Dinosaurian growth patterns and rapid avian growth rates

Did dinosaurs grow in a manner similar to extant reptiles, mammals or birds, or were they unique? Are rapid avian growth rates an innovation unique to birds, or were they inherited from dinosaurian precursors? We quantified growth rates for a group of dinosaurs spanning the phylogenetic and size diversity for the clade and used regression analysis to characterize the results. Here we show that dinosaurs exhibited sigmoidal growth curves similar to those of other vertebrates, but had unique growth rates with respect to body mass. All dinosaurs grew at accelerated rates relative to the primitive condition seen in extant reptiles. Small dinosaurs grew at moderately rapid rates, similar to those of marsupials, but large species attained rates comparable to those of eutherian mammals and precocial birds. Growth in giant sauropods was similar to that of whales of comparable size. Non-avian dinosaurs did not attain rates like those of altricial birds. Avian growth rates were attained in a stepwise fashion after birds diverged from theropod ancestors in the Jurassic period.     

Rapid growth and sterility of growth hormone gene transgenic triploid carp

Triploid carp (100%) with 150 (3n=150) chromosomes were obtained by crossing the females of improved tetraploid hybrids (♀, 4n=200) of red crucian carp (♀)×common carp (♂) with the males of diploid yellow river carp (♂, 2n=100). The crosses yielded transgenic triploid carp (positive triploid fish, 44.2% of the progeny) and non-transgenic triploid carp (negative triploid fish). Histological examination of the gonads of 24-month-old positive triploid fish suggested they were sterile and the fish were not able to produce mature gametes during the breeding season. Morphologically, both the positive and negative triploid fish were similar. They had a spindle-shaped, laterally compressed, steel grey body with two pairs of barbells. Most of the quantifiable traits of the triploid carp were intermediate between those of the two parents. The positive and negative triploid fish were raised in the same pond for 2 years. The mean body weight of the positive triploid fish was 2.3 times higher than the negative triploid fish. The weight of the largest positive triploid fish was 2.91 times higher than that of the largest negative triploid fish. Thus, we produced fast-growing transgenic triploid carp that have a reduced ecological risk because of their inability to mate and produce progeny.     

环境污染、内生人口增长与经济增长模型

通过把环境污染与生产总量联系起来,由消费物质多少及环境好坏、人口增长率大小这三个因素来确定效用,建立一个环境内生人口增长的经济增长模型,并按照微分方程的稳定性理论对模型进行了均衡分析和动态分析．     

TiO2纳米管阵列的可控生长及其生长机理探讨

目的研究TiO2纳米管阵列的可控生长最佳条件及其生长机理。方法采用阳极氧化法在Ti箔上生长有序排列的TiO2纳米管阵列,用场发射扫描电镜(日立S-4800型)分析其表面与界面形貌,通过电流-时间曲线分析TiO2纳米管的生长规律。结果通过实验结果可知,纳米管的可控生长模式为阻挡层变厚并趋于稳定;而纳米管的生长机理可以理解为化学溶解与电化学刻蚀与溶解的相互竞争并达到平衡,同时纳米管的生长受电压、温度、搅拌速度的影响,阳极电压不仅控制了纳米管的生长速度,还决定着纳米管的生长模式;纳米管生长速度随温度的升高而增大,随搅拌速度的增大而减小。结论通过分析纳米管的生长过程中电流变化与表面形貌,得出了纳米管的可控生长模式和纳米管的生长规律。     

Douglas-fir树木生长模型分析及建模

主要对一棵24岁的Douglas-fir(花旗松，北美西北部的主要树种之一)的生长情况进行详细的测量和描述，其目的是创建出一个准确的计算机三维模型．同样的研究由Mark Goebel在2002年对同一试验地砍伐的另一棵Douglas-fir的地下部分作过．把两次研究的结果结合起来制作出一个可以用于教学演示的Douglas-fir生长模型．使用G．H.Dufr和Noran J.Nolan首创的分析法对测量结果进行了分析．主千年轮的直径生长，主干平均年轮面积，主干垂直生长，枝干长度增长和年平均枝干直径的数值都进行了构图分析．生长曲线同理想生长曲线表现出了一定的差异，同时显示了各年问的细微变化．过去24年间好的生长年份可以因此被确定出来．测量分析结果和Goebel的研究结果相吻合，因此重建一棵Douglas-fir的目的能够被实现．但是研究结果表示我们砍伐的Douglas-fir并不是完全没有受到生长压力的绝对优势物种，要进一步创建三维模型还需要一些计算才能实现．     

Dynamic instability of microtubule growth

We report here that microtubules in vitro coexist in growing and shrinking populations which interconvert rather infrequently. This dynamic instability is a general property of microtubules and may be fundamental in explaining cellular microtubule organization.