聚氨酯硬质泡沫材料的阻燃改性进展

聚氨酯硬泡材料(RPUF)优异的隔热性、低密度和良好的压缩性质使其被广泛用作建筑、汽车、电子电器等领域的隔热保温材料,但RPUF极易燃烧、火焰蔓延速率快、烟毒性大等缺点给人们的生命安全造成了巨大的损失。传统的反应型阻燃聚氨酯硬泡材料阻燃效率低,而添加性阻燃剂与聚氨酯基体不相容而对其制备工艺和力学性能有严重的影响。文中综述了近年来发展的层层自组装(LBL)法、光热固化涂覆法、气凝胶涂覆法等新型的阻燃聚氨酯制备途径,这些方法在保证聚氨酯硬泡材料优异的物理性能基础上能同时提升阻燃效率,制备出高效阻燃RPUF,并展望了未来阻燃聚氨酯的发展趋势与前景。

Femtosecond laser fabrication of nanograting-based distributed fiber sensors for extreme environmental applications

The femtosecond laser has emerged as a powerful tool for micro-and nanoscale device fabrication. Through nonlinear ionization processes, nanometer-sized material modifications can be inscribed in transparent materials for device fabrication. This paper describes femtosecond precision inscription of nanograting in silica fiber cores to form both distributed and point fiber sensors for sensing applications in extreme environmental conditions. Through the use of scanning electron microscope imaging and laser processing optimization,high-temperature stable, Type II femtosecond laser modifications were continuously inscribed,point by point, with only an insertion loss at 1 d B m~(-1) or 0.001 d B per point sensor device.High-temperature performance of fiber sensors was tested at 1000℃, which showed a temperature fluctuation of ±5.5℃ over 5 days. The low laser-induced insertion loss in optical fibers enabled the fabrication of a 1.4 m, radiation-resilient distributed fiber sensor. The in-pile testing of the distributed fiber sensor further showed that fiber sensors can execute stable and distributed temperature measurements in extreme radiation environments. Overall, this paper demonstrates that femtosecond-laser-fabricated fiber sensors are suitable measurement devices for applications in extreme environments.

Low cross-talk optical addressing of trapped-ion qubits using a novel integrated photonic chip

Individual optical addressing in chains of trapped atomic ions requires the generation of many small,closely spaced beams with low cross-talk.Furthermore,implementing parallel operations necessitates phase,frequency,and amplitude control of each individual beam.Here,we present a scalable method for achieving all of these capabilities using a high-performance integrated photonic chip coupled to a network of optical fibre components.The chip design results in very low cross-talk between neighbouring channels even at the micrometre-scale spacing by implementing a very high refractive index contrast between the channel core and cladding.Furthermore,the photonic chip manufacturing procedure is highly flexible,allowing for the creation of devices with an arbitrary number of channels as well as non-uniform channel spacing at the chip output.We present the system used to integrate the chip within our ion trap apparatus and characterise the performance of the full individual addressing setup using a single trapped ion as a light-field sensor.Our measurements showed intensity cross-talk below~10^(-3) across the chip,with minimum observed cross-talk as low as~10^(-5).

On-chip beam rotators,adiabatic mode converters,and waveplates through low-loss waveguides with variable cross-sections

Photonics integrated circuitry would benefit considerably from the ability to arbitrarily control waveguide cross-sections with high precision and low loss,in order to provide more degrees of freedom in manipulating propagating light.Here,we report a new method for femtosecond laser writing of optical-fiber-compatible glass waveguides,namely spherical phase-induced multicore waveguide(SPIM-WG),which addresses this challenging task with three-dimensional on-chip light control.Fabricating in the heating regime with high scanning speed,precise deformation of cross-sections is still achievable along the waveguide,with shapes and sizes finely controllable of high resolution in both horizontal and vertical transversal directions.We observed that these waveguides have high refractive index contrast of 0.017,low propagation loss of 0.14 dB/cm,and very low coupling loss of 0.19 dB coupled from a single-mode fiber.SPIM-WG devices were easily fabricated that were able to perform on-chip beam rotation through varying angles,or manipulate the polarization state of propagating light for target wavelengths.We also demonstrated SPIM-WG mode converters that provide arbitrary adiabatic mode conversion with high efficiency between symmetric and asymmetric nonuniform modes;examples include circular,elliptical modes,and asymmetric modes from ppKTP(periodically poled potassium titanyl phosphate)waveguides which are generally applied in frequency conversion and quantum light sources.Created inside optical glass,these waveguides and devices have the capability to operate across ultra-broad bands from visible to infrared wavelengths.The compatibility with optical fiber also paves the way toward packaged photonic integrated circuitry,which usually needs input and output fiber connections.

