Influences of complex modification of P and RE on microstructure and mechanical properties of hypereutectic Al-20Si alloy

P and RE complex modification of hypereutectic Al-Si alloys was conducted. The influences of P, RE content on the microstructure and mechanical properties of alloys were investigated. The complex modifications of P and RE make the coarse block primary silicon obviously refined and the large needle eutectic silicon modified to the fine fibrous or lamella ones. P mainly refines the primary silicon, but excess P is unfavorable to the refinement of primary silicon. RE can well refine the primary and eutectic silicon, but its modification effect on the eutectic silicon is more obvious. P can repress the modification of RE on the eutectic silicon. The alloys with the additions of 0.08% P and 0.60% RE have the optimal microstructure and the highest mechanical properties. Compared with the unmodified alloy, the primary silicon of alloys can be refined from 66.4 μm to 23.3 μm and the eutectic silicon can be refined from 8.3 μm to 5.2 μm. The tensile strength is improved from 256 MPa to 306 MPa and the elongation is improved from 0.35% to 0.48%.

Room temperature operation of all-solid-state battery using a closo-type complex hydride solid electrolyte and a LiCoO_(2) cathode by interfacial modification

We report on an all-solid-state battery that employs a closo-type complex hydride solid electrolyte and a LiCoO2 cathode.Interfacial modification between the solid electrolyte and cathode with a LiNbO3 buffer layer enables reversible charge-discharge cycling with a cell voltage of 3.9V (vs.Li^+/Li) at room temperature.Electrochemical analyses clarify that the given modification effectively suppresses side reactions at the cathode/solid electrolyte interface.The interfacial resistance is lowered by ca.10 times with a 5 nm thick LiNbO3 buffer layer compared to that without a buffer layer,so that a discharge capacity of 109 mAh g^-1 is achieved.These results suggest that interfacial modification can be a viable approach to the development of high-voltage all-solid-state batteries using closo-type complex hydride solid electrolytes and oxide cathodes.

Surface Modification of Cu-Cr Complex by NIR and MIR Laser

Irradiated by infrared laser, the surface reducibility and adsorbability of Cu-Cr complex could be improved, owing to the interaction of photo-fragmentation and laser texturing. Analyzed by the binding energy spectra and the auger spectra, the valence states of chromium ion and copper ion were+3 and+1 after radiation respectively, which still had the reducibility to release electrons. In contrast with the near-infrared(NIR)1 064 nm and mid-infrared(MIR) 10 600 nm laser at the same average output power of 15 W, the reduced metal percentage in the Cu-Cr complex was obviously distinguished at the depth from nanometer to micron. After chemical plating, the average coating thickness and mean-square deviation of the NIR sample were 11.61 μm and 0.30 for copper layer, and 2.69 μm and 0.08 for nickel layer. The results were much better than those of the MIR sample.

Recent Advances in the Role of the Elongator Complex in Plant Physiology and tRNA Modification: A Review

The Elongator complex is a multifunction protein complex which has been shown to be involved in transcriptional elongation, DNA replication and repair, tubulin and histone acetylation, gene silencing and tranfer RNA uridine modification. The composition of the Elongator complex is found to be highly conserved in eukaryotes, protein homologs of various subunits have been identified in fungi, plant, animal, and human. Remarkably, mutation in genes encoding the Elongator complex structural components all results in defects of transfer RNA wobble uridine modification, and this function of the Elongator complex is also conserved in eukaryotes. The Elongator complex mutants in higher plants have pleiotropic phenotypes including defects in vegetative growth, abiscisic acid hypersensitivity, elevated tolerance to drought and oxidative stress. What is the relationship between the Elongator complex＇s function in nucleoside modification and its activity in other cellular pathways？ This review summarizes the recent advances in study of function of the Elongator complex, in the aspects of cell physiology and molecular biology.

