环己酮直接合成环己酮肟——Ⅰ.钛层柱粘土催化环己酮氨肟化反应特征

钛层柱粘土(Ti-PILC)首次用于液相催化环己酮经氨肟化直接合成环己酮肟,氨肟化反应性能取决于制备Ti-PILC时钛源的选择和催化剂的孔结构。选择合适的反应条件,如反应介质、反应物投料比和催化剂量可进一步提高肟的选择性。     

Analysis of the human factor VIII A2 inhibitor epitope by alanine scanning mutagenesis

Antibodies directed to the A2 domain of factor VIII (fVIII) are usually an important component of the polyclonal response in patients who have clinically significant inhibitory antibodies to fVIII. A major determinant of the A2 epitope has been located by homolog scanning mutagenesis using recombinant hybrid human/porcine fVIII molecules to a sequence bounded by Arg484-Ile508 (Healey, J. F. , Lubin, I. M., Nakai, H., Saenko, E. L., Hoyer, L. W., Scandella, D. , and Lollar, P. (1995) J. Biol. Chem. 270, 14505-14509). Within this region, human residues Arg484, Pro485, Tyr487, Ser488, Arg489, Pro492, Val495, Phe501, and Ile508 differ from porcine fVIII. We stably expressed in mammalian cells nine active B-domainless human fVIII molecules containing single alanine substitutions at these sites. Their inhibition by a murine anti-A2 monoclonal antibody, monoclonal antibody (mAb) 413, and by three A2-specific alloimmune and two A2-specific autoimmune human inhibitor plasmas was measured by the Bethesda assay. The inhibition of Arg484 --> Ala, Tyr487 --> Ala, Arg489 --> Ala, and Arg492 --> Ala by mAb413 was reduced by greater than 90% compared with wild-type, B-domainless human fVIII. mAb413 inhibited the most severely affected mutant, Arg489 --> Ala, 0.01% as well as wild-type fVIII. For all five patient plasmas, the Tyr487 --> Ala mutant displayed the greatest reduction in inhibition. The inhibition of the Tyr487 --> Ala mutant by these antibodies ranged from 10% to 20% that of wild-type fVIII. The inhibition of the Ser488 --> Ala, Arg489 --> Ala, Pro492 --> Ala, Val495 --> Ala, Phe501 --> Ala, and Ile508 --> Ala mutants by most of the plasmas also was significantly reduced. In contrast, the Arg484 --> Ala and Pro485 --> Ala mutants were relatively unaffected. Thus, although mAb413 binds to the same region as human A2 inhibitors, it recognizes a different set of amino acid side chains. The side chains recognized by human A2 inhibitors appear to be similar, despite the differing immune settings that give rise to fVIII alloantibodies and autoantibodies.     

Si-Mn-Mo系低碳贝氏体钢焊接热影响区的脆化机理

用焊接热模拟,普通光学金相,透射、扫描电镜及电子探针,X射线和常规拉伸、冲出等手段研究了一种新型Si-Mn-Mo系低碳贝氏体钢焊接热影响区过热区的组织和性能的关系,重点探讨了过热区的脆化机理.结果表明,在焊接热模拟条件下,原始奥氏体晶粒尺寸是影响机械性能的主要因素.少量准下贝氏体与低碳马氏体的混合组织具有最佳的强韧性配合.随线能量增加,影响韧性的主要因素是奥氏体晶粒粗化以及高温时碳原子在奥氏体晶界及其附近的偏聚;而且碳原子的这种偏聚是经过较高线能量热循环后出现沿晶脆性断口的主要原因.粒状贝氏体及粒状组织中的M-A岛不是该钢焊接热影响区过热区脆化的原因.     

