Segregation of calcium on the surface of aluminum-based powders and its effect on oxidation kinetics

Segregation in the surface layers of an aluminum alloy powder containing 1.3 wt % calcium is studied. With the use of X-ray photoelectron spectroscopy, it is found that the surface calcium content is increased to 34 wt % compared to the bulk. Oxidation of the powder in air studied with the use of thermogravimetry and differential scanning calorimetry showed that the high surface concentration and high chemical activity of calcium result in a doubling of the reaction yield at a temperature of 1750 K.     

Specific features of deuterium and tritium labeling of Pro-Gly-Pro-Leu and of physiologically active amino acids

γ-Aminobutyric acid (GABA), 3-hydroxy-L-tyrosine (D0PA), and Pro-Gly-Pro-Leu were labeled with hydrogen isotopes. The mean deuterium content per molecule was 7.5 atoms in Pro-Gly-Pro-Leu and up to 4 atoms in GABA and DOPA. The incorporation of isotopes depending on the reaction conditions was monitored by mass spectrometry. The isotope exchange efficiency was found to strongly depend not only on the reaction temperature and catalyst: substrate ratio, but also on processes occurring on the support surface.     

Fest‐Flüssig‐Trennung von feindispersen Suspensionen durch Pressfiltration bei pulsierendem Überdruck

The productivity of filtration systems for dewatering of finely dispersed suspensions can be increased by pulsating overpressure. For suspensions of marine organic‐mineral sediments, press filtration processes were investigated under static and pulsating overpressure. The influence of the static pressure component, the pressure amplitude characteristic, the pressure vibration frequency, and the filtration time on the volume of filtrate were determined. Based on Darcy's law, a model of the filtration process under static overpressure was developed. For pulsating overpressure, the mathematical theory of experiment planning and the statistical data analysis method were used.     

Modeling the Processes of Self-Organization in Crystal-Forming Systems: New Two-Layer Clusters–Precursors 0@(Na 2 Cd 6 )@(Na 12 Cd 26 ) and 0@(Na 3 Cd 6 )@(Na 6 Cd 35 ) for the Self-Assembly of the Na 26 Cd 141 – hP 168 Crystal Structure

The combinatoric and topological analysis and modeling of the self-assembly of the Na26Cd141–hP168 crystal structure (space group Pbcm; a = 5.483 Å, b = 24.519 Å, and c = 14.573 Å; and V = 1895 Å3) are performed using computational methods (the ToposPro software package). Ninety-eight versions of the cluster representation of the 3D atomic network with the number of structural units ranging from four to seven are found. It is determined that polyhedral clusters–precursors C8 = 0@Na2Cd6 and C9 = 0@Na3Cd6 are templates, on the surface of which atomic shells consisting of 38 and 41 atoms are formed. The composition of the two-layer clusters is C46 = 0@(Na2Cd6)@(Na12Cd26) and C50 = 0@(Na3Cd6)@(Na6Cd35). The centers of clusters C46 and C50 are occupied by positions 1a with the symmetry 6/mmm and 2c with the symmetry −6m2. The symmetry and topology codes of the processes of self-assembly of 3D structures from nanoclusters–precursors C46 and C50 are reconstructed.