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Abstract  

Aluminum (Al) nanopowders with mean diameter of about 50 nm and passivated by alumina (Al2O3) coatings were prepared by an evaporation route: laser heating evaporation. Thermal properties of the nanopowders were investigated by simultaneous thermogravimetric-differential thermal analysis (TG-DTA) in dry oxygen environment, using a series of heating rates (5, 10, 20, 30, 50 and 90°C min−1) from room temperature to 1200°C. With the heating rates rise, the onset and peak temperatures of the oxidation rise, and the conversion degree of Al to Al2O3 varies. However, the specific heat release keeps relatively invariant and has an average value of 18.1 kJ g−1. So the specific heat release is the intrinsic characteristic of Al nanopowders, which can represent the ability of energy release.

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Summary  

The effects of bentonite density and fulvic acid on the sorption and diffusion of 90Sr2+in compacted bentonite were investigated by using a capillary method. The experiments were carried out at pH 7.0±0.1 in the presence of 0.01M NaClO4. The results suggest that the sorption and diffusion of 90Sr2+in compacted bentonite decreases with increasing the density of compacted bentonite. The presence of FA enhances the sorption of Sr2+, but reduces the diffusion of Sr2+in compacted bentonite. The porosity of the compacted bentonite plays an important role in the sorption and diffusion behavior of 90Sr2+. Using the calculated effective diffusion coefficients the long-term relative concentration distribution of strontium was evaluated in compacted bentonite.

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Abstract  

Hydrogen peroxide (H2O2) is popularly employed as a reaction reagent in cleaning processes for the chemical industry and semiconductor plants. By using differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2), this study focused on the thermal decomposition reaction of H2O2 mixed with sulfuric acid (H2SO4) with low (0.1, 0.5 and 1.0 N), and high concentrations of 96 mass%, respectively. Thermokinetic data, such as exothermic onset temperature (T 0), heat of decomposition (ΔH d), pressure rise rate (dP/dt), and self-heating rate (dT/dt), were obtained and assessed by the DSC and VSP2 experiments. From the thermal decomposition reaction on various concentrations of H2SO4, the experimental data of T 0, ΔH, dP/dt, and dT/dt were obtained. Comparisons of the reactivity for H2O2 and H2O2 mixed with H2SO4 (lower and higher concentrations) were evaluated to corroborate the decomposition reaction in these systems.

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Flow chemistry has emerged as the enabling field of high-throughput, data-driven discovery, and process chemistry, yet solids handling remains its key challenge. Insoluble salt by-products can stop flow, fluctuate reagent concentrations in reactors, and cost unexpected time and materials consumptions. The clogging of perfluoroalkoxy (PFA) tubing, stainless steel (SS) tubing, and a silicon microreactor by NaCl during a Pd-catalyzed amination using XPhos ligand was each studied. Our goal of understanding the appropriate reactor design provides in-depth analyses of constriction and mechanical entrapment. Calculations of Stokes number (St)>1 revealed that NaCl particle depositions were independent of the reactor materials. Analyses of the clogging time’s dependence on the residence time (τ) and particle volume fraction (ϕ) discovered commercial tubing to be inadequate for the decoupling of the kinetics. The results prescribe why fabricated microreactors with on-chip analytics, particle formations and dissolutions, and without fluidic connections are solutions to discover and develop ubiquitous reactions that form inorganic salt by-products.

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Abstract

Di-tert-butyl peroxide (DTBP) is an organic peroxide (OP) which has widespread use in the various chemical industries. In the past, thermal runaway reactions of OPs have been caused by their general thermal instability or by reactive incompatibility in storage or operation, which can create potential for thermal decomposition reaction. In this study, differential scanning calorimetry was applied to measure the heat of decomposition reactions, which can contribute to understand the reaction characteristics of DTBP. Vent sizing package 2 was also employed to evaluate rates of increase for temperature and pressure in decomposition reactions, and then the thermokinetic parameters of DTBP were estimated. Finally, hazard characteristics of the gassy system containing DTBP, specifically with respect to thermal criticality, were clearly identified.

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Abstract  

In terms of pre-safety assessment of a potential site for high-level radioactive wastes disposal in China, the geochemical behavior of key radionuclides which tend to be released from the repository must be thoroughly investigated. 99Tc is a long-lived fission product with appreciable productivity in nuclear fuel, and Tc (+7) has unlimited solubility in near-field geochemical environments. In this study, the effects of ionic strength and humic acid on 99TcO4 sorption and diffusion in Beishan granite were investigated with through-diffusion and batch sorption experiments. Results indicated that the effective diffusion coefficients (D e) of 99TcO4 in Beishan granite varied from 1.07 × 10−12 to 1.28 × 10−12 m2/s without change with ionic strength, while the distribution coefficients (K d) negatively correlated with ionic strength of the rock/water system. This study also indicates that there is no evident influence of humic acid concentration on the diffusion behavior of 99TcO4 in Beishan granite, due to the limited interaction between humic acid and 99TcO4 .

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Journal of Radioanalytical and Nuclear Chemistry
Authors: D. Xu, Q. L. Ning, X. Zhou, C. L. Chen, X. L. Tan, A. D. Wu, and X. Wang

Summary  

Effects of ionic strength and of fulvic acid on the sorption of Eu(III) on alumina were investigated by using a batch technique. The experiments were carried out at T=25±1 °C, pH 4-6 and in the presence of 1M NaCl. The results indicate that sorption isotherms of Eu(III) are linear at low pH values. The sorption-desorption of Eu(III) on alumina at pH 4.4 is reversible, but a sorption-desorption hysteresis is found at pH 5.0. Fulvic acid has an obvious positive effect on the sorption of Eu(III) on alumina at low pH values. The migration of Eu(III) in alumina was studied by using column experiments and 152+154Eu(III) radiotracer at pH 3.8. For column experiments, Eu(III) sorbed on alumina can be desorbed completely from the solid surface at low pH values. The findings are relevant to the evaluation of lanthanide and actinide ions in the environment.

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Lipopolysaccharide and b-1,3-glucan binding protein (LGBP) is a pattern recognition receptor that can recognize and bind LPS and b-1,3-glucan. LGBP has crucial roles in innate immune defense against Gram-negative bacteria and fungi. In this study, LGBP functions in Portunus trituberculatus innate immunity were analyzed. First, the mRNA expression of PtLGBP in hemocytes, hepatopancreas, and muscle toward three typical pathogen-associated molecular patterns (PAMPs) stimulations were examined using real-time PCR. Results show that the overall trend of relative expressions of the LGBP gene in three tissues is consistent, showing up-down trend. In each group, the highest expression of the LGBP gene was at 3 and 12 h post-injection. The LGBP gene is also expressed significantly higher in the hemocytes and hepatopancreas than in the muscle. The highest level of LGBP was in the lipopolysaccharides (LPS) and glucan-injected group, whereas the lowest level was in the PGN-injected group. Furthermore, bacterial agglutination assay with polyclonal antibody specifically for PtLGBP proved that the recombinant PtLGBP (designated as rPtLGBP) could exhibit obvious agglutination activity toward Gram-negative bacteria Escherichia coli, Vibrio parahaemolyticus, and V. alginolyticus; Gram-positive bacteria Bacillus subtilis; and fungi Saccharomyces cerevisiae. LGBP in Portunus trituberculatus possibly served as a multi-functional PRR. In addition, LGBP is not only involved in the immune response against Gram-negative and fungi, as manifested in other invertebrates, but also has a significant role in anti-Gram-positive bacteria infection.

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