粒状贝氏体组织的疲劳性能

本文研究了粒状贝氏体组织的低周疲劳性能、冲击疲劳性能及旋转弯曲疲劳性能.结果表明:在等抗拉强度下,粒状贝氏体的低周疲劳性能与冲击疲劳性能均优于回火马氏体组织.且随粒状贝氏体含量增加,冲击疲劳寿命相应提高.粒状贝氏体中的(M-A)岛对疲劳裂纹扩展有阻碍作用,对提高疲劳寿命有利.在等强度下,粒状贝氏体的旋转弯曲疲劳性能和回火马氏体组织相当,疲劳极限(Sf)与屈服强度(σy)和断裂强度(S_K)的关系为: S_f=4.651+0.1411(σ_y+S_K)     

EFFECT OF MICROSTRUCTURE ON CORROSION FATIGUE BEHAVIOUR OF A LOW CARBON BAINITE STEEL

The behaviour towards corrosion fatigue of low carbon bainite steel with variousmicrostructures after tempered at different temperatures has been examined. The susceptibilityof the steel to corrosion fatigue may be improved by tempering at 300℃.     

Core–Shell Structure and Interaction Mechanism of γ‐MnO2 Coated Sulfur for Improved Lithium‐Sulfur Batteries

Lithium‐sulfur batteries have attracted worldwide interest due to their high theoretical capacity of 1672 mAh g^?1 and low cost. However, the practical applications are hampered by capacity decay, mainly attributed to the polysulfide shuttle. Here, the authors have fabricated a solid core–shell γ‐MnO₂‐coated sulfur nanocomposite through the redox reaction between KMnO₄ and MnSO₄. The multifunctional MnO₂ shell facilitates electron and Li⁺ transport as well as efficiently prevents polysulfide dissolution via physical confinement and chemical interaction. Moreover, the γ‐MnO₂ crystallographic form also provides one‐dimensional (1D) tunnels for the Li⁺ incorporation to alleviate insoluble Li₂S₂/Li₂S deposition at high discharge rate. More importantly, the MnO₂ phase transformation to Mn₃O₄ occurs during the redox reaction between polysulfides and γ‐MnO₂ is first thoroughly investigated. The S@γ‐MnO₂ composite exhibits a good capacity retention of 82% after 300 cycles (0.5 C) and a fade rate of 0.07% per cycle over 600 cycles (1 C). The degradation mechanism can probably be elucidated that the decomposition of the surface Mn₃O₄ phase is the cause of polysulfide dissolution. The recent work thus sheds new light on the hitherto unknown surface interaction mechanism and the degradation mechanism of Li‐S cells.     

混凝土分层缺陷的超声检测方法研究

为解决混凝土结构中分层缺陷的在线非接触检测难题,论文提出了利用空气耦合(简称:空耦)超声导波定量检测混凝土结构中分层缺陷的新方法。首先研究了空耦超声导波在混凝土结构中的传播特性,理论分析和实验表明,利用空耦超声波以入射角8.7°入射厚度为50 mm的混凝土板时,可以激发以A0模态为主的导波。然后构建了空耦超声导波扫查实验系统,在混凝土结构单侧利用一对倾斜8.7°的空耦探头激励和接收导波信号,通过分析发现A0模态对分层缺陷敏感,且其幅度与扫查路径中的分层缺陷尺寸存在单调变化关系;在此基础上,对检测区域进行扫查,利用不同位置处的导波信号幅度实现分层缺陷的二维成像。实验结果表明,该方法不仅可以避免耦合剂对检测结果的影响,同时可实现对服役状态下混凝土结构中分层位置及尺寸的定量检测。     

A comparative evaluation of foreground/background sketch-based mesh segmentation algorithms

This paper presents an extensive comparative evaluation of five popular foreground/background sketch-based interactive mesh segmentation algorithms, addressing the quantitative assessment of the accuracy, efficiency, and stability of each algorithm. To facilitate the comparison, we have developed a complete framework with an intuitive and simple sketch-based interface to enable interactive mesh segmentation by marking strokes to specify the foreground and background with the mouse buttons, allowing us to quantify the algorithms in a unified manner. The evaluation has been performed via extensive user experiments in which each participant was assigned to segment models with the evaluated algorithms and the corresponding update of each segmentation was recorded as a new refinement when additional interactions were added. We then collected the segmentations from participants and evaluated them against the ground-truth corpus constructed from the Princeton segmentation database. To investigate how well the interactive segmentations match the ground-truth, five metrics were used to measure the boundary and region accuracy of segmentations. By studying the experimental results, we have analyzed the performance of the evaluated algorithms and provided valuable insights into their characteristics.