On a Certain Sub-Riemannian Geodesic Flow on the Heisenberg Group

Under study is an integrable geodesic flow of a left-invariant sub-Riemannian metric for a right-invariant distribution on the Heisenberg group. We obtain the classification of the trajectories of this flow. There are a few examples of trajectories in the paper which correspond to various values of the first integrals. These trajectories are obtained by numerical integration of the Hamiltonian equations. It is shown that for some values of the first integrals we can obtain explicit formulae for geodesics by inverting the corresponding Legendre elliptic integrals.     

Identification of individual isotopes in a polymer blend using tip enhanced Raman spectroscopy

For the first time, tip enhanced Raman spectroscopy (TERS) blinking measurements are used to identify the individual isotopes of non‐Raman resonant polystyrene in a miscible, binary blend. This demonstrates the sensitivity and selectivity required for nanoscale chemical imaging and broadens the types of surface components potentially identifiable with TERS. Copyright © 2015 John Wiley & Sons, Ltd.     

Influence of the grain-size and chemical composition of a MgO coating on the structure-phase state and elemental composition of the ground layer formed on an electric steel surface

The surface morphology, phase state and elemental composition, and substructure of the ground layer of anisotropic electric steel (AES) samples have been studied via scanning electron microscopy, atomic force microscopy, transmission electron microscopy, electron probe microanalysis, and x-ray diffractometry. High-temperature annealing of MgO coatings with different grain-size distributions and chemical compositions was found to lead to formation of a single-phase layer of forsterite (Mg₂SiO₄) on the AES surface. It has been revealed that the morphology and substructure of a forsterite layer depend on the grain-size distribution and chemical composition of magnesium oxide and the conditions used in preparation of MgO suspensions. When added to MgO suspensions, TiO₂ and Na₂B₄O₇ impurities promote formation of a denser coating substructure. The increased mixing speed used in suspension preparation improves the surface homogeneity of a ground layer only if a suspension contains MgO grains of different size.     

A study of the chemical stability of beryl and of the product of its mechanical activation against sulfuric acid

Effect of the concentration of sulfuric acid used for beryl sulfatization, degree of beryl grinding, temperature and duration of beryl sulfatization, and other technological parameters of sulfuric acid decomposition on the extent of beryl recovery was studied. The results obtained made it possible to suggest a method for preparation of beryl concentrates for sulfatization. The method is based on a mechanochemical activation of this kind of raw materials and can serve as an alternative to the conventionally employed beryl activation techniques.     

Probing the mechanisms of ambient ionization by laser‐induced fluorescence spectroscopy

The ionization mechanisms of several atmospheric pressure ion sources based on desorption and ionization of samples deposited on a surface were studied. Home‐built desorption electrospray ionization (DESI), laserspray ionization (LSI), and atmospheric pressure matrix‐assisted laser desorption/ionization (AP‐MALDI) sources were characterized using low‐molecular‐weight compounds, in particular fluorescent dyes. Detection of the desorbed and ionized species was performed by laser‐induced fluorescence and ion cyclotron resonance mass spectrometry. The dependences of the signal intensities on various experimental parameters were studied. The data obtained reveals common features, such as formation of solvated species and clusters in the ionization processes, in all of the techniques considered. Copyright © 2012 John Wiley & Sons, Ltd.     

Detoxication of Aqueous Cyanide Solutions with Oxygen in the Presence of S(IV) and Cu(II) Compounds

Oxidation of cyanide anions with atmospheric oxygen in aqueous solutions in the presence of Na₂SO₃ and NaHSO₃ mixture and CuSO₄ as a catalyst was studied. The reaction mechanism was proposed.     

Recent trends in ultra‐fast HPLC: New generation superficially porous silica columns

New generation columns, i.e. packed with superficially porous silica particles are available as trade names with following manufacturers: Halo, Ascentis Express, Proshell 120, Kinetex, Accucore, Sunshell, and Nucleoshell. These provide ultra‐fast HPLC separations for a variety of compounds with moderate sample loading capacity and low back pressure. Chemistries of these columns are C₈, C₁₈, RP‐Amide, hydrophilic interaction liquid chromatography, penta fluorophenyl (PFP), F5, and RP‐aqua. Normally, the silica gel particles are of 2.7 and 1.7 μm as total and inner solid core diameters, respectively, with 0.5‐μm‐thick of outer porous layer having 90 Å pore sizes and 150 m²/g surface area. This article describes these new generation columns with special emphasis on their textures and chemistries, separations, optimization, and comparison (inter and intra stationary phases). Besides, future perspectives have also been discussed.     

Detailed insight into the hydrogen bonding interactions in acetone-methanol mixtures. A molecular dynamics simulation and Voronoi polyhedra analysis study

Voronoi polyhedra (VP) analysis of mixtures of acetone and methanol is reported on the basis of molecular dynamics computer simulations, performed at 300 K and 1 bar. The composition of the systems investigated covers the entire range from neat acetone to neat methanol. Distribution of the volume, reciprocal volume and asphericity parameter of the VP as well as that of the area of the individual VP faces and of the radius of the empty voids located between the molecules are calculated. To investigate the tendency of the like molecules to self-associate the analyses are repeated by disregarding one of the two components. The self-aggregates of the disregarded component thus turn into large empty voids, which are easily detectable in VP analysis. The obtained results reveal that both molecules show self-association, but this behavior is considerably stronger among the acetone than among the methanol molecules. The strongest self-association of the acetone and methanol molecules is found in their mole fraction ranges of 02-0.5 and 0.5-0.6, respectively. The caging effect around the methanol molecules is found to be stronger than around acetones. Finally, the local environment of the acetone molecules turns out to be more spherical than that of the methanols, not only in the respective neat liquids, but also in their mixtures.     

Structural and optical properties of porous silicon prepared from a p +-epitaxial layer on n-Si(111)

The structural and optical properties of porous silicon prepared by anodic etching of an n-Si(111) wafer with a p ⁺-homoepitaxial layer on one side are studied by scanning electron microscopy and multiple-crystal X-ray diffraction. A considerable difference between the microstructures on the sides of the wafer is found. Upon aging for 4.5 months, diffraction peaks of the por-Si structures shift from that of the substrate by δθ = ?42″ for the n-Si porous layer and ?450″ for the p ⁺-Si porous layer. The photoluminescence band associated with the p ⁺-layer is twice as narrow as the band associated with the n-layer and is shifted toward shorter wavelengths (higher energies) by 0.4 eV, with the intensities of the bands being the same.