[en] We present a molecular dynamics simulation within the framework of empirical tight-binding potential on the liquid structure of Au under different pressures during the rapid cooling process. The pair correlation function (PCF) and the pair analysis (PA) technique are used to reveal the structural characteristics of liquid Au under normal and high pressures. The split of the second peak of g(r) is associated with the glass transition at the cooling rate of 2.06x10¹³ K/s under different pressures. The nearest distance is shortened under high pressures. High-pressure is in favor of FCC-type and BCC-type atomic clusters. The number of icosahedral structures increases in the high temperature region as pressure increase, while high-pressure is not preferable for icosahedra at low temperature. With the increase of the pressure, the possibility that the system forms crystalline structure is enhanced. The influence of a higher pressure on the microstructure of liquid metal is much clearer than that of a lower pressure

[en] The paper discusses the responses of eutectic silicon and eutectic cells in Al–10Si alloy upon inoculation with an Al–10Si–2Fe master alloy. The further inoculation hardly destroys the modification effect of Sr but significantly refines the eutectic cells in Sr-modified samples, while in unmodified samples, it stimulates the occurrences of polyhedral silicon particles and divorced eutectic. Thermal analysis, scanning electron microscopy, (high-resolution) transmission electron microscopy and scanning and transmission electron microscopy have been used to elucidate the underlying mechanism. A cluster-assisted nucleation mechanism responsible for the enhanced nucleation of silicon phase upon inoculation is proposed. Icosahedral (AlFeSi) clusters are speculated to evolve from the added Al–10Si–2Fe master alloy in Al–10Si melt, around which aggregations of silicon atoms form. Through a series of structural evolutions, these clusters transform into precursors of a silicon crystal. The subsequent formation of silicon particles is achieved by the agglomerations and attachments of these precursors and individual silicon atoms. This hypothesis is further consolidated by the increased characteristic temperatures of eutectic and the anomalous appearance of a high density of nanoscale particles, as well as the abnormal disappearance of Sr-induced twins in further inoculated silicon particles. The increased characteristic temperatures are strong indications of the enhanced nucleation of the silicon phase. The high density of nanoscale particles with an indeterminate crystal structure are the survivors of these precursors. In an Sr-modified and further inoculated sample, the formation of Sr-induced twins is consequently inhibited due to the participation of these precursors during the growth of silicon particles. Furthermore, based on the proposed nucleation mechanism, the dependence of eutectic cell size on Sr level is elucidated in detail

[en] Objective: To screen radiosensitive lipid metabolites in rat plasma and analyze their metabolic pathways in order to provide scientific basis for radiation damage biomarker. Methods: The whole body irradiation of ⁶⁰Co γ rays was performed to rats with different doses of 0, 1, 3 and 5 Gy. The changes of lipids in plasma were detected by untargeted lipidomics method based on liquid chromatography coupled mass spectrometry. Results: Twenty plasma lipids were identified as the potential radiosensitive biomarkers at 7 days after irradiation, including 13 over-expressed lipids and 7 down-expressed lipids, where 12 lipids well responded to radiation doses. Conclusions: Lipid metabolites in rat plasma are significantly changed after exposure to γ rays, and the metabolic pathways of sphingolipid, glycerophospholipid and glycosylphosphatidylinositol (GPI) are significantly enriched. (authors)

[en] Objective: To explore the influences of the final concentration and adding time of Cytochalasin-B (Cyt-B) on radiation-induced nucleoplasmic bridges (NPB) in cytokinesis-block assay. Methods: Human peripheral blood samples were divided into 5 final concentration groups (group 2, 4, 6, 8, 10 μg/ml) according to different final concentrations of Cyt-B. Moreover, blood samples were divided into 4 adding time groups (group 0, 28, 40, 44 h) according to different adding times of Cyt-B. Blood samples were irradiated with 0 (sham irradiation) and 2 Gy ⁶⁰Co -rays in vitro, at a dose rate of 1 Gy/min. A cytokinesis-block assay was carried out to prepare NPB samples. The percentages of mononucleated, binucleated and multinucleated cells, as well as the frequencies of NPB and micronucleus (MN) in binucleated cells were analyzed using an optical microscope. Results: Nuclear division index (NDI) and the percentages of binucleated cells increased with increased concentration of Cyt-B, and decreased with delayed adding time of Cyt-B (except group 0 h) in both final concentration groups and adding time groups. After exposed to 2 Gy, NPB frequencies were no significant difference (except group 0 h). MN frequencies had the trend of decreased with the increased concentration of Cyt-B, but no significant difference with adding time of Cyt-B. Conclusions: In cytokinesis-block assay, different final concentration and adding time of Cyt-B may induce to the variation of NPB frequencies, but there was no significant difference. Appropriate increased final concentration or ahead adding time of Cyt-B can increase the percentage of binucleated cells that help to improve the efficiency of analysis. (authors)

[en] Objective: To study the effects of sex, age, length of service, type of work and annual effective radiation dose on nucleoplasmic bridge (NPB) in the peripheral blood lymphocytes of radiation workers. Methods: The peripheral blood samples of 100 radiation workers in Henan province were collected and the NPB in peripheral blood lymphocytes were measured by CBMN assay. The frequencies of NPB formation and NPB-containing cells were calculated, and the effects of various factors on NPB incidence were analyzed statistically. Results: The NPB frequency in radiation workers was higher than that in healthy people (Z = -8.123, P < 0.01). Except for sex, the factors of age, length of service, type of work and annual effective dose had significant influences on NPB (x² = 7.202-45.571, P < 0.05). Conclusions: NPB reflects the effect of low-dose long-term chronic irradiation on the occupational radiation workers. (authors)

