Chemical bonding in high-temperature YBa2Cu3O7 superconductors

Calculations for clusters serving as models for the electronic structure of the copper, barium, and oxygen sites in high-temperature YBa₂Cu₃O₇ superconductors were carried out in the framework of the discrete variation method. An analysis of the bond orders in such compounds was carried out using the overlap occupancies of various AO of the metal and oxygen atoms. Values were obtained for AO occupancies and effective charges on the atoms in the clusters.Institute of Chemistry, Urals Branch, Academy of Sciences of the USSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 30, No. 5, pp. 12–16, September–October, 1989.     

Angular distribution of 4.43-MeV γ-rays produced in inelastic scattering of 14.1-MeV neutrons by <Superscript>12</Superscript>C nuclei

The work is devoted to measuring the angular distribution of 4.43-MeV γ-rays produced in inelastic scattering of 14.1-MeV neutrons by ¹²C nuclei. A portable ING-27 neutron generator (designed and fabricated at VNIIA, Moscow) with a built-in 64-pixel silicon α-detector was used as a source of tagged neutrons. The γ-rays of characteristic nuclear radiation from ¹²C were detected with a spectrometric system that consisted of 22 γ-detectors based on NaI(Tl) crystals arranged around the carbon target. The measured angular distribution of 4.43-MeV γ-rays is analyzed and compared with the results of other published experimental works.     

Pseudo-four-component synthesis and in silico studies of 5-(5-hydroxy-3-methyl-1H-pyrazol-4-yl)-substituted 5H-chromeno[2,3-b]pyridines

Multicomponent reactions (MCRs) are important processes, in which more than three different reactants directly get converted into one new structure bearing most of the atoms of these reactants. It is a very powerful tool in drug discovery and combinational chemistry. A new pseudo-four-component synthetic approach to 5-(5-hydroxy-3-methyl-1H-pyrazol-4-yl)-substituted 5H-chromeno[2,3-b]pyridines with 68%–95% yields is reported. This MCR opens an efficient and convenient way to substituted 5H-chromeno[2,3-b]pyridines, which are promising compounds in medicinal chemistry and for the treatment of lung cancer through inhibition of aldo-keto reductase 1B10. A new consensus approach of molecular docking and molecular dynamics was applied for the investigation of interaction of synthesized 5H-chromeno[2,3-b]pyridines and aldo-keto reductase 1B10.     

Effective Molecular Dynamics Model of Ionic Solutions for Large-Scale Calculations

A model of ionic solutions is proposed which can be used to calculate aqueous salt solutions in different nanostructures. The interaction potential of the model includes the Lennard-Jones potential and angularly averaged dipole–dipole and ion–dipole interactions. Lennard-Jones potential parameters for different ions are obtained. Characteristics of aqueous solutions at different salt concentrations are calculated using the molecular dynamics method. It is shown that the calculated values of the hydration shells of ions parameters are in good agreement with the theoretical and experimental data at a salt concentration of 1 mol/kg. The computational scheme used in the calculations is described. It is shown that calculations using the proposed model require less computing resources compared with the standard models of ionic solutions.     

Quasi-Isentropic Compressibility of Deuterium at a Pressure of ~12 TPa

An experimental result for the quasi-isentropic compressibility of a strongly nonideal deuterium plasma compressed in a spherical device by the pressure P = 11400 GPa (114 Mbar) to the density ρ ≈ 10g/cm³ has been reported. The characteristics of the experimental device, diagnostic methods, and experimental results have been described. The trajectory of motion of metallic shells compressing a deuterium plasma has been recorded using intense pulsed sources of X rays with the boundary energy of electrons up to 60 MeV. The deuterium plasma density ρ ≈ 10g/cm³ has been determined from the measured radius of the shell at the time of its “stop.” The pressure of the compressed plasma has been determined from gas-dynamic calculations taking into account the real characteristics of the experimental device.     

Helium-3 as a Perspective Fuel for Power Generation through Aneutronic Thermonuclear Fusion

Physics of Atomic Nuclei - The aneutronic D3–He (deuterium–helium-3) fuel cycle is considered as a viable alternative to D–T (deuterium–tritium) fusion since it is...     

Measurement of the compressibility of a deuterium plasma at a pressure of 1800 GPa

The thermodynamic properties of a highly compressed deuterium plasma have been measured using an explosive spherical experimental chamber. The experiment has been performed with an X-ray diffraction complex consisting of three betatrons and a multichannel optoelectronic system of the detection of X-ray images of the process of the explosive spherical compression of deuterium. The density of the shock-compressed deuterium plasma ρ = (4.3 ± 0.7) g/cm³ at the pressure P = 1830 GPa has been detected at the initial pressure of gaseous deuterium P ₀ = 267 atm and the temperature T ₀ = 10.5°C. Under such conditions, the plasma is strongly nonideal (Γ ～ 450) with the degenerate (nλ _e ³ ～ 280) electron component and with an electron density of about 2.8 × 10²³ cm^?3.     

Aluminum hydroxocarboxylates in solution deposition of planarization alumina films

Aluminum hydroxocarboxylates derived from butyric, pivalic, valeric, and isovaleric acids were synthesized and characterized. The synthesized hydroxocarboxylates were suspended in isopropanol and reacted with diethylenetriamine and monoethanolamine, which acted as hydrolyzing and complex-forming agents, to obtain precursor solutions for chemical deposition of smooth amorphous alumina films on metal substrates.     

Stereochemical Effects on 1H Chemical Shifts in 2,3-Diazabicyclo[2.2.1]Hept-2-Ene (DBH), 2,3-Diazabicyclo[2.2.2]Oct-2-Ene (DBO) and Related Molecules

¹H-NMR spectra of DBH (1), DBO (2) and of the synthetic precursor to 1, 1,4-phenyl-2,4,6-triazatricyclo[5.2.1.0^2,6]heplanc-3,5-dione (3), were recorded in acetone-d₆ and C₆D₆ at 500 MHz. Assignment was aided by complete resolution of signals of 1 and 3 in C₆D₆ by aromatic solvent-induced shifts (ASIS). The effect of the change from phenyllriazolinedione to a diazene functional group on the chemical shifts of the exo,endo and syn,anti protons was investigated. The chemical shifts of the exo,endo protons of 1 are exceptionally sensitive to the functional group at the hetero substituted bridge in the DBH skeleton. However, the relative chemical shift of the syn,anti proton pair is independent of the nature of the functional group. The role of stereochemical effects on these chemical shifts is discussed.