Electronic structure of carbon nanotubes with copper core

The electronic structure of copper-intercalated carbon nanotubes has been studied by quantum-chemical methods. The total and partial densities of states of nanotubes have been calculated by the linear augmented-cylindrical-wave method. The armchair (5,5) nanotubes with one, two, three, and four copper atoms per unit cell have been calculated The introduction of the metal is accompanied by a sharp increase in the density of states at the Fermi level of the nanowire, which determines the concentration of free electrons involved in charge transfer in the nanotube. The 3d electrons of the metal and the carbon shell are nearly equally involved in electron transport in intercalated wires.     

Natural and synthetic manganese minerals

The mineral and microelement composition and structures have been studied and a comparative analysis has been carried out for manganese minerals with the general formula [Mn(O,OH)₂]⁺[R_0.5–1(OH)_21.5] · nH₂O (R = Mn, Na, K, Ni, Co, Ca, and others) that built iron-manganese concretions raised from different areas of the Sea of Okhotsk and the Bering Sea, and their synthetic analogues. The structures of synthetic manganese species were found to better withstand temperature impacts than those of the native minerals studied under the same conditions.     

Standard thermodynamic functions of CaNi0.5Zr1.5(PO4)3 crystalline phosphate in the range of T → 0 to 640 K

The temperature dependence of the heat capacity C _p ^○ = f(T) of CaNi_0.5Zr_1.5(PO₄)₃ crystalline phosphate is studied by precision adiabatic vacuum and differential scanning calorimetry over the temperature range of 7–640 K. Its standard thermodynamic functions C _p ^○ (T), H ^○(T)-H ^○(0), S ^○(T), and G ^○(T)-H ^○(0) for the region T → 0 to 640 K and the standard entropy of formation at T = 298.15 K are calculated from the obtained experimental data. Using data on the low-temperature (30–50 K) heat capacity, the D fractal dimension of phosphate is determined and conclusions about the character of the topology of its structure have been made. The final results are compared to data from thermodynamic investigations of the structurally related crystalline phosphates Zr₃(PO₄)₄, Ni_0.5Zr₂(PO₄)₃, and Ca_0.5Zr₂(PO₄)₃.     

Thermochemistry of solvation of 18-crown-6 ether in binary methanol-acetonitrile solvents

Heat effects of the dissolution of 18-crown-6 ether (18C6) over a wide range of compositions of mixed methanol-acetonitrile solvents are determined via calorimetry at 298.15 K. It is found that passing from methanol to acetonitrile to x _AN = 0.6 mole fraction is accompanied by a sharp increase in the exothermicity of 18C6 solvation. It is concluded that a further increase in the aprotic component of a binary mixture leads to no appreciable changes in the enthalpy of solvation of the macrocycle.     

Effect of water on the temperatures of human immunoglobulin conformation transitions

A differential thermal analysis of native and denaturated human immunoglobulin (G isotype) and mixtures of the native protein with water over the temperature range of 80–570 K is conducted. Temperatures of the protein conformational transitions and the effect of water on them are investigated. The limit of water solubility in the native protein is determined calorimetrically from the enthalpy of excess water phase melting. A physical state diagram of the immunoglobulin-water system over a wide range of temperatures and component concentrations is built and analyzed.     

Oxidation of C60 and C70 fullerites in air

The oxidation of C₆₀ and C₇₀ fullerites and C₆₀/C₇₀ mixture is accompanied by the decomposition of the carbon frameworks of the molecules at annealing temperatures of 250 and 445°C. Fourier-IR and HPLC studies show that the oxidation/decomposition of C₇₀ molecules is more active than that of C₆₀. The stages of fullerite interaction with oxygen while heating in air were determined.     

Sorption of certain isatins on various sorbents under RP-HPLC conditions

The results from chromatographic analysis of biologically active isatin derivatives on hyper-crosslinked polystyrene (HCLPS) and silica gel modified by octadecyl groups (SilC₁₈) are presented. The constants of distribution of sorbates between a mobile phase and the investigated sorbents (K _x ) and the changes in the standard differential molar Gibbs energies of adsorption $(\Delta _a \bar G^\circ )$ are calculated, along with the chromatographic retention-physicochemical property of sorbate dependences. It is found that the equations describing these dependences have high forecasting ability with respect to the values of retention factors of the investigated sorbates.     

Fibroporous polytetrafluoroethylene modified with iron nanoparticles: Structure and electronic and magnetic properties

A method for synthesizing iron-containing nanocomposite based on fibroporous polytetrafluoroethylene (PTFE) is described. Fibroporous PTFE obtained under the radiation of a CO₂ laser on block PTFE is modified in supercritical carbon dioxide (sc CO₂) to form micro- and nanoporous structures. Porous fluoropolymer is treated with a solution of bis(toluene)iron(0) obtained by metal-vapor synthesis (MVS). The composition and structure of iron-containing fluoropolymer is studied by transmission electron microscopy and X-ray photoelectron and Mössbauer spectroscopy. Fe nanoparticles with an average size of 9 nm, consisting of ～30% FeO and ～70% Fe³⁺, are registered in the sample. Fe⁰ nanoparticles are stabilized in fluoropolymer pores and are coated with nanoparticles of nonstoichiometric iron oxides that have superparamagnetic properties.     

Phase equilibria and salting-out effects in a cesium nitrate-triethylamine-water system at 5–25°C

Phase equilibria and critical phenomena in a cesium nitrate-water-triethylamine system in which the constituent binary liquid system is stratified at the lower critical solution temperature (LCST) is studied in a range of 5–25°C by the visual polythermal method. It is found that introducing cesium nitrate into the water-triethylamine system leads to a slight reduction in the LCST (from 18.3 to 16.3°C) and to a decrease in the mutual solubility of the components. The distribution coefficients of triethylamine between aqueous and the organic phases of the monotectic state at different temperatures are calculated. It is found that the salting-out of triethylamine from aqueous solutions by cesium nitrate increases with rising temperature. The results of the salting-out effect of sodium, potassium, and cesium nitrates on a water-triethylamine binary system are compared.     

Enthalpies of dissolution of NaVO3 · 2H2O in aqueous chloric acid and the standard formation enthalpy of the VO 2 + ion

The enthalpies of dissolution of sodium metavanadate dihydrate in aqueous solutions of chloric acid and sodium perchlorate were measured by calorimetry at 298.15 K at ionic strengths of I = 0.3, 0.4, 0.5, 0.6, and 1.0 M. The standard formation enthalpy of the VO ₂ ⁺ ion in aqueous solution was calculated from the resulting experimental data.