SCIENTIFIC PRINCIPLES FOR MODIFICATION OF WATER-SOLUBLE POLYMERS. FORMATION OF MACROMOLECULAR COMPLEXES

The study of nanosecond dynamics of macromolecules with the lumines-cent methods make it possible to investigate the formation and functioning of polymericcomplexes, polymeric conjugates and macromolecular metal complexes, which are widelyused for solving many practical tasks. The nanosecond dynamics of macromolecules are ahighly sensitive indicator of interpolymer complexes (IPC) formation. It enables us to solvethe problems of studying IPC formation and stability and to investigate the interpolymerreactions of exchange and substitution. The investigation of changes in the rotational mo-bility of globular protein molecules as a whole makes it possible to determine the complexcomposition and its stability, and to control the course of polymer-protein conjugate forma-tion reaction. The nanosecond dynamics of polymers interacting with surfacants' ions (S)are the sensitive indicator of the S-polymer complex formation. A method for determin-ing the equilibrium constants of the S-polymer complex formation was developed on thebasis of the study of polymer chains mobility. It is established that nanosecond dynamicsinfluences the course of chemical reactions in polymer chains. Moreover, the marked effectof the nanosecond dynamics is also revealed in the study of photophysical processes (theformation of excimers and energy migration of electron excitation) in polymers with pho-toactive groups. It was found that the efficiency of both processes increases with increasingthe mobility of side chains, the carriers of photoactive groups.

Spectral Properties and Characterization of the Modified PSⅡ Core Complexes

用组氨酸的特异性修饰剂 (DEPC)对PSⅡ核心复合物进行了化学修饰 ,并对其光谱性质进行了研究。研究结果表明 :修饰后的PSⅡ核心复合物的吸收光谱在红区发生了很大变化 ,随修饰时间的增加 ,6 80nm处的吸收逐渐下降。修饰后的PSⅡ核心复合物的荧光光谱在最初的 1min内出现荧光上升现象 ,然后逐渐下降 ,峰位蓝移。这些研究结果表明 ,组氨酸残基的修饰导致了原初电子供体P6 80结构的破坏 ,并对其功能产生了影响。

Oxalate modification enabled advanced phosphate removal of nZVI:In Situ formed surface ternary complex and altered multi-stage adsorption process

Nano zero-valent iron(nZVI)is a promising phosphate adsorbent for advanced phosphate removal.However,the rapid passivation of nZVI and the low activity of adsorption sites seriously limit its phosphate removal performance,accounting for its inapplicability to meet the emission criteria of 0.1 mg P/L phosphate.In this study,we report that the oxalate modification can inhibit the passivation of nZVI and alter the multi-stage phosphate adsorption mechanism by changing the adsorption sites.As expected,the stronger antipassivation ability of oxalate modified nZVI(OX-nZVI)strongly favored its phosphate adsorption.Interestingly,the oxalate modification endowed the surface Fe(III)sites with the lowest chemisorption energy and the fastest phosphate adsorption ability than the other adsorption sites,by in situ forming a Fe(III)-phosphate-oxalate ternary complex,therefore enabling an advanced phosphate removal process.At an initial phosphate concentration of 1.00 mg P/L,pH of 6.0 and a dosage of 0.3 g/L of adsorbents,OX-nZVI exhibited faster phosphate removal rate(0.11 g/mg/min)and lower residual phosphate level(0.02 mg P/L)than nZVI(0.055 g/mg/min and 0.19 mg P/L).This study sheds light on the importance of site manipulation in the development of high-performance adsorbents,and offers a facile surface modification strategy to prepare superior iron-basedmaterials for advanced phosphate removal.

N,O-Bidentated difluoroboron complexes based on pyridine-ester enolates:Facile synthesis,post-complexation modification,optical properties,and applications

An array of pyridine-ester enolate based organoboron complexes has been designed and synthesized via a one-pot cascade of Pd-catalyzedα-arylation and BF2complexation.The rapid structure-activity relationship(SAR)studies indicated that unsymmetrical N,O-chelated BF2complexes were highly fluorescent in solid state,and exhibited large Stokes shifts,excellent photostability,along with insensitivity to p H.Theα-aryl group could not only modulate the electronic effect but also inhibit the intermolecularπ-πstacking to promote the aggregation-induced emission(AIE)effect.DFT calculations and experiments identified that the intramolecular charge transfer properties of these N,O-chelates could be switched by the modification of substituents,resulting tunable fluorescence wavelengths.Furthermore,post-complexation modification was accomplished,including Suzuki-Miyaura cross-coupling,Buchwald-Hartwig amination,oxidative cleavage,along with a unique triple substitution reaction involving propargyl Grignard reagents.The exemplificative application of dimethylamine substituted boron complex as a reversible acidic vapor sensor was also demonstrated.

