Synthesis and structure of 5-hydrazino- and 5-hydroxyamino-3-aryl-2-pyrazolines and-2-isoxazolines

It was established by the methods of ¹H and ¹³C NMR spectroscopy that the oximohydrazones and bis(hydrazones) of aroylacetic aldehydes exist in the form of the corresponding 5-hydrazino- and 5-hydroxyamino-3-aryl-2-pyrazolines and -2-isoxazolines. The features of the aromatization of these compounds to the corresponding pyrazoles and isoxazoles were studied. Data on the mass-spectral study of the 5-hydroxyamino-2-pyrazoline-5-hydrazino-2-isoxazoline tautomerism in the gas phase are presented.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 927–935, July, 1989.     

Phenomena Affecting the Equilibrium of Al(III) and Zn(II) Extraction with Winsor II Microemulsions

The extraction of Al(III) and Zn(II) from an aqueous solution with two water-in-oil microemulsions, one containing di(2-ethylhexyl)phosphoric acid (DEHPA), was investigated to aid the understanding of the role of the extractant and the metal specific characteristics in the mechanism of microemulsion extraction. The extraction of Al with the DEHPA microemulsion increased by a factor of about 10 with respect to that in the conventional DEHPA system, whereas the extraction of Zn was lower than that in the single DEHPA system. Extraction with the DEHPA-free microemulsion was very low, showing that metal ion solubilization was not important in the mechanism of microemulsion extraction. It is proposed that the effect of the mixed microemulsion on the metal distribution coefficient is the result of the balance between a decrease in the complexation reaction yield due to the interaction between butanol and DEHPA, and the adsorption of the metal complex at the macro- and microinterfaces. The former leads to a decrease in Zn(II) extraction and the latter to Al(III) extraction synergism. Copyright 2000 Academic Press.     

A calorimetric unit for measurements of the thermal effects of reactions in solution

A calorimetric unit for measurements of the thermal effects of reactions in solution was created. The unit was designed following the classic scheme of a hermetic liquid calorimeter working under isoperibolic conditions, it had a thermometric sensitivity of 10⁻⁴ K and a calorimetric sensitivity of 10⁻² J. The accuracy of calorimeter operation was checked against the heats of solution of potassium chloride. The molar integral enthalpies of solution of glycine in water at 298 K were determined.     

Electronic structure and excitations in oligoacenes from ab initio calculations

Oligoacenes C(4n+2)H(2n+4) (n=2,...,6) are studied using a variety of ab initio methods. Density functional theory (DFT) optimized geometries were in good agreement with experiment. Vertical and adiabatic ionization potentials and electron affinities were computed with DFT and it was found that standard exchange-correlation (xc) functionals underestimate ionization potentials in oligoacenes. Possible reasons for this underestimation are discussed. Low lying electronic excitations were computed using time-dependent density functional theory, configuration interaction singles, and configuration interaction singles with approximate treatment of doubles. In agreement with earlier work, time-dependent DFT in conjunction with standard xc-energy functionals substantially underestimates the lowest (p) singlet-singlet electronic transition.     

Analysis of chemical bonding in electronic excited states using parity function

The parity function (Schmider, J Chem Phys 1996, 105, 11134) is a projection of the spin‐traced one‐particle density matrix, which is strongly influenced by chemical bonding and its type. In this article, we apply the Parity Function to analyze chemical bonding in the electronic excited states of some small molecules, computed with the time‐dependent density functional theory. The calculations were carried out within the standard linear combination of atomic orbitals framework. We found that the changes in the parity function upon the excitation can be interpreted in terms of chemically relevant concepts such as bond breaking. We hope that the parity function will become a useful tool for understanding electronic excited states. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Analysis of nonexponential capacitance relaxation signals

The kinetics of charge transfer by deep energy levels of the semiconductor gap, describing nonexponential shape of capacitance relaxation signals, is suggested. A method of analysis of these signals, possessing higher accuracy and resolution in comparison with the conventional methods based on the relaxation-time approximation, is developed.     

机械泵驱动两相回路的实时动态模型分析

在航空航天领域,为了加速系统设计及测试进度,通常需要进行半实物实时仿真,即控制器用实物,受控对象采用数学模型。本文开发出了基于Matlab/Simulink的两相传热模块,并用其搭建了某机械泵驱动两相回路的实时动态模型。通过与实验的对比,验证了模型的可靠性,表明该模型满足实时要求,可以在下一步用于半实物仿真。     

Implementation of a density functional theory-based method for the calculation of the hyperfine A-tensor in periodic systems with the use of numerical and Slater type atomic orbitals: application to paramagnetic defects

The A-tensor parameterizes the "hyperfine" interaction of an "effective" electronic spin with the magnetic field due to the nuclear spin as monitored in an electron paramagnetic resonance (EPR) experiment. In this account, we describe an implementation for the calculation of the A-tensor in systems with translational invariance based on the Kohn-Sham form of density functional theory (KS DFT). The method is implemented in the periodic program BAND, where the Bloch states are expanded in the basis of numerical and Slater-type atomic orbitals (NAOs/STOs). This basis is well-suited for the accurate representation of the electron density near the nuclei, a prerequisite for the calculation of highly accurate hyperfine parameters. Our implementation does not rely on the frozen core approximation tacitly assumed in the pseudopotential schemes. The implementation is validated by performing calculations on the A-tensor for small atoms and molecules within the supercell approach as well as for paramagnetic defects in solids. In particular, we consider the A-tensor of "normal" and "anomalous" muonium defects in diamond and of the hydrogen cyanide anion radical HCN(-) in a KCl host crystal lattice.     

Quantum interference in exciton-Mn spin interactions in a CdTe semiconductor quantum dot

We show theoretically and experimentally the existence of a new quantum-interference effect between the electron-hole interactions and the scattering by a single Mn impurity. The theoretical model, including electron-valence-hole correlations, the short- and long-range exchange interaction of a Mn ion with the heavy hole and with electron and anisotropy of the quantum dot, is compared with photoluminescence spectroscopy of CdTe dots with single magnetic ions. We show how the design of the electronic levels of a quantum dot enables the design of an exciton, control of the quantum interference, and hence engineering of light-Mn interaction.