隧道–土体–地表结构相互作用体系地震响应影响因素分析

为探讨地下结构近距离穿越地表结构时二者之间地震响应的相互影响规律,建立隧道–土体–地表框架结构相互作用体系计算模型,系统研究对该体系地震响应影响显著的参数,具体包括:隧道的直径和埋深、土体的分层特性、框架结构的高宽比及其与隧道圆心的间距、输入地震波特性等。计算分析表明:(1)隧道对体系自振特性影响并不显著,但地表框架结构则显著改变了体系的频率特征;(2)隧道对地表框架结构地震响应的影响主要与隧道的半径相关,较大的隧道半径可阻隔地震波的传播,从而起到一定的减震功能;(3)由于考虑的框架结构质量相对较轻,地表框架结构对隧道地震响应的影响不显著;(4)由于地震波频谱成分及结构自身频率的影响,不同地震波对体系地震响应的影响十分显著;(5)土的分层特性改变了土体的刚度,因而也影响了体系的地震响应。研究成果可为初步定性确定地下结构与临近地表结构地震响应的相互影响提供参考。     

WiMAX标准跟踪研究

本文主要介绍了WiMAX的物理层、MAC层以及网络层标准发展历史和目前最新的进展情况。     

甜菜氮代谢的研究进展

在甜菜生长所必须的营养元素中,氮素对甜菜的生长、含糖率以及产糖量影响最大.文章总结了甜菜与氮素的关系,综述了甜菜对氮素的吸收、运转及其积累和分配的研究和发展.     

An Efficient Marker Gene Excision Strategy Based on CRISPR/Cas9-Mediated Homology-Directed Repair in Rice

In order to separate transformed cells from non-transformed cells, antibiotic selectable marker genes are usually utilized in genetic transformation. After obtaining transgenic plants, it is often necessary to remove the marker gene from the plant genome in order to avoid regulatory issues. However, many marker-free systems are time-consuming and labor-intensive. Homology-directed repair (HDR) is a process of homologous recombination using homologous arms for efficient and precise repair of DNA double-strand breaks (DSBs). The clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein-9 (Cas9) system is a powerful genome editing tool that can efficiently cause DSBs. Here, we isolated a rice promoter (Pssi) of a gene that highly expressed in stem, shoot tip and inflorescence, and established a high-efficiency sequence-excision strategy by using this Pssi to drive CRISPR/Cas9-mediated HDR for marker free (PssiCHMF). In our study, PssiCHMF-induced marker gene deletion was detected in 73.3% of T₀ plants and 83.2% of T₁ plants. A high proportion (55.6%) of homozygous marker-excised plants were obtained in T₁ progeny. The recombinant GUS reporter-aided analysis and its sequencing of the recombinant products showed precise deletion and repair mediated by the PssiCHMF method. In conclusion, our CRISPR/Cas9-mediated HDR auto-excision method provides a time-saving and efficient strategy for removing the marker genes from transgenic plants.     

丁腈橡胶非均相催化加氢研究进展

丁腈橡胶（NBR）选择性催化加氢是制备高附加值、高性能氢化丁腈橡胶（HNBR）的一个重要过程。将链段中C==C双键加氢饱和而保留氰基基团,不仅可保持其原有的耐油性和耐磨性,而且可极大地改善其耐侯性、耐臭氧性等。本文介绍了NBR加氢的几种工艺,着重综述了NBR非均相催化加氢的研究进展及发展方向,探讨了负载型催化剂的载体孔道结构和表面性质及活性组分组成对NBR加氢性能的影响。本文还对非均相催化加氢过程中的溶剂效应、催化剂的回收和循环再生进行了阐述,提出溶剂对催化加氢速率和加氢度都有重要影响,溶剂的受氢能力（β值）是影响加氢过程的关键参数。催化剂失活的主要原因是表面活性位点被聚合物覆盖,而利用有效的溶剂洗涤或者采用催化剂表面功能化的方式,可促使活性位再次暴露,恢复其加氢活性。最后,对非均相加氢制备高附加值HNBR体系中的催化剂设计、溶剂效应和催化剂再生等发展方向进行了展望。     

