The origin of the internal nostril of tetrapods

The choana, a unique 'internal nostril' opening from the nasal sac into the roof of the mouth, is a key part of the tetrapod (land vertebrate) respiratory system. It was the first component of the tetrapod body plan to evolve, well before the origin of limbs, and is therefore crucial to our understanding of the beginning of the fish-tetrapod transition. However, there is no consensus on the origin of the choana despite decades of heated debate; some have claimed that it represents a palatally displaced external nostril, but others have argued that this is implausible because it implies breaking and rejoining the maxillary-premaxillary dental arcade and the maxillary branch of nerve V. The fossil record has not resolved the dispute, because the choana is fully developed in known tetrapod stem-group members. Here we present new material of Kenichthys, a 395-million-year-old fossil fish from China, that provides direct evidence for the origin of the choana and establishes its homology: it is indeed a displaced posterior external nostril that, during a brief transitional stage illustrated by Kenichthys, separated the maxilla from the premaxilla.     

岁岁年年人不同——《长亭》与《金锁记》之比较

苏伟贞是公认的受张爱玲影响很深的作家。1986年,苏伟贞发表《长亭》,其中的人物让读者很容易联想起张爱玲的《金锁记》。本文就是从人物形象分析的角度来解读《长亭》对《金锁记》的继承与发展。     

配电脑前学会读懂电脑硬件性能参数

通过学习一定的计算机的硬件知识,学会读懂计算机各硬件主要性能参数,让人们在购买电脑时能够选择适合自己需求的电脑,不必花冤枉钱,而且实用。     

The end of world population growth

There has been enormous concern about the consequences of human population growth for the environment and for social and economic development. But this growth is likely to come to an end in the foreseeable future. Improving on earlier methods of probabilistic forecasting, here we show that there is around an 85 per cent chance that the world's population will stop growing before the end of the century. There is a 60 per cent probability that the world's population will not exceed 10 billion people before 2100, and around a 15 per cent probability that the world's population at the end of the century will be lower than it is today. For different regions, the date and size of the peak population will vary considerably.     

世界植树节邮票赏析

以收集到的79枚世界植树节邮票为线索，随着季节推移，概述世界植树节邮票。世界植树节邮票不仅直接反映不同地域、不同国家的地理风貌，也生动反映不同民族、不同国家的植树政策与植树文化。每一个有担当的政府都从社会动员、文化宣传、科学研究、经济杠杆、法律法规等方面倡导“绿水青山就是金山银山”，全力推动植树造林运动。     

哈贝马斯生活世界理论的价值

哈贝马斯在其代表作《交往行动理论》中对“生活世界”进行了探讨，他的生活世界理论为其交往行动理论提供了基础性支撑，提出了很有价值的“体系--生活世界”双重社会分析结构，开拓了马克思主义的内部论题，体现了极强的理论延展能力，是很有价值的现代哲学方案。     

The spin and orbital moment contributions of each element to macroscopic magnetization in Co0.9Fe0.1 films

With the development of information technology, the data storage capacity of magnetic recording media has been increasing rapidly in recent years. To achieve areal densities as high as one terabit per square inch (Tb·in?2), roughly 20 times of today’s p…     

法眼、新闻眼各归其眼——评公共事件下法律与新闻的博弈

从评判的角度而言,法眼和新闻眼对待公共典型事件的价值和立场是不一样的,自然而然,二者得出的结论也不尽相同。究其因,是法眼与新闻眼二者本质属性的区别所致。文章通过分析2009年著名的两大公共事件中的法眼、新闻眼,推导出这样的结论：法眼的基本属性是理性、保守和价值一元化的,而新闻眼则更倾向于感性、前卫和价值多元化。正是由于本质的不同,对于公共典型事件,法眼、新闻眼二者无须融合为一体,应各司其职,各归其眼。     

提高草木灰中各元素的有效性研究

考察了煅烧温度、煅烧时间对草木灰中各元素的有效性影响.实验结果表明:草木灰经700℃煅烧1.0h,所含的硅能够大量转化为可溶性硅,其他元素可溶性物质无明显改变,故可作为硅肥的补充剂使用;以盐酸为浸提剂实验效果最好;浸提温度对实验结果影响不明显.