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适应性突变的遗传学特征 被引量:2
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作者 张汉波 沙涛 +1 位作者 程立忠 丁骅孙 《遗传》 CAS CSCD 北大核心 2002年第3期395-398,共4页
基于大肠杆菌FC40菌株的研究结果表明 ,适应性突变依赖RecBCD重组途径的酶 ,要求SOS反应的部分基因功能 ,lac+ 回复突变序列都是在单核苷酸短重复序列处的一个碱基缺失。有证据表明有的适应性突变来自一个或多个暂时性的超突变的细胞亚... 基于大肠杆菌FC40菌株的研究结果表明 ,适应性突变依赖RecBCD重组途径的酶 ,要求SOS反应的部分基因功能 ,lac+ 回复突变序列都是在单核苷酸短重复序列处的一个碱基缺失。有证据表明有的适应性突变来自一个或多个暂时性的超突变的细胞亚群 ,它们的基因组发生大量的突变 ,转座子高频丢失。产生这种暂时性的超突变的增变子可能是因为细胞的MMR活性暂时不足 ,或是因错误翻译产生丧失了校读活性的DNA聚合酶III。其他一些研究系统虽然得到了一些同FC40菌株不一致的结论 ,但所有实验证据都表明 ,在饥饿等环境胁迫因子作用下 ,非生长或缓慢生长的细胞可以产生突变 。 展开更多
关键词 适应性突变 遗传学特征 RecBCD重组途径 SOS反应 增变子 超突变
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Approximate Well Width and Optical Gain Formulas of 1 .555μm In_(1-x-y )Ga_y Al_x As Compressively Strained Quantum- Well Laser 被引量:2
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作者 张冶金 陈维友 +2 位作者 蒋恒 刘彩霞 刘式墉 《Journal of Semiconductors》 EI CAS CSCD 北大核心 2001年第1期11-17,共7页
Using Harrison's model and anisotropic parabolic approximation,the band structure of In1- x- y Gay Alx As compressively strained quantum wells is calculated.To design lasers with1.55μm wavelength,it is necessary... Using Harrison's model and anisotropic parabolic approximation,the band structure of In1- x- y Gay Alx As compressively strained quantum wells is calculated.To design lasers with1.55μm wavelength,it is necessary to an- alyze the well width,differential gain,transparency carrier density and the characteristic gain for an arbitrary com- position.Some useful empirical formulas are also presented. 展开更多
关键词 In1- x- y Gay Alx As QW linear gain differential gai
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A New System of Variational Inclusions with (H,η)-accretive Operators in Banach Spaces 被引量:3
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作者 LIU Ying CHEN Yong-li HE Zhen 《Chinese Quarterly Journal of Mathematics》 CSCD 北大核心 2008年第4期565-573,共9页
In this paper, we first introduce a new class of generalized accretive operators named (H,η)-accretive in Banach space. By studying the properties of (H,η)-accretive, we extend the concept of resolvent operators... In this paper, we first introduce a new class of generalized accretive operators named (H,η)-accretive in Banach space. By studying the properties of (H,η)-accretive, we extend the concept of resolvent operators associated with m-accretive operators to the new (H,η)-accretive operators. In terms of the new resolvent operator technique, we prove the existence and uniqueness of solutions for this new system of variational inclusions. We also construct a new algorithm for approximating the solution of this system and discuss the convergence of the sequence of iterates generated by the algorithm. 展开更多
关键词 q-uniformly smooth Banach space (H η)-accretive operator resolvent operator technique system of variational inclusion iterative algorithm
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Numerical Derivation of Strain Rate Effects on Material Properties of Masonry with Solid Clay Bricks 被引量:4
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作者 WEI Xueying HAO Hong 《Transactions of Tianjin University》 EI CAS 2006年第B09期147-151,共5页
In this paper, numerical method is used als. A typical unit of masonry is selected to serve merical model of RVE is established with detailed to study the strain rate effect on masonry materias a representative volume... In this paper, numerical method is used als. A typical unit of masonry is selected to serve merical model of RVE is established with detailed to study the strain rate effect on masonry materias a representative volume element (RVE). Nudistinctive modeling of brick and mortar with their respective dynamic material properties obtained from laboratory tests. The behavior of brick and mortar are characterized by a dynamic damage model that accounts for rate-sensitive and pressuredependent properties of masonry materials. Dynamic loads of different loading rates are applied to RVE. The equivalent homogenized uniaxial compressive strength, threshold strain and elastic modulus in three directions of the masonry are derived from the simulated responses of the RVE. The strain rate effect on the masonry material with clay brick and mortar, such as the dynamic increase factor (DIF) of the ultimate strength and elastic modulus as a function of strain rate are derived from the numerical results. 展开更多
关键词 masonry structure strain rate effects dynamic increase factor (DIF) elastic modulus ultimate strength
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Design of a transversal equalizer for electronic dispersion compensation in optical communication links 被引量:3
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作者 高振斌 石勇 +1 位作者 王博 曾祥烨 《Optoelectronics Letters》 EI 2011年第1期37-40,共4页
A programmable transversal equalizer for electronic dispersion compensation(EDC) in optical fiber communication systems is developed.Based on the SiGe technology with a cut-off frequency of 80 GHz,the equalizer consis... A programmable transversal equalizer for electronic dispersion compensation(EDC) in optical fiber communication systems is developed.Based on the SiGe technology with a cut-off frequency of 80 GHz,the equalizer consists of 6 seriesparallel amplifiers as delay units and 7 Gilbert variable gain amplifiers as taps,which ensure that the equalizer can work at the bit rate of 10 Gb/s.With different tap gains,the forward voltage gain of the transversal equalizer varies,which demonstrates that the equalizer has various filtering characteristics such as low pass filtering,band pass filtering,band reject filtering,and notch filtering,so it can effectively simulate the inverse transfer function of dispersive channels in optical communications,and can be used for compensating the inter-symbol interference and other nonlinear problems caused by dispersion.The equalizer(including pads) occupies an area of 0.40 mm × 1.08 mm,and its total power dissipation is 400 mW with 3.3 V power supply. 展开更多
关键词 Communication systems Dispersion compensation Electromagnetic dispersion Inverse problems Optical fibers Voltage regulators
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