Phenolic profiling reveals the metabolite basis of flesh colour and fresh-cut browning in apple fruit

Flesh colour, which is affected by cultivars and browning, can largely impact consumer acceptance in fresh-cut apples. The study profiled phenolic metabolites from apple flesh of twenty-three cultivars by widely targeted metabolomics. Comparison among white- and yellow-fleshed cultivars showed fifteen phenolics, mainly quercetin 3-O-glucoside, hyperoside, hesperetin 5-O-glucoside and cymaroside, in white-fleshed apples were significantly higher than those in yellow-fleshed apples. It may indicate a metabolite basis of yellow and white flesh colour, and better potential nutrition in white-fleshed apples. In addition, ten phenolic metabolites including five cyanidin glycosides showed significant differences between the highest and the lowest browning groups, indicating them may be crucial in browning of fresh-cut apple. This work elucidates the differences of phenolic profiles among apple cultivars with different flesh colour and provides useful data to evaluate the suitability of apple for fresh-cut processing.     

红外辐射联合回火与冷激杀菌技术对胡萝卜粉品质的影响

首先研究不同红外辐射温度(100,110,120℃)及辐射时间(2.5,5,10 min)对胡萝卜粉微生物及品质的影响,然后根据栅栏效应原理研究红外辐射-回火、红外辐射-冷激联合杀菌对胡萝卜粉微生物、色调值、类胡萝卜素含量等品质的影响。结果表明:100℃、10 min的红外辐射处理使细菌和真菌分别降低了1.9 lg(CFU/g)和2.32 lg(CFU/g),110℃、5 min的红外辐射处使细菌和真菌分别降低了1.58 lg(CFU/g)和2.57 lg(CFU/g)。在上述两种处理条件下胡萝卜粉的水分活度从0.238分别降至0.123和0.147,胡萝卜粉中总类胡萝卜素含量从308.8μg/g降至227.8μg/g和238.8μg/g,色差值(ΔE)为9.11和7.89。与红外辐射单独作用相比,联合回火后的处理没有显著影响细菌数目,处理后保持在5.40~5.80 CFU/g,霉菌、酵母数却在处理过程中显著减少,然而减少量较低,总数仍不低于4.5 lg(CFU/g)。红外辐射-冷激联合处理相比红外辐射单独处理,100℃、10 min联合冷激7 d处理可将细菌数量降低0.25 lg(CFU/g),可将霉菌与酵母数量降低0.28 lg(CFU/g),110℃、5 min联合冷激7 d处可将细菌数量降低0.26 lg(CFU/g),可将霉菌、酵母数量降低0.40 lg(CFU/g),且这些处理下胡萝卜粉的色调值、水分活度、类胡萝卜素含量变化不显著。本试验结果表明,红外辐射-冷激处理具有协同效应,且处理过程中胡萝卜粉的色调值及总类胡萝卜素含量不受影响,这为低水分粉体食品红外辐射联合杀菌提供了参考。     

Microstructure and mechanical behavior of laser aided additive manufactured low carbon interstitial Fe49.5Mn30Co10Cr10C0.5 multicomponent alloy

Laser aided additive manufacturing(LAAM)was used to fabricate bulk Fe49.5Mn30Co10Cr10C0.5 interstitial multicomponent alloy using pre-alloyed powder.The room temperature yield strength(σy),ultimate tensile strength(σUTS)and elongation(εUST)were 645 MPa,917 MPa and 27.0％respectively.The as-built sample consisted of equiaxed and dendritic cellular structures formed by elemental segregation.These cellular structures together with oxide particle inclusions were deemed to strengthen the material.The other contributing components include dislocation strengthening,friction stress and grain bound-ary strengthening.The high εUTS was attributed to dislocation motion and activation of both twinning and transformation-induced plasticity(TWIP and TRIP).Tensile tests performed at-40℃and-130℃demonstrated superior tensile strength of 1041 MPa and 1267 MPa respectively.However,almost no twinning was observed in the fractured sample tested at-40℃and-130℃.Instead,higher fraction of strain-induced hexagonal close-packed(HCP)ε phase transformation of 21.2％were observed for fractured sample tested at-40℃,compared with 6.3％in fractured room temperature sample.     

Identification of the Primary Factors Determining the Specificity of Human VKORC1 Recognition by Thioredoxin-Fold Proteins

Redox (reduction–oxidation) reactions control many important biological processes in all organisms, both prokaryotes and eukaryotes. This reaction is usually accomplished by canonical disulphide-based pathways involving a donor enzyme that reduces the oxidised cysteine residues of a target protein, resulting in the cleavage of its disulphide bonds. Focusing on human vitamin K epoxide reductase (hVKORC1) as a target and on four redoxins (protein disulphide isomerase (PDI), endoplasmic reticulum oxidoreductase (ERp18), thioredoxin-related transmembrane protein 1 (Tmx1) and thioredoxin-related transmembrane protein 4 (Tmx4)) as the most probable reducers of VKORC1, a comparative in-silico analysis that concentrates on the similarity and divergence of redoxins in their sequence, secondary and tertiary structure, dynamics, intraprotein interactions and composition of the surface exposed to the target is provided. Similarly, hVKORC1 is analysed in its native state, where two pairs of cysteine residues are covalently linked, forming two disulphide bridges, as a target for Trx-fold proteins. Such analysis is used to derive the putative recognition/binding sites on each isolated protein, and PDI is suggested as the most probable hVKORC1 partner. By probing the alternative orientation of PDI with respect to hVKORC1, the functionally related noncovalent complex formed by hVKORC1 and PDI was found, which is proposed to be a first precursor to probe thiol–disulphide exchange reactions between PDI and hVKORC1.     