甘薯活性多糖抗突变作用的体外实验研究

为了探讨甘薯的保健作用,本文利用鼠伤寒沙门氏菌营养缺陷型回复突变试验（Ames试验）对甘薯活性多糖进行了体外抗突变作用的研究。结果表明：甘薯活性多糖具有显著的抗突变作用,当其剂量为20mg/平皿时对2－AF、B[a]p和AFB1的致突变性抑制率均达到70％以上,并且呈明显的剂量－效应关系;甘薯活性多糖的抗突变作用主要是通过阻断致突变物使正常细胞变为突变细胞而实现的,也包括部分去突变作用,但促进突变细胞修复的作用不明显;随着121℃高温处理时间和紫外光（30W,25cm)照射时间的增加,甘薯活性多糖的抗突变作用有所减小,而在pH3．5－pH7．5下处理30min后对其抗突变作用影响不大,超过这个pH范围,抗突变作用都有所减小。     

Rhodium‐Catalyzed Oxidative ortho‐Acylation of Aryl Ketone O‐Methyl Oximes with Aryl and Alkyl Aldehydes

The rhodium‐catalyzed oxidative ortho‐acylation of aryl ketone O‐methyl oximes with aryl and alkyl aldehydes via C H bond activation is described. The cross‐coupling reaction exhibits high functional group tolerance and regioselectivity under relatively mild conditions and constitutes a versatile route to a diverse library of diaryl ketones, which are difficult to obtain by the classical Friedel–Crafts acylation. Moreover, this reaction proceeds via an unprecedented Rh‐catalyzed oxidative ortho‐acylation of aryl ketone O‐methyl oximes with highly electron‐deficient aryl aldehydes followed by a direct addition of the second ortho C H bond to aldehydes in a one‐pot reaction, to generate two C C bonds simultaneously.     

用于CBM-TOF超级模块探测器质量控制的分布式数据读出方法

高压缩重子物质(Compressed Baryonic Matter,CBM)实验装置飞行时间谱仪利用由多气隙电阻板室(Multi-gap Resistive Plate Chamber,MRPC)探测器构建的超级模块实现高密度、高精度的粒子飞行时间测量,该超级模块可支持高达320通道的高精度时间测量能力,数据率高达6 Gbit·s~(-1)。为实现超级模块探测器的性能评估,提出一种基于千兆以太网的分布式数据读出方法,利用片上系统技术实现读出节点的千兆网络传输能力。测试结果表明,针对单条数据传输路径,原型读出模块在全链路情况下,能实现约467 Mbit·s-1的综合数据传输速率。读出方案中事例组装、命令发送、状态显示等功能均运行正常。     

Experimental Study on Inactivation of Bacterial Endotoxin by Using Dielectric Barrier Discharge

The low-temperature plasma （LTP） generated by dielectric barrier discharge （DBD） was used to sterilize the E.coli endotoxin, which is usually difficult to kill ...     

煤矿硫化氢的危害与防治

为了精确预报煤矿井下硫化氢含量,防止硫化氢含量超标带来的危害,基于可调谐半导体激光吸收光谱技术,设计研制了一种便携式硫化氢检测仪。该仪器采用中心波长为1 590 nm的分布式反馈激光器,结合多次反射的郝里奥特长光程气体吸收池,可以满足煤矿井下0~200 mg/L硫化氢的实时检测。离线标定和实验室测试得到检测仪测量的相对误差为±2%,最快响应时间为0.5 s;通过实验室测量六盘水大湾煤矿120205采煤工作面上隅角和采空区的气体成分,结果表明,便携式硫化氢检测仪稳定可靠, 能够满足煤矿井下硫化氢预警的要求。