异佛尔酮二异氰酸酯反应增容聚己二酸-对苯二甲酸丁二酯/聚乳酸生物降解阻隔膜的结构与性能

以异佛尔酮二异氰酸酯(IPDI)为聚己二酸-对苯二甲酸丁二酯/聚乳酸(PBAT/PLA)共混物的增容剂,通过熔融共混法制备了PBAT/PLA/IPDI共混粒子并吹制得到薄膜。采用红外光谱、扫描电镜、差示扫描量热分析、拉伸试验、热重分析和水蒸气透过率测试等研究了不同含量IPDI对共混薄膜形态结构、结晶性能、力学性能、热性能和阻隔性能的影响。结果表明,IPDI的异氰酸酯基团能与PBAT和PLA发生化学反应,分散相尺寸变小,两相界面变得模糊,有效改善了共混物的相容性。随着IPDI含量的增加,共混物中PBAT的结晶度升高,薄膜的拉伸强度逐渐增大,水蒸气阻隔性能呈现先增大后减小的趋势。当IPDI质量分数为0.5%时,PBAT/PLA/IPDI薄膜的横纵向拉伸强度相较于纯PBAT/PLA薄膜分别提升了74.2%和28.6%,断裂伸长率维持在790%和244%,水蒸气透过率降低了38.2%,表现出良好的力学和水蒸气阻隔等综合性能。

Progress in flexible perovskite solar cells with improved efficiency

Perovskite solar cell has emerged as a promising candidate in flexible electronics due to its high mechanical flexibility,excellent optoelectronic properties,light weight and low cost.With the rapid development of the device structure and materials processing,the flexible perovskite solar cells(FPSCs)deliver 21.1%power conversion efficiency.This review introduces the latest developments in the efficiency and stability of FPSCs,including flexible substrates,carrier transport layers,perovskite films and electrodes.Some suggestions on how to further improve the efficiency,environmental and mechanical stability of FPSCs are provided.Specifically,we considered that to elevate the performance of FPSCs,it is crucial to substantially improve film quality of each functional layer,develop more boost encapsulation approach and explore flexible transparent electrodes with high conductivity,transmittance,low cost and expandable processability.

Seedling defoliation of cereal crops increases peanut growth and yield in an intercropping system

Intercropping cereals and legumes is practiced widely in the world for improving yields and economic benefits. Shorter legume crops in intercropping are shaded by taller cereals, substantially reducing legume growth and yield. Reducing shade in intercropping by shortening the plant height of cereals by seedling defoliation has been proposed as a practical approach to increase crop yields and land productivity. A two-year field experiment was conducted to investigate the effect of defoliation of cereal crops at seedling stage on the growth and yield of peanut(Arachis hypogaea L.) intercropped with corn(Zea mays L.) or millet(Setaria italica L.). In comparison with non-defoliation controls, defoliation reduced final plant height by 29 cm on average for corn and 18 cm for millet. Photosynthetically active radiation on peanut in intercropping systems with corn or millet intercropping was respectively 27.0% and 22.8% higher than those in controls, significantly improving the light environment of intercropped peanut. Net photosynthetic rates of peanut were on average 25.5% higher in corn and peanut intercropping and 19.6% higher in millet and peanut intercropping than those in non-defoliation controls. Total biomass of intercropped peanut increased owing to increased root growth. Across two years, yield of peanut intercropped with corn was 27.7% and with millet 32.8% higher than those of controls. Defoliation of cereal crops did not affect corn yield but significantly decreased millet yield by 24.5%. Our results suggest that applying seedling defoliation in intercropped corn could increase peanut yield without compromising corn yield in an intercropping system.

Engineered microorganisms and enzymes for efficiently synthesizing plant natural products

Plant natural products are a kind of active substance widely used in pharmaceuticals and foods.However,the current production mode based on plant culture and extraction suffer complex processes and severe concerns for environmental and ecological.With the increasing awareness of environmental sustainability,engineered microbial cell factories have been an alternative approach to produce natural products.Many engineering strategies have been utilized in microbial biosynthesis of complex phytochemicals such as dynamic control and substructure engineering.Meanwhile,Enzyme engineering including directed evolution and rational design has been implemented to improve enzyme catalysis efficiency and stability as well as change promiscuity to expand product spectra.In this review,we discussed recent advances in microbial biosynthesis of complex phytochemicals from the following aspects,including pathway construction,strain engineering to boost the production.

