Insight into Conformational Change for 14-3-3σ Protein by Molecular Dynamics Simulation

14-3-3σ is a member of a highly conserved family of 14-3-3 proteins that has a double-edged sword role in human cancers. Former reports have indicated that the 14-3-3 protein may be in an open or closed state. In this work, we found that the apo-14-3-3σ is in an open state compared with the phosphopeptide bound 14-3-3σ complex which is in a more closed state based on our 80 ns molecular dynamics (MD) simulations. The interaction between the two monomers of 14-3-3σ in the open state is the same as that in the closed state. In both open and closed states, helices A to D, which are involved in dimerization, are stable. However, large differences are found in helices E and F. The hydrophobic contacts and hydrogen bonds between helices E and G in apo-14-3-3σ are different from those in the bound 14-3-3σ complex. The restrained and the mutated (Arg56 or Arg129 to alanine) MD simulations indicate that the conformation of four residues (Lys49, Arg56, Arg129 and Tyr130) may play an important role to keep the 14-3-3σ protein in an open or closed state. These results would be useful to evaluate the 14-3-3σ protein structure-function relationship.     

g-C_3N_4/TiO_2复合光催化剂的制备及其性能研究

以四异丙醇钛和三乙胺为原料,通过水解法合成TiO2。三聚氰胺于580℃煅烧得到g-C3N4,g-C3N4与TiO2按一定比例混合,在超声波条件下加入适量的甲醇得到复合材料g-C3N4/TiO2。以甲基橙为光催化反应模型考察了复合材料的紫外光催化活性。结果表明,g-C3N4/TiO2具有良好的光催化活性,用量3%时,甲基橙脱色率达96.6%。     

H3PWl2O40/Y-β催化苯甲醛1,2-丙二醇缩醛的绿色合成

采用Y-β复合分子筛负载H3PWl2O40为催化剂,对苯甲醛与1,2-丙二醇发生缩合反应合成苯甲醛1,2-丙二醇缩醛进行了研究,考察了催化剂用量、醇醛摩尔比、反应时间、带水剂用量及催化剂重复使用次数等因素对收率的影响。结果表明,该催化剂具有催化性能高,易回收并有较好的重复使用性能等优势。最佳反应条件为：苯甲醛0.1 mol,醇醛摩尔比1.2,催化剂用量0.6 g,带水剂环己烷用量为10 mL,反应40 min后收率为92.3％。     

溶胶-凝胶微波加热合成PbZr_(0.52)Ti_(0.48)O_3前驱体

以硝酸铅、硝酸锆、四氯化钛、柠檬酸为原料,用溶胶-凝胶法制备出凝胶,在100℃下烘干,然后用微波炉加热,合成了PbZr0.52Ti0.48O3前驱体。讨论了微波合成参数对粉体晶相和晶体粒度的影响。用X射线衍射仪(XRD)、扫描电子显微镜(SEM)对制备的粉体进行了表征。结果表明,溶胶-凝胶结合微波加热法可以在较短的时间内制得PbZr0.52Ti0.48O3粉体,且晶形发育比常规加热更完善。微波120℃加热20min,可得到纯相的PbZr0.52-Ti0.48O3前驱粉。     

2,6-二氯-3-氰基-4-甲基吡啶的合成及应用

2,6-二氯-3-氰基-4-甲基吡啶是制备染料的重要中间体,本文对2,6-二氯-3-氰基-4-甲基吡啶合成路线及其优缺点进行评述,并对其应用进行了介绍。     

Microstructure and properties of WC reinforced Ni-based composite coatings with Y2O3 addition on titanium alloy by laser cladding

ABSTRACT

In this study, WC reinforced Ni-based composite coatings with Y₂O₃ addition were deposited on Ti-6Al-4V titanium substrate by laser cladding. The phases, microstructure, microhardness and wear resistance of the composite coatings were studied by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, microhardness tester and wear tester. The results showed that good metallurgical bonding was achieved between the composite coatings and substrate. The phases mainly were γ-Ni, TiC, TiB₂, Ni₃B, M₂₃C₆ and WC. Most of the WC was dissolved in small pieces of WC during the laser cladding process. The microhardness of the composite coatings was about 3 times that of the titanium substrate and the wear resistance of the composite coatings had a significant increase.     

Harnessing the scientific synergy of welding and additive manufacturing

ABSTRACT

Additive manufacturing (AM) of metallic materials and welding share many similarities in their physical processes and the way the microstructure and properties of the products evolve. This synergy can be a powerful driver for the scientific and technological advancements of both these important technologies for the benefit of all people. Science and Technology of Welding and Joining provides a forum for the exchange of emerging scientific and technological advancements in AM. This special issue of the journal highlights the current research in the AM processes, and the microstructure and properties of metallic components. Furthermore, it identifies some of the current challenges and opportunities for the future.     

Friction and wear reductions in fluorinated plain and fully formulated oils through enhanced heating time using moderate loading under boundary lubrication conditions

The use of fluorinated mix catalyst (titanium fluoride: TiF₃ + iron fluoride: FeF₃) with polytetrafluoroethylene: PTFE in engine oil is increasingly a strategy to improve fuel economy and component durability to simultaneously provide low friction and excellent wear protection. The influence of these additives shows promising results during load bearing capacity testing and long‐term durability experiments. This paper addresses the enhancement of friction and wear performances of 0.1% and 0.05% phosphorus plain zinc dialkyl dithiophosphate (ZDDP) oil and fully formulated engine oil when heated to 100°C for specific time under thermal and tribological conditions for moderate pressure loading (1.9 GPa Hertzian pressure or 180 N) which simulate the cold start of a car under 700 rpm rotational speed or the valve trains loading where most of the ZDDP are applied. Tests were performed in a ball on cylinder tribometer under boundary lubrication conditions. Surface analyses were carried out using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results showed that the anti‐wear additives (2 wt. % PTFE + 0.5 wt. % FeF₃ + .5 wt. % TiF₃) provided excellent wear protection to 0.1% phosphorus plain and fully formulated oil when cylinder is immersed in the desired lubricant and heated for a predetermined time but performed poorly in 0.05% phosphorus fully formulated oil under the same conditions. The transform of anti‐wear coated material to the worn surfaces, which was a function of the anti‐wear performance of additives, was shown to have an influence on friction performance. The wear reducing effect, which was observed in fluorinated additives tribological tests, indicated a positive contribution and good tribofilm formations. Copyright © 2016 John Wiley & Sons, Ltd.     

救生机器人推进器的3维反问题设计与性能校验

针对水上救生机器人难以实现快速稳定航行的问题,采用3维反问题设计理论对机器人推进器进行几何设计并对相关参数进行匹配,在合理假设条件下,将喷水推进泵内的有旋流方程进行有效分解获得周向平均流动方程和周期性脉动流动方程。使用速度矩沿流线的分布来控制叶片的载荷,运用计算流体力学对所设计的喷水推进泵进行水力性能校验,结果表明：在毂径比较大等特定条件约束下,喷水推进泵的水力效率达到80.38%,并且在较宽的流量范围内保持高效,叶轮表面压力沿轴向分配合理,没有局部低压区,叶轮推力满足预期性能,验证了设计思路和参数配置的正确性。