Synthesis of Schiff base–containing benzoxazine derivatives

The excellent chemical and physical properties of benzoxazine resins and the functionality of Schiff bases were combined in one compound's structure, creating newly designed benzoxazine derivatives that can form complexes with metals. The new type of benzoxazine monomer was synthesized via the ring-closure reaction of formaldehyde, aniline, and three newly designed Schiff bases. The presence of the Schiff base in the molecular structure of these novel benzoxazine monomers enables them to trap metals as the functional compounds, like Cu, from a solution. Thermally initiated polymerization occurs at a lower temperature by the formation of intermolecular and intramolecular hydrogen bonds between imine, oxazine, Schiff base hydroxyl groups, and the newly generated hydroxyl groups. The thermal behavior of the bisbenzoxazine monomers was investigated with Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and differential scanning calorimetry, and then they were cured at 120, 180, and 230°C. According to the magnetic susceptibility, FTIR, scanning electron microscopy with energy dispersive X-ray spectroscopy, TGA, and microwave plasma atomic emission spectroscopy results, it is shown that Cu(II) complexes of the compounds were also succesfully synthesized, and they proved to be successful in catching metal. This is due to the functionality of Schiff bases forming the metal complexation in the compounds. The poly(bisbenzoxazine)s also showed high limiting oxygen index (31–37), low ring-opening temperature (150–190°C), high char yield (35%–49%), and excellent thermal stability, due to the highly crosslinked nature of the polymers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47908.     

The effect of fullerene C60 on the thermooxidative degradation of a free-radical PMMA studied by thermogravimetry and calorimetry

Thermogravimetric and calorimetric study of the effect of fullerene C₆₀ on the thermooxidative degradation of free-radical poly(methyl methacrylate) revealed three stages in the process.     

EEG source localization using a sparsity prior based on Brodmann areas

Localizing the sources of electrical activity in the brain from electroencephalographic (EEG) data is an important tool for noninvasive study of brain dynamics. Generally, the source localization process involves a high‐dimensional inverse problem that has an infinite number of solutions and thus requires additional constraints to be considered to have a unique solution. In this article, we propose a novel method for EEG source localization. The proposed method is based on dividing the cerebral cortex of the brain into a finite number of “functional zones” which correspond to unitary functional areas in the brain. To specify the sparsity profile of human brain activity more concisely, the proposed approach considers grouping of the electrical current dipoles inside each of the functional zones. In this article, we investigate the use of Brodmann's areas as the functional zones while sparse Bayesian learning is used to perform sparse approximation. Numerical experiments are conducted on a realistic head model obtained from segmentation of MRI images of the head and includes four major compartments namely scalp, skull, cerebrospinal fluid (CSF), and brain with relative conductivity values. Three different electrode setups are tested in the numerical experiments. The results demonstrate that the proposed approach is quite promising in solving the EEG source localization problem. In a noiseless environment with 71 electrodes, the proposed method was found to accurately locate up to 6 simultaneously active sources with accuracy >70%.     

Possibilities of the magnetodynamic method for testing the thickness of two-layer coatings

The dependence of the normal component of the secondary-magnetic-field flux above the surface of a two-layer (nonmagnetic-ferromagnetic) coating on a nonmagnetic base on the parameters of a magnetodynamic transducer and on the ratio of the magnetic and nonmagnetic coating layer thicknesses has been studied. The possibilities of testing the thickness of a magnetic layer under a nonmagnetic layer regardless of the thickness of the latter (within a certain range) and separately measuring the layer thicknesses owing to selection of the transducer characteristics are substantiated.     

Ultra-fast boriding of nickel aluminide

In this study, we explored the possibility of ultra-fast electrochemical boriding of nickel aluminide (Ni₃Al) in a molten borax electrolyte. Electrochemical boriding was performed at 950 °C for 15 min and at current densities ranging from 0.1 to 0.5 A/cm². The boride layers formed on the test samples were 50 to 260 μm thick depending on the current density. The mechanical, structural, and chemical characterization of the boride layers was carried out using a Vickers micro-hardness test machine, optical and scanning electron microscopes, and a thin film X-ray diffractometer. The hardness of boride layer was in the range from 800 to 1200 ± 50 HV depending on the load and the region from which the hardness measurements were taken. X-ray diffraction studies confirmed that the boride layers were primarily composed of Ni₃B, Ni₄B₃ and Ni₂₀AlB₁₄ phases. Structurally, the boride layer was very homogenous and uniformly thick across the borided surface area.     

