Promotional effects of Nb5+ and Fe3+ co-doping on catalytic performance and SO2 resistance of MnOx-CeO2 low-temperature denitration catalyst.

As we know, SO2 can cause MnOx-CeO2 (MnCeOx) catalyst poisoning, which seriously shortens the service life of the catalyst. Therefore, to enhance the catalytic activity and SO2 tolerance of MnCeOx catalyst, we modified it by Nb5+ and Fe3+ co-doping. And the physical and chemical properties were characterized. These results illustrate that the Nb5+ and Fe3+ co-doping can optimally improve the denitration activity and N2 selectivity of MnCeOx catalyst at low temperature by improving its surface acidity, surface adsorbed oxygen as well as electronic interaction. What's more, NbOx-FeOx-MnOx-CeO2 (NbFeMnCeOx) catalyst possesses an excellent SO2 resistance due to less SO2 being adsorbed and the ammonium bisulfate (ABS) formed on its surface tends to decompose, as well as fewer sulfate species formed on its surface. Finally, the possible mechanism that Nb5+ and Fe3+ co-doping enhances the SO2 poisoning resistance of MnCeOx catalyst is proposed.

Strain Variability in Growth and Thermal Inactivation Characteristics of Listeria monocytogenes Strains after Acid Adaptation.

ABSTRACT: Given the importance of strain variability to predictive microbiology and risk assessment, this study aimed to quantify the magnitude of strain variability in growth and thermal inactivation kinetics behaviors after acid adaptation. Thirty-three Listeria monocytogenes strains were exposed to acid-adapted tryptic soy broth supplemented with yeast extract (TSBYE; pH 5.5) and non-acid-adapted TSBYE (pH 7.0) for 20 h. Next, the growth parameters of these adapted and nonadapted strains that grew in nonbuffered TSBYE at 25°C were estimated. The tested strains were inactivated at 60°C in nonbuffered broth to obtain the heat resistance parameters. The results revealed that strain variability was present in the growth and thermal inactivation characteristics. The maximum specific growth rate ranged from 0.21 to 0.44 h-1 and from 0.20 to 0.45 h-1 after acid and nonacid adaptation, respectively. The lag times were from 0.69 to 2.56 h and from 0.24 to 3.36 h for acid-adapted and non-acid-adapted cells, respectively. The apparent D-values at 60°C of the pathogen ranged between 0.56 and 3.93 min and between 0.52 and 3.63 min for the presence and absence of acid adaptation condition, respectively. Acid adaptation significantly (P < 0.05) increased the magnitude of strain variability in the thermal inactivation characteristics of L. monocytogenes, with the coefficient of variation increasing to 0.17, whereas acid adaptation did not significantly (P ≥ 0.05) influence the variabilities in the growth parameters of the tested strains. Furthermore, the subsequent growth behaviors of all strains did not exhibit significant (P > 0.05) changes after exposure to acidic broth. However, the thermal resistance of most (25 of 33) of the tested strains increased (P < 0.05) after growing in acid-adapted broth. The relevant data generated in the present study can be used to describe the strain variability in predictive microbiology and to deeply understand the behavioral responses of different strains to acid adaptation.

[Strain variability of foodborne pathogens in microbiological risk assessment - a review].

Strain variability is one of the most important factors to influence the accuracy of foodborne pathogens risk assessment, such as Listeria monocytogenes, Salmonella spp. Strain-to-strain variation is defined as the inherent differences among identically treated strains of the same microbial species. The differences cannot be eliminated by changing test methods or improving test protocols. This review addresses presently related studies of strain variability. Based on the effect of strain variability on the outcome of risk assessment, we summarize sources of variabilities in food chain, strain phenotypic variabilities and the methods to integrate strain variability in growth and inactivation into predictive modelling, and indicate the inadequacies in the study of strain variability. We suggest further study the mechanism of strain variability, expand the comparison of variability among different sources, and integrate the variability of gene expression, protein and cell metabolism into the predictive modelling.

