One-Step Synthesis of Porous Graphitic Carbon Nitride and the Photocatalytic Performance under Visible-Light Irradiation

Porous graphitic carbon nitride (pg-C3N4) was synthesized via a facile one-step dicyandiamide (DCDA) high-temperature calcination method using heat-labile ammonium bicarbonate (NH4HCO3) as the gaseous template, and different pg-C3N4 materials were obtained by mixing various mass ratios of NH4HCO3 into DCDA. The micro-structures and -morphologies of the porous materials were characterized by X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) respectively, and the photocatalytic degradation of methylene blue (MB) dye was tested under visible-light irradiation. It is found that the thermal decomposition of NH4HCO3 promoted destruction of the layer-structured g-C3N4 and increment of the specific surface area, producing more porous structures on the material surfaces, which is considered to be vital for the improvement of photocatalytic performance. Compared with the photocatalyst calcined by pure DCDA, the pg-C3N4 photocatalysts obtained by mixing the two raw materials performed better on MB dye degradation. Moreover, photocatalytic efficiency of the catalysts improved significantly with increasing NH4HCO3 contents in the raw materials. The degradation rate photocatalyzed by pg-C3N4 materials can reach more than 90% within 1.5 h, 6.5 times higher than that of the control material. It comes up to 99% at 2 h, basically achieving the complete degradation and decolorization of MB dye

Quantifying Wave–Particle Interactions in Collisionless Plasmas: Theory and Its Application to the Alfvén-mode Wave

Wave–particle interactions can induce energy transfer at different timescales in collisionless plasmas, which leads to the reshaping of the particle velocity distribution function. Therefore, how to quantify wave–particle interactions is one of the fundamental problems in the heliosphere and in astrophysical plasmas. This study proposes a systematic method to quantify linear wave–particle interactions based on the Vlasov–Maxwellian model. We introduce energy transfer rates with various expressions by using perturbed electric fields and perturbed particle velocity distribution functions. Then, we use different expressions of the energy transfer rate to perform a comprehensive investigation of wave–particle interactions of the Alfvén-mode wave. We clarify the physical mechanisms responsible for the damping of the Alfvén-mode wave in wavevector space. Moreover, this study exhibits for the first time evident signatures of wave–particle interactions between Alfvén-mode waves and resonant/nonresonant particles in the velocity space. These resonant and nonresonant particles can induce energy transfer in opposite directions, which leads to self-regulation of the particle velocity distribution function. Furthermore, this study exhibits a comprehensive dependence of wave–particle interactions of the Alfvén-mode wave on the wavenumber and plasma beta (the ratio between the plasma thermal pressure and the magnetic pressure). These results illustrate that the proposed method would be very useful for quantifying different types of linear wave–particle interactions of an arbitrary wave mode

Complete chloroplast genome of Morinda parvifolia (Rubiaceae), a traditional medicinal plant in China

Morinda parvifolia is a traditional medicinal plant of the family Rubiaceae. In the current study, the complete chloroplast genome of M. parvifolia was sequenced and reported for the first time. The genome is 153,069 bp in total length, containing two inverted repeats (IR) regions of 25822 bp which were separated by a large single copy (LSC) region of 83813 bp and a small single copy (SSC) region of 17612 bp. A total of 131 gene species were annotated, including 86 protein-coding genes,37 tRNA genes, and 8 rRNA genes. The overall GC content of the genome is 38.07%. The phylogenetic analysis based on the complete chloroplast genome reveals that M. parvifolia is closely related to Morinda officinalis. This study enriches the genetic information of M. parvifolia as well as for the phylogenetic studies for Rubiaceae

