Layer-by-layer self-assembly under high gravity field

In the present article, we have developed a facile and rapid method to fabricate a polyelectrolyte multilayer under high gravity field and investigated the difference of mass transfer in the diffusing process between LbL self-assembled technique under high gravity field (HG-LbL) and dipping assembly. Herein, we have employed polyethyleneimine and zinc oxide nanoparticles, which is a well-known UV blocking material with typical absorption properties in the range of 300-400 nm, as building blocks and applied hydrogen bonding as the driving force to construct the multilayer under HG-LbL and dipping assembly. The results show that, compared with dipping assembly, HG-LbL can highly improve the utilization and adsorption efficiency of building blocks by hastening the diffusing process, and meanwhile the resulting multilayer films still achieve comparable quality as those prepared from dipping assembly.     

A Liquid‐Liquid Interface Process for Fabricating TiO2 Nanofiber Membrane with High Photocatalytic Activity

A membrane consisting of TiO₂ nanofibers was successfully fabricated through a simple solvothermal water/n‐hexane interface reaction of tetra‐n‐butyl titanate with NaOH followed by post treatments of acid washing and calcination. Tetra‐n‐butyl titanate reacts with NaOH at the interface to form high‐quality nanofibers with lateral dimensions below 200 nm and longitudinal dimensions of several tens of micrometers. The membrane is formed by the interpenetration and overlapping of the flexible nanofibers and distributed by holes with sizes ranging from several tens of nanometers to several hundreds of nanometers. Because of the porous structure, this nanofiber membrane exhibited a high efficiency in the photodecomposition of dyes in water.     

Quasiparticle states and quantum interference induced by magnetic impurities on a two-dimensional topological superconductor

We theoretically study the effect of localized magnetic impurities on two-dimensional topological superconductor (TSC). We show that the local density of states (LDOS) can be tuned by the effective exchange field m, the chemical potential μ of TSC, and the distance Δr as well as the relative spin angle α between two impurities. The changes in Δr between two impurities alter the interference and result in significant modifications to the bonding and antibonding states. Furthermore, the bound-state spin LDOS induced by single and double magnetic impurity scattering, the quantum corrals and the quantum mirages are also discussed. Finally, we briefly compare the impurities in TSC with those in topological insulators.     

Gain and transmission properties of a probe field in a four-level atomic system

We theoretically investigate the absorption–amplification response of the probe field in a four-level cold ⁸⁷Rb atomic system. It is found that the incoherent pumping fields play very important roles in realizing the amplification of the probe field. The transmission property of the probe field is also studied.     

Semi-analytical analysis of the isolation to moving-load induced ground vibrations by trenches on a poroelastic half-space

A semi-analytical model is proposed to investigate the screening efficiency of trenches to moving-load induced ground vibrations. The ground is modeled as a fully saturated poroelastic half-space governed by Biot's dynamic poroelastic theory. The trenches are obtained by placing three rectangular elastic layers with appropriate width upon the poroelastic half-space. By Helmholtz decomposition, the displacement fields of the elastic layers are decomposed into three scalar potentials. Analytical solutions are obtained based on Fourier transform and Fourier series in the transformed domain. The time-domain results are obtained by the fast Fourier transform (FFT). The different performances of trenches on a saturated poroelastic half-space and a single-phase elastic half-space to the moving load-induced ground vibration are identified. It is found that the discrepancy of the screening efficiencies between the two models becomes significant when the load speed approaches the Rayleigh wave speed of the ground surface. Also, some parametric studies for the screening efficiency of the trench on the poroelastic half-space are presented.     

330 MHz,sub 50 fs Yb: Fiber ring laser

We demonstrate 330 MHz repetition rate operation in a ring cavity Yb:fiber laser with an innovative wavelength-division-multiplexing collimator to raise the repetition rate. The spectral bandwidth of the pulse is 30 nm and the dechirped pulse width is 48 fs. The output power is 70 mW with 600 mW, 975 nm pump laser diode.     

Theory and experiment of flat-top all-fiber comb filter based on two high birefringence fiber Sagnac loop filters

A simple flat-top all-fiber comb filter based on two high birefringence fiber (HBF) Sagnac loop filters is presented. The proposed flat-top comb filter consists of two HBF Sagnac loop filters with two polarization controllers (PCs) and a fiber circulator. According to the theoretical analysis, with proper settings of the polarization state of the PCs, the comb filter can realize flat-top passband and the channel spacing also can be switched when the comb filter is convex spectrum. The 0.3 dB bandwidth of the flat-top passband is 0.49 nm with a free spectral range of 1.4 nm. The maximum extinction ratio is nearly 20 dB. The comb filter with switchable channel spacing can be obtained from 0.7 nm to 1.4 nm.     

Atom localization via controlled spontaneous emission in a five-level atomic system

We investigate the one- and two-dimensional atom localization behaviors via spontaneous emission in a coherently driven five-level atomic system by means of a radio-frequency field driving a hyperfine transition. It is found that the detecting probability and precision of atom localization behaviors can be significantly improved via adjusting the system parameters. More importantly, the two-dimensional atom localization patterns reveal that the maximal probability of finding an atom within the sub-wavelength domain of the standing waves can reach unity when the corresponding conditions are satisfied. As a result, our scheme may be helpful in laser cooling or the atom nano-lithography via atom localization.     

Enhanced homing of mesenchymal stem cells to the ischemic myocardium by ultrasound-targeted microbubble destruction

In recent years, ultrasound-targeted microbubble destruction (UTMD) has been utilised for the targeted delivery of stem cells. We tested the effects of the myocardial micro-environment changes induced by UTMD on promoting the homing of mesenchymal stem cells (MSCs) to the ischemic myocardium. Dogs were randomly divided into two groups and treated with or without UTMD after the establishment of myocardial infarction models. 4,6-diamino-2-phenyl indole (DAPI) labelled MSCs were transplanted via coronary injections 2 weeks after myocardial infarction in both groups. The results from real-time PCR and western blot analyses indicated that the expression of various cytokines in UTMD-treated dogs was much higher than that observed in non-treated dogs. Histopathological findings demonstrate that ultrasound at a frequency of 1 MHz and an intensity of 1.0 W/cm² provoked inflammatory reactions with mild myocardial damage. Myocardial microenvironment changes caused by UTMD may promote the homing of MSCs to the ischemic myocardium. This non-invasive technique may be a promising method for cardiac cell transplantation therapy.     

Efficient femtosecond pulse generation in an all-normal-dispersion Yb:fiber ring laser at 605 MHz repetition rate

We report a 1030 nm-wavelength Yb:fiber laser that produces the shortest/direct output pulse duration (502 fs) among all-normal-dispersion fiber lasers at the highest repetition rate (605 MHz) among the passively fundamentally mode-locked fiber lasers. The laser also exhibits an optical efficiency of 70% at CW and 65% at mode-locking modes.