代建工程项目管理冲突及化解对策研究——以高校实验楼代建项目为例

长期以来代建制在实验楼等复杂个性项目上施行时,存在“冲突频发并需政府干预”的突出问题,代建制要求和现有流程之间的矛盾,使得项目建设中的工作冲突容易演变为利益冲突,妨碍了代建项目有效推进。文章在解析管理冲突及其原因的基础上,尝试对相关工作流程进行合理修正,从而摆脱“冲突解决依赖政府干预”的境况,以期为代建制的深入推广提供参考。

精细胞中促进组蛋白-鱼精蛋白替换的分子机制研究进展

在精子形成过程中,圆形精子细胞核内染色质中的组蛋白逐渐被鱼精蛋白替代,使染色质凝聚得更为紧凑,奠定成熟精子头部特异形态的结构基础。若组蛋白-鱼精蛋白替换缺陷,将导致精子核凝聚失败,表现出精子形态异常和活力降低,受精困难。研究显示,组蛋白翻译后修饰、瞬时DNA链断裂、DNA链断裂修复和染色质重塑复合体识别等一系列变化都会促进组蛋白-鱼精蛋白的替换,本文从以上几个方面综述了目前对于促进组蛋白-鱼精蛋白替换分子机制的研究进展,以期为雄性不育症的诊断和治疗提供理论基础。

镁改性增强小麦秸秆生物炭对镉的吸附能力:表面络合模型研究

近年来研究改性生物炭有效去除水中重金属成为热门,但使用表面络合模型从微观探讨生物炭对镉的吸附机理鲜见报道。通过MgCl2与小麦秸秆生物炭(WB)共热解制备镁改性生物炭(MgWB)。SEM-EDS、FTIR和BET等表征显示镁成功接枝到生物炭,Mg的质量分数增加了3.97%,生物炭表面新增Mg-O峰且-OH、-C-O峰增强,镁改性未改变小麦秸秆的条状管道主体结构但比表面积降低9.94%。293-313 K的等温吸附曲线表明改性前后生物炭的吸附行为均符合Langmuir模型,MgWB在313 K时最大饱和吸附密度(3.50μmol·m-2)是WB的3.7倍。Boehm滴定实验显示改性使总酸性官能团增加13.4%,其中代表高、中、低亲和型官能团的羟基、内酯基、羧基浓度分别增加4.28%、8.92%和0.178%。电位滴定曲线显示镁改性导致生物炭的pHpzc从9.2降为5.3,不同pH条件下Cd2+的吸附边实验中WB和MgWB吸附率达90%所需pH分别为9和6,结果表明吸附平衡所需pH值与pHpzc有关,且pHpzc的改变会导致生物炭表面位点类型在不同pH条件下的镉吸附差异。利用非静电表面络合模型NEM、以广义复合法进行拟合,最佳参数计算的位点分布曲线显示WB和MgWB的吸附贡献主要为高亲和型位点,该位点与Cd^(2+)的吸附态浓度达到最高值所对应的pH分别为10和7;模型拟合参数pKa和pK≡SOCd+表明镁改性导致生物炭表面官能团的质子化能力降低,与Cd^(2+)的络合能力增强。镁改性可以丰富生物炭表面官能团,通过增加表面位点浓度和降低pHpzc有效改善生物炭对重金属的吸附。本研究在使用非静电表面络合模型拟合中将表面位点类型的吸附贡献与pHpzc结合讨论微观吸附机理,为生物炭-重金属的相互作用提供了一种新的量化手段。

