Mammalian sleep

This review examines the biological background to the development of ideas on rapid eye movement sleep (REM sleep), so-called paradoxical sleep (PS), and its relation to dreaming. Aspects of the phenomenon which are discussed include physiological changes and their anatomical location, the effects of total and selective sleep deprivation in the human and animal, and REM sleep behavior disorder, the latter with its clinical manifestations in the human. Although dreaming also occurs in other sleep phases (non-REM or NREM sleep), in the human, there is a contingent relation between REM sleep and dreaming. Thus, REM is taken as a marker for dreaming and as REM is distributed ubiquitously throughout the mammalian class, it is suggested that other mammals also dream. It is suggested that the overall function of REM sleep/dreaming is more important than the content of the individual dream; its function is to place the dreamer protagonist/observer on the topographical world. This has importance for the developing infant who needs to develop a sense of self and separateness from the world which it requires to navigate and from which it is separated for long periods in sleep. Dreaming may also serve to maintain a sense of Iness or self in the adult, in whom a fragility of this faculty is revealed in neurological disorders.

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精密离心机结构误差对其运动精度的影响研究

目的研究精密离心机结构误差对其运动精度的影响。方法基于LMS Virtual.Lab Motion平台,开展精密离心机主轴回转系统静不平衡量、静压气体轴承铅垂度、转盘与静压气体轴承垂直度等结构误差对主轴半径误差和倾角误差的影响规律研究。结果获得了精密离心机结构误差对其运动精度的影响规律。结论随着主轴回转系统静不平衡量、铅垂度误差和垂直度误差的增大,主轴回转系统的半径误差和倾角误差均线性增加。     

Mammalian hairs in Early Cretaceous amber

Two mammalian hairs have been found in association with an empty puparium in a ∼100-million-year-old amber (Early Cretaceous) from France. Although hair is known to be an ancestral, ubiquitous feature in the crown Mammalia, the structure of Mesozoic hair has never been described. In contrast to fur and hair of some Jurassic and Cretaceous mammals preserved as carbonized filaments, the exceptional preservation of the fossils described here allows for the study of the cuticular structure. Results show the oldest direct evidence of hair with a modern scale pattern. This discovery implies that the morphology of hair cuticula may have remained unchanged throughout most of mammalian evolution. The association of these hairs with a possible fly puparium provides paleoecological information and indicates peculiar taphonomic conditions.     

2012年,扼住世界末日钟的指针

"世界末日"就像一个口碑很差的绯闻明星,总与不同年份惹上"绯闻".有人说它跟2000年有个约会,又有人把它和2012紧紧捆绑在了一起,但一个根本没观测到的行星会撞击地球的故事,怎么看都像是八卦狗仔的小道消息,笔者绝不相信毫无根据的故事能够带来末日.     

Circadian control of meal timing during temporal isolation

The Science of Nature -     

带轮毂直齿圆柱齿轮精锻的变形分析

此文对空心坯料精锻带轮毂直齿圆柱齿轮工艺进行了模拟实验,并以座标网格法着重对精锻终了阶段进行了变形分析,获得了金属流动规律,提出了对制订精锻工艺有参数价值的结论。     

Precision of the radiochemical OH measurement method

Twenty-eight radiochemical ¹⁴C tracer measurement of tropospheric hydroxyl radical (OH) concentrations were obtained at a rural site near Washington State University, Pullman, WA (117°W, 47°N). Diurnal OH concentration variations were observed for the five days between 9 August and 14 August 1990. These data made it possible to estimate the midday precision and detection limit of the radiochemical OH measurement method. Experiments performed at a peak O₃ photolysis rate J (O(¹D)) of (3.0±0.2) × 10⁻⁵ s⁻¹ yielded a mean midday OH concentration of (5.6±0.1 (1σ)) × 10⁶ cm⁻³. Other data put an upper bound of 16% on fluctuations of instrument sensitivity. Low-light or nighttime background OH concentrations were less than (2.6±2) × 10⁵ cm⁻³. A lower detection limit of 10⁵ cm⁻³ was obtained when extra care was taken with the low-level ¹⁴C counting procedure.     

直齿圆柱齿轮精锻技术的研究进展

综述了直齿圆柱齿轮精锻技术的特点和研究现状,并对其前沿问题和发展趋势进行了探讨.     

精确空投缓冲气囊材料研究

介绍了精确空投着陆缓冲的作用原理以及对气囊材料的要求,分析了聚酰胺、聚酯纤维2种气囊织物材料和氯丁橡胶、硅酮2种涂层材料的结构性能及发展,总结了当前主要的新材料技术,提出了着陆缓冲气囊材料的发展趋势.     

基于状态的维修——信息化环境下精确维修的利刃

分析了当前装备维修所面临的信息化战场环境,阐述了信息化环境下装备精确维修的必要性,介绍了维修的分类和基于状态的维修(CBM)概念,分析了CBM的特点,介绍了CBM的研究现状,阐述了CBM的技术可行性。在此基础上,进一步分析了信息化环境下基于CBM的装备精确维修流程。     

端盖精密成形的有限元模拟

采用有限元 (FEM)的方法对分流法精密成形端盖进行了计算机模拟 ,对坯料成形载荷 行程曲线、应力、模具的弹性变形等参量进行分析得出 :分流法是一个降低变形抗力和模具弹性变形 ,适于精密成形的有效的方法     

链条滚子精密成形新工艺

针对链条滚子成形存在的问题,提出了一种利用棒料以冷挤压成形为主,在连续模中进行多个工序连续成形的精密成形工艺方案,从而提高了材料的利用率和工厂的经济效益。     

精密离心机加速度测量不确定度模型研究

目的为精密离心机输出加速度的测量不确定度评定提供数学模型。方法基于三类较为常用的加速度载荷模型,考虑加速度各分量之间的相关性,分别建立三类加速度测量不确定度评定模型,并对三类模型的优劣进行分析和比较。结果利用所建立的加速度测量不确定度评定模型,对六台著名精密离心机输出的加速度测量不确定度指标进行了计算和校验,计算结果与部分精密离心机的给定指标一致,分析发现另一部分精密离心机的指标并不可信。结论针对精密离心机的技术指标和技术路线,可选择对应的加速度测量不确定度评定模型进行精密离心机输出加速度的测量不确定度评定。     

Internalisation of Enteric Viruses by Acanthamoeba castellanii, via Ingestion of Virus-Infected Mammalian Cells

The protozoan Acanthamoeba castellanii can inhabit various environments, including aquatic environments. After co-culture with mammalian cells which had been infected with coxsackievirus and rotavirus, virus was observed to have been internalised within the Acanthamoeba cells. No internalisation of freely-suspended virus was observed. The potential implications of virus internalisation of protozoa via infected mammalian cells, such as protection from disinfection, are discussed.