The possible BπB\pi molecular state and its radiative decay

Recently, several exotic bosons have been confirmed as multi-quark states, but there are violent disputes about their inner structures, namely if they are molecular states or tetraquarks, or even mixtures of the two structures. It would be interesting to experimentally search for non-strange four-quark states with open charm or bottom which are lighter than $\Lambda_c$ or $\Lambda_b$. Reasonable arguments indicate that they are good candidates of pure molecular states $D\pi$ or $B\pi$ because pions are the lightest boson. Both $B\pi$ and $D\pi$ bound states do not decay via strong interaction. The $B\pi$ molecule may decay into $B^*$ by radiating a photon, whereas $D\pi$ molecule can only decay via weak interaction. In this paper we explore the mass spectra of $B\pi$ molecular statesby solving the corresponding B-S equation. Then the rate of radiative decay $|\frac{3}{2},\frac{1}{2}\rangle\to B^*\gamma$ is calculated and our numerical results indicate that the processes can be measured by the future experiment. We also briefly discuss the $D\pi$ case, due to the constraint of the final state phase space, it can only decay via weak interaction.Comment: 12 pages, 3 figures, 3 table

A Complete Reference of the Analytical Synchrotron External Shock Models of Gamma-Ray Bursts

Gamma-ray bursts are most luminous explosions in the universe. Their ejecta are believed to move towards Earth with a relativistic speed. The interaction between this "relativistic jet" and a circum burst medium drives a pair of (forward and reverse) shocks. The electrons accelerated in these shocks radiate synchrotron emission to power the broad-band afterglow of GRBs. The external shock theory is an elegant theory, since it invokes a limit number of model parameters, and has well predicted spectral and temporal properties. On the other hand, depending on many factors (e.g. the energy content, ambient density profile, collimation of the ejecta, forward vs. reverse shock dynamics, and synchrotron spectral regimes), there is a wide variety of the models. These models have distinct predictions on the afterglow decaying indices, the spectral indices, and the relations between them (the so-called "closure relations"), which have been widely used to interpret the rich multi-wavelength afterglow observations. This review article provides a complete reference of all the analytical synchrotron external shock afterglow models by deriving the temporal and spectral indices of all the models in all spectral regimes, including some regimes that have not been published before. The review article is designated to serve as a useful tool for afterglow observers to quickly identify relevant models to interpret their data. The limitations of the analytical models are reviewed, with a list of situations summarized when numerical treatments are needed.Comment: 119 pages, 45 figures, invited review accepted for publication in New Astronomy Review

Long time clinical outcomes of limus-eluting stent versus paclitaxel-eluting stent in patients undergoing percutaneous coronary artery intervention: A meta-analysis of randomized controlled clinical trials

Background: The meta-analysis was aimed to compare the long time (> 2 year) clinical outcomes of limus-based stents (LBS) and paclitaxel-eluting stents (PES). LBS and PES are two kinds of most common coronary artery stents in clinics.Methods: Electronic data bases of PubMed, Cochrane, and EMBASE were searched. We included randomized controlled clinical trials (RCT) comparing LBS and PES with long time clinical outcomes. Methodological quality of eligible trials was assessed using “risk of bias” tool. The efficacy endpoints included target lesion revascularization (TLR), target vessel revascularization (TVR), and stent thrombosis (ST), and the safety endpoints included all cause death, cardiac death, and myocardial infarction (MI). Odds ratios (OR) and 95% confidence intervals (95% CI) were calculated for each endpoint.Results: A total of 23 RCTs and 19,319 participants were included and analyzed in this meta-analysis. All trials were of an acceptable quality. At 2 years, LBS showed reduced risk of revascularization and ST (TLR: OR = 0.59, 95% CI 0.44–0.78; TVR: OR = 0.63, 95% CI 0.55–0.71; ST: OR = 0.55, 95% CI 0.41–0.73) and a lower rate of MI (OR = 0.67, 95% CI 0.57–0.79). Subgroup analysis showed that both everolimus-eluting stents and sirolimus-eluting stents had better clinical outcomes compared with PES. The comparisons of 3, 4 and 5 year follow-up results revealed that the clinical outcomes of PES were non-inferior to those of LBS but LBS was associated with reduced risk of MI and ST at 3 years.Conclusions: LBS is associated with better clinical outcomes at 2 years. Both LBS and PES showed similar efficacy and safety at long time period.

