Community Structure and Diversity of Hymenopteran Parasitoids of Chromatomyia horticola (Diptera: Agromyzidae) in Different Habitats in Changchun, China.

The community structure and diversity of hymenopteran parasitoids of the agromyzid leafminer Chromatomyia horticola (Diptera: Agromyzidae) were studied in agricultural, urban, and natural habitats in Changchun, Northeast China. In agricultural habitats, a total of 3,380 individuals and 19 species were collected, and the dominant species were Diglyphus isaea (Walker) (Hymenoptera: Eulophidae) (71.15%) and Chrysocharis pentheus (Walker) (Hymenoptera: Eulophidae) (12.10%). In urban habitats, a total of 5,996 individuals and 21 species were collected. There were three dominant species, C. pentheus (26.68%), Chrysocharis phryne (Walker) (Hymenoptera: Eulophidae) (22.18%), and D. isaea (22.13%). In natural habitats, a total of 1,566 individuals and 26 species were collected. There were three dominant species, C. pentheus (30.52%), D. isaea (15.52%), and Pediobius metallicus (Nees) (Hymenoptera: Eulophidae) (12.26%). The diversity indices of the parasitoid community in urban and natural habitats were higher than that in agricultural habitats, and the richness index in natural habitats was higher than that in agricultural and urban habitats. These results suggest that there are differences in the community composition and dynamics of parasitoids in different habitats. Hymenopteran parasitoids of C. horticola are less abundant in natural habitats; however, species richness is greater, and can be used as a species reserve for biological control.

A new species of Hemiptarsenus Westwood (Hymenoptera, Eulophidae) from China, with a key to Chinese species.

A new species, Hemiptarsenus jilinus Tao, sp. nov., is described and illustrated. All the type specimens were reared from Chromatomyia horticola (Goureau) (Diptera: Agromyzidae), a leafminer attacking the plants Ixeris polycephala Cass. and Pterocypsela indica (L.) Shih, in Jilin Province, north-eastern China. A key to Chinese species of the genus is provided.

Effects of Substrates on the Production of Fruiting Bodies and the Bioactive Components by Different Cordyceps militaris Strains (Ascomycetes).

Cordyceps militaris is a type of food and medicinal species and is widely cultured in Asia. Substrate and strain are important factors for the production of fruiting bodies and bioactive components contents in fruiting bodies of C. militaris. This study aimed to select the excellent strains and suitable substrates by six strains of C. militaris cultivated on rice, wheat, and tussah (Antheraea pernyi) pupae. The results showed that the rice and wheat were suitable for fruiting body formation of strain CM3, with yields of 23.19 and 19.07 g per bottle, and biological efficiency of strain CM3 were 62.26% and 54.48%, respectively, which were significantly higher than other strains. Tussah pupae is suitable for fruiting body formation of strain CM9, with fruiting body length, yield, and biological efficiency of 5.57 cm, 6.80 g per each, and 291.70%, respectively, which were significantly higher than other strains. The content of adenosine in fruiting bodies of strain CM9 cultivated on tussah pupae was 2.62 mg g-1, followed by that of strain CM3 on rice of 2.51 mg g-1. The content of cordycepin in fruiting bodies of strain CM4 cultivated on wheat was 5.68 mg g-1, followed by that of strain CM9 on wheat of 5.41 mg g-1. To improve the product quality and the contents of bioactive components, C. militaris strains and substrates should both be considered, that is, different strains should be appropriate for different substrates.

Interstitial Occupancy by Extrinsic Alkali Cations in Perovskites and Its Impact on Ion Migration.

Recent success in achieving highly stable Rb-containing organolead halide perovskites has indicated the possibility of incorporating small monovalent cations, which cannot fit in the lead-halide cage with an appropriate tolerance factor, into the perovskite lattice while maintaining a pure stable "black" phase. In this study, through a combined experimental and theoretical investigation by density functional theory (DFT) calculations on the incorporation of extrinsic alkali cations (Rb+ , K+ , Na+ , and Li+ ) in perovskite materials, the size-dependent interstitial occupancy of these cations in the perovskite lattice is unambiguously revealed. Interestingly, DFT calculations predict the increased ion migration barriers in the lattice after the interstitial occupancy. To verify this prediction, ion migration behavior is characterized through hysteresis analysis of solar cells, electrical poling, temperature-dependent conductivity, and time-dependent photoluminescence measurements. The results collectively point to the suppression of ion migration after lattice interstitial occupancy by extrinsic alkali cations. The findings of this study provide new material design principles to manipulate the structural and ionic properties of multication perovskite materials.

