Few-Body Systems Composed of Heavy Quarks

Within the past ten years many new hadrons states were observed experimentally, some of which do not fit into the conventional quark model. I will talk about the few-body systems composed of heavy quarks, including the charmonium-like states and some loosely bound states.Comment: Plenary talk at the 20th International IUPAP Conference on Few-Body Problems in Physics, to appear in Few Body Systems (2013

Electric field tunable multi-state tunnel magnetoresistances in 2D van der Waals magnetic heterojunctions

Magnetic tunnel junction (MTJ) based on van der Waals (vdW) magnetic layers has been found to present excellent tunneling magnetoresistance (TMR) property, which has great potential applications in field sensing, non-volatile magnetic random access memories, and spin logics. Although MTJs composed of multilayer vdW magnetic homojunctions have been extensively investigated, the ones composed of vdW magnetic heterojunction is still to be explored. Here we use first-principles approaches to reveal that the magnetic heterojunction MTJs have much more distinguishable TMR values than the homojunction ones. In the MTJ composed of bilayer CrI3/bilayer Cr2Ge2Te6 heterojunction, we find there are eight stable magnetic states, leading to seven distinguishable electronic resistances. As a result, six sizable TMRs larger than 600% can be obtained (the maximum TMR is up to 120,000%). The number of distinguishable memories is more than two times larger than that of a four-layered homojunction MTJ. The underlying relationships among magnetic state, spin-polarized band structures, and transmission spectrums are further revealed to explain the multiple TMR values. We also find that the magnetic states and thus TMRs can be efficiently modulated by an external electric field. This study opens an avenue to the design of high-performance MTJ devices based on vdW heterojunctions.Comment: 6 figure

Rare case of magnetic Ag3+^{3+} ion: double perovskite Cs2_{2}KAgF6_{6}

Normally $4d$ or $5d$ transition metals are in a low-spin state. Here using first-principles calculations, we report on a rare case of a high-spin $S$=1 magnetic state for the Ag$^{3+}$ ion in the double perovskite Cs$_{2}$KAgF$_{6}$. We also explored a possibility of a conventional low-spin $S$=0 ground state and find an associated tetragonal distortion to be 0.29 {\AA}. However, the lattice elastic energy cost and the Hund exchange loss exceed the e$_{g}$ crystal-field energy gain, thus making the low-spin tetragonal structure less favorable than the high-spin cubic structure. We conclude that the compact perovskite structure of Cs$_{2}$KAgF$_{6}$ is an important factor in stabilizing the unusual high-spin ground state of Ag$^{3+}$.Comment: 6 pages, 6 figures, accepted for publication in PR

Increased vascular endothelial growth factor (VEGF) expression in rats with spinal cord injury by transplantation of bone marrow stromal cells

Vascular endothelial growth factor (VEGF), a well known angiogenic factor, has been shown to have direct and/or indirect influence on spinal cord injury (SCI). The purpose of this study is to observe VEGF expression changes in rats with SCI by bone marrow stromal cells (BMSCs) treatment. The mRNA expression of VEGF in rats was analyzed by semi-quantitative RT- PCR and the protein expression level was quantified by means of western blot and immunohistochemistry technology. It was found that VEGF was significantly up-regulated in BMSCs treatment group in comparison to the sham group and DMEM group on mRNA level. On protein level, VEGF was also highly increased in BMSCs treatment group, which reached the highest level after 14 days treatment. The present study suggests a potential local role for VEGF as mediators of SCI which might provide a certain reasonable clue to clarify molecular mechanisms of BMSCs treatment in SCI.Key words: Vascular endothelial growth factor (VEGF), spinal cord injury, bone marrow stromal cells, reverse transcription-polymerase chain reaction (RT-PCR), western blot, immunohistochemistry

Robust optimization in HTS cable based on DEPSO and design for six sigma

The non-uniform AC current distribution among the multi-layer conductors in a high-temperature superconducting (HTS) cable reduces the current capacity and increases the AC loss. In this paper, Particle swarm optimization coupled with differential evolution operator (DEPSO) has been applied in structural optimization of HTS cables. While the existence of fluctuation in design variables or operation conditions has a great influence on the cable quality, in order to eliminate the effects of parameter perturbations in design and improve the design efficiency, a robust design method based on design for six sigma (DFSS) is applied in this paper. The optimization solutions show that the proposed optimization procedure can not only achieve a uniform current distribution, but also improve significantly the reliability and robustness of the HTS cable quality. © 2008 IEEE

The molecular systems composed of the charmed mesons in the HSˉ+h.c.H\bar{S}+h.c. doublet

We study the possible heavy molecular states composed of a pair of charm mesons in the H and S doublets. Since the P-wave charm-strange mesons $D_{s0}(2317)$ and $D_{s1}(2460)$ are extremely narrow, the future experimental observation of the possible heavy molecular states composed of $D_s/D_s^\ast$ and $D_{s0}(2317)/D_{s1}(2460)$ may be feasible if they really exist. Especially the possible $J^{PC}=1^{--}$ states may be searched for via the initial state radiation technique.Comment: 42 pages, 4 tables, 31 figures. Improved numerical results and Corrected typos

Optical loss compensation in a bulk left-handed metamaterial by the gain in quantum dots

A bulk left-handed metamaterial with fishnet structure is investigated to show the optical loss compensation via surface plasmon amplification, with the assistance of a Gaussian gain in PbS quantum dots. The optical resonance enhancement around 200 THz is confirmed by the retrieval method. By exploring the dependence of propagation loss on the gain coefficient and metamaterial thickness, we verify numerically that the left-handed response can endure a large propagation thickness with ultralow and stable loss under a certain gain coefficient.Comment: 6 pages with 4 figure