CRGO–enzyme conjugates can be applied to other hydrophobic proteins, and thus could dramatically improve the performance of immobilized proteins. The results indicate that CRGO is a potential substrate for efficient enzyme immobilization, and is an ideal candidate as a macromolecule carrier and biosensor.
The enzyme loadings on chemically reduced graphene oxide (CRGO) increase with the hydrophobicity of the CRGO surface, thus suggesting that hydrophobic interaction is a driving force for the enzyme immobilization. These results indicate that CRGO is an ideal candidate as a macromolecule carrier and biosensor.
Brain-inspired electronics require artificial synapses that have ultra-low energy consumption, high operating speed, and stable flexibility. Here, we demonstrate a flexible artificial synapse that ...uses a rapidly crystallized perovskite layer at room temperature. The device achieves a series of synaptic functions, including logical operations, temporal and spatial rules, and associative learning. Passivation using phenethyl-ammonium iodide eliminated defects and charge traps to reduce the energy consumption to 13.5 aJ per synaptic event, which is the world record for two-terminal artificial synapses. At this ultralow energy consumption, the device achieves ultrafast response frequency of up to 4.17 MHz; which is orders of magnitude magnitudes higher than previous perovskite artificial synapses. A multi-stimulus accumulative artificial neuromuscular system was then fabricated using the perovskite synapse as a key processing unit to control electrochemical artificial muscles, and realized muscular-fatigue warning. This artificial synapse will have applications in future bio-inspired electronics and neurorobots.
This paper explores the impact of risk preference as well as interlinked credit and insurance contract on peasants’ new technology adoption. The results show that (1) risk preference has a ...significant impact on peasants’ adoption of innovative seeds, and the influence of exact probabilistic risk preference on peasants’ adoption of innovative seeds is greater than that of ambiguous probabilistic risk preference. (2) Interlinked credit and insurance contract has a significant positive impact on peasants’ adoption of innovative seeds, and interlinked credit and insurance contract plays a moderating role in promoting peasants’ adoption of innovative seeds. (3) Peasants’ education level, the degree of land fragmentation, the proportion of grain cultivation in the household-cultivated land, whether to provide meteorological disaster warning services, and the distance to financial services also have a significant impact on peasants’ adoption of innovative seeds. This interplay between collateral and the nature of credit-insurance interlinkage has direct and important implications for the design of programs to boost the adoption of innovative agricultural technologies simultaneously, and sheds light upon how the government can formulate relevant policies to promote innovative technological development.
Microorganisms are applied to remediate chromium (Cr)-contaminated soil extensively. Nevertheless, the microbial loss and growth inhibition in the soil environment restrain the application of this ...technology. In this study, a Cr(VI)-reducing strain named
WHX-1 was screened, and the microbial aggregates system was established via immobilizing the strain on
biochar to enhance the Cr(VI)-reducing activity of this strain. The mechanism of the system on Cr(VI) transformation in Cr-contaminated soil was illuminated. Pot experiments indicated that the microbial aggregates system improved the physicochemical characteristics of Cr-contaminated soil obviously by increasing organic carbon content and cation exchange capacity, as well as decreasing redox potential and bulk density of soil. Moreover, 94.22% of Cr(VI) was transformed into Cr(III) in the pot, and the content of residue fraction Cr increased by 63.38% compared with control check (CK). Correspondingly, the physiological property of
planted on the Cr-contaminated soil was improved markedly and the main Cr(VI)-reducing microbes,
spp., were enriched in the soil with a relative abundance of 28.43% in the microbial aggregates system. Considering more active sites of biochar for microbial aggregation, it was inferred that
WHX-1 could be immobilized by
biochar, and more Cr(VI) was transformed into residue fraction. Cr stress was decreased and the growth of plants was enhanced. This study would provide a new perspective for Cr-contaminated soil remediation.
Severe fever with thrombocytopenia syndrome (SFTS) is emerging and the number of SFTS cases increased year by year in China. In order to explore the epidemiology trend, we analyzed the changing ...epidemiological characteristics of SFTS cases in different years and compare characteristics in different provinces. From 2011 to 2016, a total of 5360 laboratory-confirmed SFTS cases were reported and annual case numbers increased year by year. Most SFTS cases occurred in individuals aged between 40 years and 80 years (91.57%), but age distributions of SFTS cases in different years were significantly different and the median ages increased slightly year by year. The numbers of affected counties from 2011 to 2016 increased sharply from 98 to 167. Of note, the seasonal distributions of SFTS cases in different provinces were significantly different (Fisher = 712.157, P = 0.000) and provinces in south regions showed earlier epidemic peak and longer epidemics durations. The median time from illness onset to confirmation of different years was significantly different (χ
= 896.088, P = 0.000) and it peaked in 2014. Furthermore, case fatality rate was associated with province, year, and age of SFTS cases. These results may be helpful for authorities to better preventive strategy and improve interventions against SFTS.
The exhaust gas from pyrolysis of ZIF-67 was used as carbon precursor to prepare high-performance PC for supercapacitor electrodes by deposition in hard templates.
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•Porous carbon with ...high supercapacitor performance is prepared.•Exhaust gas derived from pyrolysis of zeoliticimidazolate framework is used as carbon precursor.•Efficient utilization of exhaust gas is realized.•The microporous structure makes porous carbon have high capacitance of 445.7 F g−1 in supercapacitor.
Pyrolyzing carbon precursors will also lead to a large amount of exhaust gas, which is a waste of resources and a huge pollution. Therefore, realizing the full utilization of exhaust gas from carbon precursors is significant. Herein, cobalt (Co) modified hard templates with micropores or mesopores is used to prepare porous carbon for supercapacitors, in which Co species provide the active sites for the capture and deposition of exhaust gas derived from zeoliticimidazolate framework. Using N2 as protective and carrier gas, the whole process can be realized in a simple tubular furnace. The obtained PC can replicate the morphology and pore structure of the hard template with the characteristics of micropores or mesopores respectively. The microporous structure of PC gives it higher surface area and pore volume than PC with mesopores, which makes it have high capacitance of 445.7 F g−1 in supercapacitor.
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