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991.
迭层空腹桁架转换层结构的静力性能分析 总被引:7,自引:0,他引:7
迭层空腹桁架是一种新型的转换层结构型式。,本文分析了弦杆截面尺寸、腹杆布置对结构受力性能的影响,从而给出了其设计建议。 相似文献
992.
Baisong Lu Fang Yu Jianhua Wang Siqing Zhao Dong Zhao Qiuyun Dai Peitang Huang Cuifen Huang 《科学通报(英文版)》2000,45(5):432-435
Conotoxins are short peptide-toxins with specific targets and large diversity. They are useful in analgesia, neuroprotection,
detection of some kinds of deseases, and receptor and ion channel study. In order to explore the conotoxin resourses of Chinese
oceans, rapid amplification of 3′ cDNA ends (RACE) method was utilized to systemically analyze the O-superfamily conotoxin
content ofConus striatus inhabited near Chinese Hainan Island. Six new O-superfamily conopeptides were identified, one of which is highly homologous
to MVIIA, an N-type calcium channel antagonist. 相似文献
993.
Regulatory role of the sequences downstream fromnodD3 P1 promoter ofRhizobium meliloti 总被引:1,自引:0,他引:1
The 660 bp region betweennodD3 P1 promoter and the following coding region ofRhizobium meliloti has been studied. This region is designated “downstream sequences”. It consists of two potential open reading frames, ORF1
and ORF2. Studies on the role of the downstream sequences on the activity ofnocD3 P1 with nod D3(P1)-IacZ fusion show that deletion of the sequences containing ORF2 causes the increase of the activity of the fusion; on the contrary,
addition of extra copies of ORF2 markedly decreases the activity of the fusion. These results indicate that the product of
ORF2 plays a negative role in the expression ofnod D3. 相似文献
994.
Menadione can induce apoptosis in tobacco protoplasts. Typical characteristics are detected including the condensation of
chromatin, the formation of apoptotic bodies and the degradation of genomic DNA into “DNA ladder”. Specific DNase is activated
during this process. Ca2+ and Mg2+ are necessary for its activation, while Zn2+ and EDTA (Ethylenediaminetetraacetic acid) can inhibit its activation. The fragmentation of DNA and lamin can be inhibited
by DEVD (Ac-Asp -Glu- Val- Asp-aldehyde). The fragmentation of lamin can also be inhibited by PMSF (Phenylmethylsulfonyl fluoride)
and CH (Cyclohexinide). These results show that activation of specific DNase and proteases is involved in menadion-induced
apoptosis in plants. 相似文献
995.
目的 :X线评价腰部创伤后腰椎稳定性。方法 :对 12 8例腰部创伤患者摄腰椎正侧位片 ,应用Denisi等人创伤生物力学实验研究原理方法进行 X线分析 ,对腰椎稳定性作出评价。结果 :腰部创伤后引起椎体及附件骨折 2 0例 ,其中胸 1 1 2例 ,胸 1 2 4例 ,腰 1 2例 ,腰 2~ 5 8例 ,腰椎横突骨折 2例 ,其他附件骨折 2例。腰椎椎体移位 ,全部发生在腰 3~ 5 。腰椎不稳定 8例均有椎体压缩性骨折改变。结论 :腰部创伤除引起椎体及附件骨折外 ,也可致腰椎不稳定。 相似文献
996.
目的 :探讨血清透明质酸 (HA)、 型胶原 ( - C)联合检测对肝纤维化诊断的准确性。方法 :运用放射免疫法 (RIA)测定 98例慢性肝炎患者血清 HA、 - C水平 ,并与临床 B型超声检查结果进行对比研究。结果 :二项指标升高与肝纤维组织增生程度呈良好的正相关 (P<0 .0 1)。二项指标分别在慢性肝炎中型、慢性肝炎重型以及肝硬化中渐次升高 ,有显著差异 (P<0 .0 1)。同期 B超检查结果准确率不高。结论 :二项指标的联合检测在肝纤维化和早期肝硬化的诊断上较 B超检查准确、可靠。 相似文献
997.
聚变等离子体中存在负磁剪切的情况下,研究发现在α(α=-q2Rdβ/dr,q是安全因子,β是等离子体压力与磁压力之比,R和r分别代表托卡马克的大半径和小半径)引起的第二个势井里面存在αTAEs(α-induced Alfvén eigenmodes)。这些模式是一种很危险的本征模,容易被激发从而破坏聚变等离子体的稳定状态。对该本征模的研究,为该领域的研究提供了一些参考。 相似文献
998.
针对GPS接收机在跟踪过程中由频率误差引起的位同步概率下降问题,提出了一种基于频率补偿的GPS位同步方法.分析了环路中频率误差引起相干积分累加值衰减的机理,利用不同频率的复信号分别对相干积分结果进行补偿,计算出20个候选位置的值,最大值对应的位置即为数据边界位置.该方法有效减少了由频率误差导致的相干累加损耗,提高了位同步的概率.在弱信号情况下,使用非相干积分方法可进一步提高信号增益和位同步概率.与其他位同步方法相比,所提方法可容忍更大的频率误差,即使跟踪环路处于失锁状态也能准确实现位同步,且在频率误差小于25 Hz的情况下表现出更优的位同步性能. 相似文献
999.
1000.
Critical Systems Thinking on the Inefficiency in Post-Earthquake Relief: A Practice in Longmen Shan Fault Area 总被引:1,自引:1,他引:0
Jiuping Xu Jiuzhou Dai Renqiao Rao Huaidong Xie Yi Lu 《Systemic Practice and Action Research》2016,29(5):425-448
The Longmen Shan Fault area is one of the most active seismic zones in the world, has a relatively dense population and a low economic development level. Therefore, the provision of effective post-earthquake relief is very important for saving lives and restricting financial losses. However, providing urgent relief is a complex problem that requires efficient coordination between the organizations, and departments involved, and the specific environments, for the supply of urgent materials, energy and information. In practice, although there are sufficient relief supplies, because of the lack of systemic thinking, relief activities are often chaotic leading to inefficiencies and even increases in the damage and loss of life. In this study, a critical systems thinking approach is used to reflect on the system contexts, boundaries, structures and functions of the emergency relief systems. Using systems modeling we constructed simulations for different relief plans and their consequences, and a work shop of metasynthetic engineering was constructed to integrate the different views, knowledge and contexts. At the practical stage, after the model’s validity was verified from the 2008 Wenchuan earthquake data, based on the 2013 Lushan earthquake simulation results, some recommendations are made to improve future post-disaster relief operations. Finally, the significance of critical systems thinking is demonstrated to ensure effective and efficient of post-earthquake relief. Some limitations and future research also have been presented in conclusion. 相似文献