Dynamical and allosteric regulation of photoprotection in light harvesting complex Ⅱ

Major light-harvesting complex of photosystemⅡ(LHCⅡ)plays a dual role in light-harvesting and excited energy dissipation to protect photodamage from excess energy.The regulatory switch is induced by increased acidity,temperature or both.However,the molecular origin of the protein dynamics at the atomic level is still unknown.We carried out temperature-jump time-resolved infrared spectroscopy and molecular dynamics simulations to determine the energy quenching dynamics and conformational changes of LHCⅡtrimers.We found that the spontaneous formation of a pair of localα-helices from the 310-helix E/loop and the C-terminal coil of the neighboring monomer,in response to the increased environmental temperature and/or acidity,induces a scissoring motion of transmembrane helices A and B,shifting the conformational equilibrium to a more open state,with an increased angle between the associated carotenoids.The dynamical and allosteric conformation change leads to close contacts between carotenoid lutein 1 and chlorophyll pigment 612,facilitating the fluorescence quenching.Based on these results,we suggest a unified mechanism by which the LHCⅡtrimer controls the dissipation of excess excited energy in response to increased temperature and acidity,as an intrinsic result of intense sun light in plant photosynthesis.

Thouless pumping in disordered photonic systems

Thouless charge pumping protocols provide a route for one-dimensional systems to realize topological transport.Here,using arrays of evanescently coupled optical waveguides,we experimentally demonstrate bulk Thouless pumping in the presence of disorder.The degree of pumping is quite tolerant to significant deviations from adiabaticity as well as the addition of system disorder until the disorder is sufficiently strong to reduce the bulk mobility gap of the system to be on the scale of the modulation frequency of the system.Moreover,we show that this approach realizes near-full-unit-cell transport per pump cycle for a physically relevant class of localized initial system excitations.Thus,temporally pumped systems can potentially be used as a design principle for a new class of modulated slow-light devices that are resistant to system disorder.

Influence ofγ-Fe2O3 nanoparticles doping on the image sticking in VAN-LCD

Image sticking in liquid crystal display(LCD)is related to the residual direct current(DC)voltage(RDCV)on the cell and the dynamic response of the liquid crystal materials.According to the capacitance change of the liquid crystal cell under the DC bias,the saturated RDCV(SRDCV)can be obtained.The response time can be obtained by testing the optical dynamic response of the liquid crystal cell,thereby evaluating the image sticking problem.Based on this,the image sticking of vertical aligned nematic(VAN)LCD(VAN-LCD)with different cell thicknesses(3.8μm and 11.5μm)and different concentrations ofγ-Fe2O3 nanoparticles(0.017 wt.%,0.034 wt.%,0.051 wt.%,0.068 wt.%,0.136 wt.%,0.204 wt.%,and 0.272 wt.%)was evaluated,and the effect of nano-doping was analyzed.It is found that the SRDCV and response time decrease firstly and then increase with the increase of the doping concentration ofγ-Fe2O3 nanoparticles in the VAN cell.When the doping concentration is 0.034 wt.%,theγ-Fe2O3 nanoparticles can adsorb most of the free impurity ions in liquid crystal materials,resulting in 70%reduction in the SRDCV,8.11%decrease in the decay time,and 15.49%reduction in the rise time.The results show that the doping ofγ-Fe2O3 nanoparticles can effectively improve the image sticking of VAN-LCD and provide useful guidance for improving the display quality.

Mapping Multi-factor-mediated Chromatin Interactions to Assess Dysregulation of Lung Cancer-related Genes

Studies on the lung cancer genome are indispensable for developing a cure for lung cancer.Whole-genome resequencing,genome-wide association studies,and transcriptome sequencing have greatly improved our understanding of the cancer genome.However,dysregulation of longrange chromatin interactions in lung cancer remains poorly described.To better understand the three-dimensional(3D)genomic interaction features of the lung cancer genome,we used the A549 cell line as a model system and generated high-resolution chromatin interactions associated with RNA polymerase II(RNAPII),CCCTC-binding factor(CTCF),enhancer of zeste homolog 2(EZH2),and histone 3 lysine 27 trimethylation(H3K27me3)using long-read chromatin interaction analysis by paired-end tag sequencing(ChIA-PET).Analysis showed that EZH2/H3K27me3-mediated interactions further repressed target genes,either through loops or domains,and their distributions along the genome were distinct from and complementary to those associated with RNAPII.Cancer-related genes were highly enriched with chromatin interactions,and chromatin interactions specific to the A549 cell line were associated with oncogenes and tumor suppressor genes,such as additional repressive interactions on FOXO4 and promoter–promoter interactions between NF1 and RNF135.Knockout of an anchor associated with chromatin interactions reversed the dysregulation of cancer-related genes,suggesting that chromatin interactions are essential for proper expression of lung cancer-related genes.These findings demonstrate the 3D landscape and gene regulatory relationships of the lung cancer genome.