Synthesis and characterization of V,Mo and Nb incorporated micro–mesoporous MCM-41 materials

Highly microporous metal-MCM-41 ordered mesoporous structure catalysts having different metal/Si (V, Mo, Nb) atomic ratios and combinations of metal sources were hydrothermally synthesized. The structural properties estimated using different techniques were found to be in agreement with each other. Metals were successfully incorporated into MCM-41 without deteriorating the ordered hexagonal structure. The metal ions in the synthesis solutions probably settled on the hydrophilic end of the template hence the metal incorporation resulted improvements in the micropore structure. Low loading of metals caused an increase in the surface area and pore volume values of the catalysts. The highest total (1310 m² g^?1) and micropore surface area values (1083 m² g^?1) were obtained by Nb incorporation. The micro- and mesopore dimensions of MCM-41 increased from 0.5 to 1.1 nm and from 2.5 to 2.8 nm, respectively, with metal incorporation. Low V/Si ratios and presence of Nb in the starting solution enhanced narrow mesopore size distribution. The pore dimension and wall thickness values estimated from nitrogen adsorption and X-ray diffraction methods were consistent with the corresponding values obtained using transmission electron microscopy.     

Alu Deletions in LAMA2 and CDH4 Genes Are Key Components of Polygenic Predictors of Longevity

Longevity is a unique human phenomenon and a highly stable trait, characterized by polygenicity. The longevity phenotype occurs due to the ability to successfully withstand the age-related genomic instability triggered by Alu elements. The purpose of our cross-sectional study was to evaluate the combined contribution of ACE*Ya5ACE, CDH4*Yb8NBC516, COL13A1*Ya5ac1986, HECW1*Ya5NBC182, LAMA2*Ya5-MLS19, PLAT*TPA25, PKHD1L1*Yb8AC702, SEMA6A*Yb8NBC597, STK38L*Ya5ac2145 and TEAD1*Ya5ac2013 Alu elements to longevity. The study group included 2054 unrelated individuals aged from 18 to 113 years who are ethnic Tatars from Russia. We analyzed the dynamics of the allele and genotype frequencies of the studied Alu polymorphic loci in the age groups of young (18–44 years old), middle-aged (45–59 years old), elderly (60–74 years old), old seniors (75–89 years old) and long-livers (90–113 years old). Most significant changes in allele and genotype frequencies were observed between the long-livers and other groups. The search for polygenic predictors of longevity was performed using the APSampler program. Attaining longevity was associated with the combinations LAMA2*ID + CDH4*D (OR = 2.23, P_Bonf = 1.90 × 10⁻²) and CDH4*DD + LAMA2*ID + HECW1*D (OR = 4.58, P_Bonf = 9.00 × 10⁻³) among persons aged between 18 and 89 years, LAMA2*ID + CDH4*D + SEMA6A*I for individuals below 75 years of age (OR = 3.13, P_Bonf = 2.00 × 10⁻²), LAMA2*ID + HECW1*I for elderly people aged 60 and older (OR = 3.13, P_Bonf = 2.00 × 10⁻²) and CDH4*DD + LAMA2*D + HECW1*D (OR = 4.21, P_Bonf = 2.60 × 10⁻²) and CDH4*DD + LAMA2*D + ACE*I (OR = 3.68, P_Bonf = 1.90 × 10⁻²) among old seniors (75–89 years old). The key elements of combinations associated with longevity were the deletion alleles of CDH4 and LAMA2 genes. Our results point to the significance for human longevity of the Alu polymorphic loci in CDH4, LAMA2, HECW1, SEMA6A and ACE genes, involved in the integration systems.