Test of conformal gravity with astrophysical observations

Since it can describe the rotation curves of galaxies without dark matter and can give rise to accelerated expansion, conformal gravity attracts much attention recently. As a theory of modified gravity, it is important to test conformal gravity with astrophysical observations. Here we constrain conformal gravity with SNIa and Hubble parameter data and investigate whether it suffers from an age problem with the age of APM~08279+5255. We find conformal gravity can accommodate the age of APM~08279+5255 at 3 $\sigma$ deviation, unlike most of dark energy models which suffer from an age problem.Comment: 6 pages, 2 figure

Next-to-leading order QCD corrections to the top quark decay via the Flavor-Changing Neutral-Current operators with mixing effects

In this paper detailed calculations of the complete $\mathcal{O}(\alpha_s)$ corrections to top quark decay widths $\Gamma(t\to q+V)$ are presented ($V=g,\gamma,Z$). Besides describing in detail the calculations in our previous paper (arXiv:0810.3889), we also include the mixing effects of the Flavor-Changing Neutral-Current (FCNC) operators for $t\to q+\gamma$ and $t\to q+Z$, which were not considered in our previous paper. The results for $t\to q+g$ are the same as in our previous paper. But the mixing effects can either be large or small, and increase or decrease the branching ratios for $t\to q+\gamma$ and $t\to q+Z$, depending on the values of the anomalous couplings ($\kappa^{g,\gamma,Z}_{\mathrm{tq}}/\Lambda$, $f^{g,\gamma,Z}_{\mathrm{tq}}$ and $h^{g,\gamma,Z}_{\mathrm{tq}}$).Comment: 21 pages, 12 figure

Treatment of proliferative diabetic retinopathy by vitrectomy combined with retinal photocoagulation

AIM: To evaluate clinical effect of vitrectomy combined with retinal photocoagulation for proliferative diabetic retinopathy(PDR).<p>METHODS:A retrospective analysis 72 patients(104 eyes)with PDR who underwent vitrectomy, postoperative fundus fluorescein angiography and retinal photocoagulation within 4wk, from July 2009 to November 2012 in our hospital. All the patients were followed up for more than 12mo, analysising the clinical data of preoperative, postoperative, final corrected vision and the operation complications.<p>RESULTS:The increasing rate of visual acuity after retinal photocoagulation(the last retinal photocoagulation)within 1wk was 88.5%(92/104), 1mo was 92.3%(96/104), 3mo was 90.4%(94/104)and one eye had neovascular glaucoma, 6mo was 88.5%(92/104)and one eye had retinal detachment, 12mo was 80.8%(84/104)and 2 eyes with silicone oil emulsification. Along with the development of diabetic retinopathy, the increasing rate of visual acuity declined, complications of silicone oil eye operation increased, especially in eyes with proliferative diabetic retinopathy in phase five or six.<p>CONCLUSION:Vitrectomy combined with retinal photocoagulation in treatment of PDR is effective and safe. Postoperative fundus fluorescein angiography can have a definite object in view of retinal photocoagulation after vitrectomy, which can reduce excessive photocoagulation and prevent light coagulation deficiencies, while improve the visual acuity effectively and reduce the complications