TG酶-壳聚糖复合改性对鱼明胶凝胶特性的影响及初探

鱼明胶(FG)较差的凝胶特性限制了其在生产中的应用,壳聚糖(CS)和谷氨酰胺转氨酶(TG)已被证明可以用于改善FG的凝胶特性。本研究采用CS和TG对FG进行改性,制备了两种不同类型的改性明胶:FGTG、FG-TG-CS。对比研究了两种改性方式对FG凝胶强度、质构特性、流变学性质、荧光强度、红外光谱和体外消化率的影响。结果表明:单一TG改性和复合改性均能显著提高FG的凝胶强度和质构特性。CS添加量为0.7%时,复合改性的FG有最高的凝胶强度和硬度,分别为522.02±0.07 g和11.79±0.30 N。流变结果表明复合改性组有最高的粘度(η50=0.53±0.04 mPa·s)、凝胶点(23.04±0.17℃)和融胶点(31.30±0.25℃)。改性后样品荧光强度降低,且复合修饰组有更高的荧光猝灭效率。傅里叶红外光谱红移表明复合修饰增加了体系中α-螺旋含量,有助于稳定胶体的形成。因此,TG-CS复合修饰可以有效解决FG凝胶特性较弱的缺点。

复合酶改性玉米皮可溶性膳食纤维的工艺优化及理化特性分析

为探究玉米皮可溶性膳食纤维(Soluble Dietary Fiber,SDF)最佳提取工艺及功能特性。本研究以玉米加工副产物玉米皮为原料,采用复合酶法改性提取玉米皮可溶性膳食纤维,通过单因素实验和响应面优化确定最佳工艺参数并对其理化性质进行了研究。结果表明,当纤维素酶添加量为1.5%、木聚糖酶添加量为1%、酶解温度为55℃、酶解时间为150 min时,玉米皮SDF得率达到的最高值为16.64%±0.21%,其溶解度为87.63%±0.43%,持水力为2.87±0.16 g/g,持油力为2.30±0.12 g/g,葡萄糖吸附力为5.32±0.12 mmol/g,体外模拟胃环境(pH2.0)、肠环境(pH7.0)下胆固醇吸附性分别为11.74±0.15、42.93±0.08 mg/g,胆酸钠吸附性分别为15.43±0.17、50.67±0.10 mg/g。研究结果可为玉米皮可溶性膳食纤维的开发利用提供理论参考。

木质素及其衍生物改性沥青

通过官能团、形貌、热稳定性和亲疏水性等参数对比筛选出适用于沥青改性的木质素,采用柠檬酸疏水改性处理对其进行表征分析,探索掺入改性前、后木质素的沥青性能变化规律。结果表明,有机溶剂木质素中含有丰富的羟基、表面较为粗糙、热稳定性和疏水性能较好,最佳条件为疏水改性温度130℃,m(柠檬酸)∶m(有机溶剂木质素)=7∶1,酯化率为28.70%。改性后的有机溶剂木质素羟基含量减少,表面比较粗糙,热稳定性良好,疏水性能增强。掺杂改性后有机溶剂木质素沥青的复数剪切模量提高,相位角减小,抗车辙性能提高。

空化射流联合复合酶法提取豆渣中可溶性膳食纤维工艺优化

目的探究空化射流联合复合酶法对豆渣可溶性膳食纤维(soluble dietary fiber,SDF)得率、抗氧化活性及官能团的影响。方法采用单因素和响应面实验设计优化空化射流联合复合酶法提取工艺条件,测定提取后SDF的1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2-picrylhydrazyl,DPPH)自由基清除率和红外光谱。结果豆渣SDF最佳提取条件为:空化射流处理压力0.3 MPa,复合酶添加量为6%,料液比为1:30(g/mL),豆渣SDF提取率为18.21%;此条件下得到的SDF具有较高的抗氧化活性,在SDF质量浓度为2.5 mg/mL时,对DPPH自由基抑制率为73.06%;红外光谱图显示经联合方法提取的豆渣SDF官能团成分没有发生变化。结论空化射流联合复合酶法可以有效提高豆渣SDF提取率,为提高豆渣应用价值提供理论支撑。

