Helicoverpa armigera and Helicoverpa zea are major caterpillar pests of Old and New World agriculture, respectively. Both, particularly H. armigera, are extremely polyphagous, and H. armigera has ...developed resistance to many insecticides. Here we use comparative genomics, transcriptomics and resequencing to elucidate the genetic basis for their properties as pests.
We find that, prior to their divergence about 1.5 Mya, the H. armigera/H. zea lineage had accumulated up to more than 100 more members of specific detoxification and digestion gene families and more than 100 extra gustatory receptor genes, compared to other lepidopterans with narrower host ranges. The two genomes remain very similar in gene content and order, but H. armigera is more polymorphic overall, and H. zea has lost several detoxification genes, as well as about 50 gustatory receptor genes. It also lacks certain genes and alleles conferring insecticide resistance found in H. armigera. Non-synonymous sites in the expanded gene families above are rapidly diverging, both between paralogues and between orthologues in the two species. Whole genome transcriptomic analyses of H. armigera larvae show widely divergent responses to different host plants, including responses among many of the duplicated detoxification and digestion genes.
The extreme polyphagy of the two heliothines is associated with extensive amplification and neofunctionalisation of genes involved in host finding and use, coupled with versatile transcriptional responses on different hosts. H. armigera's invasion of the Americas in recent years means that hybridisation could generate populations that are both locally adapted and insecticide resistant.
This paper considers the problem of attitude tracking control for uncertain rigid spacecraft subject to control input magnitude and rate saturation (MRS). First, a smooth input MRS model is proposed. ...Then, a robust attitude tracking control scheme is designed based on the backstepping and finite-time disturbance observer techniques. Finally, the effectiveness of the control scheme derived here is illustrated by numerical simulations.
Several piezocone penetration test (CPTu)-based soil behaviour classification systems (SBCs) have been developed for standard sites, where clays, silt, and sand dominate. However, problems can occur ...when applying the SBCs to offshore sites, where the marine soils may be decomposed from rocks or mixed with artificial fills. This study evaluates the accuracy of six CPTu-based SBCs for marine soils at a site offshore Hong Kong based on 16 CPTu soundings with 25 367 data points by comparing them with composition-based SBCs from borehole records in the vicinity of each sounding. The soil types are determined from six common CPTu-based SBCs. The interpretation of CPTu data is first performed to generate soil type variables comparable to borehole data, followed by a cross-validation study. The soil classification performance of each SBC is quantified by the weighted kappa coefficient and the Kendall correlation coefficient between the soil types generated by the CPTu-based and composition-based SBCs. The classification accuracy for each soil type is also evaluated via the root mean squared error and the mean absolute error. The classified soil types from the CPTu data are associated with a median degree of consistency, indicating the need for combining CPTu-based and composition-based SBCs for marine soil classification.
The effects of Fusarium oxysporum f. sp. cucumerinum, the pathogen causing Fusarium wilt in cucumber and cinnamic acid, a principal autotoxic component in the root exudates of cucumber (Cucumis ...sativus L.), on plant growth, Photosynthesis and incidence of Fusarium wilt in cucumber were studied in order to elucidate the interaction of autotoxins and soil-borne pathogens in the soil sickness. F. oxysporum. f. sp. cucumerinum (FO) and cinnamic acid (CA) at 0.1 or 0.25 mM significantly decreased net photosynthetic rate, stomatal conductance and the quantum yield of Photosystem II photochemistry (ΦPSII), followed by a reduction of plant biomass production, but did not induce photoinhibition. Pretreatment with CA before inoculation with FO increased the effectiveness of FO, together with a slight photoinhibition. CA pretreatment significantly increased percentage of plants affected by Fusarium wilt, browning index of vascular bundle and Fusarium population in the nutrient solution. All these results indicate that CA enhanced Fusarium wilt by predisposing cucumber roots to infection by FO through a direct biochemical and physiological effect. It is likely that soil sickness results from an interaction of many factors.
In general, Mg alloys are difficult to process at low temperature (below 200 °C), due to the limited slip systems. High-temperature deformation easily results in the grain growth, which seriously ...restricts the improvement of mechanical properties. In this study, we report a subsequent low-temperature extrusion technology for ultra-fine grained (UFG) Mg–Zn–Ca–Mn alloys processed through equal channel angular pressing (ECAP), and successfully fabricate the extruded alloy with high yield strength (∼332.8 MPa) and superior ductility (∼17.9%) through grain refinement and texture modification. The initially fine-grained structure in the as-ECAPed alloy is beneficial to improving its low-temperature deformability, because the compatibility stress at grain boundaries can effectively promote the activation of the non-basal slip systems. Although the strength is dramatically increased, the alloy extruded at 100 °C exhibits the poor ductility, which can be ascribed to the dislocation accumulation behavior. With increasing extrusion temperature, the yield strength is remarkably increased at very small expense of ductility, because of the grain refinement, stacking faults, recovery of basal texture and fine secondary phase particles. The dislocations formed during the extrusion can be rapidly annihilated through a dynamic recrystallization process, which contributes to the improved ductility.
Display omitted
•Low-temperature extrusion leads to high strength and excellent ductility.•Ultra-fine grained structure improves low-temperature deformability.•Dislocation annihilation effectively hinders the premature fracture.
This paper addresses attitude-stabilizing control for rigid spacecraft with actuator magnitude and rate saturation (MRS). Firstly, a continuous dynamical system is introduced to model the actuator ...MRS. Rigorous analysis is given to demonstrate that the model’s output can always meet the MRS constraints if the control scheme applied to the model derived here is continuous. Then, by using the proposed MRS model and the homogeneity property, two attitude-stabilizing control laws are presented. The measurement of angular velocity is required in the implementation of the first control law, but this requirement is unnecessary in the second one. The local finite-time stability of the resulting closed-loop system is ensured by employing the Lyapunov approach. Finally, several simulation examples are presented to validate the efficiency of the proposed method.
•Uniformly distributed non-coherent nanoprecipitates appeared in FeCoNi (Al)HEAs after high-pressure solidification (HPS).•Short-range ordering structures and the double sluggish diffusion effect ...(DSDE) lead to the nanoprecipitates.•The volume fraction of grain boundary phases is decreased after HPS.•The maximum permeability (μm) increased prominently and the intrinsic coercivity decreased after HPS.
Display omitted
In this work, we investigated the microstructure and magnetic properties of FeCoNi (Al) high-entropy alloys (HEAs) prepared by high-pressure solidification (HPS). The results show that incoherent nanoprecipitates distributed in uniaxial grain uniformly, which significantly reduces the average magnetic anisotropy of the alloys. The maximum permeability (μm) of alloys increased prominently (i.e. from 47800 to 169000 in FeCoNi alloy and 78000–205000 in FeCoNiAl alloy) and the intrinsic coercivity decreased by 43% in FeCoNiAl alloy after HPS. Nanoprecipitates were related with the double sluggish diffusion effect (DSDE), which is caused by the coupling of high-entropy and high-pressure during solidification process. DSDE not only ensures the retention of short-range ordering (SRO) structures in the liquid metal, but also inhibits the SRO structures’ growth during the solidification process. These SRO structures provide structural conditions to the nanoprecipitates. The molecular dynamics simulation results provide support to the crucial role of DSDE on short-range ordering structures. HPS can effectively reduce the volume fraction of grain boundary precipitates also due to DSDE. Thus, DSDE exhibited the great significance to understand the microstructure of FeCoNi (Al) HEAs by HPS. The perspective also provides a paradigm to enhance the magnetic property of soft magnetic alloys significantly.
PDF
