Adsorption of nitrogen on aluminum, Al2O3, and AlN powders at 78 K

The adsorption of nitrogen on aluminum powders of ASD-4 and UDA grades, aluminum oxide (α-Al₂O₃), and aluminum nitride is studied at 78 K in the adsorbate relative pressure range (P _a /P ₀) of 0 to 1. It is shown that the nature of the chemical bonds and the structure and state of the adsorbent determine the share of the adsorption isotherms and their attribution to a particular type of isotherms. With an increase in the fraction of metal bonds in an adsorbent, the isotherms become more convex, indicating enhancement of the effect of lateral interactions. The specific surfaces of samples are calculated.     

Oxidation of fine aluminum powders with water and air

Fine aluminum powders (RA20–RA60 grades, SUAL-PM) with specific surface area from 0.37 to 0.73 m²/g and high aluminum contents (95–98 wt %) are studied. The powders are found to be waterwettable without additions of surfactants and characterized by high rates of gas liberation in reacting with a calcium hydroxide solution under normal conditions. All RA20–RA60 powders are shown to be highly reactive upon oxidation with air and close to aluminum nanopowders in the parameters of their activity when heated in air. Their stability in water could prevent active (metallic) aluminum losses during their storage.     

Dynamics and mechanism of the interaction of graphite powders with ozone

The kinetics of ozone sorption by powders of finely milled graphite at 20 °C, the behavior of unpaired electrons of the conjugated systems of the structure, and the IR spectra of the surface functional groups were studied. The surface hexagonal cells enter into the reaction. After 1/6 of the accessible cells was consumed, the reaction rate decreased appreciably, most likely, due to the induction effects of the functional groups formed. Considerable weight losses of the samples were observed during the reaction. The changes in the character of the ESR spectra indicate a decrease in the sizes of the conjugation ensembles. The reaction of ozone with the surface produces local sites of structure destruction, which decrease the reactivity of the adjacent surface regions and thus protect them from further destruction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1772–1776, September, 2008.     

Influence of 1,3-dichloroacetone on the regularities of decay of arylnitroso oxides

The decay kinetics of isomeric forms of a series of arylnitroso oxides in the presence of 1,3-dichloroacetone in acetonitrile was studied by the flash photolysis technique. The regularities observed are explained by the complex formation between the molecules of nitroso oxide and additive.     

Thermodynamic calculations of the interaction of scandium halides with aluminum

The fundamental characteristics of the reduction of scandium trifluoride and trichloride with aluminum were studied by thermodynamic modeling over wide temperature and pressure ranges (1100–1400 K and 1–10⁶ Pa for ScF₃ and 800–1200 K and 1–10⁵ Pa for ScCl₃). Calculations of the equilibrium compositions of the systems were performed to draw conclusions about the contents of condensed and gaseous components and determine the temperatures of the complete reduction of trihalides with the formation of a two-phase alloy containing a saturated solution of scandium in aluminum and the Al₃Sc intermetallic compound. The results of modeling were in agreement with the available experimental data.     

Configuration interaction calculations on the nitrogen molecule

A contracted Gaussian basis set capable of describing about 63% of the correlation energy of N₂ has been used in a detailed configuration-interaction calculation. Second-order perturbation theory overestimated the correlation energy by 23–50% depending on how H⁰ was chosen. Pair-pair interaction affects the correlation energy by about 20% while quadruple excitations have an 8% effect.     

Synthesis and characterization of glycosylated nitrogen mustard derivatives and their interaction with bovine serum albumin

To improve the specificity of nitrogen mustards towards tumor cells, glucose-nitrogen mustard, fructose-nitrogen mustard, and lactose-nitrogen mustard were prepared as three novel glycosylated nitrogen mustard derivatives by esterification of bis(2-chloroethyl)carbamic chloride (BCC) with glucose, fructose, and lactose, respectively. BCC was synthesized from bis(2-chloroethyl)amine hydrochloride and triphosgene. The topic products were characterized by infrared (IR) and mass spectrometry (MS), and their interaction with bovine serum albumin was investigated by measuring fluorescence spectra in tris(hydroxymethyl)aminomethane hydrochloride (Tris–HCl) buffer solution at physiological conditions.     

A density-functional model of the dispersion interaction

We have recently introduced [J. Chem. Phys. 122, 154104 (2005)] a simple parameter-free model of the dispersion interaction based on the instantaneous in space, dipole moment of the exchange hole. The model generates remarkably accurate interatomic and intermolecular C6 dispersion coefficients, and geometries and binding energies of intermolecular complexes. The model involves, in its original form, occupied Hartree-Fock or Kohn-Sham orbitals. Here we present a density-functional reformulation depending only on total density, the gradient and Laplacian of the density, and the kinetic-energy density. This density-functional model performs as well as the explicitly orbital-dependent model, yet offers obvious computational advantages.     