基于JPEG图像的模块化可逆信息隐藏方法

当前的可逆信息隐藏方法为了寻求更好的嵌入性能,通常会基于给定的图像内容对修改模式和嵌入参数作出自适应的调整。然而,通过细化自适应程度或扩大解空间来寻找更优解时,会造成计算复杂度高、时间成本难以承受等问题。为此,提出了一种适用于JPEG图像的模块化可逆嵌入方法来提高自适应寻优的效率。通过比较不同情况下最优解的嵌入性能,对原有的解空间进行优化、筛选,从而生成一个适用于不同图像的通用修改模式集合。每一个修改模式被定义为在多直方图修改框架下的最优嵌入点集合。在嵌入时,为给定的图像内容自适应地从预设的解集中选定合适的修改模式。实验在USC-SIPI数据集上与五个具有代表性的方法进行了比较。相比于同类算法,所提算法可将峰值信噪比提升0.03~1.81 dB。对于文件大小扩展,所提算法的性能结果可比两个经典方法分别减少12.4%和5.1%。实验结果表明,相比于主流经典方法,该方法在含密图像质量和文件大小扩展方面有更好的性能表现,并能以较低的计算复杂度取得与最近的高效方法相近的自适应嵌入效果。

多梳抑制性去泛素化酶复合物的结构与功能及其在血液肿瘤发生发展中的作用

多梳抑制性去泛素化酶(polycomb repressive deubiquitinase,PR-DUB)复合物是多梳蛋白家族的成员之一,通过调节组蛋白修饰参与染色体的表观遗传修饰。多梳抑制性复合物1(polycomb repressive complex 1,PRC1)和PR-DUB复合物通过对H2AK119Ub泛素化与去泛素化修饰调控平衡,保护活性基因免受异常沉默,去泛素化功能与促进基因活化和建立转录允许的染色质状态有关,除此之外还激活增强子并促进双链断裂处DNA损伤修复。附加性梳样1(additional sex comb-like1,ASXL1)作为表观遗传支架组装染色质修饰复合物和转录因子参与表观遗传调控。BRCA1相关蛋白1(BRCA1-associated protein 1,BAP1)作为去泛素化酶去除底物的泛素化修饰。PR-DUB复合物由核心二聚体和其他辅助因子组成,BAP1与ASXL1形成核心二聚体,其他亚基相互作用调节PR-DUB复合物靶向和功能。ASXL1和BAP1是与PR-DUB复合物去泛素化功能最相关的2个亚基,ASXL1的DEUBAD结构域激活BAP1发挥去泛素化作用水解H2AK119Ub1。了解ASXL1和BAP1的结构以及相互作用机制对研究PR-DUB复合物特异性去泛素化作用的机制至关重要。在人类中,PR-DUB复合物成分的突变经常引起多种血液肿瘤。ASXL 1基因突变常导致蛋白质翻译提前结束,大部分是由于C末端PHD结构域缺失导致。目前认为,PR-DUB复合物中突变的ASXL1或BAP1、表观遗传因子以及Akt/mTOR等靶点或信号通路相互作用是促进血液肿瘤发生发展的可能机制。这对于针对潜在的治疗靶点研究开发新的特异性靶向治疗药物至关重要。本文将介绍PR-DUB复合物的结构与功能、作用机制及其在血液肿瘤疾病中的发生,重点就ASXL1和BAP1进行综述,并系统总结了潜在的靶向治疗药物,以期为PR-DUB复合物在血液疾病防治中的研究提供科学参考。

Yeast KEOPS complex regulates telomere length independently of its t6A modification function

In Saccharornyces cerevisiae, the highly conserved Sua5 and KEOPS complex （including five subunits Kael, Bud32, Cgi121, Pccl and Gon7） catalyze a universal tRNA modification, namely N6-threonylcarbamoy- ladenosine （t6A）, and regulate telomere replication and recombination. However, whether telomere regulation function of Sua5 and KEOPS complex depends on the t6A modification activity remains unclear. Here we show that Sua5 and KEOPS regulate telomere length in the same genetic pathway. Interestingly, the telomere length regulation by KEOPS is independent of its t6A biosynthesis activity. Cytoplasmic overexpression of Qri7, a functional counterpart of KEOPS in mitochondria, restores cytosolic tRNA t6A modification and cell growth, but is not sufficient to rescue telomere length in the KEOPS mutant kae1△ cells, indicating that a t6A modification-independent function is responsible for the telomere regulation. The results of our in vitro biochemical and in vivo genetic assays suggest that telomerase RNA TLC1 might not be modified by Sua5 and KEOPS. Moreover, deletion of KEOPS subunits results in a dramatic reduction of telomeric G-overhang, suggesting that KEOPS regulates telomere length by promoting G-overhang generation. These findings support a model in which KEOPS regulates telomere replication independently of its function on tRNA modification.

