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Cp*CoIII-catalyzed C–H amidation/annulation of 2-phenyl-1H-imidazoles with 1,4,2-dioxazol-5-ones were developed to give imidazo[1,2-c]quinazoline derivatives with broad substrate scope in moderate to good yields.

Majority of Mn

A synthetic protocol based on Cp*Co

The space charge in dielectric materials is closely related to the aging of insulating materials under DC voltage. In order to further reveal the aging process of ultra-high voltage direct current (UHVDC) dry bushing, it is necessary to study the space characteristics of epoxy resin used in the bushing during aging process. The epoxy resin samples were prepared in vacuum condition. The samples were aged for 24 hours under the dc stress of 60 kV/mm at different temperature (40, 60, 80 and 100 °C). The space charge in the samples during the aging process was simultaneously measured with improved pulsed electro-acoustic (PEA) system. When the temperatures are less than or equal to 60 °C, there are only homocharge accumulations in the sample bulks. When the temperatures are higher than or equal to 80 °C, the homocharge accumulations near both of the electrodes are the same as the conditions at low temperatures at first. Then subsequently, with the increase of aging time, the positive charge accumulation gradually occurs near the cathode at high temperatures. The higher the temperature is, the sooner the positive charge accumulated near the cathode appears, and the larger the amount of the positive charge is. The characteristics of space charge play an important role in distorting the electric field distribution. With the change of the space charge polarity, the position of the maximum electric field in the samples changed.

With the rapid development of smart grid and grid automation level, the intelligent requirements of power switch in the power system are also increasing. One of the main factors that lead to the secondary equipment failed is the transient electromagnetic interference in the process of switching operation. Due to the transient electromagnetic interference(EMI) caused by the operation of intelligent distribution switch, the secondary equipment may not work normally. Especially during the operation of intelligent distribution switch, the burning and reignition of the arc which caused by contacts generate transient electromagnetic field on the disconnected bus and radiate energy to the surrounding space. Therefore, it is of great theoretical and practical significance to research the electromagnetic interference of 10kV distribution switch in secondary control and protection device. In this paper, the finite-integral time-domain (FITD) method is used to calculate the interference of 10kV intelligent distribution switch when it is operating. The calculated results show that the space radiation and coupling interference caused by the arc in the 10kV distribution switch can be ignored because the intelligent distribution switch is a closed container.

As a mature renewable energy technology, wind power is an important form of renewable energy power generation. With the increasing installed capacity of wind turbines, the cluster of wind turbines has become more and more popular in china. Wind farms are usually located in open areas, and the wind turbines always stand out from the wind farm, which make the blade of the wind turbines are easily damaged by lightning. So lightning protection of blades is important for the safe operation of wind turbines. In this paper, a calculation model of multiple wind turbines was established in finite element method. Through simulating the electric field distribution of multiple wind turbines under thunder-cloud background and lightning leader, the effects of factors such as lightning leader positions and blade angles of wind turbines on the electric fields distribution of the turbine blades were investigated, and the lightning shielding effect of multiple wind turbines was analyzed. The results show that the variation of the lightning leader position and the blade angle of wind turbines both have influences on the electric field distribution of multiple wind turbines. When the lightning leader position varies in three typical positions, the electric field distributions on the surface of the turbine blades vary with the angle at different positions. When the lightning leader position was unchanged, the variation of wind turbine blade angle would also affect the electric field distribution on the surface of adjacent wind turbine blades. Furthermore, in clustered wind farms the angles of adjacent wind turbine blades are random, and the lightning shielding effect of multiple wind turbines was analyzed considering the influence of blade angle variation on the electric field distribution of adjacent wind turbine blades in this paper. The research results can be regarded as a basis for analyzing lightning strike characteristics of clustered wind farms.

Ribosome engineering has proven to be a practical method for increasing antibiotic production, and is extensively applied to strain improvement in antibiotic production and activation of silent genes in several prokaryotes. In this study, ribosome engineering was used to improve production of bioactive secondary metabolites produced by Pseudomonas protegens Pf-5. Rifampicin-resistant mutants that bear the H531N in the β-subunit of RNA polymerase showed improved antifungal activity and morphological changes. The production of several secondary metabolites in R55 mutant was significantly improved using high-performance liquid chromatography (HPLC) analysis. Two antibiotics with antifungal activity, 2, 4-diacetylphloroglucinol (Phl) and pyoluteorin (Plt), which may contribute to the improved antifungal activity of the R55 mutant, were identified by mass spectrometer (MS) analysis.

