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We have theoretically studied the hydrodesulphurisation (HDS) mechanism of thiophene and its hydrogenated derivatives over sulphided Co–Mo catalysts supported by four zeolites (ZSM-5, FAU, Beta, MCM-22) by a two-layer ONIOM (our Own N-layered Integrated molecular Orbital and molecular Mechanics) method. Due to low energy barriers, the thiophene can be hydrogenated to 2,3-dihydrothiophene (2,3-DHT), 2,5-dihydrothiophene (2,5-DHT) and tetrahydrothiophene (THT). Direct desulphurisation (DDS) and hydrogenolysis desulphurisation (HYD) pathways were investigated in detail. The calculated results show that in DDS mechanism of thiophene, the rate-determining step is the C–S bond cleavage. In HYD mechanisms of 2,5-DHT, 2,3-DHT and THT, the rate-determining step is hydrogen transfer on ZSM-5, FAU and Beta zeolites except MCM-22 zeolite. The HYD of 2,3-DHT and THT should occur by the stepwise pathway. But for the 2,5-DHT, the concerted pathway is probably more favourable than the stepwise pathway. The reduced density gradient (RDG), differential charge density (DCD), and local orbital locator (LOL) maps show that for all transition states (TSs), there are complicated van der Waals (VDW) and electrostatic interactions between the organic fragment and the catalytic centre. [ABSTRACT FROM AUTHOR]

Different from traditional phased array radar, frequency diverse array (FDA) radar uses a small frequency increment across the array elements; thus, the beampattern of FDA can be performed in both range and angle domains. Nevertheless, the transmit beampattern of conventional FDA is coupled in range and angle domains, which is not suitable for target detection. In this paper, we propose a multi-carrier FDA framework to generate the range-angle-decoupled beampattern. To focus the transmit energy at the desired position and suppress the interference at the undesired position, we then propose a beampattern synthesis approach based on Lagrange programming neural network, which can be implemented by hardware easily. Numerical simulation results demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Abstract The ordered mesoporous Ni/KIT-6 (KIT-6, an ordered mesoporous SiO 2) catalysts were prepared by impregnation method for carbon dioxide reforming of methane. The physicochemical properties of the prepared catalysts were characterized by H 2 -TPR, XRD, BET, and TEM. The research results show that the specific surface area, pore diameter, crystal size of Ni species, and catalytic performance of the Ni/KIT-6 catalysts are obviously affected by the Ni content. Increasing Ni content results in the increment of the crystal size of Ni species, while the dispersion of Ni species shows the opposite trend. The specific surface area and pore size of the Ni/KIT-6 catalyst with the Ni loading of 3 wt% were 493.3 m2 g−1 and 6.22 nm, respectively. Besides, the Ni species are highly dispersed on the surface of KIT-6 support. Thereby, it exhibits the superior catalytic performance of carbon dioxide reforming of methane to syngas (CO and H 2). At atmospheric pressure, the CO 2 and CH 4 conversions for each catalyst following the order: NK3 ≈ NK4 > NK5 > NK2 > NK1 > bulk Ni. When the reaction temperature is 600 °C, the conversions of CH 4 and CO 2 of the NK3 catalyst are 65.1% and 37.0%, respectively. Meanwhile, it also shows excellent stability. Highlights • The structure of KIT-6 promoted high dispersion of nickel species. • Ni/KIT-6 catalysts maintain ordered developed mesoporous structure and high specific surface area. • Developed mesoporous structure and highly dispersed Ni are more favorable for carbon dioxide reforming of methane. • Ni/KIT-6 catalyst has superior carbon dioxide reforming of methane performance. [ABSTRACT FROM AUTHOR]

CeO 2 nanorods and nanocubes, which were used as supports to Pd (3.0 wt.%)/CeO 2 catalysts, which were prepared by hydrothermal method. TEM, HRTEM, XRD, and H 2 -TPD were used to study the physic-chemical properties of the Pd/CeO 2 catalysts. The Pd/CeO 2 catalysts were applied to investigate the vapor phase benzene catalytic hydrogenation reaction under atmospheric pressure at the temperature of 100–200 °C. Results show that the Pd/CeO 2 catalysts exhibit morphology-dependent catalytic activity. The Pd/CeO 2 nanorod catalyst (PC100) has a superior vapor phase benzene catalytic hydrogenation performance. The benzene catalytic hydrogenation conversion and cyclohexane selectivity are 96.4% and 100% at 200 °C, respectively. [ABSTRACT FROM AUTHOR]

There are difficulties in tracking host use by pests and mating between pests exposed to Bt selection and non-Bt hosts across landscapes. We used stable isotope analyses of sampled bulked and individual Helicoverpa armigera moths across the major cotton producing area of northwestern China to estimate contributions made by the predominant crops, Bt cotton (C3) and non-Bt corn (C4; a putative refuge). 'Effective mating' that between moths originating from cotton and the putative refuge (corn) was estimated using the isotope signal of sampled females and their spermatophores. Across the 4 years (2012–2015), substantially fewer moths were produced from putative refuges versus Bt cotton, and an asynchrony in population phenology occurred in moths originating from both sources at certain critical times. The proportion of C4 moths in bulked samples, and as individual females, was the highest during spring and autumn. Furthermore, the percentage of C4 moths originating from corn was positively correlated with its percentage in the landscape. However, mating was biased toward pairs of moths originating from the same host type. The proportion of 'effective mating' ranged from 24 to 45%, and was greatest during spring and autumn correspondingly. Our study suggests that the refuge role of corn might be overestimated in northwestern China because asynchrony of population phenology and a bias in mating toward pairs of moths that originate from host type are not being considered. Therefore, increasing the diversity of refuge crops temporally would better facilitate resistance management instead of relying on a single refuge host. [ABSTRACT FROM AUTHOR]

Extensive unofficial planting of Bt cotton expressing Cry1Ac toxin has occured for the past two decades in northwestern China, and no mandatory refuge policy has been adopted. The status of Cry1Ac susceptibility of Helicoverpa armigera in this region has not been routinely monitored, nor has the susceptibility to Cry2Ab cotton which has not been released in China. The susceptibility of H. armigera populations to both toxins was assessed in 2014 and 2015 in two contrasting cotton farming systems across the region. Over the 2 years, the response to Cry1Ac of the nine H. armigera field populations sampled ranged from 3.16 to 16.94 μg ml−1 for LC50 and 0.013 to 0.741 μg ml−1 for IC50, and the baseline susceptibility of these strains to Cry2Ab ranged from 3.43 to 19.05 μg ml−1 for LC50 and 0.16 to 3.81 μg ml−1 for IC50. There was no significant difference in susceptibility to either Cry1Ac or Cry2Ab between small-holder and broad-acre farming. The susceptibility to Cry1Ac toxin in northwestern China is higher than that in northern China, while there was no difference for Cry2Ab between northwestern China and northern China. With high levels of adoption of Bt cotton and relatively limited natural refuge for H. armigera, it is important to consider resistance management measures for Bt cotton in northwestern China. [ABSTRACT FROM AUTHOR]