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Parabronema skrjabini is one of the most harmful nematodes to camels and is responsible for economic losses in animal husbandry industry. There is an urgent need for in-depth studies of potential vectors of the nematode due to its scant regarding information. As previous studies indicated that flies may be the vectors of P. skrjabini, we captured flies in the main camel-producing areas of Inner Mongolia. After autopsy of the specimens of two species of horn flies, we observed the morphology of the suspected nematode larvae found in them. Internal transcribed spacer ribosomal-DNA gene sequences were considered the best candidate to confirm the species of the larvae found. Our results showed that the homology compared with P. skrjabini was 99.5% in GenBank. Subsequently, we preliminarily identified two species of horn flies through morphological observation and then sequenced the mitochondrial-DNA-gene cytochrome oxidase subunit I obtained from two species of horn flies, with 100 and 99.2% similarity to sequences deposited in GenBank, respectively. Thus, we identified Haematobia titillans and Haematobia irritans and provided evidence for their potential role as vectors of parabronemosis. Our study provides reference for future research on the life history of the nematode and the vectors of parabronemosis.
Finite difference method is an important methodology in the approximation of waves. In this paper, we will study two implicit finite difference schemes for the simulation of waves. They are the weighted alternating direction implicit (ADI) scheme and the locally one-dimensional (LOD) scheme. The approximation errors, stability conditions, and dispersion relations for both schemes are investigated. Our analysis shows that the LOD implicit scheme has less dispersion error than that of the ADI scheme. Moreover, the unconditional stability for both schemes with arbitrary spatial accuracy is established for the first time. In order to improve computational efficiency, numerical algorithms based on message passing interface (MPI) are implemented. Numerical examples of wave propagation in a three-layer model and a standard complex model are presented. Our analysis and comparisons show that both ADI and LOD schemes are able to efficiently and accurately simulate wave propagation in complex media.
Interatomic potentials are constructed for eight representative binary metal systems covering various structural combinations and thermodynamic characteristics. On the basis of the constructed interatomic potentials, molecular dynamics simulations reveal that the physical origin of metallic glass formation is the crystalline lattice collapsing while solute atoms are exceeding the critical value, thus determining two critical solid solubilities for the system. For a binary metal system, the composition range bounded by the two determined critical solid solubilities is therefore defined as its intrinsic glass-forming range, or quantitative glass-forming ability.
A metallic glass/porous tungsten bi-continuous phase composite was prepared by pressure infiltration whose quasi-static compressive stress and strain to macroscopic failure are much higher than those of all the previous tungsten-reinforced metallic glass matrix composites. It deserves to be mentioned that because of its high-yield strength and high elastic strain limit, metallic glass seems to be used as the reinforcement to strengthen the crystalline materials in the bi-continuous phase composite materials.
(Zr62Cu15.4Ni12.6) (x = 6–12) in situ glassy composites containing uniformly distributed Ta-rich particles were prepared by arc-melting and copper mould casting. The results show that addition of 6–10 at.% Ta to Zr62Cu15.4Ni12.6Al10 results in dissolution of 2.4 to 4.6 at.% Ta in the glassy matrix, which promotes glass-forming ability, and the remaining Ta precipitates out as body-centered cubic (BCC) Ta-rich particles dispersed on the glassy matrix. The critical diameters for the composites with 6, 8, and 10 at.% Ta are 7, 7, and 6 mm, respectively. At 12 at.% Ta addition, the glass-forming ability is dramatically reduced because of the precipitation of secondary dendritic Ta-rich particles and other nanocrystallites from melts during copper mould casting. Also, owing to the solid-liquid reaction during induction heating, some Ta-rich particles formed in the master alloys will redissolve into the glassy matrix, resulting in a smaller volume fraction of Ta-rich particles in the as-cast glassy rods than that of the corresponding ingots. The glassy matrix composites exhibit enhanced plastic strain of about 7.5 to 22.5% at room temperature. The optimum Ta content in the glassy alloys is determined to be 10 at.%, which corresponds to the highest ultimate stress of 2220 MPa and the largest plastic strain of 22.5%. The plastic strain increases with increasing volume fraction of in situ BCC Ta-rich particles. This is apparently ascribed to the impedance of Ta-rich particles to shear bands. Ta-rich particles seed the initiation of multiple shear bands and block the shear band propagation, leading to intensive multiplication and bifurcation of shear bands.
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