Accurate and efficient band gap predictions of metal halide perovskites using the DFT-1/2 method: GW accuracy with DFT expense.

The outstanding optoelectronics and photovoltaic properties of metal halide perovskites, including high carrier motilities, low carrier recombination rates, and the tunable spectral absorption range are attributed to the unique electronic properties of these materials. While DFT provides reliable structures and stabilities of perovskites, it performs poorly in electronic structure prediction. The relativistic GW approximation has been demonstrated to be able to capture electronic structure accurately, but at an extremely high computational cost. Here we report efficient and accurate band gap calculations of halide metal perovskites by using the approximate quasiparticle DFT-1/2 method. Using AMX3 (A = CH3NH3, CH2NHCH2, Cs; M = Pb, Sn, X = I, Br, Cl) as demonstration, the influence of the crystal structure (cubic, tetragonal or orthorhombic), variation of ions (different A, M and X) and relativistic effects on the electronic structure are systematically studied and compared with experimental results. Our results show that the DFT-1/2 method yields accurate band gaps with the precision of the GW method with no more computational cost than standard DFT. This opens the possibility of accurate electronic structure prediction of sophisticated halide perovskite structures and new materials design for lead-free materials.

Secondary Electron Emission Materials for Transmission Dynodes in Novel Photomultipliers: A Review.

Secondary electron emission materials are reviewed with the aim of providing guidelines for the future development of novel transmission dynodes. Materials with reflection secondary electron yield higher than three and transmission secondary electron yield higher than one are tabulated for easy reference. Generations of transmission dynodes are listed in the order of the invention time with a special focus on the most recent atomic-layer-deposition synthesized transmission dynodes. Based on the knowledge gained from the survey of secondary election emission materials with high secondary electron yield, an outlook of possible improvements upon the state-of-the-art transmission dynodes is provided.

First-principles analysis of the C-N bond scission of methylamine on Mo-based model catalysts.

The C-N bond breaking of methylamine on clean, carbon (nitrogen, oxygen)-modified Mo(100) [denoted as Mo(100) and Mo(100)-C(N,O), respectively], Mo(2)C(100), MoN(100), and Pt(100) surfaces has been investigated by the first-principles density functional theory (DFT) calculations. The results show that the reaction barriers of the C-N bond breaking in CH(3)NH(2) on Mo(100)-C(N,O) are higher than that on clean Mo(100). The calculated energy barrier can be correlated linearly with the density of Mo 4d states at the Fermi level after the adsorption of CH(3)NH(2) for those surfaces. Moreover, the DFT results show that the subsurface atom, e.g., carbon, can reduce the reaction barrier. In addition, We noticed that the activation energies for the C-N bond breaking on Mo(2)C(100) and MoN(100) are similar to that on Pt(100), suggesting that the catalytic properties of the transition metal carbides and nitrides for C-N bond scission of CH(3)NH(2) might be very similar to the expensive Pt-group metals.

Effect of pre-covered oxygen on the dehydrogenation reactions over copper surface: a density functional theory study.

Dehydrogenation of five species including CH3OH, CH3O, H2COO, NH3, and H2O over clean and oxygen-modified copper surfaces has been investigated by the first-principle density functional calculations within the generalized gradient approximation. The reaction enthalpies and the activation energies have been calculated for 10 elementary steps corresponding to the direct and oxygen-assisted cleavage of X-H bonds (X = O, N, C). The DFT-GGA results showed that the pre-adsorbed oxygen always facilitates the dehydrogenation reaction by decreasing the reaction enthalpies and the activation energies. The obtained results are in general agreement with experimental observations.