Development and applications of the quasi‐dynamic triaxial apparatus for deep rocks

The mechanical behaviors of deep rocks have always posed a challenge for the implementation and safe operation of major underground engineering projects.To this end,this study modified the existing mainstream rock mechanics instruments equipped with a dynamic disturbance loading system and developed a second‐generation TFD‐2000/D triaxial instrument.The first‐generation device is equipped with an independent disturbance system and an advanced EDC‐580 all‐digital servo controller,which can apply disturbing load independently,implement the function of cyclic disturbance,and combine dynamic and static disturbances.The instrument was found to be reliable for use in analyzing the damage process of rocks in the disturbance test of marbles.The second‐generation instrument tackles three limitations of the first‐generation instrument:(i)it upgrades the strain measurement system and uses extensometers with linear variable differential transformers to accurately measure deformation;(ii)it uses the self‐balanced chamber to replace the Hoek–Franklin triaxial cell and auto‐balancing triaxial pressure chamber;and(iii)the loading rod is independently equipped with an EDC‐580 all‐digital servo controller,which measures precise loads.The experimental findings confirmed that the second‐generation instrument can be used for rock mechanics testing under cyclic disturbance loading,the disturbance–stress relaxation cycle,and the creep–fatigue cycle.In this sense,the second‐generation instrument can be a useful addition to deep rock mechanical instruments and provide a valuable reference.

电化学脱合金Ti6Al4V基台对人牙龈成纤维细胞的影响

目的探讨电化学脱合金Ti6Al4V基台对人牙龈成纤维细胞(human gingival fibroblasts,HGFs)的影响,为种植基台表面改性设计提供实验依据。方法根据试样不同表面进行分组:NC组(阴性对照,光滑表面无其他处理)、NM-1组(纳米网-1,1 mol/L NaOH电化学脱合金处理1 h,电压2 V)、NM-2组(纳米网-2,5 mol/L NaOH电化学脱合金处理1 h,电压2 V)。扫描电镜(scanning electron microscopy,SEM)观察不同试样表面形貌及HGFs在其表面的黏附状态,接触角测量仪测定试样表面亲水性。CCK-8评估HGFs在不同试样表面的增殖情况;qRT-PCR检测HGFs在不同试样表面Ⅰ型胶原(collagenⅠ,COL1A1)、Ⅲ型胶原(collagenⅢ,COL3A1)、纤连蛋白1(fibronectin 1,FN1)、黏着斑激酶(focal adhesion kinase,FAK)、黏着斑蛋白(vinculin,VCL)、整合素α2(integrinα2,ITGA2)、整合素β1(integrinβ1,ITGB1)等黏附相关基因表达水平;免疫荧光染色,激光共聚焦显微镜(confocal laser scanning microscope,CLSM)观察HGFs在不同试样表面vinculin蛋白表达情况;天狼猩红染色评价HGFs在不同试样表面胶原纤维分泌合成情况。结果SEM观察到NM-1组和NM-2组表面形成有序均一的三维网状结构,网格直径NM-1组约为30 nm,NM-2组约为150 nm;NM-1组和NM-2组对比NC组,水接触角显著下降(P<0.0001);NM-1组细胞增殖能力较NC组显著提高(P<0.01),NM-1组和NM-2组的水接触角及细胞增殖能力差异无统计学意义(P>0.05)。SEM镜下可见HGFs黏附24 h后在各组试样表面均黏附良好,NM-1组和NM-2组细胞与NC组对比伸展面积更大,形态纤长,细胞伪足更发达。qRTPCR结果显示NM-1组中COL1A1、COL3A1、FN1、FAK、VCL等黏附相关基因表达水平显著高于NC组和NM-2组(P<0.01)。vinculin蛋白免疫荧光结果表明,NM-1组vinculin蛋白表达水平最高,单个细胞黏着斑数量最多(P<0.01)。天狼猩红染色结果显示NM-1组胶原纤维分泌合成量最高(P<0.0001)。结论Ti6Al4V经电化学脱合金改性后所构建的三维纳米网状结构有促进HGFs黏附增殖和胶原分泌合成的作用,其中网格直径约为30 nm的NM-1组对HGFs的促进作用明显。