Association between matrix metalloproteinase gene polymorphisms and development of ischemic stroke.

We investigated the association between MMP2 rs243865, MMP3 rs3025058 and MMP9 rs3918242 polymorphisms and development of ischemic stroke in a Chinese population. Between January 2012 and May 2014, a total of 317 patients with ischemic stroke and 317 health control subjects were enrolled into our study. The MMP2 rs243865, MMP3 rs3025058 and MMP9 rs3918242 polymorphisms were analyzed using polymerase chain reaction (PCR) coupled with restriction fragment length polymorphism (RFLP). By multivariate logistic regression analysis, we found that individuals carrying with the CC genotype and the TC+CC genotype of MMP9 rs3918242 were associated with a significantly increased risk of ischemic stroke when compared with the TT genotype, and the ORs (95% CI) was 5.47 (2.64-12.38) and 1.55 (1.08-2.24), respectively. The TC+CC genotype of MMP9 rs3918242 was associated with an elevated risk of ischemic stroke in tobacco smokers, and the OR (95% CI) was 2.03 (1.11-3.74). In conclusion, our study suggests that MMP9 rs3918242 polymorphism is correlated with an elevated risk of ischemic stroke, and this gene polymorphism has interaction with tobacco smoking in the risk of ischemic stroke.

Lithium isotope traces magmatic fluid in a seafloor hydrothermal system.

Lithium isotopic compositions of fluid inclusions and hosted gangue quartz from a giant volcanogenic massive sulfide deposit in China provide robust evidence for inputting of magmatic fluids into a Triassic submarine hydrothermal system. The δ(7)Li results vary from +4.5‰ to +13.8‰ for fluid inclusions and from +6.7‰ to +21.0‰ for the hosted gangue quartz(9 gangue quartz samples containing primary fluid inclusions). These data confirm the temperature-dependent Li isotopic fractionation between hydrothermal quartz and fluid (i.e., Δδ(7)Liquartz-fluid = -8.9382 × (1000/T) + 22.22(R(2) = 0.98; 175 °C-340 °C)), which suggests that the fluid inclusions are in equilibrium with their hosted quartz, thus allowing to determine the composition of the fluids by using δ(7)Liquartz data. Accordingly, we estimate that the ore-forming fluids have a δ(7)Li range from -0.7‰ to +18.4‰ at temperatures of 175-340 °C. This δ(7)Li range, together with Li-O modeling , suggest that magmatic fluid played a significant role in the ore formation. This study demonstrates that Li isotope can be effectively used to trace magmatic fluids in a seafloor hydrothermal system and has the potential to monitor fluid mixing and ore-forming process.

Formation of carbonatite-related giant rare-earth-element deposits by the recycling of marine sediments.

Carbonatite-associated rare-earth-element (REE) deposits are the most significant source of the world's REEs; however, their genesis remains unclear. Here, we present new Sr-Nd-Pb and C-O isotopic data for Cenozoic carbonatite-hosted giant REE deposits in southwest China. These REE deposits are located along the western margin of the Yangtze Craton that experienced Proterozoic lithospheric accretion, and controlled by Cenozoic strike-slip faults related to Indo-Asian continental collision. The Cenozoic carbonatites were emplaced as stocks or dykes with associated syenites, and tend to be extremely enriched in Ba, Sr, and REEs and have high (87)Sr/(86)Sr ratios (>0.7055). These carbonatites were likely formed by melting of the sub-continental lithospheric mantle (SCLM), which had been previously metasomatized by high-flux REE- and CO2-rich fluids derived from subducted marine sediments. The fertility of these carbonatites depends on the release of REEs from recycled marine sediments and on the intensity of metasomatic REE refertilization of the SCLM. We suggest that cratonic edges, particularly along ancient convergent margins, possess the optimal configuration for generating giant REE deposits; therefore, areas of metamorphic basement bounded or cut by translithospheric faults along cratonic edges have a high potential for such deposits.