DNA体外缩合的研究进展

DNA缩合不仅是自然界常见的生理现象,也是非病毒载体介导基因转染的关键步骤。了解DNA体外缩合的性质与特征,将有助于设计出高效的非病毒转基因载体。本文综述了近十几年来以多价阳离子为缩合剂诱发的DNA体外缩合的研究进展,着重介绍了缩合的机理、过程、影响缩合的因素以及应用于转基因的最新成果。     

Algorithms of target detection on hyperspectral imagery

With the development of airborne and spaceborne remote sensing from the 1980s, as a new and growing technology, hyperspectral imaging is widely used in different fields, such as military investigation, battlefield information acquisition, environmental monitoring, mineral exploration and public security. Because of the unique characteristic of acquiring spectral and spatial information simultaneously, it brings the hyperspectral detection advantages when dealing with target detection problem under complex conditions. Target detecting models of hyperspectral image are established, including the target subspace model and the probability statistical model. And several algorithms are introduced, which are based on original spectral features, sub-space projection and probability statistical model separately. Comparison shows that if the background includes fault objectives, GLRT is the best algorithm, and its SINR is the largest; on condition of anomaly target detection, LPTD is the best, and have a quite high SINR.     

An angle-resolved laser incident beam detector based on a pair ofFabry-Perot etalons

An angle-resolved laser detector based on a pair of a non-mechanical scanning Fabry-Perot cavities is described. The differential signal from the two cavities is approximately independent from the polarization of the incident laser beam and it is used to determine the angle of incidence of the beam on the Fabry-Perot cavities. The F-P etalon is made of interferometric filter combination. A laser incident angle sensor experimental platform is built up, and the experiment is carried out with a given laser range finder. When the incident angle is less than 5°, the transmission difference measured by the laser angle sensor is significantly lower than theoretical value, and deviation is more than 10%. When the incident angle is greater than 10°, the deviation is much lower than that of the situation of the incident angle is lower than 10°.     

Plastically deformable polyethylene with excellent transparency and stress whitening resistance properties fabricated by constructing massive chain entanglement

Stress whitening is one of the most prominent macroscopic defects for polyethylene (PE), which greatly affects the appearance and quality of its commodity. In order to eliminate the stress whitening defects of PE, ultrahigh molecular weight polyethylene (UHMWPE) was blended with PE to fabricated PE/UHMWPE, and the enhanced intermolecular entanglement and stretchability was achieved, which greatly suppressed and impeded the occurrence of heterogeneous plastic deformation and fibrillar bundle structure during applying tensile stress, resulting in the sharply deceased of the nanoscale cavities defects for the sample. And thus, the elimination of stress whitening defects and high-light transmittance in the visible region with excellent optical transparency performance were successfully achieved for PE/UHMWPE. Moreover, introduction of UHMWPE chains significantly improved the orientation degree and formed a dense oriented crystalline network with fine lamellae for the sample, which highly enhanced the mechanical strength of PE/UHMWPE after applying stress. This work provided a new strategy for developing stress whitening eliminating polyolefin materials with high performance, which was of great significance for sustainable development and environmental friendliness.     

硅酸镁锂的有机改性及对Cr(Ⅵ)的吸附特性

采用水热法合成了硅酸镁锂(Laponite), 然后利用十六烷基三甲基溴化铵(CTMAB)对其进行有机改性, 研究了改性后的有机硅酸镁锂(CTMABL)对Cr(Ⅵ)的吸附特性. 结果表明, 改性后样品的比表面积和孔容积变小而平均孔径增大. CTMABL样品的d₍₀₀₁₎值从改性前的1.23 nm增加到1.79 nm, 表明CTMAB进入Laponite层间. 随着溶液pH值的提高, CTMABL对Cr(Ⅵ)的吸附效率明显下降; pH<8.5时, CTMABL颗粒表面电势为正, 能够与Cr(Ⅵ)阴离子发生静电吸引从而提高吸附效率. 随着固液比增加, 对Cr(Ⅵ)的去除效率迅速上升, 当固液比达到4 g/L后去除效率趋于稳定. 离子强度对Cr(Ⅵ)吸附过程的影响不明显. CTMABL对Cr(Ⅵ)的吸附符合准二级动力学模型, 吸附传质速率受膜扩散和颗粒内扩散过程共同影响. 等温吸附过程符合Langmuir模型, 热力学分析结果表明吸附过程是一个自发的吸热反应. 综合分析认为表面配合作用是主要的吸附机制, 同时静电引力在吸附过程中起到了促进作用.     

层合板问题几种求解方法的比较

为比较Lagrange 体系和Hamilton 体系的有限元法在求解层合板问题时的优劣,以寻求此类问题较合适的数值方法,本文在已有研究的基础上,将几种有限元法应用到层合板问题的计算中,编程并对相关算例进行计算和分析. 数值结果表明：Hamilton 体系常规有限元和改进有限元,Lagrange 体系理性有限元在计算此类问题时各有其优势,而Lagrange 体系常规有限元在求解此类问题时的精度较差.     

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将理性有限元法引入到Timoshenko梁问题中,提出了一种理性Timoshenko梁单元,克服了 剪切锁死现象. 在推导控制方程时,与传统有限元方法采用Lagrange插值不同, 理性有限元法用Timoshenko梁弯曲问题的基本解逼近单元内部场. 运用该梁单元分析 Timoshenko梁时,无需缩减积分,就能避免剪切锁死,并且极大地提高了计算精度,说明 理性有限元法具有广泛的应用前景.     

径向辛体系一种新的差分格式

通过对Hellinger-Reissner变分原理进行坐标变换,将径向模拟为时间,导向辛体系,得到Hamilton对偶方程组.将微分形式的有限差分法引入弹性力学极坐标系下径向辛体系,把对偶方程组中的微分方程直接改用差分方程代替,推导出极坐标系下问题的辛差分方程,从而得到一种全新的径向辛体系差分格式.求解方程组,可直接得到位移和应力.编程计算曲梁等算例,结果表明该辛差分格式是有效的,丰富了弹性力学辛体系差分法的内容.