Mechanical Activation and Thermal Treatment of Low-Energy Nb-2Si Powder Blend. The Experiment. II. Mathematical Model

Russian Physics Journal - The paper proposes a mathematical model of thermal explosion in mechanically activated Nb–2Si powder blend. A study of the dynamics of mechanical activation...     

Ultrahigh-spatial-resolution field-emission projection microscopy of insulating samples

The method of ultrahigh-spatial-resolution field-emission projection imaging of nonconducting tips is implemented experimentally. An image of a glass microcapillary tip was obtained for the first time by the nonscanning method with spatial resolution no worse than 20 nm.     

Effects of Hydrogen Peroxide on In Vitro Cultures of Tea (Camellia sinensis L.) Grown in the Dark and in the Light: Morphology,Content of Malondialdehyde,and Accumulation of Various Polyphenols

Tea plants (Camellia sinensis L.) are phenol-accumulating crops that are widely used for public health. The healing effect of tea leaf products is due to the biosynthesis of such phenolic compounds (PCs) as flavans, which have P-vitamin capillary-strengthening activity. Due to their limited habitat and the value of their specialized metabolites of a phenolic nature, a promising approach is to establish in vitro cultures from them that retain the ability to form PCs, which is characteristic of ex vivo tea plants. The aim of this study was to investigate the effect of exogenic H₂O₂ (0.01 mM; 0.1 mM; 1 mM) on the growth, morphology, degree of stress response, and accumulation of various phenolic compounds in tea plant callus cultures of different ages (24 or 36 days) grown under different cultivation conditions (darkness or light). According to the results obtained, the H₂O₂ effect on tea callus cultures of different ages did not cause changes in their morphophysiological characteristics, both after 2 h of exposure (rapid response of callus culture, RRCC) and after 48 h (delayed response of callus culture, DRCC). The determination of the malondialdehyde (MDA) content, which serves as an indicator of changes in the level of lipid peroxidation (LPO) and the presence of stress responses in plant cells, indicated either its maintenance at the control level, a decrease, or an increase. All these effects depended on the growth conditions of the tea callus cultures (darkness or light), their age, the duration of exposure (rapid or delayed response), and the H₂O₂ concentration. Similar trends were noted for the total content of PCs as well as the amount of flavans, proanthocyanidins (soluble and insoluble forms), and lignin. The plant cell responses reflected changes in its adaptation programs, when specialized metabolites act as a target for the action of H₂O₂, thereby contributing to an increase in their resistance.     

CaII,YbII and SmII Bis(Amido) Complexes Coordinated by NHC Ligands: Efficient Catalysts for Highly Regio- and Chemoselective Consecutive Hydrophosphinations with PH3

The first example of intermolecular hydrophosphination of styrene, 2-vinylpyridine and phenylacetylene with PH₃ catalyzed by bis-(amido) complexes [(Me₃Si)₂N]₂M(NHC)₂ (M=Ca, Yb, Sm) coordinated by NHC ligands is described. The reactions of styrene with PH₃ proceed under mild conditions in quantitative yields to afford only anti-Markovnikov product and allow for the chemoselective synthesis of primary, secondary and tertiary phosphines. Addition of phenylacetylene to PH₃ regardless the initial molar substrates ratio results in the exclusive formation of a tertiary tris-(Z-styryl)-phosphine. Crucial effect of the Lewis base coordinated to the metal ion in precatalyst on catalytic activity in styrene hydrophosphination with PH₃ was demonstrated. Free NHCs were also found to be able to promote addition of PH₃ to styrene, however they provide much lower reaction rates compared to the metal complexes.     

Nanostructured Carbon Coatings on Polyethylene Films

The properties of medical low-density polyethylene films with carbon coatings improving the biological compatibility of the polymer were studied by electron and scanning atomic-force microscopy, as well as by IR, Raman, visible, and UV spectroscopy.     

Emission Spectrum and Charged-Particle Trajectory in the Field of an Inhomogeneous Electromagnetic Wave

Doklady Physics - By the example of an inhomogeneous electromagnetic wave formed by the superposition of two plane monochromatic electromagnetic waves, which are arbitrarily directed relative to...     

Dynamics of the Homogenization of Binary Powder Mixtures

The effect the initial structure of a two-component reaction powder mixture has on the dynamics of its isothermal homogenization is investigated. Relations for determining the duration of homogenization are obtained. A technique for calculating kinetic parameters is proposed.     

Existence and properties of a static solution to a nonhomogeneous Burgers equation

A problem of expansion of nonlinear waves in a heterogeneous media is considered, this problem is described by a Burgers equation with a stochastic right-hand side. Existence of a statistical solution is proved and sufficient conditions are obtained for such properties as uniformity (independence on translation) of the probability measure of the solution, stationarity and ergodicity.     

Homogenization of high frequency nonlinear acoustics equations

High frequency nonlinear acoustics equations proposed in [1] are considered. The acoustic characteristics of the medium rapidly oscillate. This model describes the propagation of pulses of sound shocks generated by supersonic planes, blast waves in atmosphere and ocean, continuous radiation of sound sources. An asymptotic solutions of high frequency nonlinear acoustics equations is constructed (when the characteristic size of inhomogeneity is small with respect to the height of the layer where the problem is posed     

Crystal structure of glycine phosphite C<Subscript>2</Subscript>H<Subscript>5</Subscript>NO<Subscript>2</Subscript>·H<Subscript>3</Subscript>PO<Subscript>3</Subscript>

Single crystal X-ray diffraction study of glycine phosphite C₂H₅NO₂·H₃PO₃ was performed (monoclinic, space group P2₁/c, a = 7.401(3) Å, b = 8.465(3) Å, c = 9.737(3) Å; β = 100.73(5)°, Z = 4). It has been found that one of hydrogen atoms is located at the centre of symmetry forming two strong hydrogen bonds to yield H₄P₂O ₆ ^?2 dimers, while another hydrogen atom is statistically disordered over two positions and organizes the dimers into an infinite corrugated chain. The ordering of this hydrogen atom position and/or displacement of the other one from the centre of symmetry will lead to the loss of symmetry centre and lowering of the point group symmetry from C_2h to piezo-active group C₂ or C _s .