Recovery of FLiBe from ThF4-FLiBe salt using precipitation-distillation coupled method.

The low-pressure distillation of FLiBe salt containing ThF4 was carried out at 1223 K and <10 Pa using thermogravimetric equipment. The weight loss curve indicated a rapid distillation stage at the beginning of distillation, followed by a slow stage. The composition and structure analyses showed that the rapid distillation process originated from the evaporation of LiF and BeF2, while the slow distillation process was mainly attributed to the evaporation of ThF4 and LiF complexes. Precipitation-distillation coupled method was employed for the recovery of FLiBe carrier salt. XRD analysis indicated that ThO2 was formed and remained in the residue with the addition of BeO. Our results showed that the combination of precipitation and distillation treatment was an effective way to recover carrier salt.

Study on the Thermal Stability of the Na2UF8 Complex in the Argon Atmosphere.

The Na2UF8 complex is an important intermediate compound in the purification of UF6 by the adsorption-desorption process during fluoride volatility of the spent nuclear fuel, and its decomposition is seriously affected by temperature and atmosphere. In this study, the thermal stability of Na2UF8 in the argon atmosphere was investigated by the in situ Raman spectroscopy. The decomposition products of Na2UF8 at different temperatures were systematically determined by X-ray diffraction spectroscopy and X-ray absorption fine structure spectroscopy. The results indicated that Na2UF8 on the NaF sorbent was stable under 300 °C in the argon atmosphere, and it started to decompose into UF6 and NaF rapidly when the temperature was above 300 °C. Meanwhile, a small amount of Na2UF8 was converted to Na3UF7, and it was stable in the temperature range from 350 to 450 °C. The decomposition mechanism of the Na2UF8 and the formation mechanism of Na3UF7 on the NaF sorbent were speculated according to the experimental results.

Investigation of the local structure of molten ThF4-LiF and ThF4-LiF-BeF2 mixtures by high-temperature X-ray absorption spectroscopy and molecular-dynamics simulation.

The microscopic structures of ThF4-LiF and ThF4-LiF-BeF2 molten salts have been systematically investigated by in situ high-temperature X-ray absorption fine-structure (XAFS) spectroscopy combined with molecular-dynamics (MD) simulations. The results reveal that the local structure of thorium ions was much more disordered in the molten state of the ThF4-LiF-BeF2 salt than that in ThF4-LiF, implying that the Th and F ions were exchanged more frequently in the presence of Be ions. The structures of medium-range-ordered coordination shells (such as Th-F2nd and Th-Th) have been emphasized by experimental and theoretical XAFS analysis, and they play a significant role in transport properties. Using MD simulations, the bonding properties in the molten ThF4-LiF and ThF4-LiF-BeF2 mixtures were evaluated, confirming the above conclusion. This research is, to the best of our knowledge, the first systematic study on the ThF4-LiF-BeF2 molten salt via quantitative in situ XAFS analysis and MD simulations.

First-principle atomistic thermodynamic study on the early-stage corrosion of NiCr alloy under fluoride salt environment.

The atomic morphology change in the NiCr alloy surface induced by fluorine-chemisorption was investigated by the ab initio atomistic thermodynamic method to elucidate early-stage corrosion processes of nickel-based alloys in strong oxidizing environment. The surface phase diagrams of Cr-doped Ni(111) surface as a function of fluorine chemical potential were obtained to track the surface structures that are most likely to be fostered in various temperature and pressure conditions. The adsorption of fluorine on the top site of Cr in the alloy surface was the most energetically favorable one. With increasing fluorine chemical potential, more fluorine atoms started to agglomerate in the trapping sink of Cr. Fluorine-fluorine repulsion interaction coupled with strong F-Cr bonding could facilitate a decided morphology modification of the metal substrate. Moreover, an insight into the desorption pathways for potential species revealed that in the presence of fluorine, the dissociation of Cr predominantly stems from the relatively easy desorption in the form of CrF2/CrF3 molecules from the non-passivated Ni-based alloy surface.

First-Principles Study of Vacancies in Ti3SiC2 and Ti3AlC2.

MAX phase materials have attracted increased attention due to their unique combination of ceramic and metallic properties. In this study, the properties of vacancies in Ti3AlC2 and Ti3SiC2, which are two of the most widely studied MAX phases, were investigated using first-principles calculations. Our calculations indicate that the stabilities of vacancies in Ti3SiC2 and Ti3AlC2 differ greatly from those previously reported for Cr2AlC. The order of the formation energies of vacancies is VTi(a) > VTi(b) > VC > VA for both Ti3SiC2 and Ti3AlC2. Although the diffusion barriers for Ti3SiC2 and Ti3AlC2 are similar (~0.95 eV), the properties of their vacancies are significantly different. Our results show that the vacancy-vacancy interaction is attractive in Ti3AlC2 but repulsive in Ti3SiC2. The introduction of VTi and VC vacancies results in the lattice constant c along the [0001] direction increasing for both Ti3SiC2 and Ti3AlC2. In contrast, the lattice constant c decreases significantly when VA are introduced. The different effect of VA on the lattice constants is explained by enhanced interactions of nearby Ti layers.

Performance of EuroSCORE II and SinoSCORE in Chinese patients undergoing coronary artery bypass grafting.

