The quintessential two-dimensional lattice model that describes the competition between the kinetic energy of electrons and their short-range repulsive interactions is the repulsive Hubbard model. We study a time-reversal symmetric variant of the repulsive Hubbard model defined on a planar lattice: Whereas the interaction is unchanged, any fully occupied band supports a quantized spin Hall effect. We show that at 1/2 filling of this band, the ground state develops spontaneously and simultaneously Ising ferromagnetic long-range order and a quantized charge Hall effect when the interaction is sufficiently strong. We ponder on the possible practical applications, beyond metrology, that the quantized charge Hall effect might have if it could be realized at high temperatures and without external magnetic fields in strongly correlated materials. 相似文献
We designed and synthesized new armed 12-oxacrown-3s bearing oxygen donor arms and forming encapsulated complexes with metal ions. The ISEs based on the single armed 12-oxacrown-3s exhibited Na+ ion selectivity, while the ISE based on the double armed 12-oxacrown-3 exhibited Li+ ion selectivity. The conformational analysis was performed on the free armed 12-oxaciown-3s and the non-encapsulated and the encapsulated armed 12-oxacrown-3 complexes using a semi-empirical method. The conformational analysis indicated that all armed 12-oxacrown-3s structurally prefer the Na+ ion rather than the Li+ ion. Further, it became apparent that the single armed 12-oxacrown-3s without a guest cation have the C3v 12-oxaciown-3 ring and the double armed 12-oxacrown-3 without a guest cation has the bent 12-oxacrown-3 ring. The oxygens except carbonyl oxygens were directed toward the cation center in the structures of the complexes. It was clear that the ether and ester oxygens participate in the sidearm coordination. 相似文献
The analysed substances, procaine and benzocaine, are two anaesthetic agents currently being administered in tablet form, also in the topical (cream, gel, balm) and injectable dosage forms. The TG/DTG/DTA curves were obtained in air at different heating rates. For determination of the heat effects, the DTA curves (in μV) were changed with the heat flow curves (in mW), so that the peak area corresponds to an energy in J g?1 or kJ mol?1. The non-isothermal experiments are preformed to investigate the thermal degradation process of these active substances, both as a solid and are performed in a dynamic atmosphere of air at different heating rates, by heating from room temperature to 500 °C. The kinetic analysis was performed using the TG data in air for the first step of substance’s decomposition at four heating rates: 7, 10, 12 and 15 °C min?1. The data were processed according to an appropriate strategy to the following kinetic methods: Kissinger–Akahira–Sunose, Flynn–Wall–Ozawa, Friedman and NPK, to obtain realistic kinetic parameters, even if the decomposition process is a complex one. Thermal analysis was supplemented using Fourier Transform infrared spectroscopy coupled with the TG device to identify the anaesthetics with any products which may have formed (EGA—the evolved gas analysis). 相似文献
The aim of this paper is to present the comparative kinetics of thermal decomposition of K2[MoO(O2)2(C2O4)] (kalium oxalato-oxo-diperoxo molibdate), respectively Na2[MoO(O2)2(C2O4)] (natrium oxalato-oxo-diperoxo molibdate). The TG data were obtained at different heating rates: β = 2.5, 4, 5, and 10 °C min?1 in air and nitrogen (50 mL min?1), and the TG/DTG data were processed with the following methods: Friedman, Flynn–Wall–Ozawa and modified-NPK method. 相似文献
Journal of Thermal Analysis and Calorimetry - Thermal and crystallographic characterization of one solvent-free bis(iminophosphorane)ethane (BIPE) form and three solvates with acetonitrile (ACN),... 相似文献
The main object of investigations in this work is the study of the various Roman mortars in Drobeta-Turnu Severin, Romania; the results help clarify the technology used for the construction of the studied sites through different thermoanalytical techniques. The first site encompasses the surviving elements of the Danube Bridge built by the Romans at the beginning of the second century AD to help in their conquest of Dacia. The aim is to establish the extent of similarity or difference between the studied samples. Thermal analysis and infrared spectroscopy are used in the study of different mortar samples. This paper highlights the compatibility of the techniques used: XRD for identifying major crystalline phases, FTIR for a more detailed image for the noncrystalline phase composition and TGA for a quantitative determination of volatile phases (especially CO2 and H2O). The analyses carried out on the mortar samples managed to divide the samples into different categories, obtaining very good correlations between the techniques used. The results also indicate that mortar samples from both the bridge and the Roman Castrum are within known values for Roman mortars.