Equity Incentives and Audit Opinions Shopping

【中文摘要】 与国外股权激励模式不同，我国实行的是业绩型股权激励，而签字审计师承担着对企业财务报告的监督职责，研究股权激励对审计的影响具有重要的现实意义。本文以 2006～2016 年我国沪深两市 A 股（A-shares，人民币普通股票）非金融类上市公司为样本，运用双重差分倾向得分匹配法和 Lennox（2000）的审计意见购买模型，研究分析股权激励对企业审计意见购买的影响。研究结果表明，股权激励抑制了企业的审计意见购买，支持最优契约假说。进一步的研究发现，在区分了企业的产权性质和管理层权力后，股权激励对审计意见购买具有抑制作用，主要体现在非国有企业；管理层权力削弱了股权激励对审计意见购买的抑制作用，甚至当董事长和总经理两职合一时，股权激励甚至会强化企业进行审计意见购买。研究表明股权激励在我国上市企业的公司治理中仍然发挥着积极正面的作用。本文的研究丰富了与股权激励和审计意见购买相关的文献。 【Abstract】In contrast to the equity incentive model in international studies，equity incentives in China are implemented based on accounting performance. Since CPAs take the responsibility of auditing firms’ financial reports，it is of great importance to study the effect of equity incentives on the behaviors of a firm's auditor. Based on a sample of non-financial companies listed in the A-shares market in China from 2006 to 2016，this paper studies the impact of equity incentives on the audit opinion shopping by applying the difference in differences propensity score matching method and the audit opinion shopping model of Lennox(2000). Our results show that equity incentives inhibit the opinion shopping，which supports the optimal contract hypothesis. Further analysis suggests that such inhibition always exists in thenon-state-owned enterprises and that managerial power weakens such inhibition.In particular，when CEO also serves as chairman of the board，equity incentives will strengthen the opinion shopping. Overall，our results show that equity incentivesplay a positive role in the corporate governance of listed companies in China.本文为国家自然科学基金青年项目“审计师处罚的溢出效应研究”（71702032）、福建省科技厅软科学项目“财务重述与会计师事务所审计项目负责人配置”（2018R0015）、福建省高等学校新世纪优秀人才支持计划项目（2018）的阶段性成果

Complete chloroplast genome sequence of Bambusa subtruncata (Bambusodae)

Bambusa subtruncata is found in Xinyi county, Maoming city, Guangdong province, China. In the current study, we sequenced the complete chloroplast genome of B. subtruncata and reported for the first time. The genome was 139,444 bp in total length, including a large single-copy (LSC) region of 82,956 bp, a small single-copy (SSC) region of 12,897 bp, and a pair of invert repeats (IR) regions of 21,798 bp. Plastid genome comprised of 127 genes in total; 82 protein-coding genes, 37 tRNA genes, and eight rRNA genes. Phylogenetic analysis based on 25 chloroplast genomes indicates that B. subtruncata is closely related to Bambusa emeiensis in Bambusodae

Electron Heat Flux Instabilities in the Inner Heliosphere: Radial Distribution and Implication on the Evolution of the Electron Velocity Distribution Function

This Letter investigates the electron heat flux instability using the radial models of the magnetic field and plasma parameters in the inner heliosphere. Our results show that both the electron acoustic wave and the oblique whistler wave are unstable in the regime with large relative drift speed (ΔVe) between electron beam and core populations. Landau-resonant interactions of electron acoustic waves increase the electron parallel temperature that would lead to suppressing the electron acoustic instability and amplifying the growth of oblique whistler waves. Therefore, we propose that the electron heat flux can effectively drive oblique whistler waves in an anisotropic electron velocity distribution function. This study also finds that lower-hybrid waves and oblique Alfvén waves can be triggered in the solar atmosphere, and that the former instability is much stronger than the latter. Moreover, we clarify that the excitation of lower-hybrid waves mainly results from the transit-time interaction of beaming electrons with resonant velocities vP ∼ ω/kP, where ω and kP are the wave frequency and parallel wavenumber, respectively. In addition, this study shows that the instability of quasi-parallel whistler waves can dominate the regime with medium ΔVe at the heliocentric distance nearly larger than 10 times of the solar radius