The composition and distribution of metal clusters in the MoFe protein from a nifZ deletion strain （DJ 194） of Azotobacter vinelandii

Through the anaerobic chromatography on the columns of DEAE 52, Q-Sepharose and Sephacryl S-200, a nitrogenase MoFe protein (△nifZ Av1) was obtained from a nifZ deleted mutant of Azotobacter vinelandii (stain DJ194).The results of Western blotting after anoxic native electrophoresis and SDS-PAGE showed that △nifZ Av1 was similar to wild type MoFe protein (OP Av1) at the electrophoretic mobility, molecular weight and subunit composition. Furthermore, △nifZ Avl was also similar to OP Av1 at the molybdenum content, EPR signal (g≈4.3, 3.65 and 2.01), and the molar extinction coefficient (△ε) of circular dichroism (CD)at 660 nm region. All of these indicated that, besides having the same α2β2 composition as OP Av1, the △nifZ Av1 also contained equal amount of reductive FeMoco in the spin state of S=3/2 to OP Av1. However, the iron content and substrate (C2H2, H^ and N2)-reduction activity of △nifZ Av1 were 74% and 46%-50% of those of OP Av1, respectively. Furthermore, the △ε at around 450 nm, which reflects P-cluster in Av1, was obviously lower than that of OP Av1. It suggested that the difference between △nifZ Avl and OP Av1 resulted from P-cluster rather than FeMoco, and from the half number of P-cluster in △nifZ Av1, but the composition or redoxstate of P-cluster in △nifZ Av1 were not changed. Thus it could propose that △nifZ Av1 is composed of two different αβsubunit pairs. One is a FeMoco-and P-cluster-containing pair, and the other is a P-cluster-deficient but FeMoco-containing pair. Since the deletion of nifZ gene leads to the deficiency of only one of two P-clusters in a α2β2 tetramer, the assembly of P-cluster may not simply depend on one gene product, and so a possible mechanism of NifZ is supposed here.     

用低温等离子体技术降解三氟溴甲烷（哈隆1301）

利用低温等离子体技术对三氟溴甲烷ＣＦ３Ｂｒ进行了降解。在放电３ｍｉｎ后，ＣＦ３Ｂｒ的降解率可达５５％，而在ＣＦ３Ｂｒ－Ｏ２体系中，ＣＦ３Ｂｒ的降解率可达６８％。研究了低压ＣＦ３Ｂｒ的气相反应机理，以及ＣＦ３Ｂｒ初妈压力，外加气体对降解ＣＦ３Ｂｒ的影响。     

酵母/硅复合材料对铈(Ⅲ)的吸附性能及机理

利用溶胶-凝胶法制备酵母/硅复合材料,研究了其对水溶液中铈离子的吸附行为.通过静态吸附试验,考察了初始pH值、吸附时间、初始质量浓度、温度和共存离子等因素对吸附性能的影响.从动力学、等温吸附方面对吸附过程进行了分析,并通过傅里叶变换红外光谱和透射电镜探讨了吸附机理.研究结果表明:pH =5.5时,吸附效果最佳;吸附量随初始质量浓度的增加而增加,随着温度的升高而增大;120 min后吸附过程趋于平衡;共存离子对铈的吸附影响不大.准二级动力学方程较好地描述了酵母/硅复合材料对铈的吸附动力学行为.Langmuir吸附等温模型能更好地描述吸附材料的吸附平衡性能,表明该吸附属于单分子层吸附,298 K时,最大吸附量为36.1 mg·g-1.     

太阳能晶硅片废砂浆回收中固液分离工艺参数研究

固液分离作为废砂浆回收的第一道工序,对整个晶硅片废砂浆回收有极大影响。本文从固液分离工艺中各个步骤出发,根据废砂浆中碳化硅型号的不同,分别优化造浆浓度、卧螺离心机操作参数及刮刀滤布型号参数;同时将卧螺排水进行二次分离,使得废砂浆综合回收率提高到90%以上。     

基于残差网络的高温合金微观组织图像分割方法

材料微观组织图像分析是材料研究的重要环节,其分析方法的精准性和快速性对新材料的设计、研制和现有材料的优化、寿命评价都非常重要。因此,如何建立更快速更精准的微观组织分割方法成为微观组织图像分析和性能评价的关键。针对传统的微观组织图像分割技术对于高温合金材料分析精度不高等问题,通过对卷积神经网络结构进行优化,提出了一种基于Res_Unet网络的微观组织图像分割方法。实验验证结果表明,本文的方法不仅解决了深度学习在材料组织图像小样本数据上的实现问题,还显著提高了材料微观组织图像的分割精度。     

基于强化学习的视频车辆跟踪

基于视频的车辆跟踪在交通监控领域有着重要的实用价值,强化学习是一种无监督的学习方法,具有搜索效率高的特性,将强化学习理论应用于视频车辆的跟踪,充分发挥了其搜索效率高的特性,实验结果表明基于强化学习的视频车辆跟踪,其跟踪情况稳定,跟踪准确率比较高,可以获得很好的跟踪效果。     

Evaluation of Multi-Scale Full Waveform Inversion with Marine Vertical Cable Data

Seismic illumination plays an important role in subsurface imaging. A better image can be expected either through optimizing acquisition geometry or introducing more advanced seismic mi-gration and/or ...     

An Evaluation of Reverse-Time Imaging of Clustering Earthquakes

Clustering earthquakes refer to the seismic events that occur closely with each other in time and space. Because their overlapping waveform records make it difficult to pick the first arrivals, the hyp...     

略谈英语同义词在用法上的区别

英语同义词的教学应该从两个方面进行。一是区别其在词义上的差异,二是区别其在用法上的差异。教师在同义词讲解中往往重视前者而忽略后者。本文就英语同义词在用法上的差异作粗浅探讨。     

SXSES─DSS模型库和方法库管理系统的设计与实现

模型库具有３级视图，实现了模型的３级独立，允许多种模型表示方法，为动态构模提供了连接机构和交互构模界面。方法库采用统一方法首部，实现方法封装。它们为人机结合的复杂的智能化巨决策支持系统提供了模型和方法的管理支持。