OBJECTIVES: The European System for Cardiac Operative Risk Evaluation II (EuroSCORE II) was developed to update EuroSCORE and incorporated refinement and modification of several risk factors. SinoSCORE was designed by Chinese scholars based on 9839 patients who underwent coronary artery bypass grafting (CABG) at 43 participating institutions. This study was designed to validate the EuroSCORE II and SinoSCORE in Chinese patients undergoing CABG and to compare their performance overall and per subgroup. METHODS: A total of 4507 adult receiving CABG at our institution between January 2010 and April 2014 were included in this retrospective study. Patients were stratified for cardiovascular risk using EuroSCORE II and SinoSCORE. The performance of EuroSCORE II and SinoSCORE was analysed with a focus on discrimination power and calibration. RESULTS: The in-hospital mortality rate for the entire cohort was 1.4%, while the mortality rate predicted by EuroSCORE II was 1.47 ± 1.2% (95% CI 1.43-1.50) and by SinoSCORE was 2.86 ± 3.5% (95% CI 2.76-2.96). The C-statistics of EuroSCORE II and SinoSCORE were 0.728 and 0.716, respectively. The Hosmer-Lemeshow test indicated that EuroSCORE II had poor goodness of fit while SinoSCORE performed slightly better. When patients were divided into quartiles based on predicted risk, respectively defined as group I, II, III and IV, EuroSCORE II underestimated mortality rates of patients scored IV, but overestimated mortality rates in all other groups; SinoSCORE underestimated mortality rates of patients scored I and overestimated mortality rates in all other groups. EuroSCORE II only achieved good discrimination for patients scored I (area under the receiver operating characteristic curve, AUC = 0.707 > 0.70), and SinoSCORE achieved poor discrimination for all subgroups except group II (AUC = 0.754 > 0.70). EuroSCORE II overestimated the mortality rate in the isolated CABG group and underestimated mortality rates in patients with other cardiac surgeries. SinoSCORE overestimated mortality rates in all pathology subgroups. The AUC values of EuroSCORE II and SinoSCORE were 0.694 and 0.687, respectively, for isolated CABG. The AUC values of EuroSCORE II and SinoSCORE were 0.772 and 0.669 for combined cardiac surgery CABG. CONCLUSIONS: EuroSCORE II could predict mortality in the entire group and in the low-middle risk group, but not in the high-risk group, in which it underestimated mortality. SinoSCORE overestimated mortality rates in the entire group and in all subgroups. Risk models should be targeted to different heart diseases, and the statistical methods of established risk systems should be improved.

Piezoelectric, Mechanical and Acoustic Properties of KNaNbOF5 from First-Principles Calculations.

Recently, a noncentrosymmetric crystal, KNaNbOF5, has attracted attention due to its potential to present piezoelectric properties. Although α- and ß-KNaNbOF5 are similar in their stoichiometries, their structural frameworks, and their synthetic routes, the two phases exhibit very different properties. This paper presents, from first-principles calculations, comparative studies of the structural, electronic, piezoelectric, and elastic properties of the α and the ß phase of the material. Based on the Christoffel equation, the slowness surface of the acoustic waves is obtained to describe its acoustic prosperities. These results may benefit further applications of KNaNbOF5.

Clearance of Propionibacterium acnes by kupffer cells is regulated by osteopontin through modulating the expression of p47phox.

Osteopontin (OPN) is a cytokine with multiple functions, including the regulation of innate immune response. However, the detailed function and mechanism of OPN in host defense against invaded microorganisms remain unclear. In this report, we revealed that OPN could affect the clearance of Propionibacterium acnes in kupffer cells. In a murine model of P. acnes induced hepatic granuloma, OPN-deficient mice or wild-type (WT) mice treated with anti-OPN mAb exhibited more hepatic granuloma formation than WT mice. Increased infiltration of intrahepatic leukocytes, higher expression of TLRs, and significantly upregulated level of proinflammatory cytokines of liver tissue were observed in OPN-deficient mice after P. acnes challenge. Moreover, in vitro assay showed that kupffer cells isolated from OPN(-/-) mice exhibited impairment in clearance of P. acnes. Kupffer cells isolated from OPN(-/-) mice showed reduced level of NADPH oxidase-mediated reactive oxygen species (ROS) in response to P. acnes, which was regulated by NADPH oxidase subunit p47phox. Further investigation revealed that OPN interaction with αvß3 integrin activated PI3K and ERK signal pathways, leading to the expression of p47phox. Taken together, these data demonstrated an important role of OPN in enhancing the antimicrobial innate immune response by modulation of bacterium clearance activity in kupffer cells.

Identification of a novel functional domain of ricin responsible for its potent toxicity.

Ribosome-inactivating proteins (RIPs) are toxic N-glycosidases that depurinate the universally conserved α-sarcin loop of large rRNAs. They have received attention in biological and biomedical research because of their unique biological activities toward animals and human cells as cell-killing agents. A better understanding of the depurination mechanism of RIPs could allow us to develop potent neutralizing antibodies and to design efficient immunotoxins for clinical use. Among these RIPs, ricin exhibited remarkable efficacy in depurination activity and highly conserved tertiary structure with other RIPs. It can be considered as a prototype to investigate the depurination mechanism of RIPs. In the present study, we successfully identified a novel functional domain responsible for controlling the depurination activity of ricin, which is located far from the enzymatic active site reported previously. Our study indicated that ricin A-chain mAbs binding to this domain (an α-helix comprising the residues 99-106) exhibited an unusual potent neutralizing ability against ricin in vivo. To further investigate the potential role of the α-helix in regulating the catalytic activity of ricin, ricin A-chain variants with different flexibility of the α-helix were rationally designed. Our data clearly demonstrated that the flexibility of the α-helix is responsible for controlling the depurination activity of ricin and determining the extent of protein synthesis inhibition, suggesting that the conserved α-helix might be considered as a potential target for the prevention and treatment of RIP poisoning.