Three distinct optical-switching states in phase-change materials containing impurities:From physical origin to material design

Ge2Sb2Tes is the most widely utilized chalcogenide phase-change material for non-volatile photonic applications,which undergoes amorphous-cubic and cubic-hexagonal phase transition under external excitations.However,the cubic-hexagonal optical contrast is negligible,only the amorphous-cubic phase transition of Ge2Sb2Te5 is available.This limits the optical switching states of traditional active dis-plays and absorbers to two.We find that increasing structural disorder difference of cubic-hexagonal can increase optical contrast close to the level of amorphous-cubic.Therefore,an amorphous-cubic-hexagonal phase transition with high optical contrast is realized.Using this phase transition,we have developed display and absorber with three distinct switching states,improving the switching perfor-mance by 50％.Through the combination of first-principle calculations and experiments,we reveal that the key to increasing structural disorder difference of amorphous,cubic and hexagonal phases is to intro-duce small interstitial impurities(like N)in Ge2Sb2Tes,rather than large substitutional impurities(like Ag)previously thought.This is explained by the formation energy and lattice distortion.Based on the impurity atomic radius,interstitial site radius and formation energy,C and B are also potential suit-able impurities.In addition,introducing interstitial impurities into phase-change materials with van der Waals gaps in stable phase such as GeSb4Te7,GeSb2Te4,Ge3Sb2Te6,Sb2Te3 will produce high optical con-trast amorphous-metastable-stable phase transition.This research not only reveals the important role of interstitial impurities in increasing the optical contrast between metastable-stable phases,but also proposes varieties of candidate matrices and impurities.This provides new phase-change materials and design methods for non-volatile optical devices with multi-switching states.     

Precise quantification of the antibacterial activity of chitosan by NB medium neutralizer

In the present research,nutrient broth(NB)medium was identified to be able to neutralize the antibac-terial activity of chitosan and its derivatives.Therefore,an improved test method independent of NB medium was proposed to precisely quantify the antibacterial effectiveness and efficiency of chitosan.The minimum bactericidal concentration(MBC)of chitosan was 60 μg mL-1 against S.aureus and E.coli,and 0.01％(w/v)chitosan could kill 100％of bacteria within 3 min.From another point of view,the neutralizing efficiency of NB could be tripled by adding 25 g L-1 of sodium chloride.Then the neutraliz-ing mechanism of NB medium was ascribed to flocculation between chitosan and protein.Adding extra sodium chloride could significantly reduce the size of floccules,and smaller floccules would lose the ability of binding with bacteria directly,showing higher neutralizing rate on the macro scale.     

Mechanical and dielectric properties of functionalized boron nitride nanosheets/silicon nitride composites

Uniformly dispersed boron nitride nanosheets (BNNSs) reinforced silicon nitride (Si₃N₄) composites were prepared by surface modification assisted flocculation combined with SPS sintering. In order to improve the dispersibility of the BNNSs in the composites, the liquid phase stripped BNNSs are surface functionalized by a two-step covalently modification. The amino-modified BNNSs (NH₂-BNNSs) and Si₃N₄ powders have opposite surface potential, mixed evenly by electrostatic interaction during flocculation. The results showed that mechanical properties of Si₃N₄ composites were obviously enhanced by adding NH₂-BNNSs. The fracture toughness and bending strength of Si₃N₄ composites added 0.75 wt% NH₂-BNNSs were increased by 34% and 28%, respectively, compared with monolithic Si₃N₄. Toughening mechanisms are synergistic action of the torn, pull-out or bridging of BNNSs and crack deflection mechanisms with microstructural analyzes. The dielectric properties of the Si₃N₄ ceramics are also improved after the addition of NH₂-BNNSs.     

浅谈液压夹具在转向油缸铸造缸盖加工上的应用

随着液压夹具在机械加工中运用推广,该公司引用液压夹具多年来取得一定成效,文章针对转向油缸的铸造缸盖铣、钻序前后加工工装进行对比分析,重点突出应用全自动液压夹具后可提升装夹效率、加工质量以及降低劳动强度等,可以在不添置设备的情况下,满足产能提升的需求。     

河南某赤褐铁矿石选矿工艺比较试验

河南某难选赤褐铁矿石铁品位达4038%，主要脉石成分SiO2含量为1563%，有害元素硫、磷含量均不高；矿石中的铁主要是赤褐铁，其次是硅酸铁、硫化铁，磁性铁含量很低。为探索该矿石可能的开发利用工艺，进行了多种选矿工艺研究。结果表明：直接正浮选、直接反浮选、焙烧—弱磁选工艺均不能有效提高精矿铁品位；矿石采用焙烧—磨矿—弱磁选工艺处理，在矿样与焦炭粒度均为-2 mm，质量比为100∶4，800 ℃焙烧60 min，焙砂磨选细度为-0074 mm占90%，弱磁选磁场强度为4538 kA/m的情况下，可获得铁品位为5584%、回收率为8922%的铁精矿；该精矿经再磨—弱磁精选，在再磨细度为-0074 mm为98%，弱磁精选磁场强度为3404 kA/m的情况下，可获得铁品位为5637%、回收率为8893%的铁精矿。