Transport anisotropy and metal-insulator transition in striped Dirac fermion systems

Using the determinant quantum Monte Carlo method, we investigate the metal-insulator transitions induced by the stripe of charge density in an interacting two-dimensional Dirac fermion system. The stripe will introduce the transport anisotropy and insulating intermediate phase into the system, accompanied by the change of band structure and a peak of density of states around Fermi energy. In the case of strong correlation, stripe exhibits competition with Coulomb repulsion through closing the energy gap and disrupting the magnetic order, and finally drives the system in Mott insulating phase back to the metallic state. Our results may provide a feasible way to modify transport properties by setting charge stripes in experiments.Comment: 8 pages, 9 figure

Evolution of magnetic correlation in an inhomogeneous square lattice

We explore the magnetic properties of a two-dimensional Hubbard model on an inhomogeneous square lattice, which provides a platform for tuning the bandwidth of the flat band. In its limit, this inhomogeneous square lattice turns into a Lieb lattice, and it exhibits abundant properties due to the flat band structure at the Fermi level. By using the determinant quantum Monte Carlo simulation, we calculate the spin susceptibility, double occupancy, magnetization, spin structure factor, and effective pairing interaction of the system. It is found that the antiferromagnetic correlation is suppressed by the inhomogeneous strength and that the ferromagnetic correlation is enhanced. Both the antiferromagnetic correlation and ferromagnetic correlation are enhanced as the interaction increases. It is also found that the effective $d$-wave pairing interaction is suppressed by the increasing inhomogeneity. In addition, we also study the thermodynamic properties of the inhomogeneous square lattice, and the calculation of specific heat provide good support for our point. Our intensive numerical results provide a rich magnetic phase diagram over both the inhomogeneity and interaction

Determination of bupropion hydrochloride in rat plasma by LC-MS/MS and Its application to pharmacokinetic study

A selective and sensitive liquid chromatography-tandem mass spectrometry method was developed and validated for quantitation of bupropion hydrochloride in rat plasma using triazolam as an internal standard. Chromatographic separation was achieved on a SB-C18 column at 30 °C, with 50: 50 (v/v) acetonitrile-0.1 % formic acid in water as mobile phase. The flow rate was 0.3 mL/min. The determination of bupropion was performed in MRM mode, m/z 239.9 → 183.7 for bupropion and m/z 343.0 → 308.0 for triazolam (IS) and positive ion electrospray ionization interface. Calibration curve was linear over range of 1.2 to 480 ng/mL. The intra- and inter-run relative standard deviations of the assay were less than 10 %. The mean absolute recoveries determined at the concentrations of 2.4, 48 and 360 ng/mLwere 91.00%, 92.06%, 91.71%, respectively. The validated method is successfully used to analyze the drug in samples of rat plasma for pharmacokinetic study.Colegio de Farmacéuticos de la Provincia de Buenos Aire

The characteristics analysis and cogging torque optimization of a surface-interior permanent magnet synchronous motor

This paper proposes optimal stator skewed slot analytical method for cogging torque reduction in surface-interior permanent magnet synchronous motor(SIPMSM) and analyzes the characteristics of SIPMSM. The series-parallel equivalent magnetic circuit models(EMCMs) of SIPMSM is built based on the characteristics of magnetic circuits, which is used to design the basic electromagnetic parameters of SIPMSM. Analytical expressions of cogging torque are derived from applying analytical techniques. Stator skewed slot for cogging torque minimum is adopted, and the stator skewed slot pitch is confirmed based on the analytical expressions of the resultant cogging torque. The cogging torque, torque ripple, back electromotive force(back-EMF), power-angle characteristics, efficiency and power factor of SIPMSM are analyzed by establishing 3-dimensional finite element model(3-D-FED) of SIPMSM with stator skewed slot and straight slot. It is shown that the comprehensive performance of optimized SIPMSM is improved as confirmed by finite element analysis and analytical calculation results

Experimental Study on Plugging Behavior of Degradable Fibers and Particulates within Acid-etched Fracture

As proven from field practices in North America and Northwest China, temporary plugging and diverting acid fracturing is an indispensable technology to enhance stimulation effect and hydrocarbon production of complex carbonate reservoirs. It\u27s well-known that the key to the success of this technology lies in creating a temporary plugging within the previously created fractures. Consequently, many scholars have conducted laboratory experiments to investigate the plugging behavior of fibers and particulates. However, the current devices nearly have certain limitations in simulating temporary plugging experiments. Aiming at this problem, this paper introduced the fracture temporary plugging evaluation system with large fracture size, and high-pressure resistance, which can meet the requirement of temporary plugging experiment. In addition, 3D printing technology was used to reproduce the roughness of acid-etched fracture surface, improving the experimental accuracy. Based on the device, a series of experiments were performed to study the effect of carrier fluids type, the injection rate, the fracture width, and the fracture morphology on plugging behavior of fibers and particulates. Experimental results show that the plugging effect of HPG fracturing fluid is better than that of slick water. Moreover, the effect of temporary plugging deteriorates with the decrease of injection rate, which can be attributed to the fact that high injection rate increases the probability of bridging and plugging. When it comes to the fracture width, only fibers have favorable plugging effect under the condition of 2 mm fracture width. However, a single type of temporary plugging agent (only fibers or particulates) cannot achieve effective plugging under the condition of 4 mm fracture width. The combination of fibers and particulates can obtain favorable plugging effect. When the fracture width increases to 6 mm, it\u27s difficult to obtain favorable plugging effect if the diameter of particulates is less than 50% of fracture width. Hence, it is recommended to add big particulates whose diameters are at least 50% of the fracture width to improve the plugging effect. Moreover, the fracture surface morphology affects the formation time of temporary plugging, but does not affect whether temporary plugging is formed or not. This study deepens the understanding the plugging behavior of fibers and particulates within acid-etched fracture and provides fundamental for field treatment design

Determination of bupropion hydrochloride in rat plasma by LC-MS/MS and Its application to pharmacokinetic study

A selective and sensitive liquid chromatography-tandem mass spectrometry method was developed and validated for quantitation of bupropion hydrochloride in rat plasma using triazolam as an internal standard. Chromatographic separation was achieved on a SB-C18 column at 30 °C, with 50: 50 (v/v) acetonitrile-0.1 % formic acid in water as mobile phase. The flow rate was 0.3 mL/min. The determination of bupropion was performed in MRM mode, m/z 239.9 → 183.7 for bupropion and m/z 343.0 → 308.0 for triazolam (IS) and positive ion electrospray ionization interface. Calibration curve was linear over range of 1.2 to 480 ng/mL. The intra- and inter-run relative standard deviations of the assay were less than 10 %. The mean absolute recoveries determined at the concentrations of 2.4, 48 and 360 ng/mLwere 91.00%, 92.06%, 91.71%, respectively. The validated method is successfully used to analyze the drug in samples of rat plasma for pharmacokinetic study.Colegio de Farmacéuticos de la Provincia de Buenos Aire