Bond distortion effects and electric orders in spiral multiferroic magnets

We study in this paper bond distortion effect on electric polarization in spiral multiferroic magnets based on cluster and chain models. The bond distortion break inversion symmetry and modify the $d$-$p$ hybridization. Consequently, it will affect electric polarization which can be divided into spin-current part and lattice-mediated part. The spin-current polarization can be written in terms of $\vec{e}_{i,j}\times(\vec{e}_{i}\times\vec{e}_{j})$ and the lattice-mediated polarization exists only when the M-O-M bond is distorted. The electric polarization for three-atom M-O-M and four-atom M-O$_{2}$-M clusters is calculated. We also study possible electric ordering in three kinds of chains made of different clusters. We apply our theory to multiferroics cuprates and find that the results are in agreement with experimental observations.Comment: 14 pages, 11 figure

A new approach to automated retinal vessel segmentation using multiscale analysis

Author name used in this publication: David ZhangRefereed conference paper2006-2007 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe

Full one-loop QCD and electroweak corrections to sfermion pair production in γγ\gamma \gamma collisions

We have calculated the full one-loop electroweak (EW) and QCD corrections to the third generation scalar-fermion pair production processes $e^+e^- \to \gamma \gamma \to \tilde{f_i}\bar{\tilde{f_i}} (f=t,b,\tau)$ at an electron-positron linear collider(LC) in the minimal supersymmetric standard model (MSSM). We analyze the dependence of the radiative corrections on the parameters such as the colliding energy $\sqrt{\hat s}$ and the SUSY fundamental parameters $A_f$, $\tan \beta$, $\mu$, $M_{SUSY}$ and so forth. The numerical results show that the EW corrections to the squark-, stau-pair production processes and QCD corrections to the squark-pair production processes give substantial contributions in some parameter space. The EW relative corrections to squark-pair production processes can be comparable with QCD corrections at high energies. Therefore, these EW and QCD corrections cannot be neglected in precise measurement of sfermion pair productions via $\gamma\gamma$ collision at future linear colliders.Comment: to be appeared in Phys. Rev.

The Effects of Ultra-high Pressure Treatment on the Phenolic Composition of Red Wine

Wine is usually aged in oak barrels. In this study, young red wines were treated with ultra-high pressure(UHP) to stimulate the ageing process. Changes in phenolic acids, flavan-3-ols and proanthocyanidinswere determined by reverse-phase high pressure liquid chromatography (RP-HPLC). The concentrationof phenolic acids increased, while the levels of flavan-3-ols decreased. The content and structure ofproanthocyanidins also changed and the tendency was similar to that of natural ageing

Generation and Focusing of Orbital Angular Momentum Based on Polarized Reflectarray at Microwave Frequency

A novel polarized reflectarray is designed, fabricated, and experimentally characterized to show its flexibility and efficiency to control wave generation and focusing of orbital angular momentum (OAM) vortices with desirable OAM modes in the microwave frequency regime. In order to rigorously study the generation and focusing of OAM, a versatile analytical theory is proposed to theoretically study the compensation phase of reflectarray. Two prototypes of microwave reflectarrays are fabricated and experimentally characterized at 12 GHz: one for generation and one for focusing of OAM-carrying beams. Compared with the OAM-generating reflectarray, the reflectarray for focusing OAM vortex can significantly reduce the beam diameter, and this can further improve the transmission efficiency of the OAM vortex beams. We also show that the numerical and experimental results agree very well. The proposed design method and reflectarrays may spur the development of new efficient approaches to generate and focus OAM vortex waves for applications to microwave wireless communications