Search

To improve the wear resistance of CoCrFeNi high-entropy alloys (HEAs) for a wider range of industrial applications, the alloying strategy was applied to CoCrFeNi HEA by doping Mo element in various ratios, and CoCrFeNiMox (x = 0, 0.2, 0.5, and 1.0) HEA deposits were fabricated by cold spray. The microstructure evolution, mechanical properties, and tribological properties of cold-sprayed CoCrFeNiMox HEA deposits were systematically investigated. The results showed that Mo0, Mo0.2, and Mo0.5 deposits have a face-centered-cubic (FCC) single structure, while Mo1.0 deposit was composed of FCC matrix and hard brittle phases. The doping of Mo element into CoCrFeNi HEA deposits significantly increased the hardness due to the enhanced solid solution strengthening and precipitation strengthening. As a result, the anti-wear properties of Mo-doped CoCrFeNi HEA deposits were gradually improved with the increase in Mo ratios. To be specific, the Mo1.0 deposit exhibited the lowest specific wear rate of 5.1 × 10−5 mm3/N·m, which was reduced by 94.9% in comparison to the Mo0 deposit. Overall, the current study proposes a new strategy to manipulate the mechanical properties of cold-sprayed HEA deposits by alloying.

High chromium superalloys have good overall mechanical properties and are widely used in critical hot-end components. The current manufacturing process still faces the problem of low forming efficiency. Extreme high-speed laser metal deposition (EHLMD) is a new and efficient additive manufacturing technology that can quickly and directly shape the direct forming of difficult-to-process materials. However, EHLMD still possesses some inter-layer defects in EHLMD alloy due to its excessively fast scanning speed, implying that there is potential for further improvement in its properties. Hot isostatic pressing (HIP) as a post-heat treatment is primarily used for the removal of defects in additive manufacturing components. In this study, the defects, microstructure, and properties of the EHLMD K648 superalloy using Micro-CT, XRD, SEM and TEM under HIP treatment were investigated. The results show that the porosity of the HIP EHLMD K648 superalloy decreased, and slender needle-shaped α-Cr phase, γ′ phase and coarse M6C carbides were precipitated. The tensile strength of the HIP EHLMD K648 superalloy increased by about 240 MPa. However, its plasticity was reduced. To further improve the plasticity of the HIP EHLMD K648 superalloy, subsequent heat treatment was carried out. The outcomes of this study are expected to promote the manufacturing of high-quality chromium superalloys and the development of EHLMD technology.

Arthropod-borne rickettsioses comprise a wide variety of subtypes that are endemic in Cambodia, but there remains very little data on the geographic distribution of the pathogens or their vectors. Surveys were conducted in Koh Kong and Preah Sihanouk Provinces between September 2017 and June 2018 to collect ectoparasites from peridomestic animals and the environment using dragging and flagging methods. Collected ectoparasites were sorted and identified morphologically, then pooled by species, host, and location for molecular detection using Rickettsia genus- and species-specific qPCR and/or multilocus sequence typing (MLST) assays. A total of 14,254 ectoparasites were collected including seven new locality records. Rickettsia species were detected in 35.5% (174/505) of the pools screened representing 3,149 randomly selected ectoparasites from the total collected. Rickettsia asembonensis was detected in 89.6% (147/164) of Rickettsia-positive flea pools and 3.6% (6/164) of the flea pools were positive for both R. asembonensis and Rickettsia felis. Candidatus Rickettsia senegalensis from Ctenocephalides orientis fleas and Rickettsia sp. close to Rickettsia japonica and Rickettsia heilongjiangensis from Haemaphysalis ticks were identified by MLST. This appears to be the first report of these new ectoparasite records and rickettsial species in southern Cambodia, suggesting a potential health risk to military and civilians in this region. Author summary: Rickettsiae are Gram-negative bacteria that cause acute undifferentiated febrile illness in humans. These pathogens are associated with arthropods and primarily transmitted by ectoparasites such as ticks, fleas, and mites. In Cambodia, rickettsial diseases have been documented in local patients, travelers and military personnel. However, the lack of entomological studies and awareness of these diseases hindered our comprehensive understanding of these pathogens and their arthropod vectors. Our manuscript provides a description of ectoparasite diversity and sheds light on their potential role in rickettsial disease transmission. Through molecular techniques, we uncover the prevalence and diversity of Rickettsia species in ectoparasites collected from various animal hosts in Koh Kong and Preah Sihanouk province. Rickettsia asembonensis, Rickettsia felis, and Candidatus Rickettsia senegalensis were all identified from Ctenocephalides orientis fleas, while Rickettsia species closely related to Rickettsia japonica, Rickettsia heilongjiangensis, and Rickettsia raoultii were found from Haemaphysalis ticks. Additionally, Rickettsia were also detected in Heterodoxus spiniger lice and Laelapidae mites, although we were unable to characterize the species. Insights into this pathogen-vector-host interface will better inform healthcare professionals, leading to more accurate diagnoses and increased awareness for better management of these diseases. [ABSTRACT FROM AUTHOR]

ABSTRACT Artificial breeding of mantis shrimp Oratosquilla oratoria, using the ecological breeding in earthen pond (EBEP) method, has been carrying out from 2019, and the produced larvae have always been used for supportive breeding programs in Bohai Bay. To assess the degree of fidelity of enhancement programs used an EBEP method to native genetic pools, genetic diversity at 10 microsatellite loci was analyzed in three hatchery offspring populations, their wild parent stocks, and their wild contemporaneous offspring. Significant decrease in the almost genetic diversity parameters and highly significant differences in shannon's information index (decreasing by 22.54%–40.97%) and allelic richness (33.80%–46.87%) were observed between in hatchery populations. This further created relatively more genetic differentiation between the hatchery and wild population, as the pairwise Fst values and genetic distances showed. The mean pairwise relatedness coefficients showed higher values within hatchery populations and lower values within wild populations. Hatchery populations contained the fewest full‐sib families and offspring were extremely distributed in 10–11 full‐sib groups in each hatchery population. The relatively small number of actual spawning females and large variance in parental contribution to the next generation possibly causes allele reduction in the hatchery population, which in turn leads to a decrease in allelic diversity and an increase in genetic similarities among individuals. Promoting synchrony of ovarian development in females, providing good conditions for incubation and larvae culture and balancing the contributions of parents will be important in future breeding propagation. [ABSTRACT FROM AUTHOR]