包装材料阻隔性能测试标准的现状

包装材料对食品、药品安全有很大影响,包装材料的氧气和水蒸气阻隔性能是保护食品等内容物品质的重要因素。本文对现行有效的检测标准进行综述,同时对今后阻隔性能研究的发展方向进行了展望。

Influence of Waste Materials Containing Tungsten on Melting and Crystallization of Glass-ceramics

Influences of waste materials containing tungsten on melting and crystallization of glass-ceramics are discussed in this article. High temperature melting, nucleation and crystallization of glass-ceramics were explored by means of DTA, XRD and SEM. The high temperature melting performance of glass-ceramics ingredients can be effectively improved by mixing the right amount of waste materials containing tungsten. But the additive amount should be properly controlled, the mixing content of waste materials containing tungsten should be a range of 0.5 ~ 2.0 %. In the experiment of glass-ceramics ingredients system, the molten softening temperature of base glass powder reduced about 20 ℃ by adding 1 % waste materials containing tungsten, and the nucleation temperature reduced about 15 ℃. The nucleation and crystallization performance of glass-ceramics mineral crystals can be promoted by mixing the right amount of waste materials containing tungsten. That is helpful to improve the quality of glass-ceramics products.

Electrospun Flexible Nanofibres for Batteries:Design and Application

Flexible and free-standing electrospun nanofibres have been used as electrode materials in electrochemical energy storage systems due to their versatile properties,such as mechanical stability,superb electrical conductivity,and high functionality.In energy storage systems such as metal-ion,metal-air,and metal-sulphur batteries,electrospun nanofibres are vital for constructing flexible electrodes and substantially enhancing their electrochemical properties.The need for flexible batteries has increased with increasing demand for new products such as wearable and flexible devices,including smartwatches and flexible displays.Conventional batteries have several semirigid to rigid components that limit their expansion in the flexible device market.The creation of flexible and wearable batteries with greater mechanical flexibility,higher energy,and substantial power density is critical in meeting the demand for these new electronic items.The implementation of carbon and carbon-derived composites into flexible electrodes is required to realize this goal.It is essential to understand recent advances and the comprehensive foundation behind the synthesis and assembly of various flexible electrospun nanofibres.The design of nanofibres,including those comprising carbon,N-doped carbon,hierarchical,porous carbon,and metal/metal oxide carbon composites,will be explored.We will highlight the merits of electrospun carbon flexible electrodes by describing porosity,surface area,binder-free and free-standing electrode construction,cycling stability,and performance rate.Significant scientific progress has been achieved and logistical challenges have been met in promoting secondary battery usage;therefore,this review of flexible electrode materials will advance this easily used and sought-after technology.The challenges and prospects involved in the timely development of carbon nanofibre composite flexible electrodes and batteries will be addressed.

Synergic Evolution of Microstructure‑Texture‑Stored Energy in Rare‑Earth‑Added Interstitial‑Free Steels Undergoing Static Recrystallization

Synergic evolution of microstructure-texture-stored energy in interstitial-free(IF)steels has been investigated to elaborate the effect of dissolved rare-earth(RE)elements on static recrystallization.Grain size,texture fraction and geometrically necessary dislocation distribution of IF steel samples annealed for different times were compared,suggesting that RE elements could postpone recrystallization nucleation but accelerate grain coarsening.The visco-plastic self-consistent model was primarily adopted and verified,then used to calculate the relative activities of different slip systems.It was proved that the compatible deformation of IF steels was very sensitive to dissolved RE elements,in particular the{110}6<111>2 slip systems became extremely inactive,leading to anα-fibre textures rich configuration of RE-IF steels.Although both IF steels have the same stored energy sequence of whichγ-fibre takes precedence in nucleation followed byα-fibre,the nucleation rates ofα/γ-fibres driven by the reduced stored energy slowed down in RE-IF steels.Further nucleation-path analyses revealed that shear bands withinγ-fibre mainly sacrificed for grain nucleation of{111}<110>orientation,whileα-fibre especially prior grain boundaries therein preferred supplying nucleation sites for{554}<225>grains,which accounting for the competitive growth ofγ-fibre textures in RE-IF steels rather than being dominated by a single orientation.After grain growth,the major texture of Normal-IF steels had been transferred to{554}<225>from{111}<110>,while{554}<225>in RE-IF steels still inherited the orientation advantage and grew up rapidly,thus inducing the grain coarsening.As this work offers a significant understanding of RE microalloying effect on static recrystallization,it will provide references for alloy design and industrial application of IF steels.

