Induction of DNA-double-strand breaks by auger electrons from 99mTc complexes with DNA-binding ligands

The potential of certain Auger electron emitting nuclides for systemic radiotherapeutic applications has recently gained much attention. In particular, the ability of several nuclides, including 111In, 125I, and 123I, to induce DNA double-strand breaks (dsb), a good indicator of cytotoxicity, has been extensively studied. However, this ability has never previously been shown experimentally for 99mTc, which, besides the well-known gamma radiation that is used for diagnostic applications, also emits an average of 1.1 conversion electrons and 4 Auger or Coster-Kronig electrons per decay. Owing to the short range of Auger electrons, the radionuclide needs to be located very close to the DNA for dsb to occur. We synthesized two cationic 99mTcI-tricarbonyl complexes with pendant DNA binders, pyrene and anthraquinone. The X-ray crystal structures of the two complexes could be elucidated. Linear dichroism and UV/Vis spectroscopy revealed that the complex with pyrene intercalates DNA with a stability constant, K, of 1.1 x 10(6) M(-1), while the analogous complex with anthraquinone interacts with DNA in a groove-binding mode and has an affinity value of K=8.9 x 10(4) M(-1). We showed with phiX174 double-stranded DNA that the corresponding 99mTc complexes induce a significant amount of dsb, whereas non-DNA-binding [TcO4]- and nonradioactive Re compounds did not. These results indicate that the Auger electron emitter 99mTc can induce dsb in DNA when decaying in its direct vicinity and this implies potential for systemic radiotherapy with 99mTc complexes.     

基于应变传递率的管道结构损伤识别研究

为了研究海底管道损伤识别的分布式监测方法,在标量传递率概念的基础上提出了应变传递率概念和相应的损伤识别方法来对海底管道进行损伤识别,并通过有限元模型模拟对该方法进行了验证。对管道模型的不同损伤程度进行了分析,对比发现该方法相比加速度传递率和理论传递率对损伤程度更加灵敏。对不同边界条件进行分析,发现该方法对损伤位置的识别不受边界条件的影响。对参考单元的选取进行了验证分析,验证了参考单元应选择远离反弯点的非损伤位置。     

在役加氢反应器材料损伤分析

基于随加氢反应器运行 5a的试验试块 ,研究了加氢反应器运行 5a后筒体材料 2 .2 5Cr 1Mo钢的损伤。进行了化学成分分析、拉伸和冲击试验、脱氢和脱脆试验以及断口形貌分析。结果表明 :反应器运行 5a后筒体母材及其焊缝金属的拉伸性能未发生明显变化 ,而冲击韧性明显降低 ,且焊缝金属损伤程度较母材严重。经分析 ,材料的损伤主要是加氢反应器长期使用过程中高温回火所致     

基于MSA法的高心墙堆石坝地震沉降易损性分析

多条带分析法(MSA)是新近提出的一种针对离散强度因子的易损性分析方法,为结构安全评估提供了有效路径,但目前在土石坝工程领域应用较少。本文针对高心墙堆石坝,选取坝顶震陷率为性能指标,建议了轻度、中度和重度破坏三个等级;考虑地震动的随机性,采用MSA法开展了易损性研究,得到了不同破坏等级的易损性曲线和概率,为大坝的强震性能评价提供准则和参考;不同条带数量下地震易损性分析结果表明,适当减少水平条带数量,对易损性结果影响不大,这有利于计算工况的减少。     

考虑卸荷损伤的柱状节理岩体开挖特性研究

通过建立柱状节理岩体径向应力比与力学劣化系数的数学关系,获取柱状节理岩体卸荷损伤效应的定量表达式。结合FLAC~(3D)提出一种考虑卸荷损伤的柱状节理岩体开挖分析方法,实现岩体单元的力学参数在开挖过程中随实际应力状态得到动态调整。在此基础上开展柱状节理岩体试验洞的开挖特性分析。结果表明,考虑卸荷损伤的计算数据与实测数据基本吻合,试验洞围岩的位移、体积应变增量和塑性区均随开挖断面的逐步增加而增大,且呈边墙最大,底板次之,拱顶最小的分布规律。最后采用体积应变增量大于0.10%和塑性区作为岩体松弛的综合判别指标,其分析结果与钻孔声波测试数据相一致。     

抗地震结构的服役费用函数及其建立方法

讨论了服役工程结构的经济性问题 ,包括 :抗地震结构在服役过程中为完成预定功能所需要的经济花费、这些花费同结构抗震可靠度的函数关系以及它们的建立方法。形成的服役费用函数可以作为决策结构最佳抗震设防标准的依据。     

基于超声成像技术的套管损伤检测系统设计

工业的发展越来越依赖石油和天然气,合理高效的开采、及时对油气井生产的套管损伤状况检测至关重要.为了解决这个间题,本文提出基于超声成像技术实现套管损伤程度的检测.首先,阐述超声波成像技术基本原理,再对成像检测系统进行总体设计,包括硬件电路设计和软件系统设计.其中,系统软件设计中,利用MATLAB软件仿真实现对被检测超声波回波信号的模拟呈现,能从成像图上观测到套管的各个损伤部位坐标和损伤程度,这样有利于更加直观、清晰分析套管损伤性质,有效地缩短了设计周期,使检测系统结构趋于合理,符合工程实用.     

Experimental habitat scenting inhibits colonization by beaver,Castor canadensis

Unoccupied beaver (Castor canadensis) sites in New York State were for two years experimentally scented with a mixture of beaver castoreum and anal gland secretion. These sites were colonized less often than unscented control sites. The beaver is the first mammal to have been shown experimentally to use intraspecific odor cues when settling in vacant habitat. Territorial pheromones may be useful as repellents for beaver or other rodents.     

有机固相沉积对储层的损害

定性分析有机同相沉积对储层的影响,定量研究有机固相沉积后储层的损伤情况.利用岩石-毛细管模型描述地层孔隙空间,并用孔隙度、渗透率与比面等的相互关系推导出有机同相沉积量与储地层参数的变化关系式.     

Static solution on four-region spherial cavity expansion model in a pressure sensitive medium

Spherical cavity expansion model is often used to study the mechanic characteristics of pressure sensitive mediums. The most important one we do in the paper is that we construct a four-region model with σθ≠0 in damage region,which is different from what Satapathy did before and is more reasonable. By adopting this model,different constitutive equations were constructed by different method-elastic mechanics in elastic region,damage mechanics and fracture mechanics in damage region,and macro-micro mechanics theory in plastic region. Then using Durban's self-similarity assumption,the control differential equations with boundary conditions were established,and the static numerical solution of stress field and displacement field in the three different regions of elastic,damage and plastic area were discussed respectively. Results showed that this four-region model can describe precisely the mechanic characteristics of pressure sensitive mediums under initial pressure.