Search

Inert matrix fuel (IMF) can effectively burn hazardous nuclides (such as Pu and minor actinides) as transmutation targets in reactors, making it an attractive option for nuclear waste management. IMF is a dispersion type of fuel that diffuses fissile phase, PuO2, in a neutron-transparent inert matrix (IM). MgO-Nd2Zr2O7 (M-NZO) composite ceramic is a potential IM that can replace UO2 in (U, Pu)O2 mixed oxide fuel (MOX) and to produce IMF by dispersing PuO2 in it. In this work, MgO, Nd2O3, ZrO2 powders were chosen as the raw materials, and series of ωM-(1-ω)NZO (ω=0.3, 0.4, 0.5, 0.6, 0.7 within mass percent) composite ceramics were prepared by one-step method at 1 500 ℃ for 24 h. Based on the analysis of phase composition and morphology, the thermophysical properties such as thermal conductivity and the coefficient of thermal expansion (CTE) for as-prepared M-NZO composite ceramics were systemically investigated. It is indicated that the as-prepared M-NZO composite ceramics show the remarkable densification and the mass fractions of MgO and Nd2Zr2O7 phases are almost the same as the designed nominal chemical composition. The average grain size of MgO phase and Nd2Zr2O7 phase is about 0.75 μm and 0.70 μm, respectively. The thermophysical properties results show that the thermal conductivity of all as-prepared M-NZO composite ceramics is 2.1-3.8 times that of UO2 ceramics at 1 400 ℃, suggesting the excellent thermal conductivity. And the thermal conductivity of M-NZO composite ceramics prepared by one-step method is higher than that of M-NZO composite ceramics fabricated by two-step method in the literatures within the tested temperature range, and the highest difference value is about 2 W·m-1·K-1 at high temperature (800 ℃). In terms of thermal expansion, the CTE value of as-prepared M-NZO composite ceramics ranges from 12.3×10-6-14.1×10-6/K and is comparable to that of UO2 ceramics. In addition, an incremental quantity of the thermal conductivity and CTE for ωM-(1-ω)NZO composite ceramics will merge with increasing MgO content. Combining the minimum thermal conductivity results for M-NZO composite materials, 0.5M-0.5NZO is the optimal sample composition, in which the mass percent of MgO in the composites stays the same as that of Nd2Zr2O7. In conclusion, M-NZO composite ceramics prepared in this work exhibits good thermal conductivity and stable thermal expansion property. And these thermal physical properties of M-NZO composite ceramics are superior to that of traditional UO2 ceramics. It is suggested that M-NZO composite ceramics can meet the thermal physical performances of IMF.

Single gamete cell sequencing together with long-read sequencing can reliably produce chromosome-level phased genomes. In this study, we employed PacBio HiFi and Hi-C sequencing on a male Landrace pig, coupled with single-sperm sequencing of its 102 sperm cells. A haplotype assembly method was developed based on long-read sequencing and sperm-phased markers. The chromosome-level phased assembly showed higher phasing accuracy than methods that rely only on HiFi reads. The use of single-sperm sequencing data enabled the construction of a genetic map, successfully mapping the sperm motility trait to a specific region on chromosome 1 (105.40–110.70 Mb). Furthermore, with the assistance of Y chromosome-bearing sperm data, 26.16 Mb Y chromosome sequences were assembled. We report a reliable approach for assembling chromosome-level phased genomes and reveal the potential of sperm population in basic biology research and sperm phenotype research. An improved pig genome assembly is reported, using single sperm sequencing to reconstruct chromosome haplotypes, and with improved Y chromosome sequence. [ABSTRACT FROM AUTHOR]

Few studies have been done on the interspecific relationship between fishes species, an important part of mangrove wetlands. In 2022-2023, a sampling survey was conducted on the mangrove tidal gully fish in the estuary area of Haishan Town, Raoping County, Guangdong Province in spring, summer, autumn and winter, and the composition of fish species in the mangrove wetland was studied. The aim of this study was tried to elucidate the response relationship between the distribution and interspecific relationships of wetland fish and the effects of environmental factors by calculating the spatiotemporal niche width and interspecific overlap values. The results showed that a total of 14 species belonging to 12 families and 6 orders were identified, including 6 dominant species (IRI≥500), 3 common species (500>IRI≥100), 2 rare species (100>IRI≥10) and 3 occasional species (IRI<10). The spatiotemporal niche width of the fish in mangrove tidal gullies ranged from 0.000 to 2.428, with a large variation range, including 1 species of wide niche species (Bij≥2.0) (Oreochromis niloticus), 2 species of medium niche species (1.0≤Bij<2.0)(Odontamblyopus rubicundus and Bostrichthys sinensis), and the remaining 11 species narrow niche species (00.6) were highly significant overlapped (0.6), accounting for 47% of the total logs, and 21 pairs (0.3< overlap value <0.6) were significant overlapped, accounting for 23% of the total logs, and the two pairs accounted for 70% of the total logs. The highest spatiotemporal niche overlap values were found in Siganus oramin and Periophthalmus cantnensis (up to 0.956), while the lowest non-overlap values were included in O. niloticus and Platycephalus indicus, B. sinensis and P. indicus, and Paraplagusia bilineata and P. indicus, all with the value of 0. BIOENV analysis showed that the most suitable combinations of environmental factors for fish abundance in the study area were water temperature, salinity, pH and chlorophyll a content, which the correlation coefficient is 0.475, and the RELATE test results were significant (R=0.461, P<0.05), indicating that these four environmental factors were important in affecting fish distribution. In general, the spatiotemporal niche of fish in the mangrove wetland of Raoping Haishan town was dominated by narrow niche species, and the spatiotemporal niche overlap between different fish species was significant and meaningful. The water temperature, salinity, pH and chlorophyll a content of the water body were important environmental factors affecting the distribution of fish in the wetland in the forest area. [ABSTRACT FROM AUTHOR]