Estimation of the Dihedral Angle Between Metal Nanoparticles During Their Coalescence

The process of coalescence of various metal nanoparticles has been studied by the Monte Carlo method. The interaction of nanoparticles is described by a multiparticle Gupta type potential. An algorithm of recognizing and estimating a dihedral angle at the neck is developed. The dihedral angle between metal nanoparticles during their sintering is estimated

Determination of ππ\pi\pi scattering lengths from measurement of π+π−\pi^+\pi^- atom lifetime

The DIRAC experiment at CERN has achieved a sizeable production of $\pi^+\pi^-$ atoms and has significantly improved the precision on its lifetime determination. From a sample of 21227 atomic pairs, a 4% measurement of the S-wave $\pi\pi$ scattering length difference $|a_0-a_2| = (.0.2533^{+0.0080}_{-0.0078}|_\mathrm{stat}.{}^{+0.0078}_{-0.0073}|_\mathrm{syst})M_{\pi^+}^{-1}$ has been attained, providing an important test of Chiral Perturbation Theory.Comment: 6 pages, 6 figure

Investigation of welding process of vitrimer-based material: meso-scale simulation

A self-healing epoxy material is considered, based on bisphenol A diglycidyl ether and atricarboxylic fatty acid hardener, belonging to a new class of polymers called vitrimers. The res toration of the integrity of such systems in the case of a damage occurs due to the exchange reaction of covalent bonds between the comonomers forming a polymer network. In our previous work, we have developed a model of this material based on the method of reactive dissipative particle dynamics. In this work, we apply our model to study the welding process of vitrimer samples cut into two parts. The control of the integrity of the structure of the systems was carried out using a topological analysis by calculating the distributions over the lengths of simple cycles and the density of the number of load-bearing circuits. It has been shown that the rate of restoration of the integrity of the systems is determined by the concentration of the catalyst and the degree of crosslinking of the polymer. The results obtained also indicate that in the case of a high degree of crosslinking of the polymer, as well as a low catalyst concentration, the structure of the system is highly inhomogeneous

Correlation method for pattern recognition

A new approach towards solving the pattern recognition problems in hybrid optical/digital correlators is suggested. The method is based on the authors' know-how-principle of transforming the field intensity or amplitude data on the identified object assuming that these data may be entered into a computer by ordinary methods. This principle allows to solve the unification of the correlation functions and recognition attributes selection problem using a unified, identified object's class-independent method. Presented experimental results confirm applicability of this approach

Aryloxy Alkyl Magnesium versus Dialkyl Magnesium in the Lanthanidocene-Catalyzed Coordinative Chain Transfer Polymerization of Ethylene

Complexes [(1,2,4-Ph3C5H2)2NdCl2K(THF)2]2 (Nd1), {[1,2-Ph2-4-(4-MeOC6H4)C5H2]2NdCl2K(THF)2}2 (Nd2), {[1,2-Ph2-4-(2-MeOC6H4)C5H2]2NdCl2[K(THF)4]}(THF)0.5 (Nd3), and [(1,2,4-Ph3C5H2)2TbCl2K]2 (Tb1) have been synthesized, studied by X-ray diffraction analysis, and used in coordinative chain transfer polymerization (CCTP) of ethylene upon activation by alkyl magnesium derivatives. The complexes Nd1 and Tb1 exhibiting similar molecular structures and the same core type have demonstrated similar catalytic activities. Two types of alkylating/chain transfer agents, namely, di-n-butyl magnesium and heteroleptic complex (BHT)Mg(THF)2 nBu Mg1 (BHT = 2,6-di-tert-butyl-4-methylphenoxide), have been studied in this reaction. We have found that (BHT)Mg(PE) products (PE is an oligoethylene chain) are being formed at a relatively high rate while using Mg1 at 40 °C in the solution polymerization of ethylene; the oligomeric products comprise more than 40 ethylene fragments, unlike Mg(PE)2 derivatives, which are obtained from MgnBu2 and contain about 20 ethylene fragments. Luminescence spectroscopy study of the reaction mixtures, while initiating the complex Tb1 by MgnBu2 or Mg1, confirmed the structural proximity and high symmetry of the catalytic complexes for both types of Mg reagents. These experimental results reaffirmed the hypothesis about the CCTP mechanism, suggesting the formation of trinuclear LnMg2 catalytic species. Within this mechanism, we can explain the increase in the polymerization degree (Pn) when Mg1 is used by growing a single oligoethylene chain (PE) per a Mg atom to form (μ-BHT)2Mg2(PE)2 species, whereas application of MgnBu2 provides the growth of two PE chains to form the Mg2(PE)4 product with lower solubility. © 2019 American Chemical Society