Interface regulation strategy of Al-CNTs composite induced by Al-Si eutectic reaction and its strengthening mechanism

Carbon nanotubes(CNTs)reinforced aluminum matrix composites(AMCs)show broad application prospects in the fields of aerospace and transportation because of their lightweight,high specific strength and specific modulus.A new alloying strategy in this study is proposed to regulate its weak intrinsic interface and uncontrollable interfacial reaction.Our results show that Si element could hinder the dissolution and diffusion of carbon atoms in Al matrix,inhibiting Al-CNTs interface reaction.Grain refinement and dislocation increment induced by the reinforcements promote the contributions to the strength of AMCs.The wettability and interface bonding of Al-CNTs could be effectively improved by Al/Si/CNTs composite interface,the formed discontinuous strong interface is advantageous to coordinate the plastic deformation of AMCs.Si particles can also firmly fix CNTs through pinning effect during deformation,which leads to a better load transfer.Therefore,the tensile strength of Al-5Si-0.5CNTs composite can be enhanced up to 391 MPa while maintaining an acceptable plasticity of 7.5%.It brings the strengthening effect of CNTs into full play in AMCs and achieves the strengthening effect of 1+1>2 under the comprehensive effect of grain refinement strengthening,dislocation strengthening,dispersion strengthening of Si particles and load transfer to CNTs。

Development of a widely targeted volatilomics method for profiling volatilomes in plants

Volatile organic compounds play essential roles in plant environment interactions as well as determining the fragrance of plants.Although gas chromatography-mass spectrometry-based untargeted metabolo-mics is commonly used to assess plant volatiles,it suffers from high spectral convolution,low detection sensitivity,a limited number of annotated metabolites,and relatively poor reproducibility.Here,we report a widely targeted volatilomics(WTV)method that involves using a“targeted spectra extraction”algorithm to address spectral convolution,constructing a high-coverage MS2 spectral tag library to expand volatile annotation,adapting a multiple reaction monitoring mode to improve sensitivity,and using regression models to adjust for signal drift.The newly developed method was used to profile the volatilome of rice grains.Compared with the untargeted method,the newly developed WTV method shows higher sensitivity(for example,the signal-to-noise ratio of guaicol increased from 4.1 to 18.8),high annotation coverage(the number of annotated volatiles increased from 43 to 132),and better reproducibility(the number of volatiles in quality control samples with relative standard deviation value below 30.0%increased from 14 to 92 after normalization).Using the WTV method,we studied the metabolic responses of tomato to environmental stimuli and profiled the volatilomes of different rice accessions.The results identified benzothiazole as a potential airborne signal priming tomato plants for enhanced defense and 2-nonanone and 2-heptanone as novel aromatic compounds contributing to rice fragrance.These case studies suggest that the widely targeted volatilomics method is more efficient than those currently used and may considerably promote plant volatilomics studies.

新型争论贪噬菌Variovorax paradoxus S110的细胞色素P450酶的异源表达及催化特性分析

细胞色素P450单加氧酶(Cytochrome P450 monooxygenases)是一种广谱催化剂,可以催化多种类型反应而参与生物体外源物质代谢与天然产物的合成。为丰富P450作为合成生物学的酶元件库,并探索新型催化反应,利用生物信息学手段从争论贪噬菌Variovorax paradoxus S110中挖掘出一种新型电子自供体细胞色素P45(VpMO)单加氧酶,属于CYP116B家族,它可以在大肠杆菌Escherichia coli异源可溶表达。酶学性质研究表明P450VpMO最适pH和最适温度分别为8.0和45℃,并且在温度低于35℃时具有良好的稳定性,Km值为0.458 mmol/L,kcat为2.438 min-1;重要的是重组P450VpMO可以催化一系列包含污染物的含甲氧基底物进行脱甲基反应,其中对4-甲氧基苯乙酮的脱甲基反应转化率高达91%。相比于其他CYP116B家族的P450酶,P450VpMO表现出较强的酶活性,这为后期进一步研究P450VpMO提供了基础。