Highly specialized mammalian skulls from the Late Cretaceous of South America

Dryolestoids are an extinct mammalian group belonging to the lineage leading to modern marsupials and placentals. Dryolestoids are known by teeth and jaws from the Jurassic period of North America and Europe, but they thrived in South America up to the end of the Mesozoic era and survived to the beginnings of the Cenozoic. Isolated teeth and jaws from the latest Cretaceous of South America provide mounting evidence that, at least in western Gondwana, dryolestoids developed into strongly endemic groups by the Late Cretaceous. However, the lack of pre-Late Cretaceous dryolestoid remains made study of their origin and early diversification intractable. Here we describe the first mammalian remains from the early Late Cretaceous of South America, including two partial skulls and jaws of a derived dryolestoid showing dental and cranial features unknown among any other group of Mesozoic mammals, such as single-rooted molars preceded by double-rooted premolars, combined with a very long muzzle, exceedingly long canines and evidence of highly specialized masticatory musculature. On one hand, the new mammal shares derived features of dryolestoids with forms from the Jurassic of Laurasia, whereas on the other hand, it is very specialized and highlights the endemic, diverse dryolestoid fauna from the Cretaceous of South America. Our specimens include only the second mammalian skull known for the Cretaceous of Gondwana, bridging a previous 60-million-year gap in the fossil record, and document the whole cranial morphology of a dryolestoid, revealing an unsuspected morphological and ecological diversity for non-tribosphenic mammals.     

Numerical Value Results OF Guassian Beam Focussing

1Lens is placed in beam waist We consider the case of a Gaussian beam that is incident at its waist on a thin lens of focal length f.To find the location of the waist of the output beam and the beam radius at that point,we start with the ABCD law.     

Delayed ageing through damage protection by the Arf/p53 pathway

The tumour-suppressor pathway formed by the alternative reading frame protein of the Cdkn2a locus (Arf) and by p53 (also called Trp53) plays a central part in the detection and elimination of cellular damage, and this constitutes the basis of its potent cancer protection activity. Similar to cancer, ageing also results from the accumulation of damage and, therefore, we have reasoned that Arf/p53 could have anti-ageing activity by alleviating the load of age-associated damage. Here we show that genetically manipulated mice with increased, but otherwise normally regulated, levels of Arf and p53 present strong cancer resistance and have decreased levels of ageing-associated damage. These observations extend the protective role of Arf/p53 to ageing, revealing a previously unknown anti-ageing mechanism and providing a rationale for the co-evolution of cancer resistance and longevity.     

A PRICE DUOPOLY GAME MODEL WITH UNCERTAIN PARAMETERS

1 IntroductionIn the Bayesian game modeIs[1t2], the uncertainty of objectives is described with probability. But sometbe the uncertainty in practice i8 gben by some fuzzy parnders, and theobjectives of players mny not be to mallmize the expected payOffs[3'4'5j. [6,7l discussed themodeIs for endogenous Stackelberg and price leadership under complete infOmation. In [8,9],we studied the Cournot and Stackelberg models with fuzzy parameters. In this paPer, we givea new subjective equllibrinm fo…     

基于Android 手机言行记录系统的设计与实现

针对手机用户的个性化需求较高及传统方法的进程监控问题, 设计并实现了基于Android 开发平台的手机言行记录系统。该系统通过控制手机通讯录信息、文件加密操作、应用程序监控以及日志监控等方式实时监控分析手机用户的言行记录, 方便用户的自我监控与管理。该方法主要运用Intent 和日志监控实现软件监控功能,通过类FileEncrpter 对文件系统加密, 对录音加密则使用流加密, 运用MediaRecord 类和ACC(Advanced AudioCoding)编码实现音频录制。实验结果表明, 该系统达到了较为理想的实验效果, 证明了该系统的可行性。     

基于ARM的列车运行控制算法仿真测试系统

介绍了列车运行控制系统的基本组成和原理,采用通用ARM芯片S3C2440设计了列车运行控制仿真硬件系统以及包含列车模型的PC端仿真软件.使用串口UART实现下位机控制系统硬件和上位机列车仿真模型软件之间的数据通信.最后,设计了基于滑动模态状态观测器的列车控制算法,并在仿真测试系统中进行了测试.     

一种混合退化系统剩余寿命预测方法

针对传统的预测方法不能同时考虑线性和非线性退化问题,提出了一种基于维纳过程的带随机参数和确定参数的混合退化模型.基于首达时间(FHT)的概念给出了剩余寿命(RUL)的解析渐进显式形式,模型中随机参数通过Kalman滤波技术实时更新,确定参数采用极大似然估计进行估计.最后,采用陀螺仪实验数据验证了该方法的有效性.