Many-body effects of dispersion interaction

The role of many-body (MB) dispersion forces have been analyzed for strands, films, and cubic lattices in the framework of a model Hamiltonian that allows exact solution of the multiparticle Shrodinger equation. For the systems investigated the MB contribution may be as large as 7% of specific dispersion energy and 11% of solvation energy. Nonadditivity becomes particularly important for aggregation in solution, where its effect may be several times larger than the pairwise contribution. For all systems considered, the three-body Axilrod-Teller approximation was insufficient to predict the magnitude and in some cases even the sign of the full MB effect.     

Effect of atmospheric nitrogen on the oxidation mechanism of aluminum alloys with rare-earth metals

Interaction (25–620°C) of aluminum and its alloys with an atmosphere saturated with nitrogen was studied to determine the role played by rare-earth metals in the mechanism by which nitride phases are formed in oxidation of Al + REM alloys in air. The ellipsometric method and Auger electron spectroscopy were used to determine that, under the given experimental conditions, metallic aluminum is subjected to the greatest extent to the nitridation process, which is competing with the oxidation process. The process is initiated by the conversion of the amorphous oxide film to γ-Al₂O₃. The surface of Al + REM alloys interacts with nitrogen at the outer part of the oxide layer. The rare-earth metal actively reacts with impurity oxygen present in the atmosphere under study and hinders formation of nitride/oxynitride layers.     

Exchange-hole dipole moment and the dispersion interaction: high-order dispersion coefficients

In recent publications [A. D. Becke and E. R. Johnson, J. Chem. Phys. 122, 154104 (2005); E. R. Johnson and A. D. Becke 123, 024101 (2005)] we have demonstrated that the position-dependent dipole moment of the exchange hole can be used to generate dispersion interactions between closed-shell systems. Remarkably accurate C6 coefficients and intermolecular potential-energy surfaces can be obtained from Hartree-Fock occupied orbitals and polarizability data alone. In the present work, our model is extended to predict C8 and C10 coefficients as well. These higher-order coefficients are obtained as easily as C6 and with comparable accuracy.     

Bounds on dispersion coefficients for the interaction of helium atoms

We use a recently developed method to obtain tight bounds on multipole dispersion coefficients for the interaction of helium atoms.     

Exchange-hole dipole moment and the dispersion interaction

A simple model is presented in which the instantaneous dipole moment of the exchange hole is used to generate a dispersion interaction between nonoverlapping systems. The model is easy to implement, requiring no electron correlation (in the usual sense) or time dependence, and has been tested on various atomic and molecular pairs. The resulting C6 dispersion coefficients are remarkably accurate.     

Temperature-programmed reduction of cobalt-containing catalysts of the Fischer-Tropsch synthesis based on ultrafine aluminum powders alloyed with rare-earth metals

Russian Chemical Bulletin - The ultrafine aluminum powder alloyed with rare-earth metals (Ce, Sm), which is used as a support for the cobalt-containing catalysts of the Fischer-Tropsch synthesis,...     

Influence of bilirubin on the distribution of99mTc-HIDA and99mTc-IODIDA in rats and their interaction with HSA

The interaction of bilirubin and^99mTc-HIDA and^99mTc-IODIDA has been studied in rats. The mechanism of this interaction has been examined at the level of binding with human serum albumin (HSA) by the in vitro method. Percentage of binding with HSA, and affinity constants for^99mTc-IODIDA were determined with and without bilirubin. Bilirubin was labeled with^99mTc and its interaction with HSA was also examined.     

Influence of molecular characteristics of nonionic cellulose ethers on their interaction with ionic surfactant investigated by conductometry

The interaction between nonionic derivatives of cellulose, hydroxypropylmethyl cellulose (HPMC) and methyl cellulose (MC), and ionic surfactant, sodium dodecylsulfate (SDS) were investigated by conductometric titration method, at 30°C. Obtained titration curves show two break points: critical aggregation concentration (cac) defined as the concentration of SDS at which interaction starts, and polymer saturation concentration (psp) as the concentration at which interaction finishes. Changes of characteristic concentration breaks were determined in dependence on concentration and molecular characteristics of cellulose derivatives (degree of substitution (DS) and molecular mass, i.e. intrinsic viscosity). It was shown that the first break point, cac, is independent of polymer concentration; while the second break point, psp, increases as polymer concentration increases, as described by a linear correlation. The slopes of linear relationship justify the DS on the intensity of the cellulose derivatives–SDS interaction. Changes in the intrinsic viscosity of cellulose derivatives do not exhibit influence on the interaction with SDS.