RESUMO
We investigate the dynamics and pattern formation of two ring dark solitons in a two-dimensional binary Bose-Einstein condensate with tunable intercomponent interaction via numerical simulation of the time-dependent Gross-Pitaevskii equation. Both the black and gray ring dark solitons are considered for cases where the modulation frequency of the intercomponent interaction is resonant or nonresonant with the one of the trapping potential. Our results show that in the presence of periodic modulation of the intercomponent interaction not only are the lifetimes of the ring dark solitons largely extended but also their decaying dynamics are dramatically affected. Before snaking instability sets in, new ring dark solitons are formed, and both the numbers and depths of the ring dark solitons exhibit collective oscillations. With the development of instability, the system exhibits different decaying processes, and a variety of decay profiles, such as vortex necklace, distorted octagon, vortex-antivortex ring, and cross, are formed, showing a strong dependence on the modulation frequency of the intercomponent interaction and the initial depth of the ring dark soliton.
RESUMO
Silver nanowires are widely used in catalysts, surface enhanced Raman scattering, microelectronic equipment, thin film solar cells, microelectrodes and biosensors for their excellent conductivity, heat transfer, low surface resistance, high transparency and good biocompatibility. However, the optical nonlinearity of silver nanowires has not been further explored yet. In this paper, three silver nanowire samples with different concentrations are produced via a typical hydrothermal method. Their applications to fiber lasers are implemented to prove the optical nonlinearity of silver nanowires for the first time. Based on three kinds of silver nanowires, the mode-locked operation of fiber lasers is successfully realized. Moreover, the fiber laser based on the silver nanowire with a concentration of 2 mg/L demonstrates the shortest pulse duration of 149.3 fs. The experiment not only proves the optical nonlinearity of silver nanowires, but also has some enlightenment on the selection of the optimum concentration of silver nanowires in the consideration of ultrashort pulse output.
RESUMO
Studies investigating the association between the COL1A1 gene -1997G/T polymorphism and the risk of osteoporosis in postmenopausal women have reported conflicting results. We performed a meta-analysis based on the evidence currently available from the literature to make a more precise estimation of this relationship. We conducted searches of the published literature in the PubMed and Embase databases up to September 2014. We estimated the pooled odds ratios with their 95% confidence intervals to assess the associations using fixed- or random-effect models. Publication bias was investigated by Begg's funnel plot. Meta-analysis was performed using the STATA package version 12.0. No significant association was found between the -1997G/T polymorphism in the COL1A1 gene and osteoporosis risk in the total population analysis (TT vs GG: OR = 1.28, 95%CI = 0.76-2.17; TT vs GT: OR = 1.04, 95%CI = 0.60-1.78; dominant model: OR = 0.84, 95%CI = 0.50-1.40; recessive model: OR = 1.18, 95%CI = 0.84- 1.66). In a subgroup analysis by nationality, the results also showed that no significant associations between the COL1A1 gene -1997G/T polymorphism and osteoporosis risk existed in either Caucasian or Asian populations. No evidence of publication bias was found. In conclusion, the COL1A1 gene -1997G/T polymorphism might not be a risk factor for osteoporosis in postmenopausal women. Further large and well-designed studies are needed to confirm these conclusions.