In order to develop an efficient system for deleting genomic segment in Agrobacterium tumefaciens to analyze gene functions and construct marker gene-free recombinant strains, a Cre recombinase expression plasmid was constructed by placing its encoding gene under the control of Ptet promoter and cloning into the plasmid replicable in both A. tumefaciens and E. coli. Triple recombineering was applied to efficiently construct integrative vectors which were used to introduce loxP sites and selection markers into the chromosome of A. tumefaciens. Cre recombinase could be properly induced by anhydrotetracycline in A. tumefaciens, which was revealed by the fact that kanamycin resistance gene flanked by two parallel loxP sites was excised from the genome of A. tumefaciens with virtually 100% efficiency. And what is more, an A. tumefaciens mutant carrying large-deletion (~85 kb) in genome was successfully constructed by Cre/loxP system. Here, we described the application of combination of Cre/loxP system and triple recombineering to efficiently excise genomic segment in A. tumefaciens, which also would facilitate efficient construction of multiple gene disruptions in A. tumefaciens.

The binary toxin ‘ Photorhabdus insect-related’ proteins (PirAB) produced by Photorhabdus luminescens have been reported to possess both injectable and oral activities against a range of insects. Here, PirAB-fusion protein was constructed by linking pirA and pirB genes with the flexible linker (Gly4Ser)3 DNA encoding sequence and then efficiently expressed in Escherichia coli . To better understand the role of PirAB toxin played in the process of invasion, its cytotoxicity against insect midgut CF-203 cells was investigated. Application of purified PirAB-fusion protein as well as PirA/PirB mixture caused loss of viability of CF-203 cells after 24 h incubation. CF-203 cells treated by PirAB-fusion protein displayed morphological changes typical of apoptosis, such as cell shrinkage, cell membrane blebbing, nuclear condensation and DNA fragmentation. Moreover, PirAB-fusion protein also exhibited injectable insecticidal activity against Spodoptera exigua larvae. The bodies of S. exigua fourth-instar larvae injected with PirAB-fusion protein turned completely black. Thus, we concluded that PirAB-fusion protein possessed similar biological activity (cytotoxicity and insecticidal activity) to PirA/PirB mixture, which would enable it to be used as an efficient agent for pest control.

Heterologous expression has been proven to be a valid strategy for elucidating the natural products produced by gene clusters uncovered by genome sequencing projects. Efforts have been made to efficiently clone gene clusters directly from genomic DNA and several approaches have been developed. Here, we present an alternative strategy based on the site-specific recombinase system Cre/loxP for direct cloning gene clusters. A type three secretion system (T3SS) gene cluster (~32 kb) from Photorhabdus luminescens TT01 and DNA fragment (~78 kb) containing the siderophore biosynthetic gene cluster from Agrobacterium tumefaciens C58 have been successfully cloned into pBeloBAC11 with “Cre/loxP plus BAC” strategy. Based on the fact that Cre/loxP system has successfully used for genomic engineering in a wide range of organisms, we believe that this strategy could be widely used for direct cloning of large DNA fragment.

Previous study revealed that the N-terminal region of PirB toxin from Photorhabdus luminescens showed 20.5% identity and 41.5% similarity to the domain I of Cry2A toxin of Bacillus thuringiensis. The encoding sequence of the domain I of Cry2Aa protein was replaced by the encoding gene of corresponding domain of PirB protein. Expression of pirB-cry2Aa chimeric gene in B. thuringiensis acrystalliferous strain Cry−B leads to the formation of crystals with irregular shape. Bioassay showed that PirB-Cry2Aa hybrid protein displayed toxicity against Spodoptera exigua and Helicoverpa armigera larvae. Our data implied that PirB protein might possess pore-forming activity and PirB-Cry2Aa hybrid protein could be used as biological control agent.