Rotation of dust vortex in a metal saw structure in dusty plasma

By designing a metal saw structure,both negative and positive rotations of dust vortices are obtained experimentally.With increasing gas pressure,the dust vortex undergoes different spatial distribution from dense dust cloud to dust void,then to dust chain.The transition between the negative and positive rotations of dust vortices is reversible and controllable by changing the gas pressure/input power.The underlying mechanism of this transition is preliminarily explored.

One-dimensional perovskite-based Li-ion battery anodes with high capacity and cycling stability

Perovskite,widely used in solar cells,has also been proven to be potential candidate for effective energy storage material.Recent progress indicates the promise of perovskite for battery applications,however,the specific capacity of the resulting lithium-ion batteries must be further increased.Here,by adjusting the dimensionality of perovskite,we fabricated high-performing one-dimensional hybrid perovskite C_(4)H_(20)N_(4)PbBr_(6) based lithium-ion batteries,with the first specific capacity as high as 1632.8 mAh g^(-1)and a stable specific capacity of 598.0 mAh g^(-1)after 50 cycles under the condition of the constant current density of 150 mA g^(-1).The stable specific capacity is 2.36 times higher than that of the three-dimensional perovskite CH_(3)NH_(3)PbBr_(3)(253.2 mAh g^(-1)),and 1.6 times higher than that of the commercialized graphite electrode(372 mAh g^(-1)).The structure difference and the associated ion diffusivity are revealed to substantially affect the specific capacity of the perovskite-based lithium-ion battery.Our study opens up new directions for the applications of hybrid perovskites in energy storage devices.

Establishing cell suitability for high-level production of licorice triterpenoids in yeast

Yeast has been an indispensable host for synthesizing complex plant-derived naturalcompounds, yet the yields remained largely constrained. This limitation mainly arises from overlookingthe importance of cell and pathway suitability during the optimization of enzymes and pathways. Herein,beyond conventional enzyme engineering, we dissected metabolic suitability with a framework forsimultaneously augmenting cofactors and carbon flux to enhance the biosynthesis of heterogenoustriterpenoids. We further developed phospholipid microenvironment engineering strategies, dramaticallyimproving yeast’s suitability for the high performance of endoplasmic reticulum (ER)-localized, ratelimitingplant P450s. Combining metabolic and microenvironment suitability by manipulating only threegenes, NHMGR (NADH-dependent HMG-CoA reductase), SIP4 (a DNA-binding transcription factor)andGPP1 (Glycerol-1-phosphate phosphohydrolase 1), we enabled the high-level production of 4.92 g/L rarelicorice triterpenoids derived from consecutive oxidation of b-amyrin by two P450 enzymes afterfermentation optimization. This production holds substantial commercial value, highlighting the criticalrole of establishing cell suitability in enhancing triterpenoid biosynthesis and offering a versatileframework applicable to various plant natural product biosynthetic pathways.

Programmable photonic RF filters based on an integrated Fabry-Pérot laser with a saturable absorber

We propose and experimentally demonstrate the programmable photonic radio frequency(RF)filters based on an integrated Fabry-Pérot laser with a saturable absorber(FP-SA).Owing to the high output power and the relative flatness spectrum of the FP-SA laser,only a waveshaper and an erbium-doped fiber amplifier(EDFA)were needed,which can greatly reduce the complexity of the system.The sinc filter employed 87 taps,representing a record-high tap number and resulting in a 3-d B bandwidth of 0.27 GHz and a quality factor of 148.Furthermore,Gaussian apodization enabled the out-of-band rejection of the filter to reach 34 d B and the center frequency to be finely tuned over a wide range,spanning from 4 to 14 GHz.These results indicate that the proposed scheme could provide a promising guideline for the photonic RF filters that demand both high reconfigurability and greatly reduced size and complexity.

隧道技术治疗上前牙黑三角1例

目的本文通过报道上前牙邻面黑三角的治疗过程1例,希望为黑三角的治疗提供新的思路。诊疗经过:患者女性,33岁。上前牙邻面龈乳头退缩1月余。使用隧道技术(tunnel technique,TUN)+结缔组织移植术(connective tissue graft,CTG)联合树脂充填,治疗其上前牙邻面龈乳头退缩,术后随访2年。结果2年后前牙区龈乳头外形丰满,完全充盈邻间隙,美学效果改善明显。结论TUN+CTG联合树脂充填可以治疗前牙区黑三角,其适应证和优缺点还有待进一步临床研究去证明。