Vertical distributions of non-methane hydrocarbons and halocarbons in the lower troposphere over northeast China

Vertical distributions of air pollutants are crucial for understanding the key processes of atmospheric transport and for evaluating chemical transport models. In this paper, we present measurements of non-methane hydrocarbons (NMHCs) and halocarbons obtained from an intensive aircraft study over northeast (NE) China in summer 2007. Most compounds exhibited a typical negative profile of decreasing mixing ratios with increasing altitude, although the gradients differed with different species. Three regional plumes with enhanced VOC mixing ratios were discerned and characterized. An aged plume transported from the northern part of the densely populated North China Plain (NCP; i.e. Beijing-Tianjin area) showed relatively higher levels of HCFC-22, 1,2-dichloroethane (1,2-DCE) and toluene. In comparison, the plume originating from Korea had higher abundances of CFC-12, tetrachloroethene (C2Cl4) and methyl chloride (CH3Cl), while regional air masses from NE China contained more abundant light alkanes. By comparing these results with the earlier PEM-West B (1994) and TRACE-P (2001) aircraft measurements, continuing declining trends were derived for methyl chloroform (CH3CCl3), tetrachloromethane (CCl4) and C2Cl4 over the greater China-northwestern Pacific region, indicating the accomplishment of China in reducing these compounds under the Montreal protocol. However, the study also provided evidence for the continuing emissions of several halocarbons in China in 2007, such as CFCs (mainly from materials in stock) and HCFCs. © 2011 Elsevier Ltd

The Cu induced ultraflat band in the Pb10−x_{10-x}Cux_x(PO4_4)6_6O4_4 (x=0,0.5x=0,0.5)

Based on the first principle calculations, we investigate the geometry and the electronic structures of the lead apatite with and without the Cu doped. Our calculations found that without the Cu doping the lead apatite crystal is an insulator with a flat band above the Fermi lever. Furthermore, our results indicate that by introducing the O1 vacancies would results in the disappear of the flat bands in the undopped crystal. While the Cu is doped forming the LK-99, there exist the ultra-flat bands crossing the Fermi level induced by the doped Cu atoms, which is due to the hybridization between the d states of the Cu atoms and the p states of the fully occupied 1/4 occupied O1 atoms. Moreover, we point out that the hybridization maybe the key for the realization of the room temperature superconductivity for the LK-99, and a possible solutions method to improve the quality of the crystal is proposed. Our work provides a foundation for the future studies on the unique electronic and the superconductivity properties of the LK-99 crystal.Comment: 8 pages, 7 figure

A Keypoint Based Enhancement Method for Audio Driven Free View Talking Head Synthesis

Audio driven talking head synthesis is a challenging task that attracts increasing attention in recent years. Although existing methods based on 2D landmarks or 3D face models can synthesize accurate lip synchronization and rhythmic head pose for arbitrary identity, they still have limitations, such as the cut feeling in the mouth mapping and the lack of skin highlights. The morphed region is blurry compared to the surrounding face. A Keypoint Based Enhancement (KPBE) method is proposed for audio driven free view talking head synthesis to improve the naturalness of the generated video. Firstly, existing methods were used as the backend to synthesize intermediate results. Then we used keypoint decomposition to extract video synthesis controlling parameters from the backend output and the source image. After that, the controlling parameters were composited to the source keypoints and the driving keypoints. A motion field based method was used to generate the final image from the keypoint representation. With keypoint representation, we overcame the cut feeling in the mouth mapping and the lack of skin highlights. Experiments show that our proposed enhancement method improved the quality of talking-head videos in terms of mean opinion score