Adaptive frequency sweep analysis for electromagnetic problems using the Thiele interpolating continued fractions

A direct rational approximation method based on Thiele interpolating continued fractions theory is proposed for fast frequency sweep analysis of electromagnetic problems. And an adaptive algorithm is also formed. Compared with the conventional rational approximation method, the proposed method can get a rational approximation directly without a great number of matrix inverse computations and doesn't need to allocate much memory for high derivatives of the dense impedance matrix. Meanwhile, the computation of surface currents by continued fractions can be sped up as compared with the traditional rational approximation. Numerical simulations for broad band scattering analysis of different shaped objects are discussed to shown the effectiveness of the present method. © 2010 IEEE.published_or_final_versionThe 2nd International Conference on Education Technology and Computer (ICETC 2010), Shanghai, China, 22-24 June 2010. In Proceedings of 2nd ICETC, 2010, v. 5, p. 126-12

Oscillatory thermopower of carbon chains: First-principles calculations

We investigate the thermoelectric transport through carbon chains connected by two Al leads. Using a Landauer-Buttiker-like formula, we calculate the thermopower and thermoconductance of Al-Cn-Al from first principles. We find that the charge transfer plays an important role in the thermoelectric transport. Because of the charge transfer, the thermopower changes sign for even-odd number of carbon atoms. The thermopower and electric conductance as a function of the gate voltage also exhibit oscillatory behaviors with a phase difference of pi/2.published_or_final_versio

Spin pump in the presence of a superconducting lead

We present a theoretical analysis of a spin pump in the presence of a superconducting lead. The spin pump is facilitated by a rotating magnetic field which provides a spin flip mechanism and hence can generate a spin current without an accompanying charge current. Using a nonequilibrium Green's function method, we obtain a general solution of the pumped charge current and spin current in both the adiabatic and non-adiabatic regimes. The numerical results for the charge current and spin current are presented as we vary different system parameters such as the gate voltage, the external magnetic field, and the pumping frequency. We find that for a quantum dot with a single resonant level in line with the Fermi energy of the left normal lead, a pure spin current is generated by a rotating magnetic field at any frequency. We have identified two kinds of photon-assisted processes which dominate at low pumping frequencies and high pumping frequencies, respectively.published_or_final_versio

Exploring the "energy-saving personality traits" in the office and household situation: An empirical study

Behavior-driven energy conservation has been a promising strategy for reducing building energy consumption as well as carbon emissions. With the intention of revealing the impacts of an individual’s personality basis on energy conservation behavioral attitudes and intentions in households and offices, the present study proposes and conducts an experiment in Xi’an, China with two groups for the investigation of such attitudes towards household energy-saving behavior (HESB) and office energy-saving behavior (OESB), respectively. The research adopts structural equation modeling for experiment data analysis. The analysis results suggest that the two personality traits, Agreeableness and Neuroticism, are significantly related to both HESB and OESB attitudes. Especially, agreeable people tend to present stronger energy-saving attitudes, while individuals with higher Neuroticism are less likely to do so. The results indicate that the impacts of these two traits on energy-saving attitude are found to be less influenced by different environment settings. Further, the results find that Extraversion positively influences energy-saving attitude in the office environment, while Openness only significantly works in the household environment. It is hoped that the findings of the present study can provide informative references to energy-saving intervention design as well as further studies on the spillover of pro-environmental behaviors.</jats:p

Properties of plasmoids observed in Saturn’s dayside and nightside magnetodisc

Plasmoid is a key structure for transferring magnetic flux and plasma in planetary magnetospheres. At Earth, plasmoids are key media which transfer energy and mass in the "Dungey Cycle". For giant planets, plasmoids are primarily generated by the dynamic processes associated with “Vasyliunas Cycle”. It is generally believed that planetary magnetotails are favorable for producing plasmoids. Nevertheless, recent studies reveal that magnetic field lines could be sufficiently stretched to allow magnetic reconnection in Saturn’s dayside magnetodisc. In the study, we report direct observations of plasmoids in Saturn’s dayside magnetodisc for the first time. Moreover, we perform a statistical investigation on the global plasmoid electron density distribution. The results show an inverse correlation between the nightside plasmoid electron density and local time, and the maximum plasmoid electron density around prenoon local time on the dayside. These results are consistent with the magnetospheric circulation picture associated with the "Vasyliunas Cycle"

Understanding the nature of "superhard graphite"

Numerous experiments showed that on cold compression graphite transforms into a new superhard and transparent allotrope. Several structures with different topologies have been proposed for this phase. While experimental data are consistent with these models, the only way to solve this puzzle is to find which structure is kinetically easiest to form. Using state-of-the-art molecular-dynamics transition path sampling simulations, we investigate kinetic pathways of the pressure-induced transformation of graphite to various superhard candidate structures. Unlike hitherto applied methods for elucidating nature of superhard graphite, transition path sampling realistically models nucleation events necessary for physically meaningful transformation kinetics. We demonstrate that nucleation mechanism and kinetics lead to $M$-carbon as the final product. $W$-carbon, initially competitor to $M$-carbon, is ruled out by phase growth. Bct-C$_4$ structure is not expected to be produced by cold compression due to less probable nucleation and higher barrier of formation

Activation of Human Stearoyl-Coenzyme A Desaturase 1 Contributes to the Lipogenic Effect of PXR in HepG2 Cells

The pregnane X receptor (PXR) was previously known as a xenobiotic receptor. Several recent studies suggested that PXR also played an important role in lipid homeostasis but the underlying mechanism remains to be clearly defined. In this study, we found that rifampicin, an agonist of human PXR, induced lipid accumulation in HepG2 cells. Lipid analysis showed the total cholesterol level increased. However, the free cholesterol and triglyceride levels were not changed. Treatment of HepG2 cells with rifampicin induced the expression of the free fatty acid transporter CD36 and ABCG1, as well as several lipogenic enzymes, including stearoyl-CoA desaturase-1 (SCD1), long chain free fatty acid elongase (FAE), and lecithin-cholesterol acyltransferase (LCAT), while the expression of acyl:cholesterol acetyltransferase(ACAT1) was not affected. Moreover, in PXR over-expressing HepG2 cells (HepG2-PXR), the SCD1 expression was significantly higher than in HepG2-Vector cells, even in the absence of rifampicin. Down-regulation of PXR by shRNA abolished the rifampicin-induced SCD1 gene expression in HepG2 cells. Promoter analysis showed that the human SCD1 gene promoter is activated by PXR and a novel DR-7 type PXR response element (PXRE) response element was located at -338 bp of the SCD1 gene promoter. Taken together, these results indicated that PXR activation promoted lipid synthesis in HepG2 cells and SCD1 is a novel PXR target gene. © 2013 Zhang et al