A mean-field theory which satisfies the electron on-site local constraint in the relevant regime of density for the high-temperature superconductors is developed. Within this approach, the electron spectral function, the electron dispersion, and the electron density of states of copper oxide materials are discussed, and the results are qualitatively consistent with the numerical simulations.

We study the paramagnetic Anderson-Hubbard model using an extension of dynamical mean-field theory (DMFT), known as statistical DMFT, that allows us to treat disorder and strong electronic correlations on equal footing. An approximate nonlocal Green's function is found for individual disorder realizations and then configuration-averaged. We apply this method to two-dimensional lattices with up to 1000 sites in the strong disorder limit, where an atomic-limit approximation is made for the self-energy. We investigate the scaling of the inverse participation ratio at quarterand half-filling and find a nonmonotonic dependence of the localization length on the interaction strength. For strong disorder, we do not find evidence for an insulator-metal transition, and the disorder potential becomes unscreened near the Mott transition. Furthermore, strong correlations suppress the Altshuler-Aronov density of states anomaly near half-filling.

A solid-phase extraction (SPE) procedure with the use of superparamagnetic Fe(3)O(4) nanoparticles as extracting agent was developed for HPLC-ESI-MS/MS analysis. Four most heavily used triazine pesticides (herbicides) were taken as the test compounds. The NPs showed an excellent capability to retain the compounds tested, and a quantitative extraction was achieved within 10min under the testing conditions, i.e. 100 microL NP solution was added to 400 mL sample in a beaker with stirring. After extraction, the superparamagnetic NPs were easily collected by using an external magnet. Very importantly, analytes retained on the Fe(3)O(4) NPs could be quantitatively recovered by dissolving the NPs with an HCl solution, allowing subsequent HPLC-ESI-MS/MS quantification. A capillary HPLC-ESI-MS/MS method with the present NP-based SPE procedure was developed for the determination of triazines including atrazine, prometryn, terbutryn, and propazine. Atrazine-d(5) was used as internal standard. The method had an LOD of 10 pg/mL atrazine, and a linear calibration curve over a range from 30 pg to 50.0 ng/mL. Simultaneous determination of the four triazine pesticides in water samples taken from local lakes was demonstrated.

Motivated by current interest in disordered systems of interacting electrons, the effectiveness of the geometrically averaged density of states, ρg(ω), as an order parameter for the Anderson transition is examined. In the context of finite-size systems we examine complications which arise from finite energy resolution. Furthermore we demonstrate that even in infinite systems a decline in ρg(ω) with increasing disorder strength is not uniquely associated with localization.

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We study the effects of interorbital hopping on orbital fluctuations and Mott-Hubbard metalinsulator transition (MIT) in the two-orbital Hubbard model within the extended linearized dynamical mean-field theory. By mapping the model onto an effective model with different bandwidths through the canonical transformation, we find that at half-filling, the increases of the interorbital Coulomb interaction U ′ and the Hund's coupling J drive the MIT, and the critical Jc for MIT increases with the lift of the inter-orbital hopping integral t ab . Meanwhile at quarter filling and in the strong correlation regime, the system without t ab exhibits MIT with the decreasing of J, and favors the orbital liquid ground state. However, the system transits from metal to insulator with the increasing of t ab , accompanied with the rising of the orbital order parameter. These results show the important role of the interorbital hopping in the orbital fluctuation and orbital ordering.

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