The sand dredging and its impacts on riverbed evolution and tidal dynamic change in the lower reaches and delta of the Dongjiang River are examined in this paper. The large amount of sand, totally 3.32 billion m^3 fro...The sand dredging and its impacts on riverbed evolution and tidal dynamic change in the lower reaches and delta of the Dongjiang River are examined in this paper. The large amount of sand, totally 3.32 billion m^3 from 1980 to 2002, was mined from the riverbeds of the lower reaches and delta of the Dongjiang River. Increasing of the channel capacity, lowering of the average riverbed elevation, deepening of the water depth and decreasing of the longitudinal riverbed gradient are the main effects on the riverbed evolution brought by the large amount of sand dredging. Under the strong sand dredging and associated significant riverbed deformation, the notable changes of the tidal dynamic in the lower reaches and delta of the Dongjiang River occurred, including： （1）in the upper reaches of the Dongjiang River delta and lower reaches of the Dongjiang River, tidal level dropped apparently, tidal range widened, flood tidal duration became longer, amplitudes for major tidal components became bigger and tidal dynamics intensified; （2） tidal wave spread faster; and （3） the limits of the tidal level, tidal current and salt water moved upstream.展开更多
为揭示影响西藏凹乳芹叶绿体基因组中同义密码子使用偏好和使用模式的因素,本研究利用CUSP在线程序和Codon W 1.4.2、Microsoft Excel、SPSS 19等软件,计算并分析西藏凹乳芹叶绿体基因组53个蛋白质编码基因序列(coding sequences,CDS)...为揭示影响西藏凹乳芹叶绿体基因组中同义密码子使用偏好和使用模式的因素,本研究利用CUSP在线程序和Codon W 1.4.2、Microsoft Excel、SPSS 19等软件,计算并分析西藏凹乳芹叶绿体基因组53个蛋白质编码基因序列(coding sequences,CDS)的密码子使用偏性指标和碱基组成。结果表明,与G/C相比,同义密码子更偏好使用以A/U结尾的密码子。53条CDS的有效密码子数(effective number of codon,ENC)以及各项偏性指标分析均表明密码子偏好性较弱。GC_(1)和GC_(2)极显著相关,但两者与GC_(3)相关性均不显著,GC_(3)与ENC极显著相关,表明第3位碱基与第一、二位碱基的组成不同,同时GC_(3)会影响密码子的使用偏性。通过中性绘图、ENC-plot、PR2-plot、对应性分析发现自然选择可能在西藏凹乳芹叶绿体基因组同义密码子使用偏性中发挥重要作用,同时也受到突变压力、碱基组成等其他因素的影响;经过筛选得到4个最优密码子AGU、CGU、GGA和UUG。本研究结果为西藏凹乳芹的遗传修饰提供了理论基础,亦有助于丰富其遗传资源。展开更多
文摘The sand dredging and its impacts on riverbed evolution and tidal dynamic change in the lower reaches and delta of the Dongjiang River are examined in this paper. The large amount of sand, totally 3.32 billion m^3 from 1980 to 2002, was mined from the riverbeds of the lower reaches and delta of the Dongjiang River. Increasing of the channel capacity, lowering of the average riverbed elevation, deepening of the water depth and decreasing of the longitudinal riverbed gradient are the main effects on the riverbed evolution brought by the large amount of sand dredging. Under the strong sand dredging and associated significant riverbed deformation, the notable changes of the tidal dynamic in the lower reaches and delta of the Dongjiang River occurred, including： （1）in the upper reaches of the Dongjiang River delta and lower reaches of the Dongjiang River, tidal level dropped apparently, tidal range widened, flood tidal duration became longer, amplitudes for major tidal components became bigger and tidal dynamics intensified; （2） tidal wave spread faster; and （3） the limits of the tidal level, tidal current and salt water moved upstream.
文摘为揭示影响西藏凹乳芹叶绿体基因组中同义密码子使用偏好和使用模式的因素,本研究利用CUSP在线程序和Codon W 1.4.2、Microsoft Excel、SPSS 19等软件,计算并分析西藏凹乳芹叶绿体基因组53个蛋白质编码基因序列(coding sequences,CDS)的密码子使用偏性指标和碱基组成。结果表明,与G/C相比,同义密码子更偏好使用以A/U结尾的密码子。53条CDS的有效密码子数(effective number of codon,ENC)以及各项偏性指标分析均表明密码子偏好性较弱。GC_(1)和GC_(2)极显著相关,但两者与GC_(3)相关性均不显著,GC_(3)与ENC极显著相关,表明第3位碱基与第一、二位碱基的组成不同,同时GC_(3)会影响密码子的使用偏性。通过中性绘图、ENC-plot、PR2-plot、对应性分析发现自然选择可能在西藏凹乳芹叶绿体基因组同义密码子使用偏性中发挥重要作用,同时也受到突变压力、碱基组成等其他因素的影响;经过筛选得到4个最优密码子AGU、CGU、GGA和UUG。本研究结果为西藏凹乳芹的遗传修饰提供了理论基础,亦有助于丰富其遗传资源。