Dissimilar laser welding of CrMnFeCoNi high entropy alloy and 316LN stainless steel for cryogenic application

The microstructure and mechanical properties of dissimilar laser beam welded joint between CrMnFeCoNi alloy and 316LN stainless steel was investigated.The results showed that the defect-free dissimilar joint was obtained by laser beam welding.The ultimate strength of the welded joints can reach∼90%of the base materials at both room and cryogenic temperatures.The deformation substructure mainly consisted of planar dislocation,the stacking faults and the dissociation of stacking faults into nanotwins.The volume fraction of the nanotwins was increasing at cryogenic temperature.The hardness fluctuates greatly in welded joint and the lowest hardness was located at fusion zone near the fusion line.The fracture of the welded joint was located at the fusion zone in consistence with the lowest hardness area.It is mainly attributed to the coarse grain and stress concentration at this area.

Microfluidics in cardiovascular disease research: state of the art and future outlook

Due to extremely severe morbidity and mortality worldwide,it is worth achieving a more in-depth and comprehensive understanding of cardiovascular diseases.Tremendous effort has been made to replicate the cardiovascular system and investigate the pathogenesis,diagnosis and treatment of cardiovascular diseases.Microfluidics can be used as a versatile primary strategy to achieve a holistic picture of cardiovascular disease.Here,a brief review of the application of microfluidics in comprehensive cardiovascular disease research is presented,with specific discussions of the characteristics of microfluidics for investigating cardiovascular diseases integrally,including the study of pathogenetic mechanisms,the development of accurate diagnostic methods and the establishment of therapeutic treatments.Investigations of critical pathogenetic mechanisms for typical cardiovascular diseases by microfluidic-based organ-on-a-chip are categorized and reviewed,followed by a detailed summary of microfluidic-based accurate diagnostic methods.Microfluidic-assisted cardiovascular drug evaluation and screening as well as the fabrication of novel delivery vehicles are also reviewed.Finally,the challenges with and outlook on further advancing the use of microfluidics technology in cardiovascular disease research are highlighted and discussed.

Synthesis of dispersed long single-crystalline TiO_2 paste and its application in DSSC as a scattering layer

Ti O2 nanowire(NW) is one of the potential scattering layer materials in dye-sensitized solar cells(DSSCs) owing to its fast electron conductivity and excellent light scattering property resulting from its one-dimensional(1D) morphology. However, Ti O2 NWs used as scattering layers in previous work were either aggregated or shortened into shuttles that cannot use their unique 1D properties. In this paper, we present the preparation of a well-dispersed long NW paste(exceeding 1 ?m) by a mild method and used as a scattering layer in DSSC. The paste achieved a photoconversion efficiency of 5.73% and an efficiency enhancement of 12% compared with commercial scattering layer(P200 paste). Compared with the DSSC without a scattering layer, an efficiency enhancement of 54.9% was achieved. Also, the largest efficiency of 6.89% was obtained after optimization of photoanode thickness. The photoanodes were investigated through dye desorbed experiments and transmission spectra, which suggested that P25 nanoparticles with the as-prepared NW scattering layer loaded more dye than those with P200 paste. These results indicate that well-dispersed long NW paste has a potential application in scattering layers.

The degradation of cathodic Fe/N/C catalyst in PEMFCs:The evolution of remanent active sites after demetallation

The state-of-the-art Fe/N/C catalyst has presented comparable initial cathode performance to the benchmark Pt/C catalyst in proton exchange membrane fuel cells(PEMFCs).However,the major bottleneck is its significant activity decay in real-world PEMFC cells.The superposed“fast decay”and“slow decay”have been well documented to describe the degradation process of Fe/N/C catalysts during PEMFC operation.The fast decay has been well understood in close relation to the demetallation at the initial 15-h stability test.Nevertheless,it is still unclear how the remanent active sites evolve after demetallation.To this end,the catalyst performance and evolution of a typical Fe/N/C active site were herein investigated through postmortem characterizations of the membrane electrode assemblies(MEAs)after different operations.It is presented that 1 bar pressure and 80℃ temperature are the optimized conditions for Fe/N/C MEA.Particularly,the“fast decay”in the initial 15 h is immune to the various operating parameters,while the“slow decay”highly depends on the applied temperature and pressure.According to the X-ray absorption spectra(XAS)analysis and stability test of MEA,the gradual evolution of Fe-N coordination to Fe-O is found correlated with the“slow decay”and accounts for the catalyst decay after the demetallation process.