Influence of introducing Zr,Ti,Nb and Ce elements on externally solidified crystals and mechanical properties of high-pressure die-casting Al–Si alloy

High pressure die casting(HPDC)AlSi10Mn Mg alloy castings are widely used in the automobile industry.Mg can optimize the mechanical properties of castings through heat treatment,while the release of thermal stress arouses the deformation of large integrated die-castings.Herein,the development of non-heat treatment Al alloys is becoming the hot topic.In addition,HPDC contains externally solidified crystals(ESCs),which are detrimental to the mechanical properties of castings.To achieve high strength and toughness of non-heat treatment die-casting Al-Si alloy,we used AlSi9Mn alloy as matrix with the introduction of Zr,Ti,Nb,and Ce.Their influences on ESCs and mechanical properties were systematically investigated through three-dimensional reconstruction and thermodynamic simulation.Our results reveal that the addition of Ti increased ESCs'size and porosity,while the introduction of Nb refined ESCs and decreased porosity.Meanwhile,large-sized Al_3(Zr,Ti)phases formed and degraded the mechanical properties.Subsequent introduction of Ce resulted in the poisoning effect and reduced mechanical properties.

Electron-withdrawing inductive effects enhanced strategy for protein thiol sensing and blocking agent design

It is a great challenge to discover novel chemical reactions suitable for biological analysis in a living system.The development of novel protein thiol blocking agents is a crucial need for exploring protein thiol functions in protein refolding,signal transduction,and redox regulation.We are always keen on seeking novel chemical reactions applied to endogenous biological macromolecules or protein thiol sensing,blocking,and labeling.In the present work,we have successfully developed a novel agent to block protein thiol by enhanced electron-withdrawing inductive effects.This sensing and blocking process was detailedly monitored by UV-vis,fluorescent spectra,and SDS-Page gel separation.The spectral studies demonstrated that the agent could react ultrafastly with thiol within seconds atμM level.Furthermore,fluorescent imaging in cells and in vivo was further used for the validation of its ability to sensing and blocking thiol,providing evidence of downregulated protein thiols in Parkinson's disease.The enhanced electronwithdrawing inductive effect strategy in this work may provide a general guideline for designing protein thiol agent.

Reconfiguration Cost Analysis Based on PetriNet for Manufacturing System

Nowadays, manufacturers are faced with severe challenges to response rapidly to changing demands and meet various customers’ needs with respect to production volume and product profile. Reconfigurable manufacturing paradigm was proposed as an advanced manufacturing philosophy to enhance the adaptability and flexibility of manufacturing sys-tems. By physical and logical reconfiguration, Reconfigurable Manufacturing System (RMS) is able to fulfil customers’ needs in a cost-effective way by making full use of the resources currently available. This paper focuses on studying of reconfiguration cost of such systems. In this paper, DEDS modelling method Petri Net is used to construct the model for reconfiguration process of RMS which includes physical reconfiguration cost factors and conjunction matrix is used to describe the production processes. By highlighting the differences in the process set before and after reconfiguration, the reconfiguration principles have been proposed to describe and guide the process of the manufacturing system re-configuration. The simulation example is given to prove the validation of the proposed model.

苏云金芽胞杆菌rocE基因的转录调控

【目的】rocE基因编码精氨酸降解途径中的精氨酸通透酶,通过分析苏云金芽胞杆菌(Bacillus thuringiensis,Bt)rocE基因的转录活性,明确rocE基因的转录调控机制。【方法】通过RT-PCR确定rocE基因所在基因簇的转录单元;β-半乳糖苷酶活性测定分析rocE基因启动子(ProcE)的转录活性;采用同源重组技术敲除Bt HD73菌株的rocE基因;通过融合His标签的方法在大肠杆菌中表达纯化RocR蛋白的HTH结构域;通过凝胶阻滞实验明确RocR与rocE基因启动子的结合作用。【结果】在M9培养基中,精氨酸可诱导ProcE的转录活性;在SSM培养基和精氨酸诱导培养基中,与出发菌株HD73相比,ProcE在sigL(编码Sigma54因子)突变体和rocR突变体中的转录活性显著下降。RocR-HTH蛋白与ProcE有结合作用。rocE基因的缺失对菌体生长和Cry1Ac蛋白产量无显著影响。rocE缺失突变体的芽胞形成率为65.5%,HD73出发菌株为85.7%,显著性分析结果表明差异显著(P<0.05)。【结论】rocE基因的转录活性受Sigma54的控制,并受RocR正调控。rocE基因的缺失影响菌株的芽胞形成率。