Relationships of the synthesis of silicon dioxide nanoparticles in low-temperature plasma created in helium and argon at atmospheric pressure

Low-temperature plasma-chemical synthesis of silicon dioxide nanoparticles from tetraethoxysilane, performed at atmospheric pressure in a reactor with flat perforated electrodes coated with an insulating layer, was studied. The use of such electrodes allows reaching stable sustaining of RF discharge (α-mode) with helium and argon used as plasma-forming gases. The relationships of the synthesis of silicon dioxide nanoparticles from tetraethoxysilane in helium and argon plasma differ insignificantly. Most probably, nanoparticles with the size in the interval 100–150 nm are formed in the zone of the discharge sustaining, but, as the particles are transported with the gas flow beyond the plasma zone, they undergo agglomeration. An increase in the nanoparticle size to 100–150 nm, observed when using perforated electrodes with an insulating coating, is most probably due to an increase in the residence time of the reaction gas medium in the zone of the discharge sustaining.     

Upper bound of the limit load for a tensile cylinder with a soft welded (soldered) joint containing a crack

The limit load is one of the main characteristics in estimating the performance of different structures, in particular, structures with soft welded (soldered) joints. In some cases, the difference between the yield strengths of the main material and the joint material is so great that plastic strain is localized in a thin joint. With some features of such strain distribution taken into account, an upper bound of the limit load of a tensile axisymmetric sample with a crack in a welded (soldered) joint is obtained.     

Free-surface roughness of thin-walled tubes in reduction

The problem of the stress-strain state of thin-walled tubes in axisymmetric steady-state deformation is solved using the membrane theory of shells and the model of an ideal rigid-plastic material satisfying the Mises yield condition and the associated flow law. The obtained solution is used together with the empirical relation between the strain state at an arbitrary point of the free surface and the surface roughness parameters at the same point to determine the influence of some tube reduction parameters on the surface roughness parameters in the product. The employed empirical relation is derived assuming that the free surface roughness parameters depend on two independent kinematic variables.     

A prototype of a high-voltage platform for the KRION ion source

A high-voltage platform that has been developed for the KRION ion source is described. The platform design concept is explained. The calculations that have been performed of the influence of the design and materials on the source magnetic field make it possible to define a range of materials suitable for manufacturing the platform. The major components of the high-voltage platform, such as a high-voltage power supplier, and decoupling insulators of the high-voltage power source, and the main and supplementary platforms, are chosen and described. It is determined that, to exclude electric breakdowns and corona discharges, one should use an electrically shielded channel with a cryocooler and power supplies for the KRION-source coupling cables.     

Data-Independent Microbial Metabolomics with Ambient Ionization Mass Spectrometry

Atmospheric ionization methods are ideally suited for prolonged MS/MS analysis. Data-independent MS/MS is a complementary technique for analysis of biological samples as compared to data-dependent analysis. Here, we pair data-independent MS/MS with the ambient ionization method nanospray desorption electrospray ionization (nanoDESI) for untargeted analysis of bacterial metabolites. Proof-of-principle data and analysis are illustrated by sampling Bacillus subtilis and Pseudomonas aeruginosa directly from Petri dishes. We found that this technique enables facile comparisons between strains via MS and MS/MS plots which can be translated to chemically informative molecular maps through MS/MS networking. The development of novel techniques to characterize microbial metabolites allows rapid and efficient analysis of metabolic exchange factors. This is motivated by our desire to develop novel techniques to explore the role of interspecies interactions in the environment, health, and disease. This is a contribution to honor Professor Catherine C. Fenselau in receiving the prestigious ASMS Award for a Distinguished Contribution in Mass Spectrometry for her pioneering work on microbial mass spectrometry.

Reactions of 2- and 4-pyrones with secondary phosphine chalcogenides: a facile synthesis of functional phosphorylated pyrones

The oxidative cross-coupling between 4-hydroxy-6-methyl-2-pyrone or 3-hydroxy-2-methyl-4-pyrone and secondary phosphine chalcogenides proceeds in CCl₄/Et₃N under mild conditions (20–52 °С, 0.75–10 h) through the hydroxyl group to give O-(6-methyl-2-oxo-2H-pyran-4-yl) diorganylphosphinochalcogenoates or O-(2-methyl-4-oxo-4H-pyran-3-yl) diorganylphosphinochalcogenoates, in high yields.