Using single-atom catalysts for the electrochemical reduction of carbon dioxide is a promising method for excess renewable electricity as chemical energy in fuels. In this study, we have investigated single non-noble metal atoms supported on nitrogen-doped graphene (M-N4@Gr, where M = Fe, Co, Ni) as catalysts for the electrocatalytic reduction of CO2 using first-principles density functional theory and the computational hydrogen electrode model. The results show that HCOOH is the preferred product of CO2 reduction on the Ni-N4@Gr catalyst with an overpotential of 1.511 V, while Fe-N4@Gr and Co-N4@Gr prefer to reduce CO2 to CH4 with the overpotential of 0.877 and 0.687 V, respectively. The computational results revealed that the coordination environment affects d orbital occupations, leading to a difference in the spin polarization of the systems and thus affecting the performance and selectivity of catalysts. Our work may pave the way for extending single non-noble atom catalysts, which consist of earth-abundant elements, toward electrocatalytic CO2 reduction reaction by regulating coordination environments.

Thermomyces dupontii, a widely distributed thermophilic fungus, is an ideal organism for investigating the mechanism of thermophilic fungal adaptation to diverse environments. However, genetic analysis of this fungus is hindered by a lack of available and efficient gene manipulating tools. In this study, two different Cas9s from mesophilic and thermophilic bacteria, with in vivo sgRNA expression under the control of tRNAGly, were successfully adapted for genome editing in T. dupontii. We demonstrated the feasibility of applying these two gene editing systems to edit one or two genes in T. dupontii. The mesophilic CRISPR/Cas9 system displayed higher editing efficiency (50-86%) than the thermophilic CRISPR/Cas9 system (40-67%). However, the thermophilic CRISPR/Cas9 system was much less time-consuming than the mesophilic CRISPR/Cas9 system. Combining the CRISPR/Cas9 systems with homologous recombination, a constitutive promoter was precisely knocked in to activate a silent PKS-NRPS biosynthetic gene, leading to the production of extra metabolites that did not exist in the parental strains. Metabolic analysis of the generated biosynthetic gene mutants suggested that a key biosynthetic pathway existed for the biosynthesis of thermolides in T. dupontii, with the last two steps being different from that in the heterologous host Aspergillus. Further analysis suggested that these biosynthetic genes might be involved in fungal mycelial growth, conidiation, and spore germination, as well as in fungal adaptation to osmotic, oxidative and cell-wall-perturbing agents. IMPORTANCE Thermomyces represents a unique ecological taxon in fungi, but a lack of flexible genetic tools has greatly hampered the study of gene function in this taxon. The biosynthesis of potent nematicidal thermolides in T. duponti remains largely unknown. In this study, mesophilic and thermophilic CRISPR/Cas9 gene editing systems were successfully established for both disrupting and activating genes in T. duponti. In this study, a usable thermophilic CRISPR/Cas9 gene editing system derived from bacteria was constructed in thermophilic fungi. Chemical analysis of the mutants generated by these two gene editing systems identified the key biosynthetic genes and pathway for the biosynthesis of nematocidal thermolides in T. dupontii. Phenotype analysis and chemical stress experiments revealed potential roles of secondary metabolites or their biosynthetic genes in fungal development and adaption to chemical stress conditions. These two genomic editing systems will not only accelerate investigations into the biosynthetic mechanisms of unique natural products and functions of cryptic genes in T. duponti, but also offer an example for setting up CRISPR/Cas9 systems in other thermophilic fungi.

Electrochemical reduction of CO2 to high-energy chemicals is a promising strategy for achieving carbon-neutral energy circulation. However, designing high-performance electrocatalysts for the CO2 reduction reaction (CO2RR) remains a great challenge. In this work, by means of density functional theory calculations, we systematically investigate the transition metal (TM) anchored on the nitrogen-doped graphene/graphdiyne heterostructure (TM-N4@GRA/GDY) as a single-atom catalyst for CO2 electroreduction applications. The computational results show that Co–N4@GRA/GDY exhibits remarkable activity with a low limiting potential of −0.567 V for the reduction of CO2 to CH4. When the charged Co-N4@GRA/GDY system is immersed in a continuum solvent, the reaction barrier decreases to 0.366 eV, which is ascribed to stronger electron transfer between GDY and transition metal atoms in the GRA/GDY heterostructure. In addition, the GRA/GDY heterostructure system significantly weakens the linear scaling relationship between the adsorption free energy of key CO2 reduction intermediates, which leads to a catalytic activity that is higher than that of the single-GRA system and thus greatly accelerates the CO2RR. The electronic structure analysis reveals that the appropriate d−π interaction will affect the d orbital electron distribution, which is directly relevant to the selectivity and activity of catalysis. We hope these computational results not only provide a potential electrocatalyst candidate but also open up an avenue for improving the catalytic performance for efficient electrochemical CO2RR.

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The propagation and evolution model of botnet is the most common method to study the spreading features of bots, but current botnets' propagation and e volution models limited to describe active spread process based on worms, don't consider the passive spread process similar to "plugged Trojan-horse into webpage", so these models can not exactly describe how the bots spread on the Internet. In this paper, a new botnet propagation and evolution model (WT-S IR) was proposed. This model carefully considers about the real situation of the Internet, especially probability of bots' status transformed from infected and immune to susceptible. Simulation result shows that the WT-S IR model more exactly satisfies the practical propagation laws and infection characteristics of bots on Internet. Keywords-botnet; Propagation and evolution model; WT-SIR;I.INTRODUCTION Botnet propagation and evolution models main ly used to describe the process of bot nodes join or leave the Botnet influenced by different factors, it is used to depict the relationship between the number of infected nodes and spread-time, address scanning space, network topology and the distribution of sensible nodes.Research on models of Botnet propagation and evolution can describe characteristics of the Botnet propagation to some extent, it is also make sense to understand the propagation law, predict the propagation tendency, and improve the accuracy of the Bot program transmission. At the same time, it can reduce the possibility of vulnerability exposure, extend the survival time of transmission module of bot program, and earn the maximu m benefit before specific vulnerabilities were announced.Classical Botnet propagation and evolution models are based on infectious disease model used by worms, try to analysis the process of state transition and steady state characteristics of infected nodes. Nowadays, worm propagation models main ly including SEM model, SI model[1], SIS model[2], KM (Kermack -Mckendrick) model, SIR model[3], double factors (Two -Factor) model[4], SIRS model[5], SEIRS model[6], DSIR model[7] and ADSIR model[8], etc.Because all sorts of Botnets adopted different propagation methods, and during the process of propagation the network environments and infection targets are also