Aluminium/tin (IV) oxide thermite composite: sensitivities and reaction propagation

ABSTRACT

Thermites are energetic composites made of metal and oxidizer particles that react according to an exothermic reaction and release large amounts of energy. Many possible metal and oxidizer couples exist in the literature. Here, the performance of the aluminum reducing metal and tin (IV) oxide (SnO₂) combination was reported as a function of the fuel/oxidizer mass ratio. The Al/SnO₂ energetic composite, in stoichiometric conditions, was insensitive to impact, sensitive to friction and extremely sensitive to electrostatic discharge. The combustion velocity was determined to be close to 600 m/s. Changing the stoichiometry affected both the sensitivity thresholds to the friction test (160 N to > 360 N) and flame propagation velocity (480–588 m/s) of the Al/SnO₂ composite. These results are reported for the first time.     

Effect of Thermomechanical Fatigue on Precipitation Microstructure in Two Precipitation-Hardened Cast Aluminum Alloys

Thermal loading induces modifications of the precipitation microstructure of Al–Si–Cu–Mg alloys. This study focuses on the effect of deformation on precipitation microstructure during thermomechanical loadings. Several specimens were thermomechanically cycled while others were exposed to the same thermal cycles without any mechanical loading. The nature and morphological characteristics of the precipitation microstructure of the thermomechanically cycled specimens are compared to those of the thermally aged ones, using transmission electron microscopy (TEM), in order to assess the effect of deformation on the precipitation microstructure and especially on the kinetics of precipitate growth. The absence of any significant effect of superimposed straining during thermal cycling is discussed. Implications for the prevision of yield strength degradation during service operation are briefly presented.

     

The Magnetosome Protein,Mms6 from Magnetospirillum magneticum Strain AMB-1, Is a Lipid-Activated Ferric Reductase

Magnetosomes of magnetotactic bacteria consist of magnetic nanocrystals with defined morphologies enclosed in vesicles originated from cytoplasmic membrane invaginations. Although many proteins are involved in creating magnetosomes, a single magnetosome protein, Mms6 from Magnetospirillum magneticum strain AMB-1, can direct the crystallization of magnetite nanoparticles in vitro. The in vivo role of Mms6 in magnetosome formation is debated, and the observation that Mms6 binds Fe³⁺ more tightly than Fe²⁺ raises the question of how, in a magnetosome environment dominated by Fe³⁺, Mms6 promotes the crystallization of magnetite, which contains both Fe³⁺ and Fe²⁺. Here we show that Mms6 is a ferric reductase that reduces Fe³⁺ to Fe²⁺ using NADH and FAD as electron donor and cofactor, respectively. Reductase activity is elevated when Mms6 is integrated into either liposomes or bicelles. Analysis of Mms6 mutants suggests that the C-terminal domain binds iron and the N-terminal domain contains the catalytic site. Although Mms6 forms multimers that involve C-terminal and N-terminal domain interactions, a fusion protein with ubiquitin remains a monomer and displays reductase activity, which suggests that the catalytic site is fully in the monomer. However, the quaternary structure of Mms6 appears to alter the iron binding characteristics of the C-terminal domain. These results are consistent with a hypothesis that Mms6, a membrane protein, promotes the formation of magnetite in vivo by a mechanism that involves reducing iron.     

Retrogradation Kinetics of Eight Starches

Retrogradation rate and extent were determined by differential scanning calorimetry and rheology measurements on 40% dry matter gels made from pea, modified waxy maize, rice, waxy rice, wheat, manioc, potato and microwaved irradiated potato starches. As a result, each starch retrogrades differently, depending also on the measurement technique. Nevertheless, potato and pea starches seem to be the most sensitive and the waxy and modified waxy types are the least sensitive to retrogradation.     

APOB CRISPR-Cas9 Engineering in Hypobetalipoproteinemia: A Promising Tool for Functional Studies of Novel Variants

Hypobetalipoproteinemia is characterized by LDL-cholesterol and apolipoprotein B (apoB) plasma levels below the fifth percentile for age and sex. Familial hypobetalipoproteinemia (FHBL) is mostly caused by premature termination codons in the APOB gene, a condition associated with fatty liver and steatohepatitis. Nevertheless, many families with a FHBL phenotype carry APOB missense variants of uncertain significance (VUS). We here aimed to develop a proof-of-principle experiment to assess the pathogenicity of VUS using the genome editing of human liver cells. We identified a novel heterozygous APOB-VUS (p.Leu351Arg), in a FHBL family. We generated APOB knock-out (KO) and APOB-p.Leu351Arg knock-in Huh7 cells using CRISPR-Cas9 technology and studied the APOB expression, synthesis and secretion by digital droplet PCR and ELISA quantification. The APOB expression was decreased by 70% in the heterozygous APOB-KO cells and almost abolished in the homozygous-KO cells, with a consistent decrease in apoB production and secretion. The APOB-p.Leu351Arg homozygous cells presented with a 40% decreased APOB expression and undetectable apoB levels in cellular extracts and supernatant. Thus, the p.Leu351Arg affected the apoB secretion, which led us to classify this new variant as likely pathogenic and to set up a hepatic follow-up in this family. Therefore, the functional assessment of APOB-missense variants, using gene-editing technologies, will lead to improvements in the molecular diagnosis of FHBL and the personalized follow-up of these patients.