[en] The resistivity behavior of undercooled liquid Cu-Ni and Cu-Co alloys had been studied in the contactless method, to probe the structure transition in undercooled melts during the cooling process. Over the entire concentration range, linear behavior of resistivity with temperature was obtained in liquid and undercooled liquid Cu-Ni system. It implied that the formation of icosahedral order might not influence the electron scattering in undercooled liquid Cu-Ni alloys. Similar results were obtained in Cu-Co system in the vicinity of liquidus temperature. A turning point was obvious in temperature coefficient of resistivity for undercooled liquid Cu-Co alloys around the bimodal line, which was interpreted to be responsible for metastable liquid-liquid phase separation. During liquid phase separation process, resistivity decreased and the temperature coefficient of resistivity was larger than that of homogeneous melts. In combination with transmission electron microscopy and scanning electron microscope studies on the as-solidified microstructure, this was interpreted as the formation of egg-type structure and concentration change in Cu-rich and Co-rich phases. The mechanism controlling the separation and droplets motion was also discussed in undercooled liquid Cu-Co system.

[en] Objective: To screen the indicators of retrospective dose estimation, based on 5 cytogenetic methods to assess the victim followed-up at 4 year after ¹⁹²Ir radiation accident in Nanjing. Methods: The chromosome aberration (dic + r) assay, cytokinesis block micronucleus (MN) and nucleoplasmic bridge (NPB) assay, fluorescence;in situ hybridization (FISH)-based and G banding-based translocation analysis were used to retrospective biological dose estimation. Results: The estimated doses of FISH-based and G banding -based analysis were 1.45 and 1.21 Gy respectively, which was similar to the biological dose estimated short time after the accident. However, the estimated doses by chromosome aberration, micronucleus and nucleoplasmic bridge method were 0.56, 0.45 and 0.41 Gy respectively, which were lower than the corresponding biodose. Correction factors were used to adjust the biodose. Conclusions: In the 4th years after exposure, the estimated biological doses by FISH-based and G banding-based translocation were consistent with the biodose. Therefore, the two methods were suitable for retrospective dose estimation, while correction factors should be considered in chromosome aberration method for retrospective dose estimation. (authors)

[en] Highlights: • The addition of 0.5 wt% Ni–32.5 wt% Si master alloy triggers multi-step nucleation of silicon in various Al–Si alloys. • The aggregation of pre-nucleation clusters changes the silicon growth by suppressing the twin plane re-entrant mechanism. • Pre-nucleation clusters manifest themselves by nano-particles with rhombohedral (9R) and hexagonal (2H) stacking sequences. Multi-step nucleation catalyzed by a Ni–Si master alloy in Al–Si liquids was investigated. Instead of enhancing heterogeneous nucleation, the master alloy triggers pre-nucleation clusters before initiating stable phase nucleation. The pre-nucleation clusters manifest themselves by a high number density of nano-sized silicon particles with rhombohedral (9R, ABCBCACAB…) and hexagonal (2H, ABAB…) stacking sequences, which have higher energies than diamond-cubic phase. Thermal analysis in Al–Si alloys with different Si concentration and inoculation time shows the effect of pre-nucleation clusters varying with the amount of local ordering (NiSi) clusters. In addition, the growth of silicon crystal is changed due to the presence of pre-nucleation clusters by suppressing the twin plane re-entrant mechanism.

[en] Using viscometer, densitometer, magnetic susceptibility device, DSC and X-ray diffractometer for high temperature (XRD), the Pb melt has been investigated between 800-1200 K. Anomalous changes in the physical properties were found near the same temperature. X-ray diffraction shows that the size of clusters in the low temperature zone is much larger than that in the high temperature zone. It is presumed that some solid-like structure occurred at the anomalous point of the physical properties during the cooling process

[en] Highlight• The addition of 0.5wt.% Sb with a holding time over 60 min leads to the disappearance of twin and the formation of high number-density Al-rich nano-particles in eutectic Si, which act as nucleation precursors and promote the eutectic nucleation in Al–10Si alloy; • A mechanism of precursor nucleation and microstructure transition is proposed, based on the formation of high number-density Al-rich nano-particles; • The existence of AlSb clusters in the Al–10Si–0.5Sb melts is eliminated, while Sb–Si repulsive force and Sb–Sb segregation lead to aggregation of Si atoms and precursors, respectively. The mechanism of refinement of eutectic Si with Sb additions in an Al–10 wt.% Si alloy is studied. The increased holding time designates a transition of the eutectic nucleation temperature from a decreased value to an increased one, accompanied by a morphological transformation of eutectic Si from lamellar to a shorter, rod-like shape. By ab initio molecular dynamics simulation, the chemical short-range order of − 0.002 demonstrates weak affinity in the Al–Sb pair, which does not favor the existence of AlSb clusters in the melts. Sb–Sb segregation and the Sb–Si repulsive force are revealed, which promote the formation of Al-enriched precursors and the accumulation of Si atoms adjacent to precursors, inducing precursor nucleation. Continuous attachment of precursors and individual Si atoms during Si growth results in the high number-density nano-particles and suppresses the formation of twin grains within eutectic Si.